m H Z m S 8 3 ?E | r C m o a> o v * n 5 m 2 O 2 m m x A m c 2 00 00 1 o H m n 0) r i D < m 3) I O (0 2 35 < -1 < 0) m GIFT OF COMPEND OF MECHANICAL REFRIGERATION A COMPREHENSIVE DIGEST OF APPLIED ENERGETICS AND THERMODYNAMICS FOR THE PRACTICAL USE O7 Ice Manufacturers, Cold Storage Men, Contractors, Engineers, Brewers, Packers and Others Interested in the Application of Refrigeration. SIXTH EDITION By J. E. SI E BEL DIRECTOR ZYMOTECHNIC INSTITUTE, CHICAGO CHICAGO NICKERSON & COLLINS CO. 1904 Entered according to Act of Congress by H. S. RICH & CO. In the office of the Librarian of Congress at Washington, D C 1895, 1895, 1899, 1902 and 1903. Copyright, 1904, by NICKERSON & COLLINS CO. All rights of translation reserved. PRESS OF ICE AND REFRIGERATION CHICAGO PREFACE While in the third, fourth, fifth and sixth editions of the Compend the general arrangements of matter and the man- ner of treatment remain the same as in the first and second editions, it is nevertheless an entirely new book. Not only that the contents of the sixth edition cover nearly one hun- dred and fifty pages more than they did in the first edition, but also much of the former matter has been entirely rewrit- ten and nearly every topic has received valuable additions. This will be especially noticed in the practical chapters on the "Compressor and Its Attachments," "Ice and Distilled Water Making," "Cold Storage," "Piping of Rooms, " "Insu- lation and Heat Leakage," "Brewery Refrigeration," "Ab- sorption Machine," "Management and Testing of Machines,*' etc. On "Liquefied Air, Its Production and Uses," and on "The Carbonic Acid Machine" entirely new chapters have been added. The cold storage temperature tables and storage rates have again been thoroughly revised, and many import- ant tables and many practical examples on various topics have been added to the book ; and although it now covers over four hundred pages, it nevertheless retains its convenient shape, equally well adapted for pocket and table use. Special attention has been given to the preparation of the tablo of contents, and more particularly to the. topical index, which contains some fifteen hundred references, so that whatever has been said in the book on any subject can be readily found under any possible appellation. Again, the hints and suggestions kindly offere:! by the engineering fraternity have been duly utilized in the present edition. Still many imperfections must necessarily remain, and for this reason the author solicits such further commun- ications and criticism as may tend to render the work of the greatest possible utility to the profession. 501806 PREFACE TO FIRST EDITION. THE object for which this book has been compiled is a two-fold one. In the first place it is intended to pre- sent in a convenient form those rules, tables and formulae which are frequently needed by the refrigerating en- gineer. In the second place it is an attempt to present the subject in a simple yet systematic manner, so as to enable the beginner to acquire a more or less thorough insight into the matter and to understand the technical terms used in publications on the subject. This course has been suggested or rather prompted by constant inquiries addressed to the publishers, and in order to best subserve this purpose the different para- graphs and chapters have been framed in such a man- ner, that while each paragraph may be consulted for the individual information which it contains, the whole forms a continuous chain of reading matter calculated to digest the entire subject of Energetics and Thermodynam- ics and their application to mechanical refrigeration. Instead of making the futile attempt to describe the decorative details of the endless varieties of machines and appliances, the author has aimed to*discuss the vari- ous methods of refrigeration and applications thereof for different purposes in such a manner as to enable every engineer, operator and owner of a plant to thoroughly understand all the vital points in the working of his machinery and in the handling of goods for cold storage, in the making of ice, in the refrigeration of breweries, packing houses, etc. In this way it is thought that the familiar questions as to temperatures, say of brine and storage rooms, as to what a machine is able to do under given conditions, 01 PREFACE. what it might be made to do under others, as to the proper dimensions of different parts, and most other problems relating to the operation of refrigerating works, can be readily answered by turning to a paragraph or a table, and in cases of greater accuracy by doing some plain figuring. The different amounts of space allotted to the differ- ent systems of refrigeration must not be construed into argument for or against the merits of one or the other system. The author is not interested in any one system in particular, and if his intention to be strictly impartial is not actually carried out in every respect, his judgment rather than his impartiality should be impeached. As regards the mathematical treatment of the sub- ject, it had to be strictly elementary and without the use of diagrams to subserve the desired purpose of a book for ready reference. In presenting the subject on this basis it has been the special object of the author to have the formulae as plain and simple as they could be made with- out making an undue sacrifice in regard to accuracy. This is especially the case with all the formulae relating to ammonia refrigeration, which subject, like some others, has been treated altogether on the basis of articles pub- lished by the author in Ice and Refrigeration. In order to further enhance the usefulness of the book, and in forced recognition of the fact that many practical machinists have an aversion to even the sim- plest kind of a formula, a separate appendix has been devoted to the numerical solution of a number of varied examples, which it is thought will suffice to demonstrate that the formulae in these chapters can be handled by any one versed in the simplest forms of common figuring. Independent of the strictly practical issues, and .in pursuance of the stated objects of the Compend, it has been sought to give so much of an elementary discussion of the terms and definitions of the science" of energetics and of thermodynamics in particular, that its perusal will suffice to understandingly master the technical terms in PREFACE. treatises on refrigeration and kindred topics in Ice and Refrigeration and other publications. In this attempt those definitions and concepts which are of more recent coinage and which have not as yet been generally accepted in text books, have for this reason received rather more attention in these pages than their direct relation to the main subject would seem to call for at first sight. To those who possess the required practical and the- oretical knowledge, the book will doubtless prove a wel- come companion, as it contains in a very convenient form a prolific array of useful and indispensable tables, and a number of rules which are not usually committed to memory. Aside from the works quoted in Appendix III. the author is indebted to many of the ice machine building fraternity for much of the information here presented, and he may also be allowed to mention in this direction the valuable contributions to Ice and Refrigeration by Wood, Denton, Jacobs, Linde, Sorge, Starr, Richmond, St. Clair, Post, Rossi, Kilbourn, Burns and others. There naturally must be many imperfections and shortcomings connected with an attempt like this, and special pains have been taken to draw attention to them in the body of the book, and any further suggestions or hints in this direction by those using the same will be thankfully received by its author with a view to further improve and perfect the contents of this publication. TABLE OF CONTENTS. * PART I. GENERAL ENERGETICS. CHAPTER I. MATTER. MATTER General Properties of Matter, Constitution, Atoms, Molecules, Solid, Liquid, Gaseous Matter 5 Body, Mass. Unit of Mass, Mass and.Weight.iMeasurement of Space, Density, Specific Weights..' 6 Fundamental Units, Derived Units, C. G. S. Units 6 CHAPTER II. MOTION, FORCE. MOTION. Force, Measurement of Force, Dyne, Gravitation, Molecular Forces, Cohesion (table) ..: 7 Adhesion, Chemical Afflnity.Work, Unit of Work, Foot-Pound, Time, Power, Horse-Power, Velocity, Momentum 8 Inertia, Laws of Motion, Statics, Dynamics or Kinetics 9 CHAPTER III. ENERGY. ENERGY. Visible Energy, Kinetic Energy,Potential Energy, Molecular Energy 9 C. G. S. Unit of Energy, the Erg, the Dyne Centimeter, Con- servation of Energy, Transformation of Energy 10 Physics, Subdivision of Physics, Dissipation of Energy, Energy of a Moving Body, Mechanisms 10 CHAPTER IV -HEAT. HEAT. Sources of Heat, Ether, RadiantjHeat and Light 11 Temperature, Thermometer, Thermometer Scales 12 Comparison of Thermometer Scales (table)..- 13 Measuring High Temperatures U Absolute Zero, Unit of Heat 14 C. G. S. Unit of Heat, Capacity for Heat, Specific Heat 15 Tables on Specific Heat of Solids, Liquids and Water at Dif- ferent Temperatures ...r .1&-16 Use of Specific Heat, Determination of Specific Heat, Tem- perature of Mixtures 16 Expansion by Heat of Solids ( table ), of Liquids. ... 17 Expansion of Water and Liquids (tables), Transfer of Heat. . 18 Insulators (table) 19 Conduction of Heat, Conductivity of Metals, Radiation of Heat, Theory of Heat Transfers, Absorption of Heat 20 Convection of Heat, Complicated Transfer, Convection 23 Comparative Absorption and Radiation (table ) 23 Condensation of Steam in Pipes, Heat Emitted (tables). ..24-26-26 Non-conductive Coating for Steam Pipes (tables) 23-24 Cooling of Water in Pipes (tables) 24-25 Transmission of Heat through Plates from Water to Water and Steam to Water (tables) 27-28 Condensation in Pipes Surrounded by Water, Transmission of Heat through Pipes ( tables) 29-30 Latent Heat, Latent Heat of Fusion (tables), Effect of Pres- sure on Melting Point, Latent Heat of Solution 31 Frigoriflc Mixtures (table )'. 32 ii TABLE OP CONTENTS, HEAT BY CHEMICAL COMBINATION. Elementary Bodies, Chemical Atoms, Molecules.. 33-34 Chemical Symbols, Atomicity, Tables of Properties of Ele- ments, Generation of Heat.. . ,..'. ....33-34 Measure of Affinity, Total Heat Developed, Maximum Prin- ciple, Expressions for Heat Developed, Heat of Combina- tion with Oxygen (table) 86 COMBUSTION. Air Required in Combustion, Gaseous Prod- ucts.. 36-37 Heat Generated, Coal, Coke, Lignite ? . 38 Chimney and Grate ' * 39 Heat by Mechanical Means '. 39 CHAPTER V.-FLUIDS, GASES, VAPORS. FLUIDS IN GENERAL. Viscosity, Pascal's Law, Buoyancy of Liquids, Archimedean Principle, Specific Gravity De- termination, Hydrometers 40 Comparison of Hydrometers, Specific Gravity, Twaddle, Baume" and Beck (tables), Pressure of Liquids AI Water Pressure, Surface Tension of Liquids, Velocity of Flow 42 Flow of Water in Pipes, Flow through Pipes, Head of Water, . Water Power, Hydrostatics and Dynamics . 43 CONSTITUTION OF GASES. Pressure and Temperature, Boyle's .Law, Mariotte's Law, St. Charles Law, Unit of Pressure, Absolute and Gauge Pressure '.-.; 44 Comparison of British and Metrical Barometer, Action of Vacuum, Mano-Meters, Gauges, Weight of Gases..:, 45 Mixture of Gases, Dalton's Law, Buoyancy of Gases Lique- faction of Gases, Heat of. Compression, Critical Tempera- ture, Critical Pressure, Critical Volume _ 45 Table of Critical Data, Specific Heat of Gases (table) 47 Isothermal Changes, Adiabatic 'Changes, Free Expansion Latent Heat of Expansion, Volume and Pressure 48 Perfect Gas, Absolute Zero Again, Velocity of Sound, Friction of Gas in Pipes, Absorption of Gases 49-50 VAPORS. Saturated Vapor, Dry or Superheated Vapor Wet Vapor, Tension of Vapors ; . 50 Vaporization, Ebullition, Boiling Point, Variation of Boiling Points, Retardation of Boiling, Latent Heat of Vaporiza- tion * 51 Refrigerating Effects, Liquefaction of Vapors, Distilling, Condensation,. Compression, Dalton's Law for Vapors, Vapors from Mixed Liquids, Sublimation, Dissociation .... 52 .CHAPTER VI. MOLECULAR DYNAMICS. MOLECULAR KINETICS.-Rectilinear Motion of Molecules, Temperature of Gases, Pressure of Gases, Avogrado's Velocity of Molecules in Gases, Internal Friction, Total Heat Energy of Molecules 64 Law of Gay Lussac, Expansion of Gases, Volume and Tem- perature.. . , , 55 EQUATION FOR GASEOUS BODIES Equation for Perfect Gases, Connecting Volume, Pressure and Temperature... . 55 Van der Waal's Universal Equation for Gases 56 Critical Condition of Gases, Critical Data 56-57 Application of Universal Equation, Molecular Dimensions... 58-59 Absolute Boiling Point, Capillary Attraction, Gas and Vapor, Liquefaction of Gases 60 CHAPTER VII. THERMODYNAMICS. THERMODYNAMICS. First Law of Thermodynamics, Sec- 9nd Law of Thermodynamics, Equivalent Units, Mechan- ical Equivalent of Heat (J), Second Law Qualified 61 TABLE OF CONTENTS. in Conversion of Heat into Work, Continuous Conversion, Work- ing Substance. Working Medium, Molecular Transforma- tion of Heat into Work, Work Done by Gas Expanding . against Resistance, Vacuum, Heat Energy of Gas Mixtures 62 Dissipation of Energy, Adiabatic Changes, Adiabatic Com- pression, Adiabatic Expansion, Reversible Changes or Conversions, Isothermal Changes, Isothermal Compression 63 Maximum Conversion, Continuous Conversion, Passage of Heat, Its Ability to Do Work (Proportional to Differences in Temperature) : . 64 Requirements for Continuous Conversion, Working Medium, Boiler or Generator, Refrigerator or Condenser, Compen- sation for Lifting Heat . 64-65 Components of Heat Changes, Internal and External Work, . Maximum Continuous Conversion of Heat 65 CYCLE OF OPERATIONS. Reversible Cycle, Ideal Cycle.... 66 Ideal Cycles Have the Same and the Maximum Efficiency 66 Influence of Working Fluid, Rate of Convertibility of Heat, Carnot's Cycle, 67 Synopsis of Proof of Second Law . 67-68 Efficiency of Ideal Cycle, Description of Garnet's Cycle 68-69 Heat Engines, Available Effect of Heat 70 Consequences of Second Law, Absolute Zero of Temperature.70-7t Ideal Refrigerating Machine, Efficiency and Fall of Heat.... 71-72 COMPENSATED TRANSFER OF HE AT. Uncompensated Transfer, Entropy, Latent and Free Energy . . : 72 Future Condition of Universe, Changes of Entropy 73 Increase of Entropy, Origin of Heat Energy 74 SPECIFIC HEAT OF GASES. -At Constant Volume, at Con- stant Pressure, Components of Specific Heat of Gases.. 75-76 AIR THERMOMETER. Thermodynamic Scale . 7tt Heat, Weight, Entropy, Thermodynamic Function, Carnot's Function, the Constant of the Gas Equation (S) 77 Isentropic Changes, Latent Heat and Entropy 77 CHAPTER VIII. MODERN ENERGETICS. NATURE OF MASS. System of Energetics, New Definition of Energy, Classification of Energy, Mechanical Energy, Heat, Electric and Magnetic Energy, Chemical or Internal Energy, Radiated Energy 78 Mechanical Energy, Kinetic Energy, Energy of Space, Energy of Distance ( force ), Energy of Surface, Energy of Volume . 78 Factors of Energy, Intensity Factor, Capacity Factor, Applied to Various Forces of Energy, Dimensions of Energy 79 The Intensity Principle, Compensation of Intensities, Differ- ences of Intensities, Regulative Principle of Energy, Maxi- mum Amount of Transformation, State of Equilibrium.. 80 Artificial and Natural'.Transf ers, Artificial Equilibrium, Dissi- pation of Energy, Radiant Energy 81 Transformation of Energy, Reversible Changes, Irreversible Changes, Perpetual Motion of First and Second Order, Con- servative System 83 Continuous Conversion of Energy, Maximum Convertibility, Intensity of Principle, Criterion of Changes 83 Justification of Modern Concepts, Uniform Units of Energy, Change of Absolute Zero , 84 PART II. PRACTICAL APPLICATION. - CHAPTER I. REFRIGERATION IN GENERAL. MEANS FOR PRODUCING REFRIGERATION. Classifica- tion of Methods, Air Machines, Windhausen Machine 85 IV TABLE OF CONTENTS, Freezing Mixtures, Ice Machines, Construction of Machines, Vaporization, Vacuum and Absorption Machines 86 Continuous Absorption Machine, the Compression Machine Cycle of Operation 87 AMMONIA MACHINES, Qualifications of Ammonia for Refrigerating Purposes, Perfect Compression System, the Reversible Cycle of Operations, Work to Lift Heat 88 Formula Expressing Work, Defect in Cycle, Choice of Circu- lating Medium, Discussion of Essential Qualities of Differ- ent Refrigerating Liquids ( table) ...;...., 89 Comparison of Ammonia, Sulphurous Acid and Carbonic Acid for Refrigeration, Size of Ice Making Machines, Ex- pressions for Capacity, Refrigerating and Ice Making Capacity, Various Uses of Refrigeration 89-90 CHAPTER II. PROPERTIES OF AMMONIA. FORMS OF AMMONIA. Anhydrous Ammonia, Composition and Decomposition of Same, Compressibility and Com- bustibility, .Non-Explosiveness of Ammonia 91 Handling of Drums Containing Ammonia, Suffocating Proper- ties of Same, Pressure and Temperature of Saturated Ammonia, Vapor Density of Ammonia and Volume of Vapor, Specific Heat -of Liquid and of Vapor (Negative Specific Heat) .. .??.. .............. 92 Specific Volume of Liquid Ammonia, Latent Heat of Evapora- tion, External Heat, Weight of Ammonia Liquid and Vapor. 93 Woo&a Table for Properties of Saturated Ammonia Vapor. T . . '94 Van der Waql's Formula Applied to Ammonia, Values for Pressure of Saturated Ammonia by this Formula 96 Superheated Ammonia Vapor, Formulae for Superheated Vapor, Relation of Volume, Temperature and Pressure.. 96-97 AMMONIA LIQUOR. Strengths of Solution of Ammonia (table), Showing Specific Graviiy and Degrees Baume 97 Siaar'* Table, Showing Relations between 'Pressure and Tem- perature of Ammonia Solutions of Different Strengths.. 98-99 Explanation of Baum6 Scales or Hydrometers, Saturated ' Solution of Ammonia, Tables Showing Percentage of Am- monia in Saturated Solution at Different Temperatures. 100-101 Heat Generated by the Absorption of Ammonia, Formula for Calculating the Same .101-102 Sim's Table, Showing the Solubility of Ammonia in Water at Different Pressures and Temperatures 102 Tests for Ammonia, Boiling Point Test, Nessler's Reagent, Different Systems of Ammonia Refrigeration 103-104 CHAPTER III. WATER, STEAM, ETC. PROPERTIES OF WATER. Composition, Formation of Ice, Freezing Point Depressed by Pressure. Properties of Ice, Steam, volume of Steam, Pressure of Saturated Steam. .. 105 Total Heat in Steam, Latent Heat of Vaporization, Externaf Latent Heat, Internal Latent Heat, Specific Heat of Water and of Steam, Negative Specific .Heat of Steam, Specific Heat of Ice, Specific Volume of Steam 106-107 Table Showing Properties of Saturated Steam 107 Volume and Weight of Water at Different Temperatures 108 PRODUCTION OF STEAM. Work Done by Steam, Heating Area of Boiler, Priming 108 Amount of Priming, Flow of Steam through Pipes 109 HYGROMETRY. Air Saturated with Moisture, Hygrometric State of Atmosphere, Absolute Moisture, Dew Point, Determination of Moisture, Wet and Dry Bulb Thermo- meter.. 110 Maximum Tension of Aqueous Vapor, Table Showing Tension of Vapor, Drying Air, Vaporization of Water into Air.. 111-113 Purity of Water... 113 TABLE OF CONTENTS. V CHAPTER IV. THE AMMONIA COMPRESSION SYSTEM. GENERAL FEATURES. The System a Cycle, the Compressor. 114 Refrigerating Effect of the Circulating Medium in General and of Ammonia in Particular 115 Work of Compressor per Pound of Ammonia Circulated 115. Heat to be Removed in the Condenser, Amount of Superheat- ing, Counteracting Superheating, Amount of Ammonia Required to Prevent Superheating 116 Net Theoretical Refrigerating Effect of One Pound of Am- monia, Volume of Compressor, Cubic Capacity of Com- pressor (per Minute), Clearance of Compressor 117 Formula for Clearance, Refrigerating Capacity of Compressor in Tons of Refrigeration and in Thermal Units 118 Ammonia Passing the Compressor, Net Refrigerating Ca- pacity 119 Horse Power of Compressor, Size of Compressor for a Given Refrigerating Duty. 119 Reduced Refrigerating Duty, Revolutions and Piston Area. . . . 120 Useful and Lost Work of Compressor, Determination of Lost Work, Indirect Determination of Actual Work. 120-121 Horse Power of Compressor Engine, Water Evaporated in Boiler, Coal Required . 121-122 Efficiency of Compressor : 122 DIFFERENT KINDS OF COMPRESSORS.-The Linde Com- pressor 123 The De La Vergne Compressor, the Water Jacket Compressor 124 Tables Showing the Relation between the Volume of Ammonia Gas Passing the System and the Theoretical Refrigeration under Different Back and Condenser Pressures 124-125 The St. Glair Compound Compressor, Amount of Water for Counteracting Superheating 125 The By-Pass, the Oil Trap 126 THE CONDENSER. Submerged Condenser, Amount of Con^ denser. Surf ace, Empirical Rules and Formulae 126-127 Amount of Cooling Water, Rule and Empirical Formulae, Economizing Cooling Water .... . . . !28 Device for Economizing Cooling Water, Using Same for Boiler Feeding, Open Air Condenser, Pipe Required for Same 129 Empirical Rule for Piping, Water Required, Condenser Pressure, Liquid Receiver 130 Dimensions of Condenser, Forecooler, Purge Valve, Duplex Oil Trap, Wet and Dry Compression 131-133 Expansion Valve, Expansion of Ammonia, Direct and Indirect Expansion, Size or Expansion Coils, Piping Rooms, Usual Pipe Sizes, Circumstance Governing Amount of Pipe.. .134-135 Transmission of Heat or Refrigeration through Pipes, Discus- sion of the Problems Involved, Practical Rules for Piping. 135 Scope of Rules for Piping, Comparative Dimensions of Pipe.. 136 Brine System, Size and Amount of Pipes in Brine Tank, Pipe for Brine Circulation, General Empirical Rule, Rule for Laying Pipes, Table for Equalizing Pipes 137-138 Table Showing Capacity of Single-Acting Pumps 139 The Brine Pump, Preparation of Brine, Table Showing Prop- erties of Solutions of Salt, Strength of Brine 140 Rules for Calculating Strength of Brine, Points Governing Strength of prine 7 141 Salometer and Substitutes for Same, Table Showing Specific Gravity of Salt Solutions and Corresponding Hydrometer Degrees, Chloride of Calcium for Brine Preparation Table Showing Properties of Chloride of Calcium in Solution... 142 Brine Circulation vs. Direct Expansion, the Dryer, Liquid Trap. .142-14? vi . TABLE OF CONTENTS. CHAPTER V. ICE MAKING AND STORING. SYSTEMS OF ICE MAKING. Can and Plate System, Ice Making Capacity of Plant, Size of Cans in Can System, Temperature for Freezing ... 144 Dimensions of Ice Making Tanks (table) 145 Time for Freezing, Amount of Pipe in Freezing Tank 146 Arrangement of Brine Tank, Size of Brine Tank 147 The Brine Agitator, Harvesting Can Ice, Hot Well 148 Comparison of Plate and Can System, Size of Plates, Time for Freezing, Harvesting Plate Ice, Storage of Artificial Ice.. 149 Ice for Storage, Construction of Storage Houses for Ice, Ante- Room in Ice Storage House, Equivalent of Ton of Ice in Cubic Feet, Refrigerating Ice Houses, Rule for Same ...... 150 Packing Ice, Withdrawal and Shipping Ice, Selling of Ice.. 151-152 Weight and Volume of Ice, Cost of Ice, Coal for Making Ice 1 153-155 Skating Rinks, Quality of Ice ; 156 WATER FOR MAKING ICE. Requirements of Same,. Clear Ice, Boiling and Filtration of Water 157 Distilled Water, Cooling Water Required in Distillation, Size of Condenser, Discussion of Rules on Amount of Con- densing Surf ace, Filtration of Water . 158 Reboiling and Filtering Distilled Water, Cooling the Distilled Water, Storage Tank 159 Intermediate Filter, Dimensions of Distilling Plant, Dimen- sions of a Ten-ton Distilling Plant, Dimensions of a Thirty-ton Distilling Plant 160 Skimmer, Brine Circulation, Arrangem ent of Plant 161 Defects of Ice, White or Milky Ice, White Core. Red Core, Taste and Flavor of Ice, Use of Boneblack and Fil- tration 162-164 Number of Filters, Rotten Ice, Purity of Water Test 165-166 Devices for Making Clear Ice, the Cell System, Remuner- ability of Artificial Ice Making 167 CHAPTER VI. COLD STORAGE. COLD STORAGE. Storage Rooms, Their Construction and Size, Construction of Wood 168 Construction of Brick and Tiles, and Other Constructions.. 169-1 73 REFRIGERATION REQUIRED for Storage Rooms Expressed in Units per Cubic Foot fib Piping Cold Storage Rooms, Refrigeration Required Found by Calculation, Radiation through Walls, Transmission of Heat through Walls (tables) 174-182 REFRIGERATION OF GOODS for Cold Storage, Calculation of Amount, Specific Heat of Victuals (table) . . . , 182 Calculation of Specific Heat of Victuals, Freezing Goods in Cold Storage, Refrigeration Required 183 Conditions Obtaining in Cold" Storage, Ventilation, Moisture, Dry Air for Cold Storage, Forced Circulation 184-188 COLD STORAGE TEMPERATURES. Storing Fruits, Table Showing Best Temperature for Different Fruits 188 Storing Vegetables, Onions, Pears, Lemons, Grapes, Apples, Liquors, etc 189-192 Storing Fish and Oysters (table). Freezing Fish, Storage of Butter, Cheese, Milk, Eggs and Similar Products 193-195 Miscellaneous Goods (Table of Storage Temperatures), Ven- tilation of Rooms, Lowest Cold Storage Temperatures.... 196 CHAPTER VII. BREWERY REFRIGERATION. OBJECTS OF BREWERY REFRIGERATION. Cooling Wort, Removal of Heat of Fermentation, Storage of Beer. Rough Estimate of Refrigeration, Specific Heat of Wort (table).. 197 TABLE OF CONTENTS. viii PROCESS OF COOLING WORT. Cooling Vat, Tubular Cooler, Refrigeration, Required for Cooling Wort, Simple Rule for Calculation of Same 198 Size of Machine for Wort Cooling, Increased Efficiency of Ma- chine in Wort Cooling 199 HEAT PRODUCED BY FERMENTATION. Calculation of Heat of Fermentation in Breweries, Simple Rule for Same 300 Refrigeration for Storage Rooms Expressed in Units per Cubic Foot and per Square Foot of Walls, Closer Calculations.. . 201 Different Saccharometers. Table of Comparison of Them 202 Cooling Brine and Sweet Water, Total Refrigeration, Distri- bution of Fermentation, Dimensions of Wort Cooler 203 Direct Expansion Wort Cooler 204 Piping of Rooms in the Brewery, Amount Required, Temper- ature of Rooms, Heat of Fermentation Allowed for 204-206 REFRIGERATION FOR ALE BREWERIES. Amount Re- quired for Wort Cooling and for Storage, etc. Rule for Piping ; 206-207 Attemperators, Chilling of Beer, Brewery Site, Storage of Hops 207-210 Refrigeration in Malt Houses, Actual Refrigerating Installa- tion in Breweries o of Different Capacities 211 CHAPTER VIII. REFRIGERATION FOR PACKING HOUSES, ETC. AMOUNT OF REFRIGERATION REQUIRED. Theoretical Calculation of Same, Practical Rules for Same (Units per Cubic Foot), Calculation per Number of Animals, Freez- ing of Meaf 212 Other Methods of Calculating Required Refrigeration, Rules for Piping of Rooms (Cubic Feet per Foot of Pipe) 213 Storage Temperatures for Meat (table), Official Views on Meat Storage, Freezing, etc. 214 Best Way of Freezing Meat, Circulation of Air in Rooms, Ship- ping Meat, Bone Stink, Defrosting Meat, etc 215-217 Refrigeration in Oil Works, Oleomargarine, Stearin and India Rubber Works, Dairy Refrigeration, Refrigeration for Glue Works, Skating Rinks, etc 218-220 Refrigeration in Chemical Works 220-321 Concentration of Sulphuric Acid by Cold, Decomposition of Salt Cake, Pipe Line Refrigeration, Refrigeration and En- gineering 221 CHAPTER IX. THE ABSORPTION SYSTEM. CYCLE OF. OPERATIONS. A Compound Cycle, Application of First Law to Same, Equation of Absorption Cycle 222 Working Conditions of System, Heat Added in Sef rigeration . 223 Heat Introduced by Pump, Amount of Rich Liquor to be Cir- culated ; 224 STRENGTH OF RICH AND POOR LIQUOR. Heat Removed in Condenser, Heat. Removed in Absorber 225 Heat of Absorption, Formula to Calculate Same, Table Show- ing Same, Heat Introduced by Poor Liquor 225-226 Negative Heat Introduced by Vapor, Heat Required in Gener- ator,. Work by Pump, Anhydrous Ammonia Required 227 HORSE POWER OF AMMONIA PUMP. Amount of Con- denser Water Required, Water Required in Absorber 228 Economizing Water, Economizing Steam, Steam Required.. . 229 Actual and Theoretical Capacity, Heat Used in Still 230 Expression of Efficiency, Comparable Efficiency of Compressor 231 CONSTRUCTION OF ABSORPTION MACHINE. The Gener- ator, the Analyzer, Battery Generator, Size of Still, the Condenser 232-233 viii TABLE OF CONTENTS. The Rectifier, Liquid Receiver, etc., the Absorber, the Ex- ch ang er 234-236 The Exchanger, the Heater, the Cooler, the Ammonia Pump, Miscellaneous Attachments 236-237 Overhauling Plant, Compression vs. Absorption, Tabulated Dimensions 238-239 CHAPTER X. THE CARBONIC ACID MACHINE. General Considerations. Properties of Carbonic Acid Gas (table )...'. 240-241 Construction of Plant, Compressor, Stuffing Box, Glycerine Trap, Condenser, Evaporator, Safety Valve 242-243 Joints, Strength and Safety, Application of Machine, Effi- ciency of System 244-245 Comparisons of Efficiency, Practical Comparative Tests .. .246-247 CHAPTER XL-OTHER COMPRESSION SYSTEMS. AVAILABLE REFRIGERATING FLUIDS. Table Showing Vapor Tension of Ether, Sulphur Dioxide/Methylic Ether, Carbonic Acid, Pictet Liquid and Ammonia 248 Methyl and Ethyl Chloride Machine 249 REFRIGERATION BY SULPHUR DIOXIDE. Properties of Sulphur Dioxide : 249 Table of Properties of Saturated Sulphur Dioxide Gas, Useful Efficiency. Table of Comparison of Ammonia and Sulphur Dioxide Plant 250 ETHER MACHINES. Table Showing Properties of Saturated Vapor of Ether, Practical Efficiency of Ether Machines. 251-252 REFRIGERATION BY PICTET'S LIQUID. Table Showing Properties of Liquid, Anomalous Behavior of Pictet's Liquid, Explanations for the Anomaly 252-253 Bluemcke on Pictet's Liquid .- . . 253 Mottay and Rossi's System, Cryogene, Hydrocarbons as Re- frigerating Agents, Acetylene, Naphtha, Chimogene, etc.. 264 CHAPTER XII. AIR AND VACUUM MACHINES. COMPRESSED AIR MACHINE. Cycle of Operations, Work of Compression of Air 255 Temperature of Air after Compression, Cooling of Air after Compression. Amount of Water Required, Work Done by Expansion 256 Temperature after Expansion, Refrigeration Produced, Work for Lifting Heat, Equation of Cycle 257 Efficiency of Cycle, Size of Cylinders, Actual Efficiency 258 Experiments Showing Actual Performance on Cold Air Ma- chines (table) 359 Work Required for Isothermal Compression, Work Done in Isothermal Expansion, Other Use's of Compressed Air, Table Showing Friction by Compressed Air in Pipes 260 Calculated Efficiency of Compression Air Machine, Limited Usefulness ; .... 261 VACUUM MACHINES. - Refrigeration Produced by Them, Efficiency and Size 261-262 Compound Vacuum Machine, Expense of Operating, Objec- tions to Sulphurous Acid, Southby's Vacuum Machine.. 262-263 Southby's Vacuum Machine, Operating Same 284 CHAPTER XIII. LIQUEFACTION OF GASES. Historical Points, Self-intensifying Refrigeration 265 Linde's Simple Method, the Rationale of Linde's Device. . . .266-267 Variable Efficiency, Hampson's Device, Other Methods 268 Triplcr's Invention 60 .TABLE OF CONTENTS. ix Uses of Liquid Air 270-271 Tabulated Properties of Gases 272 CHAPTER XIV. MANAGEMENT OF COMPRESSION PLANT. INSTALLATION OF COMPRESSION PLANT.-Proving of Machine, Pumping a Vacuum, Charging the Plant 273 Charging by Degrees, Operation of Plant, Detection of Leaks, Mending Leaks 27* Amount of Ammonia Required, Waste of Ammonia 5375 Ammonia in Case of Fire. 276 Condenser and Back Pressure in Different Cases 277 Table Showing Efficiency of Plant under Different Conditions. 278 Permanent Gases in Plant, Freezing Back 279 Origin of Permanent Gases, Clearance, Valve Lift 280 Packing Pistons, Pounding Pumps, etc., Cleaning Coils, etc.. . 281 Insulation, Lubrication, etc 283 CHAPTER XV. MANAGEMENT OF ABSORPTION PLANT. Management and Installation of Plant, Ammonia Required Charging of Plant Recharging Absorption Plant, Charging with Strong Liquor and Anhydrous Ammonia 285 Permanent Gases in Plant 286 Corrosion of Coils, Kinds of Aqua Ammonia '. 287 Leaks in Absorption Plant, Leak in Exchanger, Leak in Rec- tifying Pans, Strong Liquor Siphoned over 288-289 Th.e "Boil -over," Cleaning the Absorber, Operating the Ab- sorber, Packing Ammonia Pump 290-292 Economizing Water, Operating Brine Tank, Leaks in Brine Tank 293 Top and Bottom Feed Coils, Cleaning Brine Coils, Dripping Celling, Removing Ice from Coils, Cost of Refrigeration, Management of Other Plants .... 294-295 CHAPTER XVI. TESTING OF PLANT. Test of Plant, Fitting up for Test, Mercury Wells ,296 The Indicator Diagram, Maximum and Actual Capacity. . . 297-301 Commercial Capacity, Nominal Compressor Capacities (table), Actual Refrigerating Capacity 302 Friction of Compressor, Heat Removed in Condenser, Maxi- mum Theoretical Capacity, Correct Basis for Efficiency Calculation 303 More Elaborate Test, Table Showing Data of Tests of Com- pression Plant. 304 Efficiency of Engine and Boiler, Test of Absorption Plant 305 Table Showing Results of Test, Estimate and Proposals 306 Contracts, How Made 307 Unit of Refrigerating Capacity, Test of Various Machines .... 308 APPENDIX I. TABLES, ETC. Mensuration of Surfaces, Polygons 309 Properties of the Circle, Mensuration of Solids, Polyhedrons. 310 Table of Ammonia Gas (Superheated Vapor) 311 Square Roots and Cubic Roots, 1-20. (table) 312 Squares and Cubes and Roots, 1-100 (table) 313 Areas of Circles, Equivalents of Fractions of an Inch 314 Tables of Logarithms, 1-999 .. 315-316 Rules for Logarithms 317 Tables of Weights and Measures, Troy Weight, Commercial Weight, Apothecaries' Weight, Long Measure 317 X TABLE OF CONTENTS. Inches and Equivalents in Feet, Square or Land Measure, Cubic or Solid Measure, Liquid Measure, Dry. Measure.... 318 The Metric Measure, Measure of Length, of Liquids* Etc 319 Equivalents of French and English Measure 319 Specific Gravity and Weight of Materials (tables) 319-321 Cpntents of Cylinders, Table of Gallons 322 Comparison of Metric and United States Weights and Meas- ures, Comparison of Alcoholometers.... 323 Horse Power of Belting (table) , Horse Power of Shafting (table) ... ! * 324 Capacity of Tanks in Barrels ( table) .325 Table of Converting Feet of Water into Pressure per Square Inch, Table of Horse Power Required to Raise Water 32,6 Table Showing Loss of Pressure of Water, etc., while Run- ning through Pipes , 327 Flow of Steam through Pipes, Horse Powers of Boilers 328 Tables Shoeing Properties of Saturated Ammonia 1 329-331 Humidity and Moisture in Air, Latent Heat of Fusion and Volatilization :.... 332 Cold Storage Rates .333-337 Description Of Two-flue Boilers 337 Useful Numbers for Rapid Approximations 338 Weight of Castings 338 Solubility of Gases in Water 339 Dimensions of Double Extra Strong Pipe 339 Dimensions of Corliss Engines 340 Temperature of Different Localities '. 341 Useful Data oh Liquids, Measures, etc.. 1.341-342 Table of Temperature, Fahr. and Cels 343 Specific Gravity Table (Baume) .344 Table on Chloride of Calcium 345 Friction of Water in Pipes 846 Units of Energy (Comparison) . . . .. 346-347 Mean Effective Steam Pressure .348-349 Relative Efficiency of Fuel, Table on Tension of Water Vapor and on Boiling Points 350 Composition of, Water Constituents and Table on Grains and Grams,.. 351 APPENDIX II. PRACTICAL, EXAMPLES. Introductory Remarks, Fortifying Ammonia Charge 353 Numerical Examples on Specific Heat, Evaporation Power of Coal, Capacity of Freezing Mixture, .-....- 354 Numerical Examples on Permanent Gases, Examples Show- ing Use of Gas Equation 355 Work Required to Lift Heat, Refrigerating Effect of Sulphur- ous Acid, Refrigerating Capacity of a Compressor 350 Second Method of Calculation of Compressor Capacity, Third Method of Calculation, Cooling Beer Wort 857 Heat by Absorption of Ammonia Water, Rich Liquor to be Circulated in Absorption Machine 358 Numerical Calculation of Capacity of Absorption Machine, Heat and Steam Required for Same 359 Numerical Examples on Cold Storage, by Calculation, by an Appropriate Estimate 380 Calculation of Piping-Required 361 Numerical Examples on Natural Gas with Reference to Re- frigerating Purposes, Temperature of Same after Expan- sion 363 TABLE OF CONTENTS. xi Refrigerating Capacity of Gas, Work Done by Expansion, Size of Expanding Engine . 363 Expansion of the Gas without Doing Work, Refrigeration Ob- tainable by Expansion. Alone, Calculation of Refrigerating Duty : 364-365 Calculating Ice Making Capacity, Volume of Carbonic Acid Gas , 366 Horse Power of Steam Engine 307 Calculation of Pump.. 368 Motive Power of Liquid Air 3A9 Moisture in Cold Storage 370 Carbonic Acid Machine 371 APPENDIX III. LITERATURE ON THERMODYNAMICS, ETC. a. Books 372-373 b. Catalogues........ 374 TOPICAL INDEX... ...375-387 MECHANICAL REFRIGERATION. PART I. GENERAL ENERGETICS. CHAPTER I. MATTER. MATTER. Matter is everything which occupies space in three directions, and prevents other matter from occupying the same space at the same time. Matter is differen- tiated by its physical and chemical properties, color, hard- ness, weight, chemical changeability, etc. GENERAL PROPERTIES OF MATTER. The general properties of matter which are shared by all bodies are impenetrability, extension, divisibility, porosity, compressibility, elasticity, mobility and inertia, CONSTITUTION OF MATTER. To explain the different properties it is generally as- sumed that matter is ultimately composed of infinitely small particles called atoms, which aggregate or unite to form still infinitely small groups called molecules. At- tractive and repulsive forces acting between the atoms and molecules, and their respective motions are made to account for the various physical and chemical phenomena. SOLID MATTER. Matter is solid when the molecules possess a suffi- cient degree of immobility to insure the permanence of shape. LIQUID MATTER. If the molecules of a body are sufficiently movable to allow of its being shaped by the surrounding vessel, and if the same can be easily poured, it is called a liquid. GASEOUS MATTER. The gaseous state of matter is characterized by almost perfect freedom of motion of the molecules, an unlimited tendency to expand and a great compressibility. The term fluid covers both the liquid and the gaseous states. <5 MECHANICAL REFRIGERATION. BODY. A body is a limited amount of matter. MASS. Mass is the quantity of matter contained in a body. UNIT OF MASS. The unit of mass is the standard pound, which in the form of a piece of platinum is preserved by the gov- ernment. WEIGHT. Weight, or absolute weight, is the pressure of a body exerted on its support. The unit of weight is the force necessary to support one pound in vacuo, and it differs with the latitude, as the gravity or the earth's attraction. MASS AND WEIGHT. The relations between mass and weight are expressed by the equation W M =J in which M stands for mass, W for weight and g for the acceleration caused by the attraction of the earth. MEASUREMENT OF SPACE. The unit of measurement of space is the cubic foot and its subdivisions (see tables of weight and measures in appendix, etc). DENSITY. Equal amounts of matter do not necessarily occupy the same space; in other words, the density of different bodies is not the same. SPECIFIC WEIGHT. The relative density of different bodies is expressed by their specific gravity, which is the figure obtained when the weight of a body is divided by the weight of an equal volume of water. The specific weights used in the arts and industries are given in tables in Appendix 1. FUNDAMENTAL UNITS. The fundamental units of measurement are the units of distance, time and mass, DERIVED UNITS. From the fundamental units units for more complex quantities may be derived. As the fundamental units vary in different countries, the derived units vary also. FORCE. 7 C. G. S. UNITS. Besides our national units, the units derived from the French or metric system are also frequently em- ployed. They are designated as the centimeter-gramme- second units; abbreviated C. & *. units, and are also called absolute units. CHAPTER II. MOTION; FORCE. MOTION. The removal of matter from one place to another. FORCE. Any cause which changes or tends to change the condition of rest or motion of a body (in a straight line). MEASUREMENT OF FORCE. Force may be measured by the change of momentum it produces in a second. The unit of force is a dyne; it is based on the metric system, and represents that force which, after acting for a second, will give to a gram of matter a velocity of one centimeter per second. GRAVITATION. The tendency which is common to all matter, and according to which all bodies mutually attract each other with an intensity proportional to their masses and in- versely as the square of their distances, is called gravita- tion. The force of the earth attraction at its surface is equivalent to 981 dynes. MOLECULAR FORCES. The attraction and repulsion which exist between the minute and most minute parts or atoms of bodies are often referred to as the molecular forces. COHESION. Cohesion designates the attraction existing be- tween the minute parts of the same body; and for solids it is measured by the force expressed in pounds to tear apart by a straight pull a rod of one square inch area of section. This measure is also called the tenacity of a body (tons). The relative tenacities of the metals are given ap- proximately in the table below, lead being taken as the standard. Lead 1.0 Castiron 7to 12 Tin 1.3 Wroughtiron 20to 40 Zinc 2.0 Steel 40 to 143 Worked copper 12 to 20 g MECHANICAL REFRIGERATION. ADHESION. Adhesion designates the attraction between the parts of dissimilar bodies. CHEMICAL AFFINITY. This expression generally stands for the relative at- traction existing between the smallest particles (atoms and molecules)pf different substances, which, if satisfied, brings about substantial or chemical changes. WORK. Work is the product of force by the distance through which it acts. The unit of work is the product of the units of its factors, force and space. Useful work is that which brings about a specific useful effect, and lost work is that which is incidentally wasted while producing such effect. UNIT OF WORK. The unit of work is the foot-pound, i. e., the work necessary to raise one pound vertically through a dis- tance of one foot. One pound raised vertically through a distance of ten feet, or ten pounds raised through one foot, or five pounds raised through two feet, all represent the same amount of work, i. e., ten foot-pounds. TIME. The interval between two phenomena or changes of condition. The unit of time is the hour and its sub- divisions. POWER HORSE POWER. Power is the rate at which work is done, and is there- fore equivalent to the quantity of work done in the uoit of time, expressed in foot-pounds, kilogram- meters, etc., per hour, minute or second. The unit commonly employed is the horse power, which is defined as work done at the rate of 550 foot-pounds per second, or 1,980,000 foot pounds per hour. VELOCITY. The length, Z, of path traversed by a moving body in the unit of time, t; therefore fTT- V standing for velocity. MOMENTUM. Momentum is the product of mass (in motion) mul- tiplied by its velocity or force multiplied by the time* during which it acts. ENERGY. 9 INERTIA. Inertia expresses the inability of a body to change its condition of rest or motion, unless some force acts on it. LAWS OF MOTION. Newton propounded the following laws of motion: 1. A free body tends to continue in the state in which it exists at the time, either at rest or in uniform rectilinear motion. 2. All change of motion in a body free to move is proportional to the force applied, and it is in the direction of that force. 3. The reaction of a body acted upon by the im- pressed force is equal, and directly opposed to, that force. STATICS. Statics is that branch of science which treats of the relation of forces in any system where no motion results from such action. DYNAMICS OB KINETICS. Dynamics or kinetics treats of the motion produced in ponderable bodies by the action of forces. CHAPTER III.-ENERGY. ENERGY. Energy is the power or quality for doing work. We distinguish between different forms of energy, viz.: VISIBLE ENERGY. This is the energy of visible motions and positions, and is subdivided as follows: KINETIC ENERGY. Kinetic or actual energy is energy which a body possesses by virtue of its motion, such as the energy of winds, ocean currents, etc. POTENTIAL ENERGY. Potential or latent energy is that kind of energy which a body possesses by virtue of its position, a head of water, a raised weight, a coiled spring, etc. MOLECULAR ENERGY. The molecular energy comprises the energy of radi- ation or radiated matter, i. e. t electricity, light, heat, 10 MECHANICAL REFRIGERATION. etc.; molecular, potential energy or energy of chemical affinity, etc. C. G. S. UNIT OF ENERGY. The unit of energy is one-half of the energy pos- sessed by a gramme of mass when moving with a velocity of one centimeter per second. This unit is called the erg. The erg may also be defined as the work accom- plished when a body is moved through a distance pf one centimeter with the force of one dyne, that is a "Dyne Centimeter." One million ergs is called a megerg. CONSERVATION OF ENERGY. The total amount of energy in the universe, or in any limited system which neither receives nor loses any energy to outside matter is invariable and constant. TRANSFORMATION OF ENERGY. The different forms of energy are convertible or transformable into each other, so that when one form of energy disappears, an exact equivalent of another form or kind of energy always makes its appearance. (See 44 Dissipation of Energy.") PHYSICS. la the science which treats of the 'transformations and transference of energy, broadly speaking. SUBDIVISIONS OF PHYSICS. Physics, therefore, is subdivided into a science of op- tics or radiation, a science of heat, of mechanics, of electricity and of chemistry. Other distinct branches of science treat on the specific relations between two kinds of energies; for this reason we speak of thermodynamics, electro-chemistry, photochemistry, thermochemistry, electro-dynamics, etc. DISSIPATION OF ENERGY. In our efforts to transform one form of energy into another, a certain portion of the first energy always as- sumes a lower degree of tension; it is dissipated and now represents an amount of energy of less availability for useful purposes. ENERGY OF A MOVING BODY. The amount of kinetic energy possessed by a body by virtue of its motion may be expressed by the formula E= Mv* in which E stands for energy, M for mass and v for velo- city. HEAT. U MECHANISMS. A machine or a mechanism is a contrivance enabling us to transform mechanical energy, by changing the direction, power and velocity of available forces to make them serviceable for useful proposes. The energy sup- plied to a machine is partly employed to do the useful work required, and partly it is consumed in doing what is called internal work, by overcoming friction, etc. It is the lost work of the machine, and the less the latter the more perfect is the machine. CHAPTER IV.-HEAT. HEAT. Heat is a form of energy, and represented by the kinetic energy of the molecules of a body. SOURCES OF HEAT. As sources of heat we may quote: Friction, percus- sion and pressure, solar radiation, terrestrial heat, mo- lecular action, change of condition, electricity, chemical combination, more especially combustion. RADIANT HEAT. The foregoing definition, while it accounts for the phenomena of bodily and conducted heat, does not ac- count for the conditions which obtain when heat passes from one body to a distant other body without a ponder- able intervening medium, or without perceptibly heating the intervening medium, i. e., the radiation of heat. To explain these conditions in harmony with t.he mechanical or molecular theory of physics, it is supposed that the radiant heat is in the nature of a wave motion propa- gated .by means of a hypothetical substance, the ether. ETHER. The hypothetical ether which is the supposed vehicle for the transmission of the supposed wave motion consti- tuting radiant energy (radiant heat as well as light), in order to accomplish such transmission in accordance with the present conceptions of these phenomena would have to possess the following properties: "Its density would have to be such that a volume of it equal to about twenty volumes of the earth would weigh one pound; its pressure 12 MECHANICAL REFRIGERATION. per square mile would be about one pound, and the heat required to elevate the temperature of one pound for 1 F would have to be equal to the amount of heat required to raise the temperature of about 2,300,000,000 tons of water for one degree. Such a medium would satisfy the require- ments of nature in being able to transmit a wave of light or heat 180,000 miles per second, and to transmit some 130 foot-pounds of heat energy from the sun to the earth, each second per square foot of heat normally exposed, and also be everywhere practically non-resisting and sensibly uniform in temperature, density and elasticity." (Wood.) RADIANT HEAT AND LIGHT. Kadiant heat follows the same laws regarding re- fraction, reflection, polarization, etc., as does light. TEMPERATURE. The temperature of a body is proportional to the average kinetic energy of its molecules, and is measured by the thermometer. THERMOMETER. The most prevalent form of thermometer consists of a body of mercury, enclosed in a glass tube so that slight variations of expansion due to change of temperature can be read of on the scale attached. Other substances, like alcohol, air, etc., are also used as thermometric sub- stances instead of mercury. THERMOMETER SCALES. Three different scales are in use for thermometers, the "Fahrenheit" in England and United States, the " Eeaumur " in Germany and the "Celsius" or "Centi- grade" ia France, and for scientific and technical pur poses, more or less, all over the world. The scales of the different thermometers compare as follows: Freezingpoint Boiling point of water. of water. Fahrenheit 32 213 Centigrade 100 Reaumur If we designate the scales by their initials the follow- ing rules apply for the conversion of the degrees in one another* C.=|(F. 32)=f R. E.=f (P. 32)=| C. F.= C.+32=f R.H-32 HEAT. COMPARISON OF THERMOMETER SCALES. 13 R. C. F. R. C. F. +80 79 +100 98.75 +212 209.75 +23 22 +28.75 27.50 +83.75 81.50 78 97.50 207.50 21 26.25 79.25 77 96.25 205.25 20 25 77 76 95 203 19 23.75 74.75 75 93.75 200.75 18 22.50 72.50 74 92.50 198.50 17 21.25 70.25 73 91.25 196.25 16 20 68 72 90 194 15 18.75 65.75 71 88.75 191.75 14 17.50 63.50 70 87.50 189.50 13 16.25 61.25 69 86.25 187.25 12 15 59 68 85 185 11 13.75 56.75 67 83.75 182.75 10 12.50 54.50 6(5 82.50 180.50 9 11.25 52.25 65 81.25 178.25 8 10 50 64 80 176 7 8.75 47.75 63 78.75 173.75 6 7.50 45.50 62 77.50 171.50 6 6.25 43.25 61 76.25 169.25 4 5 41 60 75 167 3 3.75 38.75 59 73.75 -164.75 2 2.50 36.50 58 72.50 162.50 1 1.25 34.25 57 71.25 J60.25 32 56 70 158 1 1.25 29.75 55 68.75 155.75 3 2.50 27.50 54 67.50 153.50 3 3.75 25 25 53 66.25 151.25 4 5 23 SB 65 149 5 6.25 20.75 51 63.75 146.75 6 7.50 18.50 50 62.50 144.50 7 8.75 16.25 49 61.25 142.25 8 10 14 48 60 140 9 11.25 11.75 47 58.75 137.75 10 12.50 9.50 46 57.50 135.50 11 13.75 7.25 45 56.25 133.25 12 15 5 44 55 131 13 16.25 2.75 43 53.75 128.75 14 17.50 0.50 42 52.50 126.50 15 18.75 1.75 41 51.25 124.25 16 20 4 40 50 122 17 21.25 6.25 39 48.75 119.75 18 22.50 8.50 38 47.50 117.50 19 23.75 10.75 37 46.25 115.25 20 25 13 36 45 113 21 26.25 15.25 35 43.75 110.75 22 27.50 17.50 34 42.50 108.50 23 2S.75 19.75 33 41.25 106.25 24 30 22 32 40 104 25 31.25 24.25 31 38.75 101.75 26 32.50 26.50 30 37.50 99.50 27 33.75 28.75 29 36.25 97.25 28 35 31 28 35 95 29 36.25 33.25 27 33.75 92.75 30 37.50 35.50 26 32.50 90.50 31 38.75 37.75 25 31.25 88.25 32 40 40 24 30 86 MEASURING HIGH TEMPERATURES. Temperatures which are beyond the reach of the mercurial thermometers (over 500) are measured by pyrometers constructed to meet the wants of specific cases. High temperatures may be estimated approxi- 14 MECHANICAL REFRIGERATION. mateJy by heating a piece of iron of the weight w up to the unknown temperature T, and then immersing the same into a known weight, W, of water of the tempera- ture t. Then if t is the temperature of the water after immersion and s the specific heat of the iron or other metal, T is found after the formula: ABSOLUTE ZERO. The zero points on the scales of thermometers men tioned are arbitrarily fixed, since the expressions of warm and cold have only a relative significance. The rea\ zero point of temperature, that is, that point at which the molecules have lost all motion, the energy of which represents itself as heat, is supposed to be, and in all proba- bility is over 460 F. below the zero of the Fahrenheit thermometer. At that temperature there is an entire ab- sence of heat and demonstrations of heat phenomena, and above that the differences in temperatures are only such of degree, but not in kind. Hence the impropriety of speaking of heat and cold as such. If t is a given temperature in degrees Fahrenheit the corresponding degrees T expressed in absolute tem- perature are found after the formula T=461 + . UNIT OF HEAT. The quantity of heat contained in a body is the sum of the kinetic energy of its molecules. Heat is meas- ured quantitatively by the heat unit, which also varies in different parts like other standards. The unit used in the United States and England is the British Thermal Unit (abbreviated B.T.U.) and represents the amount of heat required to raise the temperature of one pound of water 1 F. The French unit is the calorie, and is the quantity of heat required to raise the temperature of one kilogram of water from to 1 Celsius. Some writers define the B. T. unit as the heat re- quired to raise the temperature of one pound of water from 32 to 33. Others make this temperature from 60 to 61, and still others define it as that amount of heat required to raise ^ pound of water from the freez- ing to the boiling point. The two last definitions give nearly the same result, and may be considered practically identical. HEAT. 15 C. G. S. UNIT OF HEAT. We have no unit for heat corresponding to the C. G. S. or absolute system. The small French calorie, being the heat required to elevate the temperature of one gram of water for 1 Celsius (from 17 to 18) is equivalent to 41,- 830,000 ergs. CAPACITY FOR HEAT. The number of heat units required to raise the tem- perature of a body for one degree is called its heat capacity. It gradually increases with the temperature. SPECIFIC HEAT. The ratio of the capacity for heat of a body to that of an equal weight of water is specific heat. Hence the figure expressing the capacity for heat of one pound of a body in B. T. U. expresses also its specific heat, and vice versa. SPECIFIC HEAT OF METALS. Antimony , .0507 Manganese . .. 1441 Bismuth .0308 Mercury, solid .0319 .0939 " liquid 0333 Copper .0951 Nickel 1086 Cymbal metal .086 PlatinuTi, shfifit 0324 Gold .0324 " SDOnfifV .0329 Iridium .1887 Silver... .0570 Iron, cast .1298 Steel .1165 " wrought .1138 Tin .0569 Lead .0314 Zinc .0859 SPECIFIC HEAT OF OTHER SUBSTANCES. STONES. Brickwork and masonry.. Marble .20 .2129 .2148 .2169 .2174 .2411 .2415 .2031 .2008 .2017 CARBONACEOUS Cont. Graphite natural . . . .' .2019 .197 .1977 .604 .2503 .2311 .0872 .1966 .2026 r< of blast furnaces SUNDRY. Glass... Chalk Quicklime ... Magnesian limestone CARBONACEOUS. Coal ... . Ice .... Phosphorus. Soda . Sulphate of lead Cannel coke " of lime Coke of pit coal Anthracite SPECIFIC HEAT OF LIQUIDS. 6588 Turpentine . 4160 Benzine .3932 Vinegar 9200 Mercury .0333 Water, at 32" F 1 0000 Olive oil 3096 212 F 1 0130 Sulphuric acid: Density, 1 87 3346 32 to 212" F Wood spirit . . 1.0050 6009 1.30 \6614 Proof spirit 973 16 MECHANICAL REFRIGERATION. SPECIFIC HEAT OF WATER AT VARIOUS TEMPERATURES. Heat to Raise Heat to Raise Tempe- rature. Specific Heat. 1 Ib. of Water from 32 F. to Given Tempe- rature. Specific Heat. lib. of Water from 32 F. to Given Temperature. Temperature. Fahr. Units. Fahr. Units. 32 .0000 0.000 248 1.0177 217.449 60 .0005 18.004 266 1.0204 235.791 68 .0012 36.018 284 1.0232 254.187 86 .0020 54.047 302 1.0262 272.628 104 .0030 72.090 320 1.0294 291.132 122 .0012 90.157 338 1.0328 309.690 140 .0056 108.247 356 1.0364 328.320 158 .0072 126.378 374 1.0401 347.004 176 .0089 144.508 392 1.0440 365.760 194 .0109 162. 686 410 1.0481 384.588 212 .0130 180.900 428 1.0524 403.488 230 .C153 199.152 446 1.0568 422.478 USE OF SPECIFIC HEAT. The amount of heat or cold necessary to elevate or lower the temperature of w pounds of a body having the specific heat c for t degrees is found after the follow- ing equation: . 8 = c X t X w DETERMINATION OF SPECIFIC HEAT. The specific heat of various bodies can be found from the table, and it may also be determined experi- mentally as follows for solid substances (to find the specific heats of liquids the same principle is followed, care being taken that the liquids to be mixed have no chemical affinity for each other): Take a known weight, w, of the substance whose specific heat is to be determined, and let it have a known temperature, t (above that of the atmosphere), then immerse it in a known weight, v, of water having the temperature t' and now observe the temperature, z y acquired by the mixture. From these quantities the specific heat, x, of the substance can be cal- culated after the formula v (zf) x=}- ( w(t z) If the substance is soluble in water any other liquid whose specific heat is known may be used instead. This method, while it might answer for rough determinations, would have to be surrounded by special safeguards in order to allow for loss by radiation of the vessel, etc., in order to be applicable for exact determinations. TEMPERATURE OF MIXTURES. If two substances having respectively the weight w and w^, the temperatures t and t lt and the specific heat s HEAT. 17 and s lt are mixed without loss or gain of heat, the tem- perature, T, of the mixture is: W S--Wt S EXPANSION BY HEAT. When a body becomes warmer it expands,when it be- comes cooler it contracts, a rule of which ice, however, is one of the exceptions. EXPANSION OF SOLIDS. Amount of linear expansion of solids may be com- puted by the following formula for the Fahrenheit scale; ^180 in which .L t is the length of a bar at any temperature, t l% knowing its length, L, at any other temperature, t, and a is a coefficient to be obtained from the following table: COEFFICIENT OF EXPANSION FROM 32 TO 210 F. Glass .................. 0.000,861,30 Pine wood (length wise)... 0.000,3 Platinum ............. 0.000,884,20 Oak wood .................. 0.000,7 Steel, soft ............. 0.001,078,80 Granite .................... 0.000,8 Iron, cast ............. 0.001,125,00 Limestone ................. 0. 000,8 Iron, wrought ........ 0.001.220,40 Antimony ................. 0.001,1 Steel, hardened ...... 0. 001,239,50 Gold ........................ .001,4 Copper ................ 0.001,718,20 Ebonite .................... 0.001,7 Bronze ............... 0.001,816,70 Nickel ........... ........... 0.001,8 Brass ................ ..0.001,878,20 Silver ...................... 0.001.9 Tin .................... 0.002,173,00 Aluminum ................. 0.002,3 Lead .................. 0.002,857,60 Pine wood (crosswise) ..... 0.005,8 Zinc ................... 0.002,941,70 Mercury (in glass tube) . . .0.018,2 EXPANSION OF LIQUIDS. The expansion of liquids by heat is expressed by the volume of a given quantity of liquid at different temper- atures, as is done in the following table for water, show- ing also that at the point of maximum density. The maximum density of water, as appears from this table, is between 32P and 46 F.; above 46 the volume increases, but below 32 it increases also. Apparently this is an exception to the general rule that all bodies expand by heat and contract when the temperature is lowered. This exception, however, may be accounted for when we assume that at 32, when the water passes from the liquid to the solid state, its molecular constitu- tion is changed also, which is also indicated by th change in specific heat at this point. 18 MECHANICAL REFRIGERATION. EXPANSION AND WEIGHT OF WATER AT VARIOUS TEMPERATURES. Tem- Relative Volume W eight of One Weight of One Tem- Relative Volume Weight of One Weight of One pera- ture. by Ex- pansion. Cubic Foot. Imperial* Gallon. pera- ture. by Ex- pansion. Cubic Foot. Imperial* Gallon. Fahr. Pounds. Pounds. Pahr. Pounds. Pounds. 32 1.00000 62.418 10.0101 100 .00639 62.022 9.947 35 .99993 62.422 10.0103 105 .00739 61.960 9.937 f 62.425 1 110 .00889 61.868 9.922 39.1 . 99989 1 53 103.7 233.7 2.25 2 53 49. 4 .104.4 U 2.11 3 52.5 25 .4 46.45 1.83 4 52 14 .3 19.7 1.39 1 60 62.3 99.5 1.59 2 60 45.8 69.9 1.53 3 60 33.9 49.5 1.46 4 59 27.3 38.2 1.40 Temperature of I the atmosphere V Fahr ) Average differ-1 ence of temper- | aturesof thewa- ^ ter and the air Fahr J Total heat emit- ted per square foot per hour. Units Heat emitted per 1 1 F. difference of temperature Units... Tredgold experimented with small vessels of different materials, in which water was cooled from a temperature of 180 to one of 159, in a room at 5 GP. The heat emitted per square foot per hour per degree of mean difference of temperature was as follows: Tin plate 1.37 units. Sheetiron 2.24 " Glass 2.18 " Also, in a 2>-inch cast iron pipe, ^ inch thick, water was cooled from 152 to 140 F., in a room at 67. The heat emitted per square foot per hour per degree of dif- ference of temperature was as follows: Ordinary rusty surface * 1 . 823 units. Black, varnished -1.900 White (two coats of lead paint) 1.778 TRANSMISSION OF HEAT THROUGH METAL PLATES FROM WATER TO WATER. In a metal tubular refrigerator, hot wort was cooled by water at such a rate that, taking averages, 80 units of heat passed from the wort, and was absorbed by the water per square foot of cooling surface per 1 F. dif- ference of temperature per hour. The water and the wort were moved in opposite directions. M. P6clet proved experimentally that the rate of transmission of heat was directly as the difference of temperature at the two faces of metal plates. 28 MECHANICAL REFRIGERATION. TRANSMISSION OF HEAT THROUGH METAL PLATES FROM STEAM TO WATER. The rate of transmission of heat from steam through a metal plate to water at the other side is practically uniform per degree of difference of temperature. The following table gives average results of performance, from which it appears that the transmission is much more effective for evaporating than for heating water, twice as much for flat copper plate, three times as much for copper pipe, one-fourth more for cast iron plate. Also, that pipe surface is one-fifth more effective than flat plate surface for heating, and more than twice as much for evapora- tionthe result of better circulation, no doubt. HEATING AND EVAPORATING WATER BY STEAM THROUGH METALS. Metal Surface. Per Square Foot per 1 F. Difference of Temperature. Steam Condensed. Heat Transmitted. Heating. Evaporat- ing. Heating. Evaporat- ing. Copper plate Copper pipe Cast-iron boiler. . . Pounds. .248 .291 .077 Pounds. .483 1.070 .105 Units. 276 312 82 Units. 534 1034 100 Mr. Isherwood experimented with cylindrical metal pots, 10 inches in diameter, 213^ inches deep; % inch, 3^ inch and % inch thick; turned and bored. They were placed in a steam bath of from 220 to 320 F. Water at 212 was supplied to the pots, and evaporated. The rate of evaporation' per degree of difference of temperature was the same for all temperatures; and the rate was the same for the different thicknesses. The respective weights of water, and heats consumed per square foot of inside surface per degree of difference were as follows: Copper Brass Wrought iron Cast iron Water at 212f .665 Ib. .577 " .387 " .327 " Heat. 642.5 units 556.8 " 373.6 " 315.7 " The differences of results for the same metal evi- dently arise in part from the comparative activity of cir- culation, and in part from the condition and position of the heating surfaces. HEAT. 29 CONDENSATION OF STEAM IN PIPES OB TUBES BY WATER EXTERNALLY. From the results of experiments with surface con- densers, in which the steam was passed through the tubes, it appears that 500 units of heat by condensation were transmitted per square foot of tube surface per hour per 1 F. difference of temperature. The condensers were arranged in three groups of tubes successively trav- ersed by the condensing water. In another case, where the condenser was arranged in two groups, from 220 to 240 units were transmitted. Mr. B. G. Nichol experimented with an ordinary sur- face condenser brass tube, % inch in diameter outside; No. 18 wire gauge in thickness ; encased in a 3%-inch iron pipe. Steam of 32% pounds total pressure per square inch occupied the interspace, while cold water at 58 F. initial temperature was run through the brass tube. Three experiments were made with the tubes in a vertical position, and three in a horizontal position. Vertical Position. Horizontal Position. 1, 2, 3, 4, 5, 6, Velocity of water through tube, in feet per minute, 81, 278, 390, 78, 307, 415 feet. Steam condensed per square foot of surface per hour, for 1 F. difference of temperature, .335, .436, .457, .480, .603, 609 pound. Heat absorbed by the water, per square foot per hour, per 1 F. difference of temperature, 346, 449, 466, 479, 621, 699 units. The rate of condensation was greater in the hori- zontal position than in the vertical position. Also, the efficiency of the condensing surface was increased by an increase of velocity of the water through the tube, nearly in the ratio of the fourth root of the velocity for vertical tubes; and nearly as the 4.5 root for horizontal tubes, TRANSMISSION OF HEAT THROUGH METAL PLATES OR TUBES, FROM AIR OR OTHER DRY GAS TO WATER. The rate of transmission of convected heat is prob- ably from 2 to 5 units of heat per hour per square foot of surface per 1 F. of difference of temperature. In a locomotive fire box, where radiant heat co-oper- ated with convected heat, the following results have been 30 MECHANICAL REFRIGERATION. obtained in generating steam of 80 pounds pressure per square inch. The temperature of the fire is taken at 2,00(P F. Heat Transmitted Water Evaporated per Square Foot per per Square Foot Hour perl F.Differ- per Hour. ence of Temperature. Burning coke, 75 pounds ) per square foot of > 25% pounds. 14% units. grate ) Burningbriquettes, ) 74% pounds per V 35 20 " square foot of grate ) There are in practice little or no differences between iron, copper and lead in evaporative activity, when the surfaces are dimmed or coated, as under ordinary condi- tions. COMPARATIVE RATE OF EMISSION OF HEAT FROM STEAM PIPES IN AIR AND IN WATER. It appears that for equal total difference of tempera- ture, the rate of emission of heat from steam pipes in water amounts, in round numbers, to from 150 to 250 times the rate in air, according as the pipes are vertical or horizontal. COMPARATIVE RATE OF EMISSION OF HEAT FROM WATER TUBES IN AIR AND IN WATER AT REST AND IN MOTION. It appears that the rate of emission from water- tubes in water was about twenty times the rate in air. Mr. Craddock proved it experimentally to be twenty-five times. When the water tube was moved through the air at a speed of fifty-nine feet per second, it was cooled in one-twelfth of the time occupied in still air. In water, moved at a speed of three feet per second, the water in the tube was cooled in half the time. PASSAGE OF HEAT THROUGH METAL PARTITIONS. From oome recent observations made in Germany the following table, giving the transmission of heat through metal partitions per hour, per square foot and per one degree F. difference between each side, viz.: Smoke or air through metal to air 1.20 to 1.70B. T. U. Steam through metal to air 2. 40 to 3.40 Water through metal to air or reverse 2. 15 to 3.15 " Steam through metal to water 200. 00 to 240.00 " Steam through metal to boiling water 1,000.00 to 1,200.00 Water through metal to water 72. 00 to 96.00 LATENT HEAT. When a body passes from the solid to the liquid state, or from the liquid to the gaseous or vapor state, a HEAT. 31 certain amount of heat is required to bring about the change. As this heat is absorbed during the process of fusion or vaporization it is called latent heat of fusion and latent heat of evaporation (latent heat contained in the vapor). LATENT HEAT OF FUSION. The heat which becomes latent during the fusion or melting of a body is used or absorbed while doing the work of disintegrating the molecular structure, doing internal work as it is called. TABLE SHOWING LATENT HEAT OF FUSION. Thermal units. Ice 142.5 Nitrate of ammonia 113.2 Nitrate of soda 104.1 Phosphate of potash 85 . 1 Nitrate of potash 78.4 Chloride of calcium 64.3 Zinc 50.6 Platinum 48.8 Silver .. 37.8 Thermal units. Tin 25.5 Cadmium 24.5 Bismuth 22 . 7 Sulphur 16.8 Lead 9.5 Phosphorus 9.0 D'Arcet's alloy 8.1 Mercury 6.1 MELTING POINTS, ETC. Fahr. Fahr. j Full Iron, cast, white -j 1992 to Aluminum < red " wrought 2012 2912 1150 617 Bismuth 507 Mercury . . . 39 1690 Silver 1873 Copper 1996 Steel \ 2372 to " pure. 2155 2282 Tin 2552 442 2012 Zinc 773 Carbonic acid 108 120 Ice 32 Sulphur 239 Nitro-glycerine 45 Tallow 92 112 Turpentine ... .... 14 Stearine -j 109 to 120 bleached 143 154 EFFECT OF PRESSURE ON MELTING POINT. Substances which expand during solidification, like water, have their freezing points lowered by pressure, and those which contract in solidification have their freezing points raised by pressure. LATENT HEAT OF SOLUTION. When a body is dissolved in water or in any other liquid, or if two solid bodies (salt and snow, for an ex- ample) mix to form a liquid, a certain amount of heat becomes likewise latent; it is called the latent heat of fusion. Since the latent heat of fusion in the case of 32 MECHANICAL REFRIGERATION. such mixtures is taken from the mixture itself, the tern- perature falls correspondingly, as shown by the table on frigorific mixtures. For practical purposes the mixtures of snow and hydrochloric acid, or, where acid is objectionable, the mixture of snow and potash, is very serviceable to pro- duce refrigeration on a small scale. The mixture of sodium sulphate, ammonium nitrate and nitric acid is also recommendable. LIST OF FRIGORIFIC MIXTURES. Thermometer Sinks Degrees F. Ammonium nitrate 1 part I -, Water 1 " f From + 40 to + 4 Ammonium chloride 5 parts ) Potassium nitrate 5 " > From -f 50 to + 10 Water 16 " ) Ammonium chloride 6 parts "I Potassium nitrate 5 " \ Sodium sulphate 8 " f From + 50 to + 4 Water 16 " J Sodium nitrate 3 parts ) r Nitric acid, diluted 2 " f From + 50 to - 3 Ammonium nitrate 1 part ) Sodium carbonate 1 " V From + 50 to 7 Water 1 " ) Sodium phosphate 9 parts ) r Nitric acid, diluted. 4 ' f From -f- 50 to -12 Sodium sulphate 5 parts I Sulphuric acid, diluted 4 " f From + 50 to -f 3 Sodium sulphate 6 parts 1 Ammonium chloride 4 / ino Potassium nitrate. 2 " f From + 5 to ~ 10 Nitric acid, diluted 4 " J Sodium sulphate 6 parts ) Ammonium nitrate ... 5 > From -f 50 to 40 Nitric acid, diluted 4 } Snow or pounded ice 2 parts \ . -o Sodium chloride 1 Snow or pounded ice 5 parts ) Sodium chloride 2 V to 18 Ammonium chloride 1 ) Snow or pounded ice 24 parts Sodium chloride 10 Ammonium chloride 5 Potassium nitrate 6 Snow or pounded ice 12 parts Sodium chloride 6 Ammonium nitrate 5 to -18 to 25 a to-30 pa ts From + 32 to-5C J pa - ts HEAT. 33 HEAT BY CHEMICAL, COMBINATION. As one of the chi^f sources of heat chemical combina- tion has been mentioned, which may be defined as the process which takes place when the ultimate constituent parts (atoms) of one or more elementary bodies unite with those of another elementary body or bodies to form a substance essentially different in its properties from those of the original bodies. ELEMENTARY BODIES. Substances which cannot be resolved into two or more different substances are called elementary bodies, elements or simple bodies. CHEMICAL ATOMS. Chemically considered, an atom is the smallest parti- cle of matter entering into or existing in combinations. The atomic weight is a number expressing the ratio of the weight of the atoms of an element to the weight of an atom of hydrogen, the latter being taken as unit. MOLECULES. The smallest quantity of an elementary body, as well as of a compound body, which is capable of having an independent existence is called a molecule. A molecule, therefore, is a combination of several atoms of one and the same or of different elements. CHEMICAL SYMBOLS. The chemical elements are expressed by symbols which are the initial letters of their Latin or English name. The symbols also represent the relative quan- tity of one atom of an element. The composition of the molecule of a body is indi- cated by the symbols of its constituents. The num- ber of atoms of each element present is denoted by a number placed at the lower right hand end of the sym- bol. Thus H 2 represents a molecule of hydrogen which is composed of two atoms, and H 2 O represents a molecule of water, which is composed of two atoms of hydrogen and one of oxygen. The atomic weight of hydrogen being 1 and that of oxygen 16, it is readily seen how the formula II 2 O yields the percentage composition by a simple cal- culation. ATOM ,CITY. Atomicity or valence is that property of an element by virtue of which it can hold in combination a definite 34 MECHANICAL REFRIGERATION. number of other atoms, the atomicity of an elementary body is measured by the number of atoms of hydrogen which can be held in combination by an atom of the ele- mentary body in question, the atomicity of hydrogen being taken as unit. Thus by referring to the following table it is readily seen how one atom of chlorine will hold in combination one atom of hydrogen, one atom of oxygen two atoms of hydrogen, one atom of nitrogen three atoms of hydrogen, and one atom of carbon four atoms of hydrogen and form saturated compounds. For obvious reasons the rare and new elements, argon, helium, atherion, etc., are not mentioned. TABLE OF PROPERTIES OF ELEMENTS. Element. Sym- bol. Atom- icity. Atomic Weight. Specific Gravity. Aluminium . Al IV 27 5 2 56 Antimony Sb v 122 6 7 Arsenic . As v 75 5 75 Ba H 137 4 Bismuth . Bi v 208 8 75 Boron B III 11 2 68 Bromine Br I 80 2 96 Cadmium .... Cd II 112 1 58 Calcium Ca if 40 1 65 Carbon .... c IV 12 2 33 Chlorine Cl i 35 5 Chromium Cr VI 52 5 6 5 Cobalt Co VI 58 8 Copper , Cu II 63.5 8.953 Fluorine F I 19 Gold Au III 196 7 19.26 Hydrogen H I 1 Iodine I nr 127 4 948 Iridium Ir VI 198 21 15 Iron .... Fe VI 56 7 79 Lead .... Pb IV 207 11 36 Lithium Li i 7 594 Magnesium . Me ii 24 1 70 Manganese Mn VI 55 8 03 Mercury . H<* ii 200 13 60 Nickel N? VI 58 8 Nitrogen .... N v 14 Oxygen o ii 16 Palladium . Pd IV 106 5 11 40 Phosphorus ..." p v 31 1 840 Platinum Pt IV 197 4 21 15 K I 39 .865 Rhodium. ... Rh VI 104 12 1 Selenium Se VI 79 4 28 Silicon Si IV 28 5 2 49 Silver Ag I 108 10.53 Sodium. . Na I 23 9722 Strontium Sr 11 87 5 2 542 Sulphur. 3 VI 32 2 07 Tellurium Te VI 128 6.180 Tin . Sn IV 118 Titanium Ti IV 50 Tungsten W VI 184 Uranium Ur VI 120 18.4 Vanadium V v 51 2 5.5 Zinc Zn II 65 7 13 HEAT. 36 GENERATION OF HEAT. The generation of heat by chemical combination is explained by the fact that the resulting compounds pos- sess less energy than the constituent elements before they unite or combine. The difference of energy before and after combination appears in the form of heat, elec- tricity, etc. By the same token heat is absorbed during the decomposition of chemical compounds. MEASURE OF AFFINITY. The amount of heat or other form of energy devel- oped during a chemical change is a measure for the chemical work done or the amount of affinity displayed during the change. TOTAL HEAT DEVELOPED. The total amount of heat or energy developed dur- ing a chemical change depends solely upon the initial and final condition of the participating bodies (the initial or final condition of the system), and not on any intermedi- ate conditions. In other words, the heat developed dur- ing a chemical change is the same whether the change takes place in one operation or in two or more separate processes. MAXIMUM PRINCIPLE. Of all chemical change which may take place within a system of bodies, without the interference of outside energy, that change will take place which causes the greatest development of heat, as a general rule. According to the more modern conceptions it is held that that change will take place which will cause the greatest dissipation of energy, or by which the entropy of the system will suffer the greatest increase, or by which the greatest amount of energy will be dissipated. (For definitions of entropy see Chapters VII and VIII.) EXPRESSIONS FOR HEAT DEVELOPED. The amount of heat, expressed in units, developed or absorbed during a chemical process may be conveniently used in connection with the chemical symbols. Thus the formula Pb + 2I=PbI 2 + 7.1400 U signifies that 207 parts of lead combine with 254 parts of iodine to form 461 parts of iodide of lead, and develop thereby 7.1400 units of heat. 36 MECHANICAL REFRIGERATION. HEAT OF COMBINATION OF SUBSTANCES WITH OXYGEN. Substances. Product. Units of Heat Evolved. By 1 Ib. of Substance. By 1 Ib. of Oxygen. By 1 Atom of Substance in Pounds. Hydrogen H 2 O CO 2 SO 2 P20 5 Zn. F 3 T CiiO CO, CuO 60,986 14,220 3,996 10,345 2,394 2,848 1,085 4,325 561 7,623 5,332 3,996 8,017 9,702 7,475 4,309 60,986 170,640 127,872 320,683 156,610 159,466 68,947 121,111 32,947 Wood charcoal Sulphate, native. . . Phosphorus(y el low) Zinc . . Iron Copper Carbonic oxide Cuprous oxide COMBUSTION. Combustion is the rapid combination of combustible material (fuel) with oxygen. SPONTANEOUS COMBUSTION. In order to start the combustion of a combustible body it is generally necessary to elevate its temperature or to bring it in contact with a burning body. In other words, it must be ignited. If a body undergoes com- bustion without ignition it is a case of spontaneous combustion ; and if combustion takes place without the appearance of a flame or light it is called slow combustion. INFLAMMABLE BODIES. Bodies which are able to undergo combustion as with the appearance of a flame are called inflammable. EXPLOSIVE BODIES. If combustion of a body takes place at once or sim- ultaneously throughout its whole mass, an explosion generally takes place, especially if the body is confined in a limited space and if the products of the combustion are of a gaseous nature. Therefore such bodies are called explosives. AIR REQUIRED IN COMBUSTION. . The volume of air consumed chemically in the com- bustion of fuel is expressed by the formula: A = 1,52 (C+ 3H .40) A = volume of air as at 62 F., and under one atmos- phere of pressure, in cubic feet per pound of fuel A'= weight of air as at 62 F. per pound of fuel. C = percentage of constituent carbon. H= percentage of constituent hydrogen. O percentage of constituent oxygen. HEAT. 87 The weight of the air thus found by volume is equal to the volume divided by 13.14. Or it is found directly by the formula: In these formulae the heat evolved by the combus- tion of the sulphur constituent is not noticed, as it is trifling in proportion. GASEOUS PRODUCTS. The volume of the volatile or gaseous products of the complete combustion of one pound of a fuel, as at 62 F., at atmospheric pressure, is, by formula: F=1.52C+5.52B" The weight of the gaseous products is, by formula: V= volume of gaseous products, in cubic feet. tc = weight of gaseous products, in pounds. C = percentage of constituent carbon. H = percentage of constituent hydrogen. The volume at any other temperature is found by tfce formula for expansion of gases, given elsewhere. The proportion of free or unconsumed air usual y present in the gaseous products is determined by mult I.- plying the percentage of oxygen, found by analysis, by 4.3*. The product is the percentage of free air in parts of tf e whole mixture. HEAT GENERATED. The heat generated by combustion is as follows: Carbon .................. ...... 14,500 heat units per pound Hydrogen ...................... 62,000 Sulphur ........................ 4,000 The heating power of fuels containing carbon hydrogen is approximately expressed by the formula: in which h is the total heat of combustion. The evaporative efficiency for one pound of fuel is - e = . 15(0+4.29 JET) r ' e = 4 e= weight of water evaporable from and at 212, ! n pounds, per pound of fuel. The maximum temperature of combustion of carbc n is about 5,000 F.; and that of hydrogen is about 5,80(P If. 38 MECHANICAL REFRIGERATION. HEAT OF COMBUSTION OF FUELS. Total Equivalent Heat of Evaporative Fuel. Air Chemically Consumed per Pound of Fuel. Combus- tion of One Power, from and at 212 F., Water Pound of per Pound Fuel. of Fuel. Pounds. Cub. Ft. at 62" F. Units. Pounds. Coal of average compo- 1 sition f 10.7 140 14,700 15.22 !oke 10.81 8 85 142 116 13,548 13 108 14.02 13 67 Lignite A.sphalte 11.85 156 17,040 17.64 Wood desiccated . 6 09 80 10 974 11 36 fVbod, 25 per cent mois- 1 ture . ) 4.57 60 7,951 8.20 Vood charcoal, desic- ( cated .. ) 9.51 125 13,006 13.46 t'eat, desiccated 7.52 99 12279 12 71 1'eat, 30 per cent mois- 1 ture j 5.24 69 8,260 9.53 Peat charcoal, desic- 1 cated j 9.9 130 12,325 12.76 fitraw 4 26 56 8 144 8 43 Petroleum.. ...... 14 33 188 20 411 21 13 Petroleum oils 17.93 235 27 531 28 50 Coal gas, percubic foot I 630 .70 COAL. Coal consists mainly of carbon, which varies from 50 per cent to 80 per cent, by weight, of the fuel. Lignite or brown coal contains from 56 to 76 per cent of carbon. The average composition of coal is, say, 80 per cent of carbon, 5 per cent of hydrogen, 1^ per cent of sulphur, 1 per cent of nitrogen, 8 per cent of oxygen, and 4 per cent of ash. The fixed carbon or coke averages 61 per cent. The average specific gravity is 1.279; average weight of a solid cubic foot, 80 pounds; and of a cubic foot heaped, 50 pounds; average bulk of one ton heaped,' 44% cubic feet; equivalent evaporative efficiency, 15.40 pounds of water per pound of coal, from and at 212 F. Bituminous coals hold from 6 per cent to 10 per cent of water hygroscopically; Welsh coals from % per cent to 2% per cent. COKE. Coke contains from 85 to 97% per cent of carbon; from % to 2 per cent of sulphur, and from 1% to 14% per cent of ash. The average composition may be taken as 93% per cent of carbon, 1% per cent of sulphur, 5% per cent of ash. It weighs from 40 pounds to 50 pounds per cubic foot solid, and about 30 pounds broken and heaped. The volume of one ton heaped is from 70 to 80 cubic HEAT. 39 feet; average, 75 cubic feet. Coke is capable of absorb- ing from 15 to 20 per cent of moisture. There is or- dinarily from 5 per cent to 10 per cent of hygrometric moisture in coke. LIGNITE. Lignite or brown coal consists chiefly of carbon, oxy- gen and nitrogen; averaging in perfect lignite, 69 per cent of carbon, 5 per cent of hydrogen, 20 per cent of oxygen and nitrogen, and 6 per cent of ash. The weight is about 80 pounds per cubic foot. Imperfect lignite weighs about 72 pounds per cubic foot. CHIMNEY AND GRATE. The quantity of good coal, C,in pounds, that may be consumed per hour with a chimney having the height, JT, above the grate bars, a sectional area, A, in squai t feet at the top, may be expressed by the formula and the total area of fire grate G in square feet 1071 HEAT BY MECHANICAL MEANS. Mechanical work is also a source of heat, and in nearly all cases where work is expended, the appearance of an equivalent amount of heat is observed. The heat due to friction, percussion, etc., is an example of this kind, as also is the heat generated by the compression of gases and vapors (see Thermodynamics). The height of chimney for a given total grate area, the diameter at the top being equal to one-thirtieth of the height, is , Ja The side of a square chimney equal in sectional area to a given round chimney is equal to the product of tbe diameter by 0.886; the equivalent fraction of the height for the side of a square chimney is one-thirty-fourth. Conversely, the diameter of a round chimney equal in sectional area to a given square chimney is equal to the product of the side of the square by 1.13. When the top diameter of the chimney is one-thir- tieth of the height a good proportion the quantity of coal that may be consumed per hour is expressed by the formula c-.oi4.ar 2 - 5 40 MECHANICAL REFRIGERATION. CHAPTER V. FLUIDS; GASES; VAPORS. FLUIDS IN GENERAL. Fluids may be generally defined as bodies whose molecules are displaced by the slightest force, which property is also called fluidity, and it is possessed in a much larger degree by gases than by liquids. Gases are eminently compressible and expansible, while liquids are so but in a slight degree. VISCOSITY. The property of liquid to drag adjacent particles a ong with it is called viscosity (Internal Friction}. PASCAL'S LAW. Pressure exerted anywhere upon a liquid is trans- n itted undiminished in all directions and acts with the same force on all equal surfaces in a direction at right angles to those surfaces. BUOYANCY OF LIQUIDS. The pressure which the upper layer of a liquid exerts on the lower layers, is consequently also exerted in an upward direction, causing what is termed the buoyancy oHiquids. It is on account of the buoyancy of liquids tfhat a body weighed under liquid loses a part of its weight, equal to the weight of the displaced liquid ( Archimedian principle). SPECIFIC GRAVITY DETERMINATION. By ascertaining the loss in weight of a body immersed underwater its volume may be readily ascertained, it being equal to the volume of water corresponding to the lost weight. . This principle is used to determine the specific gravities of bodies in various ways; for instance, for solid bodies, by dividing their weight in air by the loss of weight which they sustain when weighed under water. HYDROMETERS. From among the instruments frequently used to ascertain the specific gravity of liquids, and by inference their strength, we mention those called hydrometers as based on the Archimedian principle. They are generally made of a weighted body (usually of glass), having a thinner stem at the upper end provided with a scale di- vided in degrees. The degrees may be arbitrary or show specific gravities or the strength of some particular liquid FLUIDS; GASES; VAPORS. 41 or solution in per cents; in the latter case the instru- ment is called Saccharometer, Salome ter, Alcoholometer, Acidometer, Alkalimeter, etc., according to the liquid it is designed to test. Hydrometers for different liquids or purposes, provided they cover the same range of specific gravities, may be used for either liquid when the relation their degrees bear to each other is known. For some of t he more current hydrometers, these relations are shown i a the following table : 7 ABLE SHOWING SPECIFIC GRAVITY CORRESPONDING TO DEGREES, TWADDLE, BEAUME AND BECK, FOR LIQUIDS HEAVIER THAN WATER. Numoer ofii Degrees. Corresponding Sp. Gr. Number of Degrees. Corresponding Sp. Gr. Twaddle Beaume. Beck. Twaddle Beaume. Beck. 1.000 1.000 1.000 21 1.105 1.166 1.1409 1 1.005 1.007 1,0059 22 1.110 1.176 1.1486 2 1.010 1.014 1.0119 23 1.115 1.185 1.1565 3 1.015 1.020 1.0180 24 1.120 1.195 1.1644 4 1.020 1.028 1.0241 25 1.125 1.205 1.1724 5 1.025 1.034 1.0303 26 1.130 1.215 1.1806 6 1.030 1.041 1.0366 27 1.135 1.225 1.1888 7 1.035 1.049 1.0429 28 1.140 1.235 1.1972 8 1.040 1.057 1.0494 29 1.145 1245 1.2057 9 1.045 1.064 1.0559 30 1.150 1.256 1.2143 10 1.050 1.072 1.0625 32 1.160 1.278 1.2319 11 1.055 1.080 1.0692 34 1.170 1.300 1.2500 12 1.060 1.088 1.0759 36 1.180 1.324 1.2(580 13 1.065 1.096 1.0828 38 1.190 1.349 1.2879 14 1.070 .104 1.0897 40 1.200 1.375 1.3077 15 1.075 .113 1.0968 45 1.225 1.442 1.3600 16 1.080 .121 1.1039 50 1.250 1.515 1.4167 17 1.085 .130 1.1111 55 1.275 1.596 1.4783 18 1.090 .138 1.1184 60 1.300 1.690 1 5454 19 1.095 .147 1.1258 65 1.325 1.793 1.6190 20 1.100 .157 1.1333 70 1.350 1.909 1.7000 There is a slight difference between the indications of the Reaume scale in different countries. The manufacturing chem- ists of the United States have adopted the following formula for converting the Beaume degrees into specific gravity: Specific gravity which gives specific weight slightly higher than those in the fore- going table. (See also table in Appendix.) PRESSURE OF LIQUIDS. The pressure exerted by a column of liquid at its bottom or base is proportional to the vertical height of the column of liquid, its specific gravity and to the area of the bottom, and independent of the shape or thickness of the column of liquid. 42 MECHANICAL REFRIGERATION. WATER PRESSURE. The pressure in pounds, P, of a column of water h feet high is P = .4335 h per square inch, and P = 62.425 h per square foot. SURFACE TENSION OF LIQUIDS. The layer of a liquid which separates the same from a gas or vacuum has a greater cohesion than any other layer of the liquid, owing to the fact that the attraction exerted on this layer by the interior of the liquid is not counteracted by any attraction on the outside. The sur- face is, as it were, stretched over by an elastic skin which exerts a pressure on the interior, which pressure is termed surface tension. It increases with the co- hesion of the liquid. VELOCITY OF FLOW OF LIQUIDS. The velocity with which a liquid flows through an opening depends only on the height of the liquid above the orifice and is independent of the density of the liquid. The velocity, v, in feet per second is expressed by the for- mula V= V 2 g h = 8 V ft g being the acceleration per second due to gravity, and h the depth of the orifice below the surface, both expressed in feet. QUANTITY OF FLOW. The quantity of a liquid, say water, discharged through an opening depends on the ar/"* of the opening, A (in square feet), and also on the shap etc., of the ori- fice. If the orifice is a hole in the thin all of a vessel, the quantity, E (in cubic feet), discharged A s expressed by E = bA V h A short cylindrical appendix to the opening woulc increase the discharge to E = 6.56 A V 2 h. and an appendix having the best form of a conic frus- trum will nearly discharge the theoretical amount .E 8 A V It FLUIDS; GASES; VAPORS. 43 FLOW OF WATER IN PIPES. The mean velocity, v, of water in a cast iron pipe of the length, Z, and the diameter, d, under the head, ft, isn v 48 Z The velocity is affected by the surface of pipe, the viscosity or interior friction of the liquid (hydrauL'c friction). QUANTITY OF FLOW THROUGH PIPES. Dawning's formula for the quantity, J7, in cubic feet of water discharged by channel or pipe under the head, ft, in feet is as follows: prs. 100 a -%/~y~ I being the length of pipe in feet; a, sectional area o current in square feet; c, wetted perimeter in feet. D = == hydraulic mean depth. c HEAD OF WATE&. The head, ft, approximately required to move wat< t with a velocity of 180 feet per minute through a clean cat V iron pipe, having a diameter D inches and the lengt I in feet, is WATER POWER. The theoretical effect of water power -expressed iu footpounds per minute, is equal to the weight of the water falling per minute, multiplied by the height through which the water falls. Divided by 33,000, it expresses horse powers. The practical effect depends on the efficiency of the motor (water wheel, turbine, engine, etc.). The power required to lift water is calcu- lated in the same manner. HYDROSTATICS AND DYNAMICS. The science which treats of the condition of liquids while at rest is called hydrostatics, and that which treats of the motion of liquids is called hydrodynamics. 44 MECHANICAL REFRIGERATION. CONSTITUTION OF GASES. In a general way the term gas has been defined in the foregoing. Speaking more specifically, a gas is a body in which the distance between the constituent atoms or molecules is so great that the dimensions of the mole- cules themselves may be neglected in comparison there- with. The atoms or molecules in a gas are constantly vibrating to and fro, and the average momentum or energy of this motion represents the temperature of the gas. The vehemence or force with which the atoms or molecules impinge on the walls of a surrounding vessel in consequence of this motion represents the pressure of the gas. PRESSURE AND TEMPERATURE. In accordance with the foregoing definition the pressure, volume and temperature of a gas are in direct connection, which is expressed by the laws of Boyle and St. Charles. BOYLE'S LAW. The law of Boyle or of Mariotte asserts that the vol- ume of a body of a perfect gas is inversely proportional to its pressure, density or elastic force, if its temperature remains the same. ST. CHARLES LAW. If a gaseous body is heated while the pressure re- mains constant, its volume increases proportionally with the temperature. The increase of volume for every degree F. is equal to ^ of its volume at 32 F. UNIT OF PRESSURE. The general unit of pressure is the pressure of the atmosphere per square inch, which is equal to that of a column of water of about thirty feet, or that of a col- umn of mercury of about thirty inches, and also equiva- lent to a pressure of 14.7 pounds in round numbers fif- teen pounds per square inch. ABSOLUTE AND GAUGE PRESSURE. The pressure gauges in general use indicate pressure in pounds above the atmospheric pressure; it is called gauge pressure. To convert gauge pressure into abso- lute pressure 14.7 has to be added to the former. Smaller pressures are designated by the number of inches of mercury which they will sustain, or, after the FLUIDS; GASES; VAPORS. 45 French system, by millimeters of mercury, which are compared in the following table for ordinary pressures of the surrounding atmosphere. COMPARISON OF THE BRITISH AND METRICAL BAROMETERS. Inches. Millimeters. Inches, Millimeters. Inches. Millimeters. 27.00 685.788 38.40 721.347 29.80 756.906 27.10 688.338 38.50 723.887 29.90 759.446 27.20 690.867 28-60 736.437 30.00 761.986 27.30 693.40? 28.70 728.967 30.10 764.536 "27.40 695.947 28.80 731.507 30.20 767.066 87.50 698.487 28.90 734. 047 30.30 769.606 W.60 701,037 39.00 736.587 30.40 773.146 67.70 703.567 39.10 739.127 30.50 774.686 {7.80 706.107 29.20 741.667 30.60 777.226 27.90 708.647 39.30 744.306 30.70 779. 766 38.00 711.187 39.40 746.746 30.80 783.306 28.10 713.737 29.50 749.280 30.90 784.846 38.30 716.267 29.60 751.836 28.30 718.807 29.70 754.366 ACTION OF VACUUM. The pressure of the atmosphere is the cause of the casing of water by suction pumps, the air in the pumps being removed by the movement of the piston, and its space occupied by water forced up by the pressure of the outside atmosphere. For the same reason such a pump cannot lift water higher than thirty- two feet, a column of water of this height exerting nearly the same pressure as the atmosphere at the earth's surface. For the same reason the mercury in a barometer (or glass tube from Tihich the air is withdrawn) stands about twenty-nine iftches high, varying with the pressureof the atmosphere, between twenty-seven and thirty inches at the earth's surface, but decreases with the height above the earth at the rate of 0.1 inch for 84 feet. MANOMETERS GAUGES. The instruments for measuring higher gaseous press- tires are usually called manometers or gauges. WEIGHT OF GASES. The weight of gases is determined by weighing a glass balloon filled with the same, and by subtracting from this weight that of balloon after the same has been evacuated by means of an air pump. One hundred cubic inches of air weighs 31 grains at a pressure of the atmos- phere of 30 inches, and at a temperature of 60 F.; there- fore the density of air is 0.001293 or T f ff that of water. 46 MECHANICAL REFRIGERATION. One hundred cubic inches of hydrogen, the lightest of the common gases weighs 2.14 grains. MIXTURE OF GASES. Two or more gases present in vessels, communicat- ing with each other, mix readily, and each portion of the mixture contains the different gases in the same pro- portion. Mixtures of gases follow the same laws as simple gases. DALTON'S LAW. The pressure exerted on the interior walls of a vessel containing a mixture of gases is equal to the sum of the pressures which would be exerted if each of the gases occupied the vessel itself alone. BUOYANCY OF GASES. The Archimedian principle applies also for gases hence a body lighter than air will ascend (air balloons smoke, etc.). LIQUEFACTION OF GASES. If sufficient pressure be applied to a gas and the tern perature is sufficiently lowered all gases can be com pressed so as to assume the liquid state. HEAT OF COMPRESSION. When gases or vapors are being compressed, the energy or work spent to accomplish the compression appears in the form of heat. CRITICAL TEMPERATURE. There appears to exist for each gas a temperature above which it cannot .be liquefied, no matter what amount of pressure is used. It is called the critical tem- perature. Below this temperature all gases or vapors may be liquefied if sufficient pressure is used. CRITICAL PRESSURE. The pressure which causes liquefaction of a gas at or as near below the critical temperature as possible, is called the critical pressure. Between these two tempera^ tures that is, in the neighborhood of the critical point- the transition from one state to another is unrecog- nizable. CRITICAL VOLUME. The critical volume of a gas is its volume at the critical point, measured with its volume at the freezing FLUIDS; GASES; VAPORS. 47 point, under the pressure of an atmosphere as unit. The critical temperature, pressure and volume are fre- quently referred to as critical data. TABLE OF CRITICAL DATA. Substance. Critical Press- ure in Atmos- pheres. Critical Tem- perature, Degrees C. Critical Volume. Ammonia, 115 130 Aethylen 51 10 00560 Alcohol 67 235 0.00713 76-4 231 5 0110 Aethylic ether \cetateofaethyl 37.5 42.2 200 240 0.01344 01222 60 293 00981 JJisulphide of carbon. . JJutyrate of amyl . 77.8 23 8 275 332 0.0096 03809 ( /arbonic acid 77 31 0066 31.8 347 2 0258 20.3 240 Nitrous oxide (N 2 O)... 75 50 35.4 118 0.00480 I'ropylic alcohol . ... 63.3 256 00968 Sulphurous acid 79 155.4 Toluol 40 320.8 02138 W'JitGT 195 358 00187 SPECIFIC HEAT OF GASES. A gas may be heated while its volume is kept con- stant and also while its pressure remains constant. In the former case the pressure increases and in the latter I he volume increases. Therefore we make a distinction I etween specific heat of gases at a constant volume or t a constant pressure. In the former case the heat ^dded is only used to increase the momentum of the molecules, while in the latter case an additional amount of heat is required to do the work of expanding the gas ygainst the pressure of the atmosphere. The specific heat of all permanent gases for equal volumes at con- stant pressure is nearly the same and about 0.2374 water taken as unity. TABLE OF SPECIFIC HEAT OF GASES. For Equal Weights. (Water = 1.) At Constant Pressure. At Constant Volume. A ir . . . .2377 .2164 .2479 3.4046 .5929 .2440 .2182 .1688 .1714 .1768 2.4096 .4683 .1740 .1559 .3050 .3700 .1246 Carbonic acid (CO?) " oxide (CO) Light carbureted hydrogen Dxvsen Siteam saturated ( (team gas .. .4750 .1553 Sulphurous acid 48 MECHANICAL REFRIGERATION. ISOTHERMAL CHANGES. A gas is said to be expanded or compressed isother- mally when its temperature remains constant during expansion or compression, and an isothermal curve or line represents graphically the relations of pressure and volume under such conditions. ADIABATIC CHANGES. As gas is said to be expanded or compressed adiabat- ically when no heat is added or abstracted from the same during expansion or compression, an adiabatic line or curve represents graphically the relations of pressure and volume under such conditions. FREE EXPANSION. When gas expands against an external pressure much less than its own, the expansion is said to be free. The refrigeration due to the work done by such expansion may be used to liquefy air. (See Linde's method.) LATENT HEAT OF EXPANSION. When a gas expands while doing work, such propelling a piston, an amount of heat equivalent to tbs work done becomes latent or disappears. It is called the latent heat of expansion. VOLUME AND PRESSURE. The relations of volume pressure and temperatu 'e of gases are embodied in the following formulae in whic h V stands for the initial volume of a gas at the initial tem- perature t and the initial pressure p. F 1 , t l and r* stand for the corresponding final volume, temperature and pressure. For different temperatures yi = V 1 4-461 For different pressures F* = Fi P 1 For different temperature and pressure F i = F P(*i+*61) pM* +461) If the initial temperature is 60 F. and the initial pressure that of the atmosphere, the final pressure may be found after the formula FLUIDS; GASES; VAPORS. 49 35.38 V* If the Yolume is constant 35.58 If the temperatures in above formula are expressed degrees Fahrenheit above absolute zero, the figure 461 is to be omitted. PERFECT GAS. The above rules and formulae apply, strictly speak- ing, only to a perfect or ideal gas, that is a gas in which the dimensions of the molecules may be neglected as re- gards the distance between them. Therefore when a gas approaches the state of a vapor, these laws do no more hold good. ABSOLUTE ZERO AGAIN. The expansion of a perfect gas under constant pressure being ^3 of its volume at 32 F. (freezing point), it follows that if a perfect gas be cooled down to a temperature of 493 below freezing, or 461 below zero Fahrenheit, its volume will become zero. Hence this point is adopted as the absolute zero of temperature. (See also former paragraph on this subject.) VELOCITY OF SOUND. The velocity, v, of sound in gases is expressed by the formula In which formula g is the force of gravity, h the barometric height, d the density of mercury, d the density of the gas, t its temperature, c its specific heat at constant pressure, and c, its specific heat at con- g stant volume. Hence the quotient, , for a certain gas can be determined by the velocity of sound in the same. FRICTION OF GAS IN PIPES. The loss of pressure in pounds, P, sustained by gas in traveling through a pipe having the diameter d in inches, for a distance of I feet, and having a velocity of n feet, is P = 0.00936 ^-L d 50 MECHANICAL REFRIGERATION ABSORPTION OF GASES. Gases are absorbed by liquids ; the quantities of gases so absorbed depend on the nature of the gas and liquid, and generally increase with the pressure and decrease with the temperature. During the absorption of gas by a liquid a definite amount of heat is generated, which heat is again absorbed when the gas is driven from the liquid by increase of temperature or decrease of pressure. Solids, especially porous substances, also absorb gases. Thus charcoal absorbs ninety times its own volume of ammonia gas. VAPORS. As long as a volatile substance is above its critical temperature it is called a gas, and if below that it is called a vapor. This definition, although the most definite is not the most popular one. Frequently a vapor is defined as rep- resenting that gaseous condition at which a substance has the maximum density for that temperature or pressure. Generally gaseous bodies are called vapors when they are near the point of their maximum density, and a distinction is made between saturated vapor, superheated vapor and wet vapor. SATURATED. VAPOR. A vapor is saturated when it is still in contact with some of its liquid; vapors in the saturated state are at their maximum density for that temperature. Com- pression of a saturated vapor, without change of tem- perature, produces a proportional amount of liquefaction. DRY OR SUPERHEATED VAPOR. Vapors which are not saturated are also called dry or superheated vapcrs, and behave like permanent gases. WET VAPOR. A saturated vapor which holds in suspension parti- cles of its liquid is called wet or moist vapor. TENSION OF VAPORS. . Like gases, vapors have a certain elastic force, by virtue of which they exert a certain pressure on sur- rounding surfaces. This elastic force varies with the nature of the liquid and the temperature, and is also called the tension of the vapor. FLUIDS; GASES; VAPORS, 51 VAPORIZATION. A liquid exposed to the atmosphere or to a vacuum forms vapors until the space above the liquid contains vapor of the maximum density for the temperature. EBULLITION. If the temperature is high enough the vaporization takes place throughout the liquid by the rapid produc- tion of bubbles of vapor. This is called ebullition, and the temperature at which it takes place is a constant one for one and the same liquid under a given pressure. BOILING POINT. The temperature at which ebullition of a liquid takes place is called its boiling point, for the pressure then ob- taining. When no special pressure is mentioned we understand by boiling point that temperature at which liquids boil under the pressure of the atmosphere. DIFFERENT BOILING POINTS. The boiling point varies with the nature of the liquid, and always increases with the pressure. It is not affected by the temperature of the source of heat, the temperature of the liquid remaining constant as long as ebullition takes place. The heat which is imparted to a boiling liquid, but which does not show itself by an increase of temperature, is called the latent heat of vaporization. ELEVATION OF BOILING POINT. Substances held in solution by liquids raise their boiling point. Thus a saturated solution of common salt boils at 214 and one of chloride of calcium at 370. The boiling point of pure water may also be raised above the boiling point; for water free from gases to over 260 without showing signs of boiling. This retardation of boiling sometimes takes place in boilers, and may cause explosions, if not guarded against by a timely motion produced in the water. LATENT HEAT OF VAPORIZATION". The heat which becomes latent during the process of volatilization is composed of two distinct parts. The one part is absorbed while doing the work of disintegrating the molecular structure while doing INTERNAL WORK, as it is termed. The other part of heat which becomes latent is 52 MECHANICAL REFRIGERATION. absorbed while doing the work of expansion against the pressure of the atmosphere, and is called the EXTERNAL WORK. In a liquid evaporized in vacuum, in which case no pressure is to be overcome, the external work becomes zero, and only heat is absorbed to do the internal work of vaporization (free expansion). REFRIGERATING EFFECTS. If liquids possess a boiling point below the tempera- ture of the atmosphere the latent heat of vaporization is drawn from its immediate surrounding object, causing a reduction of temperature, i. e., refrigeration. LIQUEFACTION OF VAPORS. When vapors pass from the aeriform into the liquid state, that is, when they are liquefied, the heat which bo- came latent during evaporation appears again, and must 1 ^e removed by cooling. Vapors of liquids the boiling point of which is above the ordinary temperature can be liquefied at the ordinary temperature without additional pressure (distilling condensation). Permanent gases require addi- tional pressure, and in some cases considerable refrigera- tion, to become liquefied (compression of gases). DALTON'S LAW FOR VAPORS. The tension and consequently the amount of vapor of a certain substance which saturates a given space is the same for tr^e same temperature, whether this space contains a gas or is a vacuum. The tension of the mix- ture of a gas and a vapor is equal to the sum of the ten- sions which each would possess if it occupied the same space alone. VAPORS FROM MIXED LIQUIDS. The tension of vapor from mixed liquids (which have no chemical .or solvent action on each other) is nearly equal to the sum of tension of the vapor of the two separate liquids. SUBLIMATION. The change of a solid to the vaporous state without first passing through the liquid state is called sublimation (camphor, ice). DISSOCIATION. The term dissociation is used to denote the separa- tion of a chemical compound into its constituent parts, especially if the separation is brought about by subject- ing the compound to a high temperature. MOLECULAR DYNAMICS. 63 CHAPTER VI. MOLECULAR DYNAMICS. MOLECULAR KINETICS. It has already been stated that the laws of Boyle and St. Charles are in accordance with the molecular theory, by the consequent development of which a num- ber of other relations have been established which are of the utmost importance in all discussions of energy, es- pecially those of thermodynamical nature. Applied to gases, this theory means that the rectilinear progressive motion of the molecules, which constitutes the body of a gas, represents by its kinetic energy the temperature of a gas, and by the number of impacts of its molecules against the wall of the vessel containing the gas, its pressure. DENSITY OF GASES. If m represents the mass of a molecule and u the average velocity of its rectilinear progressive motion, the kinetic energy, E (ie., the temperature), of the molecule is expressed by If the unit of volume, say a cubic foot of a gas, con- tains N molecules of the mass, m, the density of the gas, p, is p = m N PRESSURE OF GASES. The number of molecules which collide with the inte- rior surf aces of a cube of above size is equal to JV w, and hence the number which collide with one of the interior surfaces of the cube (one foot square): Nu 6 The number of impacts multiplied by the momentum of the impact of each molecule, 2 m u, yields the pressure: AVOGADRO'S LAW. At the same temperature and pressure equal volumes of different gases contain the same number of molecules. Hence the molecular weights of gases are proportional to their densities. 54 MECHANICAL REFRIGERATION. MOLECULAR VELOCITY. The average velocity of the molecules, w, is accord- ingly For hydrogen we find u = 1,842 meters per second. If M is the molecular weight of a gas referred to hydrogen as unit (p being proportional to M ) the aver- age velocity of the molecules is expressed by u = 1,842 * I meters per second. \ M The average distance, -L, which a molecule travels in rec- tilinear direction before it meets another molecule is ex- pressed by the formula 7- * 3 " 1.41;rs 2 in which A is the average distance of the molecules, and therefore A 3 the size of the cube which contains one molecule on an average. L accordingly has been found to be for hydrogen 0.000185 millimeter; for carbonic acid, 0.000068 mm.; for ammonia 0.000074 mm. INTERNAL FRICTION OF GASES. The internal friction, ??, of a gas is expressed by the equation 12 it The velocity of sound in different gases is inversely proportional to the square root of their molecular weights (see page 49). TOTAL HEAT ENERGY OF MOLECULES. The total heat energy of a body is composed of the energy due to the progressive motion of its molecules, and the interior energy which is represented by possible rotatory motions of the molecules, or by motions of the atoms composing the molecule. In gases, and probably also in liquids and solid bodies, the former portion of energy is proportional to the absolute temperature, so that at the absolute zero 461 F. the progressive mo- tion of the atoms would cease. MOLECULAR DYNAMICS. 55 LAW OF GAY LUSSAC. Since chemical combinations between different ele- ments take place in the proportion of their molecular weights, and since equal volumes of gases contain equal numbers of molecules, the chemical combination between gaseous elements must take place by equal volumes or their rational multiples, and the volume of the combina- tion if gaseous bears equally a simple numerical relation to that of the elements. EXPANSION OF GASES. Since the same number of molecules of different gases occupy the same volume at equal temperatures and pressure, the expansion by heat of all gasec under con- stant pressure must be the same, and for perfect gases it is the same for all temperatures, being equal to the ^3 part of the volume of a gas at the freezing point and at the pressure of one atmosphere. This is tantamount to saying that the volume of gas under constant pressure is proportional to its absolute temperature, T 461 -j- * EQUATION FOB PERFECT GASES. The increase of pressure of a gas heated at constant volume being likewise proportional to the absolute tem- perature and equal to -^ of its volume at the freezing point, the product of pressure and volume, p v, must be likewise, and hence it can be expressed by the equation p v = E T in which It is a constant factor, depending only upon the units used. T standing for absolute temperature, it may be written T 493 493 p a and u standing for pressure and volume at the tem- perature of 32 F., both being unit. GENERAL EQUATION FOR GASES AND LIQUIDS. This formula answers for a perfect gas in which the dimension of the molecules and their mutual attraction disappear in comparison with their volume and the expansive force due to the temperature. If the dimen- sions and mutual attraction are taken into consideration, the formula according to Van der Waals reads: 56 MECHANICAL REFRIGERATION. In this formula the signs have the same meaning as in the former equation, except the two constants a and 6, which differ with the nature of the gas ^; atoning for the influence of the molecular attraction which may be derived from the deviation of the gas from Boyle's law; b stands for the influence of the volume of the molecule; it is equal to four times the volume of the molecules. Its value may be ascertained by inserting the value found for a into the formula of Van der Waals. How- ever, it is generally more convenient and of more prac- tical application to derive the values a and b from the critical data, as will be shown later on. The formula of Van der Waals answers not only for all gases, but for the liquid condition as well, as far as changes of volume, pressure and temperature are con- cerned, provided, however, that the changes take place homogeneously and that the molecular constitution of the substance is not altered during the change. CRITICAL CONDITION. If this formula is elaborated numerically as to vol- ume for given temperatures and pressures, we always obtain one real positive expression for volume except for pressures near the point of liquefaction at tempera- tures below the critical point. Here the formula does not apply on account of the so-called critical condition (partly gas and partly liquid) which the substance maintains at this stage. These conditions become readily apparent by an elaboration of the equation of Van der Waals, for if the equation which may also be written is developed after powers of v (p and v = unit), we obtain >) T\ a ab L V _|_ v =o This equation being a cubical one, it may be satisfied by three values, which may all be real or one of which may be real and the other two imaginary. Accordingly, we MOLECULAR DYNAMICS. 57 find for all' temperatures above the critical point for any given pressure only one value for volume ; except for temperatures below the critical point for certain values of p, i.e., for pressures near the point of lique- faction for that temperature, or nearing the boiling point for that pressure. At these stages the substance is under so-called critical conditions, and here we find three different values for v, one of which may stand for the volume of the substance in its gaseous form, another for its volume as a liquid, and the third for an inter- mediate volume CRITICAL DATA. When, on increasing temperature and pressure these three values for volume converge into one, that is, if the three real roots of the equation become equal, we have reached the critical volume, that is, that volume which corresponds to the critical pressure and to the critical temperature. At this, the critical point, the substance passes gradually and without showing a separation into liquid and gas, that is to say homogeneously, from the gaseous into the liquid state; there is no intermediate stage at this temperature between the volume of the liquid and the volume of the gas, as is the case at tem- peratures below the critical point and at pressures cor- responding to the boiling point. The values of temperature pressure and volume at which the three roots of the above equation become equal is found by the following considerations: If in a cubical equation of the form x a a x z -}-b x c = o the three roots become equal to each otl^er = x t the fol- lowing relations obtain : , Applying this to the above equation, which may also be written by inserting the signs, f-) The last equation may be rendered approximately by < ? 493 _ 8a 3 = 21 bit 0.000765 *= -*r~ The numerical values for a and b for any substance having been found by these formulae from the critical temperature and pressure, they may be inserted in the general equation of Van der Waals, which will then yield the relations of pressure and volume at different temper- atures, etc. MOLECULAR DYNAMICS. 50 UNIVERSAL EQUATION. If the volume, pressure and temperature of a gas are measured by fractions of the absolute data, in other words, if v = n g> and p = e it and T = m 5, the general equation may be written If the values for it, q> and 3- as found in the above, are inserted in this equation the same may be brought to the f orm This formula contains no terms dependent upon the nature of the substance, hence the equation establishing the relations between pressure, volume and temperature is the same for all substances, if volume, pressure and temperature are expressed in fractions of the critical data (provided v > 4 6). If v is smaller than 4 6 the formula may possibly give correct results, but when it does not such a result does not vitiate the admissibility of the theory in other re- spects, as Van der Waals has shown. OTHER MOLECULAR DIMENSIONS. In accordance with the foregoing the average space, Y, occupied by each molecule of a gas is expressed by 4 ' 32 X 273 it and the specific weight, w> of a gas (water at 39 F. = 1): M 22350 y M being the molecular weight in grams, and 22,350 c. c. the volume occupied by the same at 32 F., and at the pressure of one atmosphere. If the molecules are supposed to be of spherical form their diameter, s, is expressed by the formula s = 6 *J~Z~L r =8.5 Ly L being the average distance which a molecule travels, as stated above, viz. : L --- *! _ 60 MECHANICAL REFRIGERATION. ABSOLUTE BOILING POINT. The definition of the boiling point as given hereto- fore fits only for a certain pressure, but in accordance with the critical conditions we can define an absolute boiling point as the temperature at which a liquid will assume the aeriform state, no matter what the press- ure is, viz., the critical temperature. CAPILLARY ATTRACTION. Since capillary attraction (in consequence of which liquids rise above their surface in narrow tubes) and also the surface tension of liquids are both functions of the cohesion of liquids, and since the cohesion diminishes with the temperature, the capillary attraction must do likewise; and it has been shown that it becomes zero at the critical temperature or at the absolute boiling point. CRITICAL VOLUME. At the critical temperature the change from the liquid to the gaseous condition requires no interior work, and therefore the latent heat of vaporization at this temperature must be equal to zero. The volumes of a certain weight of liquid or vapor of a substance at the critical temperature must likewise be the same. GAS AND VAPOR. If, with Andrews, we confine the conception of vapor to a fluid below its critical point, and that of a gas to a fluid above its critical point, we can also define as vapor such aeriform fluids as may be compressed into a liquid by pressure alone without lowering temperature; and by the same token a gas is an aeriform fluid which cannot be compressed into a liquid by pressure alone without lowering the temperature. By liquefaction we designate the production of a liquid separated from the vapor by a visible surface. LIQUEFACTION OF GASES. After the significance of the critical temperature had been duly understood and appreciated it became also possible to liquefy the most refrangible gases by pressure when cooled down below their critical tempera- ture. A novel way for the liquefaction of such gases, more especially air, has been devised by Linde, and the process employed by him is so simple and successful that it will doubtless become of practical value in many re- spects, more especially also practical refrigeration. THERMODYNAMICS. 61 CHAPTER VII. THERMODYNAMICS. THERMODYNAMICS. Thermodynamics is the science which treats of heat in relation to other forms of energy, and more especially of the relations between heat and mechanical energy. FIRST LAW OF THERMODYNAMICS. This law is a special case of the general law express- ing the convertibility of different forms of energy into one another. The first law of thermodynamics asserts the equivalence of heat and work or mechanical energy, and states their numerical relation. Accordingly heat and work may be converted into each other at the rate of 778 foot-pounds for every unit of heat, and vice versa. SECOND LAW OF THERMODYNAMICS. The foregoing law holds good without any limitation as far as the conversion of work or mechanical energy into heat is concerned. It must be qualified, however, with respect to the conversion of heat into work. It amounts to this, that of a certain given amount of heat at a given temperature only a certain but well defined portion can be converted into work, while the remaining portion must remain unconverted as heat of a lower temperature. This outcome is a natural consequence of the condition that heat cannot be directly transferred from a colder to a warmer body. EQUIVALENT UNITS. In accordance with the first law, we can measure quantities of heat by the heat unit or by the unit of work (foot-pound) and we can also measure it by its equivalent in heat units as well as by the units of work. The figure designating the number of foot-pounds equivalent to the unit of heat (778), i. e., the mechanical equivalent of heat, is frequently referred to by the letter J. When quantities of work and heat are brought in juxtaposition in equations, etc., it is always understood that they are expressed by the same units, i. e. , in either heat or work units. SECOND LAW QUALIFIED. In a system in which the changes are only such of heat and such of mechanical energy (work), the appear- ance of a certain amount of work is always accompanied by the disappearance of an equivalent amount of heat, 62 MECHANICAL REFRIGERATION. and the appearance of a certain amount of heat is always accompanied by the expenditure of an equivalent amount of mechanical energy. From this, however, it must not be concluded that by withdrawing a certain amount of heat from a warmer body we can convert it into its equivalent amount of mechanical energy. This is only the case under exceptional conditions ; but when, as in. the case of practical requirements, the conversion of heat into work must be done by a continuous process it cannot be accomplished under conditions practically available. CONVERSION OF HEAT. The conversion of heat into mechanical work, and work into heat, takes place in many ways. Generally the change of volume or pressure brought about by heat changes mediates the conversion. The substance which is used to mediate the conversion is called the working medium or the working substance. MOLECULAR TRANSFER OF HEAT ENERGY. The manner in which heat is converted into mechan- ical work is readily understood on the basis of the molec- ular theory, when the working fluid is a gas, the pressure of which, due to its molecular energy (heat) is employed to propel a piston. The molecules of the gas by colliding with the piston impart a portion of their molecular energy to the piston, moving the same forward; at the same time the energy of the molecules grows less, and indeed the temperature of the gas decreases as the piston moves ahead. If the work done by the piston and the heat lost by the gas were measured in the same units, it would be found that they were practically alike (pre- supposing we employ a perfect gas, consisting of simple molecules, undergoing no internal changes). GAS EXPANDING INTO VACUUM. If there had been no pressure on the piston (and the piston supposed to have no weight) in the foregoing experiment, the piston would have been moved by the expanding gas, without doing work during the expansion, and hence the temperature of the gas, while expanding under such conditions (against a vacuum), remains con- stant and unchanged, at least practically so. HEAT ENERGY OF GAS MIXTURES. The same would happen if two vessels, containing the same or different gases at different pressures, are THERMODYNAMICS. 63 brought in communication ; no change of heat takes place, while the pressures equalize themselves. Hence, the heat energy of a gas is independent of its volume, and the energy of a mixture of gases is equal to the sum of the energy of its constituents. DISSIPATION OF ENERGY. Accordingly we may allow a gas under pressure to dilate in such a way as to do a certain amount of work at the expense of an equivalent amount of heat, and we may allow it to expand without doing work. In the latter case the availability of the gas to mediate a cer- tain amount of work has not been utilized, has been dis- sipated, as it were, since the original condition of the gas cannot be re-established again without the expendi- ture of outside energy. ADIABATIC CHANGES. In the former case, when the gas was allowed to ex- pand while doing work, the greatest possible amount of work obtainable is produced when the pressure of the piston is always kept iriflnitesimally less than that of the gas. If this is being done the original condition of the gas can be established by making the pressure on the piston only infinitesimally more than on the gas, when the gas will be compressed to its original volume and temperatuje (no heat having been added to or ab- stracted from the gas during the operation). Both the operations of expansion and compression of the gas as conducted (without addition of heat, etc.) are therefore adiabatic changes, they are both reversible changes, and neither of them involves any dissipation of heat or energy. In the one change we have converted heat energy into work, and in the other work into heat. ISOTHERMAL CHANGES. The expansion of the gas while propelling a piston may be allowed to proceed while the energy imparted to the piston is replaced by heat supplied to the expanding gas from without. In this case the expanding gas is kept at the same temperature, and therefore it is said that the expansion proceeds isothermically. This operation may also be reversed and work converted into heat by apply- ing the power gained by raising the piston, to push the piston back, and withdrawing the heat liberated by 64 MECHANICAL REFRIGERATION. the work of compression as fast as it appears, so that the gas is always at the same temperature. (Isothermic compression.) If, during expansion, the temperature of the gas is always only inflnitesimally smaller, and dur- ing compression infinitesimally greater than the out- side temperature, both operations are considered to be reversible, arid no dissipation of energy takes place dur- ing the performance of either of them. MAXIMUM CONVERSION. In conducting the operations in the foregoing (re- versible) manner we obtain the maximum yield of mutual conversion of work and heat obtainable by the expansion or compression of the gas in question. CONTINUOUS CONVERSION. While a body of gas may be used in the above way to convert a certain amount of heat into work, and vive versa, it would not answer for the continuous conversion of work into heat, for if the operation of work produc- tion is reversed we simply re-establish the original con- dition without having accomplished any outside change whatever. PASSAGE OF HEAT. The fact that heat cannot of itself pass from a colder to a warmer body is also in harmony with the molecular theory. The molecules of bodies having the same tem- perature possess also the same average, energy, and therefore cannot impart energy to one another; much less can energy of heat pass from a colder to a warmor body. The ability of heat to do work is due to its nat- ural tendency to pass from a warmer to a colder body, and therefore, other circumstances being equal, is di- rectly proportional to the difference of temperature be- tween the warmer and colder body. REQUIREMENTS FOR CONTINUOUS CONVERSION. As stated, for the practical conversion of heat into work, we need a working medium that is a substance of some kind which mediates the conversion. As the heat which is communicated to this medium for the purpose of doing work is never entirely available for this purpose, but a portion of the heat always remains as heat of a lower temperature (not available for mechanical work except when it can pass to a temperature still lower), it fol- lows as a matter of course and also of necessity, that when THERMODYNAMICS. 65 we desire to convert heat into work by a continuous pro- cess we need not only a working substance but also a warm body, a source of heat (boiler, generator, etc.), and a body of lower temperature, to which the heat not avail- able for work in the operation may be discharged. The latter device is generally called a refrigerator or con- denser; in the case of many heat engines it is the atmos- phere. The same requirements, only in a reversed order, obtain for the continuous conversion of work into heat, i. e.< when heat is to be transferred from a colder to a warmer body, the work expended compensating for the transfer (lifting heat). COMPONENTS OF HEAT CHANGES. The changes produced in a body by heat may be divided in several parts, viz., the elevation of tempera- ture, i e.,the increase of energy of the molecules, the change produced by overcoming the interior cohesion, and by rearranging the molecular constitution of the body, and the change required to do outside work, overcoming pressure. MAXIMUM CONTINUOUS CONVERSION OF HEAT. The question as to the maximum amount of work which can be obtained from a certain amount of heat by continuous conversion, and the maximum amount of heat which can be obtained by or lifted by a certain amount of work, is one of the most important in ther- modynamics. It has been solved with the same result in various ways, the following giving the outlines of one of them. CYCLE OF OPERATIONS. The contrivances which are required to perform the operations, by which through the aid of the working medium, etc., heat is continuously transformed into work, or work into heat, come under the general head of machines. A series of operations of the kind mentioned which are so arranged that the working substance returns periodically to its original condition is also called a cycle of operations. REVERSIBLE CYCLE. If a cycle of operations is conducted in such a manner that all the changes or operations can be carried out in the opposite direction the cycle is what is called a revers- ible cycle. Operations can generally be made revers- 66 MECHANICAL REFRIGERATION. ible, at least in theory, if the transfers of heat follow only infinitesimally small differences in temperature and the changes in volume take place under but infinites- imally small differences of pressure. Not all changes can be performed in a reversible manner, however. IDEAL CYCLE. For the continuous conversion of heat into work we require the performance of a cycle, so that the work- ing substance, which is generally not unlimited, may return periodically to its original condition, and may be used continuously over and over again. If at the same time the operations of the cycle are carried on re- versibly the conversion of heat into work takes place at the greatest possible rate. In other words, the maximum amount of work obtainable from a given amount of heat is realized if the working substance is passed through the operations of a reversible cycle. Practically we can only approach the conditions of a reversible cycle, for which reason it is also called an ideal cycle of operations. IDEAL CYCLES HAVE THE SAME EFFICIENCY. The proof that a cycle of reversible operations for the transformation of heat into work yields the greatest return of work for a given amount of heat, and vice verso, may be based on the axiom that no energy can be created, or on the fact that heat cannot pass from a colder to a warmer body. For if one cycle of reversible opera- tions would yield a greater amount of work for a certain amount of heat than another reversible cycle, the latter would also by reversing it require a lesser amount of work to produce that given amount of heat. Hence we could operate the first cycle to convert a given amount, C, of heat to produce a certain amount of work, B, and the second cycle, being operated in the reverse manner, would only need a portion of the workB, say J5 lt to reproduce the heat (7, which could be employed in the first cycle to again produce the work B. Therefore both devices or cycles co-operating in the manner indicated would during each co-operative performance create the work!? B , or rather, transfer an equivalent amount of heat from a colder to a warmer body, which is impossible. Hence both devices must operate with the same efficiency, and all reversible cycles devised for the mutual conversion of heat into work must, theoretically speaking, have the same efficiency, and the maximum efficiency at that. THERMODYNAMICS. 67 INFLUENCE OF WORKING FLUID. In the same manner it may be demonstrated that the nature of working substance has no influence upon the amount of work which can be obtained from a given amount of heat in a reversible cycle. For if one sub- stance could be employed to yield a greater amount of work from the same amount of heat than another sub- stance, and vice versa, a combination between two cycles, each one employing one of the two substances, could be formed like the above, which would create the same im- possible results. It Should be noted that this deduction holds good only when the two cycles work between the same limits of temperature, and when no molecular changes take place in the working fluid, the mass of the latter remain- ing constant. RATE OF CONVERTIBILITY OF HEAT. The maximum amount of work derivable from a t given amount of heat in a continuous cycle of operations, being accordingly independent of the nature of the work, ing substance, and obtainable by every ideal reversible cycle, the rate of maximum conversion may be deduced from the working of any such cycle of operations. To do this we select as the working substance in our ideal cycle a perfect gas, since the laws governing the relation of pressure, temperature and volume in this case are not only well known but also comparatively simple. The first ideal reversible cycle of operations to determine the maximum convertibility of heat has been devised by Carnot, to whom the original elaborations of this subject are due. Of course any reversible cycle answers also. For simplicity's sake, following the example of Nernst, we use a cycle which is to be considered re- versible when working between very small differences of temperatures (between boiler and refrigerator). SYNOPSIS OF NUMERICAL PROOF. Consequently we assume that the absolute tempera- ture, TI, of the boiler or generator is only a little higher than the temperature, T , of the refrigerator, when the working of our ideal cycle and its numerical theoretical result may be delineated as follows: The mechanical de- vice consists of an ideal cylinder provided with a movable piston containing a certain amount of a permanent gas of 68 MECHANICAL REFRIGERATION. the volume u t . The cylinder is immersed in the refrig- erator of the temperature T , and by forcing down the piston (reversibly) is compressed to the smaller volume v z . The work, A, required to perform this change is ex- pressed by- A = BTa ln-^- E being the constant of the gas formula as above de- fined, and In standing for natural logarithm. As the temperature is to remain constant, an amount of heat, $, equivalent to the work done must be imparted to the condenser, i. e. : Q being expressed in the same units as A. Now the cylinder is immersed into the generator or boiler and allowed to assume the temperature T , while the volume remains constant, v z . The heat which is hereby con- veyed to the gas is c being the specific heat of the gas at constant vol- ume. At this juncture the gas is allowed to expand from the volume v 2 to the volume v t , and the work A t , which is done on the piston, is expressed by At=BTJn^~ while at the same time an equivalent amount of heat passes from the generator to the gas in the cylinder, i. e.: Now the cylinder is brought back to the refrigerator, where, while the volume remains constant, the temper- ature is again reduced to T , the amount of heat, e(2\ T ), being transferred from the gas in cylinder to the refrigerator or condenser. The gas is now again in its initial condition, and the operations for one period of the cycle are completed. The useful work, W, gained by this operation is while the amount of heat, H, which has been with- drawn from the boiler or source is equal to THERMODYNAMICS. 69 If we call W the total amount of work gained, and H the total amount of heat expended by the heat source to obtain the heat source, we can write If we take T t T Q , infinitesimally small, we can neg- lect the term c (TV T ), as against the infinitely greater quantity E T t In ^-, and we can write v? W_ r t T H~ T, EFFICIENCY OF IDEAL CYCLE. W The term -TT, i. e., the work obtained divided by the amount of heat (expressed in the same units) expresses what is termed the efficiency of the cycle. Generally speaking, therefore, the convertibility of a certain amount of heat into work is the greater, the greater the difference of temperature between boiler and condenser, i. e., the greater 7 7 1 T , and the lower this difference is located on the absolute scale of temperature, that is, the smaller 2\ under otherwise equal conditions. The limit is reached when T becomes zero (absolute)= 493 F., and W H, a condition which cannot even be approached in practical working. CARNOT'S IDEAL CYCLE. The ideal cycle originally devised by Carnot embraces four such operations. First, the cylinder with piston con- taining a given volume of a permanent gas is brought in contact with the heat source or boiler, and" after it has attained that temperature and the pressure correspond- ing thereto, the piston is allowed to move forward against a resistance which is continually infinitesimally less than the pressure within (i. e., reversibly). An amount of heat equivalent to the work done by the piston passes from the source of heat to the cylinder, so that the gas always maintains the temperature of the source, Aeuce the expansion is isothermal. Now the cylinder is removed from the source ol heat to conditions which are supposed to be so that it can neither take in nor give out heat, and while under such 70 MECHANICAL REFRIGERATION. conditions the piston is allowed to move forward again with the same precaution as to pressure. The expansion in this case is adiabatic, and it is allowed to proceed until the gas in the cylinder has attained the temperature of the colder body the refrigerator, to which the cylinder is then removed. The piston is now forced inward reversibly, the heat of compression being withdrawn by the refrig- erator; the temperature remains the same,thus constitut- ing an isothermal compression. After this isothermal compression the cylinder is again brought under condi- tions where it can neither absorb nor discharge heat, and under these conditions is further compressed reversibly, until the gas within has acquired the temperature of the source of heat or boiler. With this fourth adiabatic operation, the cycle is completed, the working substance having been returned to its original condition, and each and all operations may be performed in the re versed order. HEAT ENGINES. A heat engine is a contrivance for the conversion of heat into mechanical energy, and in accordance with the above laws the efficiency of such a machine does not depend on the nature of the working substance (steam, hot air, exploding gas mixtures, etc.), but only on the temperature which the working substance has when it enters and when it leaves the machine. AVAILABLE EFFECT OF HEAT. The relation between a given amount of .heat ( IT) employed in a heat engine and the greatest amount of work ( W) which can be derived from same (expressed in units of the same kind) finds its expression in the said equation: W T t T TT 2\ in which T t is the temperature at which the heat is fur- nished to the engine, and T the temperature of the re- frigerator or condenser at which the heat leaves the en- gine. The temperatures are expressed in degrees of ab- solute temperature. CONSEQUENCE OF SECOND LAW. The above equation is a concise mathematical ex- pression of the second law of thermodynamics. If in the same, T becomes zero If will become W; in other words, THERMODYNAMICS. 71 in a machine in which the refrigerator or condenser temperature is absolute zero, the whole amount of the heat employed can be converted into mechanical energy, and it furnishes an important additional proof for the reality of an absolute zero of temperature, which is fre- quently looked upon as a mere scientific fiction. IDEAL REFRIGERATING MACHINE. A similar deduction can be made when the opera- tions of the above cycle are reversed, the gas being allowed to expand at the lower temperature, taking heat from the refrigerator and its compression being performed at the higher temperature, discharging heat into the boiler. Instead of heat engine we have now a refrigerating ma- chine, and one representing conditions of maximum efficiency which must find its expression in the same equation reversed, viz.: H_ T w T IV-TO EFFICIENCY OF REFRIGERATING MACHINE. The above equation signifies that by expending the amount of work W, we can withdraw the amount of heat H from a body (refrigeration) of the temperature T , and transfer the same to a body (boiler called con- denser in the refrigerating practice) of the temperature 2\. The equation also shows that the efficiency of a refrigerating engine depends on conditions quite opposite to those applying to the efficiency of a heat engine, the conditions being, that the refrigeration which can be obtained by expending a certain amount of work is the greater the smaller 2\ T and tne larger 2\, that is the higher 2\ T is on the scale of temperature. FALL OF HEAT. In analogy with the conversion of the energy of falling water into mechanical energy and still following Carnot, it is sometimes stated that the amount of heat W while falling from the temperature T t to 2' is capable of doing the work If. We see now that this expression is not correct; the amount of heat W leaves the source or boiler having the temperature T lt but only the amount W H enters the refrigerator or falls to the temperature T in a reversible heat engine. 72 MECHANICAL REFRIGERATION. On the other hand, in a reversible refrigerating ma- chine the amount of heat W leaves the refrigerator at the temperature T and the amount W-\- H is brought over to the warmer body having the temperature 2\. COMPENSATED TRANSFER OF HEAT. When a certain amount of heat passes from a warmer to a colder body a portion of the same can be intercepted, as it were, to be converted into mechanical energy or work. If the maximum amount of work obtainable in this manner in accordance with the above equation has beer* produced, the transfer of heat from the warmer to the colder body is said to be fully compensated. The availa- bility of the energy of the whole system participating in the transfer has not been changed, since the process is reversible and the former condition can be fully re-estab- lished, theoretically speaking. UNCOMPENSATED TRANSFER. When, however, heat passes from a warmer to a colder body without doing any work (as is the case in radiation of heat) or without doing the maximum amount of work obtainable, a corresponding amount of the availability of energy is wasted or dissipated, the heat at the lower temperature being lower on the scale of availability than it was before the transfer. In this case the transfer of heat is said to be not compensated, or only partially com- pensated. In the same way mechanical energy may be dissipated when expended without transferring the max- imum amount of heat from a colder to a warmer body, as it is expected to do in the refrigerating practice. ENTROPY. ' This term is used to convey different meanings by different writers. It was originated by Clausius to stand for a mathematical abstraction expressing the degree of non-availability of heat energy for the production of me- chanical energy under certain conditions. LATENT AND FREE ENERGY. That portion of energy present in a system which may be converted into its equivalent of mechanical work is called free energy, and the remaining energy is called latent energy. Hence when a transfer of heat takes place in a system without due compensation, the free energy decreases, and the latent energy of the system THERMODYNAMICS. 73 increases correspondingly. In accordance with this con- ception the latent energy of a body divided by the tem- perature is the entropy of the body; the increase of the lament energy in a body, divided by the temperature at which it takes place, yields the amount of increase of en- tropy, and vice versa. FUTURE CONDITION OF UNIVERSE. Only the changes of the entropy can be determined, not its absolute amount. As most changes take place w thout full compensation, not reversibly, it has been ci ncluded that the entropy of the universe is constantly increasing, tending toward a condition when all energy will be latent, i.e., not available for further conversion o r changes. In reversible changes the entropy remains unchanged. CHANGES OF FREE AND LATENT ENERGY. The equation expressing the efficiency of an ideal leversible cycle of operations, viz.: w TIT O -H = ~TT may also be written This equation furnishes also an expression for the change of free and latent energy in a system in which transfer of heat without compensation, or with only partial compensation, takes place. If the compensa- tion is complete the expression ^ - jT" ' W is aero, and the amount of free and latent energy remains thesame;butif H(ri ~ ro) TT> that is, if IF is small- J- i TJ I fjl _ /TT \ cr than { , the equation covers all cases in which the changes are not reversible, and the con- version is incomplete. The free energy of the sys- tem has been decreased correspondingly in accordance with this equation. As W can never become larger TT / rn _ /TT \ than - 7p , the above difference can never be neg- ative, which means that the free energy of a system can f4 MECHANICAL REFRIGERATION. TT I rrt _ rrt \ never increase. If in the equation, W ^ jfi - ~ T^ JL i T is equal to 1, the equation becomes W H W which means that the convertible energy of the amount of heat, .H, while passing from one temperature to an- other one degree lower, with full compensation, is equal to that amount of heat divided by its absolute tempera- ture. INCREASE OF ENTROPY. If an amount of heat, JET, in a system is transferred from a higher temperature, T lt to a lower temperature, jT , without compensation, the free energy decreases, and the latent energy increases by an amount and the increase of entropy, in accordance with a former definition, is expressed by the term Reversing the above argument, we can also say: If an amount of heat, H, leaves a body of the temperature T n the entropy of that body decreases by the amount 7-7" 7p-, and when this same amount of heat enters another -* i body of the temperature T (transfer without compen- sation), the entropy of the second body is increased by the TT amount . The increase of the entropy of the system *o comprising the two bodies is therefore, as above __ T Q T t ~ T, T ORIGIN OF HEAT ENERGY. The source of nearly all, if indeed not of all, forms of energy applicable for the production of heat and power, is traceable to the sun, the radiant energy of whose rays has been converted into potential or chemical energy in the plants, whence it found its way into the deposits of coals, etc. The heat of the sun's rays also produces the vapors which reappear as water falls, etc. ; it also brings THERMODYNAMICS. 75 about the commotion in the atmosphere which appears in the force of waves and in the useful applications of the wind as well as in the devastations of the storm. SPECIFIC HEAT OF GASES AT CONSTANT VOLUME. In accordance with the molecular theory, the specific heat or the increase of heat energy for an increase of one degree in temperature for a molecule of a gas, or a propor- tional quantity of the same of the weight, Jlf, is expres- sible ( 1 Tlfr/2 ) JCv= \-~^- + E \ in which CVis specific molecular heat at constant volume, T the absolute temperature, J the mechanical equivalent of heat, and 22 the heat required to increase the motion within the molecule, u the velocity of the molecule as above defined. SPECIFIC HEAT UNDER CONSTANT PRESSURE. If a gas is heated under constant pressure the volume increases, and a certain amount of work is done, the equivalent of which in heat must also be furnished to the gas when its temperature is elevated. If we express the work done by pv I Mu* T ' 3 T the specific heat of a molecule (expressed in units of weight) of gas under constant pressure, C P , is hence 5 M n 2 or JTmust always be smaller than f = 1.6667, since E must always be positive, and when it is very small, K ap- proaches this value, as for vapor of mercury (1.666), in which the molecule is probably composed of only one atom, while in gases of presumably very complex mole- cules, the value for K approaches the other limit, viz., 1, as for ether, K= 1.029. COMPONENTS OF SPECIFIC HEAT OF GASES. From the foregoing we know that the heat required to do the work of expansion, when a gas is heated under 76 MECHANICAL REFRIGERATION. constant pressure, is always equal to two-thirds of the heat necessary to increase the energy of the molecule. We find the specific heat, c 1} for equal volumes of gases under constant pressure, to be composed as follows: Heat to increase molecular motion = 3 x 0.034 Heat to do work of expansion = 2 x 0.034 Heat to do internal work (in molecule)... = n x 0.034 Specific heat. = (n + 5) 0.034 n being the number of atoms composing the molecule. As for perfect gases, we can substitute equal volumes for equal number of molecules (since the same volumes of different gases contain an equal number of molecules), we can also say that for equal volumes of practically per- fect gases, the specific heat is the same (see page 47). NEGATIVE SPECIFIC HEAT. When the heat equivalent of the work required to compress a saturated vapor from a lower to a higher pressure is greater than the heat required to increase the energy of tjie molecules of that vapor, from the temper- ature corresponding to the low pressure to the temper siture corresponding to the higher pressure of the satur- ated vapor, then the specific heat of such saturated vapor is said to be negative. For heat must be abstracted during compression to keep it in a saturated condition, and when allowed to expand a portion of the saturated vapor will condense for the same reason. AIR THERMOMETER. As the expansion of liquids and solids by heat is not uniform throughout the thermometric scale, this con- stitutes a serious defect in all thermometers constructed by their aid. This difficulty does not exist when air or another gaseous body is used as the thermometric sub- stance. Hence the air thermometer is used for exact determinations. THERMODYNAMIC SCALE OF TEMPERATURE. If a thermometer be graduated in such a way that each degree increase in temperature of the thermometric substance adds equal amounts of free heat energy or equal amounts of heat available for mechanical conver- sion to the thermometric substance, we have a thermo- dynamic scale of temperature as devised by Thomsen. The degrees of such a scale agree very nearly with those of the air thermometer. THERMODYNAMICS. HEAT WEIGHT. In accordance with the terminology adopted by Zeuner, the " weight" or "heat weight" of a certain amount of heat, H, transferable at the absolute temper- ature T, is that portion or fraction of said amount of heat which is convertible into mechanical energy, viz.: TT -7p If the same amount of heat, H, enters a body at the constant absolute temperature T (without compen- sation), the entropy of that body is said to increase by TT an amount -^. Hence entropy and heat weight are ex- jv/essions which are numerically synonymous. The terms t hermodynamic function (Bankine), and Carnot's func- tion are used in the same connection. Thomson's ther- modynamic scale of temperature shows equal heat weights from degree to degree. Thermodynamics also teaches that the difference be- tween the specific heat of a gas at constant pressure, c p , and that at constant volume, c v , is a constant quantity, and equal to the constant R of the gas equation, viz.: ISENTROPIC CHANGES. Adiabatic changes which are at the same time revers- ible are also called isentropic changes, because such changes do not alter the entropy. LATENT HEAT AND ENTROPY. The heat which enters a body at the same or at con- stant temperature is called latent heat. Hence entropy may also be defined as latent heat divided by the corre- e ponding temperature. Accordingly during vaporization cr fusion of a body its entropy is increased. The amount of increase may be expressed by -7^- when I stands for the latent heat of vaporization or fusion, and T for the boil- ing or melting point expressed in absolute degrees F. If a gas expands at constant temperature while do- ing work, it absorbs an amount of heat equivalent to the amount of work done, and its entropy increases corre- spondingly. Chemical changes taking place at constant temperature with transferences of heat cause correspond- ing changes of entropy. 78 MECHANICAL REFRIGERATION. CHAPTER VIII MODERN ENERGETICS INTRODUCTORY REMARKS. In the foregoing paragraphs mass has been treated as one of the fundamental units, and as the vehicle not only of mechanical energy, but also of molecular energy according to the atomistic or mechanical theory of natural phenomena, which is still more or less generally accepted, and therefore followed in this compend. SYSTEM OF ENERGETICS. More recently following the example of Ostwald, Gibbs and others,it has been found expedient to consider energy not as a function of mass, but as something real, tangible and unchangeable in itself, thus creating a new series of scientific conceptions in accordance with which mass appears in the role of a factor in mechanical energy. The terminology of this system places many defini- tions in a plainer and clearer light, and is frequently used in discussions on questions of energy, so that a synopsis of its tenets will be welcome to those who desire to study them. NEW DEFINITION OF ENERGY. Energy may also be defined as that immaterial quantity which, while it causes the greatest variety of changes or phenomena between different objects, always maintains its value. This definition involves the princi- ple of conservation of energy. CLASSIFICATION OF ENERGY. The different forms of energy may also be classified in the following groups: 1. Mechanical energy. 2. Heat. 3. Electric and magnetic energy. 4. Chemical or internal energy. 6. Radiated energy. MECHANICAL ENERGY. The mechanical energy may be subdivided into two classes, viz.: The energy of motion or kinetic energy, and the energy of space, with the following subdivisions: 1. Energy of distance (force). 2. Energy of surface (surface tension). . Energy of volume (pressure). MODERN ENERGETICS. 79 ENERGY FACTORS. According to Helm, etc., the different kinds of energy- are expressible by two factors one of intensity and the other of capacity. Equal increases or decreases of energy in a given system or configuration of bodies "correspond to equal increases or decreases of intensity, or, in other words, the energy of a system is proportional to its in- tensity. This may be expressed by the.formula E=ci in which E represents energy, i the intensity and c the factor of capacity which is a measure for the amount of energy which is present in a system at a given intensity, i, the latter being counted from E = 0. In other words, the capacity factor for energy, c, may also be termed the capacity of the system for energy. The capacity and intensity factors of some of the various forms of energy are given as follows: ENERGY, CAPACITY. INTENSITY. ( . V* Mass (m) . Square of velocity A. Kinetic energy. J v * | Quantity of motion Velocity I (mv). 2 B. Energies of space a. Energy of Length. Force. distance. 5. Surface en- ergy. Surface. Surface tension. c. Energy of volume. Volume. Pressure. C. Heat. D. Electricity. Capacity for heat. Quantity of elec- Temperature. tricity. Potential. E. Magnetism. Quantity of mag- netism. Magnetic potential. F. Chemical energy, , Atomic weight. Affinity. DIMENSIONS OF ENERGY. The definitions of the conceptions relating to energy, by means of algebraical expressions, or their dimensions are rendered in the following manner: If e stands for the unit of energy, t for time, I for length or distance and m for mass the dimensions of the different mechanical conceptions may be expressed as follows: OLD UNITS. NEW UNITS. 1. Energy, m I 2 i~* e 2. Mass, m e JT~* t* 3. Quantity of motion, m I i~~ l e I 1 1 4. Force, m If * el 1 5. Surface tension, _ra t~~* e I* 6. Pressure, n I l t~ 2 e l~* 7. Effect, ml*t 3 e 80 MECHANICAL REFRIGERATION. The first three definitions belong to the domain of kinetic energy, 4, 5 and 6 represent potential energies, and 7 the effect corresponding to the mechanical concep- tion of a horse power. The dimensions as given in the second column differ from those in the first column in that the third funda- mental unit energy is substituted for mass, in accord- ance with the foregoing definition of energy factors. THE INTENSITY PRINCIPLE. Energy will pass from places of higher intensity to such of lower intensity; but energy of a certain intensity cannot pass to such of the same or of higher intensity. A system containing but one kind of energy is in equili- brium if the intensity of energy is the same throughout the system. If the intensity is not the same changes will occur until the differences in intensity have bed a equalized. If two intensities are equal to a third inten- sity, they are equal among themselves. COMPENSATION OF INTENSITIES. If more than one kind of energy is present in a sys- tem the differences in intensity of one kind of energy may be balanced or compensated by differences in .the intensity of other kinds of energy; hence, in order that a change may take place in such a system, there must be differences of intensities not compensated. If in a system containing several forms of energy, there are sudden leaps or differences in the intensity of one energy they must be compensated by equivalent sud- den leaps or differences in the intensity of some other form of energy in order that equilibrium may exist in the system. REGULATIVE PRINCIPLE OF ENERGY. Everything that happens, every change or phenome- non is the sensible demonstration of a transfer or trans- formation of energy. Of different changes possible to take place in a sys- tem containing one or more kinds of energy, that change will take place which causes the greatest amount of transformation or transference of energy in the shortest time. The term ' l possible changes ' ' implies such changes as would be in harmony with the general laws of energy. STATE OF EQUILIBRIUM. A change (compatible with the conditions of exist- ence) in a system containing different kinds of energy MODERN ENERGETICS. 81 in equilibrium must add and abstract equal amounts of energy if equilibrium is to be maintained. The algebra- ical sum of energy lost and energy gained is equal to zero, a relation providing an important criterion for the state of equilibrium. ARTIFICIAL AND NATURAL TRANSFER. Energy may maintain equilibrium or become trans- ferred or transformed artificially by means of certain ap- pliances or devices (machines) or without such means. The latter transfers may be called natural transfers. ARTIFICIAL EQUILIBRIUM. If in a system containing two kinds of energy in equi- librium, the compensation of the intensities is effected by artificial means, i. e., a machine, then such a contrivance directly determines the relation of one factor of one energy to one factor of the other energy, and therefore indirectly also the relation of the other factors. DISSIPATION OF ENERGY. The difference in intensities of energy not compen- sated determines the ability of such energy to do work or bring about changes. Hence the difference in intensities is a measure of the availability of the respective energy to do work. After a change has taken place the sum total of energy (capacities multiplied by intensities) must be the same as before the change, but the availability of the energy for the production of further changes is gener- ally lowered. This is due to the fact that after the change in one or more forms of energies has taken place the capacities have generally been increased and inten- sities decreased correspondingly. In other words, the difference in the intensity of one energy which has disap- peared has not been compensated by the appearance of an equivalent difference in the intensity of another .energy. The tendency which prevails in all natural as well as artificial processes or changes, to increase the capacity at the expense of the intensity of existing energy, or, in other words, to obliterate existing differences in inten- sities, is the cause of what is termed the dissipation of energy. RADIANT ENERGY. The state or condition of energy while on its way from one body to another without a ponderable inter- vening medium is called "radiant energy." Energy in 82 MECHANICAL REFRIGERATION. chis condition and connection is supposed to possess some of the qualities referable to the hypothetical medium ether, notably elasticity. TRANSFORMATION OF ENERGY. The compensation of a change in one form of energy by an equivalent change of another form of energy con- stitutes what is also termed the transformation of one kind of energy into another. REVERSIBLE CHANGES. If the change produced by decreasing the difference in intensity of a given quantity of one form of energy has been fully compensated by an equivalent amount of difference of intensities of some other form or forms of energies having made its appearance, such a change may be considered reversible (in the abstract, at least). Two co-ordinated reversible changes, if fully performed, re- establish the original condition of things before the change. IRREVERSIBLE CHANGES. Changes in which energy is dissipated are not revers- ible, and hence may be termed irreversible changes. PERPETUAL MOTION. . Irreversible changes are inseparably connected with all practical operations, and hence a perfectly reversible operation is a practical impossibility. Such an operation, if it were possible, could be repeated without end, and would constitute what is termed a "conservative system," which would be a kind of perpetual motion akin to that of the heavenly bodies. Such a perpetual motion, while beyond the possibilities of human skill, is not in contra- diction with the laws of energy. Besides the perpetual motion or' a conservative sys- tem,wemake a distinction between attempts at perpetual motion of the first order and of the second order. The first kind contemplates the actual creation of energy, or of power to do work, and is in direct conflict with the first law of energy proclaiming its absolute con- servation and indestructibility and its transf ormability in equivalent proportions. Perpetual motion of the second order involves the elevation of the intensity of energy without compensation, which is in direct conflict with the intensity principle or the second law of energy. MODERN ENERGETICS. 83 CONTINUOUS CONVERSION OF ENERGY. . As a rule nothing could be gained in a practical way by carrying out the two co-ordinate systems of reversible changes; the useful object generally ,is to produce changes in one definite direction, and not undo them by reversion. This is notably the case in our efforts to con- vert energy of one kind into energy of another kind by a continuous process, as when heat energy is converted into motive power or mechanical energy, etc. In all such efforts a certain percentage of energy is dissipated, that is the energy expended cannot all be compensated for in the desired direction. MAXIMUM CONVERTIBILITY. It follows from the above that when energy is trans- formed by processes or operations which are reversible (in the abstract, at least) the greatest possible amount of transformation (i. e., incurring no dissipation of energy) is effected, as otherwise perpetual motion of the second order could be produced by reversing the operations. For the same reason the maximum amount of energy obtainable by transforming a certain amount of another energy depends solely upon the uncompensated difference in the intensity of the latter energy and on the position which it holds on an absolute intensity scale, counting intensity from its proper zero. Hence the maximum of transformation obtainable in a certain direction is inde- pendent of the special object with which the energy is con- nected, or which is instrumental in the transformation. INTENSITY PRINCIPLE AND ENTROPY. The intensity principle is a general form of the second law of thermodynamics. It broadly asserts that while energy of any kind may pass from places of higher inten- sity to such of lower intensity without compensation, the reverse change, i. e., the passage of energy from places of lower intensity to places of higher intensity, can never take place without compensation. In all natural changes, in all manifestations of energy, the changes are either so as to fully compensate each other, or when this is not the case, the deficiency in compensation must correspond to so much increase of latent energy, and to a corresponding increase of entropy. In other words, natural changes proceed either without changing the entropy or by increasing the same. 84 MECHANICAL REFRIGERATION. Hence the conception of the entropy function enables us to determine as to the possibility of any supposed change in a system of bodies. If the change involves a decrease of entropy, it must be deemed impossible. If, however, the change involves no decrease of entropy, but if the same would remain unchanged or increase, then the said change is not in conflict with the laws of ener- getics. JUSTIFICATION OF CONCEPTS. The importance and significance of the above some- what fragmentary and abstract definitions and concepts becomes more apparent in the treatment of the different individual branches of energetics, and especially in ther- modynamics. It is in this branch that the above principles have their origin and confirmation, and it is in this branch that they prove their adaptability and usefulness for the further development of science, which usefulness must plead the justification of these concepts. Moreover their unrestricted adaptability in all other branches of science appears to be only a question of time. UNIFORM UNITS OF ENERGY. One kind of energy being transformable into an equivalent amount of another, it is indicated to so select the units for different forms of energies as to represent equivalent quantities. This is accomplished in a manner by some of the C. G. S. units. CHANGE OF ABSOLUTE ZERO. In the foregoing thermodynamic discussions the point of absolute zero has been taken at 461 degrees be- low zero Fahrenheit, as it is universally accepted so far. Recently, however, in his experiments to liquefy helium (the new gaseous element discovered in the atmosphere) Olszewski reached a temperature as low as 443 below zero, and helium remained a gas still. But judging from the pressure, etc., it will become a liquid at a tempera- ture of about 570 F. below zero. This temperature must therefore still be above absolute zero, although it is impossible to say how much. At any rate, it is more than likely that a different absolute zero point will have to be accepted in the future, and that then our concep- tions in thermodynamics will also receive important additions. But the experiments mentioned must be fur- ther confirmed before any definite changes are advisable. MECHANICAL REFRIGERATION. PART II. PRACTICAL APPLICATION. CHAPTER L-REFRIGERATION IN GENERAL. REFRIGERATION. The act of reducing the temperature of any body or keeping the same below the temperature of the atmos- phere is called refrigeration. MEANS OF PRODUCING REFRIGERATION. Refrigeration may be produced in many ways : 1. By transferring heat from a warmer body to a colder one. (Refrigeration by cooled brine, etc.) 2. By the consumption of heat brought about by doing work. (Working a piston against resistance with compressed gas ; air machines.) 3. By melting or dissolving solid bodies. (Melting of ice ; solution of salts in water, etc.) 4. By evaporating liquids which have a low boiling point. The latent heat of evaporation represents the amount of cold that can be produced in this way. (Evaporating liquid ammonia, liquid carbonic acid, liquid sulphurous acid, ether, etc.) AIR MACHINES. The mode of production of refrigeration by doing work is exemplified in the air machines, as that of Wind- hausen, which was formerly much used on steamers for refrigeration. In this machine the atmospheric air 13 compressed in a compressor, the heat generated by com- pression being carried off by the cooling water. The compressed air is then used to propel an engine, whereby its temperature is reduced corresponding to the work done by it in the engine. The air cooled in this way is then introduced into the rooms to be refrigerated, venti- S6 MECHANICAL REFRIGERATION. lating them at the same time. The machine operates continuously, but the refrigerating agent is rejected along with the heat which it has taken up. FREEZING MIXTURES. The refrigeration obtainable by dissolving solid bodies in water (freezing mixtures) has been referred to on pages 31 and 32. This method may also be employed in a continuous process, but is too expensive to be em- ployed on a large scale, and when done so is chiefly used as an expedient when other means fail. In such case a mixture or solution of salt in ice or snow is generally used. ICE MACHINES. The machines which are now used for the pioduction of refrigerating effects on a large scale are nearly all based on the principle of production of cold by the evaporating of liquids. Preference is given to either ammonia, sulphurous acid or carbonic acid as the evaporating liquid, or a mixture of the latter two. CONSTRUCTION OF MACHINES. The construction of the machines is the same in principle, no matter what evaporating liquid is employed, but the sizes and strength of different parts of the system vary greatly with the physical properties of the liquid, principally the latent heat of evaporation, the tem- perature and pressure of liquefaction, etc. VAPORIZATION MACHINES. The machines which are employed to practically utilize the heat of vaporization for refrigerating purposes may be classified as vacuum machines, absorption ma- chines, compression machines, and mixed absorption and compression machines. VACUUM MACHINES. In the vacuum machines water is used as the refrig- erating medium, its volatilization at a temperature suffi- ciently low being effected by means of vacuum pumps, the working of which is assisted by sulphuric acid, which absorbs the vapors as soon as formed, thus making the action of the vacuum very effective. The sulphuric acid may be concentrated for repeated use. ABSORPTION MACHINES. The- absorption machines are similar to the vacuum machine in their action, the difference being that not REFRIGERATION IN GENERAL. 87 water but a liquid (such as anhydrous ammonia), which evaporates at a low temperature without the aid of a vacuum, is used as a refrigerating medium. The vapors, instead of being absorbed by sulphuric acid, are absorbed by water, and from this they are separated again by dis- tillation, and liquefied by the pressure in the still and the aid of condensing water. In this manner all the larger absorption machines are operated continuously, the solution of ammonia in water being subjected to distillation in a still heated by ti steam worm, the vapors of ammonia entering a con- denser where they are cooled and become liquefied into anhydrous ammonia. The anhydrous ammonia is kept in a liquid receiver, whence it enters the refrigerator coils in which it evaporates, causing a refrigeration corre- sponding to its heat of vaporization. The vapors after having done this duty are allowed to enter the absorber, where they come in contact with the weak solution of ammonia drawn from the lower portion of the still, and are reabsorbed by the same with generation of heat, which is carried away by cooling water. The rich and ?old solution of ammonia doming from the absorber and going to the still, and the poor and hot solution com- ing from the still and going to the absorber, are passed through a device called the exchanger to equalize their temperatures as much as possible. A pump is required to pump the rich ammonia solution from the absorber into the still. THE COMPRESSION MACHINE. The compression machines which use the latent heat of vaporization of substances having a low boiling point, such as ammonia, sulphurous acid, carbonic acid, etc., work practically all on the same principle. The vapors created by vaporization of the refrigerating medium in the lefrigerating coils enter a compression pump, which is operated by a steam engine, which forces the vapor into condenser coils, where they are liquefied with the aid of cooling water. The liquid enters a liquid receiver, from which it is allowed to enter the refrigerating coils, as re- quired. The process is continuous, and represents a cycle of operations as the working substance returns period- ically to its original state, in a manner which approaches' reversibility more or less according to the modes of oper- ating the different machines. 88 MECHANICAL REFRIGERATION. AMMONIA MACHINES. Owing to its high latent heat of evaporation, its comparatively low vapor tension,, admitting liquefaction at a comparatively low pressure and high temperature, its neutral chemical properties, ammonia is highly val- ued for refrigerating purposes, and ammonia machines are now mostly in use for refrigerating purposes in the United States. PERFECT COMPRESSION SYSTEM. In case of a perfect reversible compression system the operations would have to consist of the following changes: First. Evaporation of the liquid ammonia at the (constant) temperature of the refrigerator, constituting an isothermal change. /Second Compression of the vapor so formed with- out addition of heat, which is an adiabatic change. Third. Condensation of the compressed vapor at the (constant) temperature of the condenser, constituting another isothermal change. Fourth. Reduction of the temperature of the liquid from the temperature of the condenser to that of the refrigerator by means of vaporizing a portion of the liquid and doing work by moving a piston. This is the second adiabatic change, and it returns the working fluid to its initial condition, thus completing the cycle, These changes are conceived to be carried on in such a manner that the transfers of heat follow only infini- tesimally small differences in temperature, and the changes in volume take place under but inflnitesimally small differences of pressure. REVERSIBLE CYCLE. Under these circumstances the changes can also be performed in the opposite direction, and therefore the cycle is what is termed a reversible cycle. A heat engine as well as a refrigerating apparatus (a heat engine re- versed), if worked on the plan of reversible cycle, is work- ing on the most economical plan that can be conceived. For this reason the heat, H, removed by a refrigerating apparatus operated strictly on this basis has a certain and well defined relation to the work or mechanical power, W, required to lift the same in the cycle of opera- tion. If in a refrigerating machine so operated t t is the temperature of condenser and t the temperature of the refrigerator (T^ and T Q designating the corresponding REFRIGERATION IN GENERAL. 89 absolute temperatures) thermodynamics teaches us that the following relations exist: H __ t o + 460 _ T W * i DEFECT IN CYCLE. Thermodynamically speaking, there should be no dif- ference in economy on account of the nature of the cir- culating fluid if a perfect cycle of operation was carried out, but practically this is not done. In all compression machines (barring some trials in the case of carbonic acid machines), the fourth operation, the reduction of tem- perature of the liquid while doing work, is not carried out, but the liquid is cooled at the expense of the refrig- eration of the system. No work is attempted, as the amount obtainable would not be in proportion to the ex- pense involved in procuring the same. This defect and other conditions in the working of a reversible cycle have some bearing on the choice of the circulating medium. CHOICE OF CIRCULATING MEDIUM. In the choice of a circulating medium, therefore, we should consider that its refrigerating effect depends on the latent heat of vaporization per pound. That the size of the compressor depends on the num- ber of cubic feet of vapor that must be taken in to produce a certain amount of refrigeration, and the strength of its parts on the pressure of the circulating medium. And also that the loss of refrigeration on account of cooling the liquid circulating medium depends on the specific heat of the liquid as compared with the heat of volatilization. The qualities chiefly involved in this question are compiled, approximately, in the following table for the principal liquids 'employed in refrigeration. Sulphurous acid. Carbonic acid Ammonia flg Ik 10 310 30 Hill* 171.2 123.2 555.5 7.35 0.277 9.10 o *a Is P O C" 0.41 1.00 1 ill ive Vol Compre Equal eration. 23.3 447. 61.7 61.70 3.24 23.3 Per Ct. 0.24 0.81 0.18 90 MECHANICAL REFRIGERATION. This table explains itself and readily accounts for the preference generally given to ammonia as the circu- lating fluid. The loss due to the cooling of the liquid as shown in percentage for every degree difference in tem- perature of condenser and refrigerator, is less than in case of the other liquids, and the total refrigerating effect per pound of liquid is largest. The only instance speak- ing more in favor of sulphurous acid is the lower press- ure of its vapor, while the compressor is smallest in case of carbonic acid, but the pressure and the loss due to heating of liquid is very large in the latter case. SIZE OF ICE MACHINES. The heat unit, as already stated, is used for measur- ing both heating and refrigerating effects. As a matter of convenience, however, the capacity of large refrig- erating plants is expressed in tons of ice. By a ton of refrigerating capacity used in the above connection is meant a refrigerating capacity equivalent to a ton of ice at the freezing point while melting into water at the same temperature. This refrigerating capacity is equal to 284,000 units. ICE MAKING CAPACITY. The refrigerating capacity of a machine is different from the actual ice making capacity of a plant; the lat- ter is considerably less, fifty per cent and upward, of the refrigerating capacity, according to temperature of wa- ter, etc. USES OF REFRIGERATION. The practical uses of mechanical refrigeration are so manifold that it is impossible to enumerate them all in a small paragraph. Foremost among them is cold storage, that is, the preservation of all kinds of. articles of food and drink by the application of low temperature. Slaugh- tering, packing and shipping of meat can hardly be car- ried on nowadays without the use of mechanical refrig- eration, and the days of the few breweries still working without this artificial appliance may be said to be num- bered. Since ice has become an article of daily necessity, there are few towns that have not or will not have their artificial ice factory or factories. Artificial refrigeration is or will be used for a great many other purposes, some of which will be mentioned later on. PROPERTIES OF AMMONIA. 91 CHAPTER II. -PROPERTIES OF AMMONIA. FORMS OF AMMONIA. The ammonia occurs in practical refrigeration in three different forms, as the liquid anhydrous ammonia, the gaseous anhydrous ammonia and solutions of ammo- nia in water of various strengths. ANHYDROUS AMMONIA. Ammonia is a combination of nitrogen and hydrogen expressed by the formula NH 3 which means that an atom of nitrogen (representing 14 parts by weight) is combined with three atoms of hydrogen (representing ttiree parts by weight). At ordinary temperatures the am- ?nonia, or anhydrous ammonia, as it is called in its nat- ural condition, is a gas or vapor. At a temperature of 30 F. it becomes liquid at the ordinary pressure of the atmosphere, and at higher temperatures also if higher pressures are employed. The anhydrous ammonia dis- solves in water in different proportions, forming what is nailed ammonia water, ammonia liquor, aqua ammonia, otc. At a temperature of 900 F. ammonia dissociates, ^.hat is, it is decomposed into its constituents, nitrogen and hydrogen, the latter being a combustible gas. It appears that partial decomposition takes place also at lower temperatures, but probably not to the ex- tent frequently supposed. The liquid ammonia turns into a solid at a tempera- t jre of about 115 F. In this condition it is heavier than tje liquid, and is almost without smell. At a tempera- t ire of 95 F. the chemical affinity between sulphuric acid and ammonia is zero, no reaction taking place be- t #een the two substances when brought jn contact at or below this temperature. Ammonia is not combustible at the ordinary tem- perature, and a flame is extinguished if plunged into the gas. But if ammonia be mixed with oxygen, the mixed gas may be ignited and it burns with a pale yellow flame. Such mixtures may be termed explosive in a certain sense. If a flame sufficiently hot is applied to a jet of ammo- nia gas, it (or rather, the hydrogen of the same) burns as Jong as the flame is applied, furnishing the heat required for the decomposition of the ammonia. Ammonia is not explosive, but when in drums con- taining the liquid ammonia not sufficient space is left for 92 MECHANICAL REFRIGERATION. the liquid to expand when subjected to a higher tempera- ture, the drums will burst, as has happened frequently during the hot season. The ammonia vapors are highly suffocating, and for that reason, persons engaged in rooms charged with am- monia gas must protect their respiration properly. PRESSURE AND TEMPERATURE OF AMMONIA. The relation between pressure and temperature of saturated ammonia vapor is expressed by the formula : 2196 log. 10 # = 6.2495 - in which p is the pressure in pounds per square inch, and Tih& absolute temperature. DENSITY OF AMMONIA. The density d of liquid anhydrous ammonia at different temperatures, water being 1, is approxi- mately expressed by the formula : d = 0.6502 0.00077 t, t being temperature in degrees Fahrenheit. The density of the gas is 0.597 at 32 F., and at 760 mm. pressure. The volume, w, of the saturated vapor per pound may be calculated by the formula : in which P is the pressure in pounds per square foot, T the absolute temperature, h the latent heat of vaporiza- tion. SPECIFIC HEAT OF AMMONIA. The specific heat of liquefied ammonia is variously stated from 1 to 1.228. The specific heat of ammonia gas is given at 0.508 at constant pressure, and 0.3913 at constant volume. The coefficient of expansion of liquid ammonia is 0.00204. The specific heat, s, of saturated vapor of ammonia is expressed by the formula: s _ l _ 555.5 T This value is negative for all values of T less than 555 absolute, which means that if saturated ammonia vapor is expanded adiabatically a portion of it will con- dense, giving up its heat to the remainder of the vapor, PROPERTIES OP AMMONIA. 93 thus maintaining the temperature corresponding to the pressure of saturation, and when compressed heat must be abstracted, if the temperature and pressure are continu- ally to correspond to those of the state of saturation, otherwise it will become superheated. SPECIFIC VOLUME OF LIQUID. The specific volume, v lt of liquefied ammonia may be found after the following rule: .0160 Vi = 0.6502-0.00077* CUblC feet LATENT HEAT. The latent heat, h, of evaporation of ammonia is /i = 555.5 0.613 1 0.000219 t 2 , in which formula t stands for degrees F. EXTERNAL HEAT. That portion of the latent heat required to overcome external pressure or the external latent heat, J, is ex- pressed by in which formula P stands for external pressure in pounds per square foot, v for the volume of the vapor, and v t for the volume of the liquid (which is neglected in the calculations given in the accompanying table), and J the mechanical equivalent of heat. WEIGHT OF AMMONIA. The weight, w, of a cubic foot of the saturated vapor w= And the weight, w^ of a cubic foot of the liquid is .....i The weight of one cubic foot of liquid ammonia at a temperature of 32 F. is 39.017 pounds. TABULATED PROPERTIES OF SATURATED AMMONIA. The physical properties of anhydrous ammonia, both in the vapor and liquid state, which are of special use in the refrigerating practice, are laid down in the follow- ing table prepared by De Volson Wood, calculated by the above formulae which have been elaborated by him also. 94 MECHANICAL REFRIGERATION. PROPERTIES OF SATURATED AMMONIA. ^ TEMPERA- PRESSURE, .2 . o> P< '3 ^ &*T TURE. ABSOLUTE. ac3 jjjf H . rt^ 3 g) i2*3 ~ 03 ^ B ,j , o . . d t-> Wp c3-"S 3 s 1 i s^ ? JB| 11 fflp O . "o r 00 43 P. 3 LJ bo 1 1 S 3 w AS a M 3 3 ? A p f~ 40 420.66 1540.9 10.69 579.67 48.23 531.44 24.37 .0234 .0410 35 425.66 1773.6 12.31 57(5.09 48.48 52S 21 21.29 .0467 30 430.66 2035.8 14.13 573.69 48.77 524.92 18.06 '.02*37 .0535 25 435.66 2329.5 16.17 570.68 49.06 531.62 16.41 .0 38 .0609 20 440.66 8857.6 18.45 567.67 49.38 518.29 14.48 .0240 .0()90 445.66 3022.5 20.99 564.64 49.67 514.97 12.81 .0242 .0779 10 450.66 3428.0 23.77 561.61 49.99 511.62 11.36 .0343 0818 5 455.66 3877.2 26.93 658.56 50.31 508.25 10.12 .0.244 !0'J88 460.66 4373.5 30.37 555.50 50. 6S 504.82 9.04 .0246 .1109 + 5 465.66 4920.5 34.17 552.43 60.84 601.59 8.06 .0247 .1241 + 10 470.66 5522.2 38.55 549.35 51.13 498.22 7.23 .0249 .1384 + 15 475.66 6182.4 42.93 640.26 51.33 494.93 6.49 .0250 .1540 + 20 480.66 6905.3 47.95 543.15 51.61 491.54 5.84 .0252 .1712 + 25 485.66 7695.2 53.43 540.03 51.80 488.23 5.26 .025') .1901 + 30 490.66 8556.6 59.41 536.92 52.01 484.91 4.75 .0254 .2105 + 35 495.66 9493.9 65.93 533.78 52.22 481.56 4.31 .0256 .2320 + 40 600.66 10512 73.00 530.03 52,42 4i'8.21 3.91 .0257 .25 3 + 45 505.66 11616 80.66 527.47 52.62 474.85 3.56 .0260 .2809 + 50 510.66 12811 88.96 524.30 52.82 471. 4S 3 25 .0260 .3109 + 55 515.66 14102 97.93 521.12 53.01 468.11 2.96 .0260 .33 9 + 60 620.66 15494 107.60 517. 93 53.21 464. \ 2 2.70 .0265 .3704 + 65 525.66 16993 118.03 514.73 53.38 461. 35 2.48 .0203 .4034 + 70 530.66 18605 129.21 511.52 53.57 457. K5 2.27 .020ft .4405 + 75 535.66 20336 141.25 508.29 53.76 454.53 2.08 .0270 .4r08 + 80 540.66 22192 154.11 504.66 53.96 450.70 1.91 .0272 .5262 + 85 545.66 24178 167.86 501.81 54.15 447.66 1.77 .027J .5649 + 90 550.66 26300 182.8 498.11 54.28 443. H3 1.64 .0274 .6098 + 90 555.66 28565 198.37 495.29 54.41 440. 8 : * 1.51 .0277 .6623 + 100 560.66 30980 215.14 491.50 54.54 436.96 1.39 .0.379 .7194 + 105 565.66 33550 232.98 488.72 54.67 434.03 1.280 .0231 .7757 + 110 570.66 36284 251.97 485.42 54.7? 430.64 1.203 .0283 .8312 + 115 575. f 6 39188 272.14 482.41 54.91 437.40 1.121 .0235 .8912 + 120 580.66 42267 293.49 478.79 55.03 423.75 1.041 .0287 .9608 + 125 585.66 45528 316.16 475.45 55.09 420.39 .9699 .0289 1.0310 + 130 590.66 48978 340.42 472.11 55.16 416.94 .9031 .0201 1 1048 + 135 595.66 52626 365.16 468.75 55.22 413.53 .8457 .0293 1.1824 + 140 600.66 56483 392.22 465.39 55.29 410.09 .7910 .0395 1.2642 + 145 605.66 60550 420.49 462.01 55.34 406.67 .7408 .0297 1.3497 + 150 610.66 64833 450.20 458.62 55.39 402.23 .6940 .0299 1.43% + 155 615.66 69341 481.54 455.22 55.43 399.79 .6511 .0302 1.5358 + 160 630.66 74086 514.40 451.81 55.46 396.35 .6128 .0304 1.6318 + 165 625.66 79071 549.04 448.39 55.48 392.94 .5705 .0306 1.7344 The critical pressure of ammonia is 115 atmqspheres, the critical temperature at 268 OF. (Dewar), critical volume .00482 (calculated). PROPERTIES OF AMMONIA. 95 VAN DER WAALS' FORMULA FOR AMMONIA. As has been shown (page 56), the constants a and b of Van der Waals' formula can be derived from the critical data, which gave me the following values for am- monia : a =.0079; b = .0016. If the values for a and b thus found for ammonia are introduced in the general equation (page 56), setting p and v equal unit, the equation will read : (v 0.0016)=(1 + . 1.00627 X This equation may be used to establish the relations between pressure, volume and temperature for anhydrous ammonia, and in order to test the same we may compare the results so obtained with those derived from actual ex- periments for saturated ammonia vapor, the volume of which ought to satisfy one of the three values for v which are possible below the critical temperature at the pressure of liquefaction. On this basis the values, p t , for the pressure of am- monia gas for given volumes at given temperatures have been calculated in the following table : t p v i; 1= =~ Pt 40 0.71 34.37 1.282 0.66 15 1.38 12.81 0.674 1.33 + 32 3.96 4.57 0.24 4.02 + 60 7.17 2.7 0.142 7.24 +122 20.3 -1.0 0.052 20.4 +1Q5 36.6 0.57 0.030 36.4 In this table the values for p and v t for the tempera- ture t are in accordance with Wood's interpretation of Regnault's experiments for saturated ammonia vapor, and the values, p lt are derived from the above formula for ammonia by inserting the value, v t , obtained in measuring the volume by the volume of an equal weight of ammonia gas at the pressure of one atmosphere at 32 F. It will be noticed that p t agrees pretty closely with p between 15 and 165, thus proving the approximate correctness of Waals' formula for saturated ammonia within these temperatures, and therefore the formula may doubtless also be safely used for superheated vapor of this substance within these limits for approximate 96 MECHANICAL REFRIGERATION. estimation. Indeed, the agreement between the two sets of pressures obtained by entirely different experiments, and by an entirely different course of reasoning, is suffi- ciently close to inspire the greatest confidence in the ex- periments of Regnault and Dewar, as well as in the mathematical deductions of Van der Waals. SUPERHEATED AMMONIA VAPOR. Below its critical temperature (266 F.) ammonia in its volatile condition is to be termed a vapor, strictly speaking; but when it is not in a saturated condition, but in the condition of a superheated vapor, as it were, it be- haves practically like a permanent gas and is also termed ammonia gas. In this condition one pound of ammonia gas, under a pressure of an atmosphere, and at the tem- perature of 32 F. occupies a volume of 20.7 cubic feet (one cubic foot of air weighing 0.0806 pound, and the specific gravity of ammonia being 0.597 of air under these conditions). FORMULA FOR SUPERHEATED VAPOR. On this basis the relations of volume, weight, press- ure and temperature of ammonia gas or superheated am- monia vapor can be calculated after the general equation of gases on pages 46 and 51. The volume v in cubic feet of one pound of ammonia gas at any temperature, t, and for any pressure, p, expressed in pounds per square inch below that which corresponds to the pressure of saturated vapor at that temperature, or for any pressure and for any temperature above that which corresponds to the temperature of saturated vapor at that pressure, can be found approximately after the formula _ 20.7(461 + 014.7 _ 20.7 (461 + *) = 0.62 (461 + t) 493 X p 33.5 p p If the volume, v, in cubic feet of one pound of am- monia gas at a certain temperature, i, is known, the press- ure can be found after the equation _ 20.7 (461 -H) 0.62 (461 + 1] P = 33.5 v. v And if the volume, v, and the pressure, p, are known the temperature may be determined approximately after the equation = 1.62 p v 461 PROPERTIES OF AMMONIA. 97 As stated above, the formula of Van der Waals may also be used in this connection, but it is rather too cumber- some for this purpose. However, if the value of 20.7 in the foregoing formulae is substituted by 19, which is the figure found in accordance with Van der Waals' equation, the results agree closer with the figures obtaining for vapor just saturated. The table on " Properties of Am- monia Gas or Superheated Vapor of Ammonia " in the appendix agrees practically with the formula given for v, on page 96, and for this reason gives only approximate values, since said formula considers ammonia a perfect gas, which it is not, as indicated by Van der Waals. AMMONIA LIQUOR. The solutions of anhydrous ammonia in water are employed in the so called absorption machines, and the properties of such solutions vary with their strength or the percentage of ammonia which they contain. The strength of such solutions, "ammonia liquor," as they are commonly called, is approximately determined by spe- cific gravity scales or hydrometers, those of Beaume be- ing usually employed for this purpose. STRENGTH OF AMMONIA LIQUOR. Percentage of Ammonia by Weight. Specific Gravity. Degrees Beaume Water 10. Degrees - Beautne" Water 0. 1.000 10 1 0.993 11 1 2 0.986 12 2 4 0.979 13 3 6 0.972 14 4 8 0.966 15 5 10 0.960 16 6 12 0.953 17.1 7 14 0.945 18.3 8.2 16 0.938 19.5 9.2 18 0.931 20.7 . 10.3 20 0.925 21.7 11.2 22 0.919 22.8 12.3 24 0.913 23.9 J3.2 26 0.907 24.8 14.3 28 0.902 25.7 15.2 30 0.897 26.6 16.2 32 0.892 27.5 . 17.3 34 0.888 28.4 18.2 36 0.884 29.3 19.1 38 0.880 30.2 20.0 PROPERTIES OF AMMONIA LIQUOR. On the following pages we publish a table prepared by Starr, and based on experiments made by him, which shows the relations between pressure and temperature for solutions of ammonia in water of different strengths. MECHANICAL REFRIGERATION. QQ, ts * 5 s- s M "?! Jl S *- II DS PRE.SSUI^ ic DE&RE.E.S ^1- 11, 11 - 1515 in 11 I" s -itl SfS N6 CSN-2^ PROPERTIES OF AMMONIA. 99 Cfr I 3 ^rJ *i S ^ <3 T 3\i n a & g^ 5j s s. B I - ^ cs 3 a - e ; r T \ j j I s : ^ * * ! j rC 5 S s s s. J J ? i .i 5 2 ^ S j - I ; ! s 5 * r 5 \ S S j 2 J^ sr 1 s I s j I s -1 e tt ! 3 3 ; 5 ? j ^ s i, 5 j ? ~ 5 j S i | s n | \ s r r 5 S ! ; i 5 ? $ 1 n * .; I s j ^ I ;- 3- ; ^ S 1 1 S B s r I 7 j 1 1 i I s r I 3. r 1 = s ?l | -t a | i i s 4 i k i j a I 5 n [ j 2 a w | 3 i ! g i i 5 ? fc | r 4 L &, 4 S |g T "> | 1 1 | 3 | i | 5 i j ^ ? f ^ P- | f >s- i- I a 3 I 1 i i 3 Z 3 i a S s 4 5 ~ S 3" 5 i 2 -2 * 1 o | 5 I 3 s 1 1 s i r 5 a i 1 ? 1 -? -5" i i 5 1 ? R R : S S i 8 3 i i i i 5 s 4' n. g | PL f- ? | i -5 1 e 5 J S S P 3 1 S i I . 3 1 I 6 R | | ? - 1 | -a ei | 5 | -T> d i r i !T i i & r I i r i 5. fe | | | i i 5 5 1 5 S i i | cr | f s S o S s sJ 3- i te I ; R | | | * ^ 5 R ? ? i i d s 5 5 1 s - i H- 5 5 1 ft ii S 'I ^ * 5 J s ^ s T 1 z 5 5 K Jt ^ H % s w i 1 I I I i f t * ^ wT S nr 1 1 g 1 I V s. p. a i i | a a 1 ? ? 1 * \ K g ~ 1 ? 1 S5 a s 2" s 3 s ? ^i S 1 s .i | | 8 i 5 3 5 s s* ,T s ~0 i 2 S a? t- s ? ^ = \f* | i S I 1 5 5 3 $ 1 r> a Q 1 | ^ 5 S ~ b 5 [ 1 i f i 3- 1 5 A j- f i | 1 | ~ 1 ^5 s ;, s | ^ o 1 s S |: 5; ^ I j . y. 1 % i ^ S 5 | S R * - i ! 5 S - r* ^ 5- g 2 d a J S s jcj s- = g S g ^> 3 o 0^ ;^- 1 S^ f g ~ Ci g = =i -8 ^ 9, 5 | 1 3 0^ I b c5 a 5 JO g 1 * i 00 <> ^ ^ 05 ] "S QQ S 3> ^ * ^ * J 100 MECHANICAL REFRIGERATION. BEAUME SCALES. It should be noted that there are three Beaume" spe- cific gravity scales, or hydrometers; one of liquids which are heavier than water, and two for liquids lighter than water. Of the latter two the scale of the one designates pure water 10, and the other designates pure water zero. As ammonia liquor (comprising mixtures of water and ammonia in all proportions) is lighter than water, only the latter two Beaume scales come into question in this respect, and generally the one which designates pure water 10 is referred to when mentioned in connection with ammonia liquor, and the degrees given in this con- nection correspond to a certain specific gravity, i. e., to a certain percentage of water and ammonia contained in the ammonia liquor as shown in the table on page 97 . SATURATED SOLUTION OF AMMONIA. The amount of ammonia which can be absorbed by water decreases with the temperature, as is shown in the following table. SOLUBILITY OF AMMONIA IN WATER AT DIFFERENT TEMPERATURES (ROSCOE). Pounds of Pounds of Degrees Celsius. Degrees Fahrenheit. NH 8 to one pound Degrees Celsius. Degrees Fahrenheit. NH 3 to one pound water. water. 32. 0.875 28 82.4 0.426 2 35.6 0.833 30 86. 0.403 4 39.2 0.792 32 89.6 0.382 6 42.8 0.751 34 93.2 0.362 8 46.4 0.713 36 96.8 0.343 10 50. 0.679 38 100.4 0.324 12 53.6 0.645 40 104.0 0.307 14 67.2 0.612 42 107.6 0.290 16 60.8 0.582 44 111.2 0.275 18 64.4 0.554 46 114.8 0.259 68. 0.526 48 118.4 0.244 22 71.6 0.499 50 122. 0.229 24 75.2 0.474 62 125.6 0.214 26 78.8 0.449 54 129.2 0.200 56 132.8 0.180 The heat H n developed when one pound of ammonia is dissolved in as much poor liquor containing one pound of ammonia to n pound of water, in order to obtain a rich liquor which will contain 6 + 1 pound of ammonia for each n pound of water (see pages 101 and 102) is H=925- 284 + 142b unit,. n PROPERTIES OF AMMONIA. 101 The figures in the following table on the solubility of ammonia in water at different temperatures have been obtained by Sims: Degrees Fahr. Lb.ofNH 3 to 1 Ib. of Water. Volume of NH 3 inl Volume of Water. Degrees Fahr. Lb.of NH 8 to 1 Ib. of Water. Volume of NH 3 inl Volume of Water. 32.0 0.899 1,180 125.6 0.274 359 35.6 0.853 1,120 129.2 0.265 348 39.2 0.809 1,062 132.8 0.256 336 42.8 0.765 1,005 136.4 0.247 324 46.4 0.724 951 140.0 0.238 312 50.0 0.684 898 143.6 0.229 301 53.6 0.646 848 147.2 0.220 289 57.2 0.611 802 150.8 0.211 277 60.8 0.578 759 154.4 0.202 266 64.4 0.546 717 158.0 0.194 254 68.0 0.518 683 161.6 0.186 244 71.6 0.490 643 165.2 0.178 234 75.2 0.467 613 168.8 0.170 223 78.8 0.446 5fc5 172.4 0.162 212 82.4 0.426 559 176.0 0.154 202 86.0 0.408 536 179.6 0.148 192 89.2 0.393 516 183.2 0.138 181 If3.2 0.378 496 186.8 0.130 170 96.8 0.3G3 478 190.4 0.122 160 100.4 0.350 459 194.0 0.114 149 1U4.0 0.338 444 197.6 0.106 139 107. 6-' 0.326 428 201.2 0.098 128 111.2 0.315 414 204.8 0.090 118 114.8 0.303 399 208.4 0.082 107 118.4 0.294 386 212.0 0.074 97 122.0 0.284 373 HEAT GENERATED BY ABSORPTION OF AMMONIA. The questions regarding the heat generated by the absorption of ammonia in water, as well as in water con- taining a certain percentage of ammonia, have been ex- perimentally studied by Berthelot, whose results may bo expressed by the following formula : C = if units. in which Q stands for the units of heat /pound Fahren- heit) developed when a solution containing one pound of ammonia in n pounds of water is diluted with a great amount of water. This equation fully suffices to solve the different problems arising in refrigerating prac- tice. Assuming 925 units (the values of different ex- perimenters differ) of heat to be developed when one pound of ammonia is absorbed by a great deal (say 200 pounds) of water, the amount of heat, Q, developed in making solutions of different strengths (one pound of ammonia to n pounds of water) may be expressed by the formula -I JO = 925 units. n 102 MECHANICAL REFRIGERATION. The heat, Q 2 , developed when b pounds of ammonia are added to a solution containing one pound of am- monia to n pounds of water, is expressible by the , = 9256 - units. Let the poor liquor enter the absorber with a strength of 10 per cent, which is equal to one pound of ammonia to nine (n) pounds of water. Let the rich liquor leave the absorber with a strength of 25 per cent, which is three (1+6) pounds of ammonia per nine (n) pounds of water. Inserting these values, n = 9 and b 2, in the above equation, we have 8 = 925 X 2 - = 1724 units. Hence by dissolving two pounds of ammonia gas or vapor in a solution of one pound of ammonia in nire pounds of water, we obtain twelve pounds of a 25 percent solution, and the heat generated is 1,724 B. T. units. SOLUBILITY OF AMMONIA IN WATER AT DIFFERENT TEM- PERATURES AND PRESSURES. (SIMS.) One Pound of Water (also Unit Volume], Absorbs tJie Following Quan- tities of Ammonia. Absolute Pr's'ure in Lbs. per Sq. Inch. 32 F. 68 F. 104 F. 212 F. Lbs. Vols. Lbs. Vols. Lbs. Vols. Gr'ms. Vol 14.67 0.899 1.180 0.518 .683 0.338 .443 0.074 .97 "" 15.44 0.937 1,231 0.535 .703 0.349 .458 0.078 .102 16.41 0.980 1.287 0.556 .730 0.363 .476 0.083 .109 17.37 1.029 1.351 0.574 .754 0.378 .496 0.088 .115 18.34 1.077 1.414 0.594 .781 0.391 .513 0.092 .120 19,30 .126 1.478 0.613 .805 0.404 .531 0.096 .126 20,27 .177 1.546 0.632 .830 0.414 .543 0.101 .132 21.23 .236 .615 0.651 .855 0.425 .558 0.106 .139 22.19 .283 .685 0.669 .878 0.434 .570 0.110 .140 23.16 .336 .754 0.685 .894 0.445 .584 0.115 .151 24.13 .388 .823 0.704 .924 0.454 .596 0.120 .157 2B.09 .442 .894 0.722 .948 0.463 .609 0.125 .164 26.06 .496 1.965 0.741 .973 0.472 .619 0.130 .170 27.02 .549 2.0H4 0.761 .999 0.479 .629 135 .177 27.99 .603 2 105 0.780 1.023 0.486 .638 28 95 656 2 175 801 1.052 493 647 3()'.SS !75S 2^309 0^842 1.106 0.511 !671 32.81 .861 2.444 0.881 1.157 0.5HO 696 34^74 1 966 2 '. 582 919 l!207 547 .718 36 'QI 2 07C 2!71 0^955 1^254 0^565 742 88 60 0^992 1^302 579 764 4o!fi8 0'.594 !780 The ammonia does not follow the absorption laws of Dalton, inasmuch as the quantity of ammonia absorbed by water does not vary directly with the pressure. PROPERTIES OF AMMONIA. 103 DIFFERENT SYSTEMS OF REFRIGERATION. Both the anhydrous liquor and the ammonia are used in refrigeration, the former in what is known as the Linde or compression system, and the latter in the Carr o or absorption system. TESTS FOR AMMONIA. As the boiling point of pure anhydrous ammonia is itt 29 below zero at a pressure of the atmosphere (30 inches of mercury), the purity of anhydrous ammonia may be tested by means of an accurate thermometer. The same is inserted into a flask containing the ammonia in a boiling condition, and provided with a tube to carry off the obnoxious vapor. If the boiling temperature differs materially from the above (allowance being made for the barometric pressure), it demonstrates that the ammonia is not pure. If after the ammonia is evapo- rated, an oily or watery residue is left in the flask, the same i3 also attributable to impurities. Ammonia leaks are generally easily detected by the smell or by the white fumes which form when a glass rod moistened with hy- drochloric acid is passed by the leak. If traces of ammonia are to be detected in water or in brine it is best to use "Nessler's Reagent, "which is prepared as follows: Dissolve 17 grams of mercuric chloride in about 300 cc. of distilled water; dissolve 35 grams of potassium iodide in 100 cc. of water ; add the former solution to the latter, with constant stirring, until a slight perma- nent red precipitate is produced. Next dissolve 120 grams of potassium hydrate in about 200 cc. of water ; allow the solution to cool ; add it to the above solution, and make up with water to one liter, then add mercuric chloride solution until a permanent precipitate again forms; allow to stand till settled, and decant off the clear solution for use ; keep it in glass stoppered blue bottles, and set away in a dark place to keep it from decomposing. The application of this reagent is very simple, a few drops of the same being added to the water or brine in question, contained in a test tube or a small glass of any other kind. If the smallest trace of ammonia is present a yellow precipitation of the liquid will take place, which turns to a full brown when the quantity of ammonia present is larger. 104 MECHANICAL REFRIGERATION. TESTING AMMONIA. The purity of anhydrous ammonia is practically tested by allowing the same to evaporate from a flask placed in water and provided with a cork and bent tube to carry off the obnoxious water. If after the evapora- tion a notable oily or watery residue is left it is attribut- able to impurities. The boiling point may be observed at the time (it is 29-30 F. below zero), and if any perma- nent gases are given off when the tube carrying off the ammonia vapor is discharged into water they may be tested for their inflammability. However, these latter two tests will hardly prove satisfactory except in the hands of an experienced chemist. In order to test the liquid residue in anhydrous am- monia, Faurot used a glass tube about six and one-half inches deep and one and one-eighth inches in diameter, and drawn out to a narrow tube at the bottom, the latter being divided in fractions of a centimeter, while the whole tube contains about 100 cubic centimeters. The open top may be closed with a rubber cork having a vent tube of glass, the outer portion of which is bent down close to the large tube, so that the whole may be placed in a glass of water after the tube has been filled to about half with the anhydrous ammonia to be tested. The ammonia will now boil away and be absorbed by the water in which the vent tube dips, and the amount or percentage of any residue that may be left can be readily estimated by the readings on the graduated portion of the tube. Permanent gases in the ammonia will manifest themselves by bubbles passing through the water. Ammonia liquor is tested for its strength by the hydrometer, as shown. For chemical tests it should be diluted with two times its volume of distilled water when, after acidification with hydrochloric acid, the addition of chloride of barium solution will show the presence of sulphates by a white precipitate. In the same diluted ammonia liquor clear lime water will show the presence of carbonates by a similar precipitation. Chlorides may be detected by acidifying the diluted am- monia solution with nitric acid and the addition of nitrate of silver solution by the formation of white pre- cipitate. If on the addition of nitric acid to the ammo- nia a red color appears it indicates traces of organic bases. WATER, STEAM, ETC. 105 CHAPTER III. WATER, STEAM, ETC. Water is a combination of one atom of oxygen with two atoms (one molecule) of hydrogen, consequently to be designated by H 2 O, which means that two parts by weight of hydrogen are combined with sixteen parts by weight of oxygen to form eighteen parts (one molecule) of water. FORMATION OF ICE. Water solidifies at 32 F., but in very fine capillary tubes the freezing point may be depressed for 20 or more. If rigidly confined or placed under pressure, the freezing point is depressed likewise. For a pressure of n atmospheres the freezing point is depressed for n X < i. 0135 F. Latent heat of ice, 142 B. T. units. PROPERTIES OF ICE. The ice which freezes out of solutions of salt OF other substance, consists of pure water, the impurities remain- ing in the unfrozen portion. Ice melts at 32 F., but by a pressure sufficiently high it can be converted into liquid at a temperature of 4 F. One cubic foot of ice weighs 998.74 ounces, avoirdupois. STEAM. Water volatilizes like any other liquid in accordance with the tension of its vapor, which at a temperature of 212 is equal to the tension of the atmosphere when the water boils, and is converted into steam, which occupies about 1,700 times the volume of the water. The water dis- sociates completely at a temperature of about 4.500, but a partial decomposition takes place at a lower tem- perature. SATURATED STEAM. When steam is still in connection with water, or if it is in such condition that a slight decrease of tempera- tare will cause liquefaction of some of the steam, it is called saturated steam. The pressure of saturated stea'm depends on its tem- perature in a manner approximately expressed by Ran- kine's formula: In which p is the pressure in pounds per square inch at the absolute temperature T in degrees F., the value of constants being : A = 6.1007, log. B = 3.43642, log. 0=5.- 69873. 106 MECHANICAL HEFUIGEKATION. TOTAL HEAT. By total heat of steam we understand that quantity of heat required to raise the temperature of unit weight of water from the freezing point to aqy given tempera- ture, and to entirely evaporate it at that temperature. The total heat, I, for any temperature, t, may be expressed by the formula: I =1091.7 4- 0.305 (t 32) LATENT HEAT OF VAPORIZATION. If the heat of the liquid, g (i. e., the amount of heat required to raise the temperature of unit weight of water from the freezing point to the temperature t) is sub- tracted from the total heat, I, at that temperature, we find the heat of volatilization, 7i, viz. : h=l g - EXTERNAL LATENT HEAT. That portion of the latent heat required to overcome external pressure, or the external latent heat, E, is expressed by tn which formula P stands for external pressure, v for the volume of the saturated vapor, v^ for the volume of the liquid, and /for the mechanical equivalent of heat. INTERNAL LATENT HEAT. The heat required to bring about the change from the liquid to the gaseous state, i. e., to perform the work of disintegration, or the so-called internal latent heat, F, is expressed by the equation F=h E SPECIFIC HEAT OF WATER. The specific heat, c, of water at any temperature, t (expressed in degrees Celsius), is c = 1 + 0.00004 t + 0.000000 t 2 See also table, page 16. SPECIFIC HEAT OF STEAM. The specific heat of superheated steam is 0.3643 at constant volume and 0.475 at constant pressure. The specific heat of saturated steam, s, is expressed by the equation WATER, STEAM, ETC. 107 which is negative for all values of T less than 1436 F.. above absolute zero. SPECIFIC HEAT OF ICE. The specific heat of ice is about half of that of wa- ter, or 0.5G4. PROPERTIES OF SATURATED STEAM, AT PRESSURE FROM ONE POUND TO 200 POUNDS ON THE SQUARE INCH. PRESSURE ABSOLUTE. HEAT, IN DEGREES, FAHR. #ly 11 || H tn Inches of I;i>;l li. fl Mercury at 32. Temperature. Latent Heat. Total Heat. 15'f 3,P iiS P- 1 Dif. Dif. prlb prlb 1 2.0375 102. 1,043.05 1,145.05 20,890 .0029 .037 5 10.1875 162.37 9126 1,001.9 1,163.46 2! 82 4,627 .0135 .167 20.375 193.29 4.93 979.60 1,172.89 1.50 2,429 .0257 .318 15 30.5625 213.07 3.47 965.85 1,178.92 1.05 1,669 .0373 .463 eo 40.75 228. 2.8 955.5 1,183.5 .8 1,380 .0487 .604 25 50.9375 240.2 2.3 947. 1,187.2 .7 1,042 .0598 .742 30 61.125 250.4 2. 939.9 1,190.3 .6 881 .0707 877 35 71.3125 259.3 1.7 933.7 1,193. .5 764 .0815 1.012 40 81.5 267.3 L5 928.1 1,195.4 .4 676 0921 1.142 45 91.6875 274.4 1.4 923.2 1,197.6 .4 608 .1025 1.272 50 101.875 281. 1.3 918.6 1,199.6 .4 552 .1129 1.402 55 112.0625 287.1 1.2 914.4 1,201.5 .4 506 .1232 1.529 60 122.25 292.7 1 1 910.5 1,203.2 .3 467 .1335 1.654 65 132.4375 298. t.l 908.8 1,204.8 .3 434 .1436 1.779 70 112.626 302.9 1. 903.4 1,206.3 .3 406 .1536 1.904 75 152.8125 307.5 .9 900.3 1,207.8 .3 381 .1636 2.029 to 163. 312. .9 897.1 1,209.1 .2 359 .1736 2.151 85 173.1875 316.1 .8 894.3 1,210.4 .3 340 .1833 2.271 90 J 83. 375 320.2 .8 891.4 1,211.6 .2 323 .1930 2.391 95 193.5625 324.1 .8 888.7 1,212.8 .3 307 .2030 S..51J. 100 203.75 327.8 886.1 1,213.9 .2 293 .2127 2 631 105 213.9375 331.3 ^Y 883.7 1,215.0 .2 281 .2224 2.751 110 224.125 334.6 .6 881.4 1,216.0 .2 269 .2319 2.871 115 234.3125 338. .6 879. 1,217.0 .2 259 .2410 2.990 120 244.5 341.1 .6 876.9 1,218.0 .2 249 .2503 3.105 254.6875 344.2 .6 874.7 1,218.9 .2 239 .2598 3.227 130 234.875 347.2 .6 872.6 ,219.8 .2 231 .2693 3.347 135 275.0625 350. .5 870.7 ,220.7 .1 223 .2788 3.467 140 2B5.25 352.9 .6 868.6 ,221.5 .1 216 .2883 3.582 145 295.4375 .6 866.8 ,222.4 .2 209 .2978 3.697 150 305.625 358.3 .5 864.9 ,223.2 .2 203 .3073 3.809 r>5 315.8125 360.9 .5 863.1 ,224. .2 196 .3168 3.927 JoO 326. 363.4 .5 861.4 ,224.8 .2 191 .3263 4.042 m 336.1875 BBS. 9 .5 859.7 ,225.6 .2 186 .3353 4.157 170 346.375 368.2 .4 858.1 ,226.3 .2 181 .3443 4.270 175 356.5625 370.6 .5 856.4 ,227. .1 176 .3533 4.383 IK) 366.75 372.9 .4 854.8 ,227.7 .1 172 .3623 4.495 IPS 376.9375 375. 3 .5 853.1 ,228.4 .1 168 .3713 4.607 190 387.125 377.5 .4 851.6 ,229.1 .1 164 .3800 4.720 195 3%. 3125 379.7 .4 850.1 ,229.8 .2 160 .3888 4.832 407.5 381.7 .3 848.6 1,230.3 .1 157 .3973 4.945 SPECIFIC VOLUME OF STEAM. The specific volume, v, of steam, in accordance with the experiments of Tate and Fairbairn, may be expressed by the formula _ oc o i 49513 1 " 108 MECHANICAL REFRIGERATION. VOLUME AND WEIGHT OF WATER. The volume of water does not change in direct propor- tion with the temperature, its greatest density being at 39 F., at which one cubic foot weighs 62.425 pounds. At 32 it weighs 62.418, at 62 it weighs 62.355, and at the boiling point it weighs 59.640 pounds. One cubic foot of water is generally taken at 62.5 pounds = 7. 48 U. S. gal- lons ; one cubic inch of water = .036 pounds ; one cubic foot of water = 6.2355 imp. gallons, or 7.48 U. S. gallons; one U. S. gallon of water = 8.34 pounds; one U. S. gallon of water = 231 cubic inches. PRODUCTION OF STEAM. The economical production of steam for industrial purposes is chiefly a question of fuel and the proper con- struction of boilers, grates, etc., and has been alluded to in the chapter 011 heat under the headings relating to fuel. For satisfactory arrangements as to boilers, etc., it may be assumed that one pound of fair average coal will produce about eight pounds of steam, more or less. WORK DONE BY STEAM. The theoretical ability of steam to do a certain amount of work is governed by the laws of thermody- namics above set forth, and the practical yield depends on a great many details in the mode of applying the force of steam practically, the consideration of which is beyond the limits of this treatise. For rough estimates, it is assumed that it requires from fifteen to thirty pounds of steam to produce a horse power, according to per- fection of engine, per hour. HEATING AREA OF BOILER. If H is the nominal horse power of a boiler and A the effective heating area of the same, Box finds that A nominal horse power requires from 0.6 to 1.2 square feet of grate surface between the limits of sixty and three horse powers. PRIMING. The water which is mechanically drawn over from the boiler with the steam is called priming, and may be determined in the following manner given by Clark. Blow a quantity of the steam, the amount of priming in which it is desired to ascertain, into a vessel holding a WATER, STEAM, ETC. 109 given weight of cold water, noting the pressure and the weight of the steam blown in, and the initial and final temperatures of the mixture. An addition is to be made to the initial weight of water, to represent the weight of water equivalent to that of the vessel containing the water, in terms of their respective specific heats. A cor- responding addition is to be made for such portion of the apparatus as is immersed in the water. Let W= weight of condensing water, plus the equiva- lent weight of the receiver and apparatus immersed in the water. w = weight of nominal steam discharged into the vessel under water. fF-f w = gross weight of mixture of nominal steam and condensing water. H = total heat of one pound of the steam, reckoned from the temperature of the condensing water. Hw = total heat delivered by the gross weight of nominal steam discharged, taken as dry steam. t = initial temperature of condensing water. t' = final temperature of condensing water. s augmentation of specific heat of water due to rise of temperature. L= latent heat of one pound of steam of the given initial pressure. Lw=: latent heat of steam discharged into the vessel, taking it as dry steam. P= weight of priming or moisture in percentage of the gross weight of nominal steam. (t f t + s)] Lw FLOW OF STEAM. The flow of steam through pipes takes place accord ing to Babcock after the following equation: \ TF=300 In which formula W is the weight of steam in pounds which will flow per minute through a pipe of the length L in feet and the diameter d in inches, when p t is the initial pressure, p z the pressure at end of pipe, and D the density or weight per cubic foot of the steam. 110 MECHANICAL REFRIGERATION. Steam of a pressure of fifteen pounds per square inch (gauge pressure) flows into vacuum with a speed of 1,550 feet per second, and into air with a speed of 650 feet per second. HYGROMETRY. Hygrometry is the art of measuring the moisture con- tained in the atmosphere, or of ascertaining the hygro- metric condition of the latter. AIR SATURATED WITH MOISTURE. The amount of aqueous vapor which can be held by a given volume of air increases with the temperature and decreases with the pressure. The air is called satu- rated with moisture when it contains all the moisture Which it can contain at that temperature. The degree of saturation or hygrometric state of the atmosphere is ex- pressed by the ratio of the aqueous vapor actually present in the air to that which it would contain if it were satu- rated. In accordance with Boyle's law the degree of saturation may also be expressed by the ratio of the elastic force of the aqueous vapor which the air actually contains to the elastic force of vapor which it would con- tain if saturated. ABSOLUTE MOISTURE. The absolute moisture is the quantity of aqueous vapor by weight contained in unit volume of air. DEW POINT. When the temperature of air containing moisture is lowered a point will be reached at which the air is satu- rated with moisture for that temperature, and a further lowering of temperature will result in the liquefaction of some of the moisture. This temperature is called the dew point. DETERMINATION OF MOISTURE. The moisture in the atmosphere may be determined by a wet bulb thermometer, which is an ordinary ther- mometer, the bulb of which is covered with muslin kept wet, and which is exposed to the air the moisture of which is to be ascertained. Owing to the evaporation of the water on the muslin the thermometer will shortly acquire a stationary temperature which is always lower than that of the surrounding air (except when the latter is actually saturated with moisture). If t is the temper- WATER, STEAM, ETC. Ill ature of tlie atmosphere and ^ the temperature of the wet bulb thermometer in degrees Celsius, the tension, e, of the aqueous vapor in the atmosphere is found by the formula e = Cl 0.00077 (t-tjht e t being the maximum tension of aqueous vapor for the temperature t t as found in table, and h the barometric height in millimeters. If e 2 is the maximum tension of aqueous vapor for the temperature t, the degree of saturation, H t is ex- pressed by e ~^ and the dew point is also readily found in the same table, it being the temperature corresponding to the tension e, TABLE SHOWING THE TENSION OF AQUEOUS VAPOR IN MILLIMETERS OF MERCURY, FROM 30 C. TO 230 C. Temp. Ten- sion. Temp. Ten- sion. Temp. Ten- sion. Temp. Ten- sion. ^30 .39 21 18.5. 94 610.4 105 907 -25 .61 22 19.7 94.5 622.2 107 972 10 .9 23 20.9 95 633.8 110 1,077 15 1.4 24 22.7 95.5 645.7 115 1,273 10 2.1 25 28.6 96 657.5 120 1.491 5 3.1 26 25.0 96.5 669.7 125 1,744 -2 4.0 27 26.6 97 682.0 180 2,030 1 4.3 28 28.1 97.5 694.6 135 2,354 4.6 29 29.8 98 707.3 140 2,717 1 4.95 30 31.6 98.5 721.2 145 3,125 2 5.3 35 41.9 99 732.2 150 3,581 a 5.7 40 55.0 99.1 735.9 155 4,088 4 6.1 45 71.5 99. 3 738.5 160 4,551 5 6.5 50 92.0 99.8 741.2 165 5,274 6 7.0 55 117.5 99.4 743.8 170 5,961 7 7.5 60 148.0 09.5 746 175 6,717 8 8.0 65 186.0 99.6 749.2 180 7,547 9 8.6 70 232.0 99.7 751.9 185 8,453 10 9.1 75 287.0 99.8 754." 190 9,443 11 9.7 80 354.0 99.9 757.3 195 10,520 12 in. 4 fl5 432.0 100 760 200 11,689 13 11.1 90 525.4 100.1 762. f 205 12,956 14 11.9 90.5 535.5 100.2 765.5 210 14,325 15 12.7 91 545.8 100.4 772.0 215 15,801 16 13.5 91.5 556.2 100. G 77H.5 220 17,39( J7 14.4 92 566.2 101 787.0 225 19,097 18 15.3 92.5 577.8 102 816 230 20,926 19 16.3 93 5:'iS.4 103 845 20 17.4 93.5 599.5 104 8*16 Degrees C. Atmospheres. .120 134 144 152 159 171 180 199 213 225 2 3 4 5 6 8 10 15 20 25 PSYCHROMETERS. Instead of the wet bulb thermometer alone it is more convenient to use two exact thermometers com- bined (one with a wet bulb and the other with a dry bulb, to give the temperature of the air) to determine 112 MECHANICAL REFRIGERATION, the hygrometric condition of the atmosphere or of the air in a room. Instruments on this principle can be readily bought, and are called psychrometers. If they are arranged with a handle, so that they can be whirled around, they are called "sling psychrometers." These permit a quicker correct reading of the wet bulb ther- mometer than the plain psychrometer, in which the thermometers are stationary and are impracticable at a temperature below 32 F., while the sling instrument can be read down to 27 F. The following table can be used to ascertain the de- gree of saturation or the relative humidity : RELATIVE HUMIDITY PER CENT. t (Dry Ther.) Difference between the dry and wet thermometers (t t'). yss 0.5 1.0 1.5 2.0 2. 5 3.0 3. 5 4.0 4. 6 5.r5.56.0 28 94 88 82 77 71 65 60 54 49 43 88 33 28 29 94 89 83 77 72 66 61 56 50 45 40 35 29 30 94 89 84 78 73 67 62 57 52 47 41 36 30 31 95 89 84 79 74 68 63 58 53 48 43 38 31 32 95 90 84 79 74 69 64 59 54 50 45 40 32 33 95 90 85 80 75 70 -65 60 56 51 47 42 33 34 95 91 86 81 75 72 67 62 57 53 48 44 31 35 95 01 86 82 76 73 69 65 59 64 50 45 35 36 96 91 86 82 77 73 70 66 61 56 51 47 36 3V 96 91 87 82 78 74 70 66 62 57 53 48 37 38 96 92 87 83 79 75 71 67 63 58 54 50 38 39 96 92 88 83 79 75 72 08 63 59 55 52 39 40 96 92 88 84 80 76 72 68 64 60 56 53 40 The hygrometer of Marvin is a sling psychrometer of improved and approved construction. HYGROMETERS. While the term hygrometer applies to all instruments calculated to ascertain the amount of moisture in the air, it is specifically used to design instruments on which the degree of humidity can be read off directly on a scale without calculation and table. Their operation is based on the change of the length of a hair or similar hygro- scopic substance under different conditions of humidity. DRYING AIR. To remove moisture from air more or less saturated with it, certain so called hygroscopic substances which have a great affinity for water may be applied. Chloride of calcium, dried at a dull red heat and powdered, may be WATER, STEAM, ETC. ;Q3 used for this purpose, and when spread in a layer %-inch thick and exposed to air at 48 F., with a humidity of 0.75, will absorb per square foot surface in each one of seven succeeding days the following amounts of moist- ure: 1,368, 1,017, 958, 918, 900, 802 and 703 grains respect- ively (Box). VAPORIZATION. The vaporization of water into the air depends on the hygrometric state of the atmosphere, and its amount in grains, _R, per square foot and 'per hour with air per- fectly calm, may be expressed according to Box by the following rule: E =s (e. t e )l5 When the air into which the water evaporates is in motion the evaporation proceeds much faster, thus : For a fresh breeze #=(e t _e)66 for a strong wind tf=(e 2 and for a gale JR=(e 2 e)188. The refrigeration which is produced by the vaporiza- tion of water into the air is about 900 B. T. units for each pound of water evaporated, or 0.117 units per grain of water evaporated. PURITY OF WATER. As natural water is never absolutely pure it is fre- quently of importance to ascertain the degree of purity of a water for certain purposes. The requirements to be made in regard to the purity of a water vary with the purposes for which it is to be used ; water may be very good for drinking purposes, but at the same time it may be too hard for boiler feeding ; and on the other "hand a water may be good for boiler feeding, yet it may be too impure (bacteriologically) for drinking purposes. Similar dis- tinctions obtain in other respects, so that it is impracti- cable to give general rules for the valuation of a water, unless they are based on an exact chemical analysis of the same. The crude chemical tests which are fre- quently recommended in this connection are of little or no value in most cases, and more frequently they are misleading. They generally only give qualitative indi- cations, but in order to be able to judge a water correctly the relative quantities of its constituents must be known. 114 MECHANICAL REFRIGERATION. CHAPTER IV. THE AMMONIA COMPRESSION SYSTEM. GENERAL, FEATURES. The refrigeration in this system is brought about by the evaporation of liquid anhydrous ammonia, which takes place in coils of pipe termed the expander or refrig- erating coils. These coils are either placed in the rooms to be refrigerated, or they are immersed in a bath of salt brine, which absorbs the cold. The salt brine is circu- lated in pipes through the rooms to be refrigerated by means of a pump. The ammonia, after having expanded, is compressed again by means of a compression pump called the compressor into another system of pipes called the condenser. The condenser -is cooled off by running water, which takes away from the ammonia in the coil a the heat which it has acquired through the compression, as well as the heat which it has absorbed while having evaporated in the expander. Owing to both pressure and withdrawal of heat, the ammonia assumes its liquid form again to pass again into the expander, thus repeating its circulation* over and over again. THE SYSTEM A CYCLE. The refrigerating contrivance above described em- bodies a perfect cycle of operations. The working sub- stance, ammonia in this case, returns periodically to its original condition. During each period a certain amount of heat, partly in the refrigerator and partly during COEI- pression (from work converted into heat), is added to tt.e working substance and an exactly equivalent amount is abstracted from the working substance in the condenser by the cooling water. THE COMPRESSOR. The compressor is a strongly constructed cylinder in which a piston moves to and fro, having a valve through which the expanded ammonia from the refrigerating coils enters and another through which it is. forced into the con- denser. A double-acting compressor has two valves at each end of the compressor cylinder, and the packing for the piston rod must be made sufficiently long and tight to withstand the pressure of the ammonia. The com- pressor, like all other parts of the ammonia system, must be made of steel and iron, no copper or brass being admissible. THE AMMONIA COMPRESSION SYSTEM. H5 During the compression stage a certain amount of heat is evolved. If not otherwise stated, it is assumed in the following discussion, that enough heat is removed during compression to keep the vapor always in a satu- rated condition. REFRIGERATING EFFECT OF CIRCULATING MEDIUM. To arrive at numerical value- of the quantities in- volved in the refrigerating process we may first determine the theoretical refrigerating effect, r, of the circulating medium. If t be the tempera* ure of the condenser, that is, the temperature of the cooling water leaving the condenser; if ti be the temperature of the refrigerator, that is, the temperature of the brine leaving the refrigerator; if s is the specific heat of the circulating liquid, and if /i t is the latent heat of vaporization of one pound of the circulating medium in thermal units at the temperature t , we find the refrigerating effect, r, of one pound of the circulating fluid, expressed in thermal units after the following formula: r=hi (t t ) s The term (t x ) s represents the refrigeration re- quired to reduce the temperature of the circulating fluid from the temperature t to the temperature t . Practically speaking, the temperature of the ammonia in condenser will always be a few degrees higher than the water leaving the condenser, and the ammonia in refriger- ating coil will always be a few degrees (5 to 10) lower than the outgoing brine. WORK OF COMPRESSOR. If the cycle of operation was a perfect reversible one, the work required from the compressor for every pound of the liquid circulating would be to lift 'the amount of heat, r, from the temperature t to the temperature t. As explained already, this is not the case, and the whole amount of heat as represented by the latent heat of vap- orization, namely, h lt is to be lifted by the compressor through the range of temperature indicated. Hence the work theoretically required from the compressor ex- pressed in thermal units, TF, is therefore T representing the temperature of the refrigerator ex pressed in degrees of absolute temperature ( t t + 460 ), 116 MECHANICAL REFRIGERATION. HEAT TO BE REMOVED IN THE CONDENSER. The theoretical number of heat units, D, which would have to be removed by the condenser water per pound of refrigerating fluid in circulation in the system, if the circulating fluid in compressor were always kept in a saturated condition from without by removing the surplus heat, could be expressed as follows: D = h, h being the latent heat of volatilization of one pound of the circulating liquid at the temperature of condenser (t). The whole amount of heat, D , to be removed when including that which would cause superheating of the fluid in compressor, may be theoretically expressed as follows: t t* Dj = jr^+ftt s(t tj. AMOUNT OF SUPERHEATING. The amount of heat, $, liable to cause superheating may therefore be expressed by the formula S = D t D, or COUNTERACTING SUPERHEATING. The surplus heat in compressor is removed in various ways : by injecting refrigerated oil, by surrounding the compressor with a cold water jacket, or by carrying liquid ammonia into the compressor, etc. While there is no doubt as to the advisability of preventing super- heating as much as possible, the theoretical discussions regarding the relative merit of these expedients do not quite agree among themselves, nor with practical expe- rience, and it would appear that besides theoretical con- siderations certain practical points have some bearing on this question, especially the degree to which the preven- tion of superheating is effected. AMOUNT OF AMMONIA IN COMPRESSOR. The additional amount of liquid ammonia that would have to be carried into the compressor with every pound of ammonia vapor entering the same, in order to keep the latter saturated during compression, may be ex- pressed by the formula P _ JL in which P stands for pounds of liquid ammonia BO re- quired. THE AMMONIA COMPRESSION SYSTEM. 117 NET THEORETICAL REFRIGERATING EFFECT. The ammonia required to keep the vapor saturated in compressor has to be cooled down from the tempera- ture t to the temperature ,, and the refrigeration is re- duced to that extent. Accordingly the net refrigerating effect, r , of every pound of circulating liquid volatilized in refrigerator, in case of wet compression is expressed by the formula: VOLUME OF THE COMPRESSOR. The volume of the compressor is expressed by the amount of space through which the piston travels each stroke. If r be the radius of the compressor and b the length of stroke in feet, the active volume of the com- pressor, V, is V= r 2 X b X 3.145 cubic feet. If r and b are expressed in inches the formula would become CUBIC CAPACITY OF COMPRESSOR. The cubic capacity of a compressor may be expressed by the amount of space which the piston travels through in one minute, only one way being counted in a single- acting, and both ways being counted for each revolution in a double-acting compressor. If ra is the number of revolutions per minute, r the radius and b the length of stroke in feet of a compressor, the capacity of the sam , O, if single-acting, is expressed by the formula : C = r 2 x3.145x&Xm cubic feet per minute; if double-acting, it is twice that. If r and b are given in inches, the product must be divided by 1,728 to find (7. CLEARANCE. As the piston does not exactly touch the cylinder ends, leaving always more or less dead space called clear- ance, the whole of the above capacity is not available on this account, and from 5 per cent to 7 per cent may be deducted from it for clearance. This may be called the reduced capacity of the compressor. 118 MECHANICAL REFRIGERATION. The exact percentage of clearance depends on a number of conditions, and may be approximately deter- mined after the following equation: F In this equation G is the theoretical capacity of a compressor, and C t the corrected or reduced capac- ity in accordance with clearance. F is the volume traversed by piston in each stroke in cubic feet, n the actual clearance space left between piston and cylinder in cubic feet, w and w t the weights of equal volumes of ammonia at the pressure in condenser and refrigerator respectively. REFRIGERATING CAPACITY OF COMPRESSOR. The refrigerating capacity of a compressor does not alone depend on its cubic capacity, but also OD surround- ing circumstances, especially the temperature in con- denser and refrigerator coils, and can, therefore, not be exactly determined without these data. For rough esti- mates it may be assumed, however, that under quite frequently prevailing conditions a cubic compressor capacity per minute of four feet will be equivalent to a capacity of one ton refrig. in twenty -four hours. (Fifty- six inches double-acting compressor capacity sixty revo- lutions. ) If (/! is the reduced compressor capacity per minute (that is, G less clearance) the corresponding re- frigerating capacity, _K, expressed in tons of refrigera- tion in twenty-four hours, maybe found after the follow- ing formula: T? ___ C t X 36 X r or approximately - (1. V v tons. In this formula v stands for the volume of one pound of ammonia vapor in cubic feet at the temperature of the refrigerator ; the sign r stands for the maximum theoretical refrigerating capacity for each pound of am- monia passing the compressor. The refrigerating capacity of a compressor, expressed in thermal units, JB lt per hour, is THE AMMONIA COMPRESSION SYSTEM. Hg AMMONIA PASSING THE COMPRESSOR. The amount of ammonia, K, in pounds passing the compressor per minute is expressible thus: K= C t X w pounds, in which C t stands for the reduced compressor capacity per minute and w for the weight of one cubic foot of ammonia vapor at the temperature of the refrigerator or expansion coils. NET REFRIGERATING CAPACITY. As the last four formulas allow for clearance, but not for other losses, it is more convenient and practically sufficiently correct in most cases to substitute in these formulas Cfor d, and reduce the refrigerating capacity so found by 15 per cent, which should be ample for all losses, and give net refrigerating capacity. HORSE POWER OF COMPRESSOR. If W= ~^ * h t (in thermal units) is the power re- quired by the compressor to lift the heat which became latent by the evaporation of one pound of ammonia in refrigerator, as shown before, and if K represents the amount of ammonia vapor entering the compressor per minute, the work to be done by the compressor per min- ute, W lt expressed in thermal units, is W t = W XK units. If expressed in foot-pounds, W 2 , it is W 2 =778 W X Jf foot-pounds. And if expressed in horse powers, W 3 , it is ITOQ W * = 330QO == ' 0234 WK horse P wer - W a = 0.0234 ~p l hj xCXw horse power. SIZE OF COMPRESSOR. In order to determine the size of a compressor for a given refrigerating duty it is advisable to reduce the latter to an expression of heat units to be removed per hour; and if the same is upderstood to represent actual refrigerating capacity, some 15 per cent or more, ac- cording to circumstances, should be added for clearance and other losses, and in case the refrigerating capacity is r equired in the form of manufactured ice it should at 120 MECHANICAL REFRIGERATION. least be doubled. The reduced refrigerating duty so obtained we will call r 2 , v the volume of one pound of ammonia gas at the temperature of the outgoing brine, r t the refrigerating effect of one pound of ammonia for the temperatures employed, Fthe active volume swept over by the piston in each revolution (two times the volume of compressor if the same is double-acting), and m the number of revolutions per minute. Signs having this meaning, the following equations obtain: In this case Vm signifies the compressor capacity per minute. If m is given F= gn r * v cubic feet. 60 X ?*! m It Vis given NUMBER OF REVOLUTIONS AND PISTON AREA. The number of revolutions of compressor varies with its size from forty to eighty revolutions per minute. When the compressor is worked directly by a steam en- gine, as is generally the case, the number of revolutions of the compressor is governed by those of the engine, and the area of the compressor piston must be in ac- cordance with that of engine piston. The product of average pressure on engine piston with the area of the latter must always be greater than the product of the compressor piston area multiplied by the pressure in con- denser coil if both the engine and compressor piston have the same length of stroke. If the stroke of com- pressor piston is shorter than that of engine piston its area can be made correspondingly larger. USEFUL AND LOST WORK OF COMPRESSOR. That part of the work of the compressor which is ex- pressed by the foregoing equations for W, TF 2 or W 3 may be considered as useful work of the compressor, while what work is done by the compressor in excess of that amount, due to superheating, friction and other causes, may be considered as lost work. The smaller the lost work the more perfect is the operation of the com- pressor. THE AMMONIA COMPRESSION SYSTEM. 121 DETERMINATION OF LOST WORK. The lost work of a compressor may be determined in various ways, directly by interpretation of the indicator diagram and also indirectly in some cases. The lost work is the difference between the actual work done by the compressor and that theoretically required of the same, or expressed by formula, L standing for lost work in thermal units and W e for actual compressor work in thermal units: L=W 6 -W INDIRECT DETERMINATION OF ACTUAL WORK. In a machine with submerged condenser, the actual work, W Q , of the compressor may be approximately de- termined in T. U. per hour after the following formula: W 6 = (T-T 1 )p-(t-t 1 )gs 1 in which formula T is the temperature of outgoing, T t the temperature of incoming condenser water, t the tempera- ture of cold brine, t^ the temperature of returning brine, p the number of pounds of condensing water used per hour, g the number of pounds of brine circulated per hour, and s the specific heat of the brine. The actual compressor work found in this manner will be somewhat larger than that found from the indi- cator diagram, since it includes the lost work due to fric- tion in the compressor. Allowance must also be made for amount of superheating neutralized otherwise than by condenser water. HORSE POWER OF ENGINE. The work required to operate the compressor, whether furnished by engine direct or by transmission and gear- ing, must be equal, or rather somewhat greater than the actual work of the compressor: It must exceed the work shown by the indicator by at least the amount due to friction of piston, etc. It is safe to assume that the in- dicated horse power of an engine, TF 7 , necessary to pro- pel a compressor of a theoretical horse power, W 3 , is at least about W 7 = 1.4 W 3 horse power. In defective machines it may be more; seldom, how- ever, it will be less. WATER EVAPORATED IN BOILER. The amount of water evaporated in boiler (for non- condensing engine) may be approximately estimated on 122 MECHANICAL REFRIGERATION. the basis that twenty-five pounds of water are needed per hour per horse power in a well regulated boiler. The amount of water, A, evaporated for twenty -f our hours is, therefore A = 25 X 24 X W 7 pounds. COAL REQUIRED. If one pound of coal evaporates n pounds of water the amount of coal, JP, required in twenty-four hours is ap- proximately _, 25 X 24 X TF 7 F - ^ - pounds. In a non-condensing engine about fifteen pounds of water are used per horse power per hour, and the foregoing formula in that case reads F = - pounds. n differs for various kinds of fuel, but may be assumed equal to 8 for fair average coal. EFFICIENCY OF COMPRESSOR. The term efficiency covers a variety of meanings, and the meaning ought to be expressed clearly in each case. Generally efficiency is expressed by the number of units of heat removed from the refrigerator for every thermal unit of work done by compressor, which is also expressed by the quotient p_ Heat removed in refrigerator Work done by compressor in T. U. This may be called the actual efficiency for a given case. As it varies not only with the machine, but also, and most decidedly so, with the local condition under which it works (temperature of refrigerator and con- denser) it affords no criterion as to the lost work done by the compressor, i. e., it is not an expression for the degree of perfection of the compressor. In order to obtain an expression for this quality we must, according to Linde, compare the actual efficiency uf a plant with the maximum theoretical efficiency of the plant when working under the same condition. The maximum theoretical efficiency, E 2 , is expressed by Linde through the formula T E 2 = T r THE AMMONIA COMPRESSION SYSTEM 123 As we have seen above, this should more properly be substituted by the maximum theoretical efficiency, E^ as explained in the above, at least if machines with the same circulating medium are to be compared, viz.: h t (tt t )s OT &= If JB stands for the heat actually removed in refrig- eration and Q for work actually performed by compressor, as ascertained by actual observation or test, we have for the actual efficiency, J5, the expression The ratio or proportion, w, between the actual and the theoretical capacity is therefore E W=-H- &1 or if we insert the expressions found above flM*-*i) QTlhi-stf-tJ] DIFFERENT KINDS OF COMPRESSORS. There are many constructive details in valves, etc., in the different makes of compressors which it is impracti- cable here to discuss. The principal difference, how- ever, is due to the different methods in which super- heating of the gas during compression is prevented or to whether the compressor is horizontal or vertical, double or single-acting, etc. By way of example we mention only a few typical ones. THE LINDE COMPRESSOR. This compressor is principally used for wet compres- sion, the peculiarities of which have been mentioned above ; it is a horizontal double-acting compressor with a deep packing, having a length of twelve inches or more in order to withstand the pressure of some 150 to 180 pounds. Since ammonia attacks India rubber, the best rubber packings for compressors are inlaid with cotton. Selden's, Oarlock's and Common Sense packing are also used. 124 MECHANICAL REFRIGEKATION. The Boyle compressor is vertical and single-acting, compressing only on the up stroke. The gas has free en- trance to and exit from the cylinder below piston, calcu lated to keep cylinder and piston cool. The extreme lower portion of the pump forms an oil chamber to seal the stuffing box around piston. THE DE LA VERGNE COMPRESSOR. This compressor is also a vertical compressor, and superheating is counteracted by means of refrigerated oil, which is circulated through the compressor by means of a small pump. Another object of the oil is that its presence ahead dnd behind the piston abolishes the evil effects of clearance, or at least lessens the same mate- rially. It furthermore affords excellent lubrication of the moving parts and helps to make the piston tight. THE WATER JACKET COMPRESSOR. This form of compressor is mostly vertical, its pecul- iarity being that the superheating is prevented by circu- lating cold water or brine through a water jacket which surrounds the compressor. These compressors are frequently single-acting; in this case a shorter stuffing box (causing less friction) for piston rod may be used, since the pressure on the stuffing box is seldom more than thirty pounds. TABLE SHOWING REFRIGERATING EFFECT OF ONE CUBIC FOOT OF AMMONIA GAS AT DIFFERENT CONDENSER AND SUCTION (BACK) PRESSURE IN B. T. UNITS. 1 C d Temperature of the Liquid in Degrees P. O 01 C G ife 65 70 75 80 85 90 95 100 105 la Pi Correspg. Condenser Pressure (gauge) Ibs. per sq. in. O3I-3 OQ 103 115 127 139 153 168 184 200 218 27 G. Pres 27.30 27.01 26.73 26.44 26.16 25.87 25.59 25.30 25.02 20 4 33.74 33.40 33.04 33.70 32.34 31.99 31.64 31.30 30.94 15 6 3t5.36 36.48 36.10 35.72 35.34 34.96 34.58 34.20 33.82 10 g 42.28 41.84 41.41 40.97 40.54 40.10 39.67 39.23 38.80 5 13 48.31 47.81 47.32 46.82 46.33 45.83 45.34 44.84 44.35 16 54.88 54.32 53.76 53. 2U 52.64 52.08 51.52 50.96 50.40 5 20 61.50 60.87 60.25 59.62 59.00 58.37 57.75 57.12 56.50 10 24 68.66 67.97 67.27 66.58 65.88 65.19 64.49 63.80 63.10 15 28 75.88 75.12 74. 3 1 73.59 72.82 72.06 71.29 70.53 69.76 20 33 85.15 84.30 83.44 82.59 81.73 80.88 80.02 79.17 78.31 25 39 95.50 94.54 93.59 92.63 91.68 90.72 89.97 88.81 87.86 30 45 106.21 105.15 104.09 103.03 101.97 100.91 99. &5 98.79 97.73 35 61 115. S 114.54 123.39 112.24 111.09 109.94 108. 79 107.64 106.49 THE AMMONIA COMPRESSION SYSTEM. 125 TABLE GIVING NUMBER OF CUBIC FEET OF GAS THAT MUST BE TUMPED PER MINUTE AT DIFFERENT CONDENSER AND SUCTION PRESSURES, TO PRODUCE ONE TON OF REFRIGERATION IN 24 HOURS. a 2 bcSjj Temperature of the Gas in Degrees' F. of S !3 8 "5 65 70 75 80 85 90 95 100 105 *- be 03 o> II I |Q 05 Correspg. Condenser Pressure (gauge) Ibs. per sq. in. D. J3 17.475 0.829 19.990 24.299 7.20 14.567 6 6.065 6.625 0.280 19.054 20.813 0.577 28.889 34.471 4.98 18.764 7 7.023 7.625 0.301 22.063 23.954 0.505 38.737 45.663 3.72 28.410 8 7.982 8.625 0.322 25.076 27.096 0.444 50.039 58.426 2.88 28.348 9 9.001 9.688 0.344 28.277 30.433 0.398 63.653 73.715 2.26 34.677 10 10.019 10.65 0.366 31.475 33.772 0.355 78.838 90.793 1.80 40.641 THE AMMONIA COMPRESSION SYSTEM. 137 DIMENSIONS OF EXTRA STRONG PIPE. A table giving dimensions of extra strong pipe will be found in the Appendix. BRINE SYSTEM. In the brine system the expansion coils, as stated, are placed in separate vessels containing salt brine, which is cooled down to the desired degree. The brine so cooled is then conducted through pipes located in the rooms to be refrigerated by means of force pumps. In ice making the cells or boxes containing the water for ice making are suspended in the brine tank. SIZE OF PIPE IN BRINE TANK. The amount of piping allowed in brine tank is also a matter of practical experience. Generally 120 to 150 running feet of 1^-inch pipe are allowed per ton of re- frigerating capacity (in 24 hours) in brine tank for gen- eral refrigeration. In case of ice making 250 to 300 running feet of 1^- inch pipe are allowed in brine tank per ton of ice to be manufactured in twenty-four hours. TABLE OF BRINE TANKS AND COILS. The following table shows the dimensions of some brine tanks and coils for different capacities, expressed in tons of refrigerating capacity (not ice making capacity). Capacity In Tons Refrigera- tion. 25 tons 35 " .... 60 " .... 75 " . . Average per ton. S.2 ?" 13 13 13 15 CO^ fl w y :-= !| fl a . 05-* ft 1,664 3,080 2,730 4,785 q O t*o3 fa o3EH 3il GM -os . j5 o o SS'iS 180.7 PIPES FOR BRINE CIRCULATION. In the case of brine circulation there must be another series of coils in rooms to be refrigerated, through which the brine circulates, as the brine does not circulate as fast as the ammonia vapor, and for other reasons the surface of brine coils in storage rooms must be much 138 MECHANICAL REFRIGERATION. larger than in case of direct expansion under conditions otherwise similar. In round figures it-is generally assumed that the area of pipe surface incase of brine circulation should be from one and one-half to two times as large as in case of direct expansion. RULES FOR LAYING PIPES. The pipes in storage rooms should be placed where they are least in the way. They should be arranged in independent sections con- nected by manifolds in such a way that each section can be shut out to throw off the frost. TABLE FOR EQUALIZING PIPES. The size of main pipe is given in the column at the left. The number of branches is given in the li ne on top, and the proper size of branches is given in the body of the table on the line of each main and beneath the de- sired number of branches. In commercial sizes the normal 13^-inch pipe is gen- erally over size; often as large as 1%. It is safe to call it 1.3 inches, and it is so figured in the table. Exact sizes are given for branch pipes. The designer of the pipe system can thus better select the commercial sizes to be used. Size of Main Pipe. NUMBER OF BRANCHES. 2 3 4 5 6 7 8 9 10 1 in. .758 .644 .574 .525 .488 .459 .435 .415 .398 1^4 " .986 .838 .747 .683 .635 .597 .556 .540 .618 m " 1.14 .967 .861 .788 .733 .689 .653 .623 .597 2 " 1.53 1.29 1.15 1.05 .977 .918 .870 .830 .796 2J6 " 1.89 1.61 1.44 1.31 1.22 1.15 1.09 1.09 .995 3 " 2 27 1.93 1.72 1.58 1,47 1.38 1.31 1.25 1.19 3^ " 2 (55 2.26 2.01 1.84 1.71 1.61 1.52 1.45 1.39 4 " 3.03 2.58 2.30 2.10 1.95 1.84 1.74 1.66 1.59 4 1 /, " 3.41 2.90 2.58 2.36 2.20 2.07 1.96 1.87 1.79 5 " 3.79 3.22 2.87 2.63 2.44 2.30 2.18 2.08 1.99 6 " 4.55 3.87 3.45 3.15 2.93 2.75 2.61 2.49 2.39 7 " 5.30 4.51 4.02 3.68 3.42 3.21 3.06 2.91 2.79 8 " 6.06 5.16 4.59 4.20 3.91 3.67 3.48 3.32 3.18 9 ' 6.82 5.80 5.17 4.73 4.40 4.13 3.92 3.74 3.58 10 " 7.58 6.44 5.74 5.25 4.88 4.59 4.35 4.15 3.98 12 " 9.08 7.73 6.89 6.80 5.86 5.51 6.23 4.98 4.78 In brine circulation the brine should also be pumped through series of pipes running in the same direction, and connected by manifolds to decrease friction. Further information in regard to piping rooms, etc., will be found in the chapters on Cold Storage, Brewery Refrigeration, etc. THE AMMONIA COMPRESSION SYSTEM. Diameter of Pump Barrel, In Inches. -3 BH III! +_. ct> C . Kl Ct> CD *"* CD & P* lilt fl! B o p fls 3Q o o' tf 03 P O III it coco*-- CNCiO ( ' os 01 *- cc . o cc t^ ct cr. ta os >*i < CC~J03WC005mi 00 S O S W hi GO 05 f^ CO C K> M. - fX ^ 5 X? ^ S pJ "^" ^ *^ t^" SiJ ^T 5 2 ^ M 03 to 00 05 W >P>- OS 13 M h-. > (-1 g CO O CJt -7 os K, 1C Or CC ^ H- O M CO O -1 Or C " i" = S c - i' 5o WO So l'< r." i^ S c5 ' -i o O5 co to INS i o ov n os ~ -~ t ^ f CT: J v ^ I CJt CC Jiiw / li ^ .- '/ / JO O tO GO O5 O3 K) t-* ) WOS^^CCrf^OOCCiC^rf^OiO-^TCiQC^h-^CitCQOC^ P. C[j ac ^- oe co o i tC'Ol>3'Xi--l fc: JO*H-' 139 H ! i 140 MECHANICAL REFRIGERATION. THE BRINE PUMP. The circulation of the refrigerated brine through the refrigerating coils in storage rooms, etc., is accomplished by the brine pump. The size of the brine pump may be estimated on the basis that the brine should not travel faster than sixty feet per minute. The table on opposite page will be found convenient in this connection. PREPARING BRINE. The brine is a solution of some saline matter in water, in order to depress the freezing point of the latter. Gen- erally chloride of sodium or common salt is used for this purpose. To make the brine it is well to use a water tight box, 4x8 feet, with perforated false bottom and com- partment at end, with overflow pipe for brine to pass off through a strainer. The salt is spread on false bottom, and the water fed in below the false bottom as fast as a solution of the proper strength will form. A wooden hoe or shovel may be used for stirring to accelerate solution. TABLE SHOWING PROPERTIES OF SOLUTION OF SALT. (Chloride of Sodium.) Percentage of Salt by Weight. Pounds of Salt per, Gallon of Solution. gS fc o gs EftSs 4 eg w Qcn l^d Po3o ^fllT a o WQrv; lr 8 Specific Gravity at 39 F. = 4 O. i ii 02 Freezing Point, Fahreneit. Freezing Point, Celsius. || 1 0.084 4 8.40 ! .007 0.992 30.5 0.8 2 0.169 8 8.46 .015 0.984 29.3 1.5 2.6 0.212 10 8.50 : .019 0.980 28.6 1.9 3 0.256 12 8.53 .023 0.976 27.8 2.3 3.5 0.300 14 8.56 .026 0.972 27.1 2.7 4 0.344 16 8.59 .030 0.968 26.6 3.0 5 0.433 20 8.65 .037 0.960 25.2 -3.8 6 0.523 24 8.72 .045 0.946 23.9 4.5 7 0.617 28 8.78 .053 0.932 22.5 5.3 8 0.708 32 8.85 .Obi 0.919 21.2 '6.0 9 0.802 36 8.91 .068 0.905 19.9 6.7 10 0.897 40 8.97 .076 0.892 18.7 7.4 12 1.092 48 9.10 .091 0.874 16.0 8.9 15 1.389 60 9.26 .115 0.855 12.2 11.0 20 1.928 80 9.64 .155 0.829 6.1 14.4 24 2.376 96 9.90 .187 0.795 1.2 17.1 26 2.488 100 9.97 .196 0.783 0.5 17.8 26 2.610 104 10.04 .204 0.771 1.1 18.4 STRENGTH OF BRINE. Generally speaking, the brine must contain sufficient salt to prevent its freezing at the lowest temperature in freezing tank, and by referring to the accompanying table one can answer the question for himself on this basis very readily. THE AMMONIA COMPRESSION SYSTEM. 141 To determine the weight of one cubic foot of brine multiply the values given in column 4 by 7.48. To determine the weight of salt to one cubic foot of brine multiply the values given in column 2 by 7.48. POINTS GOVERNING STRENGTH OF BRINE. Therefore if the temperature in the freezing tank does not go below 15 F., it would be quite sufficient to use a brine containing 15 per cent of salt (salometer de- grees 60), as from the above table it appears that such a solution does freeze below that temperature. On the other hand, if the temperature of freezing does not go below 20 F., a brine containing only 10 per cent salt would be sufficient for the same reason, etc. This table also ex- plains why it would be irrational to use stronger solutions of salt than these, for, as we see from the column show- ing specific heat, the same grows smaller as the concen- tration of the brine increases, and consequently the stronger the brine the less heat a given amqunt of brine will be able to convey between certain definite tempera- tures. There is another danger connected with the use of too strong, especially of concentrated, brine in refrig- eration. Such brine may cause clogging of pipes, etc., on account of depositing salt. This danger, however, is not so great as that of having the solution too thin, for while it may be concentrated enough not to freeze iu the brine tank, it may be still too weak to withstand the tempera- ture obtaining in the expansion coil, so that a layer of ice will form around the latter which interferes with the prompt absorption of heat from the brine. For this rea- son the surface of the expansion coils in brine tank should be inspected from time to time to see if any ice has formed on them. SIMPLE DEVICE FOB MAKING BRINE. An ordinary barrel with a false bottom three inches above the real bottom, perforated with 3^ -inch holes, is a practical contrivance for making brine. The space above the false bottom is filled with salt nearly to the top of the barrel. Ordinary water is admitted below the false bottom, and the ready brine runs out at the top through a pipe, which is best inclosed in a wire screen filled with sponges. The pipe carrying off the brine should be about %-inch larger than the pipe admitting the water. 142 MECHANICAL REFRIGERATION. SUBSTITUTE FOR SALOMETER. In case one is unable to readily obtain a salometer, a Beaume hydrometer, or a Beck hydrometer scale, both of which are in quite general use for taking the strength of acids, etc., can be used as well. Their degrees compared with specific gravity and percentage of salt are shown in the following table, and, as will be seen, do not differ so very much from the degrees of the salometer scale : Percentage of Salt by Weight. Specific ' Gravity. Degrees on Beaume's scale, 60 F. Degrees on Beck's scale, COo F. 1 5 10 15 20 25 1.0000 1.0072 1.0362 1.0733 1.1114 1 . 1511 1.1923 1 5 10 15 19 23 1.2 6 12 17 23 28 CHLORIDE OF CALCIUM. Some engineers prefer to use chloride of calcium for the preparation of brine in preference to common salt. It is higher in price than the latter, but is said to keep the pipes cleaner, causing less wear and a better conduc- tion of heat. The physical properties of the chloride of calcium solution, as appears from the subjoined table, are quite similar to those of common salt. The freezing point, however, can be depressed several degrees lower by the use of the former, and for this reason the use of chloride of calcium may be advisable in such extreme cases. Other- wise the preparation of the solution of chloride of cal- cium is the same as that of ordinary brine. PROPERTIES OF SOLUTION OF CHLORIDE OF CALCIUM. Percentage by Weight. Specific Heat. Spec. Grav. at 60 F. Freezg. Pt. degrees F. Freezg. Pt. degs. Cels. 1 5 10 15 20 25 0.996 0.964 0.896 0.860 0.834 0.790 .009 .043 .087 .134 .182 1.234 31 27.5 22 15 5 . 8 0.5 2.5 5.6 9.6 14.8 22.1 BRINE CIRCULATION VS. DIRECT EXPANSION. The principal reason why brine circulation is still preferred by many to direct expansion, is to be sought in fear entertained with regard to the escaping ammonia in THE AMMONIA COMPRESSION SYSTEM. 143 case the pipes should leak. The danger from this source, however, seems to have been greatly exaggerated, as but few accidents of this kind have been known, the pressure in the ammonia pipe being generally not much higher than in the brine coils. Another advantage frequently quoted, in favor of brine circulation is the fact that comparatively great quantities of refrigerated brine are made and stored ahead, a supply which can be drawn on in case the ma- chinery should have to be stopped for one reason or another. In case of a prolonged stoppage, refrigerating brine made by dissolving ice and salt together can be circulated through the brine pipe^, which is also impracticable in case of direct expansion. It is also claimed that in small plants, in case of brine circulation, the general machinery might be stopped and only the brine pump be kept going to dispense the sur- plus refrigeration which had been accumulated in the brine during the day. THE DRYER. The dryer is an attachment of more recent coinage with which many compression plants are provided, its purpose being the drying of ammonia gas. It is a kind of trap on the suction pipe connected in such a manner (by means of a by-pass) that the gas can be passed through it when necessary. This trap is provided with removable heads for the introduction of some moisture absorbing substance (freshly burnt unslaked lime, as a rule) and for the with- drawal of the spent absorbent. LIQUID TRAP. It is also recommended to have an additional trap between the expansion valve and the expanding coils. The vaporization then takes place within the chamber or trap, and oil and other undesirable foreign matter will be deposited in this trap, and will not be carried over into the expansion coils. The trap is provided with a by-pass, so that it can be cleaned without stoppage. If such a trap can be placed within the rooms to be refrigerated it may be of some advantage ; but if it has to be placed outside, as in the case of brine circulation, much refrigeration is wasted. 144 MECHANICAL REFRIGERATION. CHAPTER V. ICE MAKING AND STORING. SYSTEMS OF ICE MAKING. One of the principal uses of mechanical refrigeration is the production of artificial ice, which is carried out after different methods or systems. The two methods which are most generally used are the so-called can sys- tem and the plate system. ICE MAKING CAPACITY OF PLANT. From the temperature of brine tank respectively, the temperature in expansion coils (which will be from 5 to 10 lower), the temperature in condenser coil from the size of compressor, etc., the theoretical refrigerating capacity of the plant can be calculated as above shown, making allowance for clearance, etc., as mentioned. The ice making capacity of the plant is, of course, much below this theoretical refrigerating capacity. An allowance from 6 to 12 per cent loss due to radiation in brine tank, pipes, etc., must be made in the start, and in addition to that a further allowance for the refrigeration of the water from the ordinary temperature to that of freezing, and for the refrigeration of the ice from 32 to the temperature of the brine. For that and other reasons it may be assumed that the ice making capacity of a ma- chine is from 40 to 60 per cent of its theoretical refriger- ating capacity. CAN SYSTEM. In making ice by what is called the can system, the water is placed in cans or molds made of galvanized iron of convenient shape, which are inserted in a tank filled with brine, the latter being kept cool by coils of pipe in which the expanding ammonia circulates. Temperature of brine varies from 10 to 25 F., 15 F. being considered favorable. SIZE OF CANS. The cans or molds for freezing vary in size and shape. The sizes of cans in most common use are shown in the following table: No. lean, 8^X15X32, weight of cake, 1001bs.,No. 18 Iron. " 2 " 8^X16X44, " " 150 " " 18 " " 3 " 11 X11X32, " " 100 " ". 18 " " 4 " 11 X22X32, " " 200 " " 16 " " 5 " II X 22X44, " 300 " " 15 " The weight is net. Allowance is made for about 5 per cent more to allow for loss in thawing, etc. ICE MAKING AND STORING. 145 VJHM < a v ^ :: - -o 3 w "-( ~ 888 8 8 S S 3 ...,.- Tons Ice Making Capacity. _ H, No. of Tanks o> N 8 o *9 P A m A 4^ to >fc co M " > - oosco co to eo --4 o --4 ~i > 500 OS OOO 'Length of Tank FeetC: Inches. f ?f f f f f f m OOO O O O O O OOtO Width of Tank Feet & Inches. oooooo 88888 888 Depth of Tank in Inches. co co co osoios Thickness x>f Plates, laches'. SfcS 3 83 S 8 S3. No. of Coils. ' Size of Pipe, Inches. * QOOOOOO 00 00 00 OOOSO9O* No, of Pipes High. Length of Coils. Mil 1 1 1 1 I 1 I 000 *0 O OOi. Ill 1 1 1 1 1 111. Total Feet of Pipe in Tank. ja^DOiGD S? co to *^cx;oj^ Feet of Pipe per Ton" Ice Making Capacity. Number of Ice Molds tri Tank. Size of Molds in Inches. XXXXXXXXXXXXXXXX xxxxxxxxxxxxxxxx Net Weight of Ice from Each. Mold. P* SSSggg'g g888 Number of Molds per Ton Ice Mak- ing Capacity. os boos to dumber* Hours for Freezing Each Mold. * " I Remarks. 146 MECHANICAL REFRIGERATION. TIME FOR FREEZING. At about 14 to 15 F. of the brine, 11-inch ice will take about forty-five to fifty hours to close, and 10-inch ice about thirty-eight to forty-four hours, and 8-inch ice about twenty-eight to thirty-two hours. If the temperature is 10 F. it will take about 20 to 25 per cent less time, but ice will be more brittle. Ther,e figures relating to the time of freezing are given on the basis of first rate conditions all around, which are seldom if ever attained in practical working. For this reason estimates on the size of brine tank, num- ber of cans, etc., are generally made on the basis of the following freezing times: Fifty to seventy-two hours for ice eleven inches thick; forty to sixty hours for ice ten inches thick, and thirty-six to fifty hours for ice eight inches thick. On this basis twenty cans are re^ quired (300-pound cans, seventy-two hours' freezing time, 11-inch ice) for each ton of ice making capacity per day, and the room in freezing tank must be in accordance therewith. Siebert, after a formula of his own, gives the follow- ing freezing time table : FREEZING TIMES FOR DIFFERENT TEMPERATURES AND THICK- NESSES OF CAN ICE. Thickn'ss. Temp. 10 V 12 14 16 18 20 22 24' 1 in. "oli 0.35 0.39 0.44 0.50 0.58 0.70 0,8$ 2 in. Tis 1.40 1.56 1.75 2.00 2.32 2.80 3.50 3 in. 2.86 3.15 3.50 3.94 4.50 5.25 6.. 30 7.86 4_in. 5.10 5.60 6.22 7.00 8.00 9.30 11.2 14.0 5 in. 8.00 8.75 9.70 11.0 12.5 14.6 17.5 21.0 6 in. 11,5 12.6 14.0 15.8 18.0 21.0 25.2 31-5 7 in. 15.6 17.3 19.0 21.5 24.5 28.5 34.3 42.8 8 in. 20.4 22.4 25.0 28.0 32.0 37.3 44.8 56.0 9 in. IJU? 28.4 31.5 35.5 40.5 47.2 50.7 71,0 10 in. 11 in. 12 in. 45.8 50.4 56 63.0 72.0. 84.0 100.0 120.0 31.8 35.0 39.0 43.7 50.0 58.3 70.0 87.6 38.5 12.3 47.0 53.0 60.5 70.5 84.7 106.0 It will be noticed on closer inspection that in this table the time for freezing different thicknesses of ice is proportional to the square of the thickness. Thus, to freeze a block ten inches thick takes 100 times as long as to freeze a block of one inch thickness, and four tim^s as long to freeze a block of four inches thickness, than vt takes to freeze one of two inches thickness, and so on. PIPE IN BRINE TANK. About 250 feet of 2-inch or 350 feet of 1^-inch pipe, or its equivalent according to the temperature of brine and capacity of machine, are generally used per ton of ice per twenty-four hours. Less pipe is frequently used, even as low as 150 feet of 2-inch pipe, and 200 feet of 1^-inch pipe per ton of ICE MAKING AND STORING. 147 ice making capacity (in twenty-four hours), but in that case the back pressure must be carried excessively low, which duly increases the consumption of coal and the wear and tear of machinery. It is also claimed that when the agitation in brine tank is very perfect and the ammonia expansion pipes have short runs (from header) eighty -five to 100 square feet of pipe in brine tank per ton of actual daily ice making capacity will be suffi- cient. These figures agree somewhat with the ones given in the foregoing paragraph. ARRANGEMENT OF FREEZING TANK. The size and length of pipe in brine tank should be arranged in such a manner that each row of molds is passed by an ammonia pipe on each side, preferably on the wide side of mold. The series of pipes in freezing tank are connected by manifold, the liquid ammonia entering the manifold at the lower extremity, and the vapor leaving by the suction manifold placed at the higher extremity of the refrigeration coils. When working with wet vapor of ammonia, thb liquid should enter at the upper extremity, and leave for compressor at lower extremity of refrigeration coils. The refrigerating tank should be well insulated by wainscoting made of matched boards. The space between wainscoting and tank (about ten to eighteen inches) should be filled in with sawdust, cork or other insulating material. It is recommended that brine tank insulation should be twelve to eighteen inches thick on sides of tank, and at least twelve inches under the bottom. Brine tanks are made of sheet iron or steel, wood and also of cement. Each kind has its admirers, accord- ing to circumstances, local and otherwise. Tank steel plate is said to make the best job, if properly built, and will last from ten to twelve years. Wooden tanks are built of 2x4 or 2x 6-inch planks, according to size of tank, and when built that way lined with %-inch matched flooring. All the 2X4 or the matched flooring is laid and bedded in pure hot asphal- tum before being nailed together. Cedar or cypress and hard yellow pinejwood are recommended for brine tanks. Cement tanks must be made of the best cement, and thoroughly hardened and dried and coated with hot asphaltum before being used. 148 MECHANICAL REFRIGERATION. SIZE OF BRINE TANK. The brine tank should be no larger than is required to receive the molds, the refrigeration coils and the agita- tor. Generally two inches space are left between molds and three inches space where the pipes pass between them. Three feet additional length for tank are allowed for agitator. Otherwise the size of the brine tank depends on the size of the mold, i. e., the time which it will take to freeze the contents solid. If it takes forty- eight hours to close the cans, the freezing tank must hold twice as much as is expected to be turned out in twenty- four hours. THE BRINE AGITATOR. The brine agitator is a little contrivance calculated to keep up a steady motion of the brine; it generally con- sists of a small propeller, driven by belt, which keeps up a constant motion of the brine from one side of the tank to the other. HARVESTING CAN ICE. The molds containing the ice are withdrawn from the freezing tank in small plants by " hand tackle," in larger plants by the power crane. The cans are removed by the crane to the dipping tank containing hot water, called the hot well, in which the cans are suspended for a short time, hoisted up again and turned over on an inclined plane or similar contrivance when the blocks of ice drop out and slide into the storage room. In some factories a sprinkling device takes the place of the hot well. PLATE SYSTEM. In making ice after the so called plate system, hollow plates through which cold brine or ammonia can be made to circulate are immersed vertically into tanks filled with water, and the ice forms gradually on both sides of the plates, thus purifying itself of any air or other impurities on its surface, which in the can system con- centrate themselves toward the center, forming an im- pure core. For this reason it is not necessary to distill or boil water which is otherwise pure for ice making after the plate system as it is required in the can system, and hence a saving of coal by the plate system. On the other hand, the latter system requires more skill to man- ipulate it successfully in all its details, and the plant is ICE MAKING AND STOKING. 149 more expensive to install and keep in repair. The com- parisons between the two systems as to cost depend largely on the size of plants and local conditions. The following table of comparison showing the cost of pro- duction per ton of the two systems in first-rate plants will meet average conditions. It is derived from Denton, and corrected after the experiences of St. Clair and others. Can System. Plate System. Harvesting and storing, Denton .11 .06 ' Engineers and. firemen .13 .12 Coal at $3.60 per gross ton . . .... .42 .24 Water pumped at 5c. per 1,000 cubic feet Interest and depreciation at 10 per cent Repairs .... .013 .246 .027 .026 .327 .034 .946 .807 SIZE OF PLATES. The plates vary in size; generally they are 10X14 feet in area, and may be made by welding pipe into continuous coil. The spaces between the pipes are filled out by metal strips, the whole forming a solid plate. TIME FOR FREEZING. The freezing on the plates to form ice of a thickness of about twelve to fourteen inches takes from nine to fourteen days, forming cakea of ice weighing several tons. HARVESTING PLATE ICE. When the ice on the plate has become thick enough, hot ammonia taken from the system before it enters the condenser is let into the plate coil, where it loosens the ice from the metal in a few minutes. The cake is then split, and grooves cut by circular saws or hand plows enable the splitting of the whole cake into pieces of desired size, ready for market. STORAGE OF MANUFACTURED ICE. The question whether it is more economical to shut down the ice plant during the winter and have a plant of sufficient size to supply the summer demand, or to store ice during the winter months and get along with a smaller plant, appears now to be decided in favor of the latter system, at least under generally prevailing condi- tions. 150 MECHANICAL REFRIGERATION. ICE FOR STORAGE. The best, clear, solid ice, without any core of any kind, is also the best for storage. Some insist that ice for storage should not be made at temperatures higher than 10 to 14 in brine tank, but where the storage or ante-room is kept cool, this is hardly required. CONSTRUCTION OF STORAGE HOUSES. Storage houses for manufactured ice are built on the same principle as storage houses for natural ice. Efficient insulation is the principal consideration. The house should be built as nearly, square as possible, the roof should have a good pitch, and both gable ends, as well as the top, should be ventilated. The escape of cold air, as well as the ingress of warm air at the bottom should be well guarded against. A plain house may be built of frame with 2X8 studdings, lined inside with P. & B. building paper and 1-inch boards. The outside to be lined with one thickness of boards and two-ply paper, the 8 -inch space between being filled with tan bark. The outside has a 4-inch air space; is then lined outside with tongued and grooved weather boarding. The roof is covered with paper, and has an 8-foot ventilator on top. ANTE-ROOM. Storage houses for manufactured ice should be pro- vided with an ante-room holding some fifty tons of ice and over, so as to obviate the frequent opening of the storehouse proper. This ante-room should be kept cool by pipes supplied with refrigerated brine or ammonia from the machine. Fifty cubic feet of ice as usually stored will equal about one ton of ice. REFRIGERATING ICE HOUSES. In order to keep the ice intact in storage rooms, etc., the same must be refrigerated by artificial means. Gen- erally a brine or direct expansion coil is used for that purpose. The refrigeration and size of coils required may be calculated after the rules given above and further on under "Cold Storage." For rough estimations it is as- sumed that such rooms require about ten to sixteen B, T. U. refrigeration per cubic feet contents for twenty four hours. ICE MAKING AND STORING. 151 About one foot of 2-inch pipe (or its equivalent in other size pipe) per fourteen to twenty cubic feet of space are frequently allowed in ice storage houses for direct expansion, and about one-half to one-third more for brine circulation. The pipes should be located on the ceiling of the ice storage house. It is also important that the house is well ventilated from the highest point, and thoroughly drained to prevent any accumulation of moisture below the bed of ice. A foundation bed of one and a half to two feet of cinders greatly assists the drainage of the house. Ice storage houses should be painted white, but not with white lead or zinc, as a mineral paint, like barytes or patent white, will emit less heat. PACKING ICE. Different methods obtain in packing ice into stor- age houses. Some place the blocks on edge, and as closely to- gether as possible, and place the other blocks on top exactly over each other (no breaking of joints). Between the times of storing the ice is covered with dry sawdust or soft (not hard) wood planer shavings. The top layer is always covered with dry sawdust or shavings. Others recommend strongly the use of ^-inch strips between layers of manufactured ice in the storehouse, the cakes being separated, top, side and bottom, from all others in the house. Instead of sawdust, etc., rice chaff is used in the south, and it can be dried and re-used. Straw or hay is also used in places. When sawdust is used in packing ice the layer must not be too thick, as this would create heat in itself. It is also recommended to store the ice with alternate ends touching and alternately from one and a half to two inches apart, somewhat similar to a collapsed worm fence, alternating on each row. This prevents the ice from freezing together solidly, so that it may be easily separated. The cakes should not be parallel with each other, and should never be stored unless the temperature is at, or below, the freezing point. Prairie hay is the best for covering ; oat or wheat is next best, with saw- dust last. Six inches of hay should be used between the ice and the wall, well packed. There should be no covering used until the house is filled. Use hay first, 152 MECHANICAL REFRIGERATION. secondly straw, and last sawdust if no hay can be got. In warmer climates ice should be stored and covered immediately on coming from the tank at a very low temperature, say 12 or 15. SHRINKAGE OF ICE. In an ice storage house without artificial refrigera- tion the average shrinkage from January to July will be about one- tenth pound of ice for every twenty -four hours for every square foot of wall surface. In round numbers it may amount to from 6 to 10 per cent of the ice stored in the six months mentioned. HEAT CONDUCTING POWER OF ICE. From an interpretation of practical data, it appears that about ten B. T. U. of heat will pass through a square foot of ice one inch thick in one hour for every degree Fahrenheit difference between the temperatures on either side of the ice sheet. WITHDRAWING AND SHIPPING ICE. In withdrawing ice from storage care should be taken that the water from the top does not get down to the ice below. Where there is an ante-room the same is filled from time to time from the main storage room, to with- draw from as occasion requires. For the shipment of ice in large quantities, in cars, boats, etc., it is packed the same as for storage. Small quantities of ice are fre- quently shipped by express, etc., in bags well packed with sawdust or the like. In withdrawing ice from storage houses ('"'breaking out") skilled labor isrequired, and besides this the proper tools, viz.: Two breaking out bars, one for bottom and one for side breaking; otherwise much ice will be broken and wasted. The small pieces of ice remaining on top layer, as well as any wet shavings or other material, should be removed each time when ice is taken from the house . SELLING OF ICE. The selling and delivery of ice is generally done by the coupon system. It is a system of keeping an accurate account with each customer of the delivery of and the payment for ice by means of a small book containing coupons, which in the aggregate equal 500 or 1,000 or more pounds of ice, each coupon, representing the number of pounds of ice taken by the customer every time ice is delivered. ICE MAKING AND STORING. 153 These books are used in the delivery of ice in like manner as mileage books or tickets are used on the rail- road . A certain number of coupons are printed on each page, each coupon being separated from the others by perforation, so tljat they are easily detached and taken up by the driver when ice is delivered. Such books are each supplied with a receipt or due bill, so that if the customer purchases his ice on credit all that is necessary for the dealer to do is to have the customer sign the receipt or due bill and hand him the book containing coupons equal in the aggregate to the number of pounds of ice set forth in the receipt or due bill. The dealer then has the receipt or due bill, and the cus- tomer has the book of coupons. The only entry which the dealer has to enter against such purchaser in his books is to charge him with coupon book number, as per number on book, to the amount of 500, 1,000 or more pounds of ice, as the value of the book so delivered may be. The driver then takes up the coupons as he delivers the ice from day to day. WEIGHT AND YOLTJME OF ICE. One cubic foot of ice weighs fifty-seven and one-half pounds at 32. One cubic foot of water frozen at 32 3 makes 1.0855 cubic feet of ice, the expansion being 8^ per cent by freezing. One cubic foot of pure water at the point of its greatest density, 39 F., weighs 62.43 pounds. HANDLING OF ICE. The handling of ice during transit and delivery to the retail customer is a matter to which all possible attention should be given, especially by the dealers in manufactured ice, in order to reap the full benefit for the expense and care bestowed by them on the making of a pure article. The wagons in which the water is delivered should be in a clean, sanitary condition in fact as well as in appearance. The men in charge of them should not walk around in the wagons with muddy boots. The ice should not be slid on dirty sidewalks, and then be washed off with water from the same bucket with which the horses are watered. These things, although they may seem to be of little consequence, are nevertheless watched and commented on, and go far to 154 MECHANICAL, REFRIGERATION. discredit the just claims made by the manufacturer of ice in favor of his product. The same remarks hold good for the shipment of ice in railroad cars. They should also be properly cleaned, and in case any cover- ing material is needed, it should be selected with the same care as that for the covering of ice in storage at the factory. COST or ICE. The cost to manufacture and to keep in readiness for shipping a ton of ice varies greatly with circum- stances, notably the price of fuel, the kind of water, the regularity with which the plant is operated, etc. The cost, therefore, is all the way from $1 to $2.50 per ton. It is also found that one pound of average coal will make from five to ten pounds of ice, according to cir- cumstances, and that from three to seven gallons of water are required per minute to make one ton of ice in twenty-four hours. COST OF MAKING ICE. The cost of making ice varies also considerably with the size of plant. Of a model plant producing about 100 tons of ice per twenty-four hours the following data of daily expense are recorded, and we consider them very low : Chief engineer $ 5.00 Assistant engineer 6.00 Firemen.. 4.00 Helpers 5.00 Icepullers 9.00 Expenses 12.00 Coal, at about $1 . 10 per ton 18. 00 Delivering at 50c per ton (wholesale delivery) 50.00 Repairs.etc 3.00 Insurance, taxes, etc 6.00 Interest on capital 20.55 Total for 100 tons of ice $138.55 Calculating on the smaller production of twenty tons in twelve or twenty-four hours we obtain the fol- lowing figures : Twenty tons Twenty tons in 12 hours. in 24 hours. Engineer! $2.50 $5.00 Fireman 1.50 3.00 Watchman 1.00 Coal... 3.00 3.00 Repairs .50 .50 Total for 20 tons of ice $8.50 $11.50 Average per ton 43.5cts 57. Sets. ICE MAKING AND STORING. 155 i-r Oi W >&. rf*. *> 4*- CO CO 'CO CO CO Co 01 CO 09 tO.jCO tO lo1 . 8-5 -* 1-* I-* Or O jSSjf*. j .50,00 O0_05 rf^ .tO.Wi- 1 "o"o"o"co "o"oo "p/|h Q -3 CrVj'o O-Of ^^ ^ co to 101 rfi. |_l 1_L !_i M. tO rfi- Engineers $1.50 to $5.00 per day. Oilers $1.25 per day. . Tankmen a Laborers $1 per day. General Helpers $1.25 per day, Coal 15 cts. pe or $3.00 per It* PI! -wo HE -v< out acc tio un Th del e last figu livery, hel mpanying ta s, for price of voidable. th nte ke etc ad g for be 166 MECHANICAL REFRIGERATION. SKATING KINKS. Artificial ice is also used for skating rinks to be operated all the year round. The amount of refrigera- tion, piping, etc., required for such installations depends largely on local conditions and other circumstances. A skating rink in Paris 7,700 square feet has 15,000 feet 1-inch pipe, and the refrigerating machine requires a 100-horse power engine. A skating rink in San Francisco, 10,000 square feet, is operated by machine of sixty tons refrigerating capacity. The skating floor at the Shenley Park Casino in Pittsburg is constructed as follows: It consists of a .3-inch plank floor covered with two thicknesses of impervious paper; the second floor likewise covered, leaving an air space below. About 80,000 pounds of coke breeze, or about ten inches in thickness, was placed on the last named floor, the whole surmounted by 3 X 6-inch yellow pine decking, carefully spiked down and joints calked, the whole finished with a heavy coat of brewer's pitch, this preventing any dampness from reaching the insulation. Nearly 300,000 feet of lumber were used for this structure, the rink being 70 X 225 feet, or about 16,000 square feet. On the top of the floor, with the ends extending through the two ends of tank, which are rendered water tight, are 72,000 feet of 1-inch extra heavy pipe, and they are simply straight pipes 228 feet long, connected at each end by a manifold. They are operated by direct expansion. This rink will, in case of a rush, accommodate 1,100 people, and one having one-quarter of its surface would probably suffice for a patronage of 200 people. The refrigerating ma- chine used to operate this plant has a refrigerating capacity of about 160 tons. QUALITY OF ICE. The keen competition between manufactured and natural ice has brought up a number of questions touch- ing the relative merits of these articles. Although it is quite generally conceded that ice made from distilled water is in every respect purer and more healthful than natural ice, still there are claims to the contrary, some claiming that natural ice will last longer, others that distillation takes the life out of the water and ice, etc. As far as the keeping is concerned, there is no difference if the blocks are wholly frozen without holes or cracks ICE MAKING AND STORING. 157 in them; and as to the life in manufactured ice, it is cer- tainly one of its advantages that all bacterial life is killed in the same. WATER FOR ICE MAKING. Expressed broadly, water that is fit for drinking pur- poses is fit for ice making, but while for drinking pur- poses a moderate amount of air and mineral matter in the water is more or less desirable, for ice making the iibsence of both is necessary if the ice is to be clear But even if a natural ice from a certain source is apparently or temporarily free from pathogenic (disease) bacteria, it may nevertheless be suspected of possible or future contamination if its analysis indicates contamin- ation with sewage or other waste matter. This is to be suspected when the ice or the water melted from the same contains an excess of ammonia, especially album- inoid ammonia, of nitrates and of chlorides. In order to give expression to this condition of things, many municipalities have special laws defining the purity re- quired for marketable ice. The corresponding ordinance in the city of Chicago demands that : "All ice to be de- livered within the city of Chicago for domestic use shall be pure and healthful ice, and is hereby defined to be ice which, upon chemical and bacteriological examination, shall be found to be free from nitrates and pathogenic bacteria, and to contain no more than nine-thousandths of one part of free ammonia and nine-thousandths of one part of albuminoid ammonia in 100,000 parts of water." CLEAR ICE. Although ice that. is impure may be clear, and ice which is practically pure may be cloudy or milky, clear ice is nevertheless desirable, and generally called for While many natural waters will furnish clear ice after the plate system, the can system always requires boiling, and generally previous distillation and reboiling of the water in order to furnish clear ice. (It sometimes happens that the ice of some cans is white and milky, while that of others is clear. This is generally due to a leak in the cans yielding the milky ice, whereby brine enters the same. It may be readily detected by the taste of the ice. ) BOILING OF WATER. In case a natural water is almost free from mineral matter (or if the same consists chiefly of carbonates of 158 MECHANICAL REFRIGERATION. lime and magnesia), and contains only suspended matter and air in solution, it may be rendered fit for clear ice making by vigorous boiling, either with or without the assistance of a vacuum, and with or without subsequent filtration, as the case may require. DISTILLED WATER. In order to save a vast amount of fuel, 40 per cent and upward, the exhaust steam from the engine is gen- erally used to supply the distilled water as far as it goes, and a deficiency is supplied directly from steam boiler. The impurities, such as grease, etc. , carried by the exhaust steam, are removed by a so-called steam filter, and then the vapors are passed through a condenser con- structed on the same principles as the ammonia con- denser. The condenser may be submerged in water or be an atmospherical or open air condenser. For cooling, the overflow water from the ammonia condenser is used in all cases. AMOUNT OF COOLING WATER. If 960 B. T. U. is the latent heat of -steam, and the temperature of the cooling water when it reaches the condenser is 1 1? and when it leaves the condenser is i, the theoretical amount of cooling water, P, in pounds required per ton of distilled water is p _ 2000 X 960 t *! To this from 2 to 20 per cent should be added for loss, etc., according to size of plant. SIZE OF CONDENSER. If t is the mean temperature of the cooling water, that is, the average between the temperature of the water entering and leaving the condenser, and if t t is the average temperature in the condenser (presumably about 210 F.), then the number of square feet condenser surface, S, per ton of water in twenty-four hours is found after the rule 9 _ 2000 X 960 1 (t t )nx24 n being the number of B. T. U. transferred by one square foot surface of iron pipe for each degree F. difference in one hour, steam being on one side and water on the other. For practical calculations fifty feet of l^-inch pipe are allowed in a steam condenser for each ton of ice produced in twenty-four hours. ICE MAKING AND STORING. 159 This is equivalent to about twenty-two square feet of condenser surface per ton of ice made in twenty-four hours. If we assume that this amount of surface is cal- culated to prove fully sufficient even if the cooling water has a temperature of 130 F. (the range temperature in this case being 212 -- = 40) we find n = 100 or very nearly that. From experiments quoted on page 27 it appears that n varies from 200 to 500 units, and is still more, nearly twice that, in case of brass -or copper pipe which is frequently used for steam condensers in distilling apparatus. We may assume, therefore, that n = 100 will give ample con- densing in extreme cases, and also allow for decrease in the heat transmitting power of iron pipes on account of oxidation, incrustation and the like. The condenser should be provided with an efficient gas and air collector. In case the natural water is very impure, a filtration of the same before it enters the steam boiler is very ad- visable and frequently resorted to. Various kinds of filters are used, sponge, charcoal and sand filters most generally; in exceptional cases boneblack filters are used also. In case the water con- tains much dissolved organic matter, filtering with ad- dition of alum is found very advantageous in many cases. REBOILING AND FILTERING WATER. The condensed distilled water contains air in solution, and sometimes also certain other volatile substances, possessing more or less objectionable flavors. To free it from both, the water is subjected to vigorous reboiling in a separate tank. Impurities thrown to tfce surface are skimmed off. The reboiling of the water must not be done by live steam (no perforated steam coil) if the water has natur- ally a bad smell. As a still further means of purification a charcoal or other filter is used, through which the water passes after reboiling. COOLING THE DISTILLED WATER. The filtered and boiled distilled water is now passed through a condenser coil over which cold water (water which is afterward used on ammonia condenser) passes, and after it is cooled down here as much as practicable, 160 MECHANICAL REFRIGERATION. it rurs to the storage tank which is generally provided with a direct expansion ammonia coil to reduce the tem- perature of the water as near to the freezing point as possible. From the storage tank the freezing cans are filled as required. INTERMEDIATE FILTER. Frequently another water filter is placed between the water cooler and the storage tank. DIMENSIONS OF DISTILLING PLANT. As is the case with most other appliances in the re- frigerating practice, the dimensions of the different parts of. a distilling plant vary considerable with different manufacturers. For superficial guidance we will quote one or two examples. TEN-TON DISTILLING PLANT. Open air condenser consisting of ninety-six pipes, each five feet long and one and one-quarter inch diameter. Reboiler four feet diameter, three feet high, con- taining steam coil of about sixty feet K-inch pipe. Intermediate cooler to bring temperature of reboiled water to about 80 consists of eighteen pieces IM-inch pipe, each twelve feet long. Charcoal filter thirty inches in diameter and seven feet high. Layer of charcoal five feet high. Cooring and storage tank three feet diameter and seven feet high, contains 250 feet l^-inch pipe for direct ammonia circulation. In the installation of a plant it is generally prudent to expect an increase in the production, and on this basis the above dimensions might well apply to smaller plants, say downward to five tons. THIRTY-TON PLANT. Steam filter three feet diameter, seven feet high with five consecutive wire screens, sixteen meshes per inch. Surface condenser containing 100 pieces 1-inch brass pipe, each four and a half feet long. (On this basis and on the assumption made in the discussion of the last formula n would be equal to about 400 units for brass, which, nearly agrees with the experiments quoted on page 26.) Reboiler twenty-four inches diameter, six feet high, containing four feet steam pipe ten inches in diameter. Intermediate cooler, thirty- two pieces of 2-inch pipe, each seventeen and a half feet long. ICE MAKING AND STORING. 161 Two charcoal filters, each three feet diameter, seven feet high. Layer of charcoal five and a half feet high. Cooling and storage tank six and a half feet diameter and eight feet high, containing 750 feet 1^-inch pipe for direct ammonia expansion. Sand filter two feet diameter, four feet high. THE SKIMMER. The skimmer is a contrivance which is arranged in many plants between the reboiler and the intermediate cooler, to skim off oil or any other light impurities which may float on the water. It is a small cylindrical vessel with an overflow at the top and connected to the reboiler with a straight pipe on the one side, and on the other with the intermediate cooling coil. The flow of the dis- tilled water to the latter coil is so regulated that a small amount of water will always overflow from the skimmer, taking with it the impurities. Sometimes the skimmer is provided with a steam coil to keep the water boiling, thus facilitating the rising to the surface of impurities. BRINE CIRCULATION. Among the other devices used for brine circulation besides propeller wheels, paddles, etc., we mention the pump preferably a centrifugal pump with a system of brine suction and discharge pipes located inside of the freezing tank, to take out the suction and return the discharge brine at regular intervals of space throughout the length and breadth of the tank, so that every spot between the cans is drawn into the circulation. ECONOMIZING FUEL. As much of the overflow water from the steam con- denser as may be needed for boiler feeding should be made to pass through a feed water heater located be- tween the steam filter or oil separator and the condenser. Through this heater the hot steam passes first, to make the feed water as hot as possible. ARRANGEMENT OF PLANT. . It is essential that the whole of the distilling ap- paratus is kept clean, sweet and free from iron rust; for these reasons the plant should be so arranged that all tanks, pipes, etc., which contain or conduct the distilled water are constantly filled with the same. The plant should be cleaned as often as necessary by steaming the same out. 162 MECHANICAL REFRIGERATION. DEFECTS OF ICE. Water which has gone through the process of distil- lation, condensation, reboiling, skimming, etc., does not always make unobjectionable ice, perfectly clear, without core or without taste and flavor. Ice may be practically pure, wholesome and palatable while containing these defects, and although most successful manufacturers know how, as a rule, to avoid these defects, still, occa- sionally ' they turn up and often prove to be a great annoyance. WHITE OR MILKY ICE. White or cloudy or milky ice is generally due to the presence of air in the distilled water ; it is caused by deficient reboiling or by overworking the reboiler, by a deficient supply of steam to the distilled water condenser. In the latter case, a vacuum is formed through the rapid condensation of the steam, and more air is drawn in and mixed with the steam than can be driven away by the usual extent of reboiling. If in this case the supply of steam cannot be increased, the amount of cooling water running over the condenser must be reduced, in order to keep the pressure up in the condenser. Other- wise the distilled -water must be more thoroughly reboiled. Air is also drawn in sometimes during the filling of the cans, through leaks in the distilled water pipes, etc. Frequently milky or streaky ice is also due to leaks in the freezing can, through which brine may be allowed to mix with the water in the can, which will then show as white or milky ice or as white spots or streaks. The salty taste of these parts readily shows their .cause, which may be remedied by mending the cans. ICE WITH WHITE CORE. The white core which forms in the ice from the last portion of the freezing water is due to mineral water (generally carbonate of lime and magnesia) derived from the natural water, from which it has not been success- fully separated, this separation being the principal object of the distilling process. In most cases the core is caused by the priming of the boiler, by carrying too much water, or by overworking the boiler and also not blowing off the boiler often enough, in which case the mineral constituents of the water accumulate and in- crease the danger of priming. The most rational ICE MAKING AND STORING. 163 remedy in this case is boilers large enough to make overworking, high water and priming entirely impos- sible. Another important remedy is the purification of the water before it enters the boilers. ICE WITH RED CORE. The red core in ice is brought about by a separation of oxide of iron in the ice, which was kept in solution in the water in the form of carbonate of iron. This sedi- ment is nearly always derived from the iron of the plant, more especially the coils. It frequently sets in during the second season of the working of a plant, and then is directly traceable to the rust which has formed within during the idle months or during shorter stoppages. To prevent this, the pipes and tanks might be kept filled with distilled and thoroughly reboiled water. If the water supply carries much carbonic acid, this sub- stance may contaminate the distilled water in such a manner as to dissolve iron from coils, etc., which is afterward deposited in the ice, as set forth . It has also been proposed to use pipe tinned inside for the distilled water condenser, and, if possible, tinned surface throughout the distilled water plant, to avoid the possibility of contamination with iron from this source. If the water supply carries carbonate of iron in solution, this may also become the cause of a red core, but only in case the boiler primes or is overworked and foul, and if the filters do not do their duty. The formation of this red core will doubtless be avoided in the future by proper treatment of the water and more careful management of boilers and plant. For the present, in cases where prevention is impossible, a cure may be effected by cooling the .distilled water down to about 36 to 38, at which temperature the iron will separate and may be separated by means of ordinary small sand or sponge filter. A radical, but rather expensive and troublesome, means to prevent the formation of a core of any kind, consists in the removal of the water still remaining un- frozen in the nearly complete ice block, just before the core begins to form, by means of a syringe and refilling the space with clear distilled water. DANGERS OF FILTRATION. A core in the ice may also be caused by mineral matter, which has been imparted to the distilled water 164 MECHANICAL REFRIGERATION. by the very process of filtration. When, as sometimes happens, the distilled water is charged with carbonic acid gas, and boneblack (not previously chemically treated) is used as filtering material, the water will take up a certain amount of carbonate of lime from the bone- black, and cause a white core. Other impurities in filtering material will cause similar cores. COLOR, TASTE AND FLAVOR OF ICE. Regarding the odor and taste possessed by some dis- tilled water, or by ice made therefrom, and also the greenish color shown by some ice, they are due to the presence of minute quantities of volatile matter (be- longing to the hydrocarbon class), which are derived from the natural water supply or from the lubricating materials. If their presence is due to the water, these defects, as in fact also most other defects in ice, will become more apparent if the boilers are allowed to be- come foul ; and, on the other hand, if the boilers are cleaned and blown off with sufficient frequency (in the case of vile water as often as once in twenty-four hours) these defects, like others, may be so reduced as to be- come almost unnoticeable. Priming of the boilers, of course, also increases these as well as other defects. If odor, taste or color of the ice are derived from the lubricating oil (which also sometimes causes cloudy ice) efficient oil 'or steam filters, kept in proper order, are the best remedy. An improper and excessive use of cylinder oil should also be carefully guarded against. BEST USE OF BONEBLACK. Where these preventive remedies do not apply, the distilled water may be freed from these defects (taste and odor) by filtering it through granulated boneblack ; and where this is found too expensive, as in the absence of means for revivifying the spent boneblack, the latter may be used, after having been reduced to an impalpa- ble powder. In this shape a pound or two of boneblack will go a long way, and will suffice to withdraw any smell or taste from a ton of water. To this end this powder should be intimately mixed with the distilled water in the said proportion before the last filtration, which will retain the boneblack, together with the impurities which it has absorbed from the water. Blood charcoal will act even more efficiently in this respect, but it is very doubtful whether its superiority ICE MAKING AND STORING. 165 to boneblack, powdered equally fine, is sufficient to overcome its high price (eighty-five cents per pound for the best imported article). With this material it is also important to make sure that 'it has been freed from all soluble constituents before using. NUMBER OF FILTERS REQUIRED. Regarding the number and kind of filters required, it would appear from the foregoing that this question must be settled separately for individual cases. When the distilled water supply is charged with much oily matter, with odoriferous volatile products, and also with mineral substances held in solution, we shall doubtless stand in need, at least for the time being, of an oil or steam filter, of a charcoal or boneblack filter (or bone- black powder) and of a filter between the freezing can and the distilled water or cooling tank. If mineral matters were entirely absent the last filter would not be needed, and if volatile products are absent the charcoal or boneblack treatment may be dispensed with, and vice versa ; and in case where the vapor from which the water is to be condensed is absolutely pure, and the coils and tanks of the condensing apparat-is likewise, no filters, skimmers and the like will be re- quired at all. It is to be hoped that within the near future the nat- ural water supplies will be so improved, and the management of boilers, engines, lubricators, condensing coils, reboilers, etc., will be manipulated universally m such a manner that the purity of the ice can be insured without so much attention. In this respect, frequent cleaning of boilers, blowing out of coils by steam when stopping and starting, and careful lubricating are among the first points to be considered. Under all circumstances, however, a simple but effi- cient filter between distilled water storage tank and the freezing cans will always be found a valuable help and safeguard. The filtering apparatus recently introduced for this purpose, consisting of two perforated disks with special filtering cloths between, is a neat and compact apparatus which seems to satisfy all demands as regards easy application, simple operation, economy of space, little attention and efficiency. ROTTEN ICE. When complaints are made about the " quick melt- 166 MECHANICAL REFRIGERATION. ing away " of manufactured ice, it will be found that it is generally caused by incomplete cakes, or cakes which have not completely closed in the center. The increased surface thus given to a cake causes it to melt away quicker, in increasing proportion as the surface of the whole increases by this procedure. For these reasons holes in ice must be avoided, and every piece of ice should be frozen solid all over. So called rotten ice also melts away quickly ; it is ice, the surface of which is also increased by cracks pro- ceeding from the outside to the center. Such ice is fre- quently withdrawn from the outside layers of stored manufactured ice not protected by mechanical refrigera- tion during the storage, and the application of such refrigeration is the best remedy for it. TEST FOR WATER AND ICE. Water if properly distilled (and of course ice made from such water, likewise) if slowly evaporated on a piece of platinum foil on a spirit lamp or a Bun^en gas burner, should leave no solid residue. If care is used in per- forming the operation a piece of thin glass plate may be used instead of the platinum foil. PURE WATER. The opinions on the requirements to be made of a water supply vary considerably; the following may stand for a sample of what some authorities demand of a water fit for drinking and other domestic purposes, and in some measure it may also be applied to ice. 1. Such water should be clear, temperature not above 15 C. 2. It should contain some air. 3. It should contain in 1,000,000-parts : Not more than 20 parts of organic matter. Not more than 0.1 part of albuminoid ammonia. Not more than 0.5 part of free ammonia. 4. It should contain no nitrites, no sulphurated hydrogen, and only traces of iron, aluminum and mag- nesium. Besides the mentioned substances it should not contain anything that is precipitable by sulphureted ammonia. 5. It must not contract any odor in closed vessels. 6. It must contain no saprophites and leptothrix and no bacteria and infusoria in notable quantities. ICE MAKING AND STORING 167 7. Addition of sugar must cause no development of fungoid growth. 8. On gelatine it must not generate any liquefying colonies of bacteria. DEVICES FOR MAKING CLEAR ICE. Besides the plate system and the use of distilled water, a number of contrivances have been devised for the manufacture of clear ice from natural water. The efficiency of these devices is based upon the motion which they keep up in the water in various ways. Their de- tailed description cannot be attempted here; moreover it seems that they have net. given much satisfaction gener- ally; probably they are too cumbersome and too uncer- tain in their performance. THE CELL SYSTEM. From the other methods in use for ice making, we may yet mention the cell system, which is in use on the continent to some extent. It consists of a series of walls of cast or wrought iron placed from twelve to eighteen inches apart, the space between each pair of walls being filled with the water to be frozen. The cooled brine cir- culates within a number of spaces left in the walls, and the ice forms on the walls, increasing in thickness until the two opposite layers meet. If thinner blocks are re- quired, freezing may be stopped at any time, and the ice removed. In order to detach the ice from the walls warmer brine may be circulated through the cell walls to loosen the ice. It stands to reason that impurities of the water will be separated from the same on the ice, if the two opposite layers are not allowed to meet. It will take, however, nearly double the time to freeze a block of a given thickness if the two layers are not allowed to meet to form one solid block. COST OF REFRIGERATION. In order to arrive at the possible remunerability of a refrigerating plant calculated to turn out artificial ice, it is but fair to compare the cost of the latter with the price of pure natural ice in the available market. If, however, on the other hand, a refrigerating plant is cal- culated to replace natural ice in the cooling of storage room, ice boxes, etc., the above calculation must be changed as a matter of course. 168 MECHANICAL REFRIGERATION. CHAPTER VL-COLD STORAGE. COLD STORAGE. Cold storage in general comprises the preservation of perishable articles by means of low temperature, and is one of the principal cases to which artificial refrigeration is applied. STORAGE ROOMS. Cold storage rooms, like ice houses, are built to be as perfectly insulated and protected as possible against the egress of cold and ingress of heat. They are kept cold by systems of pipe lines through which circulates either re- frigerated ammonia (direct expansion) or cooled brine (brine system). The size of the house depends on the stor- age requirements; they should be built as nearly square as possible, be properly ventilated, have double doors and windows, and all other protections that will insure the best insulation possible. The size of cold storage rooms varies from that of a small ice box of a few cubic feet capacity to that of gigantic storehouses of several million cubic feet space. CONSTRUCTION OF COLD STORAGE HOUSES. It is not within the scope of this treatise to go into details on this subject; nevertheless the descriptions of two specimens of walls for insulated buildings for storage and other purposes, which have given excellent satis- faction, may find a place here. CONSTRUCTION OF WOOD. A strong and well insulated wall of wood may be constructed by placing 2x 6-inch studs twenty-four inches apart; and in order to form outside of wall nail on them nrst a layer of 1-inch matched boards, then a layer of two- ply paper, and again a layer of 1-inch matched boards. On the inside a layer of 1-inch matched boards is nailed on the studs, and against these boards 2X 2-inch studs are placed twenty-four inches apart. In order to lorm the inside of wall one layer of 1-inch matched boards is nailed on the 2 X 2-inch studs, then a layer of two-ply paper, and lastly another layer of 1-inch matched boards on top of this paper. The spaces left between the 2 X 2-inch studs are left as air spaces, while the spaces between the 2 X 6-inch studs are filled in with sawdust crushed cork or the like. COLD STORAGE. 169 CONSTRUCTION OF BRICK AND TILES. For brick and tile construction the outside of the walls is formed of a brick wall sixteen inches or more in thickness, according to size and height of building. On the inside the wall is plastered. Again, a wall built of 4-inch hollow tiles is placed at a distance of three inches from the plaster coating of the brick wall, and a coat of plaster or cement on tiles on the inside finishes the whole wall. The space between the tiles and brick wall may bo filled in with cork, sawdust or some other insulating material. If the space between tiles and brick is filled with mineral wool, the wall represents a fire-proof structure. OTHER CONSTRUCTIONS. The following materials and dimensions have been ic commended for walls of cold chambers by Taylor: Fourteen-inch brick wall, 3^-inch air space, 9-inch brick wall, 1-inch layer of cement, 1-inch layer of pitch, 2x3-inch studding, layer of tar paper, 1-inch tongued and grooved boarding, 2x 4-inch studding, 1-inch tongued and grooved board, layer of tar paper, and, finally, 1- inch tongued and grooved boarding, the total thickness of. these layers or skins being 3 feet 3 inches. Thirty- six-inch brick wall, 1-inch layer- of pitch,l-inch sheathing, 4-inch air space, 2x4-inch studding, 1-inch sheathing, 3 inch layer of mineral or slag wool, 2 x 4-inch studding, and, finally, 1-inch sheathing; total thickness 4 feet 7 inches. Fourteen-inch brick wall, 4-inch pitch and ashes, 4- inch brick wall, 4-inch air space, 14-inch brick wall; total thickness 3 feet 4 inches. Fourteen-inch brick wall, 6-inch air space, double thickness of 1-inch tongued and grooved boards, with a layer of water-proof paper between them, 2-inch layer of best quality of hair felt, second double thickness of 1- inch tongued and grooved boards, with a similar layer of paper between them; total thickness, 2 feet 2 inches. Fourteen-inch brick wall, 8-inch layer of sawdust, double thickness of 1-inch tongued and grooved boards, with a layer of tarred water-proof paper between them, 2-inch layer of hair felt, second double thickness of 1- inch tongued and grooved boards with similar layer of paper between them; total thickness, 2 feet 4} inches. 170 MECHANICAL REFRIGERATION. The cold storage chambers built at the St. Kather- ine dock, London, are constructed as follows: On the concrete floor of the vault, as it stood origi- nally, a covering of rough boards 1 T 4 inches in thickness was laid longitudinally. On this layer of boards were then placed transversely, bearers formed of joist 4% inches in depth by 3 inches in width, and spaced 21 inches apart. These bearers supported the floor of the storage chamber, which consisted of 2%-inch battens tongued and grooved. The 4^-inch wide space or clearance between this floor and the layer or covering of rough boards upon the lower concrete floor was filled with well dried wood charcoal. The walls and roof were formed of uprights 5^X3 inches fixed upon the floor joists or bearers, and having an outer and inner skin attached thereto; the former consisting of 2-ineh boards, and the latter of two thicknesses or layers of 1^-inch boards with an intermediate layer of especially prepared brown paper. The 5^-inch clearance or space between the said inner and outer skeins of the walls and roof was likewise filled with wood charcoal, carefully dried. CONSTRUCTION OF SMALL ROOMS. Small storage rooms, down to ice boxes, are always, built of wood, paper, cork, etc., on lines similar to those given for wooden walls, but with endless variations. CONSTRUCTIONS AND THEIR HEAT LEAKAGE. The following construction of walls for cold storage buildings, taken from the catalogue of the Fred W. Wolf Co., have also been practically tested, and the ap- proximate heat leakage through them per square foot and per degree of difference in temperature between in- side and outside of the room, is also given in British thermal units in twenty -four hours. FIREPROOF WALL AND CEILING. Brick wall of thickness to suit height of building, 3-inch scratched hollow tiles against brick wall, 4-inch space filled with mineral wool, 3-inch scratched hollow tiles, cement plaster. Heat leakage 0.70 B. T. U. The ceiling to match this wall consists of the follow- ing layers : Concrete floor, 3-inch book tiles, 6-inch dry underfilling, double space hollow tile arches, cement plaster. Heat leakage 0.80 B. T. U. COLD STORAGE. 171 WOOD INSULATION AGAINST BRICK WALL. The following wood insulation against a brick wall has a leakage of 1.74 B. T. U., and consists of the fol- lowing layers : Brick wall, against which are nailed wooden strips 1X2 inches. On these are nailed two layers of 1-inch sheathing with two layers of paper .between ; next we have 2 X 4-inch studs sixteen inches apart, filled in be- tween with mineral wool, 1-inch matched sheathing, two ll,yers of paper; 1 X 2-inch strips, sixteen inches apart from centers ; double 1-inch flooring with two lnyers of paper between. CONSTRUCTIONS OF WOOD. The following constructions of wall, ceiling and floor may be followed for cold storage rooms when built of wood : The wall is constructed as follows : Outside siding, two layers of paper, 1-inch matched sheathing, 2X6- inch studs, sixteen inches apart from centers, two layers of 1-inch sheathing, with two layers of paper between, 2 X 4-inch studs, sixteen inches apart from centers, filled M between with mineral wool, 1-inch sheathing, two layers of paper, 2 X 2-inch strips, sixteen inches from center to center, two layers 1-inch flooring, with two layers of paper between. The heat leakage through this wall is 2.90B. T. U. The ceiling has the following details : A double 1-inch floor with two layers^of paper be- tween, 2 X 2-inch strips, sixteen inches apart from cen- ter, filled in between with mineral wool, two layers of paper, 1-inch matched sheathing, 2 X 2-inch strips, sixteen inches apart, filled between with mineral wool, two layers of paper, 1 inch matched sheathing, joists, double 1-inch flooring, with two layers of paper between. The heat leakage through this ceiling amounts to 2.17 B. T. U. The details of the floor are as follows : Two-inch matched flooring, two layers of paper, 1-inch matched sheathing, 4 X 4-inch sleepers, sixteen inches apart from centers, filled between with mineral wool, double 1-inch matched sheathing, with twelve lay- ers of paper between, 4 X 4-inch sleepers sixteen inches apnt from centers imbedded in 12-inch dry under- filling. 172 MECHANICAL REFRIGERATION. The heat leakage through this floor is given at 1.92 B. T. U. PIPING. All ammonia brine and heating pipes, headers and mains ought to be in the corridors, well insulated. CONSTRUCTIONS WITH AIR INSULATIONS. In the following constructions, taken from the cata- logue of the De La Yergne Refrigerating Machine Co., the insulating spaces are made by confined bodies of air, it being claimed by some that any filling of these spaces with loose non-conducting material will settle in places. The penetration of air and moisture is specially guarded against by the use of pitch in connection with brick or stone, or by paper where wood is used. Joints between boards should be laid in white lead and corners should be protected by triangular pieces of wood with paper placed carefully behind. CONSTRUCTIONS OF WOOD. The main walls of buildings (for refrigerators of hotels, restaurants and cold storage in general) built on the foregoing principles, have the following details, commencing inside: %-inch spruce, insulating paper, %-inch spruce, 1-inch air space, twelve inches square, %-inch spruce, insulating paper, %-inch spruce, 1-inch air space, %-inch spruce, insulating paper, %-inch hard wood. The ceiling or floor, when the room above or below is not cooled, has the following details, commencing be- low the joists : 76-inch board, insulating paper, %-inch board, floor beams, ^-inch board, insulating paper, %-inch board (two inches air space, %-inch board, insul- ating paper, y% -inch board). If room above is cooled, the parts in parenthesis may be omitted. Partitions between two cooled rooms, where differ- ence of temperature does not exceed 20, may be constructed as follows : ^-inch board, insulating paper, %-inch board, l>-inch air space, ,%-inch board, insu- lating paper, ^-inch board. For main inside walls between two rooms, of which one is not cooled, the following construction may be followed : %-inch board, insulating paper, %-inch board, two inches air space, %-inch board, insulating paper, ^-inch board, two inches air space, ,%-mch board, in- sulating paper, %-inch board. COLD STORAGE. 173 CONSTRUCTION IN BRICK. The outer walls in buildings of brick may be con- structed as follows, commencing outside : Brick wall of proper strength, two coats of pitch, two inches air space, %-inch board, insulating paper, %-inch board, two inches air space, %-inch board, insulating paper, %-inch board. The ceiling may be constructed as follows, when room above is not cooled (commencing at the top layer): One inch asphalt, two inches concrete, brick, wooden strips, %-inch board, insulating paper, %-inch board, two inches air space, %-inch board, insulating paper, %-inch board. If the difference in temperature between the lower and upper room does not exceed 20 P. the following construction for ceiling maytbe used : One inch asphalt, two inches concrete, brick. SURFACE OF INTERIOR WALLS. It is claimed that the porosity of the surfaces of walls in cold storage rooms ia in a measure responsible for the spoiling of provisions. Such walls, if made of cement, plaster and similar semi-porous material, pos- sess sufficient moisture to give rise to all sorts of putrefactive and bacterial growths, allowing them to thrive under favorable conditions. A further objection to this kind of walls is the quicker radiation of heat through them. For these reasons it has been urged that the walls in cold storage houses for cold and espe- cially meat storage, should be made from porcelain, and that they should be cleaned several times during the year. REFRIGERATION REQUIRED. The amount of refrigeration required in a given case depends on a number of circumstances and conditions, the size of the room, the frequency with which the arti- cles are brought in and removed, their temperature, spe- cific heat of produce, etc. For these reasons it is impos- sible to give a simple general rule, and the following figures, which are frequently used in rough calculations, must be considered as approximations only: For storage rooms of 1,000,000 cubic feet and over, 20 to 40 B. T. U. per cubic foot per twenty four hours. For storage rooms 50,000 cubic feet and over, 40 to 70 B. T. U. per cubic foot per twenty-four hours. 174 MECHANICAL REFRIGERATION. For boxes or rooms 1,000 cubic feet and over, 50 to 100 B. T. U. per cubic foot per twenty-four hours. For boxes less than 100 cubic feet, 100 to 300 B. T. U. per twenty -four hours. For rooms in which provisions are to be chilled, about 50 per cent additional refrigeration may be allowed in approximate estimations. For actual freezing the amount should be doubled (see also Meat Storage). PIPING AND REFRIGERATION. The foregoing rules on refrigerating capacity, as well as those given elsewhere, and including also the rules for piping given on pages 134 to 138, and elsewhere, have in common one vital defect^ in that they fit only one given temperature or rooms of one certain size. This condition of things necessarily gives rise to numer- ous misunderstandings arid many errors, and for this reason I have endeavored to outline some tables which would do equal justice to all the elements involved, or at least indicate how this could be done. The desire of the author to supply such much needed tables without further delay must be an excuse for their imperfections,as so far only comparatively few of the values given therein could be verified by data taken from actual experience. TABULATED REFRIGERATING CAPACITY. The amount of refrigeration required for cold storage buildings for provisions, beer, meat, ice, etc., depends, as has been mentioned repeatedly, principally on the size of the rooms, their insulation, the maximal outside tempera- ture and the minimal inside temperature (leaving open- ings, opening of doors and refrigeration of contents, etc., out of the question). The chief variants among these quantities are the degree of insulation, the size of rooms or houses and the minimal temperature within (the latter depending on the objects of storage) ; while for the maximal outside temperature we may agree upon a certain fixed quantity, which for approximate calculations will apply for a large territory of the United States, at least. We may safely take this maximal temperature for most of the United States at 80 to 90 F., so it will amply cover 86 F. Doing this, we can readily outline a table which will show the amount of refrigeration required for rooms of different sizes and of different insulation for any given COLD STORAGE. 175 temperature, as, for instance, the following table, which gives the number of cubic feet in cold storage buildings which can be covered by one ton of refrigerating capac- ity for rooms of different sizes, for different temperatures and for different (excellent and poor) insulation during a period of twenty-four hours : NUMBER OF CUBIC FEET COVERED BY ONE TON REFRIG- ERATING CAPACITY FOR TWENTY- FOUR HOURS. Size of building- Temperature F. in cub. ft. Insulation. more or less. 10 20 30 40 50 10O excellent 150 600 800 1,000 1,600 3,000 JL\J\J poor 70 300 400 600 900 2,000 1Of\r\ excellent 500 2,500 3,000 4,000 6,000 12,000 ,uuu poor 250 1,500 1,800 2,500 5,000 10,000 10,000 excellent poor" 700 300 3,000 1,800 4,000 2,500 6,000 3,500 9,000 7,000 18,000 14,000 30,000 excellent 1,000 5,000 6,000 8,000 13,000 25,000 poor 500 3,000 3,500 5,000 11,000 20,000 100,000 excellent 1,500 7,500 9,000 14,000 20,000 40,000 poor 800 4,500 5,000 8,000 16,000 35,000 The next table is constructed on the same basis, giving the amount of refrigeration required per cubic foot of space for. storage rooms of different sizes for dif- ferent temperatures, expressed in British thermal units, and for a period of twenty-four hours. REFRIGERATING CAPACITY IN B. T. U. REQUIRED PER CUBIC FOOT OF STORAGE ROOM IN TWENTY-FOUR HOURS. Size of building- Temperature F. iii cub. ft. Insulation. * more or less. 10 20" 30 40 50 100 excellent 1,800 480 360 284 180 95 j. \j\j poor 4,000 960 480 470 330 140 1,000 excellent 550 no 95 70 47 24 poor 1,100 190 165 110 55 28 10,000 excellent poor 400 900 95 160 70 110 47 81 30 40 16 20 30,000 excellent 280 55 47 35 22 11 poor 550 95 81 55 26 14 100,000 excellent poor 190 350 38. 63 30 55 20 35 14 18 7 4 176 MECHANICAL REFRIGERATION. The expression " excellent insulation" in the above and following tables may be taken to refer to wallu, ceilings, etc., the heat leakage of which does not exceed two B. T. U. for each degree F. difference in tempera- ture per square foot in twenty-four hours ; and the ex- pression "poor insulation" may be taken to refer to walls, etc., the heat leakage in which amountii to four B. T. U. and more. The average of the amounts of refrigeration, space and pipes given in the tables may be taken for average good insulation, other circum- stances being equal. TABULATED AMOUNTS OF PIPING. The amount of piping required for cold storage buildings depends, in the first place, on the amount of re- frigeration to be distributed thereby, and therefore indirectly on the same conditions as does the amount of refrigeration required. In addition thereto the amount of piping also depends on the difference between the temperature within the refrigerating or direct expan- sion pipes, and without. As this difference may be varied arbitrarily by the operator, and necessarily differ* for different storage temperatures, it would be veiy difficult to arrange a table fitting all possible conditions. However, it stands to reason that for each storage temperature there is one preferable brine or expansion temperature, and the accompanying tables on piping are expected to fit these temperatures for practical calcula- tions. LINEAL FEET OF 1-INCH PIPE REQUIRED PER CUBIC FOOT OF COLD STORAGE SPACE. building Temperature F. in cub. ft. Insulation. more or less. 10 20 30 40 50 excellent 3.0 0.78 0.48 0.36 0.24 0.15 100 poor 6.0 1.50 0.90 0.66 0.48 0.30 1/Wl excellent 1.0 0.26 0.16 0.12 0.08 0.05 poor 2.0 0.50 0.30 0.22 0.16 0.10 10,000 excellent poor 0.61 1.2 0.16 0.33 0.10 0.20 0.075 1.15 0.055 0.11 0.035 0.07 30,000 excellent poor 0.5 1. 0.13 0.25 0.08 0.15 0.06 0.11 0.040 0.03 0.025 0.05 100,000 excellent poor 0.38 0.75 0.10 0.20 0.06 0.12 0.045 0.09 0.03 0.06 0.009 0.018 COLD STORAGE. 177 The quantities of pipe given in the foregoing table refer to direct expansion, and should be made one and one -half times to twice that long for brine circulation. They also refer to 1-inch pipe, and by dividing the lengths given by 1.25, or multiplying them by 0.8, the corresponding amount of 13^-inch pipe is found. To find the corresponding amount of 2-inch pipe, the length given in the table must be divided by 1.8, or multiplied by 0.55. The next table is for, the same purpose as the one preceding, but it shows the number of cubic feet of storage building which will be covered by one foot of 1-inch pipe during a period of twenty-four hours for different sized rooms and different storage temperatures. NUMBER OF CUBIC FEET COVERED BY ONE FOOT OF ONE-INCH IRON PIPE. building Temperature F. in cub. ft. Insulation. more or less. 10 20 30 40 50 ion excellent 0.3 1.3 2.1 2.8 4.2 7.0 poor 0.15 0.7 1.1 1.5 2.1 3.5 1 000 excellent 1.0 4. 6.0 8.4 12.4 20. poor 0.5 2. 3.2 4.5 6.2 10. 10,000 excellent poor 1.7 0.85 6. 3. 10. 5. 13. 6.5 18. 9. 28. 14. 30,000 excellent poor 2.0 1.0 8. 4. 14. 7. 18. 9. 25. 13. 40. 20. 100,000 excellent poor 2.6 1.3 10. 5. 17. 8.5 22. 11. 33. 17. 110. 55. The number of cubic feet of space given in the last table as being covered by one lineal foot'of pipe refers to direct expansion, and only one-half to two-thirds of that space would be covered by the same amount of pipe in case of brine circulation. The figures in this table also refer to 1-inch pipe; and to find the corresponding amounts of cubic feet of space wliich would be covered by one lineal foot of 1^[- inch pipe, the numbers given in the table have to be multiplied by 1.25 or be divided by 0.8. To find the corresponding amount of space which will be covered by one lineal foot of 2-inch pipe, the numbers given in the table must be multiplied by 1.8 or divided by 0.55. 178 MECHANICAL REFRIGERATION. The foregoing tables are calculated for a maximum outside temperature of 80 to 90 F. If the same is ma- terially more or less about 10 per cent of refrigeration and piping should be added or deducted for every 5 F. more or less, as the case may be. TABLES FOR REFRIGERATING CAPACITY. The accompanying table designed by Criswell is cal- culated on the lines laid out in the foregoing paragraphs, on the assumption that the walls, ceiling and floor oi the cold storage building have an average heat leak- age of three B. T. U. per square foot in each twenty-f our hours for each degree Fahrenheit difference in tempera ture outside and inside of building. The maximum temperature is taken, at 82 F. Accordingly the total refrigeration for such a building is found by multiplying its total surface in square feet ^ third column of table) by 3, and the difference between the temperature in de- grees Fahrenheit within the storage building and 82 F. It is then divided by 284,000 to reduce the refrigerating capacity to tons of refrigeration. We will take for an example the building, 25x40x10. Its surface is 3,300 square feet, and the total refrigera- tion required for a temperature of 32 within the cold storage house is therefore , 1.53 tons, or, in round numbers, 1.5 tons. The building here referred to contains 10,000 feet, consequently one ton of refrigeration would cover _1M2? 1.51 =6,600 cubic feet of such a building. This figure should agree with the corresponding figure, given in the accom- panying table (at least, approximately so), some of the figures in the table being obtained by interpolation or averaging. If we compare this table with the table given on page 175 we will note several apparent discrep- ancies. They are explained by the desire to give a very liberal estimate in the tables on page 175, and to make allowance not only for the refrigerating of the contents, but also for the opening of doors. These are doubtless the reasons why the refrigerating capacity for smaller rooms in table on page 175 appears so large, especially at lower temperatures, as in tbese cases the opening of doors, etc., acts most wastefully. COLD STORAGE. TABLE FOR REFRIGERATING CAPACITY. XXXXXXXXXXXXXXXXXXXM |8Sil88S88888l|'Sg XXXXXXXXXXXXXXXXXXXX * i h-i h-^ h- * > ^ l\D rOCCC c: i -<* cc to c ^ co I? I! Contents, ;ubic leet. Surface in square feet. Ratio cubic feet to square feet. 179 M.Q II o' W 0?IOO tO^lplp3CC&>QIOtKf : *^lO*Sfl*-t&tO*- ' o; s* l^H** ^K^hh^l ^H-* p pops la t3j-p o to pc o: w co H- CD'S S2 CO Is DOORS IN COLD STORAGE. Xt may not be amiss on this occasion to state that the doors of cold storage buildings and rooms and ice boxes play a most important role in the economy of a plant; and therefore their construction, which is frequently left to the discretion of an ordinary carpenter, is a mat- ter of the greatest importance. Not only should they be constructed on the basis of the least heat transmission, but so framed and hung as to be tight and remain so for the longest possible time, as well as open freely at all times. Readjustments long neglected involve financial 180 MECHANICAL REFRIGERATION. losses in many directions, often expensive repairs, when a proper construction would avoid both by rendering the first needless. Facility for easily and quickly opening and closing, fastening and unfastening is most import- ant. Workmen persistently leave doors open while going in and out if these points be neglected, with a consequent great ingress of heat and moisture. For this reason it is but fair to recognize the laudable exertion of those firms who make the rational construction of doors used in cold storage buildings, rooms, etc., a special feature. CALCULATED REFRIGERATION. For more exact estimates the refrigeration required in a given case may be calculated by allowing first for the refrigeration required to keep the storage at a cer- tain given temperature in consequence of the radiation through walls; and second for the refrigeration re- quired to cool the articles or provisions from the tem- perature at which they enter the storage room down to the temperature of the latter. RADIATION THROUGH WALLS. If the number of square feet contained in a wall, ceiling, floor or window be /, the number of units of re- frigeration, R, that must be supplied in twenty-four hours to offset the radiation of such wall, ceiling or floor, may be found after the formula: E = fn (t tj B. T. units, or expressed in tons of refrigeration In these formulas t and t t are the temperatures on each side of the wall, and n the number of B. T. units of heat transmitted per square foot of such surface for a differ- ence of 1 F. between temperature on each side of wall in twenty-four hours. The factor > varies with the con- struction of the wall, ceiling or flooring, from 1 to 5. For single windows the factor n may be taken at 12, and for double windows at 7 (Box). For different materials one foot thick we find the following values for n: For pine wood ....... 2.0 B. T. U. For sawdust ....... .. 1.1 B. T. U. " mineral wooi ... 1.6 " " charcoal, pow'd 1.3 ' " granulated cork 1.3 " " " " cotton .......... 0.7 " " " " wood ashes ..... 1.0" " " soft paper felt . 0.5 " " " COLD STORAGE. 181 i<- < i *' M M 6.2 5.5 5.0 4.5 4,3 4.1 B. 1 . I For brick walls of different thicknesses the factor n may be taken as follows after Box : y t brick 4H inches thick n = 5.5 B. T. Units. 1 || 9 || || || = 4.5 || || || 2 2 " 18 " " " = 3io " " M 3 27 = 2.6 M " 4 " 36 " " " = 2.2 4i * " For walls of masonry of different thicknesses the factor n may be taken as follows after Box: Stone walls 6 i 12 18 24 30 36 German authorities give values for n which are less than one-half of the values here quoted. For air tight double floors of wood properly filled un- derneath so that the atmosphere is excluded, and for ceilings of like construction, n is equal to about 2 B. T. U. An air space sealed off hermetically between two walls has the average temperature of the outside and in- side air, hence its great additional insulating capacity. If the air space is hermetically sealed inside and outside, it appears that its thickness is immaterial; half an inch is as good as three inches. If a wall is constructed of different materials having different known values for n, viz., n lt n 2 , n s , etc., and the respective thicknesses in feet d,, d z , d 3t the value, n, for such a compound wall may be found after the form- ula of Wolpert, viz. : i n _d , _d_ 3 w 2 n s In case of an air space perfectly sealed off the factor n may be determined for that portion of the wall between the air space and the outside, which value is then in- serted into the formula B = fn (t-t t ) But in this case while t stands for the maximum out- side temperature t stands for the temperature of the air space, which may be averaged from the inside and outside temperature, taking into consideration theconductibility and thickness of the component parts of the wall. In the selection of insulating substances, their power to withstand moisture plays an important part in most cases. In this respect cork is a very desirable material. 182 MECHANICAL REFRIGERATION. likewise pitch and mixtures of asphalt; lamp black and a mixture of lamp black with mica scales is also used with great success, especially in portable refrigerating chambers, refrigerator cars and the like, as it will not pack from jolting, owing to its lightness and elasticity, and it also withstands moisture very well. REFRIGERATING CONTENTS. If the amount of refrigeration required to replace the cold lost by the transmission of walls, windows, ceil- ings, etc., has been determined upon, the refrigeration required to reduce the temperature of the goods placed in storage to that of the storage room is next to be ascertained. If p, p t , p 2 etc., be the number of pounds of differ- ent produce introduced daily into the storage room and s, Si, s 2 , etc., their respective specific heat, t their tem- perature and t t the temperature of the storage room, we find the amount of refrigeration, -R, in B.T. units required daily to cool the ingoing product after the formula: E = (p s -f p s, + p z s 2 ) (t t t ) B. T. units, or, expressed in tons of refrigeration : tons. 284000 The specific heat of some of the articles frequently placed in cold storage may be found in the following table: SPECIFIC HEAT AND COMPOSITION OF VICTUALS. 4-1 1 s> . ||j $% Water. Solids. il| I*! %2* *$3 115 CC c3 a CO- & Lean beef 72 00 28 00 77 41 10 Fat beef . 51 00 49 00 60 34 72 Veal 63 00 37 00 70 39 90 Fat pork 39 00 61 00 51 30 55 Eggs 70 00 30 00 76 40 100 74.00 26 00 80 ' 42 105 Cabbage . 91 00 9 00 93 48 129 Carrots 83 00 17 00 87 45 118 Cream . . 69 25 30 75 68 38 84 Milk 87 50 12 50 90 47 124 Oyster . . . 80 38 19 62 84 44 114 Whitefish 78 00 22 00 82 43 111 Eels .... 62 07 37 93 69 38 88 76 62 23.38 81 42 108 Pigeon 72 40 27 60 78 41 Chicken 73 70 26 30 80 42 COLD STORAGE. 183 CALCULATION OF SPECIFIC HEATS OF VICTUALS. The specific heats in the fifth column of the forego- ing table is calculated after the formula s= _o 0.^=0.008 + 0.20 JLUU in which formula s signifies the specific heat of a sub- stance containing "a" per cent of water and "6" per cent of solid matter; 0.2 is the value which has been uni- formly assumed to represent the specific heat of the solid constituents of the different articles in question. If the articles are cooled below freezing, which takes place be- low 32 F., the specific heat changes, owing to the fact that the specific heat of frozen water is only a^out half of that of liquid water. In conformity with this fact, and considering that the specific heat of the solid mat- ter is not apt to change under these circumstances, we find the specific heat, s', of the same articles in a frozen condition after the following formula : and in this way I have obtained the figures in the sixth column of the above table. The figures in the last column, showing the latent heat of freezing, have been obtained by multiplying the latent heat of freezing water, which is 142 B. T. U. by the percentage of water contained in the different ma- terials considered. In this manner the specific heat for other articles may be readily calculated. For still more approximate determination we may assume that the specific heat of all kinds of produce is about 0.8. On this basis the amount of refrigeration, R, required to reduce the temperature of the produce to that of the refrigerating room is B=P (tt t ) 0.8 units. And expressed in tons= E = P ^l^ tons of refrigeration. P being the total weight of the produce introduced daily. FREEZING GOODS IN COLD STORAGE. If, in addition to the refrigeration of the goods to be stored the same have to be actually frozen and cooled down to a certain temperature below freezing, the re- frigeration as calculated ia the foregoing paragraph 184 MECHANICAL REFRIGERATION. must be corrected, for the water contained in the goods must be frozen, which requires an additional amount of refrigeration. On the other hand, the specific heat of the frozen water being one-half of that of water, this circumstance lessens somewhat the amount of refrigera- tion required below freezing point. Therefore if p rep- resents the number of pounds of water contained in a daily charge for cold storage to be chilled and reduced to a temperature, n the amount, E, found by the foregoing rules must be corrected by adding to it an amount of refrigeration equivalent to p (126 + 0.5^) units. CONDITIONS FOR COLD STORAGE. For the preservation of perishable goods by Gold storage the temperature is the main factor, although Other conditions, such as clean, dry, well ventilated rooms and pure air, are of paramount importance. Humidity is almost as important as temperature. Extreme cold tem- perature will react on certain goods like eggs, fruits, etc , so that when taken out the change of temperature will deteriorate their quality quickly. Hence the conditions under which articles must pass from cold storage to con- sumption are often of as vital importance as the cold storage itself, for which reason special rules must be followed in special cases. MOISTURE IN COLD STORAGE. Besides the temperature in .a cold storage room the degree of moisture is of considerable importance. It is neither necessary nor desirable that the storage room should be absolutely dry; on the contrary, it may be too dry as well as it may too damp. If the room is too dry it will favor the shrinkage and drying out of certain goods. If the room is too damp goods are liable to spoil and become moldy, etc. For this reason the moisture should always be kept below the saturation point. This condition can be ascertained by the hygrometic methods described in the chapter treating on water and steam. There is little danger that the rooms will ever be too dry; on the other hand, they are not required to be abso- lutely dry, and as to chemical dryers, such as chloride of calcium, oatmeal, etc., they are probably superflu- ous, with proper ventilation and refrigerating machinery properly applied. COLD STORAGE. 185 Generally the artificial drying of air is considered superfluous in cold storage, as the air is kept sufficiently dry by the condensation that forms on the refrigerating pipes. In this way the moisture exhaled by fruits, etc., is also deposited. Special care, however, is to be taken to remove the ice from the coils from day to day as it forms, in which case it is readily removable. Chemica.1 dryers are seldom used in storage houses refrigerated by artificial refrigeration. Freshly burnt lime is sometimes used in egg rooms. In cold storage houses operated by natural ice, chem- ical or physical absorbents, such as oatmeal, slacked lime, chloride of calcium and chloride of magnesium are fre- quently used. The latter substance is the principal con- stituent of the waste bittern of salt works, which is sometimes used for drying air in the cold storage of fruit. The waste bittern is spread out on the entire sur- face of the floor, and, if needed, on additional surfaces above it. One square foot of well exposed bittern, either in the dry state or state of inspissated brine, will be enough to take up the moisture arising from two to six bushels of fruit, varying according to its condition of greenness or ripeness. The floors of the preserving room should be level, so that the thick brine running from the dry chloride may not collect in basins, but 'spread over the largest surface. The moisture from the fruit taken up by the absorbent varies from about three to ten gal- lons for every 1,000 bushels of fruit weekly. The spent chlorides or the spent waste bittern may be revived by evaporation, by which they are boiled down to a solid mass again. The waste bittern is also used as a crude hydrometer by dissolving one ounce of the same in two ounces of water and by balancing the shallow tin dish containing this mixture on a scale placed in the cold storage room. If the scale keeps balanced, it indicates the proper state of dryness, but if the weight of the mixture increases, the moisture in the room is increasing and the means for keeping the air dry should be put in operation. DRY AIR FOR REFRIGERATING PURPOSES. To produce a dry air by mechanical means St. Glair considers the entire absence of any condensing or refrig- erating surface in the space to be refrigerated absolutely 186 MECHANICAL REFRIGERATION, necessary. The rapid circulation of the air in the room is also of vital importance; and in such circulation no con- tact of the incoming cold air with the outgoing warm air to cause condensation is the result aimed at. To insure these conditions he places the refrigerator at the highest point, and has communicating air shafts from the bottom of the same to the rooms to be cooled. Like shafts ascend from the top of the rooms cooled to top of the refrigerator. The refrigerating coils in the refrigerator are kept at a temperature of zero to 15 below, and a small stream of strong brine is allowed to drip over the coils to a pan underneath, being pumped back to the upper drips as fast as deposited. This brine will have a temperature rang- ing from zero to 4 below. The action is said to be simple and effective; all moisture is either condensed or frozen instantly as it comes in contact with such low temperature, and an absolutely dry air descends in the air shafts to the rooms to be cooled. VENTILATION OF COLD STORAGE ROOMS. The foul air in storage rooms is removed by ventila- tion, which is effected in various ways. Frequently the change of air brought about by opening doors, etc., is considered sufficient; in some cases windows are opened from time to time. Ventilating shafts located in the ceil- ing of storage rooms are also often used as means to effect a change of air. A small rotary fan, located in the engine room and connected with the storage rooms by galvanized iron pipes, provided with gates or valves, is a very effi- cient device to remove foul air. Where fans cannot be applied for want of motive power or other reasons a ventilating shaft, if properly constructed, will answer every purpose, and is much less expensive to operate. The air ducts, or pipes, should be located in the hallways, and connection made thence to each room through the side wall near the ceiling, and some suitable device should be arranged on the end of the pipe extending into the cooling room to regulate the amount of ventilation. The several air ducts leading from the various hallways should have a common ending, and connection made thence to the smoke stack. The strong up draft from the furnace insures ample ventila- tion from rooms at all times, provided that the pipes are made air tight and large enough for the purpose. COLD STORAGE. 187 The simple expedient of a ventilating shaft extend- ing just outside of the building without being raised to a considerable height, or some provision made to artifi- cially produce a draft, often proves inoperative as a means of ventilating refrigerating rooms, because the air in the rooms, becoming cold, settles to the floor and escapes through crevices about the doors or when the doors are opened, causing a down draft, and in many cases over- balancing the uptake of the ventilating pipe. FORCED CIRCULATION. Of the various recent devices for forced circulation and the drying of air in cold storage, most are based on the principle of St. Clair delineated in the foregoing paragraph. It may also be combined with any system of artificial ventilation which may be brought about by fans, ventilators, etc. The introduction of air cooled a few degrees below the temperature of the storage room (by drawing the air over refrigerated surface, as is done in the St. Clair and similar systems) insures dry ventila- tion. VELOCITY OF AIR. If, as in the St. Clair system of forced circulation, the air after having been cooled (and dried) by being passed over the refrigerating coils located in the top part of the storage rooms, falls down from the bottom of the coil through a shaft or shafts to the bottom of the room, while the hot air from the top of the room ascends to the top of the coil by shafts or a shaft, the velocity of the air current thus produced by a difference in temperature, or rather by a difference in gravity due thereto, may be expressed by the following formula: In this formula Tand T Q are the temperatures (in degrees absolute Fahrenheit) of the air in the hot and cold air shafts respectively, which are supposed to have the same sectional area, and Fis the velocity with which the air moves through the shafts in feet per second. NUMERICAL RULES FOR MOISTURE. The proper degree of humidity in cold storage rooms, especially also for the storage of eggs (to avoid mold and shrinkage at the same time) is of the utmost impor- tance, and Cooper finds that the relative humidity should 188 MECHANICAL REFRIGERATION. differ with the temperature at which the rooms are kept. Thus a room kept at 28 F. should have a relative hu- midity of 80 per cent, while a room kept at 40 F. should have a humidity of only 53 per cent, and intermediate degrees of humidity for intermediate temperatures. At least one correct normal thermometer (to correct the others by) should be kept in each cold storage plant. DISINFECTING COLD STORAGE ROOMS. Meat rooms and other cold storage rooms may be dis^ infected if necessary by formaldehyde vapors, which are produced by burning wood spirit in an ordinary spirit lamp, the wick of which is covered by a platinum wire screen, in the form and size of a thimble, to make it only glow, and not burn with a flame. Special lamps are made also for this purpose. COLD STORAGE TEMPERATURES. Generally speaking, the temperature of cold storage rooms is about 34 F. For chilling the temperature of the room it is generally brought down to 30 F M and in the case of freezing goods from 10 F. to F. The temperatures and other conditions considered best adapted for the cold storage of different articles of food, provisions, etc., have been compiled in the follow- ing paragraphs, which reflect the views of practical and successful cold storage men as expressed by them in Ice and Refrigerati on : STORING FRUITS. The temperatures for storing fruits are given in the following table : FRUIT. REMARKS. F Apples 30-40 Bananas 34-36 Berries, fresh For three or four days 34-36 Canteloupes Carry only about three weeks 32 Cranberries 33-34 Dates, figs, etc 34 Fruits, dried 35-40 Grapes : 32-40 Lemons 36-45 Oranges 36 Peaches 35-45 Pears 33-36 Watermelons Carry only about three weeks 32 In general, green fruits and vegetables should not be allowed to wither. Citrus fruits should be kept dry until the skin yields its moisture, then the drying process should be immediately checked. For bananas no rule can be made ; the exigencies of the market must govern the ripening process, which can be manipulated almost at will- COLD STORAGE. 189 Fruits, especially tender fruits, should be placed in cold storage, just when they are ripe. They will keep better than if put in when they are not fully ripe. Pears will stand as low a temperature as 33. Sour fruit will not bear as much cold as sweet fruit. Catawba grapes will suffer no harm at 26, while 36 will be as cold as is safe for a lemon. The spoiling of fruit at temperatures below 40 F. is due to moisture. ONIONS. Onions, if sound when placed in cold storage, can be carried several months and come out in good condition. It is important that the onions be as dry as possible when put into cold storage. If they can be exposed to a cool, dry wind, they will 1986 much of their moisture. They are usually packed in ventilated packages or crates. It is claimed, however, that they will keep all right in sacks, if the sacking is not too closely woven, and stored in a special way, being arranged in tiers so the air has free access. Authorities differ as to the best tempera- ture at which to keep the onions, the range being from 30 to 35 F. But 32 to 33 seems to be generally pre- ferred. The rooms should be ventilated and have a free circulation of dry air. Onions should not, of course, be stored in rooms with other goods. When the onions are removed the rooms should be well aired, thoroughly scrubbed and, after the walls, ceiling and floor are free from moisture, should be further purified and sweetened by the free use of lime or whitewash; and a good coat of paint or enamel paint would be advantageous, after which the rooms can be used for the storage of other goods, though some practical cold storage men are of the opinion that such rooms should not afterward be used for the storage of eggs, butter or other articles so sensitive and susceptible to odors, but should be set aside for the storage of such goods as would not be injured by foreign odors. Attempts have been made to kiln dry onions, but this was found impracticable, owing to the fact that the extreme heat required to penetrate the tough outer skin of the onion caused it to soon decay. Experiments have also been made with evaporating onions after removing the outer skin, but this was also unsuccessful. There is no difficulty, however, in keeping onions in cold storage 190 MECHANICAL REFRIGERATION. for six or seven months and having them come out in perfect condition, if the above suggestions are followed. PEARS* Pears, like other tender fruit, should be placed in cold storage when still firm, and before the chemical changes which cause the ripening have set in ; and they must be handled very carefully. The temperature at which to store them is from 33 to 40 F. The pears after having been kept in cold storage will spoil very rapidly after coming out, and should be consumed as short a time thereafter as may be. Pears should be picked as soon as the stem will readily part from the twig, and before any indications of ripeness appear ; and, as in the case of apples, should immediately be placed in storage, but the temperature should not be as low as for apples. Few kinds of pears can be kept as late as April and May; even after January there is considerable risk. The temperature should be between 33 and 40, but, as for all winter storage goods, must be constant and uniform, for which reason the rooms should have heating as well as chilling pipe. The paper wrapper will best protect them from touching each other in storage. LEMONS. The best storage temperature for lemons is allowed to be 45 and below, but below 36 F. they are liable to be injured, if kept at that temperature for any length of time. The acid, which is the principal ingredient ot lemons, is decomposed, and those containing the least acid will stand the least cold. Lemons should not be ex- pected to keep good in cold storage over four months. Lemons stored during the first three months of the year are said to hold good for at least five months, but if stored later it is more difficult to preserve them. GRAPES. Grapes for cold storage must be well selected and very carefully packed. No crushed or bruised or partly decayed berries are allowable; a whole lot may be tainted by a single berry. Grapes lose much in flavor and taste in cold storage. Malagas hold their flavor best, and will last till Christmas and even longer, but the Concord and other softer grapes will not hold out after Thanksgiving day, as a rule. The best temperature is from 32 to 40. COLD STORAGE. 191 At the latter temperature the flavor appears to suffer less, especially with the Concord, and the lower tem- perature has more effect on the Concord than on the Malaga, it appears, generally speaking. APPLES. Apples may be kept either in barrels or boxes or in bulk, it is said, with equally good results. The barrels, etc., if kept in storage for any length of time, must be refilled to make up for shrinkage, before being put on the market. Opinions as to best temperature for apples vary all the way from 30 to 40. The latter temperature should not be exceeded in any case. If the air in cold storage is too dry it wilts the apples, and if it is too damp it bursts and scalds apples, especially if the temperature is not low enough. The so called " Rhode Island Green- ing" seems to be most susceptible to scalds. Apples should be picked early and put in cold storage with the least possible delay. Apples when stored in barrels should not be stored on ends, but preferably on their sides. A temperature of 13 is considered most favor- able by some. In storing apples eight to ten cubic feet storage room space is allowed per barrel, and twenty to twenty-five tons daily refrigerating capacity per 10,000 barrels. STORING VEGETABLES. ARTICLES. F. Asparagus 34 Cabbage 32-34 Carrots 33-34 Celery 33-35 Dried beans 32-40 Dried corn 35 Driedpeas 40 Onions 32-34 Parsnips 33-34 Potatoes 34-36 Sauerkraut .* 35-38 Sweetcorn 35 Tomatoes , 34-35 Asparagus, cabbage, carrots, celery, are carried with little humidity; parsnips and salsify, same as onions and potates, except that they may be frozen without detri- 2116 FERMENTED LIQUORS. ARTICLES. F, Beer, ale, porter, etc 33-42 Beer, bottled 45 Cider 30-40 Ginger ale 36 Wines 40-4?- Olarets 45-50 192 MECHANICAL REFRIGERATION. The temperatures at which these articles are to be kept in storage is of course not the temperature at which they should be dealt out for consumption. Beer, ale and porter should not be offered for consumption at a temper- ature below 52 F., and temperatures between 57 and 61 are even preferable on sanitary grounds, which, however, are often disregarded to insure a temporarily refreshing palate sensation. STORING FISH AND OYSTERS. Fish if previously frozen should be kept at 25 after being frozen. Oysters should not be frozen. The follow- ing temperatures are given: ARTICLES. F. Dried fish 35 Fresh fish. 25-30 Oysters 33-40 Oysters in shell 40 Oysters in tubs 35 A successful firm describes the freezing of fish as follows: When the fish are unloaded from the boats they are first sorted and graded as to size and quality. These are placed in galvanized iron pans twenty-two inches long, eight inches wide and two and a half inches deep, covered with loosely fitting lids, each pan containing about twelve pounds. The pans are then taken to the freezers. These are solidly built vaults with heavy iron doors, resembling strong rooms, and filled with coils of pipes so arranged as to form shelves. On these shelves the pans are placed, and as one feature of the fixtures is economy of space, not an inch is lost. The pans are kept here for twenty- four hours in a temperature at times as low as 16 below zero. Each vault or chamber has a capacity of two and a half tons, and there are sixteen of them, giving a total capacity of forty tons, which is the amount of fish that can be frozen daily if required. On being taken out of the sharp freezers the pans are sent through a bath of cold water, and when the fish are removed they are frozen in a solid cake. These cakes are then taken to the cold storage warehouse, which is divided into chambers built in two stories, almost the same as the sharp freezers. The cakes of fish, as hard as stone, are packed in tiers and remain in good condition ready for sale. It is possible to preserve them for an indefi- nite time, but as a rule frozen fish are only kept for a sea- son of from six to eight months. They are frozen in the spring and fall when there is a surplus of fish, and sold COLD STORAGE. 193 generally in the winter or in the close season when fresh flsh cannot be obtained. For shipment, fish may be packed in barrels after the following directions: Put in a shovelful of ice at the bottom of the barrel, and be always careful to see that auger holes are bored into the bottom of the barrels, to let the water leak out as fast as it is produced by the melting ice. After putting in a shovelful of fine ice, crushed by an ice mill, put in about fifty pounds of fish; then another shovelful of ice on top of the fish, etc., until the barrel is full, always leaving space enough on the top of the barrel to hold about three shovelsful of ice. By shovels, scoop shovels are meant. Oysters are said to keep six weeks safe at 40. In one instance they have been kept ten weeks at this tempera- ture for an experiment. STOKING BUTTER. Butter is preserved both ways : by keeping the same at the ordinary cold storage temperatures, and also by freezing. Both processes have given satisfactory results, but it appears that those obtained by actual freezing are quite superior, the flavor and other qualities of the butter being perfectly preserved by the freezing. To obtain the best results butter should be frozen at a tem- perature of 20 and the variation should not be over 2 G to 3. For long storage, however, butter, like fish, should be frozen quickly at a temperature of from 5 to 10, and subsequently it should be kept at about 20- F. Ash and spruce tubs make the best packages for butter. As regards thawing it, it is simply taken from the freezer, as in the case of ordinary cold storage goods, with- out paying any attention to the thawing out process. The thawing comes naturally, and the effect that it has upon the butter is to give it a higher and quicker flavor when thawed out than when frozen. When selling frozen goods it is sometimes necessary to let them stand out a little time in order to get the frost out of the butter; particu- larly so in the case of high grade goods, for the thawing develops the flavor. June butter is considered the best for packing and storage. It is essential to exclude the air from butter while being held in cold storage, hence cooperage must be the best, and soaked in brine for twenty -four hours. If the top of the butter is well cov- ered with brine, a temperature of 33 to 35 will answer. 194 MECHANICAL REFRIGERATION. For ordinary cold storage of butter and similar articles. the following temperatures are given: ARTICLES. F. Butter 33-35 Butterine 35 Oleomargarine 35 STORING CHEESE. The best temperature for the storage of cheese is generally considered 32 to 33, and should not vary more than 1. Cheese should not have been subjected to any high temperature before being placed in cold storage. Cheese should be well advanced in ripening before it is placed in cold storage, to avoid bad smell in the house. It generally enters the cold storage room in June and July, and leaves by the end of January, sooner or later when needed. It will keep much longer, however, over a year when needed. It must be kept from freezing. If frozen, it must be thawed gradually, and consumed thereafter as soon as possible, or otherwise it will spoil internally. The humidity of the room must keep the cheese from shrinking and cracking, but the room must not be damp either, otherwise mold will set in. MILK. Milk is not as a rule kept in cold storage except for a short period. It has been proposed, however, to con- centrate milk by a freezing process, by which part of the water in the ice is converted into ice. The ice is allowed to form on the surface of the pans, which are placed in cold rooms, and the surface of the ice is broken fre- quently, to present a fresh surface for freezing. BOGS. Eggs should be carefully selected before being placed in cold storage, and every bad one picked out by can- dling. The best temperature for storing eggs is between 32 and 33 F. As eggs are very sensitive and will absorb bad odors, etc., it is not advisable to store them together with cheese or other products exhaling odors. For some purposes the contents of eggs may be stored in bulk. In this case the eggs are emptied into tin cans containing about fifty pounds and stored for any length of time at 30 F. They must be used quickly after thawing. Eggs are generally placed in cold storage in April and early May; later arrivals will not keep as well. They are seldom k^pt longer than February. The tem- COLD STORAGE. 195 perature best suited for eggs is supposed to be between 31 and 34 by American packers, but English dealers claim that 40 to 45 is equally good. The humidity of the air in the cold storage room has doubtless a great bearing on this question. Eggs which have been stored at 30 must be used soon after leaving storage, while eggs kept at 35 to 40 will keep nice for a longer time, as the germ has not been killed in the latter, and consequently they taste fresh. Eggs for the market, especially those to go in cold stor- age, must not have been washed. Washed eggs have a dead and lusterless looking shell, looking like burned bone through a magnifying glass. It is also recommended that eggs in cold storage should be reversed at least twice weekly. The age of eggs may be approximately determined by the following method, based upon the decrease in the density (through loss of moisture) of the eggs as they grow old: Dissolve two ounces of salt in a pint of water, and when a fresh egg is placed in the solution it will im- mediately sink to the bottom of the vessel. An egg twenty-four hours old will sink below the surface of the water, but not to the bottom of the vessel. An egg three days old will swim in the liquid, and when more than three days old will float on the surface. The older the egg the more it projects above the surface, an egg two weeks old floating on the surface with but very little of the shell beneath the water. . Experiments have been made for the preservation of eggs by dipping them in chemicals, but with no notable success. It is reported that when preserved in lime water, or in a solution of waterglass or by coating with vaseline they will keep for eight months, but dou&tless not with- out some detrimental alteration in taste and flavor. DRYING OF EGG ROOMS, ETC. For the drying of egg rooms, etc., Mr. Cooper recom- mends supporting a quantity of chloride of calcium above the cooling coils, over which the air is circulated by mechanical means. The brine formed by the absorp- tion of moisture by the chloride of calcium will then trickle down over the pipes and thereby effectually pre- vent any formation of frost on the pipes, and therefore keep them at their maximum efficiency at all times, The air, in passing over the brine moistened surface of 196 MECHANICAL REFRIGERATION. the coils, is purified, and the briiie, after falling to the floor of the cooling room, goes to the sewer, and no fur- ther contamination takes place. The re-use of the salt after redrying is objected to by some on account of these contaminations; but it seems to us that they will be ren- dered entirely harmless if the salt is dried at a sufficiently high temperature, and this can hardly be avoided if the water is all driven off, to do which requires calcination at a tolerably high temperature, a temperature which re iar above that at which all germs are destroyed. STORAGE OF MISCELLANEOUS GOODS. ARTICLES. REMARKS. Canned Goods: F. bruits. ... 35 Meats 35 Sardines 35 Flour and Meal: Buckwheat flour , 40 Corn meal 40 Oatmeal 40 Wheat flour 40 Miscellaneous: Apple and peach butter 40 Chestnuts 33 Cigars 35 Furs, woolens, etc 25-32 Furs, undressed , 35 Game to freeze Long storage 0-5 Game, after frozen Short storage 25-28 Hops 33-36 Honey 36-40 Nuts in shell 35-38 Maple syrup, sugar, etc 40-45 Poultry, after frozen '. . '. .Short storage.'.' .'.' .'.' .' .' .' .' .'.' .'.' .'.' .'. 28-30 Poultry, to freeze Long storage 5-10 Syrup 35 Tobacco 35 LOWEST COLD STORAGE TEMPERATURES. Temperatures below zero Fahrenheit are hardly of any utility in cold storage, although in some instances even lower temperatures are produced. A room piped about four cubic feet of space to one lineal foot 1-inch pipe, direct-, ammonia expansion, could be brought to 8 F. below zero. Theoretically a temperature of 28 F. can be produced with ammonia refrigeration at a back pressure equal to that of the atmosphere (and even lower at lower pressures), but practically it is not likely that temperatures lower than 20 F. can be obtained with ammonia, although it may be done by carbonic acid; but as stated before, it is to no purpose as far as cold stor- age is concerned. BREWERY REFRIGERATION. 197 CHAPTER VII. BREWERY REFRIGERATION. PRINCIPAL OBJECTS OF BREWERY REFRIGERATION. The principal uses for refrigeration in a brewery are as follows: First. Cooling of the wort from the temperature of the water as it can be obtained at the brewery to the temperature of the fermenting tuns (about 40 F. ). Second. Withdrawal of the heat developed by the fermentation of the wort. Third. Keeping cellars and store rooms at a uniform low temperature of about 3&~ to 38 F. Fourth. Cooling brine or water to supply attemper- ators in fermenting tubs. Fifth. For the storage of hops and prospectively in the malting process. ROUGH ESTIMATE OF REFRIGERATION. Frequently the amount of refrigeration required for breweries is roughly estimated (in tons) by dividing the capacity of the brewery in barrels made per day by the figure (4). As a matter of course, this can answer only for very crude estimates. For closer estimates the dif- ferent purposes for which refrigeration is required must be considered separately. SPECIFIC HEAT OF WORT. The wort by the fermentation of which the beer is produced consists chiefly of saccharine and dextrinous matter dissolved in water. Its specific heat, which is the chief quality that concerns us now, varies with the Strength of Wort in Per Cent after Balling. Corresponding Sp3ciflc Gravity. . , Corresponding Specific Heat? 8 .0320 .944 9 .0363 .937 10 .0404 .930 11 .0446 .923 12 .0488 .916 13 .0530 .909 14 .0572 .902 15 .0614 .895 16 .0657 .888 17 .0700 .881 18 .0744 .874 19 .0788 .867 20 .0832 .861 amount of solid matter which it contains; this may be ascertained by finding its specific gravity by means of a odccharometer or otner hydrometer. The specific heat 193 MECHANICAL REFRIGERATION. of wort of different strength or specific gravity may be found from the accompanying table. These figures are calculated for a temperature of 60 F. For every degree Fahrenheit that th^ temperature of the wort is below 60, the number 0.00015 must be added to the specific gravity given in above table, and for every degree above the number 0.00015 must be subtracted. Thus the specific gravity of a wort of 13 per cent being acccording to the table 1.0530 at 60, at 50 it would be 60 50=10x0.00015 = 0.0015 more, or 1.0545. PROCESS OF COOLING WORT. The wort as prepared in the brewery is boiling hot, and has to be cooled to the temperature of the ferment- ing tuns. It is first cooled at least, generally so by ex- posing it to the atmosphere in the cooling vat, in which, however, it should not remain over two to three hours, nor at a temperature below 110 F. After this the wort is allowed to trickle over a system of coils through which ordinary cold water circulates by which the temperature of the wort is reduced to that of the water, about 60 F. or thereabouts. A system of coils, generally placed be- low the one mentioned already, finishes the cooling process by reducing the temperature of the wort to about 40 F. or below in ale breweries to about 55 F. This is done by circulating either cooled (sweet) water or refrig- erated brine or refrigerated ammonia through the latter coils while the wort trickles over the same. REFRIGERATION REQUIRED FOR COOLING WORT. The amount of cooling required in this latter opera- tion must be furnished by artificial refrigeration, and its amount expressed in B. T. units, 77, may be calculated exactly if we know the number of barrels, B, of wort to be cooled, its specific heat, s, and its specific gravity, 0, after the following formula: U=B X 259 X g X s (t 40) units, in which t stands for the temperature to which the wort can be cooled by the water to be had at the brewery. To reduce this amount of ^refrigeration to tons of re- frigeration it must be divided by 284,000. SIMPLE RULE FOR CALCULATION. Assuming that the average temperature of the wort after it has been cooled b^ the water as it is obtainable BREWERY REFRIGERATION. 199 at the brewery, is about 70 F., and that the average strength of wort in breweries is between 13 and 15 per cent of extract, corresponding to a specific weight of about 1.05, and to a specific heat of 0.9. the above formula may be simplified and the refrigeration required daily for the cooling of the wort of a brewery of a daily capacity of B barrels, expressed as follows: U= B X 7400 units. Or, expressed in tons of refrigeration, U t In other words, about one ton of refrigeration is re- quired for about thirty-eight barrels of wort under the conditions mentioned. If the water of the brewery cools the wort to 60, one ton of refrigeration would an- swer for about fifty-two barrels of wort. The former figure on one ton of refrigeration for forty barrels of wort is generally adapted for preliminary es- timates. SIZE OF MACHINE FOR WORT COOLING. The capacity of an ice machine is generally expressed in tons of refrigeration produced in twenty-four hours. However, the wort in a brewery must be cooled in a few hours; therefore, in order to find the capacity of the ice machine required to do the above duty the number of tons of refrigeration found to be required to do the cool- ing of the wort must be multiplied by the quotient = in which h means the time expressed in hours in which the cooling of the wort must be accomplished. This of course applies to cases in which a separate machine is used for wort cooling, as is done in large breweries. Frequently the cooling of the wcrt is accomplished by employing nearly the whole refrigerating capacity of the brewery for this purpose for a comparatively short time. INCREASED EFFICIENCY IN WORT COOLING. In these cases, therefore, the total refrigerating ca- pacity of a brewery must never be less than that required to do the wort cooling in the desired time when all other refrigerating activity is suspended during that time. In this connection it should, however, be mentioned that the brine system, as well as the direct expansion system, 200 MECHANICAL, REFRIGERATION. may be made to work with increased efficiency when ap- plied to wort cooling. In the former case this may be accomplished by storing up cooled brine ahead, and in the latter case by allowing the ammonia to re-enter the com- pressor at a much higher temperature after having been used for wort cooling than in other cases. HEAT PRODUCED BY FERMENTATION. The cooled wort is now pitched with yeast and allowed to ferment, by which process the saccharine constituents of the wort are decomposed into alcohol and carbonic acid with the generation of heat after the following formula: C 12 H 22 O llf H 2 0=4 C z H 5 OH+ 4 <70 2 + 66,000 units. Maltose. Alcohol. Carbonic Acid. Heat. In other words, this means that 360 pounds of malt- ose during fermentation will generate 66,000 pounds Cel- sius units of heat, or that one pound of maltose while decomposed by fermentation will generate about 330 B.T. units of heat. CALCULATING HEAT OF FERMENTATION IN BREWERIES. If the weights of the wort and that of the ready beer are determined by means of a Balling saccharometer, and are 6 and 6 t respectively, the heat, H, in B. T. units gen- erated during the fermentation of -B barrels of such wort, may be determined after the formula H= B X 0.91 (&-6J (259+ 6) 330 100 And the refrigeration required to withdraw this heat from the fermenting rooms, expressed in tons, 17, of refrigerating capacity is ' " ; " SIMPLE RULE FOR SAME PURPOSE. Again, if we assume that the wort on an average shows 14 per cent on the saccharometer, and after fer- mentation, it shows 4 per cent, the above formula, giving the refrigeration in tons, IT , in tons required in twenty- four hours to withdraw the heat generated by the fer- mentation of B barreis of wort turned in on an average daily, may be simplified as follows: BREWERY REFRIGERATION. 2 ^ In other words, one ton of refrigerating capacity is re- quired for every thirty-four barrels of beer produced oil an average per day of above strength. This rule will apply to pretty strong beers ; for weaker beer it may be- come much less, so that one ton of refrigeration will answer for fifty barrels, and even more. This shows the importance of this branch of the calculation, which is frequently passed over in a "rule of thumb " way. For preliminary estimates one ton of net refrigerat- ing capacity is allowed to neutralize the heat generated by the fermentation of twenty-five barrels of beer. DIFFERENT SACCHAROMETERS. If in the above determinations of the strength of wort of beer any other kind of saccharometer has been used its readings can be readily transformed into read- ings of the Balling scale, by using the table on the fol- lowing page, which may also be used in connection with the other tables on hydrometer scales in this book. In this way any hydrometer may be made available for the purpose contemplated in the above formula. REFRIGERATION FOR STORAGE ROOMS. Besides the heat generated by fermentation, the heat entering the fermenting and storage rooms from with- out must be carried away by artificial refrigeration, so as to keep them at a uniform temperature of 32 to 38 F. The amount of refrigeration required on this account is also frequently estimated by a "rule of thumb," allow- ing all the way from twenty to seventy units of refrigera- tion for every cubic foot of room to be kept cool during twenty-four hours. The difference in refrigeration is due to the size of the buildings and to the manner in which the walls and roofs are built. Generally thirty units are allowed per cubic foot of space, in rough preliminary estimates, for capacities over 100,000 cubic feet. For capacities between 5,000 and 100,000 cubic feet from forty to seventy units are allowed, and above 100,- 000 from twenty to forty units per cubic foot of space. Sometimes, after another way of approximate figuring, about 20 to 100 units of refrigeration (generally 50) are allowed per square foot of surrounding masonry ceiling and flooring. 202 MECHANICAL REFRIGERATION. TABLES FOB THE COMPARISON OF DIFFERENT SACCHAB- OMETERS AMONG THEMSELVES AND WITH SPECIFIC GRAVITY. Ill *S ,| 2 IT t.3 |^ j 00 . d f If II 1! O 1 too" | 1 a j IS | f|3 2 i i I ft M 1 l co 00 0.00 0.00 1.000 262.41 12.00 17.45 14.64 1.0488 275.21 .25 .36 .30 1.001 262.66 .25 .83 1.0498 275.49 .50 .72 .60 1.002 262 92 .50 18.21 15 '2f 1.0509 275.76 .75 1.08 .90 1.003 263.18 .75 .60 .60 1.0520 276.04 1.00 .44 1.20 1.004 263.45 13 00 .99 .92 1.0530 276.32 .25 .80 .60 1.005 263.71 .25 19.38 16.24 1 0540 276.60 .50 2 16 .80 1.006 263.97 .50 .77 .55 1.0551 276.88 .75 .62 2.10 1.007 264.23 .75 20 16 86 1.0562 277.15 2.00 .88 .40 1 008 264.50 14.00 .55 17.17 1 0572 277.42 .25 3:24 70 1.009 264.76 .25 .94 .48 1.0582 277.68 .60 .60 3.00 1.010 265 02 .50 21.33 .80 1.0593 277.96 .75 96 .30 1.011 265.28 .75 .72 18.12 1 0604 278.25 3.00 4.32 .60 1.012 265.55 15.00 22.11 43 1.0614 278. 62 .25 .68 .90 1 013 265 81 .25 .60 .75 1.0625 278.80 .60 5.04 4 20 1.014 266.07 .50 .89 19 07 1.0636 279 09 .75 .40 .50 1.015 266 33 .75 23.27 .89 1.0646 279.85 4.00 .76 .80 1.016 266.60 16.00 .66 .71 1.0657 279.63 .25 6.12 5.10 1.017 266.86 .25 24 05 20.03 1.0668 279.92 .50 .48 .40 1 018 267.12 .50 .44 .35 1.0679 280.21 .75 .84 .70 1.019 267.38 .75 .83 .67 1.0690 280.60 5.00 7.20 6.00 1.020 267.65 17.00 25.22 21.00 1.0700 280. 77 .25 .56 .30 1.021 267.91 25 .61 .33 1.0711 281.06 .50 .92 .60 1.022 268 17 .50 26 00 .66 1 0722 281.34 .75 8 28 .90 1.023 268.43 .75 .39 .99 1.0733 281 63 6.00 .64 7.20 1.024 268 69 18.00 .78 22.32 1-0744 281.92 .25 9 00 .50 1 025 268 96 .25 27.17 .65 1.0755 282.21 .50 .36 80 1.026 269 2-7 50 .56 .98 1.0766 282.60 .75 .72 8.10 1.027 269 48 .75 .96 23.31 1.0777 282.78 7.00 10.08 40 1 028 269 74 19 00 28.36 .64 1.0788 283 08 .25 .44 .70 1.029 270.00 .25 .76 .97 1.0799 283 37 .50 .80 9.00 1 030 270.27 .50 29.16 24.30 1 0810 283.65 .75 11.16 .30 1.031 270.53 .75 .56 .63 1.0821 283.93 8.00 62 .60 1.032 270.79 20.00 .95 .96 1.0832 284.21 .25 .96 .96 1.0332 271 11 .25 30.34 25.29 1.0843 28449 .60 12.32 10 26 1.0342 271.37 60 .73 .62 1.0854 284. 77 .75 .68 .57 1 0352 271 64 .75 31.12 .95 1.0865 285.05 900 13 04 .88 1.0363 271 91 21,00 .60 26.27 1 0876 285.33 .25 .40 11.19 1 0374 272.19 .87 .60 1.0887 286.62 .50 .76 .50 1 0384 272 47 '.50 32 25 93 1.0898 285.91 .75 14.12 .81 1.0394 272.74 75 64 27.26 1.0909 286 Iff 10.00 .48 12.11 1.0404 273.00 22 00 33.04 .69 1.0920 286.47 .25 .84 42 10415 273.28 .25 .44 .92 1.0931 286.77 .60 15.21 .73 1 0425 273.56 .50 .84 28.25 1.0942 287 06 75 .58 13 06 1.0436 273.84 .75 34.23 .68 1.0953 287.36 11.00 .95 .37 1.0446 274 H 23.00 .63 .91 1.0964 287.66 .25 16.32 .68 1.0457 274 39 .25 35.03 2924 1 0976 288.96 .50 .69 1400 1.0467 274 66 .50 .43 .67 1.0986 288 20 76 17.07 .32 1.0478 274.94 75 83 .90 1.0997 288.50 24.00 36.23 30.23 1.1008 288 80 CLOSER CALCULATION. For calculations required to be more exact the power for transmission of heat by the walls and windows, as well as the difference of temperature within and without, must be taken into consideration. BREWERY REFRIGERATION. 203 For calculations of this kind the same rules apply which have been given under the head of cold storage, pages 153, etc. The number of units of refrigeration found to be required must be divided by 284,000 to express tons of refrigeration. COOLING BRINE AND SWEET WATER. The amount of refrigeration required to cool brine or sweet water to supply the attemperators in the fer- menting tubs is included in the estimate for the refriger- ation required to neutralize the heat of fermentation. TOTAL REFRIGERATION. Therefore the total amount of refrigeration required is composed of the first three items mentioned in the second paragraph of this chapter, and by adding them we find the actual capacity of the machine or machines required in a given case. It may be verified in accordance with the considerations mentioned in the paragraph on "Increased Efficiency for Wort Cooling." DISTRIBUTION OF REFRIGERATION. The practical distribution of the refrigeration in the brewery is carried out on different principles, and should follow the figures obtained in the above calculations. Formerly the cooling of rooms in breweries was fre- quently effected by the circulation of air, which was furnished direct by compressed air refrigerating ma- chines. Later on the air to be used for this purpose was refrigerated in separate chambers with the aid of am- monia compression machines. At present, however, the chief means for cooling brewery premises are coils of pipe into which the ammonia is allowed to expand di- rectly as it leaves the liquid receiver. These coils are generally placed overhead, in which position they assist greatly in keeping the air dry. DIMENSIONS OF WORT COOLER. The amount of refrigeration destined to do the cool- ing of the wort takes care of itself, provided the cooler, which, as already described, is generally constructed after the Baudelot pattern, is large enough to do the cooling in the proper time. The proportions frequently employed for the ammonia portion of the wort cooler are 204 MECHANICAL REFIJGERATION. about teu lengths of 2-inch pipe, each length sixteen feet long, for fifty barrels of wort to be cooled from about 70 to 40 F. within three to four hours. For 100 barrels of wort to be cooled the ammonia por- tion of the cooler consists of fourteen lengths of pipe six- teen feet long; for 180 barrels,of fifteen lengths twenty feet long; and for 360 barrels, twenty lengths twenty feet long, all pipes to be 2-inch. These are practical figures, and given with a view to afford ample cooling surface. The amount of refrigeration which must circulate through the wort cooler within that time has been deter- mined by the above calculation. In the case of brine circulation, salt brine being used in the wort cooler, the surface of pipe should be made 20 percent more than given above; in other words, a cooler of the above dimensions will answer for forty barrels of wort, instead of fifty, in case brine circulation is used. DIRECT EXPANSION WORT COOLER. In case of brine circulation, to which the foregoing dimensions apply, the pipes of the wort cooler may be of copper, but in case of direct expansion being used, the inside of the pipes cannot be copper, but must be iron or steel, and, therefore, copper plated steel pipe or polished steel pipe is used in this case, the latter being given the preference by most manufacturers on account of cheap- ness and relative efficiency. The ammonia portion of the wort cooler should be made in two or more sections, having separate and direct connections for inlet of liquid ammonia and outlet of ex- panded vapor. PIPING OF ROOMS. The balance of refrigeration, that is, the whole amount, less that used for wort cooling, must be dis- tributed over the store and fermenting rooms in due pro- portion. In doing so the time within which the refrigera- tion is to be dispensed must be considered foremost. The subsequent figures are based on the assumption that dur- ing every day the machine or brine pump is active for twenty-four hours to circulate refrigeration; if less time is to be used for that purpose more distributing pipe must be used in proportion. As a general thing too much piping cannot be em- ployed, for the nearer the temperature of the room to be BREWERY REFRIGERATION. 205 cooled is to that within the pipe, the more economical will be the working of the ice machine. In case of direct expansion it is frequently assumed that in order to properly distribute one ton of refrigera- tion about storage and fermenting rooms, it will require a pipe surface of 80 square feet, which is equivalent to 130 feet of 2-inch pipe, and to about 190 feet of 1^-inch pipe. Smaller pipe than that it is not advisable to use. If radiating disks are employed less pipe may be used. For brine circulation much more piping, even as much as 200 square feet of surface, are allowed per ton of refrigeration to be distributed. In very close calculations allowance should be made for the difference in temperature in the different vaults, which for fermenting rooms is about 42 F., for storage rooms about 33- F., and for final storage or chip cask about 37 F. HEAT OF FERMENTATION AGAIN. In addition to the piping allowing for the transmis- sion of heat through the walls, the balance of piping, i. e., that which is to convey the refrigeration required to neutralize the heat during fermentation, must be appor- tioned according to the amount of heat which is de- veloped in the different rooms. This can also be calcu- lated very closely after the above rules, if the method of fermentation to be carried on is known. But as a rule this is not the case, and to supply this deficiency it may be assumed that from the heat gener- ated during fermentation about four-fifths is generated in the fermenting room, and about one-fifth in the ruh and chip cask cellar together. In this proportion the ad- ditional piping in these rooms may be arranged after due allowance has been made for the refrigeration conveyed by the attemperators. EMPIRICAL RULE FOR PIPING ROOMS. More frequently than the foregoing method empirical rules are followed in piping rooms in breweries, it being assumed that nearly all of the heat generated in the fermenting room proper (during primary fermentation) is carried off by the attemperators. On this basis it is fre- quently assumed that one square foot of pipe surface will cool about 40 cubic feet of space in fermenting room, and about 60 to 80 cubic feet of space in ruh and chip cask cellar (direct expansion). 206 MECHANICAL REFRIGERATION. These figures then apply to direct expansion; for brine circulation, about one-half of the above named spaces will be supplied by one square foot of refrigerating surface. This figure appears to contemplate a range of about 9F. difference between the temperature of rooms and that of refrigerating medium within pipe. Much more and much less pipe is frequently used for the same pur- pose, which is to be accounted for by reasons given on pages 135 and 136. Here we allow more space per square foot of refriger- ating pipe surface than is done in the rule at the bottom of page 135 for storage rooms in general to keep the same temperature. This is partially explained by the fact that brewery vaults are less frequently entered from without, and that their contents are less frequently changed than is the case with general storage vaults. Furthermore it is evident that the size of vaults is also a matter for consideration in this respect. ATTEMPERATORS. The attemperators are coils of iron pipe, one to two inches thick, the coil having a diameter of about two- thirds of the diameter of the fermenting tub, in which it is suspended, and a sufficient number of turns to allow about twelve square feet pipe surface per 100 barrels of wort> corresponding to about nineteen feet of 2-inch pip*. The refrigeration is produced by means of cooled water or brine circulating through the attemperators. The attemperators are suspended with swivel joints so that they can be readily removed from the fermenting tub. There is a great variety in the form of attemperators, box or pocket coolers being also frequently used. On the whole the pipe attemperator as described seems to be the simplest and most popular. It has also been proposed (Galland) to cool the fer- menting wort by the injection of air, purified by filtration through cotton and refrigerated artificially. This plan, however, does not seem to be followed practically to any great extent. REFRIGERATION FOR ALE BREWERIES. While the general calculations relating to heat of fermentation, cooling of the wort and cooling of rooms are the same for ale as for lager beer, the specific data relating to piping, etc., in above paragraph, are given BREWERY REFRIGERATION. 207 with special reference to lager beer, and must be modified when applied to ale. This is due to the fact that the ale wort is cooled to a temperature of about 55 F. only, and that the storage rooms are to be kept at a temperature of 50 F., or there- abouts. Accordingly, for ale wort cooling one ton of refriger- ation will be required for every seventy -five barrels. For keeping the rooms at the temperature of 50 about twenty B. T. units and less of refrigeration for every cubic foot in twenty-four hours will be sufficient. The refrigeration necessary to remove the heat of fermentation is calculated in the same manner as above. The piping of store rooms in ale breweries is fre- quently done at the rate of one running foot of 2-inch pipe per sixty cubic feet of space. The tables on refrigeration and piping discussed in the chapter on cold storage may also be consulted in this connection. SWEET WATER FOR ATTEMPERATORS. The circulation of refrigerated brine in the attem- perators is not considered a safe practice by brewers in general, as a possible leak of brine would be liable to cause great damage to the beer. For this reason cooled or ice water (it is also termed sweet water to distinguish it from salt water or brine) is circulated in the attem- perators, generally by means of an automatic pump which regulates the proper supply of sweet water to the attemperators, no matter how many or how few of them are in operation at the time. The ice or sweet water is cooled in a suitable cistern or tank which contains a cooling pipe in which ammonia is allowed to expand di- rectly, or through which refrigerated brine is allowed to circulate. In some breweries the wort is also cooled by refrigerated sweet water made in the above way. This method absolutely precludes the possibility of contami- nation of ammonia or brine, but at the same time it is very wasteful in regard to the very indirect mode of ap- plying the refrigeration 1 , and for this reason brine in cir- culation is now mostly used for this purpose, experience having shown that the danger of contamination is prac- tically excluded. 208 MECHANICAL REFRIGERATION. CHILLING OF BEER. Recently it has been found desirable to subject the ready beer to a sort of chilling process immediately before racking it off into shipping packages. This pro- cess, however, is of no practical utility if the beer is not filtered after it has been chilled and before it goes into the barrels. In this case much objectionable albuminous matter, still contained in the ready beer, is precipitated by chilling and separated from the beer by filtration, while without filtration this matter would redissolve in the beer and cause subsequent turbidities, especially if the beer is used for bottled goods. BEER CHILLING DEVICES. The chilling was first effected by passing the beer through a copper worm placed in a wooden tub which was filled with ice. But by this the desired object was attained only partially. Therefore, the ice was mixed with salt to obtain a still lower temperature in the beer passing through the worm. Still more recently, and of course in all breweries where mechanical refrigeration is employed, the pipes through which the beer passes are cooled by brine or by direct expansion. Special apparatus are also made for this purpose, and generally consist of a series of straight pipes provided with manifold inlet and outlet, and placed in a cylindrical drum, through which refrigerated brine or ammonia is allowed to pass in a direction opposite to the beer. COOLING OF WORT. Coolers of the same construction are now also fre- quently used for wort cooling instead of the Baudelot coolers. For both purposes, i. e., the chilling of the ready beer and the cooling of the wort, the refrigerated brine appears to act as the best cooling medium, at least so with some makes of this kind of coolers as they are constructed and operated at present. If direct expansion is used it has been found impracticable (at least in the cases reported to the author) to effect a thorough chilling in the desired time. If used for wort cooling, direct expansion has also caused some trouble when used with some kinds of these new coolers, but it has been overcome in a measure by allowing the ammonia to enter the cooler almost OUP- half to one hour before the wort is passed through the same. BREWERY REFRIGERATION 209 SAFEGUARDS TO BE EMPLOYED. It has also been experienced that the expanded ammonia, especially if the expansion valve (one of which must be provided for each of these coolers) is not mani- pulated very carefully, enters the compressor in an over- saturated condition if allowed to pass directly to the same. Under such conditions the compressor will oper- ate in an irregular manner, and even the cylinder head may be blown out in extreme cases. To guard against such calamities it is necessary to carry the expanded ammonia to the compressor in proper condition by allow- ing the same to mix with the expanded ammonia coming from the expansion pipes in other parts of the brewery, before reaching the compressor. To do this the ex- panded ammonia from the wort cooler and that from the cellar may enter a common conduit pipe at a sufficient distance from the compressor to insure a thorough mix- ture of the gases. CAUSES OF TROUBLE. The foregoing contains, we believe, the principal safeguards known at present to be of service to over- come the troubles with these coolers; troubles which, while they are not gainsaid by their makers, are never- theless, we understand, declared by some of them so paradoxical in their action that they upset the entire theory of transmission of heat as given by the scientists at present. On the other hand, and to partly offset a statement so derogatory to the engineering profession, it may be permissible to suggest that the chief of the apparatus makers, while being expert practical copper- smiths, are perhaps not sufficiently versed in the intricate details offered by problems of heat transmission to give the construction of apparatus of a novel tendency the proper consideration. It is not unlikely that the relative sizes of direct expansion pipes and brine pipes in the refrigeration of rooms have been taken as cases parallel to these coolers, while in fact the transmission of heat proceeds at a rate entirely different in both cases. DIRECT REFRIGERATION. Instead of refrigerating the fermenting and storage rooms of the brewery it has also been proposed to refrig- erate the contents of the tubs and casks separately and in a more direct manner, just as the surplus heat of fer- 210 MECHANICAL REFRIGERATION. meriting tubs is now withdrawn, by means of attempera- tors or similar devices. At first sight there would seem to be a source of considerable saving in this proposition, but it would be at the expense of cleanliness, dryness and reliable supervision of the brewery. Therefore it must be considered a change of very doubtful expediency. BREWERY SITE. In former times it was generally considered that the best location for a brewery site was on a hill side, to enable the fermenting and storage rooms to be built into the hill into natural rock, in order to profit by the natural low underground temperature in the summer and the higher underground temperature in the winter time; in other words, by the even temperature all the year around. This position was certainly well taken when the beer was made exclusively by top fermenta- tion, and the position still holds good in a measure for ale breweries. As the great majority of breweries, how- ever, are operated for the production of lager beers which have to ferment, and are stored at temperatures much lower than those obtaining in natural vaults (at least, in the moderate zones), artificial refrigeration or ice has to be resorted to. In either case the natural vaults offer very little advantage to overground structures, well insulated, especially if the larger cost of construction of natural vaults, their inconvenience as to room, and generally also as to accessibility, is considered. For these reasons the site for a brewery nowadays is generally selected with sole reference to convenience as to sriipr- ment of produce, reception of material and quality and accessibility of water supply. ICE MAKING AND BREWERY REFRIGERATION. Very frequently it happens that a brewery is to be operated in connection with an ice plant, and, generally speaking, it is doubtless not only more convenient, but also good economy to have more than one refrigerating machine in such cases on account of different expansion or back pressures that we have to work with. STORAGE OF HOPS. To keep hops from degeneration their storage at 32 34 F, in a dry, dark, insulated room has been found the only successful way. The hops should be well dried, sulphurized and well packed before being placed in cold storage. Artificial refrigeration, as well as ice, may be BREWERY REFRIGERATION. 211 used, but special precaution has to bo used to keep the room dry in the latter case. REFRIGERATION IN MALT HOUSES The cold air which is required in malting, especially in the so called pneumatic methods of malting, it has also been proposed to furnish by means of refrigerating machinery, but it does not appear that it can be done successfully from a financial point of view, except, perhaps, under very exceptional circumstances. ACTUAL INSTALLATIONS. The following figures are taken from actual meas- urements of an existing installation in a brewery having a daily capacity of 375 barrels lager beer, which has the following appointments : One ammonia compression machine of fifty tons, chiefly for wort cooling, direct expansion, reduces tem- perature of whole output, 375 barrels, from 70 to 40 F. in four hours (the ammonia portion of Baudelot cooler consisting of twenty pieces of 2-inch pipe, each twenty feet long). One ammonia compression machine, 50 tons capacity, for storage atteniperators, etc. (direct expansion). Fermenting room, 90x75 feet, fourteen feet high, is piped at the rate of one foot 2-inch pipe for every twenty-seven cubic feet space. Each one of the sixty- five fermenting tubs contains an attemperator coil of twenty-one feet 2-inch pipe. Ruh cellar, 90X74 feet, and twenty feet high, is piped at the rate of one foot 2-inch pipe for every forty cubic feet of space. Chip cask cellar, 90x73 feet, and sixteen feet high, is piped at the rate of one foot. 2-inch pipe for every fifty- two cubic feet of space. A fifty-barrel lager beer brewery was equipped with machinery to furnish refrigeration in accordance with the following estimates : 3,200,000 B. T. units for storage. 416,000 B. T. units for cooling wort. 300,000 B. T. units for attemperators. Total, 3,916,000 B.-T. units=13.8 tons, or in round figures equal to fifteen tons refrigerating capacity. The whole capacity is calculated to cool the wort in four hours. 212 MECHANICAL REFRIGERATION. CHAPTER VIII. REFRIGERATION FOR PACKING HOUSES, ETC. AMOUNT OF REFRIGERATION REQUIRED. The application of refrigeration in slaughtering and packing houses is quite similar to its application to cold storage in general, and the amount of refrigeration re- quired in a -special case may be estimated on the same principles. THEORETICAL CALCULATION OF SAME. The refrigeration required to keep the rooms at the required temperature is found after the rules given on pnge 173, etc. The additional refrigeration to chill or freeze the meat can be calculated after the rules given on page 183, etc. PRACTICAL RULES FOR SAME. The temperature of the chilling rooms is below 32 F. and the fresh slaughtered meats are stored in them until they have acquired the storage temperature in storage rooms, to which they are then removed. For practical estimates it is frequently assumed that a refrigeration equivalent to about 80 B. T. units is re- quired for every cubic foot of chilling room capacity in twenty-four hours. The refrigeration for meat storage rooms is the same as that required for ordinary storage, i. e., from 20 to 50 units (40 units being calculated on an average) for every cubic foot of space in twenty-four hours. For crude estimates calculations are frequently made on the basis of allowing 3,000 to 5,000 cubic feet space per ton of refrigeration in twenty-four hours in chilling rooms, and 5,000 to 8,000-cubic feet space per ton of refrig- eration in twenty-four hours in storage rooms, accord- ing to insulation, size of rooms and other conditions. FREEZING ROOMS. The freezing of meat is performed in rooms kept at a temperature of 10 F. and below. Considerable additional refrigeration is required for freezing, not only on account of the latent heat of freezing, which has to be withdrawn, but also on account of the low temperature at which the rooms have to be kept. For rough estimates at least 200 REFRIGERATION FOR PACKING HOUSES- 213 B. T. units of refrigeration should be allowed for every cubic foot of freezing room capacity. CALCULATION PER NUMBER OF ANIMALS. If the average number and kind of animals to be dis- posed of daily in slaughtering house is known, calcula- tions are also made on a basis similar to the following: From 6,000 to 12,000 cubic feet of space are allowed per ton of refrigerating capacity to offset the loss of refrig- eration by radiation through walls and otherwise, and in addition to that, the extra refrigeration to be allowed in the chilling room for the chilling proper is arrived at in accordance with the assumption that one ton of refriger- ation will take care of the chilling of 15^24 hogs (average weight, 250 pounds). 5- 7 beeves (average weight, 700 pounds). 45-55 calves (average weight, 90 pounds). 55-70 sheep (average weight, 75 pounds). In actual freezing one ton of refrigeration will take care of one ton of meat (in twenty-four hours). PIPING OF ROOMS. The piping of rooms in packing houses may be ar- ranged after rules referred to already. Not infrequently, however, other empirical rules are followed, viz.: For chilling rooms, for instance, one running foot of 2-inch pip'e (or its equivalent) is allowed for thirteen to fourteen cubic feet of space ; that is, in case of direct expansion, and for seven to eight cubic feet of space for brine circulation. For storage rooms, one running foot of 2-inch pipe is allowed for forty-five to fifty cubic feet in case of di- rect expansion, and for fifteen to eighteen cubic feet in case of brine circulation. . For freezing rooms, one running foot of 2-inch pipe is allowed for six to ten cubic feet of space for direct expansion, and for three cubic feet of space in case of brine circulation. Others proportion the piping by the number of ani- mals slaughtered, allowing thirteen feet of 2-inch pipe per ox, and six feet 2-inch pipe per hog in case of direct expansion in chilling room. In case of brine expansion thirteen feet 1^-inch pipe are allowed per hog, and twenty-seven feet 1^-inch are al- lowed per ox in chilling room. (Large installations.) 214 MECHANICAL REFRIGERATION, STORAGE TEMPERATURES FOR MEATS. The temperatures considered best adapted for the storage of various kinds of meats are given in the follow- ing table: ARTICLES. P. Brined meats . .... a5-40 Beef, fresh 37-39 Beef, dried 36^5 Hams, ribs, shoulders (not brined) 30-35 Dogs 30-33 Lard 34-45 Livers 30 Mutton 32-36 Oxtails , 33 Sausage casings 30-35 Tenderloins, butts, ribs 30-35 Veal 32-36 OFFICIAL VIEWS ON MEAT STORAGE. . The report of an official commission created by the French government to investigate the cold storage of meats, etc , closes with the following conclusions : First. Whenever meat is to be preserved for a com- paratively short time, for market purposes, the animals being slaughtered close to the cold storage or not having to be transported, after slaughtering, for a distance in- volving more than a few hours (as much as twelve), in transit, congelation is not required to insure the con- servation. It should be avoided, as by such a practice, that is, the temperature being kept in the storage above the freezing point, the meats are sure to retain all ^heir palatable and merchantable qualities. Second. In special circumstances, such as for a pro- tracted conservation, in case of a transportation of the slaughtered animals from very long distances, involving days or weeks in transit, congelation appears to be pref- erable and safer It does not necessarily render the meats less merchantable, wholesome or palatable, if they are frozen and thawed out, very slowly, gradually and carefully; and only after they have been deprived partially of the excess of moisture of their tissues. Third. Cold, dry air should be the vehicle of cold; it should circulate freely around the meats. FREEZING MEAT. The same commission recommends that in case the meat must be frozen it should be done in such a way that the fiber is not altered; it should preserve its elasticity as long as possible, up to the very moment when the liquid elements of the meat begin to solidify, so that, at the REFRIGERATION FOR TACKING HOUSES. 215 point of congelation, the dilatation of the water, in changing state, should not cause the bursting of the or- ganic cells, leaving a uniform mass of disagreeable ap- pearance at the thawing out. The congelation must proceed very slowly from the start, progressing gradually and very regularly through the mass, as soon as the freezing point has been reached; the temperature should be carefully watched, very evenly lowered without any sudden depression. Once congealed, the temperature of the meats can be carried very low without detriment. CIRCULATION OF AIR IN MEAT ROOMS. The required circulation of air in the meat rooms is either produced by natural draft or (especially in Europe) by means of blowers or fans, which circulate air, cooled artificially. The cooling of air used for the latter purpose is generally done in a separate room in which the air is brought in contact with the surfaces of pipes which are refrigerated by direct ammonia expansion. The warmer air is continuously exhausted from the meat rooms by means of a blower, which forces it through the cooling apparatus and thence back to the meat' rooms in a cold and dry condition. See also what has been said on ventilation, etc., in the chapter on cold storage. BONE STINK. As already stated, the freezing of meat must be done very carefully, in order to avoid any injury to the meat. Moro particularly the chilling and freezing must be done very gradually, for when the meat is plunged at once in a chamber below the freezing point, the external parts are frozen more quickly than the internal parts, and the latter are cut off by this external frozen and poorly con- ducting zone from receiving the same intensity of cold. The external frozen zone contracting on the internal portion causes many of the cells to be ruptured and the contents to escape, and on cutting into meat so frozen a pulpy consistency of the meat is found near the bones. This is particularly the case when whole carcasses are treated, but also parts of the animal show similar defects when frozen carelessly. The so called "bone stink," which shows itself as decaying marrow in the interior of the bones of many frozen meats, is also gen- erally due to the too hasty freezing. However, the con- dition of animal at the time of killing (exhaustion by a 216 MECHANICAL REFRIGERATION. long journey, injudicious feeding, excitement, delay in skinning, etc.) appears to favor the liability to bone stink. Hanging the animals too closely together after they are slaughtered and dressed is said to be a fruitful source of bone taint, for when they are throwing off the animal heat and gases contained in the bodies, if hung too closely together they will steam one another and prevent this animal heat and gas from getting away. The ab- sence of proper ventilation and an insufficient circulation of fresh air is also a likely cause, bearing in mind that what has to be aimed at is the driving away of this ani- mal heat and gas as it passes out of the carcass. While the temperature of the cooling chamber should be kept moderately low, it should not be too low; a free circula- tion being of far more importance than lowness of tem- perature during this early cooling or chilling process. Bone taint can be detected without actually cutting up a carcass, in the following way: A long wooden skewer is inserted at the point of the aitch bone; this passes the cup bone and enters the veins that divide the silver side from the top side, where, if any taint exists, it is sure to be found, the wooden skewer bringing out the taint upon it. For testing while in a frozen state a carpenter's brace and bit should be used. This must be inserted as above described. FREEZING MEAT FROM WITHIN. It has also been proposed to prevent the bone stink, etc., by freezing meat from the center by introducing into the same a pipe shaped like a hollow sword divided by a partition around which refrigerated brine or am- monia is permitted to circulate. DEFROSTING OF MEAT. The importance of doing the defrosting of meat with the same care as the freezing is well illustrated by a number of patents taken out for this operation. One of these processes subjects the meat to a continuous circu- lation of dry air formed by mixing cold air at a tempera- ture of 19 and dry air heated to 70, the combined cur- rent at about 26, increased to about 60, being forced through the thawing chamber by a fan. Time required for thawing, two to five days. This process is in use at Malta and Port Said. Another patent provides for the circulation of air, REFRIGERATION FOR PACKING HOUSES. 217 dried by arrangement of pipes containing cooling me- dium, and suitably heated by steam pipes, passing over the meat by natural means, and, by gradually increasing temperature, abstracting the frost without depositing moisture. Time required for defrosting: Beef, four days; bheep, two days. Process has been in continuous use in London for two and one- half years; it is also used in Paris and in Malta for meat supplied to troops. MOLDY SPOTS ON MEAT. The white mold spots which sometimes form on meat in cold storage are due to the growth of a fungus (Oidium attncans) the germs of which are quite common in the air. For this reason the formation of this mold may be prevented by providing a circulation of air which has passed over the cooling pipes (St. Glair's system, described under "Cold Storage") , by which the moisture and mold germs are withdrawn from the air. KEEPING OF MEAT. Meat, if kept constantly at 31 in a properly venti- lated room from the time it has been slaughtered can be kept fresh at least six months, ')ut if the temperature goes up at times as high as even only 33 the meat might not keep over a month; however, if the ventilation and humidity are properly regulated it should keep about two months in good condition in the latter case. Beef should be placed in cold storage within ten hours after killing. SHIPPING MEAT. Meat properly prepared may be kept at a tempera- ture between 32 and 35 F. for any length of time, but to insure against a break down of the refrigerating ma- cmnery aboard the vessel, the meat is generally frozen be- fore it is loaded, thus providing for a deposit of cold (100 tons of frozen meat being equivalent for refrigerating purposes to seventy tons of ice) that can be drawn on in case the machinery fails temporarily. REFRIGERATION FOR OTHER PURPOSES. From the data, rules and examples given under the heads of cold storage, packing house and brewery re- frigeration, and on refrigeration in general, it will be practicable to make the required approximate estimates for most of the other numerous applications of refrig- erating machinery. 218 MECHANICAL REFRIGERATION-. REFRIGERATION IN OIL WORKS. In oil refineries artificial refrigeration has become indispensable for the purpose of separating the parafflne wax and refining the oil. Stearline, India rubber works, etc., can no longer be without artificial refrigeration. DAIRY REFRIGERATION. In the dairy practice, the cooling and freezing of milk, in butter making, etc., there is a great future for artificial refrigeration. Refrigeration has also been patented for the special purpose of freezing the water out of milk in order to concentrate the same without heat. REFRIGERATION IN GLUE WORKS. Some glue manufacturers have found it to their in- terest to improve their product by drying their gelatine in looms artificially refrigerated, thus permitting them to use glue solutions less concentrated. VARIOUS USES OF REFRIGERATION. Manufacturers of oleomargarine, of butterine, soap, chocolate, etc., derive great benefit from artificial refrig- eration. For seasoning lumber it is also employed to some extent already. Skating rinks, ice railways, etc., are kept in working order all the year now by artificial refrigeration. Young trees are kept in cold storage to hold back unseasonable and premature growth. The preservation of the eggs of the silkworm, so as to make the eclosion of the eggs coincide with the ma- turity of leaves of the mulberry tree has also become a subject of artificial refrigeration. Many transatlantic vessels are equipped with gigantic refrigerating apparatus to enable them to transport per- ishable goods, chiefly meat, but also fruits, beer, etc. In dynamite factories for maintaining the dynamite at a low temperature during the process of nitrating. In manufactories of photographic accessories, for cooling gelatine dry plates. In the establishments of wine growers and merchants for reducing the temperature of the must or unfer- mented wine, and for the obtainment of an equable tem- perature in the cellars, etc. Wool and woolen garments, as likewise furs and peltry, are preserved from the attacks of moths by artifi- cial refrigeration. KBPBIGERATION FOR PACKING HOUSES. 219 Beds in summer time may be cooled by pans filled with ice in the same way as they are warmed by warm ing pans in winter. This cooling of beds is said to pro- duce immediate sleep and rest, and is Especially recom- mended in cases of insomnia and other afflictions. Decorative effects, quite novel and artistic, to adorn the dining table, etc., may be produced by freezing flow- ers, fishes, etc., tastefully grouped in clear crystal ice blocks of convenient shapes. For refrigeration of dwellings, hospitals, hotels, pub- lic institutions, etc.: This subject has been much written about, but in the practice of refrigerating dwellings and hotels during the hot season little progress has been made so far, many being of the opinion that it would be too expensive for general use. While this may be so, there is doubtless a great field open in this direction for the application of refrigeration in those cases in which expense is a second- ary consideration. The value of ice in therapeutics is. generally recog- nized. From among the more recent applications in this direction may be mentioned the following : Ice is used for the induction of failing respiration by rubbing slowly the mucous membrane of the lips and mouth with a piece of ice to the rhythm of normal respiration. Ice is said to moderate inflammation of the brain or its membranes, and also the severe headache of the early stages of acute fevers, also to relieve the pain and vomit- ing in cases of ulcer or cancer of the stomach. It is also-excellent for the sore throat of fevers, and in cases of diphtheria. Sucked in small pieces, it checks secretions of the throat. Ice also arrests hemorrhage in a measure. Artificial refrigeration is also very extensively used m the shipping of all sorts of produce, especially meat, eggs, etc., and the refrigerating installations in vessels crossing the ocean, and in railroad cars crossing the plains, are subjects of special study and detail which it would be beyond the scope of this book to enter into, here. We may add, though, that the refrigeration during transit is not confined to railroad cars and steamboats, but that small delivery wagons for meat, eggs, etc., are now constructed with special reference to the keeping of their refrigerated contents until delivered to the con- sumer or retailer. 220 MECHANICAL REFRIGERATION. In distilleries for keeping the spirits in the store tanks cool during hot weather, and thereby obviating the very serious loss that is otherwise experienced through evaporation. In chocolate and cocoa manufactories to enable the cooling room to be maintained at a low temperature in summer, and the process to be worked continuously all the year around. A great saving is likewise effected by the rapid solidification which is rendered possible, and the waste thus avoided; and furthermore, as the choco- late leaves the molds readily and intact, a considerably fewer number of the latter are required to do the same amount of work. In sugar factories and refineries for the concentra- tion of saccharine juices and solutions by freezing or congealing the water particles, which are then removed, leaving the residuum of a greater strength. In India rubber works for the curing and hardening of India rubber blocks, thereby facilitating the cutting of same into sheets for manufacture of various elastic articles. The material in that state admitting of its be- ing worked up in a much superior manner, and, more- over, at a far lower cost REFRIGERATION" IN CHEMICAL WORKS. Some of the chemical industries in which artificial refrigeration is extensively used have been mentioned al- ready, and to these may be added ash works, asphalt and tar distilleries, nitroglycerine works, etc. In fact, all chemical operations which depend largely on differences in temperature, notably all those involving crystalliza- tion processes, can in most cases be greatly assisted by the use of artificial refrigeration. This is particularly true of substances which it is difficult to obtain in a pure state, and which do not pass into the solid state, except at very low temperature. To successfully purify such sub- stancesand there are a great many of them artificial refrigeration is the most valuable auxiliary, and very re- markable results have been obtained already in this direc- tion. The most successful purification of glycerine is an instance of this kind. Chloroform is another still more re- markable example. This substance, although considered pure, was nevertheless of a very unstable character. Time, action of light, heat and other unavoidable conditions. REFRIGERATION FOR PACKING HOUSES. 221 caused its degeneration, until it was shown by Pictet that an absolutely pure article of chloroform could be obtained by crystallizing the same at a temperature of about 90 P . This is a very low temperature, considering practical possibilities of the present day, but it accomplishes the object, and there are many more equally useful applica- tions not yet thought of, or beyond the reach of practical refrigeration at present. CONCENTRATION OF SULPHURIC ACID. The concentration of sulphuric acid, which is accom- plished in expensive platinum vessels, can be accom- plished, according to Stahl, in leaden vessels, if artificial refrigeration is used to crystallize the strong acid, which can then be separated from the weak mother acid. Another interesting chemical change brought about by artificial refrigeration is the decomposition of the acid sulphate of soda into neutral salt and free sulphuric acid. DECOMPOSITION OF SALT CAKE. Another interesting application of refrigeration in chemical manufacturing is the decomposition of the so called salt cake (acid sulphate of soda) into sulphuric acid and neutral sulphate of soda, which takes place when a watery solution of the said salt is subjectecTto a low temperature. PIPE LINE REFRIGERATION. In many cities refrigeration is furnished to hotels, butchers, restaurants, private houses, etc., by a pipe line which carries liquid ammonia; another pipe line return- ing the expanded ammonia to the central factory, at which a large supply of liquid ammonia is kept in store to regulate inequalities in the demand for refrigeration. REFRIGERATION AND. ENGINEERING. When making excavations in loose soil, it has been found expedient to freeze the ground by artificial refrig eration, and this artifice is now extensively applied in mining operations, in the sinking of bridge piers, in tun- neling through loose or wet soil, etc. One of the greatest pieces of engineering with the aid of refrigerating machinery was accomplished about two years ago in the opening of a coal mine in Anzin, Franco. The coal was over 1,500 feet below the surface, and below strata strongly saturated with water, and im- passable without artificial solidification. 222 MECHANICAL REFRIGERATION. CHAPTER IX. THE ABSORPTION SYSTEM. THE CYCLE OF OPERATIONS. As in the compression system of ammonia refrigera.- tiou, the operations performed in the absorption system constitute what has been termed a cycle of operations, the working medium, ammonia liquor, returning period- ically to its initial condition, at least theoretically so. A COMPOUND CYCLE. It is, however, not a reversible cycle, but rather two cycles merged into one, or a compound cycle. The anhy- drous ammonia after leaving the still at the top, passes i hrough the analyzer, condenser, receiver and refrigera- tor to the absorber, where it meets the weak liquor com- ing through the heater and exchanger from the still, and then after having been absorbed by the latter, passes as rich liquor from the absorber through the ammonia pump to the exchanger, and through the heater to the still, entering the latter by first passing through the analyzer, generally located at the top of the still. APPLICATION OF FIRST LAW TO CYCLE. Owing to the complexity of the operations of the double or compound cycle, its theoretical working condi- tions cannot be expressed by so simple a formula as in the case of a reversible cycle. Nevertheless, the tenets of the first law of thermodynamics apply in this case also, and therefore the heat and work which is imparted to the working substance while performing the operations of one period of the cycle must be equal or equivalent to the heat and work which are withdrawn during the same period all quantities to be expressed by the same kind of units. EQUATION OF ABSORPTION CYCLE. Hence, if W\ is the heat imparted to the liquid in the still, and W 2 the heat imparted to the anhydrous ammonia in the refrigerator, and W 3 the heat equivalent of the work of ammonia pump, we find Hj. being the heat withdrawn from the anhydrous ammonia in the condenser, and H 2 being the heat with- drawn from the working substance in the absorber. THE ABSORPTION SYSTEM. 223 As all the quantities in the above equation (besides TF 4 ) can be readily determined, it enables us to find, if not a simple at least an artless expression for W t (i. e., the heat which must be imparted to the liquid in the still). WORKING CONDITIONS OF SYSTEM. For the purpose of determining the theoretical values of the quantities which determine the efficiency of an absorption machine, we make the following stipulations which, we hold, are such as to be within the theoretical possibility of realization, although practically they have not as yet been fully realized, viz.: That the apparatus is provided with efficient analyzer and rectifier, so that the ammonia when entering the condenser is practically in an anhydrous condition. That the poor liquor when entering the absorber is only 5 warmer than the rich liquor when leaving the absorber. That all the heat of the poor liquor, except that brought into the absorber, is imparted to the rich liquor on its way to the still in the exchanger. That the uncompensated heat transfers from the at- mosphere to the colder portions of the plant, and from the warmer portions of the plant to the atmosphere, are so well guarded against that they may be neglected in this connection. HEAT ADDED IN REFRIGERATION. The above premises being granted, the different items of the above equation are readily expressed. The heat, W 2 , added to the working fluid in the expansion or re- frigerating coils, is theoretically equal to tbe amount of refrigeration which is produced by its evaporation. The refrigeration, r, in B. T. units which may be pro- duced by the vaporization of one pound of anhydrous ammonia in an absorption machine is the same as in a compression machine, and is therefore expressible by the same formula: r = h l (t t i )s units, h being the heat of volatilization of one pound of am- monia at the temperature t x , of the refrigerator; t is the temperature of the liquid anhydrous ammonia, i. e., the temperature of the condenser, and s the specific heat of ammonia. 224 MECHANICAL REFRIGERATION. For the purpose of this calculation the temperature of the outgoing condenser water may be taken for t, but in order to find the maximum theoretical refrigerating effect, the temperature of the incoming condenser water, cr rather, about 5 G added to that, should be taken for t, as the liquid anhydrous ammonia can be cooled to that degree by the condenser water. This also applies to the same calculation for compression system. HEAT INTRODUCED BY PUMP. The heat, TF 3 , imparted to the working medium by the operation of the ammonia pump is equivalent to the work required to lift the rich liquor from the pressure of the absorber to that of the still. It is not a very im- portant quantity in this connection, and may be neglected in approximate calculations. However, it may be de- termined by the formula: for each pound of anhydrous ammonia which is volatil- ized in the expander. In this formula P 2 stands for the number of pounds of rich liquor which must be moved for every pound of ammonia volatilized in the expander; and z and z t being in feet the heights of columns of water corresponding to the pressure in the still and pressure in absorber, respectively. S represents the specific grav- ity of the rich liquor, and 772 the equivalent of the heat unit in foot-pounds. In exact calculations the heat due to friction of pumps should be added. RICH LIQUOR TO BE CIRCULATED. The number of pounds of rich liquor, P 2 , which must pass the ammonia pumps in order that one pound of liquid anhydrous ammonia may be disposable in the ex- pander or refrigerator coils, depends on the concentra- tion or strength of the poor and rich ammonia liquor, and if the percentage strength of the former be a, and that of the latter be c, we find P 10 _ (100-q) 100 _ n (100 c) a (100 a) c (100 c) a c ~ (100-a) THE ABSORPTION SYSTEM. 225 STRENGTH OF AMMONIA LIQUOR. The percentage strength of the rich liquor depends largely on the construction of the absorber. Theoretically it is determined by the temperature at which it leaves the absorber and the pressure in the latter as shown in the tables on solutions of ammonia given by Starr, pages 96 and 97. The lowest possible percentage strength of the poor liquor depends in a similar manner on the temperature and pressure in the still, but is also greatly affected by the constructive detail and operation of this appliance. HEAT REMOVED IN CONDENSER. The amount of heat, H t , which is taken away from the working substance in the condenser, while one pound of vapor is condensed into liquid ammonia, is equal to the latent heat of volatilization of that amount of ammonia at the temperature of the condenser (temperature of out- going condenser water), and may be readily obtained from the table on saturated ammtfnia, page 92. HEAT REMOVED IN ABSORBER. The amount of H 2 which must be withdrawn from the working liquid in the absorber is composed of differ- ent parts, viz.: The heat developed by the absorption of one pound of ammonia in the poor liquor, H n . The heat brought into the absorber by a correspond- ing quantity of poor liquor, H g . The negative heat brought into the absorber by one pound of the refrigerated ammonia vapor, H v . Hence we find H = H n + H Hv units. - HEAT OF ABSORPTION. The heat developed by the absorption of ammonia vapor in the poor liquor may be obtained after the form- ula given, pages 99 and 100, viz. : ) units. In this formula n stands for the number of pounds of water contained in the poor liquor for each pound of ammonia, and 1 -+- b stands for the number of pounds oi ammonia contained in the rich liquor for every n pound 226 MECHANICAL REFRIGERATION. of ammonia. Under these suppositions Q 3 stands for the number of heat units developed by the absorption of b pounds ammonia vapor, or the heat developed by one pound is rr The last two formulae may be united, to give a sim- pler expression for the amount of heat developed when one pound of ammonia is dissolved in a sufficient quan- tity of poor liquor, containing one pound of ammonia to n pounds of water, in order to obtain a rich liquor which will contain b ~f- 1 pound of ammonia for each n pound of water. The formula then reads n = 925 - 284 + 142 " units. The amount of heat developed by the absorption of one pound of ammonia in some cases of different strength of poor and rich liquor, calculated after the foregoing formula, is given in the subjoined table, together with the number of pounds of rich liquor that must be moved for each pound of ammonia evaporated in the refrig- erator. Ammonia in poor liquor, per cent. Ammonia in rich liquor, per cent. Heat of absorp- tion by one pound of am- monia in units. Pounds of rich liquor for each pound of active ammonia. a c Hn P2 10 25 812 6.0 10 36 828 3.45 12 35.5 828 3.74 14 25 854 7.8 15 35 811 4.25 17 28.75 840 7.0 20 25 840 16.0 30 33 819 6.1 20 40 , 795 4.0 HEAT INTRODUCED BY POOR LIQUOR. The number of pounds of poor liquor which enters the absorber for each pound of active ammonia vapor is equal to the rich liquor less one, this being the amount or weight of ammonia withdrawn, and therefore the heat, Hg, which enters the absorber with that amount of poor liquor, when its temperature is 5 above that of rich liquor leaving the absorber, is He = (P 2 1) 5 X S units, S being the specific heat of the poor liquor, which may be taken at 1. THE ABSORPTION SYSTEM. 227 NEGATIVE HEAT INTRODUCED BY VAPOR. The negative heat, Tv, brought into the absorber with every pound of ammonia vapor is H v = (tt 1 ] 0.5 units, t being the temperature of the strong liquor leaving the absorber, and t t being the temperature in refrigerator coils. HEAT REQUIRED IN GENERATOR. From the above it is evident that the strength of strong and weak liquor, the pressure in still and absorber, and all other quantities, depend in a perfectly constructed plant in the last end on the temperature of cooling water and brine. Accordingly, it would be possible to express the heat required in the still or generator as a function of these temperatures, but the formula required to do this would be so complicated as to be without any prac- tical value, nor would it possess any theoretical signifi- cance. As all the quantities '(excepting WJ of the equation of the absorption cycle can be determined numerically in the manner shown, the quantity, JF^orthe heat required in the generator, can be readily determined after the formula W l = H i +H 2 - W 2 W a WORK DONE BY AMMONIA PUMP. The power, F (in foot-pounds), required to run the ammonia pump is theoretically expressed by the form ilia: foot-pounds, for every pound of active ammonia, *. e., anhydrous am- monia evaporating in refrigerator. (See page 224.) ANHYDROUS AMMONIA REQUIRED. The number of pounds, P 15 of anhydrous ammonia required to circulate to produce a certain refrigerating effect, eay ra tons in twenty-four hours, is m X 284000 PI = - pounds. 228 MECHANICAL REFRIGERATION. HORSE POWER OF AMMONIA PUMP. The power, F t , to run the ammonia pump while pro- ducing a refrigerating effect of m tons in twenty -four hours, is, therefore F l= ' - foot-pounds, and expressed in horse power F 2 , S being taken equal to 1: 33,000 being the equivalent of a horse power in foot- pounds per minute. The formula for F 2 may be simplified to P, x m(z z t ) 0.006, F 2 = 2 r - - -- horse power. This is the horse power required theoretically, to which must be added the friction, clearance and other losses of the pump, as well as of the engine which ope- rates the pump, to find the actual power and the equiva- lent amount of steam required for this purpose. AMOUNT OF CONDENSING WATER. The water required in the condenser expressed in gallons, 6r, for a refrigerating capacity of m tons in twenty-four hours is /i. X m X 284000 G = 8.33Xr(t- tl ) gallOP8 or approximately per minute in gallons, G^ in which formula h^ is the latent heat of volatilization of ammonia at the temperature of the outgoing con- denser water, i, and t the temperature of the incoming condenser water; r is the refrigerating effect of one pound of ammonia. WATER REQUIRED IN ABSORBER. The amount of heat to be removed in absorber for each pound of ammonia vaporized in refrigerator being H 2J as found in the foregoing, the amount of water re- THE ABSORPTION SYSTEM. 229 quired iii absorber for a refrigerating capacity of m tons in twenty-four hours, expressed in gallons, G z , is H 2 XmX 284000 or expressed per minute in gallons, G 9 G _H 2 X m X 24 ECONOMIZING WATER. When water is scarce or expensive, the same water after it has been used in condenser is used in the absorber, which, of course, raises the temperature of the ingoing and outgoing absorber water correspondingly. The water may also be economized by using open air con- densers or by re- cooling the same by gradation, etc. ECONOMIZING STEAM. As the poor liquor is less in volume and weight than the rich liquor, it cannot possibly heat the latter to the temperature of still, other reasons notwithstanding. For this reason the waste steam of the ammonia pump may be used to still further heat the rich liquor on its way to the generator after it has left the exchanger. This is done in the heater, and the heat so imparted to the work- ing fluid should be deducted from the heat to be fur- nished to the generator direct in theoretical estimates. The condensed steam from generator may be returned to boiler if it is not used for ice making. AMOUNT OF STEAM REQUIRED. The theoretical amount of steam required in gener- ator expressed in pounds P 6 per hour for a refrigerating capacity of m tons in twenty-four hours is approximately found after the formula p = W t X m X 284000 24 X r X h a h e being the latent heat of steam at the pressure of the boiler, or, closer still, at the temperature of the generator. As stated in the beginning, these calculations are based on ideal conditions, which are never met with in practical working, and therefore the quantities found must be modified accordingly, and the theoretical amount of steam as found must be increased by from 20 to 40 per cent, and even more, to arrive at the facts in most practical cases. 230 MECHANICAL REFRIGERATION. The amount of steam used by the ammonia pump must be added to the above. It is generally about to of the steam used in the generator. ACTUAL AND THEORETICAL CAPACITY. In order to compare the actual refrigerating capacity of an absorption plant with the theoretical capacity, the amount of steam used in the still, as well as the amount of rich liquor circulated by the ammonia pump, may be taken as a basis. The first case is practically disposed of in the foregoing. In the latter case the amount of liquid moved by the ammonia pump is equal to its capacity per minute, which is found by calculation, as in the case of a compressor, and reduced to pounds per minute. If this quantity is called C, and if P 2 is the number of pounds of rich liquor which must be circulated for each pound of active anhydrous ammonia, as found from the strength of the poor and rich liquor (see foregoing table), the refrig- erating capacity of the machine, It, should be R= units per mirute. "2 The theoretical and actual heat balances can also be compared by determining the heat removed in the con denser and absorber, as well as the heat brought into t h refrigerator and to the generator by actual measurement. SIMPLER EXPRESSION FOR W t . If we neglect the work of the liquor pump and assume that the poor liquor arrives at the absorber ao the absorber temperature, we can express the amount of heat Wi, theoretically required in the generator for each pound of anhydrous ammonia circulated by the formula W t = flu (/i 2 h) units, h 2 being the latent heat of volatilization of ammonia at the temperature of the absorber, and /i, the latent heat of volatilization of ammonia at the temperature of the condenser. It is frequently argued that an equivalent of the whole heat of absorption must be furnished to the gen- erator, but this is only the case (theoretically speaking) when the temperature of the absorber is equal to that of the condenser. THE ABSORPTION SYSTEM. 231 EXPRESSION FOR EFFICIENCY. The maximum theoretical efficiency E, of an absorp- tion machine may be expressed in accordance wfth the above. and if we include the work of the ammonia pumps, etc., we have also COMPARABLE EFFICIENCY OF COMPRESSOR. Ill order to compare the maximum theoretical effi- ciency of an absorption plant with that of a compression plant the foregoing formula: may be used, when in the case of compression W t stands for the amount of heat theoretically necessary to produce the work required from the engine for the circulation of one pound of ammonia. If the absolute temperature of steam entering the engine is T, and that of the steam leaving the engine is T, , and if the work of the engine which operates the com- pressor is expressed by Q t (in heat units), we find for lV t the expression w Q * T W iT=Ti If we omit friction of compressor and engine and in- sert for Q t the theoretical work of the compressor (page 111) we find T and r l being the absolute temperatures of condenser and refrigeration respectively. It is then and for the maximum theoretical efficiency of the com- pression machine, leaving out friction, etc., we find 232 MECHANICAL REFRIGERATION. CONSTRUCTION OF MACHINE. The construction details of the absorption plants vary so much that in this place we can only give the general outlines touching the appliances and contriv- ances which by a concert of action make up the refrig- erating effect. The dimensions of parts vary also very greatly, and those given in the following paragraphs and tables are based on data reported from machines in actual operation where not otherwise stated. THE GENERATOR. The generator, retort or still is generally an upright cylinder heated with a steam coil in which the concen- trated or rich liquor is heated. The rich liquor passes in at the top and leaves at the bottom. The retort and dome is made of steel plate, sometimes of cast iron; and this vessel, the same as other parts containing ammonia gas, should be capable of withstanding a liquid pressure of 400 pounds per square inch. SIZE OF GENERATOR. The size of the still or generator depends on the size of the machine, and for a 10-ton machine (actual ice making capacity) is about two to two and one-half feet wide and fifteen to eighteen feet high, and a little over half of this height is generally occupied by the steam coil. An English author gives the following table of di- mensions for generators or stills of absorption machines, but they appear rather small compared with American structures for the same object : Ice Made in Gallons of .880 SIZE OF GENERATOR. 24 Hours. Ammonia. Diameter. Length. 1 27 13. 5 inches. 5 feet 6 inches. 2 54 17.0 6 " 3 80 21.5 6 " 4 108 22.5 6 " 6 6 162 22.5 10 " 6 8 216 25.0 12 " 10 252 26.0 12 " 12 270 28.0 13 " 15 405 29.5 14 " 24 540 35.0 14 " BATTERY GENERATOR. Generators have also been constructed on the battery plan, three or more cylinders being connected to form one generator, the rich liquor passing gradually from the first cylinder to the last, which it leaves as poor liquor. In this manner it is possible to attain a wider THE ABSORPTION SYSTEM. 233 difference between the strength of the rich and poor liquor, it is claimed. COILS IN RETORT. The heating coils in retort or still are placed in the lower part ,of the retort, and consist of one or more spiral coils of pipe placed concentrically. According to Coppet, their connections should be at both the bottom entrance and exit, and should be made right and left handed, the object being to prevent the steam (when rushing down in the coils) from imparting a gyrating motion to the liquor, thus shaking the retort. The coils should be made of purest charcoal iron, free from defects or spots, as the hot ammonia liquor is very apt to pene- trate such bad places and cause leaks. The space in still occupied by steam coil should always contain ammonia liquor, so that the coil is never exposed to the vapors. For this reason a gauge is provided, which shows the height of the liquor in the generator. As a further pre- caution there is placed above the steam coils an in- verted cone, with a large central opening, placed so-that the liquor will be deflected to the center of still, and not fall upon the coils, if ever the liquor should stand below them. A valve is provided at the bottom of the retort to empty same, if necessary, and also one at the poor liquor pipe leading to exchanger. The heating surface of the coil in retort varies considerably, and for a_10-ton ma- chine it covers from eighty to 100 feet. THE ANALYZER. In the upper part of the still the so called analyzer is located. In it the rich liquor is made to pass over numerous shelves or disks into corresponding basins, over which it runs in a trickling shower from one disk through the next basin over the following disk," and so on, until it reaches the top of the boiling liquid in retort. While the rich liquor runs downward over these devices, the vapor from the retort passes them in its upward course and constantly meeting the rich liquid over an extended area, is enriched in ammonia, and deprived of water. Thus the ammonia vapor is rendered almost free of water when it reaches the top of the analyzer. At the same time the temperature of the rich ammonia liquor is increased from about 150 to 170, .at which it reaches the analyzer, to about 200, more or less, when it reaches the body of liquor in the retort. 234 MECHANICAL, REFRIGERATION. The passages in the analyzer must be amply large for the passage of water and ammonia vapor in opposite directions in order to avoid foaming, overloading, etc. The best iron or steel plate must be used in the construc- tion of the analyzer. As also stated elsewhere, galvan- ized iron pipes and zinc surfaces in general must be avoided wherever they come in contact with ammonia. The surface in the analyzer runs from fifty to seventy square feet in a 10-ton machine. THE RECTIFIER. Frequently the vapor on its way from analyzer to condenser passes the so called rectifier, which is a small coil partly surrounded by cooling water, the lower end of which is connected with the condenser coit, but has also a liquid outlet to a separate liquor receiver which receives all watery condensation which may have formed in the rectifier. In this manner the vapors, when they enter the condenser proper, are as nearly anhydrous as they can practically be made. About twenty-five square feet of cooling surface is allowed in the rectifier for a machine 'of ten tons ice making capacity. The liquid separated from the vapor in the rectifier, after passing through a separate cooler, is returned to the ammonia pump, whence it passes back to the generator or still. The following table, giving the heating surfaces of generator coils and surface in analyzer and rectifier for machines of different ;sizes, is also given on English authority, and these figures also fall short of the sizes employed in the United States : Size in Tons of Ice Made in 24 Hours. Surface in Gene- rator Coils. Surface in An- alj'zer Disks. Surface in Rectifier Coil. Tons Square Feet. Square Feet. Square Feet. 2 6 12 15 30 50 16 43 81 160 214 304 14 34 68 133 169 262 4 11 20 40 50 74 THE CONDENSER. The vapor after leaving the still or rectifier enters the condenser which is constructed on the same principles as the condenser in a compression machine. Besides the submerged condenser and the open air or atmospheric condenser (the latter, on account of accessibility, simplic- THE ABSORPTION SYSTEM. 235 ity and cleansability, now most generally adopted) it has also been proposed to use condensers exposed to the at- mosphere alone, thus to save the cooling water. Such condenser requires a considerable surface, at least over eight times that of the submerged condenser, and over five times that of the atmospheric condenser. The ma- terial for condenser coils, as well as for all other coils in the absorption machine, should be the very best iron. Still another form of condenser consists of one pipe wi thin another, in which the water surrounds the out- side pipe and also runs through the internal pipe, while the gas passes through the annular space between the two pipes. This is a very effective form of condenser, but the difficulty of keeping it clean is very great, and it is almost impossible when the water is liable to leave a deposit. For sizes of condenser coils the same subject under compression machines should be referred to, also the subsequent table on general dimensions. LIQUID RECEIVER, ETC. The vapors after having passed the condenser, reach the receiver in a liquid form and thence pass through the expansion valve to the coils in freezing or brine tank. These parts of the plant, their construction and the mode of operating them are quite the same as in case of the com- pression plant. The liquid receiver for an absorption ma- chine should be at least large enough for the storage of sufficient liquid ammonia to bring the poor liquor at the bottom of the retort to between 18 and 20 Reaumur when the machine is in operation. THE ABSORBER. In the absorber the vapor of ammonia, after having done its duty in the freezing tank or expansion coils, meets the poor liquor coming from the generator, and is reab- sorbed by the latter. The absorber should be constructed in such a manner as to allow the ammonia solution as it gets stronger to meet the cooling water flowing in an opposite direction, so that the warmer water cools the weaker solution and the colder water cools the stronger solution. In compliance with this condition the vapors of ammonia should be in constant contact with the liquor, and the surface of contact ought to be of reasonable area. This may be accomplished by passing the ammonia and weak liquor over traps or disks, similar to those 236 MECHANICAL REFRIGERATION. in the analyzer, or through a series of pipes or coils, where they are in constant contact with each other, the pipes being efficiently cooled from the outside by water (spent water from condenser generally), in order to remove the heat of solution of the ammonia as fast as it is formed. Generally the ammonia gas and the poor liquor are mixed together into a manifold at the lower end of the coils. The surface of these pipes exposed to the cooling water in a tank in which they are submerged (atmospheric cooling, as in the case of atmospheric con- densers, may also be used), is variously estimated at 300 to 500 square feet for a machine- of ten tons ice making capacity. THE EXCHANGER. In the exchanger the heat which the poor liquor carries away from the still should be imparted to the rich liquor on its way to the still. Asa matter of course the two liquids should flow in opposite directions, so that the hottest rich liquid meets the poor liquid when it is hottest, and the cold poor liquid meets the rich liquid when it is coldest. The exchanger is also to be made of the best sheet steel, and the coils within should be extra heavy, and the whole apparatus must be able to sustain the same pressure as the retort. It should stand upright, and the liquor pump should force the rich liquor through these coils to the top of the retort or to the heater, and the poor liquor should pass in the opposite direction. In causing the liquors to take this course the pressure in the body of the exchanger can be regulated by the valve on the poor liquor pipe coming from the retort. The amount of surface between the poor and rich liquor in exchanger varies according to its construction, all the way from twenty-five to fifty square feet for a 10- ton plant (ice making capacity). This statement covers those plants of which we have knowledge. According to Starr, who assumes the heat transfer to amount to 40 B. T. units per square foot surface per hour, for each degree Fahrenheit difference in temperature, about 120 square feet of exchanging surface would be required for an ice making plant of ten tons daily capacity. THE HEATER. The heater is another contrivance frequently used to further the objects of the exchanger. It consists of a coil THE ABSORPTION SYSTEM. 237 of pipe through which the rich liquor passes from the exchanger before it reaches the retort. This pipe is located in a drum in which steam (generally spent steam from liquor pump) is circulated. It is constructed on the same principles as the other receptacles and coils. The surface of the heater coil is about thirty to fifty square feet in a 10-ton ice making plant. THE COOLER. The cooler is an arrangement frequently used to do for the poor liquor what the heater does for the rich liquor, I. e., to promote the objects of the exchanger by withdrawing all the heat possible from the poor liquor before it reaches the absorber. This contrivance is built on the same principles as a condenser, and consists of a coil or series of coils, submerged in a tank through which cooling water circulates, or placed over a vat to allow the cooling water to trickle over them, similar to an atmospheric condenser. The surface of the cooler may be from sixty to eighty feet for a 10- ton ice making ma- chine, and larger or smaller for different capacities, as the case may be. THE AMMONIA PUMP. The ammonia pump, which takes up the rich liquor from absorber to force it through the exchanger and heater to the generator, is generally a steam pump, the en- gine and pump cylinder being mounted on a common base. A pump driven by belt may also be used. The size and number of strokes of pump depend on the size of plant, but also largely on the strength of poor and rich liquor. (See table, page 139.) For a 10-ton plant (ice making capacity) the pump has generally a diameter of three inches, the stroke being from six to ten inches and the number of strokes from twenty-five to fifty per minute. The ammonia pump is generally single-acting, in order to relieve the pressure on stuffing box, which latter fixture requires particular care in order to secure proper working of the pump. MISCELLANEOUS ATTACHMENTS. Like the condenser, the refrigerator, expansion coils, as also the brine tank (and brine pump) or the freez- ing tank, are constructed on the same lines in an absorp- tion as in a compression plant, and therefore need no fur- ther mention here. The same may be said of the expan- 238 MECHANICAL REFRIGERATION. sion valve, and of other valves required when desirable to shut off certain portions of the machine, of the required pressure gauges, thermometers and other attachments. In the use of the absorption plant for various purposes the same rules apply as in the use of a compression ma- chine. As the spent steam from the generator is used for distilled water, and as the same cannot be contam- inated with lubricating oil, the steam filter or oil sepa- rator is superfluous it the boiler feed water is of ordinary purity. OVERHAULING PLANT. In order to keep an absorption plant in the best possible order for the longest possible time it is neces- sary that the different parts be opened and overhauled from time to time (according to the water used and as other conditions may indicate) every alternate season or so in order to thoroughly clean and inspect the interior part, and to repair them in order to anticipate any pos- sible breakdowns, etc. In all cases, before starting up to open a new season, the coils and traps should be tested. COMPRESSION VERSUS ABSORPTION. The question is frequently asked as to which kind of refrigerating plant a compression or absorption plant- is the most profitable and the most economical; and many different answers are given to these questions. Dif- ferent as the two kinds of machines look at first sight, the theoretical principles as well as defects are the same, as has been already explained, although the natural facilities, as relative price of coal and cooling water, etc., may be more favorable in certain localities for one class of machines than for another. Taking this into due con- sideration, the principal difference between the two machines in a given case must be sought in the more or less greater care and perfection with which they are built and operated, more particularly also in the quality, quantity and proper distribution of material, the work- manship and the life of the plant, considering also the kind of water and ammonia to be used. When it is considered how difficult it is to give due regard to all these circumstances in the valuation or planning of an individual plant, the apparently conflict- ing results of different kinds of plants working in differ- ent localities and conditions, and the different opinions on them are explained in a great measure. THE ABSORPTION SYSTEM. 239 TABULATED DIMENSIONS, ETC. The great variations in the dimensions of the various parts of absorption machines of different makes find expression in the following table, which purports to give the dimensions, capacity, etc., of different machines. For the correctness of these figures we are unable to vouch, as the manner in which we obtained them does not exclude clerical errors, hence we must submit them for what they are worth: TABLE SHOWING DIMENSIONS, ETC., OF ABSORPTION MACHINES. Actual ice making capacity in tons of ice 3 8 12 15 25 10 Number and size of steam boiler horse power or dimen- sions 15 30 40"x20' 50 J2 42" (2 42" Pounds of coal used per hour 65 140 135 220 | \\.Vz 504 168-1SG Number and size of generators.. . 30"xlO' 30"xl6' 24"xl8' 44"xl4' (2 30" 28"Xl5* Size of coil in gener- ator in square feet Surface of disks, etc., in analyzer in square feet Cooling surface in exchanger in square feet Cooling surface of traps in absorber in 24 10 34 130 48 20 51 260 91 64 22!/ 2 191 96 34 68 470 1 x!7 1 /4' 400 125 65 1900 80 24 25 673 Cooling surface in condenser in square feet 345 690 220 1380 1220 544 Surface in expander or refrigerator in square feet Cooling surface in rectifier in square f get; 410 1200 726 .25 2100 4000 1600 Cooling surface in heater .... 41 Temperature of water in degrees F. Temperature of brine in degrees F. 70 10-20 70 10-20 80 10-12 70 10-20 ' 76 7 80-94 10-14 From the foregoing table it appears that in absorp- tion machine one pound of coal will make from four to seven pounds of ice. On the continent it is assumed that one pound of coal will make about ten pounds of ice in an absorption machine ; the evaporative power of the coal being taken at eight pounds of water per pound of coal. 240 MECHANICAL REFRIGERATION. CHAPTER X. THE CARBONIC ACID MACHINE. GENERAL CONSIDERATIONS. Among the refrigerating machines which use other refrigerating media than ammonia, those compression machines using carbonic acid have found favor for many specific purposes, especially so for the refrigeration of storage rooms in hotels and restaurants', where the im- peccability of the gas to victuals is prominently valued. The non-corroding action of carbonic acid on any of the metals, and the fact that it cannot be decomposed dur- ing compression, etc., speak principally in favor of its use. The fact that a leak of carbonic acid is not demon- strated by its smell might be overcome by the addition of some odoriferous substance. The capacity of the compressor may be very small as compared with other refrigerating plants (see page 89), but the parts of the machine must also be made correspondingly stronger on account of the high pressure of the gas. The cheapness of liquefied carbonic acid is also quoted in its favor as a refrigerating agent, as also its lesser dan- ger to respiration in case of leaks. It is claimed that air containing 8 per cent of carbonic acid gas can be inhaled without danger, while an atmosphere containing only ^ per cent of ammonia is said to be decidedly dangerous. On the other hand, the presence of the least amount of ammonia in the air .demonstrates itself by the smell, while this is not the case with carbonic acid. Not only the neutrality of carbonic acid toward metals and packings, but also toward water, meat, beer and other products subjected to cold storage, should be mentioned in. this connection. The use of carbonic acid in refrigerating machines of the compression type has been somewhat stimulated by the cheap manufacture of liquid carbonic acid as a by-product of the brewing industry, especially in Ger- many, where over 400 such machines (1894) are said to be working satisfactorily. PROPERTIES OF CARBONIC ACID. The carbonic acid, which is a gas of 1.529 specific gravity (air = 1) at the atmospheric pressure, becomes liquid at a temperature of 124 F. at that pressure. At 32 F. it is liquid under a pressure of 36 atmospheres, and then has a specific weight of 0.93 (water = 1). The specific weight of the liquid at different temperatures, according THE CARBONIC ACID MACHINE. 241 to Mitchel, is at 32 F. = 0.93, at 42 F. = 0.8825, at 47.3 F.,= 0.853, at 65.3 F.= 0.7385, and at 86 F.=0.60. The specific heat of carbonic acid gas by weight = 0.2167 (air = 0.2375). Of the liquid it is 1 . The author's attention has been called to the appar- ent inconsistency existing between the specific gravity of liquid carbonic acid, as given in the foregoing para- graph (0.6 at 86 F.), and the amount of carbonic acid contained in the cylinders in which the same is shipped. The cylinders have a capacity of 805 cubic inches (29.11 .pounds of water) and are made to contain 20 pounds of liquid carbonic acid, and some manufacturers are said to crowd in 21 and 22 pounds, although this is doubtless a very risky proceeding. But even at 20 pounds the cyl- inders contain over 2% pounds more (at 86 F.) than what is consistent with the above specific gravity. The fact that the drums do not burst with such a charge tends to show that the foregoing specific gravity is not correct (too low) or that different densities exist for different pressures at or near the temperatures charac- terizing the critical condition of carbonic acid (88 F.). PROPERTIES OF SATURATED CARBONIC ACID GAS. Transformed to English units from a metric table computed by Prof. Schroter, by Denton and Jacobus. Tem- pera- ture of ebulli- tion in deg. F. Abso- lute press- ure in Ibs. per sq. in. Total heat reck'n'd from 32 Fahr. Heat of liquid reck'n'd from 32 Fahr. Latent heat of evapo- ration. Heat equiv- alent of ex- ternal work. . Incr'se of vol- ume during evapo- ration. Dens'y of va- por or weight of one cu. ft. t P-M44 y - r APw u 22 210 98.35 37.80 136.15 16.20 .4138 2.321 13 249 99.14 -32.51 131.65 16.04 .3459 2.759 4 292 99.88 26.91 126.79 15.80 v.2901 3.265 5 342 100.58 20.92 121.60 15.50 2438 3.853 14 396 101.21 -14.49 115.70 15.08 .2042 4.535 23 457 101.81 7.56 109.37 14.58 .1711 5.331 32 525 102.35 0.00 102.35 13.93 .1426 6.265 41 599 102.84 8.32 94.52 13.14 .1177 7.374 50 680 103.24 17.60 85.64 12.15 .0960 8.708 59 768 103.59 28.22 75.37 10.91 .0763 10.356 68 864 103.84 40.86 62.98 9.29 .0577 12.480 77 968 103.95 57.06 46.89 7.06 .0391 15.475 86 1,080 103.72 84.44 19.28 2.95 .0147 21.519 A, in the column heading, stands for the reciprocal of the mech- anical equivalent of heat. The preceding table, showing the properties of satur- ated carbonic acid, may be used in connection with the formulae given in the chapter on the ammonia compres- 242 MECHANICAL REFRIGERATION. sion system. However, the results obtained in this man- ner are only approximations, since the carbonic acid is in a superheated condition during several stages of the cycle constituting the refrigerating process, as a reference to the practical data, given hereafter, will amply show. CONSTRUCTION OF PLANT. The refrigerating plants operated with carbonic acid are built on the same general plan as the ammonia com- pression plants, compressor, condenser and refrigerator being the identical important parts, specified as follows by a leading manufacturer: THE COMPRESSOR. The compressor is either of the horizontal or the ver- tical type (for smaller machines generally the latter). It should be made of the best material, steel or semi-steel, and it is provided with a jacket through which the return gas passes, which arrangement gives additional strength to the cylinder and tends to keep it cool. The piston rods, connecting rods, crank pins and valves should be made of forged steel, and so as to be interchangeable at any time. STUFFING BOX. The stuffing box is made gas tight by means of cupped leathers on the compressor rod. Glycerine is forced into the spaces between these leathers at a pressure superior to the suction pressure in the compressor, so that what- ever leakage takes place at the stuffing box is a leakage) of glycerine either into the compressor or out into the atmosphere, and not a leakage of gas. What little leakage of glycerine takes place into the compressor is advantageous, inasmuch as it in the firsl) place lubricates the compressor, and in the second place fills up all clearances, thereby increasing the efficiency of the compressor. In order to replace the glycerine which leaks out of the stuffing box of the horizontal machine, there is a belt driven pump which operates continuously. The smaller machines are fitted with a hand pump, a few strokes of which are required to be made every four or five hours. GLYCERINE TRAP. Any glycerine which passes into the compressor be- yond what is necessary to fill the clearance spaces is dis- charged with the gas through the delivery valves. In order to prevent this going into the system, all the liquid THE CARBONIC ACID MACHINE. 243 passes through a trap in which the glycerine drains to the bottom, whence it is drawn off from time to time. It may be remarked here that the glycerine has no affinity for carbonic anhydride, hence it undergoes no change in the machine, and therefore there is no chance of the condenser coils becoming clogged. CONDENSER. The condenser consists of coils of wrought iron extra heavy pipes, which are either placed in a tank and sur- rounded by water, or are so arranged that water trickles over them, forming the well known atmospheric con- denser. The coils are welded together into such length as to avoid any joints inside the tank, where they would be inaccessible. In connection with the condensers, where sea water only is available for condensing purposes, one very im- portant advantage of carbonic anhydride machines is claimed: As carbonic anhydride has no chemical action on copper, this metal is used in the construction of the eoils, giving same longer life. EVAPORATOR. The evaporator consists of coils of wrought iron extra heavy pipe, welded into long lengths, inside which the carbonic anhydride evaporates. The heat required for evaporation is usually obtained either from brine sur- rounding the pipes, as in cases where brine is used as the cooling medium, or else from air surrounding the pipes, as in cases where air is required to be cooled direct. Between the condenser and evaporator there is a regulating or so called expansion valve for adjusting the quantity of the liquid carbonic anhydride passing from the condenser. SAFETY VALVE. In order to enable the compressor to be opened up for examination of valves and piston without loss of carbonic anhydride, it is necessary to fit a stop valve on the suction and delivery sides so as to confine the carbonic anhydride to the condenser and evaporator. It is, of course, pos- sible for a careless attendant to start the machine again without opening the delivery valve, and in such cases an excessive pressure would be created in the delivery pipe, from which there would be no outlet. To provide against this danger a safety device is adopted, consisting of a housing, at the base of which is a thin disk, which is 244 MECHANICAL REFRIGERATION. designed to blow off at a pressure considerably below that to which the machines are tested. JOINTS. All joints should be made with special flange unions and brass bushings. They should be made absolutely tight with packing rings of vulcanized fiber, which with- stand the heat and still have the necessary elasticity to insure the joint being perfectly tight when either hot or cold. STRENGTH AND SAFETY. The working pressure varies from about fifty to seventy atmospheres. Owing to the very small diameter of all parts, even in large machines, there is no difficulty in securing a very ample margin of strength. All parts of the machine subject to the pressure of the carbonic anhydride should be tested at three times the working pressure. APPLICATION OF MACHINE. Both the direct expansion and the brine system are used in connection with a carbonic acid refrigerating machine, but for most purposes the former is deemed preferable, as is also the case with ammonia compression. For ice making the can or plate system may be used, and also for other refrigerating purposes the application of the carbonic acid refrigerating plant is quite similar to that of any other compression or absorption plant. A plant quite similar, or rather identical in its main feature with a carbonic acid refrigerating plant is also used for the manufacture of liquefied carbonic acid, as it may be obtained from breweries, distilleries, calcination of lime and other sources. EFFICIENCY OF SYSTEM. The efficiency of the carbonic acid machine is some- what lessened by the high specific heat of the liquid, and therefore "decreases with greater divergence of tem- perature. It has been proposed to reduce this loss in efficiency by introducing a motor between the condenser and refrigerator, which would perfect the cycle of opera- tions. After another method, the loss of efficiency due to the specific heat of liquid is reduced by allowing the liquid during its flow to expand from the condenser pressure to an intermediate pressure, and to return the vapors so produced after having cooled the remaining liquid to the condenser by an auxiliary compressor. THE CARBONIC ACID MACHINE. 245 It has frequently been argued that carbonic acid compression machines could not be operated successfully when the temperature of the condenser water exceeds 88 F., the critical temperature of carbonic acid. Accord- ing to the present conception of the critical condition, above the said temperature carbonic acid can only exist in the gaseous form, and cannot be converted into a liquid by means of the withdrawal of the latent heat of volatilization. This being the case, the refriger- ating effect of a carbonic acid machine working with condenser water above 88 F. would only be that of a compressed gas while, expanding against resistance, which would be comparatively small when compared with refrigerating effect produced by the volatilization of the liquefied medium. These considerations and argu- ments are, however, in direct conflict with the statements of Windhausen, according to which carbonic acid ma- chines operated with condensing water of 90 to 94 F. and in tropical countries produce refrigerating effects ten times larger than what they would be if the carbonic acid acted simply as a compressed gas at such tempera- tures. Experiments cited by Linde show that a carbonic acid machine working with a temperature of 92 F. at the expansion valve gives a refrigerating effect about 50 per cent less than when the temperature at the expan- sion valve was 53 F. CAUSE OF APPARENT INCONSISTENCIES. The foregoing and other apparent inconsistencies be- tween the theory and practice of the working of the car- bonic acid refrigerating plant have recently been fully ex- plained on the basis that the carbonic acid is in the state of a superheated gas in the compression stage; in fact, it must be so if the condensing gas reaches a tempera- ture over 80, in order to produce refrigerating effects at all. The loss due to the absence of an expansion cylinder (completing a perfect reversible cycle) to reduce the tem- perature of the liquefied carbonic anhydride from the temperature of the condenser to that of the refrigerator, which constitutes the chief difference in the economy between ammonia and carbonic acid refrigerating ma- chines, has also been somewhat overestimated in dero- gation of the carbonic acid machine as shown by Mollier 246 MECHANICAL REFRIGERATION. COMPARISONS OF EFFICIENCY. The calculation on the former basis (specific heat times weight of carbonic acid circulated is unit of time) gave this loss as about 0.80 per cent of the whole theoretical refrigerating effect for every degree difference between the temperature of the condenser and that of the refrig- erator, as compared with 0.18 per cent loss in the case of ammonia. The accompanying table was calculated and published by Ewing several months ago, showing the relation between the ammonia and carbonic acid refrig- erating plant with reference to the loss due to cooling of the liquid. In this table the upper limit of temperature in the condenser, or rather immediately before the ex- pansion valve, is taken at 68 F., while the temperature in the refrigerator varies from 50 to 4 F. THEORETICAL CO-EFFICIENT OF PERFORMANCE IN VA- POR COMPRESSION MACHINES, UNDER WET COMPRES- SION, UPPER LIMIT OF TEMPERATURE BEING 68 F. Lower Limit of Temperature, Deg. F. Theoretical Co-efficient of Performance. Co-efficient of Performance in Carnot Cycle. Ammonia. Carbonic Acid. 50 40 32 23 14 4 27.8 18.1 13.2 10.2 8.3 6.9 25.7 20. 11.4 8.5 6.8 4.5 28.3 18.5 13.6 10.7 8.8 6.3 It will be noticed that with ammonia the theoretical performance namely, that of a compression machine without an expansion cylinder is only a little less than the ideal performance which would be obtained by fol- lowing Carnot's cycle. Hence with this substance al- most nothing would be gained by adding an expansion cylinder to the machine nothing, certainly, that would in any way compensate for the increase of complexity and friction and cost which an expansion cylinder would involve. With carbonic acid there is considerably more falling away from the ideal of Carnot, for the reason that the specific neat of the liquid bears a greater proportion to the latent heat of the vapor. But even then the saving in work which an expansion cylinder would bring about is not great, and in practice the expansion cylinder, even in carbonic acid machines, is never used so far. THE CARBONIC ACID MACHINE. 247 PRACTICAL COMPARATIVE TESTS. Quite a number of practical tests published by Linde several years ago led him to the compilation of the fol- lowing table, which shows the excess of efficiency in per cents of ammonia refrigerating machine over and above that of a carbonic acid machine, both working -at differ- ent temperatures before the expansion valve, the temper- ature in the brine surrounding expansion coil being the same (about 23 F.) in all cases. Temperature before expan- sion valve P 54 63 12 81 90 Excess of efficiency of am- monia plant 17% 23 % 31% 47% 101$ The tests referred to by Linde, on which the fore- going table is based, were made in the Experimental Refrigerating Station in Munich, Germany, by Schroeter, and in the following little table are compiled some of the actual results of these experiments obtained in the ca'se of an ammonia and of a carbonic acid refrigerating ma- chine: AMMONIA MACHINE. CARBONIC ACID MACHINE. No. OF TEST. 1 2 3 4 5 6 7 8 Temp, in brine tank, degrees Celsius. .. 6.1 6.4 6.4 4.8 4. 4.8 4.8 -6.T Temp, in condenser, degrees Celsius . . . 21.4 21.4 21.4 34.9 20.9 21.2 22.2 30 Temp, before expan- sion valve, degrees Celsius 6.5 11.6 18.4 28.3 -7.9 10 16.8 28.8 Refrigeration per hour per horse power of steam en gine in calories . . . 3,897 3,636 31508 2,237 3,832 3,178 2,867 1,477 The correctness of these figures has never been doubted, and in view of these facts the efficiency of a carbonic acid machine now in the market, which is given at 4,300 and 3,700 calories for temperatures of 10 and 20 Celsius before the expansion valve per indicated horse power, must be considered as something phenomenal indeed. This machine has no expansion cylinder, and therefore its efficiency is comparable to the efficiencies given under tests 6 and 7 in the above table, which are nearly 25 per cent less. 243 MECHANICAL REFRIGERATION. CH APTER.XI.-OTHER COMPRESSION SYSTEMS. AVAILABLE REFRIGERATING FLUIDS. Besides ammonia other liquids are used, and still others have been proposed as working fluids in refriger- ating machines. Most of these liquids are used on the same plan as ammonia in the compression system, and the machines, barring certain details, are constructed on the same principles as the ammonia compression ma- chine, and the same rules and calculations apply to all of them. The following table shows the pressure and boiling point of some liquids available for use in refriger- ating machines as given by Ledoux. (Denton and Jacobus' edition.) IB Tension of Vapor, in pounds per square inch, above Zero. Deg. Fahr. Sul- phuric ether. Sul- phur di- oxide. Am- monia Methy- lic ether. Car- bonic acid. Pictet fluid. (1) (2) (3) (4) (5) (6) (7) 40 10.22 31 13 23 22 5 56 16 95 11 15 13 7 23 21.51 13.85 251.6 4 1.30 9.27 27.04 17.06 292.9 13.5 5 1.70 11.76 33.67 20.84 340.1 16.2 14 2.19 14.75 41.58 25.27 393.4 19.3 23 2.79 18.31 50.91 30.41 453.4 22.9 32 3.65 22.53 61.85 315.34 520.4 26.9 41 4.45 27.48 74.55' 43.13 694.8 31.2 50 5.54 33.26 89.21 50.84 676.9 36.2 69 6.84 39.93 105.99 59.56 766.9 41.7 68 8.38 47,62 125.08 69.35 864.9 48.1 77 10.19 56.39 146.64 80.28 971.1 55.6 86 12.31 66.37 170.83 92.41 1,085.6 64.1 95 14.76 77.64 197. ^3 1,207.9 73.2 104 17.59 90.32 227.76 1,338.2 82.9 MACHINES IN ACTUAL OPERATION. Of those compression machines which are in actual uste besides the ammonia and carbonic acid machine, which have been described already, those operated with sulphur dioxide, Pictet liquid, ethylic ether (sulphuric ether), ethyl chloride and methyl chloride may be men- tioned especially. The latter machine is comparatively new, and not so far in practical use to any extent, and therefore no special account can be given of the same in the following short remarks. OTHER COMPRESSION SYSTEMS. 249 Recently we have found some accounts given of a machine operated with chloride of methyl in an ice fac- tory at Algiers. We are informed that the size of the engine is 30 horse power, that about eighty pounds of the chemical at about fifty cents per pound were needed to operate the plant during 5,000 hours without the least disturbance, and we are informed of a number of other details, but as to the actual amount of ice produced we are left in the dark entirely. The temperature of the brine is 4 F. The pressure in the expander appears to be very low THE ETHYL CHLORIDE MACHINE. A refrigerating machine using ethyl chloride as a refrigerant has been in use to some extent lately, "the ethyl chloride evaporates at a quite high temperature; the machine works under a vacuum, and condensing pressures are very low, about fifteen pounds (gauge pressure) as a maximum. The refrigerating coils are made of sheet copper, flat, several inches broad, and about an inch thick in an experimental plant in opera- tion in Chicago. The machine appears to be designed for small work only, fruit rooms, creameries, small butcher shops, etc., and is operated by any sort of a small motor. REFRIGERATION BY SULPHUR DIOXIDE. The sulphurous acid refrigerating machines are also in practical operation to some extent. They require, how- ever, a much greater compressor capacity than the am- monia compressors (nearly three times as much), and give a low efficiency at very low refrigerator temperatures. PROPERTIES OF SULPHURIC DIOXIDE. The specific heat of liquid sulphurous acid is 0.41; the critical pressure 79 atmospheres, and the critical temperature 312 F. The specific gravity of the gaseous acid is 2.211 (air = 1), and the specific gravity of the liquid at- 4 F = 1.491. The relation of the specific gravity, s, of the liquid to the temperature, i, is expressed by the following for- mula given by Andreef: 8=1.4333 0,00277 t 0.000000 271 1* The specific heat of liquid sulphurous acid is 0.41 ( water 1). 250 MECHANICAL REFRIGERATION. LEDOUX'S TABLE FOR SATURATED SULPHUR DIOXIDE GAS *>a* a 73 6viS jtt A M 03^ 3r-&; 3" o? ^pp l 3^1 ^l O U Si* ^ go, * a 'o . it 43 > . w * IfSg- >>-SP cx S'fl CCx] a fl ^ o " o3 Q) O ^2 eg. 5^.2 "t^ fl ^ 2"o 5Jt3 ^2 cd Q 0)^3 ^ OH H S QpH 5ri Q}^ ^O H 13 75.2 2.5 23.0 17.5 23.9 a % 80.6 15.9 16.6 10.1 39.2 b s L 1 72.3 26.6 50.4 40.6 19.4 S 2 70.5 14.3 37.6 30.0 20.2 ti t- 3 .<"! 3 69.2 0.5 29.4 22.0 25.2 O O g.co >* 68.5 11.8 22.8 16.1 29.4 2 24 84.2 15.0 27.4 24.2 11.7 ^ 1 26 82.7 3.2 21.6 17.5 19.0 1 M 25 84.6 10.8 18.8 14.5 22.9 *Friction taken at figures observed in the tests which range from 14 to 20 per cent of the work of the steam cylinder. OTHER COMPRESSION SYSTEMS. 251 For a comparison of the sulphur dioxide and the ammonia compression plants the foregoing table, ab- stracted from Schroeter and Denton's tests, may be cor ^ulted. ETHER MACHINES. Compression machines, with sulphuric ether as the working fluid, were in great favor in former days, but have been abandoned to a great extent, owing, probably, to the enormous size of compressor required, it being re- quired to be about seventeen times as large as an am- monia compressor of the same capacity . The great in- flammability of the ether is another objection. The for- mula and rules given for the ammonia compressor apply also for ether, with the exception that the specific heat of the saturated vapor of ether (unlike that of ammonia, steam, carbonic acid and sulphur dioxide), is positive, and therefore superheats during expansion and condenses during compression. An ether machine, therefore, needs no protection against superheating, and is always oper- ated with dry vapor. Specific heat of liquid, 0.51. TABLE SHOWING PROPERTIES OF SATURATED VAPOR OF ETHER. 2 .2 ss t* o ''" H o ^ |i . ID'S "^ ' 12 0) > '5^"c3-^ ^ . a?L ! CT W V] 5!s| ^oo oS 03 B So si rt) |S M i 3 1 -p. 2 gs Sa-^ * * y> 1 s|| fe EH ^ K H pq n:^ i" CQ jj B. T. B. T. B. T. B. T. B. T. Units. Units. Units. Units. U nits. 32 3.54 0.00 376 00 376.00 345.80 30.20 1.278 .048 50 5.51 21.28 393.76 372. 4H 341.48 31.00 0.844 .073 68 8.31 42.80 411.12 36.^.32 336.52 31. 8t) 0-574 .107 86 12.20 64.56 428.00 3H3.44 330.88 32.S6 0.401 .154 104 17. 4H 86.42 444.44 357.92 324.60 33.32 0.287 .232 122 24.32 88.76 460.44 351.68 317 64 34.04 0.210 .294 140 33 17 131.20 476.00 344.80 310.12 34.68 0.158 .392 158 44.32 153.92 491.12 337.20 301.96 35.24 0.120 .515 176 58.13 176 84 505.76 328.92 293.28 35.64 0.093 .705 194 74.96 200.00 520.00 320.00 284 12 35.68 0.073 .848 212 95.25 223 44 532.76 310.32 274.48 35.84 0.057 1.074 230 119.51 247,08 547.12 300.04 264.62 35.32 0.005 1.350 248 148.44 270.96 5CO 00 289.04 254.28 34.76 0.036 1.703 EFFICIENCY OF ETHER MACHINES. The following data relating to the working of an ether machine are not the result of a careful test, but repre- sent practical working, it is claimed: 252 MECHANICAL REFRIGERATION. For a production of fifteen tons of ice in twenty-four hours 245,000 B. T. units were abstracted per hour, and the indicated horse power of the engine was eighty-three, of which forty-six indicated horse power was used for the ether compressor and the balance for friction in compressor, pumping water, working cranes, etc. The temperature of the cooling water entering the condenser was 52 F. in this case. REFRIGERATION BY PICTET'S LIQUID. This liquid, which is also used in compression ma- chines, is a mixture of carbonic acid and sulphurous acid, Which, according to Pictet,who introduced the same, cor- responds to the formula CO 4 S. According to Pictet, the pressure of this mixture or compound at higher tempera- ture is less than the law of pressure relating to ordinary mixtures would indicate. The following table shows the relations of pressures and temperatures of this substance: Pressure Pressure Temperature, Degrees F. (Absolute) in Atmospheres. Temperature, Degrees F. (Absolute) in Atmospheres. -22 0.77 50 2.55 13 0.89 59 2.98 4 0.98 68 3.40 2.2 .00 77 3.92 5 .18 86 4.45 14 .34 95 5.05 23 .60 104 5.72 32 .83 113 6.30 41 2.20 122 6.86 If the Pictet liquid were an ordinary mixture its pressure would gradually rise from 0.77 to 13.98 atmos- pheres from the temperature 22 to -fll2 degrees Fahren- heit. Instead of that the pressure increases from 0.77 to 6.86 atmospheres only, and at 77 F. is less than that of the sulphurous " acid " or sulphur dioxide alone. ANOMALOUS BEHAVIOR OF PICTET'S LIQUID. It is claimed that a compression plant, if operated with Pictet's liquid, will produce a greater effect than what is compatible with the familiar thermodynamic formula given on page 71 of this compend. This anoma- lous behavior is sought to be explained by the physical or chemical work done by the liquids while combining into one substance in the condenser, which work it is argued replaces part of the work which would have to be done if OTHER COMPRESSION SYSTEMS. 253 a simple working fluid were used. If this explanation were correct we would have to assume that while a cer- tain amount of work (i. e. heat) is given off in the con- denser, an equivalent amount of heat must be absorbed in the refrigerator, thus increasing the efficiency of the machine in two directions, a most happy coincidence, but one which is in no wise corroborated by the second law of thermodynamics. OTHER EXPLANATIONS FOR THE ANOMALY. In accordance with thermo-chemical tenets, the combination of carbonic and sulphuric dioxide should ab- sorb heat while being formed in the condenser, and should generate heat while being decomposed in the re- frigerator. Such a behavior would bring the working of a machine with Pictet's liquid within the scope of the second law, but it would hardly account for the alleged anomalous efficiency of such a machine. Generally it is supposed that the influence of heat on chemical combinations is such that they become less permanent with increase of temperature, and that at a very high temperature they are dissolved in their elements. This is quite correct for such combinations which are formed by the development of heat, and which absorb heat while being decomposed. But the contrary takes place in the case of combinations which are formed under absorption of heat. These latter com- binations become more permanent with the increase of temperature. BLUEMCKE ON PICTET'S LIQUID. According to experiments made by Bluemcke the pressure of Pictet's liquid is always higher than that of sulphurous acid at all temperatures. Furthermore he claims that the commercial " Pictet's liquid " is not compounded after the formula CO 4 IS, but that it contains only 3 percent of CO Z by volume. The mixture CO, 6 S 7 , for which Pictet has established 76? as the boiling point has a tension of four atmospheres at a temperature of 17 C C. Such conflicting statements as these are hardly calculated to remove the doubts connected with the use of Pictet's liquid, and more authentic experi- ments by disinterested parties and with liquids of well known composition will be required to definitely settle this matter. 254 MECHANICAL REFRIGERATION. MOTAY AND ROSSI'S SYSTEM. Previous to Pictet's invention Motay and Rossi had operated a refrigerating machine on a similar plan with a compound of two liquids, one of which liquefies at a comparatively low pressure and then takes the other in solution by absorption. Their mixture consisted of or- dinary ether and sulphur dioxide and has been termed ethylo-sulphurous dioxide. It is stated that the liquid ether absorbs 300 times its volume of sulphur dioxide at ordinary temperature and at 60 F. the tension of the vapor of the mixture is below that of the atmosphere. The compressing pump has less capacity than would be required for ether alone, but more than for pure sulphur dioxide. Before exact formulae can be given for the dimen- sions and efficiency of machines working with compound liquids their chemical and physical, and especially their thermo-chemical behavior, must be more definitely settled by experiments. CRYOGENE REFRIGERATING AGENTS. Cryogene is another name for refrigerating medium, and literally translated means ice generator. Certain hydrocarbons, naphtha, gasoline, rhigoline or chimo- gene have also been recommended and used to some ex- tent as refrigerating media. These liquids are used in much the same way as ether, in common with which they have a great inflammability; but they are much cheaper to start with. Van der Weyde's refrigerating machine consists of an air pump and a force pump, a condenser and two refrigerator coils, one of which also serves as a reservoir for the condensed liquid. The water to be frozen is placed in molds which are surrounded by a glycerine bath. The glycerine bath in turn is surrounded on the outside by the refrigerating medium, 15 naphtha, gasoline, chimogene, etc., which is evaporated by means of the air pump, thereby abstract- ing sufficient heat to cause the formation of ice. ACETYLENE. Acetylene, which has lately been so prominently mentioned as the illuminating agent of the future, has also been talked of as a refrigerating agent. It is a com- bination of hydrogen and oxygen after the formula C 2 H 2 . It is highly inflammable and said to require a pressure of 48 atmospheres to be liquefied at freezing point of water. AIR AND VACUUM MACHINES. 255 CHAPTER XII. AIR AND VACUUM MACHINES. COMPRESSED AIR MACHINE. Air is used in various ways as a working fluid in re- frigerating plants, but on the whole to a limited extent only. The compressed air machine is based on the utiliza- tion of the reduction of temperature which takes place when compressed air expands while doing work in an air engine. The air is compressed by a compressor and the heat which is generated by compression is withdrawn by cooling water. The cold air leaving the expansion en- gine is used for cooling purposes. CYCLE OF OPERATIONS. This may be done in such a way that the air having served for refrigerating purposes is periodically returned to the compressor in the same condition. In this case the operations of the refrigerating system constitute what is termed a perfect cycle, and the thermodynamic laws applicable to such a cycle obtain also in the case of the compressed air machine. Practically it is far more convenient to reject the working fluid (air) along with the refrigeration, but for the purposes of the following calculations, which are rendered after Ledoux, we will assume that the opera- tions of a cycle are fully performed. WORK OF COMPRESSION. For the work, W r , of compression of the air, which is supposed to be done adiabatically (without losing or gain- ing heat), Ledoux gives the following, formula: W r = jj- (P V t P V ) foot-pounds; and also W r = m * c (T x T ) foot-pounds. In these equations P and T are the initial press- ure and temperature of the air, counted from absolute zero. F is the volume described by the piston of the com- pressor cylinder. F! is the volume described by the same piston during the outflow of the compressed air. Pj and TI are the temperature and pressure of the compressed air when leaving the compressor. 256 MECHANICAL REFRIGERATION. A is the reciprocal of the mechanical equivalent of k is the ratio of specific heat of constant pressure to the specific heat of constant volume. 0.23751 _ "0.16844 In the following equations: m stands for the weight of air (in pounds) whose volume passes from F to F,. c stands for the specific heat of air of constant volume. P 2 and T 2 are the pressure and temperature of the air after expansion. F 2 is the volume of the expansion cylinder. TEMPERATURE AFTER COMPRESSION. The temperature, T t1 of the air after adi aba tic com- pression may be found after the following formulae : T _ T /PA^-pI and \P ) T, (ft) COOLING OF THE AIR. The air after having been compressed is cooled down from the temperature T to the temperature T 3 , and volume F 3 , and the quantity of heat, Q^ which must be withdrawn from the air to accomplish this is Q t m k c ( T T 3 ) units. AMOUNT OF WATER REQUIRED. The amount of cooling water, P 1 required is H-H 0.6 (t t l t and t t being the respective temperatures of incoming and outgoing condenser water. WORK DONE BY EXPANSION. The work, W m , which may be obtained theoretically by allowing the air, after being cooled, to expand against AIR AND VACUUM MACHINES. 257 a piston adiabatically until the temperature T z is reached is : ^ r m = ^A^(p 1 y 3 p 2 F 2 ) foot-pounds. or W m = 2% (T 3 T 2 ) foot-pounds. A. TEMPERATURE AFTER EXPANSION. The temperature, T 2 , of the air after expansion is found after the formula : k- I T 3 and P t being the temperature and pressure of the air when entering the expansion cylinder. REFRIGERATION PRODUCED. The refrigeration, H, which is produced by the air during adiabatic expansion is expressed by _ff= m k c ( T T 2 ) units, T being the temperature of the air after it leaves the refrigerator. WORK FOR LIFTING HEAT. The net work, W, therefore which is theoretically required to lift the amount of refrigeration, H, is ex- pressed by the formula W= Wr Wm foot-pounds, or also- tn Ic c r o ) (T 3 I 2 ] J foot-pounds. EQUATION OF CYCLE. If the quantities, Q t1 H and Wr and W m are ex- pressed in the same (thermal) units, the equation of the cycle of operations may be expressed by if Wr and W m are expressed in foot-pounds. 258 MECHANICAL REFRIGERATION. EFFICIENCY OF CYCLE. The theoretical efficiency, E, of this refrigerating cycle may be expressed by the formula: E= ~W = = A (T 1 -T}-(T -T 2 ) T T and - being equal -, we also find 27 rjt -*- rri rji 1 ^O ^3 ^2 This expression is the same as that found for the maximum theoretical efficiency of a reversible refriger- ating machine, page 71. The above formula3 apply also in case any other per- manent gas is employed in place of air. SIZE OF CYLINDERS. From the above equations the relative sizes Fand F 2 of compression and expansion cylinders, for a given amount of refrigeration in a given time, can be readily ascertained for theoretical conditions. The ratio which should exist between the volumes of the two cylinders in order that the air is expelled at atmospheric pressure is expressed by the following equations : V, __ V 2\ V 3 standing for the volume of air after compression and after subsequent cooling, when it has the tempera- ture T 3 . ACTUAL EFFICIENCY. Owing to the bulkiness of air, the compression and expansion cylinders have to be very large, a fact which tends to increase the friction considerably. Besides this there is considerable clearance, and the moisture con- tained in the air also decreases the efficiency, all of which circumstances, combined with others of minor importance, reduce the actual performance of the air machine much below the theoretical efficiency. AIR AND VACUUM MACHINES. RESULTS OF EXPERIMENTS. 259 The foregoing remarks are forcibly illustrated by the following tests of compression machines, which were published by Linde some time ago. The figures in this table show that in the most favorable experiment (Light- foot) the actual efficiency is scarcely 33 per cent of the theoretical efficiency. (After Ledoux the friction alone reduces the theoretical refrigerating for about 25 per cent.) ACTUAL PERFORMANCE OF COLD AIR MACHINES. SYSTEM Bell- Liffhtfoot Colem'n. TF^T No 1 2 3 Diameter of compression cylin- der 28" J 27" j s'gle act'g" j 25H" 1 2-cylinder Diameter of expansion cylinder Diameter of steam cylinder. . 21" 21" 22" j 19 l / 2 " j 2-cylinder i 20" H. P. Stroke of all cylinders 24" 18" 1 31 " L. P. 36" Revolutions per minute 63 2 62 72 Air pressure in receiver, pounds (absolute) 61 65 61 Temperature of air entering the compression cylinder ... 65!4 F 52 F Temperature of air after ex- 52 6 F 82 F. 85 F. I. H. P. in compression cylinder I. H. P. in expansion cylinder.. I. H. P. in steam cylinder B. T. U. abstracted per hour and I. H. P. of steam cylinder at 20 F 124.5 58.5 84.4 668 43.1 28.0 24.6 1,554 346.4 176.2 332.7 954 The figures for test No. 1 have been observed and published by Professor Schroeter( Untersuchungen an Kcelte- maschinen verschiedener Systeme, Munich (1887); those for No. 2 are published in minutes Proc. Inst. Mech. Eng.< London, 1881. The data for trial No. 3 are taken from a paper read last year before the Manchester Society of Engineers. WORK REQUIRED FOR ISOTHERMAL COMPRESSION. If the compression of air takes place isothermically, in which case the air is kept at constant temperature during compression by injection of cold water and a cold water jacket, the work of compression is lessened. The work W 2 in foot-pounds required in theory to compress isothermically V cubic feet of air under a pressure of 260 MECHANICAL REFRIGERATION. P pounds (per square foot) to the volume of F 4 cubic feet is W= P VX 2.3026 log -J- foot-pounds. WORK DONE IN ISOTHERMAL EXPANSION. The work, W lt in foot-pounds which can be done theoretically by the isothermal expansion of F x cubic feet of air to the volume of V cubic feet, and the press- ure P is W, = P VX 2.3026 log-^- OTHER USES OF COMPRESSED AIR. The isothermal expansion of air is employed in cases where compressed air is used, not for refrigeration, but for the production of power, as in tunneling, drilling in mines, transmission of power by compressed air, etc. These are purposes for which the compressed air has been extensively used. TABLE SHOWING LOSS OF PRESSURE BY FRICTION OF COMPRESSED AIR IN PIPES. (F. A. Halsey.) |OOI*>WG;UIWI-H-*I-I w 1 Diameter * * ^ g| of Pipe. Cubic Feet of Free Air compressed to a Gauge Pressure of 60 Ibs. per Square Inch, and passing through the Pipe per Minute. 50 75 100 125 150 200 250 300 400 600 Loss of Pressure in Pounds per Square Inch for each 1,000 Feet of Straight Pipe. Lbs. 10.40 2. (53 1.22 .35 .14 Lbs. 5 90 Lbs. Lbs. Lbs. Lbs. Lbs. Lbs. Lbs. Lbs. 2.75 .79 .32 .11 4.89 1.41 .57 .20 7.65 2.20 .90 .31 .15 11.00 3 17 1.29 .44 .21 5.64 2.30 .78 .38 .20 8.78 3.58 1.23 .59 .31 .10 "5.18 1.77 .85 .45 .15 M rf rH it <* O\ O rH rf CO IO CO UO l> UJ ^D ON rH O 00 fO rH ^ fO N ^ rH ON 00" 777771 I a N a ^ '5 - : Q'T3 g jg OOO o a a ^ i Stairs u I I If is F - illfl ri 1HJI ^'^^S SB Si | ^ o3 C O fl OS bC- ^3 O> O rH N CO < >rt MANAGEMENT OF COMPRESSION PLANT. 273 CHAPTER XIV. MANAGEMENT OF COMPRESS- ION PLANT. INSTALLATION OF PLANT. The installation of a refrigerating plant comprises the proper mounting of all its parts, the proving of the pumps, piping, etc., and the charging of the plant with ammonia. A working test is also frequently made. For the mounting the same rules apply as in the case of other motive machinery. PROVING OF THE MACHINE. In order to prove a new plant, before it is charged with ammonia it should be filled with compressed air to a pressure of about 300 pounds. This is done by working the compressor, while the suction valves pro- vided for this purpose are opened. Thick soap lather, which is spread over the pipes, etc. , shows leaks by the formation of bubbles under the above pressure. The condenser and brine tanks, filled with water, show leaks by the bubbles of air escaping through the water. The air pressure thus obtained on the system may be used to blow out the pipes, valves, etc. After a pressure is pumped on the system, and after the temperature is equalized throughout the whole system, the pressure gauge ought to remain stationary if the plant is abso- lutely air tight. PUMPING A VACUUM. If the machinery is found to be perfectly air tight, all the air is discharged from the system by opening the proper valves and working the pumps. After a vacuum has been obtained all outlets are closed, and the con- stancy of the vacuum is observed on the vacuum gauge to see if the plant will withstand external pressure. CHARGING THE PLANT. After the vacuum is shown to be perfect, the drum with ammonia is connected to the charging valve. Before opening the valve on ammonia flask, the expansion valve between ammonia receiver and expander is closed. Now the liquid ammonia is exhausted into the system, while the compressor is kept running at a very slow speed with suction and discharge valves opened and water running on the condenser. 274 MECHANICAL REFRIGERATION. CHARGING THE PLANT BY DEGREES. If the air is not completely exhausted from the plant, i. e., if the vacuum is not perfect, it is advisable to charge the plant with ammonia by degrees. First about one-half of the total amount of ammonia is charged, and after this has thoroughly circulated in the system, most of the remaining air will have collected in the top of condenser, whence it can be blown off by a cock. After this has been done the balance of the ammonia is charged in a similar way in one or two additional installments. OPERATION OF PLANT. The proper working of a compression machine is chiefly regulated by the amount of ammonia passing through the same, which is done by the expansion valve, which must be manipulated very carefully. The pipe conveying the compressed ammonia to the condenser should not get warm, and the temperature of the brine should be about 5 to 10 F. higher than the temperature corresponding to the indication of pressure gauge on refrigerator. The temperature of the cooling water should be about 10 to 15 F. (sometimes as much as 20) below the temperature corresponding to the pressure in condenser coils. The sound of the liquid ammonia passing the regu- lating valve should be continuous and sonorous, this in- dicating the absence of a mixture of gas and liquid. DETECTION OF LEAKS. If any ammoniacal smell is discovered while charging the plant, it is probably due to leaks, and they should be instantly located and mended. ' It is of importance to discover the existence of a leak at the first inception. When in a machine in operation, the liquid in the tanks begins to smell, it shows either a very considerable leak or one of long standing, and in order to detect a leak readily under those circumstances it is best to test those liquors regularly from time'to time with Nessler's solu- tion, of which a few drops are added to some of the sus- pected liquid in a test tube or other small glass vessel, as described on page 103. MENDING LEAKS. It is a very efficient and simple method to close small leaks by soldering them up with tin solder, which is fre- MANAGEMENT OF COMPRESSION PLANT. 275 quently employed and gives general satisfaction. The soldering fluid, in order to properly clean the iron, should contain some chloride of ammonia, and it is best and proper that its quantity should be such as to form a con- siderable proportion of a double chloride of zinc and am- monia. A soldering liquid of this kind can be made by dissolving in a given amount of muriatic acid as much zinc as it will dissolve, and to do this in such a manner as to be able to ascertain the weight of zinc that has been thus dissolved. An amount of chloride of ammonia or sal ammoniac approximately equal in weight to that of the zinc dissolved is then added to the solution of zinc in muriatic acid. If the leaks are too large to be mended in this way, new coils or new lengths of pipe must be put in. In some cases, where conditions are favorable, electric welding may be resorted to. A cement made by mixing litharge with glycerine to a stiff paste is also recommended for closing leaks. In this case the cement must be fortified by the application of sheet rubber and sheet iron sleeves kept in position by iron clasps. Generally the amount of ammonia is determined after a rule of thumb fashion, allowing one-third pound of ammonia for every running foot of 2-inch pipe (or its equiv- alent) in expansion coils. Thus a plant of twenty-five tons ice making capacity having about 5,000 feet of 2- inch pipe would require about 5 - s - = 1.666 pounds of am- monia, while a direct expansion plant of twenty-five tons refrigerating capacity having at the rate of 2,000 feet of 2- inch pipe would require about 2 -3 = 700 pounds of am- monia. A machine of the same capacity (twenty-five tons refrigeration) with brine circulation would require only about 275 pounds of ammonia. Calculated for capacity, this would correspond to about forty-five pounds of ammonia per ton of ice mak- ing capacity, twenty-five pounds of ammonia per ton of direct expansion refrigerating capacity and twelve pounds of ammonia per ton of refrigerating capacity, brine cir- culation. These rules are arbitrary, some allowing much less ammonia, according to the location of pipes. WASTE OF AMMONIA. Another question of considerable interest to the practical operators of ice plants is in regard to the waste 276 MECHANICAL REFRIGERATION. of ammonia that may be expected to be incurred. Theoretically speaking, no waste ought to take place, as the same quantity of ammonia is used over and over again, but in practice the anhydrous ammonia gives way in the course of time. This is due to leakage in a great measure, and partly also to decomposition of ammonia. The amount of wastage depends, of course, largely on the care with which the plant is operated, and in the absence of any actual leakage is altogether due to decomposition of ammonia, which can be obviated in a great measure by keeping down the temperature around the compressor as much as possible. The amount of ammonia wasted while a machine is running depends almost entirely on the care and watchfulness, and may run all the way up to 200 pounds per year on a plant of twenty-five tons capacity. In some cases it amounts to very little, but about fifty to 100 pounds is generally considered as an un- avoidable waste for a 25-ton machine. Where there is a liquid receiver provided with a gauge glass, the attend- ant can readily tell when the ammonia is running low in the machine. Otherwise the insufficiency of ammonia is shown by a fluctuating pressure, variation in the tem- perature of the discharge pipe, and by the running of the valves in the compressor, which sometimes run smooth and easy, and at other times hard, showing that the sup- ply of ammonia and the consequent resistance varies. A rattling noise of the liquid while passing the ex- pansion valve shows the passage of vapor along with the liquid ammonia, and proves that the ammonia in the system is deficient. AMMONIA IN CASE OF FIRE. It appears that the dangers of ammonia in case of fire have been greatly over-rated, and at least in the begin- ning of a fire it acts as an extinguisher rather than other- wise. For this reason it seems more advisable in case of fire to allow the ammonia to escape whenever it is deemed good policy to stand the loss of the ammonia rather than run the risk of fire. If the latter happened the am- monia would be lost anyhow, and that, too, most likely, at a temperature high enough to make it share in the conflagration, while when allowed to escape, as long as the fire is low it may help to stifle the same or extin- guish it altogether. MANAGEMENT OF COMPRESSION PLANT. 277 Before resorting to such an expedient the pros and cons should, of course, be duly considered, and the at- tendant should properly protect himself by a mask or similar contrivance against the suffocating effect of the ammonia vapors to which he may be exposed while pro- viding means for their escape in the free atmosphere. In order to further provide for such an emergency, the out- let valve at the lower end of the condenser should be conveniently located, as the liquid ammonia should be permitted to escape first. While countenancing such heroic measures, I will not dispute that under certain conditions decomposing ammonia may, through ignition, also become the cause of fire. When, for instance, the head of a compressor running very hot should be blown off , the escaping hot ammonia, especially if saturated with lubricating oil, may be in a condition prone to decompose, and in case these vapors should come in contact with the flame of a light, the fire under the boiler, or a lighted match, a flash of fire might take place, which amid the con- fusion generally attending an accident of this kind might give rise to a destructive conflagration. In view of this possibility, it has been recommended that the lamps in the engine room of a refrigerating plant should be pro- tected by a fine wire screen, that the doors leading to the boiler door should be likewise made of fine wire cloth and be provided with a reliable self-closing contrivance. The lighting of matches, etc., should be avoided in the engine room for the same reason. CONDENSER AND BACK PRESSURE. The lower the pressure and temperature in condenser coil, and the higher the pressure and temperature in ex- panding coil (back pressure), the more economical will be the working of the plant. This is readily apparent from the formulae given for the estimation of the compressor capacity; it is even more readily apparent from the sub- joined tables, showing the actual result obtained by Schroeter in working an anhydrous ammonia compressor under different conditions. For these reasons the cooling water on the condenser should be used as cold as it can be had and in as ample profusion as possible. Likewise the expansion or back pressure should be held as high as possible. In brewery refrigeration, cold storage and other es- tablishments in which the temperature is to be kept at 278 MECHANICAL REFRIGERATION. 32 F., or thereabouts, by direct expansion, a back press- ure of about 33 pounds gauge pressure, corresponding to about 20 F., is generally maintained. In case brine circulation is used for above purposes, the brine returns with a temperature of 24 to 26 F. and enters the room with a temperature of about 20. The back pressure in ammonia coils in this case is 25 to 28 pounds, corresponding to a temperature of 10 to 15 F. During the chilling stage in meat or other cold stor- age, the temperature in the room rises in the beginning to 5(P, and a higher back pressure about 60 pounds, corresponding to a temperature of about 40 in ammonia coil is maintained. Gradually, as the temperature falls in the room, the back pressure also decreases until it reaches the point corresponding to the temperature of the room for cold storage, viz., about 30 pounds. In freezing meat, for which purpose temperatures of F. and below in rooms are required, the back press- ure gets as low as 4 pounds,corresponding to a temperature of 20 F. For ice making a temperature of 10 to 20 is main- tained in the brine, and the back pressure in ammonia coils in this case is from 20 to 28 pounds, corresponding to a temperature of 5 to 15 F. TABLE SHOWING EFFICIENCY OF PLANT UNDER DIFFER- ENT CONDITIONS. 1 2 3 4 Temperature of ) Tnlpf dpo , F refrigerated | gg*?.F Specific heat of brine (per unit of volume), 43.194 37.054 0.8608 28.344 22.885 0.8508 13.952 8.771 0.8427 -0.279 5.879 0.8374 Quantity of brine circulated per hour cu ft .... 1,039.38 908.84 633.89 414.98 Cold produced, B. T. U. per hour Temperature 1 r j t d F &. &!** 342.909 48.832 66.724 263.950 49.476 68.013 172.776 48.931 67.282 121.474 49.098 67.267 condenser, j Quantity of cooling water per 338.76 260.83 187.506 139.99 Heat eliminated by condenser, B. T. U. per hour I. H. P. in compressor cylinder. I. H. P. in stea"m engine cylinder Consumption of steam per hour in Ibs... 378. 358 13.82 15.80 311.51 301.404 14.29 16.47 335.98 214.796 13.53 15.28 -505.87 158.926 11.98 14.24 278.79 1 Per I. H. P. in Cold produced 1 comp. cyl per hour, B. VPer I. H. P. in T. U. steam cyl J Per Ib. of steam 24.813 21.703 1,100.8 18.471 16.026 785.6 12.770 11.307 564.9 10.140 8.530 435.82 MANAGEMENT OF COMPRESSION PLANT. 279 PERMANENT GASES IN PLANT. As long as their amount is small and as long as there is sufficient liquid in the condenser coil to act as a seal preventing the free circulation of the permanent gases in the system, their presence will only decrease the capacity of the condenser coil, as it were, requiring either a little more cooling water or increase the pressure in the condenser. If these gases are present in larger quantity, and especially when there is no excess of liquid ammonia in condenser coils, they will disseminate themselves through the whole plant and interfere both with the economical working of the plant and the correct indications of the gauges, etc. For these reasons the engineers ought to be watchful to prevent any accumulation of such gases. Sometimes they consist chiefly of atmospheric air, but sometimes also of hydrogen and nitrogen, due to the decomposition of ammonia. The best way to remove these gases from the system is by drawing them off at the top of the condenser coil. It is advisable when drawing off the permanent gases to make the condenser as cold as possible by using an excess of cooling water and by stop- ping the inflow of ammonia gas to the condenser for the time being. A small hose, or, better still, a permanent small pipe, may be attached to the top of the condenser or provided with a valve near the condenser, the other end dipping in cold water. If on opening the valve bubbles are seen to escape through the water the valve should be kept open as long as such bubbles appear in the water. If, however, the bubbles cease to appear in noticeable quantity, while a crackling noise in the water indicates that most of the gas escaping through the pipe is ammonia, which is absorbed by the water, then the valve should be closed, as all the permanent gases that can be removed at the time without undue loss of am- monia have been disposed of, at least for the time being. FREEZING BACK. The tendency of freezing back shown by certain ma- chines and not by others, is explained by their mode of working. The former machines work by what is called the method of wet compression, and the others by the method of dry compression. The tendency to freeze back itself involves no loss, for a machine intended for wet compression may also be worked with dry gas, by 280 MECHANICAL REFRIGERATION. opening the expansion valve very little, but in doing so the capacity of the machine is reduced and the power required to work the compressor is increased. PRACTICE IN WET COMPRESSION. In working with wet expansion the object is to deliver the gas from the compressor in a saturated con- dition, but if this were actually done we would never be sure that certain amounts of liquid were not mixed with the gas, which would constitute a severe loss. For this reason it is indicated to allow the temperature of the vapor leaving the compressor to be about 20 above that of the liquid leaving the condenser. Inattention to this point probably accounts for many differences of opinion in regard to dry and wet compression. Any liquid present under such conditions would fill the clear- ance space, and by expanding would destroy a corre- sponding percentage of compressor capacity (^-inch clearance filled with liquid ammonia would reduce the capacity over one- third). ORIGIN OF PERMANENT GASES. In the operation of a compression plant the undue heating of the gas during compression must be consid- ered as the chief cause for the decomposition of am- monia and the origination of permanent gases. How- ever, it also frequently happens that air is drawn into the system through leaks, in case a vacuum has been pumped, which some engineers are unnecessarily in the habit of doing whenever they stop the plant -for a length of time. CLEARANCE MARKS. The clearance in the compressor is not a fixed quan- tity, but changes with the natural wear of cranks and cross-head. For this reason clearance marks should be provided for on the guides and cross-heads of compressors as well as engine. These will indicate if the clearance is equalized at the end of cylinders, and guide us in the matter of keying up the bearings. The clearance should not exceed ^ part of an inch. VALVE LIFT. The lift of compressor valves must be carefully ad- justed to the speed of piston (to get full discharge), sup- ply of condenser water, etc. MANAGEMENT OF COMPRESSION PLANT. 281 If valves are not properly set and cushioned they pound, which may even cause the texture of the metal to change in such a way as to cause their breaking to pieces. PACKING OF COMPRESSOR PISTON. If the piston rod is of uniform diameter and well polished, the packing will last several months, other- wise it may have to be renewed every month. If the compressor valves or pistons should leak, the refrigerator pressure will rise and the condenser pressure will fall. When it becomes necessary to open any part of the plant the ammonia should be transferred to another part, or if this is impracticable it should be removed by absorption in water. POUNDING PUMPS AND ENGINES. Sounds that appear to proceed from first one place and then another about the engine and pumps can gener- ally be located by the use of a piece of rubber tubing, one end of which is held to the ear while the other end is brought close to the suspected place. The opposite ear should be closed to shut oat the sound. An old yet very effective way to locate any noise in- side of an engine or pump cylinder is to place one end of a wrench or other piece of metal between the teeth, and resting the other end on the cylinder head, close both ears. Every sound within the cylinder can thus be readily heard. CLEANING CONDENSER. If the condenser coils have a tendency to become incrusted by deposit from the water, they should be cleaned from time to time. On such occasions they may also be tested with a water pressure of some 400 pounds per square inch to discover corrosion, perforation and other bad places. CLEANING COILS, ETC., FROM OIL. If there is oil in parts of the system whence it cannot be removed by the oil traps, those parts may be blown out, and if consisting of pipe they can be blown out by sections, if practicable. Another way more strongly recommended, and more simple, to clean am- monia pipes from oil, consists in allowing high pressure ammonia gas to enter them; this warms and liquefies the 282 MECHANICAL REFRIGERATION. oil sufficiently to permit of its being drawn (mixed with the ammonia) into the compressor, whence it passes to the oil traps, where it is separated from the ammonia. This method of cleaning the coils is said to be very effective if repeated from time to time, say once a week, or better still, every other day. INSULATION. The most important point in the economical running of a plant is insulation, and especially does this refer to the ammonia on its way from the refrigerator to the compressor, and from the condenser to the refrigerator through the liquid receiver, etc. For these reasons these conduits cannot be insulated too well. The same applies to brine tank, freezing tank, etc. PAINTING BRINE TANKS, ETC. Light colored surfaces radiate and absorb less heat than dark surfaces under the same conditions. Also smooth and bright surfaces will radiate and absorb less heat than rough and dead looking surfaces of the same color. That the differences in radiation brought about in this way are great enough to be quite observable about a refrigeration plant, for instance, on the efficiency of a brine tank or other vats, we make no doubt. For this reason light colors, possibly white, and smoothly varnished at that, are, doubtless, best adapted to all sur- faces. Preferably a white earthy paint, like barytes, etc., but no white lead, should be used for this purpose, LUBRICATION. The oil used for lubricating the compressor differs from ordinary lubricating oil in that it must not congeal at low temperature, and must be free from vegetable or animal oils. For this reason only mineral oils can be used, and of these only such as will stand a low tempera- ture without freezing, such as the best paraffine oil, will do. Kegfular cylinder oil, however, should be used for the steam cylinder, and a free flowing oil of sufficient body for all bearings and other wearing surfaces. For heavy bearings on ice machines a' heavy oil should be used, while small bearings, such as shafts of dynamos, should be lubricated by a very light oil, to avoid undue heating in either case. Graphite or black lead is also an efficient lubricant. MANAGEMENT OF ABSORPTION PLANT. 283 CHAPTER XV. MANAGEMENT OF ABSORP- TION PLANT. MANAGEMENT OF ABSORPTION MACHINE. The management of an ammonia absorption plant has many points in common with that of a compression plant. The detection and mending of leaks, lubrication, the management of ammonia, withdrawal of permanent gas, etc., are the same in both, and they have been en- larged upon in the foregoing. There are, however, many precautions and troubles peculiar to the absorption sys- tem, and the most important of them will be shortly mentioned hereafter, and some of these in turn will also appJv to the operation of the compression plant. INSTALLATION OF ABSORPTION PLANT. The installation and testing of an ammonia absorp- tion plant is generally attended to by the manufacturers. The plant before being put in operation should be tested to a pressure of about 300 pounds per square inch. CHARGING ABSORPTION PLANT. Before the ammonia is charged into the machine, it is necessary to expel from the entire apparatus the air which it naturally contains. There are two methods of doing this, one of which consists in opening all the connecting valves in the machine; leave one open to the atmosphere, introduce direct steam in the retort until all the air is forced out, and then shut the outlet valve and let the apparatus cool off. When it becomes cold, there will be found to be a vacuum in the whole apparatus. It is then ready to receive the ammonia. This method, however, is not to be recommended, as the heat .of the steam will soften the joints, especially if rubber is used. The best way is to pump a vacuum by means of a good pump. The boiler feed pump or the ammonia pump may be used for this purpose, and when a vacuum of twenty-five inches is obtained, close all the valves. Then connect the charge pipe with the drum of aqua ammonia, taking care not to let any air enter the pipe after the drum is empty. Close the charge valve and repeat the operation with another drum, until the vacuum in the machine is gone, and then pump in the balance with the ammonia pump until nearly the requisite charge is put in; then heat the ammonia slowly by turning steam through the heater coils. When the pressure gauge 284 MECHANICAL REFRIGERATION. indicates 100 pounds, more or less, open tbe purge cock and lead the discharge into a pail of cold water through a rubber tube until no air bubbles come out', then turn on the condensing water into the condenser cooler and absorber, and apply the steam until the liquefied gas shows in glass gauge. Then open distributing valve to freezing tank, and turn the poor liquor into absorber, and in a few minutes the ammonia pump may be started to pump the enriched liquor through the coils of ex- changer and into the retort. Let the condensed steam into the deaerator and let cooling water run over the distilled water cooler coils. Let it run out until the water becomes clear and tasteless. Proceed in this way, carefully watching for ammonia leaks wherever there are joints. If none exist, keep on until all the pipes in the freezing tank become coated with frost, and the remaining air has consequently been driven out through the coils and out of the absorber purger. Then close down and proceed and make the brine solution, when the machine is ready to start again and the balance of the ammonia may be put into the machine and operated in the regular manner. OVERCHARGE OF PLANT. In charging an absorption machine with ammonia liquor, which is generally done when it is cold, it sliouid be borne in mind that the liquid expands when heat is applied, and that if the machine is charged to its work- ing point when cold, it will invariably be overcharged under working conditions. In such a case the liquor may go out of sight in the gauge and great variations of pressure take place, which are apt to damage the recti- fying pans, and the proportionate strengths of poor and rich liquor are disturbed. AMMONIA REQUIRED. When the regular automatic operation of the absorp- tion cycle has been inaugurated, a surplus of liquid am- monia should show itself in the liquid receiver. If there is a deficiency in this respect it can be supplied by the ad- dition of anhydrous ammonia, or by the addition of strong ammonia liquor, and the withdrawal of a corresponding amount of weak liquor. The sound of the liquor passing the expansion valve should be continuous and sonorous, as in the case of the compression machine, indicating the absence of a mixture of gas and liquid. MANAGEMENT OF ABSORPTION PLANT. 285 RECHARGING ABSORPTION PLANT. For the purpose of recharging an absorption plant, De Coppet gives the following rational directions: When the gas has leaked out or the liquor has become impov- erished, and knowing the original charge by weight and density, as for instance, say the original charge was 4,000 pounds at 26 B., there would be 1,040 pounds of am- monia in 2,960 of water; if the density through leakage or purging came down to say 23, there would be a loss of 120 pounds in the original charge, which can be easily sup- plied by placing a drum of anhydrous ammonia on a scale, taking a long and small flexible pipe, say a half inch, connected between the drum and same part of the machine, say the feed pipe to freezing tank, weigh the drum accurately before opening the valve, let the liquid gas run in the machine until there are within a few pounds of the quantity missing; run out of the cylinder into the machine, say ten" or fifteen pounds, then close the cylinder valve and try the machine by running it in the usual way for an hour or two. Then add the ten or fifteen pounds extra, and if all the air has been blown out of the tube, and if the ammonia is pure, his machine will work all right again. When the liquor is lacking it is best to recharge the machine with strong aqua at 26 to 28 until the original level is reached, which can easily be ascertained if a glass level or test cock has been placed on the generator or still. He has adopted this method for fifteen years, and finds it far preferable to that of concentrating the liquid and recharging it with rich ammonia afterward, securing the same amount of poor liquor, besides saving time and money. When the question presents itself as to how much anhydrous ammonia, x, in pounds must be added to m pounds of ammonia liquor of the percentage strength a in order to convert it into ammonia liquor of the per- centage strength b, it may be readily answered after the following formula: m (b a) CHARGING WITH RICH LIQUOR. When the absorption system is charged with strong aqua ammonia it happens sometimes that the pump will not readily take the strong liquor. This is due to the great tension of the ammonia in the strong solution, which 286 MECHAK^JAL REFRIGERATION. fills the pump up with ammonia vapor in such a way that the liquid cannot be drawn in. The same thing fre- quently happens with boiler feed pumps, when the feed water becomes nearly boiling hot. Generally it is found that in such cases the pump stands too high; if it stands below the liquid to be pumped the latter will fill the pump in preference to the vapor,.and the pump will gen- erally work all right. It should be noticed, however, that this artifice of elevating the receptacle containing the rich liquor above the pump will only be efficient if it is done in such a manner that the liquid will run into and fill the pump by its own gravity. If the liquid has to be syphoned over by the pump, it will make little difference whether the pump stands a little above or below the liquor, as in either case the vapor of the rich liquor will fill the syphon and pump in preference to the liquid if the pump is not in first-class working order. This tendency is increased when the pump is allowed to run dry and hot on starting, and for this reason the cooling of the pump with water frequently remedies the trouble. This, the cooling of the pump, so it will take the rich liquor, may be accomplished according to a practical operator by stopping the pump, while the machine otherwise is running as usual. In this way the absorber is cooled down in a short time ; mean- while the drum containing the rich liquor has also been connected with the pump which is now started first to pump cold liquor from the absorber for a few seconds when the absorber valve is closed and the pump started on the rich liquor, which will then be taken readily. If not the procedure may be repeated once or twice. PERMANENT GASES IN ABSORPTION PLANT. The permanent gases in the absorption plant may be due to decomposition of ammonia and also air which has found its way into the system. It appears, however, that the decomposition of water vapor in the presence of iron (and probably iron containing carbon in a greater quantity or in a more dissolvable form than other iron) is largely responsible for their presence. The carbon which is pres- ent in all iron may also combine with hydrogen, forming carburetted hydrogen. That the nature of the iron of still and condenser worms has some influence in this direction is proven by the fact that some plants are MANAGEMENT OF ABSORPTION PLANT. 287 much more damaged by these corroding influences than others. This difference in behavior must be attributed to the iron rather than to the ammonia. CORROSION OF COILS. As may be inferred from the foregoing paragraph, it will not only be the permanent gases, thus found, which annoy the manufacturer, but also the corrosion and con- sequent destruction of the coils and tanks. This is, in- deed, the case especially in the upper regions of ammonia still and in the condenser. As a precautionary measure it is well to have the coil in the still always covered with liquid. ECONOMIZING CONDENSER COILS. As has been stated, the iron of the coil or worm in condenser and in the ammonia still suffers much from pitting and corrosion, especially if the liquid does not al- ways stand above the coil in the still. Coddington finds that the pitting takes place first at the top of the coils, and therefore he has found it a good practice to turn the condenser coil over after a certain period, say after it has been used about four years. KINDS OF AQUA AMMONIA. The difference between the different kinds of aqua ammonia in the market is only in strength and price, the latter differing like that of other commodities, according to the law of demand and supply. At present, we find in the market (according to Beaume hydrometer scale for liquids lighter than water, the latter showing 100): 1. 16 aqua ammonia, often called by druggists F. F. F., containing a little more than 10 per cent of pure anhydrous ammonia. 2. 18 aqua ammonia, called by druggists F. F; F. F., containing nearly 14 per cent of anhydrous ammonia. 3. 26 aqua ammonia, called by druggists stronger aqua ammonia, and containing 29^ per cent of pure anhydrous ammonia. This is the aqua ammonia gener- ally used in absorption plants for the start. At last quoting the prices (in carboys) were about two and one- half cents per pound for the 16, three and one-half cents per pound for the 18 and four and three-quarters cents per pound for the 26, the latter not in carboys, but in iron drums. 288 MECHANICAL REFRIGERATION. It is also frequently supposed that a difference in the nature of ammonia is due to the different sources from which it is derived, viz., from gas liquor direct, or from intermediate sulphate of soda, but manufacturers claim, and with apparent reason, that this is not the case if both kinds are equally well purified. LEAKS IN ABSORPTION PLANT. If, while the pump and generator appear to work regularly, there is a great disproportion in the strength of the poor and the rich liquor, so that the strength of the former to the latter is 22 to 25, where it should be 17 to 28, or thereabouts, it is likely due to some leaks, more particularly in the exchanger or equalizer or in the recti- fying pans. LEAK IN EXCHANGER. If there is a leak in the equalizer coil large enough to seriously affect the working of the machine, the pipe connecting the equalizer and the coil in the weak liquor tank will become cool when the pump is running fast, and the equalizer will be cool back to a short distance from the leak, where the cold ammonia from the absorber mingles with the weak liquor from the generator. And at times, when the pump is running very fast, the whole weak liquor line may cool back to within a few inches of the generator, showing that strong ammonia is being pumped into the bottom and top of generator, as well as into absorber. There will also be a ringing or hissing noise in the neighborhood of the leak. First locate the trouble in the equalizer by noticing the cooling of the pipes, and then find the place in the equalizer by feeling the different sections with the pump running slower, having also the assistance of an ear tube. Another way to try an exchanger coil while the machine is running is as follows: Close poor liquor valve between the generator and exchanger; close absorber poor liquor feed, and run pump as slow as possible; open the poor liquor feed wide; if there is a leak, the pump will start faster. When the poor liquor feed is closed at the absorber and between retort and exchanger, the pump is working against the generator's pressure, while when the absorber feed is wide open the pump is work- ing against a lower pressure (ten pounds per square inch) through the leaky coil of the exchanger, then to the absorber, thus forcing a by-pass circulation of rich or MANAGEMENT OF ABSORPTION PLANT. 289 enriched poor liquor from the absorber through the exchanger, through the leak of the coil of the exchanger, back through the poor liquid cooler and to the absorber again. If the leak in the coil is of a large size, the machine will come to a standstill, and will stay that way until the leaky coil is not removed. LEAK IN RECTIFYING PANS. If under existing regularities in the relative strength of the poor and rich liquor the exchanger has not been found leaking, but perfect in its working, it is almost beyond doubt that the rectifying pans are out of order. In order to make sure on this point a certain small quantity of the liquefied ammonia may be withdrawn from the liquid receiver, and then be allowed to evapo- rate (the vessel containing the ammonia being placed in ice water). If under these conditions a remnant (water) amounting to 20 per cent and more is shown, then there is doubtless a leak in the rectifying pans, which should be repaired. STKONG LIQUOR SYPHONED OVER. When the ammonia is short in a machine the same may be absorbed so quickly in the absorber as to cause the contents of the still to be syphoned or drawn over in the absorber and (if not guarded against by check valve) into the refrigerator. Defective action of the am- monia pump may cause the same trouble. For this rea- son the gauge at still must be closely watched, so that the liquor always covers the steam coil, by which an un- due decomposition of the ammonia and formation of per- manent gases is also avoided. This siphoning over of the ammonia from one part of the system, and absorption into, another where it does not belong, is frequently called a " boil-over "; and besides the siphoning over of the liquid to the absorber, etc., it sometimes happens, also, that the liquid runs over from the generator into the condenser coils. If the liquified or condensed ammonia collects promptly in the liquid receiver, which shows on the gauge glass of same, there is always pressure enough behind the expansion valve to hold the ammonia in the generator, and there will be no danger of a boil-over unless the am- monia pump receives the liquid from the absorber too fast. To avoid this the absorber is always supplied with 290 MECHANICAL REFRIGERATION. a gauge glass, so the ammonia can be kept at a certain height by means of a valve commonly called the poor liquor valve. But if the engineer does not watch it very closely, the ammonia will get out of his sight, and some- times even into the expansion coils. This is sometimes made worse by not having a governor on tfce ammonia pump, which is sure to vary with the variation in steam pressure, causing the pump to run faster or slower. REMEDY FOR BOIL-OVER. If, however, through carelessness on these points or otherwise, a boil-over into the expansion coils has taken place it may become necessary to nearly close the expan- sion valve long enough to pump a vacuum on the absorber, and then blow what gas is on hand through the coils. This generally cleans them and takes the ammonia back to the absorber. This- is rather troublesome work, but the work will have to be done before the machine will work satisfactorily. If the expansion coils are divided in sections sup- plied by manifolds, so that all the sections except one can be shut off, and all the ammonia gas be made to pass through one section at a time, each of the sections can be cleaned without pumping a vacuum on the absorber. CORRECTION OF AMMONIA IN SYSTEM. To avoid the boil-over or siphoning over, the gen- erator gauge must be closely watched, as has already been mentioned, and if the liquid line is not visible in the gen- erator the weak liquor should be cut off from the absorber, and the generator glass watched to see if the liquid rises; and if it does, and no part of thechargehas goneo\ er into condenser or brine tank coil, and the absorber has been pumped down below where it is usually carried, it is a plain case of shortage of aqua ammonia. If there is no frost on the pipes, and the receiver glass is full of liquid, the weak liquor valve should be left closed and the expansion valve opened wider; and if the absorber fills without much of the rumbling noise, it is filling with liquid from the brine tank coil. If the machine is found to contain enough ammonia, and there is no leak in the pans or the equal- izer, and the head pressure is too low and the back press- ure too high, the trouble is to be found in the pump. But if the high pressure is too low and the low pressure not too high, with everything else all right, the machine should have an addition of anhydrous ammonia. MANAGEMENT OF ABSORPTION PLANT. 291 CLEANING THE ABSORBER. Most cooling waters used in the operation of absorb- ers in connection with absorption machines contain carbonates of lime, magnesia and iron in sufficient quan- tity to form a scale inside of the absorber. This scale consists of the carbonate of lime, etc., mentioned before, which becomes insoluble at the temperature of the ab- sorber, owing to the volatilization of the free carbonic acid in the water which held them in solution. It is a matter of considerable trouble, but also of necessity, to remove this scale from time to time, which depends on the nature of the water. This is generally done by taking the coils out and suspending them over a fire to be heated considerably above the boiling point of water (not red hot, however). While still hot, or better still, after cooling, the scale may be removed by hammering and rolling the coil about. As a much simpler device Coddington recommends the use of crude hydrochloric acid (price two and a half cents per pound) diluted with six times its weight of water. With this mixture he fills up the coils and lets them stand until it ceases to digest the scale, which usually requires two hours. If one dose of acid does not 'clean the pipe thoroughly he repeats the same. In this case it is not required to remove the coils at all, but only the bottom and top of the absorber have to be dis- connected. Some care, however, must doubtless be ex- ercised, so as not to have the acid act for too long a time, as in that case the iron of the coil itself might be affected. HIGH PRESSURE IN ABSORBER. Too high pressure in the absorber, anq^, incidentally thereto, too high temperature in the refrigerator, may be due to too much liquid in the system, or to too little cool- ing water. Too high pressure in the absorber may also be due to air or permanent gases in the system. These must be withdrawn through the purge cock at the top of the absorber, through a pipe or hose leading into a bucket of water, as described under the head of .compression plant. OPERATING THE ABSORBER. It is often claimed that the absorber runs too hot, which may be due to the presence of permanent gases, due to decomposition of ammonia or to the presence of air, or to incrustation of the pipes, all of which prevent 292 MECHANICAL REFRIGERATION. the full utilization of the cooling surface of the con- denser. It may also be that in such a case the ex- changer does not do its full duty or that ammonia pump is not in good working order and that it does not displace a sufficient amount of liquid. Another point of great importance in this respect is the proper regulation of the expansion valve, so as to prevent any excess of ammonia entering the refrigerator and the absorber. Any ammonia which enters the ab- sorber in a non-volatilized or wet condition, means so much additional heat in the absorber, more cooling water and more waste all around. For this reason we are advised to so regulate our expansion valve that the pressure on absorber gauge is about three pounds, and not much over. If, on the other hand, there is too little or no press- ure on the absorber, the ammonia pump will not do its duty, and this will be prevented by the foregoing press- ure on absorber also. In order to correct too low a press- ure in the absorber the decrease of the water supply to the latter is generally the most convenient remedy. PACKING AMMONIA PUMP. The packing of the liquor or ammonia pump is done the same way as in case of any other pump, but owing to the pressure and the smell in case of leaks it ought to be attended to with special precaution. The packing used should be of the best kind, as it will wear least on the rods, and does not require to be pulled up so tight, which increases the work and the wear and tear. The pump rod should be turned true if unevenly worn, as it is next to impossible to pack a bad rod well. Any good hemp packing is excellent for most pumps. It should be well packed into the stuffing box, but not too hard. If, after screwing down the nut in place, the box is not full, remove the nut again and put in more pack- ing. Replace the nut and screw well down, not too tight. If properly done, thumb and finger will screw the nut tight enough. The piston rod should be kept properly oiled. The packing nuts should be tightened up from time to time, and the packing should be renewed occasion- ally without waiting till it is burned out. Some operators use pure gum rings that will slip into the stuffing box with light pressure. Square or rectangular gums will answer if the rings are not convenient to get. This packing must not be screwed down too tight, as the ammonia MANAGEMENT OF ABSORPTION PLANT. 293 will swell the rubber, and in that case it may bind the rod so tightly that it will roll it out of the stuffing box. Use mineral oil for lubricating. ECONOMIZING WATER. The economizing of water is a question of even more importance with the absorption system than with the compression system, as it is used not only in the condenser and boiler, but also for the absorber. In this case also it can be recooled and re-used by gradation, and in locali- ties where the water is warm, it may be good policy to cool it by gradation in the first place. The water after hav- ing passed the absorber is better for boiler feeding than the natural water, not only because it is heated to some extent already, but also because it has already deposited some or most of its mineral matter which would tend to form scale in the boiler. The cooling water after hav- ing left the absorber might be used to condense the moist steam from ammonia pump, in case this is also needed for ice making before it enters the boiler. Some absorption machines use the cooling water for the double purpose of cooling the absorber first, and then the condenser, or vice versa. OPERATING BRINE TANK. The principal information relating to brine and freezing tanks is given elsewhere. The following may be added relative to their operation: In order to be able to fully utilize the coils in brine tanks, they should be made in short runs, and kept free from ice. Sometimes when the brine is not strong enough, the formation of ice around the expansion coil may take place, and this greatly reduces the capacity of the freezing tank, and in some measure accounts for the great variation in pipe lengths required in different plants. No galvanized iron pipe should be used for direct expansion, and con- nections, etc., should be made with extra strong unions, flanged joints, etc. No right and left coupling, nor ordi- nary couplings should be used, and the element of un- certainty should be entirely avoided. LEAKS IN BRINE TANKS. Small leaks in brine tanks may sometimes be stopped by the application of bran or corn meal near the place where the leak is. The meal or bran should be carried (in small portions at the time) to the place where the leak is, by means of a short piece of open pipe. 294 MECHANICAL REFRIGERATION. In making repairs to coils while immersed in brine the workmen should besmear their arms and hands with cylinder oil, lard or tallow, as that will enable them to keep them in the cold brine without much inconven- ience for some time. TOP AND BOTTOM FEED BRINE COILS. The expansion coils in brine tanks are fed from bot- tom or top according to the system of refrigeration, as mentioned elsewhere, but it is claimed that the disad- vantages of both ways of feeding can be avoided by using what is called TOP FEED AND BOTTOM EXPANSION. This system is a combination of the best elements of the two systems above described. Each alternate coil in a tank is connected to a liquid manifold (provided with regulating valves) at the top of the tank, and the ammonia is evaporated downward through one-half of the coils in the tank. All of the coils in the tank are connected to a large bottom manifold (which might be called an equalizing expansion manifold), and the gas is returned up through the second half of the coils to a gas suction manifold at the top of the tank, located be- hind and a little above the. liquid manifold. The suction manifold is provided with a tee for connecting the suction pipe leading to the compressors. CLEANING BRINE COILS. When the pipes in the brine tank are to be blown out by steam, the brine must be removed and the head- ers of the coils must be disconnected and each coil must be steamed out separately with dry steam, care being taken to let the steam blow through the coils long enough to heat them thoroughly, so that when the steam is shut off the coils are left hot enough to absorb all moisture inside. DRIPPING CEILING. Dripping ceiling is an awkward trouble liable to oc- cur where rooms are to be refrigerated. There seems to be no universal cure for a dripping ceiling; even as to the causes of such occurrence the most experienced en- gineers seem to have only conjectures. In some cases it seems that in storage rooms located one above the other the ceiling of the lower drips on account of the cold floor above. In other cases it appears that the space between the ceiling and refrigerating coils is too small, MANAGEMENT OF ABSORPTION PLANT. 295 allowing condensation to form on the ceiling which oth- erwise would have settled on the pipes again. It is asserted that porous ceilings, formed with brick arches laid in ordinary mortar, will prevent condensation over- head, while ceilings formed of sheet metal, wood painted, and varnish air tight and ditto cement ceilings are prone to condense moisture. The dripping from re- frigerating coils should be caught in drip pans placed or hung below them, and, generally speaking, the drippings ought to be prevented from entering the fermenting tubs, dripping over meat, vegetables and cold storage goods in general. REMOVING ICE FROM COILS. The removal of ice from ammonia expansion coils can be best effected by allowing hot ammonia vapor to enter them, and a connection to permit this should be provided for. The ice can be thawed off in this way or loosened so that it can be knocked off. If the ice is re- moved soon after it has formed, say daily, it is sufficiently loose in itself, so that it can be cleaned off without any special artifices. MANAGEMENT OF OTHER PLANTS. The* management of other refrigeration plants, notably of those which work on the compression plan, such as the sulphurous acid, the carbonic acid and" Pictet liquid " machines, is in most principal points like that of the ammonia compression machines. In the case of carbonic acid it is somewhat difficult to detect and locate leaks on account of its being free from odor. The best avail- able means in this connection are soapsuds, smeared over the pipes, joints, etc., when leaks will demonstrate themselves by the formation of bubbles. COST OF REFRIGERATION. The principal expense in the production of artificial refrigeration and artificial ice is coal and labor. And as it takes much less labor in proportion to run a large plant than a small one, it is evident that larger plants, especially for ice making, are more profitable. Also less coal is required for larger than for smaller plants. While four men are required to operate ice plants of one to five tons capacity, it will take only five men to operate a 10- ton plant, and only eight men to operate a 35- ton plant. 296 MECHANICAL REFRIGERATION. CHAPTER XVI. TESTING OF PLANT. TESTING OF PLANT. The testing of a plant is executed in different ways in accordance with what the test is intended to prove. When the question is simply as to what a plant can be made to do, independent of the use of coal, the use of condensing water and the wear and tear of machinery, the test is simply a matter of shoveling coal and pumping condenser water. However, the time of such tests has gone by, and the question nowadays is, as to what a ma- chine will do under normal comparable conditions and as to how the refrigeration produced compares with the amount of work expended and the amount of coal con- sumed. FITTING UP FOR TEST. To make a test of this kind a number of preparations have to be made. The compressor as well as the steam en- gine has to be provided with indicators; the condensing water supply has to be connected with a meter, and the amount of brine circulated must be ascertained in a similar manner. The temperature of incoming and out- going brine, of the incoming and outgoing condenser water, must be measured as exactly as possible,. as also the actual temperature of the gas when entering and leaving the compressor, for which purpose mercury wells should be placed in the suction and discharge pipe near the compressor. MERCURY WELLS. A mercury well is simply a short piece of pipe, closed at one end and fitted tightly into a pipe or vessel, the temperature of which is to be ascertained. The pipe is filled with mercury, and an exact thermometer is placed in the latter. THE INDICATOR DIAGRAM. An indicator diagram shows the outline of a surface, limited on one side by a horizontal line, the length of which represents the length of the stroke of a piston (of a pump, engine, compressor, etc.), in reduced scale. A line connecting the two ends of the straight line overhead is formed by connecting the points, which by their vertical distance from the said horizontal line indicate the press ure working on the piston when passing their respective points on the horizontal line on a certain scale. TESTING OF PLANT. 297 These diagrams are obtained by instruments called indicators, which are applied in accordance with instruc- tions accompanying each instrument when bought. The area of such a diagram limited by a straight line on one side and by a curve on the other sides, repre- sents the work done by the compressor during one stroke in foot-pounds. The area of the diagram may be found by calculation in dividing the same into convenient sections, measuring them and adding them up. The area may also be measured by a machine con- structed for this purpose, called a planimeter. With proper precaution and an accurate scale, the area of these diagrams can also be ascertained by cutting them out carefully and weighing them. The weight so obtained can then be compared with that of a rectangu- lar piece of paper of the same thickness and known sur- face. In addition to the actual work done by or applied to a piston during each stroke, these diagrams show at a glance the conditions of pressure at the different posi- tions of the piston, give also a ready idea of the regular- ity of its working, the working of the valves and the changes of temperature. CALCULATION OF DIAGRAM. Usually, and in the absence of a planimeter, the indi- cator diagram of the compressor is divided into ten ver- tical stripes, the median heights of which are added and divided by 10, whereby the median height of the dia- gram is found in inches or millimeters. As it is known for every indicator spring what pressure corresponds to one millimeter or to one inch or fraction of an inch, we can readily find the mean pressure of the compressor from the average height of the diagram. The average pressure in pounds per square inch multiplied by the area of the piston in square inches and by the number of feet trav- eled by the same per minute gives the work of the com- pressor in foot-pounds per minute, which may be divided by 33,000 to find the horse power of the compressor. In close calculations allowance must be made for the thick- ness of the piston rod in double-acting compressors, as the area of the piston is lessened on one side to that ex- tent. It is also well to obtain a number of indicator dia- grams at intervals of from ten to thirty minutes. 298 MECHANICAL, REFRIGERATION. MEAN PRESSURE OF COMPRESSOR. In the absence of an indicator diagram the mean pressure in the compressor, and indirectly the work of the compressor, may be found approximately rn the accompanying table (De La Yergne's catalogue) from the refrigerator and condenser pressure and temperature. TH fr- 00 iH GS'OSO CD fr- 1C CO CO COfr-fr- fr- OO 00 OO OO CO rHCOCO COfMOq ^ O CO OO fr- TJH OOOSfr- OOOO OrHtO IO CD fr- OO fr- fr- IO CO O 8 3 & g oo ooo OO O O O rHTH ooo ooo O tO O O O IO rHrHCsJ (MCOCO Tt< CD OS CO CD CD O -^ OO CO OS i-KM (M CORRECT BASIS FOR CALCULATION. The foregoing method for the calculation of maximum theoretical capacity is based on the temperatures of the ammonia vapor in suction pipe and in the condenser. It is, 304 MECHANICAL REFRIGERATION. however, argued (by Linde and others) and with consid- erable force, we think that the temperatures of brine leaving the brine tank, and of water leaving the conden- ser should be used instead. The latter method is fol- lowed in the calculation relating to the compression ma- chine on page 115, etc. It is true the results obtained by the former method of calculation will come nearer to the practical results, but those obtained by the latter method will give more comparable results as regards the efficiency of different machines. MORE ELABORATE TEST. For more elaborate tests, the loss of refrigeration in engine rooms and a number of other details must be con- sidered, and additional mercury wells will be necessary. TABLE SHOWING DATA OF TEST. The following table showing another series of tests made by Schroeter, at Munich, gives the different quan- tities which should be ascertained, and they also show the difference in efficiency of one and the same machine if worked under different conditions: NUMBER OP EXPERIMENT. 1 2 3 STEAAI ENGINE. Feed, water per hour in gals. . . . 48.3 71 26.2 44.91 18.88 15. ?1 135.2 55.2 42.8 37.2 65,051 1.250 .850 310,335 49.21 67.57 ol9.338 355,950 .060 .049 62 49 70 26.3 45.10 18.99 14.98 131.2 41.89 28.37 22.97 50,364 1.250 .846 230,657 49.17 67.34 15,041 273,891 .082 .065 65 64 84 as. 5 44.97 24.06 21.54 199.2 41.9 28.35 22.99 43,115 1.247 .846 195,920 40.42 95.60 5,328 248,680 .123 .109 27 Temperature of feed water, F Mean pressure (indicator), pounds per square inch. Revolutions per minute Work done in horse powers COMPRESSOR. Work done by compressor in horse Pressure in condenser coils REFRIGERATOR. Temperature of incoming brine Brine circulating per hour in Ibs Specific gravity of brine Heat absorbed in refrigerator in cal- CONDENSER. Temperature of condenser water F. . Temperature of outgoing condenser water Amount of condenser water per hour, Heat absorbed in condenser in calories Horse power produced by engine per 1,000 units refrigeration Horse power used in compressor per 1 000 units refrigeration Pounds of condensing water used per 1 000 units refrigeration TESTING OF PLANT. 305 EFFICIENCY OF ENGINE AND BOILER. To determine the efficiency of engine and boiler the amount of coal used per indicated horse power of engine must also be ascertained. Frequently also the amount of steam used by the engine is determined by means of calorimetric test. (See page 109.) TEST OF ABSORPTION PLANT. The testing of an absorption plant can be executed on similar lines, and the various movements of efficiency can be calculated from the elements of the test, refer- ence being had to the formulas given in the chapter on the absorption machine. For crude tests the amount of coal used within a certain time, to heat the ammonia still and to propel the ammonia pump, is directly com- pared with the amount of ice produced or with the re- frigeration, as it can be measured by the work done in brine tank as shown in the foregoing. MORE EXACT TESTS. For more exact tests, the temperature and pressure in the different parts of the plant must be closely ob- served, the work done by the ammonia pump must be ascertained, the strength of weak and rich liquor and a number of other items must be recorded in order to ob- tain not only an idea of the actual capacity of the plant, but also to learn in what, if in any, respect the same is falling short, and in what direction a possible remedy may be looked for. To show more clearly what is wanted in this direction, we append the tabulated record of a test made of an absorption machine by Professor Denton some time; not that we think it represents an exemplary capacity, but simply to show how the items of the test may be arranged. , DISCUSSION OF TABLE. The actual amount of coal used is not measured in the foregoing test. If we assume that one pound of coal makes about eight pounds of steam, the foregoing test shows that one pound of coal would give a refriger- ating effect equivalent to the melting of somewhat less than fourteen pounds of ice, which would correspond to an actual ice making capacity of about seven pounds of ice per pound of coal. From a letter written from southern Louisiana, recently shown us, it appears that an absorp- tion machine in regular operation in that locality fur- 306 MECHANICAL REFRIGERATION. nishes eight pounds of ice per pound of coal used as a minimum. TABLE SHOWING RESULTS OF TEST. Average pressures above atmosphere, generator Ibs. per sq. in. 150.77 steam " 47.70 cooler 23.69 absorber 23.4 temperatures, deg. F., generator 272. condenser inlet 64H.. outlet 80. range 25!4. brine inlet 21.20 outlet 16.14 range 5.0Q absorber inlet 80. outlet 111. " range 31. heater upper, outlet to generator 212. lower absorber 178. inlet from 132. inlet from generator 272. water returned to main- boilers. . 260. Steam per hour for boiler and ammonia pumps, Ibs 1,986. Brine circulated per hour, cu. ft.. 4 1,633.7 pounds 119,260 " specific heat 0.8CO heat eliminated per lb., B. T. U 4.104 " cooling capacity per 24 hours, tons of melting ice 40.67 " lb. of steam, B.T. U... 243. " ice melting capacity per 10 Ibs. of steam, Ibs 17.1 Heat rejected at condenser per hour, B. T. U 918,000 "absorber " " ...1,116,000 " consumed by gen. per lb. of steam condensed, B. T. U. 932 Condensing water per hour, Ibs 36,000 coil, approx. sq. ft. of surface 870 Absorber " " " " 350 Steam 200 Pump ammonia, dia. steam cyl., in " ammonia cyl., in 3% ' stroke,in ' revolutions -per minute brine steam cyl., diam., in 954 " brine " " " 8 stroke,in 10 revolutions per min 70 Effective stroke of pumps 0.8 of full stroke. ESTIMATES AND PROPOSALS. By way of recapitulation it may be mentioned that in ordering refrigerating machines, or in asking for esti- mates or proposals, one cannot be too explipit in stating the conditions under which the plant is calculated to work and what it is expected to accomplish. Foremost should be stated: First. The temperature and quantity of the available water supply should be given under all circumstances, and also the average temperature during the different seasons, if possible. Second. If water power or a surplus of steam power is available, it should be specified; also the price and kind of coal, if possible. TESTING OF PLANT. 307 Third. The kind of machine that is required, whether absorption or compression, and whether am- monia or some other refrigerating agent is to be used. In case the principal object of the plant is the pro- duction of ice, the following additional points should be clearly specified: (a) If absolutely pure and clear ice is required, i. e., ice made from distilled water, or whether opaque and relatively impure ice will answer. (6) If the required buildings are to be erected in wood or masonry, or if already existing buildings are to be utilized, and in the latter case, dimensions and mode of construction. (c) The amount of ice that is to be produced in twenty-four hours. MISCELLANEOUS REFRIGERATION. For the refrigeration of rooms in breweries, packing houses or cold storage establishments, etc., the follow- ing additional points should be specified, or as many of them as is practicable. (a) If the rooms are to be refrigerated by direct ex- pansion or by brine circulation. (6) The size of rooms, the construction of the walls and the temperature at which they are to be held. (c) The amount and kind of beer to be brewed, and the time it is proposed to be kept in storage in case of a brewery. (d) In the case of a packing house, the number and kind of animals to be chilled daily, and the number and kind of carcasses to be frozen, and the length of time they are to be kept in storage. (e) In the case of a cold storage establishment, the nature of the products to be stored, or the temperature at which they are to be held, and the amount of what is to be placed into cold storage daily. CONTRACTS. In case contracts are made for refrigerating machin- ery, the amount of coal and water to be used for a cer- tain specified duty, should apply to a specified kind of coal, to the temperature of the actual water supply (not to fictitious conditions), and to a specified number of rev- olutions of compressor or pump for specified dimensions. 308 MECHANICAL REFRIGERATION. In order to ascertain the amount of refrigeration which may be expected from an existing compressor, the diameter, length of stroke and number of revolutions should be given. Also state whether single or double- acting; the temperature of the cooling water; the back pressure and pressure or temperature (both if practic- able) in condenser. UNIT OF REFRIGERATING CAPACITY. In accordance with some British writers, the refrig- erating capacity of one ton of melting ice is equivalent to 318,080 thermal units. In the United States 284,000 thermal units are allowed to be equivalent to one ton of refrigerating capacity, or to the refrigerating capacity of one ton of melting ice. This disagreement is due to the dif- ferent amount of ice which is taken to make up a ton. In the former case 2,240 pounds are calculated per ton, and in the latter only 2,000 pounds are allowed per ton. TEST OF OTHER MACHINES. The testing of other refrigerating machines, such as are operated with sulphurous acid, carbonic acid, Pictet's liquid, etc., can be performed on the same lines as that of the ammonia compression machine. A similar course also applies in the case of air compression, vacuum ma- chines and other devices, the principal question always being as to what amount of coal or power and of cooling water is required to produce a certain amount of refrig- eration. In comparing the efficiency of machines in different localities due allowance must always be made for differences in the water supply, its temperature, its accessibility and available quantity. APPENDIX I. APPENDIX I. TABLES, ETC. 309 Area of Area of Area of Area of Area of Area of Area of Area of Area of cycloid s,ny regular polygon. MENSURATION. MENSURATION OF SURFACES. any parallelogram = base X perpendicular height. any triangle = base X H perpendicular height. any circle = diameter? X .7854. sector of circle = arc X y% radius. segment of circle = area of sector of equal radius, less area of triangle. parabola = base X % height. ellipse = longest diameter X shortest di- ameter X .7854. area of generating circle X 3. sum of its sides X perpendicular from its center to one of its sides -f- 2. area of both ends + length X circumference. of cone = area of base -f circumference of base X y z slant height. of sphere diameter? X 3. 1415. of frustum = sum of girth at both ends X y t slant height + area of both ends. of cylindrical ring = thickness of ring added to the inner diameter X by the thickness X 9. 8698. of segment = height of segment X by whole circumference of sphere of which it is a part. POLYGONS. 1. To find the area of any regular polygon: Square one of its sides, and multiply said square by the number in first column of the following table. 2. Having a side of a regular polygon, to find the radius of a circumscribing circle: Multiply the side by the corresponding number in the second column. 3. Having the radius of a circumscribing circle, to find the side of the inscribed regular polygon: Multiply the radius by the corresponding number in third column. Surface of cylinder Surface Surface Surface Surface Surface Num- ber Name of 1 Area 2 Radius Side Angle con- tained of Polygon. = SX = SX = RX between Sides. two sides. 3 ( Equila- ) -j teral [ .433 .5774 1.732 60 ( Triangle. J 4 Square 1. .7071 1.4142 90 5 Pentagon. . 1.7205 .8507 1.1756 108 6 Hexagon.. . 2.5891 1. 120 7 Heptagon. . B.6339 !l524 .8678 128.57 8 Octagon . . . 4.8284 .3066 .7654 135 9' Nonagon.. . 6.1818 .4619 .684 140 10 Decagon . . . 7.6942 .618 .618 144 11 Undecagon.. 9.3656 .7747 .5635 147.27 12 Dodecagon . 11.1962 1.9319 .5176 160 In the heads of the columns in above table, S = side, and K = radius . 310 MECHANICAL REFRIGERATION. PROPERTIES OF THE CIRCLE. Diameter X 3.14159 = circumference. Diameter X .8862 = side of an equal square. Diameter X .7071 = side of an inscribed square. Diameterz X .7854 = area of circle. Radius X 6.28318 = circumference, Circumference -f- 3.14159= diameter. The circle contains a greater area than any plane figure bounded by an equal perimeter or outline. The areas of circles are to each other as the squares of their diameters. Any circle whose diameter is double that of another contains four times the area of the other. Area of a circle is equal to the area of a triangle whose base equals the circumference, and perpendicular equals the radius. MENSURATION OF SOLIDS. Cylinder = area of one end X length, Sphere = cube of diameter X .5236. Segment of sphere = square root of the height added to three times the square of radius of base X height and .5236. Cone or pyramid = area of base X ^ perpendicular height. Frustum of a cone = product of diameter of both ends + sum of their squares X per- pendicular height X .2618. Frustum of a pyramid = sum of the areas of the two ends + square root of their product, X % of the perpendicular height. Solidity of a wedge = area of base X l / 2 perpendic'r height. Frustum of a wedge = y z perpendicular height X sum of the areas of the two ends. Solidity of a ring = thickness -f- inner diameter, X square of the thickness X 2 . 4674. POLYHEDRONS. 1 1 3 4 Radius of Radius of No. N times Circum- Inscribed Area of Cubic of scribed Circle. Surface. Contents. Sides Circle. R=SX R = SX A= S2X C= SsX 4 Tetrahedron . . . .6124 .2041 1.7320 .1178 6 Hexahedron. . .866 .5 6. 1. 8 Octahedron .7071 .4082 3.4641 .4714 12 Dodecahedron 1.4012 1.1135 20.6458 7.6631 20 Icosahedron . . . .951 .7558 86.602 2.1817 Side is length of linear edge of any side of the figure. 1. Radius of circumscribed circle = side multiplied by the number in first column corresponding to figure. 2. Radius of inscribed circle = side multiplied by the number in second column corresponding to figure. 3. Area of surface = square of side multiplied by the number in third column corresponding to figure. 4. Cubic contents = cube of side multiplied by num- ber in fourth column corresponding to figure. APPENDIX 1. 311 TABLE OF AMMONIA GAS ( SUPER-HEATED VAPOR). Temperature in Degrees F. H Is 5 10 15 20 25 30 35 40 45 Number of Cu. Ft.,v, Approximately Contained in ILb. of Gas. 15 18.81 19.05 19.20 19.48 19.68 19.87 20.06 20.25 20.544 20.74 16 17.56 17.85 18.09 18.24 18.43 18.53 18.81 18.90 19.20 19.44 17 16.60 16.70 16.96 17.08 17.28 17.48 17.66 17.85 18.09 18.31 18 15.54 15.84 15.93 16.12 16.32 16.51 16.70 16.89 17.08 17.32 19 14.78 14.97 15.16 15.36 15.45 15.64 15.84 15.93 16.13 16.36 20 14.01 14.25 14.40 14.49 14.68 14.88 14.97 15.16 15.36 15.58 21 13.34 13.53 13.63 13.82 14.01 14.11 14.30 14.40 14.59 14.80 32 12.76 12.86 13.05 13.15 13 34 13.44 13.63 13.72 13.92 14.12 23 12.19 12.28 12.48 12.57 12.76 12.86 13.05 13.15 13.34 13.54 24 11.71 11.80 11.90 12.09 13.19 12.38 12.48 12.57 13.76 12.96 25 11.33 11.34 11.42 11.61 11.71 11.80 11.90 12.09 12.19 12.38 26 10.75 10.84 11.04 11.13 11.33 11.32 11.52 11.61 11.71 11.85 27 10.36 10.46 10.56 10.75 10.84 10.94 11.04 11.23 11.32 11.45 28 9.98 10.08 10.17 10.36 10.46 10.56 10.65 10.75 10.84 10.94 29 9.60 9.69 9.79 9.98 10.08 10.17 10.27 10.36 10.46 10.57 30 9.2120 9.30 10.46 9.60 9.69 9.79 9.98 10.08 10.17 10.27 31 8.84 9.12 9.21 9.31 9.40 9.50 .9.60 9.69 9.80 9.91 32 8.83 8.93 9.02 9.13 9.21 . 9.31 9.40 9.50 9.61 33 8.54 8.64 8.73 8.83 8.91 9.02 9.11 9.21 9.31 34 8.25 9.35 8.49 8.54 8.64 8.73 8.83 8.92 9.02 35 8.16 8.35 8.35 8.44 8.54 8.64 8.64 8.75 36 7.87 7.96 8.06 8.16 8.26 8.35 8.44 8.55 37" 7.68 7.67 7.87 7.96 8.06 8.16 8.26 8.36 38 7.48 7.58 7.68 7.77 7.77 7.87 7.96 8.05 39 7.39 7.48 7.48 7.58 7.68 7.77 7.87 40 7.20 7.39 7.39 7.39 7.48 7.58 7.68 41 7.00 7.10 7.20 7.30 7.29 7.39 7.49 42 6.81 6.91 7.00 7.10 7.10 7.20 7.30 43 6.72 6.81 6.91 7.00 7.08 7.16 44 6.52 6.62 6.72 6.81 6.91 7.10 45 6.43 6.52 6.62 6.62 6.72 6.82 312 MECHANICAL REFRIGERATION. SQUARE BOOTS AND CUBE ROOTS OF NUMBERS. FROM 1 TO 20. No Sq. Cube. Sq. Rt C.Rt No Sq. Rt C.Rt No Sq. Rt C.Rt. .1 .01 .001 .316 .464 4 2.098 1.639 f 3.240 2.189 .15 .023 .003 .387 .531 f 2.121 1.651 .( 3.256 2.197 .2 .04 .008 .447 .585 J 2.145 1.663 .7 3.271 2.204 .25 .063 .016 .500 .630 | 2.168 1.675 .8 3.286 2.211 .3 .09 .027 .548 .669 !8 2.191 1.687 .9 3.302 2.217 .35 .123 .043 .592 .705 .9 2.214 1.699 11.0 3.317 2.224 .4 .16 .064 .633 .737 5.0 2.236 1.710 .1 3.332 2.231 .45 .203 .091 .671 .766 _] 2.258 1.721 f 3.347 2.237 .5 .25 .125 .707 .794 9 2.280 1.733 c .t 3.362 2.244 .55 .303 .166 .742 .819 .1 2.302 1.744 .4 3.376 2.251 .6 .36 .216 .775 .843 ^4 2.324 1.754 g 3.391 2.257 .65 .423 .275 .806 .866 *r 2.345 1.765 .'e 3.406 2.264 .7 .49 .343 .837 .888 '.I 2.366 1.776 _7 3.421 2.270 .75 .563 .422 .866 .909 .7 2. 888 1.786 .8 3.435 2.277 .8 .64 .512 .894 .928 .8 2.408 1.797 .9 3.450 2.283 .85 .723 .614 .922 .947 .9 2.429 1.807 12.0 3.464 2.289 .9 .81 .729 .949 .965 6.0 2.450 1.817 .1 3.479 2.296 .95 .903 .857 .975 .983 .1 2.470 1.827 .2 3.493 2.302 1. 1.000 .000 1.000 1.000 .2 2.490 1.837 .3 3.507 2.308 .05 1.103 .158 1.025 1.016 .3 2.510 1.847 .4 3.521 2.315 1.1 1.210 .331 1.049 1.032 .4 2.530 1.857 .5 3.536 2.321 .15 1.323 .521 .072 1.048 .5 2.550 1.866 .6 3.550 2.327 1.2 1.440 : .728 .095 1.063 .6 2.569 1.876 fV 3.564 2.333 .25 1.563 .953 .118 1.077 .7 2.588 1.885 !a 3.578 2.339 .3 1.690 2.197 .140 1.091 .8 2.608 1.895 .9 3.592 2.345 1.35 1.823 2.460 : .162 .105 .9 2.627 1.904 13.0 3.606 2.351 1.4 1.960 3.744 : .183 .119 7.0 2.646 1.913 .2 3.633 2.363 .45 2.103 3.049 1.204 1.132 .1 2.665 1.922 .4 3.661 2.375 1.5 2.250 3.375 1.225 1.145 2 2.683 1.931 .6 3.688 2.387 .55 2.403 3.724 1.245 1.157 '.3 2.702 .940 .8 3.715 2.399 1.6 2.560 4.096 1.265 1.170 .4 2.720 1.949 14.0 3.742 2.410 .65 2.723 4.492 1.285 1.182 .5 2.739 1.957 .2 3.768 2.422 1.7 2.890 4.913 1.304 1.194 .6 2.757 1.960 .4 3.795 2.433 .75 3.063 5.359 1.323 1.205 .7 2.775 1.975 .6 3.821 2.444 1.8 3.240 5.832 1.342 .216 .8 2.793 1.983 .8 3 '.847 2.455 .85 3.423 6.332 1.360 1.228 .9 2.811 1.992 5.0 3.873 2.466 1.9 3.610 6.859 1.378 1.239 8.0 2.828 2.000 .2 3.899 2.477 .95 3.803 7.415 1.396 .249 .1 2.846 2.008 .4 3.924 2.488 2.0 4.000 8 000 1.414 1.260 .2 2.864 2.017 .6 3.950 2.499 .1 4.410 9.261 1.449 1.281 .3 2.881 2.025 .8 3.975 2.509 .2 4.840 10.65 1.483 .301 .4 2.898 2.033 16.0 4.000 2.520 .3 5.290 12.17 1.517 1.320 .5 2.916 2.041 .2 4.025 2.530 .4 5.760 13.82 1.549 1.339 .6 2.933 2.049 .4 4.050 2.541 .5 6.250 15.63 1.581 1.357 .7 2.950 3.057 .6 4.074 2.551 .6 6.760 17.58 1.613 1.375 .8 2.967 2.065 .8 4.099 2.561 .7 7.290 19.68 1.643 1.393 .9 2.983 2.072 17.0 4.123 2.571 .8 7.840 21.95 1.673 1.409 9.0 3.000 2.080 .2 4.147 2.581 .9 8.410 24.39 1.703 1.426 .1 3.017 2.088 .4 4.171 2.591 3.0 9.00 27.00 1.732 1.442 .2 3.033 2.095 .6 4.195 2.601 .1 9.61 29.79 1.761 1.458 .3 3.050 2.103 .8 4.219 2.611 .2 0.24 32.77 1.789 1.474 .4 3.066 2.111 18.0 4.243 2.621 .3 10.89 35.94 1.817 1.489 .5 3.08-2 2.118 .2 4.266 2.630 .4 1.56 39.30 1.844 .504 .6 3.098 2.125 .4 4.290 2.640 .5 12.25 42.88 1.871 1.518 .7 3.115 2.133 .6 4.313 2.650 .6 2.96 46.66 1.897 1.533 .8 3.131 2.140 .8 4.336 2.659 .7 13.69 50.65 1.924 1.547 .9 3.146 2.147 19.0 4.359 2.668 .8 14.44 54.87 1.949 1.561 10.0 3.162 2.154 .2 4.382 2.678 .9 ,15.21 59.32 1.975 1.574 .1 3.178 2.16J .4 4.405 2.687 4.0 16.00 64.00 2.000 1.587 .2 3.194 2.169 .6 4.427 2.696 .1 16.81 68.92 2.025 1.601 .3 3.209 2.177 .8 4.450 2.705 .2 17.64 74.09 2.049 1.613 .4 3.225 2.183 20.0 4.472 2.714 .3 18.49 79.51 2.074 1.626 APPENDIX I. 313 TABLE OF SQUARES, CUBES, SQUARE ROOTS AND CUBE ROOTS OF NUMBERS FROM 1 TO 100. No. 8 Cube. Sq. Rt. C. Rt. No. e s3 1 Cube. Sq. Rt. C.Rt. 1 i 1 1.0000 1.0000 51 2601 132651 7.1414 3.7084 2 4 8 1.4142 1.2599 52 2704 140608 7.2111 3.7325 3 9 27 1.7321 1.4422 53 2809 148877 7.2801 3.7563 4 16 64 2.0000 1.5874 54 2916 157464 7.3485 3.7798 5 25 125 2.2361 1.7100 55 3025 166375 7.4162 3.8030 6 36 216 2.4495 1. 8171 56 3136 175616 7.4833 3.8259 7 49 343 2.6458 1.9129 57 3249 185193 7.5498 3.8485 8 61 512 2.8284 2.0000 58 3364 195112 7.6158 3.8709 9 8J 729 3.0000 2.0801 59 3181 205379 7.6811 3.8930 10 100 1000 3.1623 2.1544 60 3600 216000 7.7460 3.9149 11 121 1331 3.3166 2.2240 61 3721 226981 7.8102 3.9365 12 144 1728 3.4641 2.2894 62 3844 238328 7.8740 3.9579 13 169 2197 3.6056 2.3513 63 3969 250047 7.9373 3.9791 14 196 2744 3.7417 2.4101 64 4096 262144 8.0000 4.0000 IB 225 3375 3.8730 2.4662 66 4225 274625 8.0623 4.0207 16 256 4096 4.0000 2.5198 66 4356 287496 8.1240 4.0412 17 289 4913 4.1231 2.5713 67 4489 300764 8.1854 4.0615 18 324 5832 4.2426 2.6207 68 4624 314432 8.2462 4.0817 19 361 6859 4.3589 2.6684 69 4761 328509 8.3066 4.1016 20 400 8000 4.4721 2.7144 70 4900 343000 8.3666 4.1213 21 441 9261 4.5826 2.7589 71 5041 357911 8.4261 4.1408 22 484 10648 4.6904 2.8020 72 5184 373248 8.4853 4.1602 23 529 12167 4.7958 2.8429 73 5329 ^89017 8.5440 4. 1793 24 576 13824 4.8990 2.8845 74 5476 405224 8.6023 4.1983 25 625 15625 5.0000 2.9240 75 5625 421875 8.6603 4.2172 26 676 17576 5.0990 2.9625 76 5766 438976 8.7178 4.2358 27 729 19683 5.1962 3.0000 77 5929 456533 8.7750 4.2543 28 784 21952 5.2915 3.0366 78 6084 474552 8.8318 4 2727 29 841 24389 5.3852 3.0723 79 6241 493039 8.8882 4. '2908 30 900 27000 5.4772 3.1072 80 6400 512000 8.9443 4.3089 31 961 29791 5.5678 3.1414 81 6561 531441 9.0000 4.3267 32 1024 32768 5.6569 3.1748 82 6724 551368 9.0554 4.3445 33 1089 35937 5.7446 3.2075 83 6889 571787 9.1104 4.3621 34 1156 39304 5.8310 3.2396 84 7056 592704 9.1652 4.3795 35 1225 42875 5.9161 3.2711 85 7225 614125 9.2195 4.3968 36 1296 46656 6.0000 3.3019 86 7396 636056 9.2736 4.4140 37 1369 f0653 6.0828 3.3322 87 7569 658503 9.3274 4.4310 38 1444 54872 6.1644 3. 3620 88 7744 681472 9.3808 4.4480 39 1521 59319 6.2450 3.3912 89 7921 704969 9.4340 4.4647 40 1600 64000 6.3246 3.4200 90 8100 729000 6.4868 4.4814 41 1681 68921 6.4031 3.4482 91 8281 753571 9.5394 4.4979 42 1764 74088 6.4807 3.4760 92 8464 778688 9.5917 4.5144 43 1849 79507 6.5574 3.5034 93 8649 804357 9.6437 4.5307 44 1936 85184 6.6332 3.5303 94 8836 830584 9.6954 4.5468 45 2025 91125 6.7082 3.5569 95 9025 857375 9.7468 4.5629 46 2116 97336 6.7823 3.5830 96 9216 884736 9.7980 4.5789 47 2209 103823 6.8557 3.6088 97 9409 912673 9.8489 4.5947 48 2304 110592 6.9282 3.6342 98 9604 941192 9.8995 4.6104 49 2401 117649 7.0000 3.6563 99 9801 970299 9.9499 4.6261 50 2500 125000 7.0711 3.6840 100 10000 1000000 10.0000 4.6416 314 MECHANICAL REFRIGERATION. AREAS OF CIRCLES ADVANCING BY EIGHTHS. i S K Hi % K % * % .0 .012 .05 .11 .19 .30 .44 .60 i .785 .994 1.22 1.48 1.76 2.07 2.40 2.76 2 3.141 3.54b 3.97 4.43 4.90 5.41 5.93 6.49 3 7.068 7.669 8.29 8.94 9.62 10.32 n.04 11.79 4 12.56 13.36 14.18 15.03 15. 90 16.80 17.72 18.66 5 19.63 20.62 21.64 22.69 23.75 24.85 25.96 27.18 6 28.27 29.46 30.67 31.91 33.18 34.47 35.78 37.12 7 38.48 39. 8T 41.28 42.71 44.17 45.66 47.17 48.70 8 50.29 51.84 53.45 55.08 56.74 58.42 60.13 61.86 9 63.61 65.39 67.20 69.02 70.88 72.75 74. (i!) 76.58 10 78.54 80.51 82.51 84.54 86.59 88.66 90.76 92.88 11 95.03 97.20 99.40 101.6 103.8 106.1 108.4 110.7 12 113.0 115.4 117.8 120.2 122.7 125.1 127.6 130.1 13 132.7 135.2 137.8 140.5 143.1 145.8 148.4 151.2 14 153.9 156.6 159.4 162.2 165.1 1(57.9 170.8 173.7 15 176.7 179.6 182.6 185.6 188.6 191.7 194.8 197.9 16 201.0 204.2 207.3 210.5 213.8 217.0 220.3 223.6 17 226.9 230.3 233.7 237.1 240.5 243.9 247.4 250.9 18 254.4 258.0 261.5 265.1 268.8 272.4 276. 1 279.8 19 283.5 287.2 291.0 294.8 298.6 302.4 306.3 310.2 20 314.1 318.1 322.0 326.0 330.0 334.1 338.1 342.2 21 346.3 350.4 354.6 358.8 363.0 367.2 371.5 375.8 22 380.1 384.4 388.8 393.2 397.6 402 406.4 410.9 23 415.4 420.0 424.5 429.1 433.7 438.3 433.0 447.6 24 452.3 457.1 461.8 466.6 471.4 476.2 481.1 485.9 25 490.8 495.7 500.7 505.7 510.7 515.7 520.7 525.8 26 530.9 536.0 541.1 546.3 551.5 556.7 562.0 567.2 27 572.5 577.8 583.2 588.5 593. 9 599.3 604.8 610.2 28 615.7 621.2 626.7 632.3 637.9 643.5 649.1 1154.8 29 660.5 666.2 671.9 677.7 683.4 689.2 695.1 700.9 30 706.8 712.7 718.6 724.6 730.6 736.6 742.6 748.6 31 754.8 760.9 767.9 773.1 779.3 785.5 791.7 798.0 32 804.3 810.6 816.9 823.2 829.6 836.0 842.4 848.8 33 855.3 861.8 868.3 874.9 881.4 888.0 894.6 1)01.3 34 907.9 914.7 921.3 928.1 934.8 941.6 948.4 955.3 35 962.1 969.0 975.9 982.8 989.8 996.8 1003.8 010.8 36 017.9 025.0 032.1 1039.2 046.3 053.5 1060.7 068.0 37 075.2 082.5 089.8 097.1 104.5 111.8 1119.2 126.9 38 134.1 141.6 149.1 156.6 164.2 171.7 1179.3 186.7 39 194.6 202.3 210.0 217.7 225.4 233.2 1241.0 248.8 40 256.6 264.5 272.4 1280.3 288.2 296.2 1304.2 312.2 41 320.3 328.3 336.4 1344.5 352.7 360.8 1369 377.2 42 385.4 393.7 402.0 410.3 418.6 1427.0 1435.4 443.8 43 452.2 460.7 469.1 1477.6 486.2 1494.7 1503.3 511. 9 44 520.5 529.2 1537.9 1546.6 555.3 564.0 1572.8 1581.6 45 590.4 599.3 1608.2 1617.0 626.0 1634.9 1643.9 1652.9 EQUIVALENTS OF FRACTIONS OF AN INCH. Fractions of an Inch. Decimals of Foot. Fractions of an Inch. Decimals of Foot. % i * .0104 .0208- .0313 .0417 % '\ .0521 .0625 .0729 .0833 APPENDIX I. TABLE OF LOGARITHMS. 315 13' 11394 14613 3 - 00000 30103 47712 60206 6989 10 00000 00432 00860 01283 01703 11 04139 04532:04921 05307 05690 13 07918 08278 08636 08990 09342 11727 12057i 12385 12710 14922 15228! 15533 15836 1 ^ 18 184 18469] 18752 13 17609J 17891 16 20412 20682 20951J21218|21484 17 23045 ! 23299 23552 23804 24054 18 25527 25767 26007 26245 26481 19 27875|28103 28330128555 28780 . 2Q 30103 30319 30535130749130963 31175l8138fflS159 19590 19865120139 281 21748J22010 22271 22531 1 22788 264) 24303;24551 26717126951 29003 29225 29446;29666i29885 222 "97j31806;32014 212 33243 33445133646 33845134044 202 22 34242 34439 34635 34830 35024 35218 354101 35602 35793 35983 193 25(39794 39967 40140 40312 40483 40654 40824 40993 4118241830 170 26 41497 41664 41830 41995 42160 42324|42488 42651 27 43136 4B297 43457 43616 43775 43933 44091 2844716 44870 45025 45178 45331 45484 45636 45788 45939,46089 153 29 46239 46389 46538 46686 46834 30 47712 47856 480.00 48144 48287 31 49136 49276 49415 49544 49693 49831 32 50515 50650 50785 41 3~2222J32428[32633 32838 33041 3617236361 38021 38201 36548 36735 36921 38381 33 51851 51982 52113 52244 52374 34 53148 53275 53402 53529 53655 38560 38739 38916 39093 39269 39445139619 35 54406 54530 54654 54777 36 55630 55750|55870 55990 50920 51054 54900 56110 56820156987157054 57170 57287 57403) 57978 58092 58206 58319 58433 KOKAO] 59106 59217 59328 59439 59549 80208160314 60422 6030 61278 6i~38461489;6i595;61700 ! >325 I 62428!62531 ',62634:62736 43 6 43 63346 1 63447;63548 I 63648!63749 63849 63948 64048 64147 J64246 3 I 64542 1 64640 64738 64836 64933 65030 65127|65224 44 64345 6444 45 65321 ! 65417'65513'65609:65705 46 66275 66370 ! 66464j66558l66651 66745 66838166931 67669 67760 67.851 68574 68663 68752 68842: 68931 69460 69548 69635 69723:69810 70329 70415 70500|70586|70671 47 67209 67302 67894 67488 6757 1 ! 48 68124'68214 ! 68304;68894:68484 49 69019169108:69106 69284 ! 69372 50 69897 ! 69983 I 70070 70156|70243 51 70757 ! 70842i 70927 71011171096 71180J71265 71349 71433171516 52 71600171683 71767 71850 71933 mRi79na 79,ifti TO9ft3f725UR 53 72427 72509 72591 72672 72754 54 78239 73319 73999 73480 73560 55 74036 74115 74194 74272 74351 56 74818 74896 7497375050 75128 75204 75281 57 75587 75663i75739|75815 75891 58 76342 76417 76492 76666 76641 59 77085 77168 77382 77806 77378 60 77815 77887J77959J78031J78103 6 13033,13353 16136:16435 1903319312 7 77815 84510 90309 95424 02119 02530 02938 03342 03742 415 06069 06445 06818 07188 07554 379 09691 10037 10380 10721 11059 344 13672 16731 13987,14301 1702617318 323 298 247972504225285249 27184 27415!27646 234 37106 37291 37474 37657;37839 185 ' i 4281342975164 44248 44404 44560 46982 47129 47275 47421 47567 148 48430 48572|487l3j48855 48995 143 '49968 I 50106I50242!50379 138 51188'51321 52504:52634 51454151587151719134 52763J52891J53020 130 53782!53907 54033 54158j54282 126 55022 ! 55145 55206 55388155509 122 -)6229'56348 56466 56584 ; 56702 119 '57518J57634 57749J57863 116 58546158658 58771 58883 5 59659 69769 59879 59988 60097 60638 60745!60852 60959 6J06616117 61804 61909 62013|62ll7l62221 ... 6283862941 63042J63144J63245 102 65801 72835 73639 74429 65896J65891 66086,6.6181 6702467117 6794268033 '2916 '4507 759607604276117 76715 77451 78175 78247 72997 73078|73158 73639 73719 73798 73878 73957 1/t/inpi ?/tRA'? "?yiaQe; 7/lftflQ 7/17/11 4585 74663J 74741 753587543475511 7619276267 76789 76863 76937 77011 77524 77597J77670 77742 78318:78390178461 177 170 164 158 110 107 104 2107 316 MECHANICAL REFRIGERATION. TABLE OF LOGARITHMS. 1 1 2 3 4 5 6 7 8 9 i cu 61 78533 78604 78675 78746 78816 78887 78958 79028 79098 79169 71 62 79239 79309 79379 7944879518 79588 79657 79726 79796 79865 70 63 79934 80003l8007l'80l40 80208 80277 80345 80414 80482 80550 69 64 80618 80685 180753 8082 1180888 80956 81023 810908115781224 68 65 81291181358 81424'81491 81557 81624 81690 81756 81822181888 67 66 67 68 8195482020 82607 82672 83251 18331 4 820858215182216 82737 82801 82866 83378 83442 83505 82282 82930 83569 82347 82994 83632 82412 83058 83695 82477182542 83123 83187 83758:83822 66 64 63 69 70 83885,83947 84010 84073 84136 84509.84571 8463384695184757 84198 84819 84261 84880 84323 84385 84447 84942 85003] 85064 6 62 71 85125 85187 85248 85309 85369 85430 85491 85552^85612 85673 61 72 85733 85793 86853 85913 85973 86033 86= 1 METRE 1,000 millimetres j 10 metres = 1 decametre 10 decametres = 1 hectometre 10 hectometres = 1 KILOMETRE 10 kilometres = 1 myriametre A table of METRIC MEASURES OF SURFACE is obtained from the foregoing table by squaring the numbers, and placing the word "square" before each of the names; thus, 100 square millimetres^ 1 square centimetre. And A TABLE FOR VOLUMES is obtained by cubing the numbers, and placing the word ''cubic" before the names; thus, 1,000 cubic millimetres = 1 cubic centimetre. FOR MEASURES OF CAPACITY the unit is the litre, and the table is 10 centilitres = 1 decilitre 10 decilitres = 1 LITRE 10 litres = 1 decalitre and a litre contains 1 cubic decimetre. This portion of the capacity table belongs especially to the measurement of liquids. FOR DRY MEASURES the table is contained ana we have 10 litres = 1 decalitre 10 decalitres or 100 litres = 1 hectolitre 10 hectolitres or 1,000 litres = 1 kilolitre = 1 cu. metre. METRIC MEASURES OF WEIGHT. 10 milligrames = 1 centigramme 10 centigrammes =1 decigramme 10 decigrammes =1 GRAMME 10 grammes = 1 decagramme 10 decagrammes = 1 hectogramme 10 hectogrammes or 1,000 grammes . = 1 KILOGRAMME 10 kilogrammes = 1 myriagramme = 1 quintal metrigue A millier or tonne is the weight of 1 cubic metre of water at 39.1 F. APPROXIMATE EQUIVALENTS OF FRENCH AND ENGLISH MEASURES. 1 inch ................................ 25 millimeters (exactly 25.1). 1 yard ................................ 11-12 meter. 1 kilometer ......................... % mile. 1 mile ............ ..................... 1.6 or 1 3-5 kilometers. 1 square yard ........................ 6-7 square meter. 1 acre ............................... 4,000 square meters. 1 gallon .............................. 4 1 / 2 liters fully. 1 cubic foot .......................... 28.3 liters. 1 cubic meter of water .............. 1 ton nearly.* 1 gramme . , .......................... 15 l / grains nearly. 1 kilogramme ...................... 2.2 pounds fully. SPECIFIC GRAVITY AND WEIGHT OF MATERIALS. METALS. Specific Weight Cu. ft. in Gravity. per cu. ft. one ton- Aluminum ........................... 2.6. 162 13.3 Antimony, cast, 6.66 to 6.74 .......... 6.7 418 6.3 Bismuth, cast and native ...... .. 9.74 607 3.6 Brass, copper and zinc, cast 7.8 to 8.4 .............................. 8.1 504 4.4 Brass, rolled ......................... 8.4 524 4.2 Bronze, copper, 8, and tin, 1; gun metal, 8.4 to 8.6 ................. 8.5 529 4.2 Copper, cast, 8. 6 to 8. 8 .............. 8.7 542 4.1 Copper, rolled, 8.7 to 8.9 ......... ... 8.8 549 4.0 320 MECHANICAL REFRIGERATION. METALS CONTINUED. Specific Weight Cu. ft. in Gravity, percu.ft. one ton. Gold, cast, pure or 24 carat 19 . 258 1204 1 . 86 Iron, cast, 6. 9 to 7.4 7.21 450 4.8 " wrought, 7.0 to 7.9 7.77 485 4.6 " large rolled bars 7.69 480 4.6 " sheet 485 4.6 Lead 11.4 712 3.15 Mercury at 32 F 13.62 849 2.6 " 00F 13.58 846 2.6 "212F... 13.38 836 2.6 Platinum, 21 to 22 21.5 1,342 1.6 Silver 10.5 655 3.4 Steel, crucible, average 7.842 489 4.5 " cast, 7.848 489.3 4.5 " Bessemer 7.852 489.6 4.5 Spelter or zinc, 6. 8 to 7. 2 7.00 437.5 5.1 Tin, cast, 7. 2 to 7. 5 7.35 459. 4.8 Type metal. 10.45 653. 3.4 WOODS. Ash, perfectly dry 752 47. 1.748 Ash, American white, dry 61 38 1.414 Chestnut, perfectly dry 66 41 1.525 Elm " 56 35 1.303 Hemlock " " 40 25. .930 Hickory " " 85 53 1.971 Maple, dry 79 49 Oak,live,dry 5 59.3 " white.dry 70 44 " red 32to45 Pine, white 40 25 .930 Pine, yellow, southern 72 45 1.674 Sycamore, perfectly dry .59 37 1.370 Spruce, ' 40 25 .930 STONES AND MINERALS. Granite, syenite, gneiss 2. 36 to 2. 96 147.1 to 184. 6 12.1 gray 2.80to3.06 174.6tol90.8 11.8 Graphite 2.20 137.2 16.3 Gypsum, plaster of Paris 2.27 141.6 15.8 " in irregular lumps 82 Greenstone, trap, 2. 8 to 3. 2 3. 187 Limestones and marbles, 2. 4 to 2. 86 2.6 164.4 13.6 Limestones and marbles, they are frequently 2.7 168.0 13.3 Quicklime, ground, loose, per struck bushel, 62 to 70 Ibs 53 42. a Quartz, common, finely pulverized, loose 90 24.8 Sand, with its natural moisture and loose .85 to .90 24.8 Sand, pure, quartz, perfectly dry.. 1.7 106 Sand, perfectly wet, voids full of water 118tol29 17.3 Sandstones, fit for building, dry, 2.1to2.73'. 2.41 150. Standstones, quarried and piled. One measure, solid, makes 1% piled 86 26. Serpentines 2.81 175.2 12.8 Shales, red or black, 2.4 to 2.8 2.6 162 " quarried in piles 92 24.3 Slate, 2.7 to 2.9 2.8 175 12.8 Soapstone or steatite, 2.65 to 2.8.... 2.73 170 13.1 Air, atmosphere at 60 F., Barom. 30" 00123 .0765 Alcohol, pure 793 49.43 " of commerce 834 52.10 proof spirit 916 57.2 Alabaster, a compact plaster of Paris . 2.31 144.0 APPENDIX I. 321 STONES AND MINERALS CONTINUED. Specific Weight Cu. ft. in Gravity, percu. ft. gross ton. Anthracite, solid, 1.3 to 1.84, average 1.50 93.5 Asphaltum 1.4 87.3 25.6 Carbonic acid gas, 1 L / Z times as heavy as air 00187 Charcoal of pines and oaks 15 to 30 74.6 Clay, potters', dry, 1.8 to 2.1 1.9 119 18.8 Coke, loose, of good coal 23 to 32 Cement, English, Portland 1.25 to 1.51 78 to 92 23.8 to 28.7 Cork 25 15.6 Cork (comminuted) 6.0 Earth, common loam, perfectly dry, shaken moderately 82 to 92 Earth, common loam, more moist, packed 90 to 100 Earth, common loam, as a soft flow- ing mud 104 to 112 Fat 93 58 Glass, 2.5 to 3.45 2.98 186 Gutta percha 98 61.1 Hydrogen gas is 14.5 times lighter than air and 16 times lighter than oxygen .00527 Ice,at32P 92 57.5 38.9 India rubber 1 93 58 Lard ." 95 59.3 Masonry, of granite or limestones, well dressed 165 13.57 Masonry, of brickwork, pressed brick, fine joints, 140 16. Masonry, of brickwork, coarse, soft bricks 100 22.4 Mortar, hardened, 1.4 to 1.9 1.65 103 Naphtha 848 52.9 Nitrogen gas is about 1-35 part lighter than air .0744 Oils, whale, olive .92 57.3 Oxygen gas, a little more than 1-10 heavier than air 00136 .0846 Petroleum 878 54.8 40.87 Pitch 1.15 71.7 Rosin 1.1 68.6 32.65 Salt, coarse, per struck bushel, Syracuse, N. Y., 56 Ibs 45. 49.77 Salt, coarse, per struck bushel, St. Barts, 84 to 90 70. 32. Salt, coarse, per struck bushel, well dried, W. I. 90 to 96 74 Sand 90 to 106 Snow, fresh fallen 5 to 12 " moistened and compacted by rain 15 to 50 Sulphur 2 125 Tallow .94 58.6 Tar 1. 62.4 *Water, pure rain, or distilled, dt 32P.Barom. 30" 62.416 60 F. " " 1. 62.366 35.918 80 F. " 62.217 Water, sea, 1.026 to 1.030 1.028 64.08 34.96 Wax, bees 97 60.5 Gypsum, plaster of Paris 2.27 141.6 15.8 " in irregular lumps 82. Gas (natural) 0.0316 Limestones and marbles, 2.4 to2. 86. 2.6 164.4 13.6 they are frequently 2.7 168.0 13.3 Lime-quick, ground, loose, per struck bushel, 62 to 70 pounds. . 53. 42.2 Quartz, common, finely pulverized, loose 90. 24.1'- 322 MECHANICAL REFRIGERATION. TABLE OF CONTENTS IN CUB. FEET AND IN U. 8. GALLON, (From Trautwine.) Of 231 cubic inches (or 7.4805 gallons to a cubic foot); and for one foot of length of the cylinder. For the contents for a greater diameter than any in the table, take the quantity opposite one-half said diameter and multiply it by 4. Thus, the number of cubic feet in one foot length of a pipe eighty inches in diameter is equal to 8.728X4=34.912 cub. ft. So also with gallons and areas. 3 FOB 1 FOOT 3 FOB 1 FOOT IN LENGTH. CsS IN LENGTH. Diamete sr J>H ^fl^ M Diamete r ID'H ^.2+3 * . in m C3 S fl in "S C3 flj O Inches |j Cubic f< Also are square f Gallons 231 cub. : Inches If 5-1 o III 1 &. .0208 .0003 .0026 y .6625 .2485 1.859 5-16. .0260 .0005 .0040 7. 4 ! .5833 .2673 1.999 .0313 .0008 .9057 k. .6042 .2868 2.144 7-16 ! .0365 .0010 .0078 YZ. .6250 .3068 2.295 J4. .0417 .0014 .0102 K .6458 .3275 2.450 9-16. .0469 .0017 .0129 8. . .6667 .3490 2.611 .0521 .0021 .9159 M .6875 .3713 2.777 11-16' .0573 .0026 .0193 Yz* .7083 .3940 2.948 %- .0626 .0031 .0230 K. .7292 .4175 3.125 13-16. .0677 .0036 .0270 9. . .7500 .4418 3.305 .0729 .0042 .0312 /4 .7708 .4668 3.492 15-16'. .0781 .0048 .0359 Yz' .7917 .4923 3.682 1. .0833 .0065 .0408 K. .8125 .6185 3.879 .1042 .0085 .0638 10. . .8333 .5455 4.081 Yz'- .1250 .0123 .0918 k. .8542 .5730 4.286 %. .1458 .0168 .1250 g. .8750 .6013 4.498 2. '. .1667 .0218 .1632 .8958 -.6303 4.714 1876 .0276 .2066 11. 4 ! 9167 6600 4.937 Yz- !2083 .0341 .2550 .9375 .6903 5.163 .2292 .0413 .3086 Yz'- .9583 .7213 5.395 3. .2500 .0491 .3673 2. .9792 .7530 5.633 k. .2708 .0576 .4310 12. . IPoot .7854 5.876 .2917 .06H8 .4998 Yz. 1.042 .8523 6.375 %" .3125 .0767 .5738 13. . 1.083 .9218 6.895 4. ! .3333 .0873 .6528 1.125 .9940 7.435 .3542 .0985 .7370 14. *! 1.167 1.069 7.997 i' .3750 .3958 .1105 .3531 .8263 .9205 .208 .250 1.147 1.227 8.578 9.180 5. ! .4167 .1364 1.020 'YZ. .292 1.310 9.801 |: .4375 .4583 .1503 .1650 1.124 1.234 16^ . .333 .375 1.396 1.485 10.44 11.11 .4792 .1803 1.349 IT. ; .417 1.676 11.79 6. *! .5000 .1963 1.469 .458 1.670 12.50 8: .5208 .5417 .2130 .2305 1.594 1.724 i8.^; .500 .542 1.767 1.867 13.22 13.97 TABLE OF GALLONS. Cubic inch, in a gallon. Weight of a gallon in pounds avoirdupois. Gallons in a cubic foot. Weight of a cubic foot of water, Eng- lish standard, 62.3210286 Ibs. avoirdupois. United States. New York.... Imperial 231. 231.81918 277.274 8.33111 8.00 10.00 7.480519 7.901285 6.232102 APPENDIX I. 323 COMPARISON OF WEIGHTS AND MEASURES. METRIC SYSTEM. LENGTH. 1 millimeter = .0394 inches. 1 centimeter = .3937 inches. 1 METER 39.3708 inches. 1 kilometer = .6214 miles. SQUARE. 1 sq. centimeter = .1549 sq. in. 1 sq. meter = 10.7631 sq. ft. 1 ARE = 119.5894 sq.yds. 1 hectare = 2.4711 acres. CUBIC. 1 CUBIC METER 35.3166 cubic ft. WEIGHT. 1 gram = 15.4323 grains. 1 KILOGRAM = 2.2046 Ibs. 1 tonneau = 2204.55 Ibs. DRY MEASURE. 1 centiliter = .0181 pints. 1 LITER = .908 quarts. 1 hectoliter = 2.837 bushels. LIQUID MEASURE. 1 centiliter = .0211 pints. 1 LITER = 1.0567 quarts. 1 hectoliter = 26.4176 gallons. U. S. STANDARD. LENGTH. 1 inch = 2.5309 centimeters. 1 foot = 30.4794 centimeters. 1 yard = .9143 meters. 1 m iie = 1.6093 kilometers. SQUARE. 1 sq. in. = 6.4513 sq. centimeters. 1 sq. ft. = .0929 sq.' meters. 1 sq. yd. = .8361 sq. meters. 1 acre = .4047 hectares. CUBIC. 1 cubic foot = .02831 cubic meters WEIGHT. 1 Ib. = .4536 kilos. 1 cwt. 50.8024 kilos. 1 ton = 1016.0483 kilos. DRY MEASURE. 1 pint = 55.0661 centiliters. 1 quart = 1.1013 liters. 1 bushel = 35.2416 liters. LIQUID MEASURE. 1 pint = 47.3171 centiliters. 1 quart = .9563 liters. 1 gallon = 3.7854 liters. COMPARISON OF ALCOHOLOMETERS. In the absence of a specific gravity or Beaume scale, an alcoholometer may also be used for ascertaining the strength of ammonia liquor. The accompanying table is to be used in connection with the table on page 97 for this purpose. Specific gravity. Per cent Tralles (by volume). Per cent Rich- ter (by weight). Per cent Gen- dar United States. 0.793 100 100 100 0.815 95 91.5 90 0.832 90 85 80 0.848 85 79.1 70 0.863 80 74.2 60 0.876 75 68.4' 50 0.889 70 62.5 40 0.901 65 57.3 30 0.912 60 51.7* 20 0.923 55 46.5 10 0.933 50 42.0 P 0.942 45 37.7 10 0.951 40 33.0 20 0.958 35 28.7 30 964 30 24.4 40 0.970 25 20.2 50 0.975 20 16.4 60 0.980 15 13.0 70 0.985 10 10 4 80 0.991 5 60 90 0.999 1.0 100 P in the last column stands for proof spirits. Percentage over proof U. S. gendar scale can be converted into per cent Tralles by dividing by two and adding fifty. Degrees below proof are con- verted by dividing by two and subtracting from fifty. 324 MECHANICAL REFRIGERATION. HORSE POWER OF BELTING. TABLE FOR SINGLE LEATHER, 4-PLY RUBBER AND 4- PLY COTTON BELTING, BELTS NOT OVERLOADED. (ONE INOH WIDE, 800 FEET PER MINUTE = I-HORSE POWER.) Speed in Ft. Per Minute. WIDTH OF BELTS IN INCHES. 2 3 4 5 6 8 10 12 14 | 16 18 20 h.p h.p h.p h.p h.p h~p~ h.p h.p h.p h.p h.p. h.p. 400 1 14 2 24 3 4 5 6 7 8 9 10 600 14 2J4 3 3* 44 6 74 9 104 12 134 15 800 24 3 4 5 6 8 10 12 14 16 18 20 1,000 2 3% 5 6!< 74 10 124 15 174 20 224 25 1,200 3 44 6 74 9 12 15 18 21 24 27 30 1,500 3% 5% 74 94 114 15 18% 224 264 30 33% 374 1,800 4% QH 9 llfc 134 18 224 27 314 36 404 45 2,000 5 74 10 124 15 20 25 30 35 40 45 50 2,400 6 9 12 15 18 24 30 36 42 48 54 60 2,800 7 104 14 174 21 28 35 42 49 56 63 70 3,000 74 1154 15 18% 224 30 374 45 624 60 674 75 3,500 13 17-4 22 26 35 44 524 61 70 79 88 4,000 10 4 15 20 25 30 40 50 60 70 80 90 100 4,600 11J4 17 224 28 34 45 57 69 78 90 102 114 5,000 12/2 19 25 31 374 50 624 75 874 100 112 125 Double leather, 6-ply rubber or 6-ply cotton belting will transmit 50 to 75 per cent more power than is shown in this table. A simple rule for ascertaining transmitting power of belting, without first computing speed per minute that it travels, is as follows: Multiply diameter of pulley in inches by its number of revolutions per minute, and this product by width of the belt in inches; divide this prod- uct by 3,300 for single belting, or by 2,100 for double belting, and the quotient will be the amount of horse power that can be safely transmitted. HORSE POWER OF SHAFTING. Diameter of Shaft REVOLUTIONS PER MINUTE. in Inches. 100 125 150 175 200 h.p. h.p. h.p. h.p. h.p. 1516 1.2 1.4 1.7 2.1 2.4 1 316 2.4 3.1 3.7 4.3 4.9 1 7-16 4.3 5.3 6.4 7.4 8.5 1 11-16 6.7 8.4 10.1 11.7 13.4 1 15-16 10.0 12.5 15.0 17.5 20.0 2 3-16 14.3 17.8 21.4 24.9 28.5 2 7-16 19.5 24.4 29.3 34.1 39.0 2 11-16 26.0 32.5 39.0 43.5 52.0 2 15-16 33.8 42.2 50.6 59.1 67.5 3 3-16 43.0 - 53.6 64.4 75.1 a r ).8 3 7-16 53.6 67.0 79.4 93.8 107.2 3 11-16 65.9 82.4 97.9 115.4 121.8 3 15-16 80.0 100.0 120.0 140.0 160.0 4 7-16 113.9 142.4 170.8 199.8 *27.8 4 15-16 156.3 195.3 234.4 273.4 312.5 APPENDIX I. 325 iis 61 O CO CO OS CO CD C5 (M CO Cl sgg CM CO 05 * co T-J o J CO O ^ CO 91 O t- N CM * Csl O5 t- cISSS 11188 OO t- t- t- CO CO M5 U5 kO * * CO CO CO CO OJ "# O O CM O CO lO 1-4 CO OS * O H5 -l siig 8T 111 21 Mill Tl sills 01 CO t- O> O OS O S CO t- oo o o r-i CO CM CM T-1 O o os co oo t- t- GO Ol i I CM ^* >O CO CO 22 2 O t- CO O t- CO O t- CO CO OrH CO CO T-H COtOOi l-lrlrll-t 8pnnos rl ^a* |i s|l 0o *3 O O 8 r f & 1*. ||| 111 ill O C\ r * > fsl fs! 6* Q < Pbl PM o tfl > > j* 5 p 40 420.66 1539.90 10.69 4.01 579.67 24.388 .02348 .0410 43.589 40 39 1 1584.43 11.00 3.70 579.07 33.735 .02351 .0421 42.535 39 38 2 1630.03 11.32 3.38 578.42 23.103 .02354 .0433 42.483 38 37 3 1676.71 11.64 3.06 577.88 33.488 .02357 .0444 42.427 37 36 4 1724.51 11.98 2.73 577.27 21.895 .02359 .0457 42.391 36 36 425.66 1773.43 12.31 2.39 576.68 31.331 .02362 .0469 42.337 35 34 6 1823.50 12.66 2.04 576.08 30.763 .02364 .0482 42.301 34 33 7 1874.73 13.02 1.68 575.48 20.321 .02366 .0495 42.265 33 32 8 1927.17 13.38 1.32 574.89 19.708 .02368 .0507 42.213 33 31 9 1980.78 13.75 0.95 574.39 19.304 .02371 .0521 42.176 31 30 430.66 2035.69 14.13 0.57 573.69 18.693 .02374 .0535 42.133 30 29 1 2091.83 14.53 0.17 573.08 18.225 .02378 .0549 42. 052 29 28 2 2149.23 14.92 +0.22 572.48 17.759 .02381 .0563 42 4 000 28 27 3 2207.94 15.33 +0.63 571.89 17.307 .02384 .0577 41.946 27 26 4 2267.97 15.76 +1.05 571.28 16.869 .02387 .0593 41.893 26 25 435.66 2329.34 16.17 +1.47 570.68 16.446 .03389 .0608 41.858 -25 34 6 2392.09 16.61 1.91 570.08 16.034 .02393 .0624 41.806 24 23 7 2456.23 17.05 2.35 569.48 15.633 .02395 .0640 41.754 23 22 8 2520.45 17.60 2.8 568.88 15.252 .02398 .0656 41.701 22 21 9 2588.77 17.97 3.27 568.27 14.875 .02401 .0672 41.649 21 20 440.66 2657.23 18.45 +3.75 567.67 14.507 .02403 .0689 41.615 -30 19 1 2727.17 18.94 ^.24 567.06 14.153 .02406 .0706 41.563 19 18 2 2798.62 19.43 4.73 566.43 13.807 .02409 .0725 41.511 18 17 3 2871.61 19.94 5.24 565.85 13.475 .03411 .0742 41.480 17 16 4 3946.17 20.46 5,76 565.25 13.150 .03414 .0760 41.425 16 15 445.66 3022.31 20.99 +6.29 564.64 12.834 .03417 .0779 41.374 -15 14 6 3100.07 21.53 6.83 564.04 12.527 .03420 .0798 41.322 14 13 7 3179.45 23.08 7.38 563.43 12.230 .02423 .0818 41.271 13 12 8 3260.52 22.64 7.94 562.82 11.939 .02425 .0838 41.237 13 11 9 3343.29 23.22 8.52 562.21 11.659 .02428 .0858 41.186 11 10 450.66 3427.75 23.80 +9.10 561.61 11.385 .02431 .0878 41.135 10 9 1 3513.97 24.40 9.70 560.99 11.117 .02434 .0899 41.084 9 8 2 3601.97 25.01 10.31 560.39 10.860 .02437 .0921 41.034 8 7 3 3691.75 25.64 10.94 559.78 10.604 .02439 .0943 41.000 7 6 4 3783.37 26.27 11.57 559.17 10.362 .02443 .0965 40.950 6 5 455.66 3876. 85 26.92 +12.22 558.56 10.125 .02445 .0988 40.900 5 4 6 3972.62 27.59 12.89 557.94 9.894 .02448 .1011 40.845 4 3 7 4069.48 28.26 13.56 557.33 9.669 .02451 .1034 40.799 3 2 8 4168.70 28.95 14.25 556.73 9.449 02454 .1058 40.749 2 1 9 4269.90 29.65 14.95 556.11 9.234 .02457 .1083 40.700 1 +0 460.66 4373.10 30.37 +15.67 555.50 9.028 .03461 .1107 40.650 +0 1 4478.32 31.10 16.40 554.88 8.825 .02463 .1133 40.601 1 2 jj 4485.60 31.84 17.14 554.27 8.630 .02466 .1159 40.551 2 3 3 4694.96 32.60 17.90 553.65 8.436 .02469 .1186 40.502 3 4 4 4806.46 33.38 18.68 553.04 8.350 .02472 . 1213 40.453 4 * For values at temperatures higher than 100 F. see Wood's table on page 92. 330 MECHANICAL REFRIGERATION.. WOOD'S TABLE OF SATURATED AMMONIA Continued. Tempera- Pressure, '- ce- " S *h 73 X- ^ ! ture. Absolute. 1 fl |^ ! u -s !&s jSfcS PI*< 15 . **l s- a> o-Ja^ M ^a i^o h^rog r- 15 &< p. p-"3 S - k^" 11 "" O "o "S O &H *o P^- 1 h +* 1^ -o*" 1 a . IN ofS 1* ^o "M> 'S 1^1 | 2 3 C*_ 3 0< . pOfl ^ "^^ ^ QJ .Jl lt ^ ""' "' F ^ a +5 465.66 49 .'0.11 34.16 +19. 4fi 552.43 8.070 .02475 .1240 40.404 +5 t; 6 5035.95 34.97 20.27 551.81 7.892 .02478 40 355 6 7 7 5153.99 35.79 21.09 551.19 7.717 .02480 !l296 40.322 7 8 8 5274.28 36.63 21.93 550.58 ?! 553 .02483 .1324 40.274 8 9 9 5396.83 37.48 22.78 549.96 7.388 .02486 .1353 40.225 9 +10 470.66 5521.71 38.34 +23.64 549.35 7.229 .02490 .1383 40.160 +10 11 1 5549.48 39.:3 24.53 548.73 7.075 .02493 .1413 40.112 11 12 2 5778.50 40.13 25.43 548.11 6.924 .02496 .1444 40.064 12 13 3 5910.52 41.04 26.34 547.49 6.786 .02499 .1474 40.016 13 14 4 6044.96 41.98 27.28 546.88 6.632 .02502 .150739.968 14 +15 475.66 6182.00 42.94 +28.24 546.26 6.491 .02505 .1541)39.920 +15 16 6 6321.24 43 90 29.20 545.63 '6.355 .02508 .1573 39.872 16 17 7 6463.24 44.88 30.18 545.01 tf.222 .02511 .1607 39.872 17 18 8 6607.77 45.89 31.19 544.39 6.093 .02514 .1641 39.777 18 19 9. 6754.90 46.91 32.21 545.74 5.966 .02517 .1676 39.729 19 +20 480.66 6004.68 47.95 33.25 543.15 5.843 .02520 .1711 39.682 +20 21 1 7057.15 49 01 34.31 542.53 5.722 .02523 .1748 39.635 21 22 2 7211.33 50.09 35.39 541.90 5.605 .02527 .1784 39.572 22 23 3 7370.27 51.18 36.48 541.28 5.488 .0^539 .1822 39.541 23 24 4 7530.96 52.30 37.60 540.66 5.378 .02533 1800 39.479 . 24 +25 485.66 7694.52 53 43 +38. 73 540.03 5.270 .02536 .1897 39.432 +25 26 6 7860.89 54.59 39.89 539.41 5.163 .02539 .1937 3fl.3Sfi 26 27 7 8030.16 55.76 41.06i538.78 5.058 .02542 .1977)39.3:59 27 28 8 8202.38 56.96 42.26538.16 4.960 .02645 .201639.292 28 29 9 8377.56 58.17 43.47 537.53 4.858 .02548 .2059 39.246 29 +30 490.66 8555.74 59.42 +44.72 536.91 4.763 .02551 .209939.200 +30 31 1 8736.96 60.67 45.97536.28 4. 668 .02554 .214239.115 31 32 33 2 3 8921.26 9108.71 61.95 6'5.25 47.251535.66 48.55|535.03 4.577 4.486 .02557 .02561 .218539.108 .222939.047 32 33 34 4 9299.32 64.58 49.88 534.40 4.400 .02664 .2273 39.001 34 +35 495.66 9403.07 65.92 +51.22 533.78 4.314 .02668 .2318 38.940 +35 36 6 9690.04 67.29 52.59533.13 4.234 .02571 .236238.894 36 37 7 9890. 75 68.68 53.98532.52 4.157 .02574 .241338.850 37 38 8 10093.91 70.09 55.39531.88 4.068 .02578 .245838.789 38 39 9 10300.88 71.53 56.83 531.26 3.989 .02582 .250738.729 39 +40 500.66 10511.16 72.99 +58.29 530.63 3.915 .02585 .2554 38.6S4 +40 41 1 10724.95 74.48 59.78529.99 3.839 .02588 .260538.639 41 42 2 10942.18 75.99 61.29529.36 3.766 .02591 .265538.595 42 43 3 11162.93 77.52 62.82528.73 3.695 .02594 .270638.550 43 44 4 11387.21 79.08 64.38 528.10 3.627 .02507 .2757 38.499 44 +45 505.66 11615.12 80.66 +65.96 527.47 3.559 .02600 .2809 38.461 +45 46 6 11846.64 82.27 H7. 57 526. 83 3.493 .02603 .2863 38.417 46 47 7 12081.80 83.90 69.20i526.20 3.428 U'V(ii) .2917 38.373 47 48 8 12320.71 85.56 70.86525.57 3.362 ; 02609 .2974 38.32S 48 49 9 12563.36 87.25 72.56 524.93 3.303 .02612 .3027 38.284 49 +50 510.66 12809.91 88.96 +74.26 524.30 3.242 .02616 .3084 38.226 +50 51 1 13080.21 90.70 76.00 I 523.66 3.182 .02620 .3143 38.167 51 52 2 13314.43 92.46 77. 76^523. 03 3.124 .02623 .3201 38.124 52 63 3 13572.52 94.25 79.551522.39 3.069 .02626 .3258 38.080 53 54 4 13834.64 96.07 81.371521.76 3.012 .02629 .332038.037 54 APPENDIX I. 331 WOOD'S TABLE OF SATURATED AMMONIA Continued. tw Tempera- ture. Pressure, Absolute. |1 P, Si ' P< . 2S| $> ** . a;* 3 a is !|U ^a . fl sw'a o 3|f t/3 i a o P.O ^T3 > .. . Siii opL, a> o^ ogfe 01 I** g'-'CH & . QlH S . c-S g: 3^0 d ** o gf*3 -gfc<3 I ? gjjftj o FM 3 P..O '.5o 'S.So a>& Q > * ^ Q +55 515.66 14100.74 97. 92 +83.22 521 12 2.958 .02632 .3380 37.994 +55 50 6 14370.92 99.80 85.10 520.48 2.905 .02636 .3442 37.936 56 57 7 14645.18 101.70 87.00 519.84 2.853 .02639 .3505 37.893 57 58 8' 14923.98 103.64 88.94 519.20 2.802 .02643 3568 37.835 58 59 9 15206.28 105.60 90.90 518.57 2.753 .02646 13632 37.793 59 +60 520.66 15493.09 107.59 +92.89 517.93 2.705 .02651 .3697 37.736 +60 61 1 15784.23 109.61 94.91 517.29 2.658 .02654 .3762 37.678 61 62 2 16079.67 111.66 96.96 516.65 2.610 .02658 .3831 37.622 62 63 3 16379.51 113.75 99.05 516.01 2.565 .02661 .3898 37.579 63 64 4 16683.75 115.86 101.16 515.37 2.520 .02665 .3968 37.523 64 +65 525.66 16992.50 118.09 +103.33 514.73 2.476 .02668 .4039 37.481 +65 66 6 17305.70 120.18 105.48 514.09 2.433 .02671 .4110 37.439 66 67 7 17623.45 122.38 107.68 513,45 2.389 .02675 .4189 37.383 67 68 8 17945.89 124.62 109.92 512.81 2.351 .02678 .4254 37.341 68 69 9 18272.81 126.89 112.19 512.16 2.310 .02682 .4329 37.285 69 +70 530.66 18604.53 129.19 +114.49 511.52 2.272 .02686 .4401 37.230 +70 71 1 18941.00 131.54 116.84 510.87 2.233 .02689 .4479 37.188 71 72 2 19282.21 133.90 119.20 510.22 2.194 .02693 .4558 37.133 72 73 3 19628.32 136.31 121.61 509.58 2.153 .02697 .4645 37.079 73 74 4 19979.22 138.74 124.04 508.93 2.122 .02700 .4712 37.037 74 +75 535.66 20335.16 141.22 +126.52 508.29 2.037 .02703 .4791 36.995 +75 76 6 20696.00 143. 72 129.02 507.64 2.052 .02706 .4873 36.954 76 77 7 21061.85 146.26 131.56 506.99 2.017 .02710 .495736.900 77 78 8 21432.82 148.84 134.14 506.34 1.995 .02714 .501236.845 78 79 9 21808.85 151.45 136.75 505.69 1.952 .02717 .5123 36.805 79 +80 540.66 22190.15 154.10 +139.40 505.05 1.921 .02721 .5205 36.751 +80 81 1 22576.51 156.78 142.08 504.40 1.889. .02725 .529436.696 81 82 2 22968.88 159.50 144.80503.75 1.858 .02728 .538236.657 82 83 3 23365.38 162.26 147.56503.10 1.827 .02732 .547336.603 83 84 4 23767.81 165.05 150.35502.45 1.799 .02736 .5558 36.549 84 +85 545.66 24175.61 167.88 +153.18501.81 1.770 02739 .5649 36.509 +85 86 6 24588.92 170.75 156.05 501.15 1.741 .02743 .5744 36.456 86 87 7 25007.80 173.66 158.96 500.50 1.714 .0274.7 .5834 36.407 87 88 8 25432.16 176.61 161.91 499.85 1.687 .02751 .5927 36.350 88 89 9 25862.14 179.59 164.89 499.20 1.660 .02754 .6024 36.311 89 +90 91 550.66 1 26297.88 26739.88 182.62 185.69 +167.92 170.99 498.55 497.89 1.634 1.608 .02758 .02761 .6120 .6219 36-258 36.219 +90 91 92 2 27186.56 188.79 174.09 497.24 1.583 .02765 .6317 36.166 92 93 3 27639.43 191.94 177.24 496.59 1.558 .02769 .6418 36.114 93 94 4 28098.26 195.13 180.43 495.94 1.534 .02772 .6518 36.075 94 +95 555.66 28563.00 198.35 +183.65 495.29 1.510 .02776 .6622 36.023 +95 96 6 29033.86 201.62 186.92494.63 1.486 .02780 .6729 35.971 96 97 7 29510.69 204.94 190. 24|493.97 1.463 .02784 .6835 35.919 97 98 8 29993.52 208.29 193.59 493.32 1.442 .02787 .6934 35. 8U 98 99 9 30482.52 211.68 196.98492.66 1.419 .02791 .7047 35.829 99 +100 560.66 30977.78 215.12 +200.43492.01 1.398 .02795 .7153 35.778 +100 332 MECHANICAL REFRIGERATION. TABLE OF HUMIDITY IN AIR. s n 2 53 S ! ^.g co|fl^ 3 s-s8 5|, Sa g p|j &gss o> sil *-* Us 2^3 S&* ttng^jg ili* 9 H ;>0 H o m t>o 10 2.1 2.3 +13 11.2 11.4 9 2.3 2.5 --14 11.9 12.1 8 2.5 2.7 --15 12.7 12.9 7 2.7 2.9 --16 13.5 13.6 6 2.9 3.2 --17 14.4 14.5 6 3.1 3.4 +18 15.4 15.4 4 3.4 3.7 +19 16.3 16.3 3 3.7 4.0 +20 17.4 17.3 2 4.0 4.3 +21 18.5 18.4 1 4.3 4.6 +22 19.7 19.4 4.6 4.9 +23 20.9 20.6 - 1 5.0 5.3 +24 22.2 21.8 -2 5.3 5.6 +25 23.6 23.1 - 3 5.7 6.0 +26 25.0 24.4 - 4 6.1 6.4 +27 26.6 25.8 - 5 6.5 6.8 +28 28.1 27.2 -6 7.0 7.3 +29 29.8 28.8 - 7 7.5 7.8 +30 31.5 30.4 - 8 8.0 8.3 +31 33.4 32.1 -9 8.6 8.9 +32 35.4 33.8 -10 9.2 9.4 +33 37.4 35.7 +11 9.8 10.1 +34 39.3 37.6 +12 10.5 10.7 +35 41.5 39.3 TABLE SHOWING AMOUNT OF MOISTUR7S TO 100 LBS. OF DRY AIR WHEN SATURATED AT DIFFERENT TEMPERATURES. Temper- ature. Fahr. Degrees. Weight of Vapor in Ibs. Temper- ature. Fahr. Degrees. Weight of Vapor in Ibs. Temper- ature. Fahr. Degrees. Weight of Vapor in Ibs. 20 10 +10 20 32 42 52 0.0350 0.0574 0. 0918 0.1418 0.2265 0.379 0.561 0.819 62 72 89 92 102 112 122 132 1.179 1.680 2.361 3.289 4.547 6.253 8.584 11.771 142 152 162 172 182 192 202 212 16.170 22.465 31.713 4e.338 71.300 122. r>43 280.230 Infinite. LATENT UNITS OF HEAT OF FUSION AND VOLATILIZA- TION PER POUND OF SUBSTANCE. Solids Melted to Liquids. Latent Heat B. T. Units Liquids Converted to Vapor. Latent Heat B.T. Units Ice to water 142 Water to steam 966 Tin 25.6 Ammonia 495 Zinc 50 6 Alcohol pure 372 Sulphur ... 17.0 Carbonic acid 298 Lead 9 72 Bisulphite of carbon. 212 5 00 Ether, sulphuric 174 Beeswax ... . 175 Essence of turpentine 137 Bismuth 550 Oil of turpentine .... 184 Cast iron 233 Mercury 157 46.4 Chimogene 175 APPENDIX I. 333 COLD STORAGE RATES. The charges for cold storage and rates for freezing must depend greatly upon various conditions, such as capacity of house, demand and supply, competition to be met and other local conditions. For general use and as a basis for figuring, the following rates, which are those now in force in the principal cold storage points and which are generally adhered to, will be found useful: COLD STORAGE BATES PER MONTH. GOODS AND QUANTITY. id ^ a E l Each Succeeding Month. In Large Quantities, per Month. Season Rate per Bbl. orlOOLbs. Season Ends. $0.15 fO.12% 10.12% $0.45 Mayl. Bananas per bunch .. . .15 .10 .10 Beef, mutton, pork and fresh meats, per Ib .00 oou 00% Beer and ale per bbl 25 25 Beer and ale per H bbl .15 .15 Beer and ale, per J4 or % bbl. .10 .10 Beer, bottled, per case .10 .10 Beer bottled, per bbl 20 20 Berries, fresh, of all kinds, per quart . 00% 00% 00% Berries, fresh, of all kinds, per stand . 10 Butter and butterine, per Ib. (See also butter freezing rate.) Buckwheat flour, per bbl Cabbage, per bbl .00% .15 25 .OOK -12J4 25 .00% .10 20 .50-75 .50 Jan. 1. Oct. 1. Cabbage, per crate 10 10 .08 Calves (per day), each 10 Calves per Ib .... 00% 00 J4 00% Canned and bottled goods, per Ib 00 % 00% 00% Celery, per case 15 .10 .10 Cheese, per Ib 00% OOH 00% 56^-60 Jan 1 Cherries per quart 00% 00% 00% Cider, per bbl 25 .15 15 Cigars per Ib 00% 00 M. 00% Cranberries, per bbl 25 !20 .'15 Cranberries per case 10 Corn mi!:i 1, per bbl .15 .12% .10 Dried and boneless fish, etc., per Ib .00 1-5 .00% .80% 50 Nov. 1. Dried corn, per bbl 12 l / 2 10 10 Dried and evaporated apples, per Ib ;.. 00% .00 1-10 50 Nov.] Dried fruit per Ib 00 1-6 00% 0054 40-50 Nov. 1 Eggs per case 16 12% 10 50-60 Jan 1 Figs, per Ib 00% .00% 00 1-10 Fish, per bbl .20 .18 .15 75 Oct. 1. Fish, per tierce 15 .13 12H 50 Oct. 1. (See also fish freezing rates.) Fruits, fresh, per bbl .25 .20 .20 Fruits, fresh, per crate 10 .08 08 Furs, undressed, hydraulic pressed, per Ib oo y> .00*4 QQV 1 00 Oct. 1. Furs, dressed, perlb Ginger ale, bottled, per bbl. . .03 .20 .02 l / 2 .15 .02 .15 8.00 Oct.l. Grapes, per Ib .00% .00% .OOJi 2 00 Mayl. Grapes per basket 03 02 01 334 MECHANICAL REFRIGERATION. COLD STORAGE RATES PER MONTH Continued. GOODS AND QUANTITY. 43^3 If "S Each Succeeding Month. In Large Quantities, per Month. Season Rate per Bbl. or 100 Lbs. Season Ends. Grapes, Malaga, etc., per keg. Hops, per Ib ; .15 .00% .25 .25 .15 .20 .00% .01*4 .00% .OOJ4 .20 .25 1.00 .00X3 .15 .12*4 .15 .05 .50 .10 .20 .40 .00% .20 .25 .OOM .25 .20 .25 .15 .30 .00% .25 .15 .25 .10 .12*4 .00^ .20 .20 .121/2 .15 .OOM .Olfc .00*4 .00 1-5 .15 .20 .80 .00*4 ' .12*4 .10 .12*4 .04 .40 .08 .15 .30 .OOM .15 .20 T .15 .20 .12*4 .25 .0014 .20 .10 .25 .10 .12% .00% .20 .20 .10 .12*4 .00% .01 .00% .00% .12*4 Lard per tierce 1.00 1.00 .50 Nov. 1. Nov. 1. Nov. 1. Lard oil, per cask Lemons per box Maple sugar per Ib .40-50 Nov. 1. Maple syrup, per gallon Nuts of all kinds, per Ib Oatmeal, per bbl .40-50 Nov. 1. Oil' per hhd Oleomargarine, per Ib .00% .10 ; 56^.6' Mayl. Oranges, per box .10 .50 Nov. 1. Oysters, in tubs, per gal Oysters, in shell, per bbl Peaches, per basket Pears per box .30 .07 2.00 .60 1.20 1.00 Jan. 1. Mayl. Mayl. Nov. 1. Pears per bbl Pigs' feet, per Ib Pork per tierce .0034 .15 .20 & .12*4 .15 .10 .20 -OO 1 /^ .15 .08 Preserves, jellies, jams, etc., per Ib Rice flour, per bbl Sauerkraut per cask .60-75 Nov. 1. Sauerkraut, per * bbl 1.00 Oct. 1. Vegetables, fresh, per bbl Vegetables, fresh, per case. . . Wine in wood per bbl Wine, in bottles, per case BATES FOR FREEZING POULTRY, GAME, FISH, MEATS, BUTTER, EGGS, ETC. The rates for freezing goods, or for storing goods at a freezing temperature when they are already frozen, as follows: POULTRY, GAME, ETC. , IN UNBROKEN PACKAGES. Poultry, including turkeys, fowl, chickens, geese, etc., and rabbits, squirrels and ducks when picked. Four rates, A, B, C and D, for storing poultry, and the rate to be charged will be determined by the amount of such goods as may be frozen and stored during a season of six months, usually from October or November 1 to April or May 1. KATE A. For customers storing fifty (50) or more tons of poultry, the rate to be one-third cent per pound for APPENDIX I. 335 the first month stored, and one-fourth cent per pound for each month or fraction of a month, including the first month, if stored for more than one month. BATE B. For customers storing five or more, but less than fifty tons of poultry, the rate to be one-third cent per pound for the first month stored, and one-fourth cent per pound for each month or fraction of a month thereafter. RATE C. For customers storing one or more, but less than five tons of poultry, the rate to be three-eighths cent per pound for the first month stored, and one- fourth cent per pound for each month or fraction of a month thereafter. RATE D. For customers storing less than one ton of poultry, the rate to be one-half cent per pound for the first month stored, and three-eighths cent per pound for each month or fraction of a month thereafter. Venison, etc., and ducks when unpicked, one to one- half cent per pound per month, according to quantity and length of time stored. Grouse and partridges, three cents to five cents per pair per month. Woodcock, one cent to two cents per pair per month. Squabs and pigeons, four cents to six cents per dozen per month. Quail, plover, snipe, etc., three cents to five cents per dozen per month. When a portion of the goods is removed from a pack- age, storage to be charged for the whole package as it was received until the balance of the package is removed from the freezer. For goods received loose, when to be taken out of the packages in which they are received, or when to be laid out, the following rates to be charged: Poultry, including turkeys, chickens, geese, etc., and rabbits and squirrels, one-half cent to one-fourth cent per pound extra, according to quantity and length of time stored. Grouse, partridges, woodcock, squabs, pigeons, quail, plover and snipe, 50 per cent more than the rates as above specified. Ducks weighing less than two pounds each, two cents to three cents each per month. Ducks weighing two pounds or more each, three cents to four cents each per month. 336 MECHANICAL REFRIGERATION. For all kinds of poultry and birds not herein speci- fied, the rate from one cent to one-half cent per pound per month, according to quantity and length of time stored. SUMMER FREEZING RATES. Freezing rates for the summer months, 50 per cent more than the specified winter rates for the first month stored, and the same as the winter rates for the second and succeeding months. STORING UNFROZEN POULTRY, ETC. For holding poultry, game, etc., which are not frozen, at a temperature which shall be about 30 F., the rate to be one-fifth cent to two-fifths cent per pound, ac- cording to quantity, for any time not exceeding two weeks. FREEZER RATES FOR FISH AND MEATS. Salmon, blue fish and other fresh fish in packages, one-half cent per pound for the first month stored, three- eighths cent per pound per month thereafter. Fresh fish of all kinds when to be hung up or laid out, three-fourths cent per pound for the first month stored, one-half cent per pound per month thereafter. Fish in small quantities, 50 per cent more than the above rates. Special rates for large lots of large fish. Scallops, three-fourths cent per pound, gross, per month. Sweetbreads and lamb fries, one cent per pound, gross, per month. Beef, mutton, lamb, pork, veal, tongues, etc., three- fourths cent to one-half cent per pound, net, for the first month stored, one-fourth cent to three-eighths cent per pound per month thereafter. BUTTER FREEZING RATES. For freezing and storing butter in a temperature of 20 F. or lower, the rate to be charged will be determined by the amount of such goods that may be frozen and stored during the season of eight months, from April 1 to December 1, or from May 1 to January 1. There will be three rates, A, B and C. BATE A. For customers storing thirty-five (35) or more tons of butter, the rate to be fifteen cents per 100 pounds, net, per month. APPENDIX I. 337 BATE B. For customers storing five or more, but less than thirty-five tons of butter, the rate to be eigh- teen cents per 100 pounds, net, per month. KATE C. For customers storing less than five tons of butter, the rate to be twenty-five cents per 100 pounds, net, per month. EGG FREEZING RATES. For freezing broken eggs in cans, the charge to be one-half cent per pound, net weight, per month, and for a season of eight months the rate to be one and one-half cents per pound, net weight. RENT OF ROOMS. For freezing temperatures, four cents to five cents per cubic foot per month. TERMS OF PAYMENT OF COLD STORAGE AND FREEZING RATES. All the above rates are the charges for each month, or fraction of a month, unless otherwise specified; and in all cases, fractions of months to be charged as full months. Charges to be computed in all cases when possible upon the marked weights and numbers of all goods at the time they are received. All storage bills are due and payable upon the deliv- ery of a whole lot, or balance of a lot of goods, or every three months, when goods are stored more than three months. Unless special instructions regarding insurance ac- company each lot of goods, they are held at owner's risk. DESCRIPTION OF TWO-FLUE BOILERS. NUMBER. 1 2 3 4 5 6 Heating 1 Surface, square feet. Horse power at 10 square feet. Diameter, inches 105 10 30 10 10 15x15 30 3 4 6 l l / 2 l l /2 15 30 16 2100 4400 152 15 32 14 10 K % 15x15 32 8* 6 j* 15 30 16 2580 5100 201 20 36 16 12 u % 18x18 36 4 6 6 r* 18 30 16 3300 6400 349 25 40 18 13 K 20x20 40 4 6 6 18 35 16 4250 T350 356 36 44 22 15 24x2l 44 1 Uf 8H 24 40 16 5225 8800 508 51 50 28 18 5-16 7-16 30x30 60 5 8 7 is 3 26 50 16 10000 15000 Length feet . Diameter of Flues, inches . . . Thickness of Shell, inches.. . Thickness of Head, inches . . . Size of Dome, inches Width of Grate Bars, inches . Length of Grate Bars, feet. . Number of Wall Binding Bars Length Wall Binding Bars, ft. Diameter of Blow-off Cock, ins Diameter of Safety Valve, ins Diameter of Smoke Stack, ins Length of Stack, feet Number of Iron in Stack Approximate Weight of Boiler Total Weight 338 MECHANICAL REFRIGERATION. USEFUL NUMBERS FOR RAPID APPROXIMATION. Feet x .00019 =miles. Yards , x .0006 =miles. Links .X .22 =yards. Links .X .66 =feet. Feet .X 1.5 =links. Square inches .007 = square feet. 00546 ^quare feet Square feet Acres .X .X .111 =square yards. 4840. = square yards. Square yards ..X .0002066= acres. Cubic feet .04 =cubic yards. Cubic inches .X .00058 =cubic feet. U. S. bushels .X .046 =cubic yards. U. &. bushels 1.244 =cubic feet. U. S. bushels , x 2150.42 =cubic inches. Cubic feet .X .8036 = U. S. bushels. Cubic inches ... . x 000466 -US "bushels U. S. gallons .X .13368 = cubic feet. U. S. gallons ,x 231. =cubic inches. Cubic feet .X 7.48 =U. S. gallons. Cylindrical feet .X 5.878 =U. S. gallons. Cubic inches .X .004329 =U. S. gallons. Cylindrical inches ,x .0034 =U. S. gallons. Pounds x .009 =cwt.(1121bs.) Pounds ,x .00045 =tons (2,240 Ibs.) Cubic feet water x 62.5 =lbs. avdps. Cubic inches water x .03617 =lbs. avdps. Cylindrical feet of water , x 49.1 =lbs. avdps. Cylindrical inches of water X .02842 =lbs. avdps. 13 44 cwt (112 Ibs ) U. S. gallons of water , 268.8 =tons. Cubic feet water ..-z- 1.8 =cwt. (112 Ibs.) Cubic feet water -i. 35.88 =tons. Cylindrical feet ol water , Col. of water 12 in. high, 1 in. diam . . -r- 5.875 =U.S. gallons. = .34 Ibs. 183 346 circular inches , =1 square foot. 2,200 cyclindrical inches =1 cubic foot. French meters ,x 3.281 =feet. Kilogrammes , 2.205 =avdps. Ibs. Grammes ....." .X .0022 =avdps Ibs. 12 X wt. of pine pattern = iron casting. 43 X wt. of pine pattern = brass casting. 19 X wt, of pine pattern = lead casting. 12.2 x wt. of pine pattern = tin casting. 11.4 X wt. of pine pattern = zinc casting. 1 cubic foot anthracite coal = 54 Ibs. 4043 cubic feet anthracite coal = 1 ton. 49 cubic feet bituminous coal = 1 ton. 537 Ibs. per cubic foot = wt. of copper. 450 Ibs. per cubic foot = wt. of cast iron. 485 Ibs. per cubic foot = wt. of wrought iron. 708 Ibs. per cubic foot = wt. of cast lead. 490 Ibs. per cubic foot = wt. of steel. 1 gallon water = 83^ Ibs. = 231 cubic inches. 1 cubic foot water = 62{4 Ibs. = 7 1 A gallons. 1 Ib. water = 27.8 cubic inches = 1 pint. The friction of water in pipes is as the square of its velocity. Doubling the diameter of a pipe increases its capacity four times. In tubular boilers, 15 square feet of heating surface are equiv- alent to one horse power; in flue boilers, 12 square feet of heating surface are equivalent to one horse power; in cylinder boilers, 10 square feet of heating surface are equivalent to one horse power. One square foot of grate will consume, on an average, 12 Ibs. of coal per hour. Consumption of coal averages 7J^ Ibs. of coal, or 15 Ibs. of dry pine wood, for every cubic foot of water evaporated. The ordinary speed to run steam pumps is at the rate of 100 feet piston travel per minute. APPENDIX I. 339 1 8 rH GO ** -*T ^H rH OOOrHCOOOO -8' . d r2,p-*j C3 J ^ Q C/J 3 hr O^ 3 O 9 IESII >O( CH Sfe of-o" 1-8 a 5^ fl c< cc External Sq. Inch. IP ss Nomin Intern Inche L'- O 1C 5 COCO IS ssIS Ot-OiO T-iiO iNjO SSS8 SSis 340 MECHANICAL REFRIGERATION. ^srveqx'fr a -* *** o o o to ooe *****- ao co ao ao ao puno^j H * l5 >O CO C* CO CO * O 00 T-I N -H < fi O O eo o c-t-oo QO os 05 as o oi-t IH 01 j co co ^ * ^j c w >o o ODOOt C^C^Il^tD^Gir^OOGCiCC^J 'ONI APPENDIX I. 341 TABLE OF MEAN TEMPERATURE OF DIFFERENT LOCALI- TIES, DEGREES FAHR. LOCATION. 1 bit Ti P. 03 Summer. Autumn. Winter. Algiers .. 63 63 74 5 70 5 Kf) A Berlin 47 5 46 4 63 1 47 8 30 6 Berne 46 45 8 60 4 47 3 Sfl 4 49 48 66 53 28 Baltimore . 54 9 60 83 64 6 43 5 Buenos Ayres 62 5 59 4 73 fi4. fi K9 K Cairo.. 72 3 71 6 84 6 74 3 58 6 Calcutta. 78 4 82 6 83 3 80 67 8 Canton 69 8 69 8 82 72 9 54 8 Christiania 41 7 39 2 59 5 4-2 4 2*\ 2 Cape of Good Hope Constantinople . . . 66.4 56 7 63.5 51 8 74.1 73 4 66.9 60 4 58.6 4f) fi Copenhagen 46 8 43 7 63 48 7 31 3 Chicago 45 9 59 g 74 6 61 2 38 4 Cincinnati 54 7 63 2 81 8 66 4 46 6 Edinburgh 47 5 45 7 57 9 48 38 5 Jerusalem 62 2 6Q 6 72 6 66 3 49 6 Jamaica (Kingston) . 79 78 3 81 3 80 76 3 Lima (Peru) 66 2 63 73 2 69 6 59 Lisbon 61 5 59 9 71 1 62 6 . 52 3 London 50 7 49 1 62 8 51 3 39 6 Madeira (Funchal) 65 7 63 5 70 61 3 Madrid 57 6 57 6 74 1 56 7 42 1 Mexico City 60 5 53 6 63 4 65 2 60 1 43 7 44 2 69 1 47 1 17 "> Moscow 38 5 43 3 62 6 34 9 13 5 61 5 59 4 74 8 62 2 4Q 6 72 73 84 72 58 New York 53 50 72 56 '-?'-{ New Zealand 59 6 60 1 66 7 58 53 5 Nice 60 1 55 9 72 5 63 48 7 Nicolaief (Russia) 48 7 49 3 71 2 50 25 9 Paramatto (Australia) 64 6 66 6 73 9 64 8 54 K Palermo 63 59 o 74 3 66 2 52 5 Pekin (China) . . ...... 52 6 56 6 77 8 54 9 29 Paris 51 4 50 5 61 6 co 2 or q Philadelphia 55 52 76 57 34 Quito (Equador) 60 1 60 3 60 1 62 5 59 7 Quebec 40.3 73 6 72 5 79 74 5 68 5 Rome . . 59 7 57 4 73 y 61 7 46 6 San Francisco 57 5 58 59 60 53 St Louis 55 84 6 67 8 44 6 41; St Petersburg 38 3 35 i 60 3 40 5 16 6 Stockholm 42 1 ' 38 3 61 43 7 25 5 Trieste 55 8 53 8 7J 5 56 7 39 4 Turin 53 1 53 1 71 '6 53 8 33 4 Vienna . 50 7 49 1 62 8 51 3 39 6 Warsaw 45 5 44 6 63 5 46 4 27 6 Washington .... 59 69 79 58 USEFUL DATA ABOUT LIQUIDS. A gallon of water contains 231 cubic inches, and weighs 8i pounds (U. S. standard). A cubic foot of water contains 7% gallons, and weighs pounds. One U. S. gallon=.133 cubic feet; .83 imperial gal- lon; 3.8 liters. 342 MECHANICAL REFRIGERATION. An imperial gallon contains 277.274 cubic inches. .16 cubic feet; 10.00 pounds; 1.2 U. S. gallons; 4.537 liters. A cubic inch of water=.03607 pound; .003607 impe- rial gallons; .004329 U. S. gallon. A cubic foot of water =6.23 imperial gallons; 7.48 U. S. gallons; 28.375 liters; .0283 cubic meters; 62.35 pounds; 557 cwt.; .028 ton. A pound of water = 27.72 cubic inches; .10 imperial gallon; .083 U. S. gallon; .4537 kilos. One cwt. of water = 11.2 imperial gallons; 13.44 U. S. gallons; 1.8 cubic foot. A ton of water = 35.9 cubic feet; 224 imperial gallons; 298.8 gallons; 1,000 liters (about); 1 cubic meter (about). A liter of water = .,220 imperial gallon: .264 U. S. gallon; 61 cubic inches; .0353 cubic foot. A cubic meter of water = 220 imperial gallons; 264 U. S. gallons; 1.308 cubic yards; 61,028 cubic inches; 35.31 cubic feet; 1,000 kilos; 1 ton (nearly); 1,000 liters. A kilo of water = 2.204 pounds. A vedros of water = 2.7 imperial gallons. An eimer of water = 2.7 imperial gallons. A pood of water = 3.6 imperial gallons. A Russian fathom = 7 feet. One atmosphere = 1.054 kilos per square inch. One ton of petroleum =275 imperial gallons (nearly). One ton of petroleum = 360 U. S. gallons (nearly). A column of water 1 foot in height = .434 pound pressure per square inch. A. column of water 1 meter in height = 1.43 pounds pressure per square inch. One pound pressure per square inch = 2.31 feet of water in height. One U. S. gallon of crude petroleum = 6.5 pounds (nearly). One wine gallon, or U. S. gallon, is equal to 8.331 pounds=3,785 cubic centimeters=58,318 grains. One imperial gallon (English gallon) is equal to about ten pounds=4.543 cubiocentimeters=70,000 grains. One grain=0.0649 grams one gram=15.36 grains. One barrel =1.192 hectoliters one hectoliter=0.843 barrels. One English quarter=eight bushels =290.78 liters. One English bushel=36.36 liters=0.3635 hectoliters. One English barrel=36 gallons. One American barrel=31 gals. One bushel malt (English), 40 pounds; American, 34 pounds (32 pounds cleaned); one bushel barley (American), 38 pounds. One kilogram square centimeter equal to 14.2 pounds inch pressure (equal to about one atmosphere). Four B. T. units equal to about one calorie. APPENDIX I. 343 TEMPERATURES FAHRENHEIT AND CENTIGRADE. .F. C. "F. tf O F. a op C. F, a F c. 330 165.6 267 130.6 206 96.7 143 61.7 80 267 19 - 7.2 329 165. 266 130. 205 96.1 142 61.1 79 26.1 18 78 328 164.4 265 U9.4 204 95.6 141 60.6 78 25.6 17 - 8.3 327 163.9 264 128.9 203 95 140 60 77 25. 16 - 8.9 326 163.3 268 128.3 202 94.4 139 59 4 76 24 4 15 9.4 325 162.8 262 127.8 201 93.9 138 58.9 75 23.9 14 10. 324 162.2 261 127.2 200 93 3 137 58.3 74 23.3 13 10-6 323 161.7 260 126.7 19!) 92.8 136 57.8 73 22.8 12 11.1 322 161.1 25!) 126.1 198 92.2 135 57.2 72 22.2 n -11.7 321 160.6 258 125.6 107 91 7 134 56 7 71 21.7 10 -12.2 320 160. 257 125. 196 91 1 133 56.1 70 21 1 9 -12.8 319 1,59.4 2:>6 124.4 195 90.6 132 55.6 69 20.6 8 13.3 318 158.9 255 123.9 194 90. 131 55. 68 20. 7 -13.9 317 158.3 254 123.3 L93 89.4 130 54.4 67 19 4 6 -14.4 316 157.8 253 122-. 8 192 .88.9 129 53.9 66 18.9 5 -15. 315 157.2 252 122.2 191 88.3 128 53.3 66 18.3 4 -15.6 314 156.7 251 121.7 190 87.8 127 52.8 64 17'. 8 3 -16.1 313 156.1 250 121.1 1S9 87.2 126 52.2 63 17.2 2 16 7 312 155.6 249 120.6 188 86.7 1 25 51 7 62 16.7 1 -17.2 311 155. 248 120. 187 86.1 121 51.1 61 16.1 17.8 310 154,4 247 119.4 1*6 85.6 123 50 6 60 156 - 1 -18.3 309 138*9 24(1 ais.9 185 85. 122 50. 59 15 - 2 -18.9 308 153.3 245 118.3 1*J 84.4 121 49.4 58 14 4 3 -19 4 307 152.8 24! 117.8 1*3 83.9 120 48.9 57 13.9 - 4 -20 306 152.2 24-! 117.2 182 83.3 119 48:3 50 13 3 5 -20.6 305 151.7 242 116.7 181 82.8 IIS 47.8 55 12.8 - 6 -21.1 304 151.1 241 116.1 180 82.2 117 47.2 54 12.2 7 -21.7 303 150.6 240 115.6 179 81.7 116 46.7 53 11.7 - 8 -22.2 302 150. 239 115. 178 81.1 115 46.1 52 11.1 9 -22.8 301 149.4 288 114.4 177 80,6 114 45.6 51 10.6 10 -23.3 300 148.9 237 113.9 17(5 80. 113 45. 50 10. 11 23 9 299 148.3 236 113 3 175 79.4 112 44.4 49 9 4 -12 -24 4 298 147.8 235 112.8 174 78.9 111 43.9 48 8.9 -13 -25. 297 147.2 234 112.2 173 78.3 110 43.3 47 8.3 -14 -25 6 296 146.7 233 111.7 172 77.8 10!) 42.8 46 7.8 15 --26 1 295 146.1 2:i2 111.1 171 77.2 108 42.2 45 7.2 -16 -26.7 294 145.6 231 110.6 170 76.7 107 41.7 44 6.7 17 -27.2 293 145. 23n 110. 16!) 76.1 106 41.1 43 . 6.1 18 -27.8 292 144.4 22!) 109.4 168 75.6 105 40.6 42 5.6 19 58.3 291 143.9 22S 108.9 167 75. 104 40. 41 5 -20 -28.9 290 143.3 "27 108.3 166 74.4- 103 394 40 4.4 -21 -29.4 289 142.8 22(i 107.8 16f) 73.9 102 38.9 39 3.9 -22 ~"Qi 288 142.2 225 107.2 164 73.3 101 38 3 38 3.3 -23 ?ec3.0jjj6 287 141.7 224 106.7 163 72.8 100 37.8 37 2.8 -24 &K 286 141.1 223 106.1 162 72.2 99 37.2 36 2 2 -25 - 5i77 285 140.6 .,.,., 10S.6 161 71.7 98 36 7 86 1.7 -26 r-322 284 140. 221 105 160 71.1 97 36 1 34 1.1 27 -32.8 283 139.4 220 104.4 159 70.6 96 35.6 33 0.6 -28 -33.3 282 138.9 219 103.9 158 70. 95 35. Water freezes 29 33.9 i281 138.3 218 103.3 157 69.4 94 34.4 O9 A -30 -34.4 280 279 137r8 137.2 217 216 102.8 102.2 150 155 68.9 68.3 93 92 33.9 33.3 9Z 31 - 0.6 Eg -35. -35.6 278 136.7 215 101.7, 154 67.8 91 32.8 30 1.1 -33 36.1 277 136.1 214 101.1 153 67.2 90 32.2 29 17 -34 -36.7 276 135.6 213 100.6 152 1 cri 66..7 Q(* "I 8!) nr> 31.7 01 i 28 AM 2.2 O Q -35 -37.2 275 274 135. 134.4 Water boils 151 150 b<> . ] 65.6 so 87 ol.l 30.6 Z i 26 J.O - 3.3 36 37 37. H 38.3 273 133.9 212 100. 149 65. 86 30. 25 3.9 38 38.9 272 133.3 211 99.4 148 64,4 85 29.4 24 - 4.4 39 39.4 271 132.8 210 98.9 147 63.9 84 28.9 23 - 5 270 269 132.2 131.7 209 98.3 208 97.8 146 145 63.3 62.8 83 82 28.3 27.8 22 21 - 5.6 6.1 Mercury freezes- 26S 131 a 203 97.2 144 62.2 81 27.2 20 - 6.J -40 tfM MECHANICAL REFRIGERATION. SPECIFIC GRAVITY TABLE 344 The meaning of the degrees of the Beaume scale for liquids heavier than water has been defined somewhat differently by the manufacturing chemists of the United States. Accordingly the specific gravity for any given degree Beaume is found after the formula: Specific gravity- 145 _ deg 14 g eaum ^ The following table is calculated after this formula by Clapp: Degrees. Specific Gravity. Degrees. Specific Gravity. Degrees. Specific Gravity. 1.000 18 1.142 45 1.450 1 1.007 19 1.151 50 1.526 2 1.014 20 1.160 55 1.611 3 1.021 21 1.169 60 1.706 4 1.028 22 1.179 65 1.812 5 1.036 23 1.188 70 1.933 6 1.043 24 1.198 7 8 9 1.051 1.058 1.066 25 26 27 1.208 1.218 1.229 66 Used by sulphuric acid man- uf actur- ers. 1.835 10 1.074 28 1.239 11 1.082 29 1.250 12 1.090 30 1.261 13 1.098 32 1.283 14 1.107 34 1.295 15 1.115 36 1.306 16 1.124 38 1.318 17 1.133 40 1.381 APPENDIX I. 346 TABLE ON SOLUTIONS OF CHLORIDE OF CALCIUM. Specific Gravity at 64 F. Degree Beaum6 at 64 F. Degree Salometer at 64 F. Per Cent of Chloride of Calcium. Freezing Point. Deg. F. Ammonia Gauge. Pounds per Square Inch at Freezing Point 1.007 1 4 0.943 +31.20 46 1.014 2 8 1.886 4-30.40 45 1.021 3 12 2.829 +29.60 44 1.028 4 16 3.772 +28.80 43 1.035 5 20 4.715 +28.00 42 1.043 6 24 5.658 -26.89 41 1.050 7 28 6.601 -25.78 40 1.058 8 32 7.544 -24.67 38 1.065 9 34 8.487 -23.56 37 1.073 10 40 9.430 -22.09 35.5 1.081 11 44 10.373 -20.62 34 1.089 12 48 11.316 -19.14 32.5 1.097 13 52' 12.259 -17.67 30.5 1.105 14 56 13.202 ^15.75 29 1.114 15 60 14.145 -13.82 27 1.112 16 64 15.088 +11.89 25 1.131 17 68 16.031 h 9.96 23.5 1.140 18 72 16.974 - 7.68 21.5 1.149 19 76 17.917 - 5.40 20 1.158 20 80 18.860 - 3.12 18 1.167 21 84 19.803 0.84 15 1.176 22 88 20.746 4.44 12.5 1.186 23 92 21.689 8.03 10.5 1.196 24 96 22.632 11.63 8 1.205 25 100 23.575 15.23 6 .215 26 104 24.518 19.56 4 .225 27 108 25.461 24.43 1.5 .236 ' 28 112 26.404 29.29 1 "Vacuum .246 29 116 27.347 35.30 5 " .257 30 120 28.290 41.32 8.5 .268 31 29.233 47.66 12 " .279 32 30.176 54.00 15 " .290 33 31.119 44.32 10 " 1.302 34 32.062 34.66 4 " 1.313 35 33 25.00 1.51bs. This table, which has been published by a manu- facturer of chloride of calcium, gives the freezing points much lower in some cases than the small table on page 142. 346 MECHANICAL REFRIGERATION. FRICTION OF WATER IN PIPES. Frictional loss in pounds pressure for each 100 feet in length of cast iron pipe discharging the stated quanti- ties per minute: II SIZES OF PIPES, INSIDE DIAMETER. ,| 13 K" *" .X", *" 8" 3J6. 1 3 4" 6" 8" 10" 13" M" t6" 18" *3 ~i 3-3 x>.8 4 3i '.19 T 5 12 iS ::1 47 97 .27 10 J5 ; 16 M.-30 1.66 20 / 8P 19.00 6.40 8.62 .67 .21 .JO 25 ' '35 27.5 9.15 3 75 .91 -3 .12 3 33 37 fs sit ao*a 8/15 i!6o 2.01 42 .17 .27 35 45 94-9 10.00 2-44 .81 :35 9 5" a #; 82^40 5.32 1.80 .'74 .21 75 i .3 39 9.46 3.30 33 05 joo >3 48.1 4-9 4-89 1.99 .07 "5 5 807 21.2 28.1 47 '7 i 8 19.66 III ft 95 1.22 1,89 .10 ,,14 :ll .02 03 05 .07 .01 03 203 S49 , 28.06 11.20 2.66 37 .09 04 fOO5 3 00 33-41 15-20 3-65 50 .11 05 .007 350 37* tt 42,95 2 S !oO .30,80 4-73 6.01 7^43 4-'3 2 1 .96 2.21 15 .20 25 53 .06 .08 :3 .OI .02, .017 .036 .609 .019 .965 .Oil 400 450 500, 750 .830 3.88 32 ..13. .062 .036 .020 1000- t I ,46 49 .20 .091 .049 .028 1250 1245 2.09 .70 .29 .071 .040 1500 M50 95 38 . 181 095 054 1750 1660 1.23 49 .234 .123 .071 2000 .63 .297 .086 22 5 975 77 .362 . jby .107 2500 49 t.II :& :8 .150 .204 35^ 3320 .910 .472 .263 4000 {3735 593 333 4500, i .730 * c The frictional loss is greatly increased by bends or irregularities in the pipes. COMPARISON OF UNITS OF ENERGY (HERING.) Acceleration of gravity = Acceleration of gravity 1 dyne 1 dyne 1 grain gram pound avdp. foot pound foot pound foot pound metric horsepower hour = 1952940. metric horsepower hour 270 >00. metric horsepower hour = 2529.7 metric horsepower hour 1405 4 metric horsepower hour = .98634 horsepower hour . =2685400. horsepower hour . =1980000. horsepower hour . 2564.8 1 horsepower hour 1 horsepower hour ~T 646.31 981.000 centimeters per second. 32.186 feet per second. .015731 grain. .0010194 gram. = 6,3.608 dynes. = 981. dynes. = 444976. dynes. .0012953 pound Fah., heat unit. .0)7196 pound C., heat unit. .(1)03264 kilogr.-C., heat unit. foot pounds, kilogram meters, pound Fah., heat uni.s pound C., hear, units, horsepower hour, joules, foot pounds, pound Fah., heat units pound C.. heat units. kilogr.-C., heat units. APPENDIX I. 347 _ 1047.03 joules. = 7'. 2. foot pounds. - 106.731 kilogram meter. = .55556 pound Centigrade. : .35200 .29084 kilogram Centigrade, watt-hour. = 1 Brit, therm, unit (B.T.U.) 1884.66 1389.6 foot pounds. 192.116 1.8 .52353 kilogram meters, pound Fahrenheit, watt-hour. .0007018 horsepower hour. 3068.5 foot pounds. 423.54 kilogram meters. 3. 9683 1.1542 pound Fahrenheit, watt-hours. .0015472 horsepower hour. 3600. joules. 2654.4 foot pounds. 3.4383 1. dyne-centimeter. .0000001 joules. 981.00 ergs. 10000000. ergs. .737324 foot pound. .101937 kilogram meter. .0013406 horsepower for one sec. .0009551 COMPARISON OF UNITS OF ENERGY (BERING). 1 pound Fahrenheit 1 pound Fahrenheit 1 povnd Fahrenheit 1 pound Fahrenheit 1 pound Fahrenheit 1 pound Fahrenheit 1 pound Fahrenheit 1 pound Centigrade 1 pound Centigrade 1 pound Centigrade 1 pound Centigrade 1 pound Centigrade 1 pound Centigrade 1 kilogram Centigrade 1 kilogram Centigrade 1 kilogram Centigrade 1 kilogram Centigrade 1 kilogram Centigrade 1 watt-hour 1 watt-hour 1 watt-hour 1 erg 1 erg 1 grani centimeter 1 joule 1 volt-coulomb 1 watt during every second 1 volt ampere dur- ing every second 1 volt ampere dur- ing every second 1 foot-pound 1 foot-pound 1 foot-pound 1 foot-pounu 1 horsepower . 1 horsepower ;' 1 horsepower . 1 horsepower 1 Ib. F. heat unit per min = 1 Ib.P. heat unit per min , 1 Ib.F. heat unit per min = 1 Ib. Ct. heat unit per min ; 1 k. Ct. heat unit per min -. 1 Pferdekraft 1 erg per second 1 watt 1 volt ampere 1 volt coulomb per sec. = 1 volt coulomb per sec. : 1 foot pound per rain. = 1 foot pound per min. = 1 foot pound per min. = 1 metric horsepower 1 French horsepower ' 1 chevalvapeur m 1 force de cheval . 1 horsepower 1 horsepower * 1 horsepower 1 horsepower 1 ton of refrig. capacity= 1 ton of refrig. capacity- 1 ton of ref. cap. per day = 1 ton of ref. cap. per day = = 18602000.. = 13825'/ .0018434 745.941 33000. 42.746 1.01385 17.4505 .033718 .023394 .042109 pound F. heat unit. ergs. joules. kilogram meter. metric horsepower for one second. watts. foot pounds per minute. Ib. R 1 ., heat unit per min. metric horsepowers. watts. metric horsepower. horsepower. horsepower. horsepower. klg. cent. watt. ergs per second. foot pounds per min. Ib. F. heat unit per min. horsepower watt: .00003072 metric horsepower. .000030303 horsepower. 735.75x107 ergs per second. foot pounds per minute. Ib. F. heat units per min. Ib. Ct. beat unit per min. foot pounds per minute. foot pounds per hour. H. units per kour (B.T. units). B. T. units per minute. B. T. units. to about "4-ton ice making capacity, to about 12000 B. T. units per hour, to about 200 B. T. units per minute. 10.635 .0000001 10000000. 443394. .0573048 .001340ti .0226043 J.O 42.162 33.433 asooo. 198uOOO. 2565. 42.75 284000. In these tables the mechanical equivalent of heat is taken at 772. Many engineers prefer the more recent figure, 778. 348 MECHANICAL REFRIGERATION. TABLE OF MEAN EFFECTIVE PRESSURES. EFFECTIVE PRESSURE IN POUNDS / / / // / / 80/90/100/110 12d 130 1*0 tSd l0 170 18fl" xlSO/ZOtf The above graphical table will be found of assistance to the engineer by affording a ready, and, at the same time, comprehensive means of ascertaining the mean effective pressure of steam in an engine cylinder, when the initial steam pressure and the point of cut-off or the number of expansions of the steam are known. AMMONIA COMPRESSION UNDER DIFFERENT CONDITIONS. Wet Gas. Dry Gas. Condenser pressure 113.3 15.6 69.2' .5' 16.8 13.3 50.3 .792 116.7 27.2 70.5' 14.3' 18. 19.5 53.4 1.083 36.7$ 147.3 13. 82.7' 8.2' 73.8 46.5 59.9 .632 161.3 27.5 87.7' 14.5' 88.6 74.4 70.5 .840 32.9?, Suction pressure Condenser temperature Suction temperature Horse power (indicated of steam cylinder) Refrigeration (tons per 24 hours) M. E. P in compressor .... Refrigerating- capacity per horse power (tons per 24 hours) . Economy < f high over low evaporat- APPENDIX I. 349 MEAN EFFECTIVE PRESSURE OF DIAGRAM OF STEAM CYLINDER. ^ ^ a o <* e* en ^ ^ 1^ l*>.--J>*-^-^4'H-^lti.H- o 55 505530 qp'^3 a J p p to _co o ^ *>- _n p pi -i c oc cc po t*^ co n- co w ' " w bo it- -^i H-> >>. -^i o cc b> to bs I-'*.^l)OKl The M. E. P. for any initial pressure not given in the table can be found by multiplying' the (absolute) given pressure by the M.E.P. per pound of initial, as given in the third horizontal line of the table. NOTE. This table is reprinted from " Indicating the Refriger- ating Machine," published by H. S. Rich & Co., Chicago. 350 MECHANICAL REFRIGERATION. RELATIVE EFFICIENCY OF FUELS. One cord of air dried hickory or hard maple weighs about 4,500 pounds and is equal to about 2,000 pounds of coal. One cord of air dried white oak weighs about 3,850 pounds and is equal to about 1,715 pounds of coal. One cord of air dried beech, red oak or black oak weighs about 3,250 pounds and is equal to about 1,450 pounds ol coal. One cord of air dried poplar (whitewood), chestnut or elm weighs about 2,350 pounds, and is equal to about 1,050 pounds of coal. One cord of air dried average pine weighs about 2,000 pounds, and is equal to about 625 pounds of coal. From the above it is safe to assume that two and one-quarter pounds of dry wood is equal to one pound average quality of soft coal, and that the full value of the same weight of different wood is very nearly the same. That is, a pound of hickory is worth no more for fuel than a pound of pine, assuming both to be dry. It Is important that the wood be dry, as each 10 per cent of water or moisture in wood will detract about 12 per cent from its value as fuel. TABLE SHOWING TENSION OF WATER VAPOR AT DIFFERENT TEMPERATURES IN ABSOLUTE PRESSURE, AND CORRESPOND* ING VACUUM IN INCHES OF MERCURY. Temperature. Deg; F. Absolute Pressure. Vacuum* Inches. Atmospheres. Inch of Mercury. 212 1. 30. 0. 158 0,307 9.270 20.730 140 0.1% 5.880 24.120 122 0.121 3.630 26.370 113 0.094 2.820 27.180 104 0.0722 2.166 27.834 95 0.0550 1.650 28.350 86 0.0415 1.245 28.755 77 0.0310 0.930 29.070 68 0.0229 0.687 29.313 59 0.0167 0.501 29.499 50 0.0121 0.363 29.637 41 0.0086 0.258 29.742 32 0.0061 0.183 29.817 14 0.0026 0.078 29.922 4 0.0012 0.036 29. 964 BOILING POINTS UNDER ATMOSPHERIC PRESSURE. Liquids. Fahr. (leg. Cent, deg. Liquids. Fahr. deg. Cent, deg. 5000 2760 Alcohol. 173 78 3300 1815 Ether . . 96 35 Mercury (575 352 Carbon, bi-sulphurated. . 116 47 Whale oil 630 332 Water, distilled.. 212 100 Oil of linseed .... Oil of turpentine Sulphuric acid. . . 600 357 593 570 316 180 312 300 Salt, sea water.... Water, 20$ salt... Water, 30$ salt.. . Water, 40$ saturated 213 218 222 227 101 103 105 108 Phosphorus Sweet oil . . . 557 412 292 211 Ammonia, liquid. Water, in vacuo . 140 98 60 36 320 160 Chimogene +38 33 Nitric acid 220 Ol Q 104 101 Carbonic acid 112 30 80 34 Petroleum, rectified 316 158 Benzine 187 86 APPENDIX I. 35] COMPOSITION OF COMMON WATER Chloride of sodium contains ........ Na Chloride of magnesium contains. . .Mg Chloride of calcium contains ..... Ca Chloride of potassium contains ____ K Carbonate of soda contains ........ Na O Carbonate of magnesia contains. . .Mg O Carbonate of lime contains ........ Ca O Carbonate of potassa contains ..... K O Sulphate of soda contains .......... NaO Sulphate of magnesia contains ....MgO Sulphate of lime contains .......... CaO Sulphate of potassa contains ....... K O CONSTITUENTS. 39.3 and Cl 60.6 25.28 and Cl 74.73 36.06 and Cl 63.94 52.45 and Cl 47.55 58.5 and CO 2 41.5 47.62 and C O 2 52.38 56.0 and C O 2 44.0 68.17 and C O 2 31.83 43.66 and SO 3 56.34 33.33andSO 3 66.67 41.18andSO 3 58.82 54.08 and S O 3 45.92 Carbonate of lime multiplied by 0.56=lime. Sulphate of baryta multiplied by 0.343= sulphuric acid. Phosphate of mag-nesia multiplied by 0.036= magnesia. Magnesia multiplied by 0.6= magnesium. Magnesium multiplied by 1.66=magnesia. Cubic centimeter carbonic acid multiplied by 0.002= carbonic acid in grams. C. C. nitrate of silver solution multiplied by 0.0035=chlorine in grams. Chloride of sodium multiplied by 0.39=sodium. Carbonate of soda multiplied by 0.58=soda. Chloride of potassium and platinum multiplied by 0.16= potassium. In the construction of water analysis from constituents it is advisable, as most consistent with practical requirements to com- bine chlorine with magnesium (balance of chlorine with sodium or balance of magnesia with sulphuric acid). Carbonic acid combines with lime, balance of lime with sul- phuric acid, balance of sulphuric acid with soda (or balance of carbonic acid with magnesia). When alkaline carbonates are present all the chlorine is to be combined with sodium. Magnesium carbonate and calcium sul- phate are supposed not to coexist. MILLIGRAMS PER LITER TO GRAINS PER U. B. GALLON. GRAINS PER U. S. GALLON TO MILLIGRAMS PER LITER. Milligrams per Liter. Grains per U. S. Gal. Milligrams per Liter. Grains per U. S. Gal. Grains per U. S. Gal. Milligrams per Liter. Grains per U. S. Gal. Milligrams per Liter. 1 0.058 26 1.519 1 17.1 M 444.9 2 0.117 27 1.578 2 34.2 27 462.0 3 0.175 28 .636 3 51.3 28 479.1 4 0.234 29 .695 4 68.4 29 496.2 5 0.292 30 .753 5 85.6 30 513.4 6 0.351 31 .812 6 102.7 31 530.5 7 0.409 32 .870 7 119.8 33 547.6 8 0.468 83 .929 . 8 136.9 33 564.7 9 0.526 34 1.987 9 154.0 34 581.8 10 0.584 35 2.045 10 171.1 35 598.9 11 0.643 36 2.104 11 168.2 36 616.0 12 0.701 37 2.162 12 205.3 87 633.1 13 0.760 38 2.221 13 222.5 38 650.3 14 0.818 39 2.279 14 239.6 39 667.4 15 0.877 40 2.338 15 256.7 40 684.5 16 0.935 41 2.396 16 273.8 41 701.6 IT 0.993 42 2.454 17 290.9 42 718.7 18 1.052 43 2.513 18 308.0 43 735.8 19 1.110 44 2.571 19 325.1 44 752.9 20 1.169 45 2.630 20 342.2 45 770-0 21 1.227 46 2.688 21 359.4 46 787.2 22 1.286 47 2.747 22 376.5 47 804.3 23 1.344 48 2.805 23 393.6 48 821.4 24 1.403 49 2.864 24 410.7 49 83*5 25 1.461 50 2.922 25 427.8 50 855.6 352 MECHANICAL REFRIGERATION. EXPERIMENTS IN WORT COOLING. The following tabulated experiments of the per- formance of a tubular refrigerator for wort cooling are gleaned from Engineering. The water and wort are moved in opposite directions, the former through thin metallic tubes, which are surrounded by the wort to be cooled: WORT. WATER. Mf , "5 . 13 i go2 (3 i^ jj a. 83 f 0) 05 * *2 j3 3 d g r- 1 ^ O a 1 s D^ 4J 4 f. 8 fafn-5 w Nominal I Diameter Actual Insi Diameter. Actual Out Diameter. Thickness. Internal Cii ference. External Ci ference. f! Internal Ai External Ai Length of Containin Cubic Foo S3 p.tc 13 I* In. In. In. In. In. In. Ft In. In. Ft. Lbs. N 0.205 0.465 0.100 0.644 1.461 8.21 0.0329 0.1694 4377 0.29 M 0.294 0.54 0.123 0.924 1.697 7.07 0.0678 0.2290 2124 0.54 0.421 0.675 0.127 1.323 2.121 5.66 0.1394 0.3573 1033 0.74 K 0.542 0.84 0.149 1.703 2.639 0.2307 0.5542 624.2 1.09 0.736 1.05 0.167 2.312 3.299 3.67 0.4254 0.8659 338.7 1.39 1 951 1.315 0.182 2.988 4.131 2.90 0.7103 1.3582 202.7 2.17 l/^ 1.272 1.66 0.194 3.990 5.215 2.30 1.2707 2.1642 113.3 3.00 114 1.494 1.90 0.203 4.695 5.969 2.01 1.7530 2.8353 82.15 3.63 2 1.933 2.375 0.221 6.075 7.461 1.61 2.9345 4.4302 49.72 5.02 24 2.315 2.875 0.280 7.304 9.032 1.33 4.1989 6.4918 34.28 7.67 3 2.892 3.5 0.304 9.085 10.996 1.09 6.5688 9.6211 21.91 10.25 a 1 /, 3.358 4.0 0.321 10.550 12.566 0.931 8. 7561 12.5664 16.23 12.47 4 3.818 4.5 0.341 11.995 14.137 0.849 11.4*08 15.9043 12.56 14.97 5 4.813 5.563 0.375 L5.121 17.477 0.687 18.193 24.3010 7.915 20.54 6 5.750 6.625 0.437 18.064 20.813 0.576 25.967 34.4496 5.542 28.58 APPENDIX II. 353 APPENDIX II. PRACTICAL EXAMPLES. INTRODUCTORY REMARKS. The following practical examples, problems and ques- tions have been discussed for a two-fold purpose. In the first place their object is to give to those not accustomed to the use of books an idea as to how the Compend may be utilized, and to show them in particular that the formulas may be referred to by any ma.n of ordinary acquaintance with the rules of common arithmetic; and to also show them how most questions can be answered without the use of such formulae, by referring to more convenient rules or tables in the book or appendix of tables. In the second place these problems are calculated to answer such questions as frequently occur in the refrig- erating practice, and to discuss certain questions in a more direct way than it was practicable to do in the body of the book. By carrying out the formulae in numerical quantities in this appendix it was also intended to please those who profess a great preference in favor of formulae writ- ten altogether in figures, and not with figures and letters of the alphabet mixed. It is also probable that by studying the solutions in this appendix more carefully they will discover the reasons why formulas are thus written, viz. : In order to make the necessary distinction between constant numerical quantities which never change, and which therefore are given their constant numerical value in the formula and between the quanti- ties which change with every example and which there- fore are given in letters of the alphabet, for which the different values are to be inserted in every different example, FORTIFYING AMMONIA CHARGE. Q. How many pounds (x} anhydrous ammonia should be added to 600 pounds of ammonia liquor in absorption machine showing 20 Beaume (scale show- ing 10 in pure water) to make it 26 Beaume" ? From table on page 97 we find 20 Beaume to corre- spond to 17 per cent, and 26 Beaume to correspond to about 28 per cent of ammonia; hence in formula on page 285, m is equal to 600, a = 20, b = 28, and therefore x = 600(28 17) 600 Xll 1QO _ 28 = 72 = 97 - 6 Pounds. 354 MECHANICAL REFRIGERATION. EXAMPLES ON SPECIFIC HEAT. QUESTION. What amount of heat must be abstracted from 1,000 pounds of beer wort of 14 per cent to reduce its temperature from 70 to 40 F. ? Specific heat c of wort from page 158 = 0.902 = 0.9, according to page 16: S = cxtXto = 0.9X (7040) X 1000 = 0.9 X 30 X 1000 = 27000 units. Q. What will be the final temperature T,if t,000 pounds of beer wort of 14 per cent and of a temperature of 180 degrees are mixed with 1,200 pounds of water of 60 F.? In accordance with page 17 we find l t l s l 1200 X 60 X 1 + 1000 X 180 X 0.9 t 1200X1X1000X0.9 23400 -111 4Q F 2100 ' EVAPORATIVE POWER OP COAL. Q. If a lignite contains 60 percent of carbon (C) and 5 per cent of hydrogen (T), what will be its evaporative power (e) expressed in pounds of water? From page 37 we find e= .15 (G -f 4.29 H)= 0.15 (60 + 5 X 4.29) 12.21 pounds. CAPACITY OF FREEZING MIXTURE. Q. How many pounds of ammonia nitrate must be dissolved in so many pounds of water to obtain a theoreti- cal refrigerating effect equal to one ton ice melting capacity = 284,000 units? On page 32 we find that 1 pound will reduce the tem- perature from 40 to 4, which is equivalent to a refrigerat- ing effect of 2 X (40-4) = 72 units if we assume the spe- cific heat of the solution equal to that of water = 1. Hence 28|oofl about 4,000 pounds of the salt must be dissolved in 4,000 pounds of water to obtain the required effect the" oretically; practically it would take a great deal more. EXAMPLES ON PERMANENT GASES. Q. If the volume Fof a gas is ten cubic feet at a pressure of eighteen atmospheres and a temperature of 40, what will be its volume F t if expanded to a pressure of one atmosphere and a temperature of 80 ? Examples of this kind occur quite frequently, and their study will- be found very instructive and profitable. APPENDIX II. 356 The formula at bottom of page 48 gives _ 18 (-80+461) __ 18X381 - 1(40+461) TX60T" Q. What volume x in cubic feet is occupied by 180 cubic feet of a permanent gas if its temperature is reduced from 40 to 80 F.? According to page 55 the volume of a gas is propor- tional in its absolute temperature. Hence we have 180 : x = (40 + 461) : (80 -f 461) = 501 : 381 or x = 180 * 381 = 137 cubic feet. oU-L EXAMPLES SHOWING USE OF GAS EQUATION. Q. What will be the pressure of a confined volume of air at a temperature 45 if its pressure at 32 F. is equal to one atmosphere? According to the equation for perfect gases, page 55,is: T 45 -f 461 p v = |gg = ~ or v remaining unit. C(\f* p = -r^ = 1.03 atmospheres or thereabouts. 47O Q. What will be the volume of one cubic foot of air if heated at constant pressure from 32 to 45 F., its press- ure at the former temperature being one atmosphere? According to the same equation we find T 45-4- 461 P V = 493 == 493 r P remainin g uni t- r.f\a v=m = 1.03 cubic feet. Q. If the volume of a confined body of a permanent gas be one cubic foot at the temperature of 32 and at a pressure of one atmosphere, what will have to be its tem- perature T in order that it may occupy a volume of one- half cubic foot at a pressure of four atmospheres? The same equation answers the question, viz.: P v== 491J r T=493 P v = 493X4X^ = 986 F. absolute. or 986 461 = 525 F. WORK REQUIRED TO LIFT HEAT. Q. What amount of work must be expended theo- retically by a perfect refrigerating machine to withdraw 284,000 units of heat (one ton refrigeration) from a refrig- 356 MECHANICAL REFRIGERATION. erator at temperature of 10 if the temperature ia the condenser is 90 ? Prom the equation, page 71, * |r= H(T i; -T.) 284000 (90-10) JL O (^Ol-f-IUj The work is here expressed in heat units, which are eo'uvaleatto:. 49,000 X 772 = 37,830,000 foot-pounds (page 346) or to REFRIGERATING EFFECT OF SULPHUROUS ACID. Q. What is the theoretical refrigerating effect r of one pound and of one cubic foot of sulphurous acid if used in a compression machine, the temperature in re- frigerator coils being 5 and in condenser coils 95 F.? The equation r = h l (t t t )s, on page 115, applies also for sulphurous acid, for which we find /i, =171 units (page 250) and s = 0.41 (page 250) ; hence r = 161 (95 5)0.41 161 37 = 124 units. From same table we find the weight of one cubic foot of sulphurous acid at 5 equal to 0.153 pounds; hence the refrigeration of one cubic foot is 124X0.153 = 18.97 units. REFRIGERATING CAPACITY OF A COMPRESSOR. Q. What is the refrigerating capacity of a double- acting compressor, 70 revolutions per minute, diameter 9^ inches and stroke 16^ inches, temperature in re- frigerator coil 5 and in condenser coil 85 F.? The compressor volume C per minute after formula on page 303 is C=d* X I X m X 0.785 = 9%* X 16& X 0.785 X 70. From table on page 314 we find 9% 2 X 0.785 = 76.58. Hence C = 76.58 X 16.5 X 70 = 88410 cubic inches. The compressor being double-acting, this is equal to l= 102 cubic feet. From table on page 125 we find that 3.34 cubic feet of ammonia must be pumped per minute, at above named condenser and compressor temperature to produce a refrigerating effect of one ton in twenty-four hours, hence APPENDIX II. 357 'the above compressor represents a theoretical refrigerafr ing efficiency of 102 .= 30.5 tons. 3.34 SECOND METHOD OF CALCULATION. The actual refrigeration will be from 15 to 20 pei cent less, or equivalent to about 25 tons (commercial capacity ?); see table page 302, according to which the nominal daily refrigerating capacity is -^ = -^- = 25.5 tons. 4 4 The agreement between this amount and the amount found by the first calculation holds good only for the temperature selected; otherwise the last rule affords only a crude approximation. THIRD METHOD OF CALCULATION. The theoretical refrigerating effect R of this com- pressor can also be calculated after the formula on page 118 E = C X 60 X r v We find, according to formula on page 115 and table on page 94, r = h, (t t t ) s = 552.43 ( 85 5) I = 552-80 = 472 units, and v =8.06 (page 94) B = 102 x 60 x 472 units or in tons per day- o.Uo 102 X 60 X 472 X 24 8 X 284.000. = 29 - 8t C686 pounds of steam per hour. h B = 886 (at pressure in boiler 100 absolute or 85 pounds gauge pressure). To this should be added about ^ to allow for steam to run the ammonia pump, so that the whole would amount to about 900 pounds per hour. COLD STORAGE EXAMPLES. Q. What is the refrigeration B required for a local storage room 40X50x10 if each day about 30,000 pounds of fresh meat (about 120 hogs) are placed in the same at a temperature of 95 to be chilled to a temperature of 35, if the temperature of atmosphere is to be 85 F.? METHOD OF CALCULATION. The side walls of room 2x50x10+2x40x10=1,800 sq.ft. The ceiling and floors 2X40X50 =4,000 " Total. . . . .' ....................... 5,800 sq.ft. If we take n as 3 all around (assuming an average de- gree of insulation (see page 181), we have frigeration per day to keep the room at the desired temperature. The additional refrigeration to chill the meat, assum- ing its specific heat to be 0.8, we find (page 183) P( < t ) .30000(95 35) = ""355000 "" 355000 5 tons, which makes a total refrigeration of 8.1 tons required. For closer estimates the rules on pages 181 and 182 may be used. APPROXIMATE ESTIMATE. The cubic contents of the room are equal to 20,000 cubic feet, and in accordance with the rules on page 173 from fifty to 100 units (say seventy-five units in this case) are allowed per cubic foot, and in addition to that about 50 per cent more for chilling, which amounts to about 110 units in all per cubic feet, or a daily refrigeration of 20000 X 110 284000 = 8 tons in round figures. APPENDIX II. 361 Tor opening doors, for windows, etc., about 10 to 15 per cent extra refrigeration may be allowed, making the total about nine tons refrigerating capacity per day. See also rules on page 212 and 213. PIPING REQUIRED. Q. What will be the amount of 2-inch pipe direct circulation required for the above room and purpose? In accordance with rule on page 128 we assume that one square foot of pipe will convey about 2,500 units of refrigeration; this is equal to 1.6 foot of 2-inch pipe (table on page 129), hence to distribute nine tons in twenty-four hours the pipe required will be 9X284000X1.6 _ lm f ^ o( 2 .. nch ZoUU According to another rule, given on page 212, one running foot of 2-inch pipe is allowed for thirteen cubic feet chilling room capacity, in accordance with which 20 000 V^ = 1^540 feet or thereabouts of 2-inch pipe would IB be required. After still another rule, given on page 212, we find that six feet 2-inch pipe are allowed per hog slaughtered in chilling room; according to this rule we would only re- quire 720 feet of 2-inch pipe for above room, but the rule from which this result is obtained applies to large instal- lations having over a hundred times the capacity contem- plated in the example as given and calculated above. EXAMPLES ON NATURAL GAS. Q. What amount of refrigeration and work can be produced by natural gas expanding adiabatically from a pressure of 255 pounds (seventeen atmospheres) to a pressure of fifteen pounds (one atmosphere) absolute pressure, and to a volume of 1,000,000 cubic feet at the ordinary temperature and pressure? TEMPERATURE AFTER EXPANSION. If we assume the initial temperature of the gas to be 70 = 70 + 461 = 531 absolute we find the temperature T 2 of the gas after expansion after the rule on page 257, viz: fc 1 1.41 1 0.291 " 362 MECHANICAL REFRIGERATION. log. T t = log. 531 X 0. 291 (log. 1 log. 17) 2.72510.6432 = 2.0819. !T 2 = num. log. 2.0819 = 121 absolute = 461 121 = . 340 F. REFRIGERATING CAPACITY. The theoretical refrigeration H produced by 1,000,000 cubic feet expanded in this manner if the gas leaves the refrigerator at the temperature T of 5 = 466 absolute is found after the formula on page 257. H=>mkc (T T 2 )=-mfcc(466 121) c=- 0.468 (page 47) m = 0.0316 pounds (page 233 coal gas) hence H= 0.0316 X 0.468 X 1.41 X 345 = 7.0 units per cubic foot or 7,000,000 units per 1,000,000 cubic feet, which is equivalent to a theoretical refrigerating capacity of about twenty-five tons. The actual ice making capacity would probably be less than ten tons per day. WORK DONE BY EXPANSION. The amount of work, Wm, that can be obtained tkeoretically by the adiabatic expansion to 1,000,000 cubic feet of the gas is expressed by the formula = (T T 2 ) = 0.0316 X 0.468 X 1.41 (531 121) A. . X 772 = about 6600 foot-pounds per cubic foot, or for 1,000,000 cubic feet per day According to this calculation the power to be gained would be of considerably more consequence than the ice, but it must not be forgotten that these are theoretical calculations which are naturally greatly reduced in prac- tical working, not to speak of possible difficulties con- nected with the same. SIZE OF EXPANDING ENGINE. As the expanded gas leaves the expanding engine at the temperature of 121 absolute, its volume x is less in the following proportion 1000000 : x = 531 : 121 (page 55) 121 X 1000000 cubicfeet 531 APPENDIX II. 863 This is the volume over which the piston of expand- ing engine must sweep in one day. If it is double-acting and makes fifty revolutions a minute the size of tiie cylinder must be If the stroke be two feet the area of piston must be 0.8 square feet. EXPANSION WITHOUT DOING WORK. Q. What amount of refrigeration can be produced by natural gas expanding from a pressure of 255 pounds, absolute, to a volume of 1,000,000 cubic feet at the atmospheric pressure without doing work? REFRIGERATION OBTAINABLE BY EXPANSION ALONE. For the sake of simplicity we neglect the contraction of the gas due to reduction of temperature, and allow the theoretical refrigeration to be equivalent to the external work, E, done by the expanding gas, which can be found by the formula for steam on page 106 v representing the final volume and v t the original volume of the expanding gas, and calculated for one cubic foot; hence E = 15 ( ^ 2 "~ 1) = 0.31 units per cubic foot. or 310,000 units for 1,000,000 cubic feet of gas, of which only a fraction could be utilized for ice production, which would probably be less than one-third ton per day. CALCULATION OF REFRIGERATING DUTY. Q. A machine is required to cool water from 55 F. to 40 F. during part of. the day, and to keep a cold storage at 15 F. at other part of the day. What indicated horse power steam engine will be required to work compressors to extract 3,000,000 13. T. U. per hour from the water at above temperatures, and what size compressors, with number of revolutions per minute ? What B. T. U. per hour would same machine extract at same speed when working on the cold storage, and what would then be its indicated horse power ? Condensing water at 60 and leav- ing condenser at 70 F. 364 MECHANICAL REFRIGERATION. If we assume that you work by direct expansion, the temperature of the expanding ammonia would have to be about 10 lower than the water after it is cooled, i. e., 30; consequently by using the latent heat of vaporiza- tion at that temperature, as we find it in table on page 94, viz., 536, and formula on page 115 of Compend we find r = 536 (7030) 1 = 496 units, which is the refrigerating effect of one pound of ammonia, when the temperature of the refrigerator is 30 and that of the condenser 70, the specific heat of the ammonia being 1. The amount of ammonia to be evaporated per minute is, therefore 3,000,000 496 X 60 = 101 pounds. From same table on page 94, we find volume of one pound of ammonia vapor at 30 = 4.75 cubic feet, con- sequently the compressor capacity per minute will have to be 101 X 4.75 = 480 cubic feet in round numbers. If we add to this 20 per cent for clearance losses by radiation, etc., we require an actual compressor capac- ity of 576 cubic feet per minute. If we assume that the work is to be done by one double-acting compressor, making, say, seventy revolutions per minute, we require a compressor having the cubic capacity of =J^ii ='4.2 cubic feet. (& X A If we distribute this capacity over two compressor cylinders each one has to have a volume of 2.1 cubic feet. Taking the diameter of each of them at fifteen inches the area is (1.25* X 0.785) 1.227 cubic feet, and the stroke will have to be 2.1 1.227 17.12 inches. If we start from a different given stroke and num- ber of revolutions, as we probably shall, the diameter changes accordingly, after the foregoing simple rule. If a single double-acting compressor making fifty revolutions were to do the work, its dimensions, calcu- lated on the same basis as above, would be twenty inches diameter by 31^ -inch stroke. APPENDIX II. 365 The work of the compressor is found after the for- mula on page 119 : W =0.0234 WK horse power; or ^=0.0234-^^-71! X^=0.0234X 7 ~Q X 536X101=104 horse power. And the horse power of engine, after rule on page 121 of Compend, is found to be 104X1.4= 145.6 horse power. The same two compressors, if required to do duty in a cold storage plant, would probably have to run with a temperature of 5 F. in refrigerator. In this case (their cubic capacity being 576 cubic feet per minute) their re- frigerating capacity in tons per day is found by the for- mula on page 303 of Compend, viz.: 576(54670+5) n , n mx^w^- 212 tons m round figures (h t and v being found from table on page 94). Or in thermal units per hour 212 x^oro, 2aooooo Unit8- This is the theoretical capacity; to bring it on a prac- tical basis, we have to subtract 20 per cent, as we did in the case of water cooling before this yields 2500000500000 ^= 2000000 units per hour actual refrigerating capacity for cold storage. To find the horse power of the compressor in this case we find the amount of ammonia to be circulated in a minute, as before, viz.: r = 546 _ (70 15) 491, and ** Placing this value in the equation from page 119, as before, we find W 4= 0.0234 X 7 ^~ 5 X 546 X 68 118.7 horse power; and the horse power of engine 118.7 X 1.4 166 horse power. These horse power are calculated from the amount of ammonia theoretically required, and about 15 to 25 per cent should he added to bring them within practical range. We have also assumed that the temperature in condenser is that of outflowing condenser water, when in fact it should be taken 5 higher. 366 MECHANICAL REFRIGERATION. CALCULATING ICE MAKING CAPACITY. Q. What is the ice making capacity of two single- acting compressors 7X12 inches, 100 revolutions per minute? The capacity in cubic feet, <7, for each compressor per minute, according to formula on page 117 of Com- pend, is C=r 2 X 3.145 X6X m 7 2 X 3.145 X 12 X 100 9ft . . . f - pr^g = 26.7 cubic feet, or for both compressors, 26.7 x 2 = 53.4 cubic feet, which under general conditions, when no back pressure, etc., is mentioned, has been calculated to be equivalent to 53 4 -j 13.35 tons of refrigerating capacity in twenty- four hours (see page 118 of Compend), and of this from i 4 o to ! 6 g is available actual ice making capacity, which accordingly is about seven tons per day (more or less; see page 144 of Compend). VOLUME OF CARBONIC ACID GAS. Q. What is the volume of one pound of carbonic acid gas at a pressure of thirty pounds and at a tem- perature of 50? The formula that applies here is given on page 48 of the Compend, viz.: Fpfo + 461) If in this formula we insert for V the volume of one pound of carbonic acid gas at the atmospheric pressure, viz., 8.5 cubic feet, and forp the pressure of the atmos- phere, viz., 14.7 pounds, and for t the temperature of 32 F. this formula becomes: T n = 8.5 (461 + *)14.7 115 + 0.25 t t 493 p 1 P! Hence the volume F 1 of one pound of carbonic acid gas at any given temperature and pressure, say at an ab- solute pressure of thirty pounds, and a temperature of 50, is found by inserting these quantities in the fore- going formula: Tri 115 + 0.25X50 127.5 V j^j - ' -- 3Q = 4. 25 cubic feet. For apparent reasons the numerical results of above examples have been rounded off in most cases. APPENDIX II. 367 HOUSE POWER OF STEAM ENGINE. Q. What is the horse power of a steam engine the piston of which has a diameter of 12 inches, a stroke of 30 inches at 90 revolutions a minute if the gauge pressure of the steam is 80 pounds, cut-off fc? To calculate the horse power in this case we have to find the mean effective pressure by means of an indi- cator diagram, as shown on page 297. If it is imprac- ticable to obtain a diagram we take the mean average pressure as we find it in table on page 349, which is 49.4 pounds, or .50 pounds in round numbers, in this case. Multiply the same by the area of the piston in square inches and the speed of the piston in feet per minute, and divide the product by 33,000 (foot-pounds of horse power per minute. See table on page 347). The area of piston in square inches we find, accord- ing to rule given on page 309, equal to 12* X0.7854=144XO. 785=113.0, which is also given direct in table on page 314. The piston speed is 30X9 X2 450 feet per minute. Hence the horse power . This is the indicated horse power, the net effective horse power being the indicated horse power less the friction of the engine. The table on Corliss engine, on page 340, gives the indicated horse power of an engine of above description at 54, this difference being probably due to a difference in the mean effective pressure and to an allowance for piston space having been made in the latter case. WORK OF COMPRESSOR. Q. What is the work of compression done by a double-acting ammonia compressor 9 inches in diameter, 15 inches stroke at 70 revolutions per minute? The back' pressure is 28 pounds and the condenser pressure 115 pounds. This problem is calculated on the same principles as the foregoing example; but, as in that case, the proper way is to obtain the mean effective pressure from an indicator diagram. If we use the table on page 298 instead we find the mean pressure in this case at 52.6 368 MECHANICAL REFRIGERATION. pounds. The area of piston, by table on page 314, is C3.6 square inches, and its travel per minute equal to 2X70X15 ^ - =116 feet; hence the work done by the compressor is equal to 63.6X116X52.6 - w nnn -- =11.6 horse power. oo,UUU This is the indicated horse power of the work done by the compressor. In order to find the indicated horse power (of an engine) required to do this work we must add to the above the work required to overcome the fric- tion in the compressor as well as in the engine itself. CALCULATION OF PUMP. Q. How many revolutions must be made by a single- acting pump having a piston of 4 inches in diameter and 12 inches stroke in order to force 400 gallons of water 60 feet above the level of pump per hour, and what will be the power required to do this work ? According to table on page 322 the displacement by this pump for each stroke is 0.653 gallons ; hence - = 605 strokes; or, in round numbers, 600 strokes must be made per hour; and as the pump is single-acting this corresponds to 600 revolutions per hour, or ten per minute. The work done by this pump in lifting the water may be calculated the same way as the work done by a compressor, by simply inserting, instead of the mean average pressure, the pressure corresponding to a water column of 60 feet in height, viz. : 26 pounds in round numbers, as per table on page 326. WATER POWER. Q. 1. What is the power of a water fall twenty feet high and 300,000 cubic feet of water per minute ? 2. What amount of coal and steam respectively would give the same power during twenty-four hours ? In accordance with page 108 one cubic foot of water weighs 62.5 pounds; hence by using rule on water power given on page 43, we find the theoretical power of the water fall in question equal to 300 ' 000 *nn XX2 = 12,400 horse power. OdjUUU Of this theoretical effect may be utilized 30 to 75 per cent by water motors, according to construction, etc.; 50 to APPENDIX II. 369 75 per cent by turbines ; 70 to 80 per cent by water press- ure engines (generally not used for falls less than fifty feet in height). Taking 50 per cent as a safe basis, the actual work that can be expected from the fall would be equal to 12 400 ^ = 6,200 horse power This power would of course still be correspondingly reduced if the mechanical power of the water motor had to be converted into electricity, to be transmitted to a distant locality, there to be converted into mechanical power again. Leaving this out of the question, and assuming that electricity was the form of energy wanted, we find, from page 108 of the Compend, that from fifteen to thirteen pounds of steam will produce a horse power per hour, and that a pound of average coal will make about eight pounds of steam; hence a horse power will require not over two pounds of coal per hour with a good engine, and therefore 6,200 horse power may be estimated equivalent to 6,200x24x2=297,600 pounds of coal in twenty-four hours. Allowing fifteen pounds of steam per horse power, the actual power of the water fall would be represented by 6,200X15=93,000 pounds of steam per hour. With first-class machinery it would take less steam and coal. MOTIVE POWER OF LIQUID AIR. Q. What is the amount of work expressed in foot- pounds and in horse power that can be done by one pound of liquid air while expanding or volatilizing at the con- stant temperature of 70, this being the average atmos- pheric temperature V According to page 260, we find the work, TFi, in foot- pounds, which can be done theoretically by the isothermal expansion of F 1} cubic feet of liquid air to the volume of V cubic feet and the pressure P (in pounds per square foot) after the formula W t = P V X 2.3026 by - In the problem on hand we have P = 2,117 pounds. F , the volume of one pound of liquid air, is not exactly known but , the ratio of the volume after and before 370 MECHANICAL REFRIGERATION. expansion, is about 800, and V t the final volume of one pound of air in cubic feet at 70 P. and at atmospheric pressure is equal to about 13.34 cubic feet. Hence the formula developes into 0^=2,117X13.34X2.3020 log. 800=188,800 foot-pounds. (Log. 800 being equal to 2.9031. See table on page 316.) In order to express this effect in horse power, the time in which the pound of air is to expand should be stated also. Assuming that it takes place at the rate of one pound of liquid air expanding per minute, the horse power would be 188,800 g 3 QQQ = 5.72 horse power. This is the theoretical figure; practically, a reduction would have to be made for friction, etc. MOISTURE IN COLD STORAGE. Q. Assuming that 34 is the proper temperature for an egg storage room, what is the proper percentage of moisture which it should contain, and how should the wet bulb thermometer of a hygrometer or sling psychrometer stand in order to indicate that percentage of moisture ? According to Cooper the percentage of moisture for cold storage rooms, especially for eggs, should vary with the temperature as follows : Temperature in Degrees F. Relative Humid- ity, Per Cent. Temperature in Degrees F. Rel'tive Humid- ity, Per Cent. 28 29 30 31 32 33 34 80 78 76 74 71 69 67 35 36 37 38 39 40 65 62 60 58 56 53 Therefore for a storage temperature of 34 the moisture, or relative humidity, should be 67 per cent (100 per cent corresponding to air saturated with moisture), and by referring to table on- page 112 we find that this corresponds to a difference between the dry and the wet bulb of 3.5. Hence the wet bulb thermometer should show 343.5=30.5. CARBONIC ACID VS. AMMONIA. Q. We would like to ask you for some information on ice machines, as to how the carbonic anhydride ice APPENDIX II. 371 machines are in comparison with the ammonia ice ma- chines. The carbonic anhydride machine people claim their machine far superior to the ammonia machine. They also claim that carbonic anhydride has more freez- ing power than ammonia. Is this in accordance with your statement in Ice and Refrigeration (see same, page 247 of Compend) or not? This question, which was directed to the author of the Compend personally, would indicate that his state- ments with reference to this matter were misunderstood, or at least apt to misconstruction. The superiority of the carbonic acid machine would of course tally with 4,300 and 3,700 calories per horse power; but these figures were quoted by the author as phenomenal, in fact as mere claims, unsupported, so far at least, by any au- thentical tests. The author of the Compend has taken great pains to find any tests supporting such claims, or to find a carbonic anhydride machine which would give some such results in actual practice, but so far has failed to find any. On the contrary, we have come to the con- clusion that the results of the practical comparative tests given in the tables on page 247 of Compend have not been materially exceeded so far, at least hot with machines without expansion cylinder, and only such are in the market at present, as far as we know. As a result of the present status of the theoretical aspect of the questions it appears that at temperatures of 70 before the expansion valve and 20 in refrigeration coils it will take 1.2 horse power in a carbonic anhydride machine to produce the same refrigeration as one horse power in an ammonia refrigerating machine. Hence the advantages of the carbonic acid machine must be looked for in other directions rather than in that of greater effi- ciency. 372 MECHANICAL REFRIGERATION. APPENDIX III. LITERATURE ON THER- MODYNAMICS, ETC. a.-BOOKS. ATKINSON, E. Ganot's Elementary Treatise on Physics Experk mental and Applied; New York, 1883. BERTHELOT, E. Mecanique Chimique, two vols. ; Paris, 1880. BEHREND, GOTTLIEB. Eis und KalteerzeugungsMaschinen; Halle a.S., 1888, CARNOT, N. L. S. Reflections on the Motive Power of Heat; trans- lated byThurston; New York, 1890. CLAUSIUS, R. Die Meohanische Warmetheorie, three vols.; Braun- schweig, 1891. CLARK D. KINNEAR. The Mechanical Engineer's Pocket Book; New York. 1893. COOPKR, MADISON. Eggs in Cold Storage; Chicago, 1899. DUEHRINQ, E. Principien der Mechanic; Leipzig, 1877. EWING, S. A. The Steam Engine and Other Heat Engines; Cam- bridge, 1884. EDDY, HENRY T. Thermodynamics; New York, .1879. FARADAY, M. Conservation of Force; London, 1857. FISHER, FERDINAND, DR. Das Wasser; Berlin, 1891. GRASHOF, F. HydraulikNebstMechanischeWaermetheorie; Leip* 3ig, 1875. GAGE, ALFRED P. A Text Book on the Element of Physics; Bos- ton, 1885. GIBBS, WILLARD J. Thermodynamisches Studien, translated by W. Ostwald ; Leipzig, 1892. HELM, G. Energetik DerChemischenErscheinungen; Leipzig,1894. HSLM, GEORGE. Die Lehre von der Energie; Leipzig, 1887. HELMHOI/TZ, H. Erhaltung der Kraft; Berlin, 1847. HKLMHOLTZ, H. Wechselwirkung der Naturkraef te ; Koenigsberg 1854. HERING, C. Principles of Dynamo Electric Machines; New York, 1890. HIRN, G. A. Equivalent Mecanique de la Chaleur; Paris, 1858. HIRN, G. A. Theorie Mecanique de la Chaleur; Paris, 1876. HOFF, J. H. VAN'T. Chemische Dynamik; Amsterdam, 1884. JOULE, J. P. Scientific Papers; London, 1884. JEUFFRET, E. Introduction a la Theorie de 1'Energie; Paris, 1883. KIMBALL, ARTHUR L. The Physical Properties of Gases; Boston and New York, 1890. KENNEDY, ALEX. C. Compressed Air; New York, 1892. LEDOUX, M.-Ice Making Machines: New York, 1879. LEAR, VAN J. J. Die Thermodynamik in der Chemie; Leipzig, 1893 LEASK, A. R. Refrigerating Machinery; London, 1895. LEDOUX, M. Ice Making Machines, with Additions by Messrs. Denton, Jacobus and Riesenberger; New York, 1892. LoRKNZ.HANS.-Neuere Kuehlmaschinen; Muenchen und Leipzig; 1899 MARCHENA, R. E. DE. Machines frigoriflques a gas liquiflable; Paris, 1894. MAYER, J. R. The Forces of Inorganic Nature, 18*2. Translated by Tyndall. MAYER, J. R.-Mechanik der Waerme; Stuttgart, 1847. APPENDIX m. 873 MAYER, J. R. Bemerkungen ueber das Mechanische Equivalent der Waerme; Heilbronn und Leipzig-, 1851. MAXWELL, CLERK J. The Theory of Heat; London, 1891. NYSTROM'S Pocket Book of Mechanics and Engineering; Phila- delphia, 1895. OSTWALD, W. Die Energie und ihre Wandlungen; Leipzig, 1888. OSTWALD, W. Lehrbuch der allgemeinen Ohemie, vom Stand. punkt der Thermodynamik, 3 Vols; Leipzig, 1891-94. PLANCK, MAX. Ueber der Zweiten Hauptsatz der Mechanischen Waermetheorie; Muenchen, 1879. PLANCK, MAX. Grundriss der Thermochemie; Breslau, 1893. PLANCK, Max. Erhaltung der Energie; Leipzig, 1887. PARKER, J. Thermo-Dynamics; Treated with Elementary Math ematics; London, 1894. PECLET, E. Traite de la Chaleur, two vols.; Paris, 1843. PICTET, RAOUL. Synthese de la Chaleur. Geneve, 1879. PEABODY, C. H. Tables on Saturated Steam and Other Vapors; New York, 1888. POPIN, M. T. Thermodynamics; New York, 1894. REDWOOD, J. Theoretical and Practical Ammonia Refrigeration ; New York, 1895. RICHMOND, GEO. Notes on the Refrigerating Process and its plac- in Thermodynamics; New York, 1892. RONTGEN, ROBT. Principles of Thermodynamics; translated by Du Bois; New York, 1889. RUHLMANN, RICHARD. Handbuch der Mechanischen Waerme Theo- rie, two vols. ; Braunschweig, 1876. SCHWACKHOEFER, FRANZ. Vol. II, des Officiellen Berichts der K. K. Osterr. Central Commission fiir die Weltausstellung in Chicago, im Jahre 1893; Wien, 1894. SCHWARZ, ALOIS. Die Eis und Kuehlmaschinen; Muenchen und Leipzig, 1888. SKINKLE, EUGENE T. Practical Ice Making and Refrigerating; Chicago, 1897. TAIT, P. G. Sketch of Thermodynamics; Edinburgh, 1877. TAIT, P. G. Vorlesungen ueber einige neuere Fortschritte in der Physik; Braunschweig, 1877. THURSTON, R. H. The Animal as a Machine and a Prime Motor and the Laws of Energetics. THURSTON, R. H. Engine and Boiler Trials and of the Indicator and Prory Brake; New York, 1890. THURSTON, ROBT. H. Heat as a Form of Energy; Boston and New York, 1890. THOMSEN, I. Thermochemische Untersuchungen, three vols.; Leipzig, 1883. THOMSON, SIR W. Lectures on Molecular Dynamics; Baltimore, 1884. TYNDALL, J. Heat Considfired as a Mode of Motion; London, 1883. VERDET, E. Theorie mecanique de la Chaleur; Paris, 1872. VOHHBES, GARDNER T. Indicating the Refrigerating Machine; Chicago, 1899. WALD, F. Die Energie und Ihre Entwerting; Leipzig, 1889. WALLIS-TAYLOR, A. J. Refrigerating and Ice-Making Machinery; London, 1896. WOOD, DE VOLSON. Thermodynamics, Heat, Motors and Refrig- erating Machines; New York, 1896. WAALS, VAN DER. Die Continultat des Gasformigen undFliissigen Zustandes; Leipzig, 1881. ZENNER, GUSTAVB. Technische Thermodynamik, two vols. ; Leip- zig, 1890. 374 MECHANICAL REFRIGERATION. b.-VATALOGUES. American Insulating Material Manufacturing Co. (Granite Rock Wool and Insulating Materials), St. Louis, Mo. Arctic Machine Manufacturing Co. (Ice Making and Refrigerating Machinery, Ammonia compression system), Cleveland, Ohio. Austin Separator Co. (Oil Separators), Detroit, Mich. Barber, : A. H., Manufacturing Co. (Ice Making and Refrigerating Machinery, Ammonia compression system), Chicago, 111. Buffalo Refrigerating Machine Co. (Ice Making and Refrigerating Machinery, Ammonia compression system), Buffalo, N. Y. Carbondale Machine Co. (Ice Making and Refrigerating Machin-. ery, Ammonia absorption system), Carbondale, Pa. Case Refrigerating Machine Co. (Ice Making and Refrigerating Machinery, Ammonia compression system>, Buffalo, N. Y. Challoner's, Geo., Sons Co. (Ice Making and Refrigerating Machin- ery, Ammonia compression systenx), Oshkosh, Wis. Cochran Company (Ice Making and Refrigerating Machinery, Carbonic anhydride system), Loraih, Ohio. De La Vergne Refrigerating Machine Co. (Ice Making and Refrig- erating Machinery, Ammonia compression system), New York City, N. Y. Direct Separator Co. (Water and Oil Separator), Syracuse, N. Y. Farrell & Rempe Co. (Wrought Iron Coils and Ammonia Fittings), Chicago, 111. Featherstone Foundry and Machine Co. (Ice Making and Refriger- ating Machinery, Ammonia compression system, and Corliss Engines), Chicago, 111. Frick Co. (Ice Making and Refrigerating Machinery, Ammonia compression system, and Corliss Engines), Waynesboro, Pa. Grifford Bros. (Ice Elevating, Conveying and Lowering Machinery), Hudson. N. Y. Gloekler, Bernard (Cold Storage Doors and Fasteners), Pitts- burg, Pa. Ball, J. & E., Limited (Ice Making and Refrigerating Machinery, Carbonic anhydride system), London, E. C., England. Harrisburg Pipe and Pipe Bending Co., Limited (Coils and Bends, and Amm6nia Fittings and Feed-water Heaters), Harrisburg, Pa. aaslam Foundry and Engineering Co. (Ice Making and Refrig- erating Machinery, Ammonia absorption system), Derby, England. Hohmann & Maurer Manufacturing Co. (Thermometers), Roches- ter, N. Y. Hoppes Manufacturing Co. (Water Purifiers and Heaters), Spring- field, Ohio. Hoppes Manufacturing Co. (Steam Separators and Oil Illumina- tors), Springfield, Ohio. Kilbourn Refrigerating Machine Co., Limited (Ice Making and Refrigerating Machinery, Ammonia compression system), Liverpool,. England. APPENDIX III. 375 Kroeschell Bros. Ice Machine Co. (Ice Making and Refrigerating Machinery, Carbonic anhydride system), Chicago. 111. MacDonald, O. A.* (Ice Making and Refrigerating Machinery, Am- monia compression system), Chicago, 111., and Sydney, N. S. W., Australia. Nason Manufacturing Co. (Ammonia and Steam Fittings), New York City, N. Y. Newburgh Ice Machine and Engine Co. (Ice Making and Refriger- ating Machinery, Ammonia compression system), Newburgh, N. Y. Pennsylvania Iron Works Co. (Ice Making and Refrigerating Machinery, Ammonia compression system), Philadelphia, Pa. Philadelphia Pipe Bending Works (Wrought Iron Coils and Bends), Philadelphia, Pa. Remington Machine Co. (Ice Making and Refrigerating Machinery, Ammonia compression system), Wilmington, Del. Ruemmeli Manufacturing Co. (Ice Making and Refrigerating Ma- chinery, Gradirworks, Ice Cans, Fittings, etc.), St. Louis, Mo. Siddely & Co. (Ice Making and Refrigerating Machinery, Ammo- nia absorption system), Liverpool, England. Sterne & Co. (Ice Making and Refrigerating Machinery, Ammonia compression system), London, England. Stevenson Co., Limited (Cold Storage Doors), Chester, Pa. Tight Joint Co. (Ammonia Fittings), New York City, N. Y. Triumph Ice Machine Co. (Ice Making and Refrigerating Machin- ery, Ammonia compression system), Cincinnati, Ohio. Vilter Manuracturing Co. (Ice Making and Refrigerating Machin- ery, Ammonia compression system and Corliss Engines), Mil- waukee, Wis. Vogt, Henry, Machine Co. (Ice Making and Refrigerating Machin- ery, Ammonia absorption system), Louisville, Ky. Vulcan Iron Works (Ice Making and Refrigerating Machinery, Ammonia compression system), San Francisco, Cal. Wheeler Condenser and Engineering Cq. (Water Cooling Towers), New York City, N. Y. Wheeler Condenser and Engineering Co. (Auxiliary Devices for Increasing Steam Engine Economy), New York City, .N. Y. Whitlock Coil Pipe Co. (Coils and Bends, Feed-water Heaters), Elmwood, Conn. Wolf Co., Fred W. (Ice Making and Refrigerating Machinery. Ammonia compression system), Chicago, 111. Wolf Co., Fred W. (Ammonia Fittings and Ice and Refrigerating Machinery Supplies), Chicago, 111. Wood, Wm. T., & Co. (Ice Tools), Arlington, Mass. York Manufacturing Co. (Ice Making and Refrigerating Machin- ery, Ammonia compression system, York, Pa. TOPICAL INDEX. Absolute boiling .point 60 Pressure 44 Zero 14, .49 Zero, change of 84 Absorber, cleaning of .. 291 High pressure in. 291 Operating the 291 The 235 Water required for 228 Absorption and compres- sion, efficacy compared. 231 Absorption, heat added and removed in ... ... .223, 224, 225 Absorption machines 86 Capacity of (example) .... 359 Construction of 232, 239 Heat and steam required (example) 359 Miscellaneous attach- ments 237. 238 Tabulated dimensions 239 Absorption of gas 50 Absorption plant, ammonia required for . 284 Charging with rich liquor 285 Installation of 283 Charging of 283 Leaks in 28B Management of . 283, 295 Overcharging of 284 Overhauling of 238 Permanent gases in 286 Recharging of 285 Testof 305 Absorption system, actual and theoreticalcapacity of ..... 230 Ammonia, required in.227, 228 Boil over, remedy for 290 Correcting ammonia in . , 290 Cycle of 222 Heat of poor liquor 226 Heat removed in absorber 225 Heat removed in con- denser 225 Liquid pumpin 224 Negative head of vapor 227 Operation of cycle 222 Poor liquor 224 Rich liquor to be circu- lated 224 ^phoning over.. ...... 2 . 2 2 2 89 9 Working of same .... 223 Absorption vs. compression 231, 238 Acetylene for refrigeration 254 Adhesion g Adiabatic changes 48. 63 Affinity, chemical 8 35 Air machines 85'. 255, 261 Air, circulation in meat rooms 215 Air, compressed, use of ...! 260 Friction in pipes (table) . . 260 Air.etc.. liquefied by Linde's method . ......". .26b, 27. 268 Air refrigerating machines 85 Air required in combustion 36 Saturated with moisture. 110 Air thermometer 76 Air, velocity of 187 Alcoholometers, compar- ison of (table) 323 Ale breweries, refrigera- tion for 206, 207 Ammonia, anhydrous 1 Boiling point of 103, 104 Density of 92 Forms of, properties of . . 91 Heat by absorption (ex- ample) 358 In case of fire.... 276 Latent and external heat of ..'. 93 Pressure and tempera- ture,. 92, 94 Properties of 91 Properties of saturated .. 93,94,329, 331 Refrigerating effect per cubic foot (table) .. '. 124 Refrigeration per cubic foot (tables) 124, 125 Required for compression plant 275 Solubility of, in water.... 100,101, 102 Specific heat of 92 Specific volume of liquid. 93, 94 Table of properties of sat- urated 329, 331 Temperature in expan- sion coil 115 Tests for 103, 104 To be circulated in twen- ty-four hours (table) ... 124 Van der Waals' formula for 95, 96 Vapor, superheated (table) 96, 311 Waste of, in compression. 275 Weight and properties of (tabulated) 93, 94 TOPICAL INDEX. 377 Ammonia absorption, heat generated by 101, 102 Ammonia and carbonic acid system, comparison of 246,. 247 Ammonia charge, fortify- ing same (example) 353 Ammonia compression, effi- ciency of (table) 348 Ammonia compression sys- tem, cycle of..... 114 General features of 114 Ammonia compressor, horse power for 133 Ammonia liquor, kinds of . . 287 Properties of (table) 97, 98, 99 Strength of (tables)97, 100, 101 Ammonia machines 88 Ammonia or liquor pump.. 237 Ammonia pump, packing of '292 Analyzer, the 233 Anhydrous ammonia for recharging absorption plant 285 Apples, cold storage of 191 Approximations, useful numbers for. '338 Aqua ammonia, kinds of .. . 287 Areaof circles 314 Argon, physical properties of 272 AtomtCity 33, 34 Atoms., 5, 8 Chemical 33 Attemperators 206 Size of 206 Sweet water for 207 Avogadro's law 53 Breweries, direct refriger- ation for 209 Refrigeration for . 203 Brewery, piping of rooms in 204, 205 Plants, actual i n s t a J 1 a- tions... 211 Refrigeration, objects of, estimate of ,, .... 197 Site...... 210 Storage rooms, refriger- ation of. 201, 203 Brewing and ice making . . . 210 Brewery equipment of fifty barrels... .. 211 Brine agitator , . . 148 Brine, circulation in tank... 161 Circulation, pipe for. . 137 From chloride of calcium 142 Preparing of 140 Simple device for making 141 Strength of (table).... 140, 141 Brine circulation vs. direct expansion 142, 143 Brine coils, cleaning of 24 Brine pump :.. 140 Brine system 137 Brine tank, arrangement of 146, 147 Leaks in 293 Operation of 293 Brine tanks and coils, &i~. mensions of (table ) 137 Brine tanks,etc..t>ainting of 282 Brine tanks, piping of 137 British thermal unit.... 14 Butter, etc., temperature, etc., for storing of ...... 193 Freezing rates for 336 By-pass 126 Back pressure 277, Barometers, comparison of (table) Battery generator or retort Bautn scales Baume scale and specific gravity (table).. ..: Beds and refrigeration Beef, specific heat of ( table ) Beer chilling devices Belting, horse power of Blood charcoal filter Body , Boilers, description of (table) Heating area of steam ... Priming of 108, Horse power of heating surface Boiling point, difference in, elevation of Of liquids Boil over in absorption, remedy for Boneblack filter : Bon estink, taint Taint, stink, testing for .. Books on refrigeration, etc. Boyle's iaw 278 45 232 100 344 219 182 208 324 164 6 337 108 109 51 350 290 164 215 216 373 44 Cabbage, specific heat of (table) 182 Calculation of indicator diagram ;,. : . . . 297 Calculation of pump (ex- ample) 368 Calculation of refrigerator for cold storage rooms. 180, 181, 182, 183 Caloric, French 15 Can, system for ice making, sizes of 144 Capacity, maximum and actual, commercial 301 Nominal compressor, ac- tual (table) ... 302 Capacity of absorption ma- chine (example) 359 Capacity of absorption sys- tem ...v . 230 Capacity of tanks in barrels (table).....' 325 Capacity, Commercial, of - compressor 302 Refrigerating, of com- pressor (examples).. 356, 357 Refrigerating, unit of 90 Theoretical, correct basis for... ..303 378 TOPICAL INDEX. Capillary attraction 60 Carbon dioxide, physical properties of 272 Carbonic acid and ammonia system, comparison 246,247, 371 Carbonic acid machine. 240, 247 Application of, efficiency of 244 General considerations.. . 240 Joints, strength and safe- ty .-. 244 Theory and practice 245 Carbonic acid plant, con- struction of .. ... 242 Evaporator, safety valve. 243 Carbonic acid, properties of (table) 240, 241 Volume of (example).. .. 366 Carbonic oxide, physical properties of 272 Carnot's ideal cycle 69 Catalogues of refrigerating machinery, etc 874 Ceilings, dripping 294 Cell ice system 167 Changes, adiabatic, isother- mal 63 Isentropic -. 77 Isothermal, adiabatic 48 Charge of ammonia in ab- sorption (example) 858 Charging of absorption plant ;... 283 Charging of compression plant 273 Cheese, temperature, etc., for storing. 194 Chemical affinity 8 Chemical combination.heat of.. 33 Chemical heat equation 35 Chemical symbols 33 Chemical works, refrigera- tion in. 220 Chicken, specific heat of (table) .. 188 Chilling meat 215 Chilling of wort, devices for 208 Chimney and grate "39 Chloride of calcium, prop- erties of solutions (table) 142 Solutions of (table) 345 Chloroform manufacture, refrigeration in 230 Chocolate and cocoa works, refrigeration in 220 Chocolate making 220 Circles, area of (table)..... 314 Circle, properties and men- . suratives of. 310 Circulating medium, choice of .comparison of (table) 89 Refrigerating effect of... 115 Combustion, spontaneous 1 .. 38 Circulation, forced 187 Cleaning brine coils 294 Cleaning of absorber 291 Cleaning of condenser.coils, etc , 281 Clearance, excessive ....... 299 Marks ..... .. ................ 280 Of compressor ......... 117, 118 Clear ice, devices for mak- ing ....................... .. 167 From boiled water ...... .. 157 From distilled water ..... 158 Coal ....... . .................. 38 Evaporation power of (example) ................ 354 Evaporative power of.. 38, 108 Steam making power of.. 108 Cohesion (.table) ........... 7 Coils, cleaning of ........... . .281 In absorption machine, corrosion of, economiz- ing of ............... ..... 287 In retort or generator ____ 233 Removing ice from ....... 295 Size of expansion . 133, 134, 136 Coils in brine tank (table). 137 Top and bottom fed ....... 294 Coke .................. i ....... 38 Cold storage, calculation of refrigeration for ....... ........ 180,181, 182, 183 Doors ................... 179, 180 Etc., usages in ............ 337 Examples; estimates ...... 360 Houses, refrigeration re- quired for. ; .......... 174, 179 Moisture in.... ; ....... 184,185 Moisture in (example).... 370 Of apples, of vegetables, of liquors ................ 191 Of butter ..... - .............. 193 Of cheese ................... 194 Of eggs .............. ....... 194 Of fermented liquors ..... 191 Of fish .............. ..... .. 192 Of grapes ................. 190 Of lemons ......... .. 190 Of milk.. ................... 194 Of miscellaneous goods ... 196 Of onions . ...... . .......... 189 Of oysters ................ 192 Of pears ____ , ............... 190 Of vegetables ......... 191 Piping for .......... 176, 177, 361 Temperatures ........ 188, 196 Ventilation in ............. 186 Cold storage rates (by month) ............... 333, 334 Terms and payment of . .. 337 Cold storage rooms, con- struction in brick and tiles, etc. ............ 167, 170 Construction of ......... 168-173 Description of. ...... ...... 188 Doors for .................. 179 Fireproof wall and ceil- Combustion ............ 95 Air required for ......... \ 86 Gaseous product of ...... 37 Commercial capacity of compressor .............. 302 Comparison of compressor data (table) ..... . ....... 304 TOPICAL INDEX. 379 Comparison of refrigerat- ing fluids 248 Compensated transfer 72 Compound compressor 125 Compressed air cycle, equa- tion of, efficiency of, 258, 259 Friction of, in pipes (table) 260 Compressed air machine, - actual performance of . 259 'Calculation of refrigera- tion 256, 257 Compression and cooling. 256 Cycle of operation 255 Limited usefulness 261 Refrigeration work. , . 258 Theoretical efficiency 260 Compressed air, uses of 260 Compression, heat of 46 Compression machine 87 Compression of gases 46 Compression plant, am- monia required for 275 Charging of 273 Efficiency of (table) 278 Installation of 273 Operation of, mending leaks 274 Permanent gases in 279 Proving of 273 Compression system, per- fect 88 Compression vs. absorption . . .231,238 Compression, waste of am- monia in 276 Compressor 114 Ammonia in 11 Capacity of 117 Capacity, nominal (table) 302 Clearance in 117 Commercial capacity of.. 302 Efficiency of 122 For carbonic acid plant. . 242 Friction of 302 Heat in, superheailngin.. 116 Horse power of 119 Horse power required for 183, Lost work, actual work, determination of 121 Lubrication of 282 Maximum theoretical ca- pacity of 30H Mean pressure in (table). 298 Piston area 120 Piston, packing of 281 Power to operate same... 133 Refrigerating capacity of '. . . 118. 119 Refrigerating capacity of (example) . .... 366, 357 Size of 119 Useful and lost work of ..... 120,121 Volumeof. 117 Work by a (example) .... 367 Work of 116 Compressor data, compari- son of (table) 304 Compressor engine, horse power of 121 Compressor test, table snowing items of. 306 Condensation in steam pipe 21, 24,25,26, 29 Condensation of steam 29 Condenser, cleaning of; 281 Dimensions of (tables)... 131 For carbonic acid plant. . 243 Heat, removed in 116, 3U3 Hendrick's 132 In absorption, water re- quired by 228 Open air 129 Pipe required for. 127, 129, 131 Pressure 277, 278 Pressure on, water for... 130 Submerged 126 Surface, amount of 127 The, in absorption 234 Water, economizing of 228, 229 Water, recooling of 129 Water, rinsing of 129 Conductors of heat 20 Constituents of water, com- position of (table) 351 Continuous conversion 64 Contracts for refrigerating plants 807 Convection of heat 23, 24 Conversion, continuous, maximum 64 Of heat 2 Convertibility of energy ... 83 Of heat, rate of 67 Coolers for wort, how to manipulate ..... 209 Special device 208 Cooler, the, in absorption.. 237 Cooling of wort, machine for, efficiency in 199 Refrigerating required . for 198 Cooling water for con- denser, amount of econ- omizing 128 Cooling .water in pipes (tables) 26,27, 30 Cooling wort (example) 357 Core in ice 162 Corliss engines, dimen- sions of (table) 340 Corrosion and economizing of coils in absorption ... 287 Cost of making ice. .149, 154, 155 Of refrigeration 167, 295 Cream, specific heat of (table) 182 Critical condition 56 Critical data 67 Critical data (table) '... 47 Critical pressure 46, 47 Critical temperature. .. .46, 47 Critical volume 46,47, 60 Cryogene for refrigeration 264 Cuoe roots, squares, cubes. etc. (table) 312. 313 Cycle, ideal, efficiency of 66. 67, 68, 69 Of absorption machine, equation of same 222 Of operations, reversible. 65 Cylinders, contents of. in gallons and cubic feet (table) 322 380 TOPICAL INDEX. Dairy, refrigeration in 218 Dalton's law 46, 52 Data of test, table showing. 304 Decorative effects, by re- frigeration 219 Defects of ice 162 Defrosting of meat 216 Density 6 Density ofammonia 92, 94 Development of heat ... 35 Dew point... 110 Different saccharometers 200, 201 Dimensions, of absorption machine (tabulated) 239 Of absorption machines (table) 239 Of condensers (table) .... 131 Of Corliss engines 340 Of energy, units of 79 Of extra strong pipe 352 Of distilling plants 160 Of ice making tanks(table) 145, Of pipe, standard 136 Direct expansion vs. brine circulation 142, 143 Direct refrigeration for breweries 209 Disinfecting cold storage rooms 188 Dissipation of energy 63, 81 Dissociation , 52 Distilled water, filtering, . rebelling, cooling 159 Production, condensation 158 Distilleries, refrigeration in ,. 220 Distilling plant, arrange- ment Of, operation of. . . 161 Dimensions of f ....... 160 Doors for cold storage room 179 Doors for storage rooms ... 179 Double extra- strong pipe, dimensions of (tanle)'... 338 Dripping ceilings.. 2>4 Dry air for refrigeration.. 185 Dryer for ammonia 143 Drying, air 112 Of egg room, etc. 195 Dry vapors 50 Duplex oil trap 133 Dwellings, refrigeration of 219 Dynamics 9, 43 Dynamite works, refriger- ation in 218 Dyne -..,...7. 346, 347 Dyne centimeter 10 Ebullition 51 Economizing of water 293 Efficiency, of absorption and compression.; 231 Of absorption system 231 Of ammonia compression (table) 348 Of boiler and engine 305 Of compressed air ma- chines ... 260 Efficiency of compression plant (table) 278 Of ideal cycle .... 66. 67, 68, 69 Of sulphuric dioxide ma- chine 250 Relative, of fuels 350 Eggs, freezing rates of 337 Temperature, etc., for storing, moisture, etc., 194, 195 Elementary bodies 33 Elementary properties (ta- ble) 34 Elements, properties of . (table) 34 Energetics, system of, mod- ern -... 78 Energy, C. G. S., units of ... 10 Chemical, of distance, of surface of volume 78 Comparison of units of (table) .- 346, 347 Conservation of, transr formation of, kinetic ... 10 Continuous conversion of 83 Dissipation of, radiant 81 Dimensions of, units of. . . 79 Dissipation of 10, 63, 81 Factors, capacity of, in- tensity of..'. 79 Free and latent, charges of i 72, 73 New departure of, me- chanical, electric 78 Of a moving body 10 Of gas mixtures 63 Of motion, kinetic 78 Reversible an d irrevers- ible , 82 Transformation of 82 Uniform units of 83 Visible, kinetic, potential, mqlecular 9 Engine and boiler.efficiency of 305 Engineering and refrigera- tion... 221 Engines, dimensions of standard Corliss (table) 340 Pounding 281 Water required for 123 Entropy.... '72 And intensity principle .. 83 And latent heat 77 Increase of 74 Equalization of .pipes 138 Equation of compressed, air cycle 258, 259 Equilibrium of energy,arti- ficial 81 Equivalent units 61 Equivalents in piping 136 Erg 10, 346, 347 Estimates and proposals for refrigerating plants 306 Ether machine, efficiency of 251 Properties of 251 Properties of hypotheti- cal ; 11, 12 Ethyl chloride machine 249 Ethylene, physical proper- ties of 272 Evaporating water 28, 30 TOPICAL INDEX. 381 Evaporation power of coal (example) ........... '...-.. 354 Evaporator for carbonic acid plant ................ 243 Examples on natural gas... 361 Exchanger, leak in .......... 288 The, in absorption ..... .. . 236 Expansion, by heat ........ 17 Co-efflcient of (table) ..... 17 Free, latent heat of ....... 48 Of ammonia ............... 134. Of liquids ........ _____ ...... 17 Of liquids and solids by heat ...................... 17 Top and bottom feed ...... 294 Expansion coils, size of ..... 184 Expansion valve .......... 133 Experiments on wort cool- ing (table) ................ 352 Explosive bodies ............ 36 External work of vaporiza- tion ................ . ....... 62 Extra strong pipe, dimen- sions of (table) . 352 Freezing Rates, terms and payment of 337 Rooms in packing houses, calculation of refriger- J ation 213 Tank, arrangement and construction of 147 Tank, dimensions of (ta- ble) 145 Tank, pipe in 146 Tank, size of :. . . 148 Time for (table) .146, 149 Friction, of gases 49 Of water in pipes (table) - .. .......327, 346 Frigorific mixtures Stable ) . 32 Fruits, temperature for storing 188, 189, 190 ,Fuel; economizing of 161 Fuels, heat of, combustion - of ( table ) 38 Relative efficiency of..... 350 Fusion, latent heat of (table) 31, 332 .factors of energy, of in- tensity and of capacity. 79 Fall of heat 71 Fermentation, heat by 200 Heat of 200, 205 Heat produced by, calcu- lation, rule for ... . 200- Removing heat of 207 Filter, boneblack, blood charcoal 164 For distilled water, inter- mediate 160 Filters, number required, when required.when not 165 Filtration, dangers of 163 Fire and ammonia 276 Fish and oysters, tempera- ture for storing 192 Fish, freezing rates for 336 Specific heat of (table).... 182 Flow, of liquid, quantity of 42 Of steam 109 Of water in pipes. 43 Fluids 40 Viscosity of.... 40 Foot-pound 8, 346, 347 Force, measurement of *s... 7 .Molecular 7 / Unitof 7 Forced circulation 187 Forecooler 131 Free, energy, changes of .72, 73 > Expansion 48 Freezing back 279 Goods 183 Time 146, 149 Freezing mixture, capaci- ty of (example) 354 Mixtures 86 Of meat 21* Rate for butter 336 Rates for eggs $.33? Rates, in summer, for flsh, * for meats ... .... 336 Gallons contained in cylin- ders (table) Gas and vapor Gaseous products of com- bustion . .. Gas equation, Van der Waals' .;..* ...55, 58, Gas mixtures, energy of Gases, absorption of...- Adiabatic changes 48, And liquids, general equa- tion 55, 58, Buoyancy of Components of, specific heat of .' Constitution of Critical data (table ) Critical pressure Critical temperature..... Critical volume 46, Density of Equation of 55, Expanding in.to vacuum . . Expansion of Free expansion Friction of , in pipes Internal friction of Isothermal changes 48, latent heat of expansion. Liquef action of 46. Mixtures of Perfect Pressure and tempera- ture of 44, Properties of (table) Relation of volume, pres- i sure and temperature of 48", Solubility of. in water . (table) ' Specific heat of, at con- I stant volume and pres- J sure Specific heat of (table) .... Velocity of sound in .. Weight of 37 59 63 50 63 59 46 75 44 47 46 46 47 53 56 62 55. 48 49 54 63 48 60 46 49 53 272 49 382 TOPICAL INDEX. Gauges 45 Gauge pressure . . .44, 45 Gay-Lussac's law 55 Generation of neat 35 Generator, battery 232 Heat required for 327 Still or retort, size of (table) 232 Glue works, refrigeration in 218 Glycerine trap in carbonic acid plant 242 Grains and milligrams per gallon (table)...... 351 Grapes, cold storage of 190 Graphite for lubrication... 282 Gravitation ., 7 Hampson's device for lique- fying air tl] Harvesting ice 148, Head of water In pressure per square inch (table).. .. Heat, absorption of (table) Available effect of Capacity ... By absorption of ammonia (example) By chemical combination By different fuels (table). By mechanical means .... C. G. S. unit of, capacity of ; .... Changes, components of.. Complicated transfers . . . Cond uctivity ( table ) Convection of 23, Conversion of 82, 64, Determination of specific Emission of (table) 22, Emitted by pipes Energy, origin of Energy, transfer of Engines Fall of Generated by absorption of ammonia 101, Generated by ammonia absorption 101, Generation of 35, Latent 30, Latent of fusion and vola- tilization (table) 31, Leakage of walls for cold storage 170, Of chemical combinations Of combination (table) 36, 37, Of compression Of fermentation Produced by fermenta- tion, calculation, rule for Heat leakage, of buildings.. Heat, radiation and reflec- tion of (table) Radiation of 11,12, Sources of Specific, of liquids(tables) 149 43 33 38 39 15 65 23 20 24 S* 30 25 74 62 70 71 171 46 205 170 22 Heat, specific, of metals and other substances 16 Specific, of victuals;.. 182, 183 Specific, of water 16 Transfer of ,. . . 18, 23, 24 Transfer from air to wa- ter 30 Transfer, theory of 22 Transmission of, through plates 27,38,29, 30 Unitof 14 Use of specific 16 Weightof 77 Heater, the, in absorption. 236 Heating surface of boilers. 328 -Helium, physical proper- ties of ..: 272 Hop storage by artificial refrigeration 211 Hop storage, temperature for 210 ^ops, storage of 210 Horse power 8, 43, 346, 347 Of belting, of shafting (ta- ble)..... 324 Of boilers 328 For ammonia compres- sors 133 Grate surface , required for 108 Of steam engine (example) 367 Steam required for 108 Of waterfall (example).. . 368 Hospitals, refrigeration of. 219 Houses for storing ice 150 Humidity in air, relative, absolute 110, 111, 112 Table 1 332 In atmosphere(tables).lll, 112 Hydrodynamics 43 Hydrogen, physical proper- ties of 272 Hydrometers, comparison of (table) 40, 41 Hydrostatics 43 Hygrometers 112 Hygrometry 110 Ice, after plate system.. 148, 149 By cell system 167 Cans, sizes of 144 Cost of making 154 Cost of making (tables)154, 155 Devices for making clear 167 Factories, cost of operat- ing (table) 154, 155 Formation of properties of "...I 106 Handling of. ;. 153 Heat conducting power of ..._.... 152 Harvesting ot 148, 149 Houses, refrigeration of 150, 351 Machines, construction of 86 Machines, measurement of size and capacity 90 Making, amount of water required for same 128 Making and brewing 210 Making, can system 144 TOPICAL INDEX. 383 Ice making capacity 90 Making capacity, exam- ples on 866 Making^ cost of same, U9, 154, 155 Making, properties of wa- ter for 157, 166 Making, plate system. 148, 149 Making, systems of, capa- city of plant 144 Making tanks, dimensions of (table). , 145 Odor of 14 Packing of ,....,;... 151 Quality of 156, 157 Removing from coils . 295 Rotten 165, 166 Selling of 152 Shrinkage of 152 Specific Seat of 107 Storage houses . 150 Storage houses, refriger- ation of 150, 151 Storage of manufactured 149 Taste and flavor of. .. 164 Test for 166 Weight and volume of 153 Withdrawal and shipping of ..., 152 With core 162, 163 With red core 163 -With white core ; 162 India rubber works, ref rig- V eration in , ( 220 Indicator diagram, inter- pretation of 299-302 Indicator diagram 296, 297 Inertia ...;... 9 Inflammable bodies 36 Installations, actual, of brewery plant 211 Of absorption plant 283 Of compression plant... . 273 Insulation 282 Of steam pipes (table).... 20 Insulators (table ) 19 Intensity, and entropy prin- ciple 83 Principle, compensation of Internal work of vaporiza- tion.. 52 Isentropic changes 77 Isothermal changes.. ....48, 63 Isothermal compression, work required for ... 259 Joule 846, 347 Kilogrammeter 8 Kinds of aqua ammonia or ammonia liquors 287 Kinetic energy 9 Kinetics, molecular 53 Latent energy, changes of . 72, 73 Latent heat, of fusion (ta- ble;., . 31 Latent heat "of solution.. 31, 32 Of vaporization .. 51 Leakage of heat in build- . ings ....:. 1TO Leak in plant discovered by soapsuds 273 Lifting of heat (example).. 355 Lignite.. ....r 39 Linde liquid (oxygen), its uses : 271 Llnde's method, for lique- - f action of air,etc.266, 267, 268 Rationale of.... 267, 268 Liquefaction of gases. ..266, 272 History of 266 Liquefaction of vapors 52 Liquefied air by Linde's method. .....266,267, 268 Liquefying air, by Hamp- son's method 268 By other methods 269 Liquid air, for motive pow- er, for refrigeration. .. 270 Motive power of (example) 369 Uses for same 270, 271 Liquid receiver , . ISO In absorption 235 Liquids, buoyancy of 40 Boiling point of 350 Expansion of 17, 18 Flow of .-. ,... 42 Pressure of 41 Specific heat of 15 Surface tension of 43 Useful data about. ... 341, 342 Velocity of 42 Viscosity of ....>;.... 40 Liquid traps 143 Liquor or ammonia pump.. 237 Liquor pump, in absorption 224 Workdoneby 227,228 Liquors, temperature for storing (table) 191. Leaking valve and piston packing.. 300 Leak in rectifying pans 289 Leaks, in absorption plant, . in exchanger 288 In brine tank 293 Lemons, cold storage of 190 Localities, temperature in different (table) 341 Logarithms, rules for using them 317 Table of, use of. . ..315, 316, 317 Lowest cold storage tem- peratures 196 Lubricating of compressor 282 M Malt houses, refrigeration of 211 Management, of absorber. ..391 Of absorption plant. .. .283-295 Of compression plant ..273-282 Of refrigerating plants... 295 Manometers . t 45 Marsh gas, physical proper- tiesof 272 Mass. 6 Unitof 6 Materials, specific weight of (tables) 319,320, 321 384 TOPICAL INDEX. Matter, constitution of.. .. 5 General properties of : .. 5 Solid, liquid, gaseous.. .. 5 Maximum conversion. 64 Maximum convertibility .. 83 Maximum principle 85 Mean effective steam pres- - sure (tables) ..348, 849 Pressure of compressor (table) ...; 298 Measures and weights (ta- bles) 317,318, 319 Meat, cause of bonestink of 216 Chilling ...... 215 Effect of freezing on.. 2H, 217 Freezing from within," de- frosting of .' 216 Freezing of, storage tem- peratures (table) 214 Mold on, keeping of, ship- ping of -.; -...>. 217 Rooms, circulation of air in l ..;,.-. .-.215, 217 Thawing and defrosting of ,.. 216 Time of keeping of. 217 Withdrawing irom\stor- - < age.......... Yx'.V... 214 Meats, freezing rates for . . 336 Meat Storage, official views on....:..... v 214 Mechanisms .11 Megerg 10- Melting points (table) ....-.; 31. Mensuration, of circle, solids, polyhedrons, etc. 310 Of surfaces (table ) 309 Mercury wells . . . 296 .Metals, conductivity of .^ ... 22 Specific heat of 15 . Specific weight o^. . . . .819-321 Methylic chloride machine. 249 Metric and U. S. weights and measures (table).:.. 323 Measurement, compari- son 319 Milk, specific beat of (table) 182 Temperature, e t c . , f o r storing ; . , 194 Milky ice 162 Milligrams and grains per gallon, etc. (table)..,... 351 Minerals, metals, stones, specific weight of (table) ....319-321 Miscellaneous* goods, tem- peratures, etc., for stor- . age ....!.:. 196 Miscellaneous refr i g e r a - tion 218-221 Mixed vapors .... 52 Mixtures, frigorific (table). 32 Temperature of .'.<... 16 Modern concepts. .'... ...... 83 Modern energetics 78 Moisture, in air, absolute . determination of 110 In air (table) 332 In atmosphere (tables) 111 112 In cold storage ..-. 184" In cold storage (example) 370. Relative, in cold storage. 370 Rules for, cold storaare.... 187 Mold on meat 217 Molecular dynamics 53-u Forces 7 Kinetic...:.. 53 Transfer of energy^...,. . 62 Velocity^ *..:. .... 54 Molecule : 33 Molecules , 58 Heat energy of.. > i 64 Momentum- 8 Motion....... ....' 7 Laws of.......: 9 Perpetual.. 82 Motay and Rossi's system of refrigeration . . . , 254 Motive power of liquid air (example) 369 Natural gas, expansion, re- frigeration, work, etc. Negative specific heat 76 Nitric oxide, physical prop- erties of.. ;.. 212 Nitrogen, physical proper- ties of .... 272 Noise in engine or pump, how located..., .. ..281 'Odor of ice 164 Oil trap.. , 126 Duplex ;...; 133 Oil works, refrigeration in. 218 Onions, cold storage of 189 Operation of compression plant .\ 274 Optics 10 Overhauling absorption plant 238 Oxygen, physical properties of ,.....: 278 Oysters, specific heat of (table) :.. 182 Oysters and fish, tempera- ture for storage J92 Packing houses, etc., re- frigeration for, rule for- . calculation . , 212, 2f3 Freezing rooms, piping of same .-.:.:. ..212, 213 Packing of ammonia pump, 292 Packing of compressor piston : 281 Packing of ice 151 Painting brine tanks, etc.. 282 Pascal's law : 40. Passage of heat 64 Pears, cold storage of . ... 190 Peltry, refrigeration of.... 218 Perfect gases 47 > Equation of 55 Performance of ammonia and carbonic acid sys- , tern 246,247 Performance of compressed air machines . . 259 TOPICAL INDEX. 385 Permanent gases, examples on .....354,856 In absorption plant 288 In compression plant 279 Origin of . 280 Perpetual motion 82 Pf erdekraf t 346, 347 Photography, artificial re- frigeration in 218 Physics, subdivisions of 10 Pictet's liquid, refrigera- tion by 258 Pictefs liquids, anomalous behavior of 252, 253 Pipe, dimensions of, double extra strong (table). ... 339 .Extra strong, dimensions of 352 For condenser '.. 130 Rules for laying 138 Dimensions of (table )?... 136 Flow of steam in (table). 328 Friction of water in (table) 327,346 Table for equalizing. ..... 138 Transmission of heat 135 Pipe required in c o n- denser .....127, 129,131 Pipes, dimensions of stand- ard 136 Piping, equivalents in 136 Piping of brine tanks 137 Piping cold storage rooms.. 172 For cold storage (exam- ples) 361 Of brewery rooms, rules - ." 204, 205 Required for storage rooms ( tables) 174-178 Rooms 134 Rooms in packing houses, etc 213 Rooms, practical rules for 135 Pipe line refrigeration 221 Plants, specification of. 306, 307 Plate and can system, com- parison of 148,149 Plate ice, size of 149 Plate system for ice mak- ing 148,149 Polygons, surface of (table) 309 Polyhedrons, mensuration of (table) 310 Poor and rich liquor (table pt strength) 226 Liquor, heat introduced by 226 Liquor in absorption, strength of 224. 225 Pork,specificheat of (table) 182 Poultry, freezing rates for. 335 And game, rate of freez- ing of . 334,335 Rates for storing un- frozen 336 Pound, Fahrenheit 346,347 Pounding pumps and en- gines 881 Power required for am- monia compressor ..... 133 Furnished by liquid air (example) 366 Power' required to raise water (table).... 326 Unit of 8 Practical examples 353-370 Practical tests of ammonia and carbonic acid sys- tem 247 Pressure and temperature of gas. 19 Pressure, condenser and back , 277,278 Critical 46, 47 Gauge, absolute 44 Mean effective, of steam (tables) 348,849 Mean, in compressor (table)., 298 Of liquids 41 Unitof... 44 Principles of energy, regu- lative, intensity 80 Properties of ammonia 91 Of ammonia liquor.. 97, 98, 99 Of gases ( table) 272 Of saturated ammonia (table) 329,331 Of sulphuric dioxide 249 Proposals and estimates for refrigerating plants 306 Psychrometers... 111 , Pumping of vacuum 273 Pump, calculation df (ex- ample.) : .368 .Pumps,discharge by (table) 139 Pounding 281 Purge valve;,.. 132 Radiation of heat... 11, 12, 22, 23 Rates for freezing, in sum-' mer, for fish and meats, 336 Poultry, butter, etc.. ..334-337 Rates of cold storage (by months 333, 334 Rationale of Linde's method 267, 268 Recharging absorption plant 285 Rectifier, the, in absorption, . I size of (table). , 234 Rectifying pans, leak in .... 289 Red core in ice. - 162, 163 Refrigerating capacity, .nominal, actual, com- mercial 302 Refrigerating capacity, of compressor -(examples) ...... . ,356,357 Units of, British, Ameri- can , 308 Refrigerating duty, exam- ples on 364.365 Refrigerating effect 52 Net theoretical 117 Per cubic feet ammonia (table) 124 Refrigerating fluids, com- parison of 248, Refrigerating m a. c h i n e, , . ideal, efficiency of 71 386 TOPICAL INDEX. Refrigerating machinery, etc., catalogues, price lists 373 Testing of 308 Refrigerating m a c h i n e s. . different systems,85,86,87, 88- Refrigerating plant, fitting up for, test of 296 Estimates and proposals for, contracts 306, 307 Testing of 296-308. Refrigeration, according to Motay and Rossi. 254 And engineering 221 And work, by natural gas (examples) ^.361, 362, 363 By cryogene.by acetylene 254 By dry air 185 By liquid air 270 By. Pictet's liquid 252 By sulphur dioxide 249 Calculation of, for cold storage 180, 181, 182, 183 Cost of 167,295 Different systems of 103 During transit 218 Etc., books on 372, 373 For breweries :. . 197-211 For miscellaneous pur- . poses 217-221 For packing houses, etc., rule for calculation 212 In breweries, distribution of '.. 203 In chemical works. . ..... 220 In chocolate factories. . . . 220 In dairies.... ^.. 218 In distilleries 220 In dwellings 219 In dynamite works 219 In general, means of pro- ducing 85 In glue works 218 In hospitals.... 219 In India rubber works.... 220 In malt houses 211 In oil works 218 In soap works ." 218 In storing trees 218 In sugar refineries. . . : ... 220 In sulphuric acid works, soda works 221 Means of producing 85 Of brewery storage rooms 201,202 Of photographic supplies, 218 Of silk worm eggs 218 Required for storage rooms (tables) 174, 179 Self -intensifying .265 Transmission of 135 Uses of artificial 90 Refrigeration units, differ- ences between them 308 Relative moisture or hu- midity (table) 112 Retort, heat required for.. 227 Or still in absorption, coils in 232,233 Reversible changes i. 82 Reversible cycle .-*. 65, 88 Refrigeration in 89 Rich and poor liquor (table of strength ) .- ; 226 Rich liquor, amount of, to becirculated ... 224 Example on ; 358 In absorption, strength of ..224,225 Rooms, construction of, for cold storage.. 169, 170, 171,172 In brewery, piping of .204, 205 Rotten ice 166, 1B6 Rules for laying pipe 138 Of moisture in cold stor- age :... 187 S Saccharometers. compari- son of (table) 202 Different 201 Safety valve in carbonic acid plant 243 Salometer, substitute for, . comparison of 142 Salt cake, decomposition of, by refrigeration 221 Salt solutions, properties of ... 140 Saturated ammonia, table of properties of 329-331 Saturated vapors 50 Scale in coils removed by acid;...... 291 Scales, different, of ther- mometers 12, 18 Self-intensifying refrigera- tion 265 Shipping provisions, refrig- eration in .. 219 Silk worm eggs, refrigera- tion of 218 Site for brewery 210 Skating rinks 154, 156 Skimmer. . ...:... 161 Soapsuds to discover leaks 273 Solids, mensuration of (table) 310 Solubility, of ammonia in water (table) 102 ' Of gases in water (tables \339 Solution, latent heat of. .31, 32 Solutions, of ammonia, strength and properties (table) 100,101,102 Of chloride of calcium . (table).....- 345 Sound, velocity of...; 49 Southby's vacuum machine 263 Operation of. 264 Space, measurement of 8 Spe-cific gravity and v Baume scale (table) 344 Specific gravity, deter- mination of 40 Specifications of plants. 306, 307 Specific heat, calculation of 183 Determination of. ....' 16 Example on . 354 Negative 76 Of ammonia 91 Of beef 182 Of cabbage 182 Of chicken 182 Of cream 182 TOPICAL INDEX. 387 Specific heat of fish ... 182 Of gases (table) 47 Of liquids 15 Of metals ;. 15 Of milk 182 Of oysters J82 Of pork 182 Of veal 182 Of victuals 182 Of water, of ice, of steam. 107 Of wort (table) 197 Use of 16 Specific volume of steam... 107 Specific weight 6 Of materials (tables) 319,320, 321 Spontaneous combustion... 36 Square and cubic roots (table) 312, 818 Squares, cubes, roots, etc. (table) 312, 313 Statics 9 Steam, condensation in pipes (tables)... 21, 24, 25, 26 Condensation of, in tubes. 29 Economizing of, in ab- sorption, amount re- quired 229 Steam engine, horse power of (example) 36T Steam, flow of 109 Flow of, in pipes ( table ) . . 328 Internal and external heat of 106 Latent heat of 106 Steam pipe, condensation in 21 Insulation of 20, 21 Steam, production of, work done by 108 Properties of (table) 107 Saturated 105 Specific heat of 106 Specific volume of 107 Total heat of 106 Steam, pressure of (table).. 107 Steam produced per pound of coal 108 Steam to produce horse power 108 Steam, volume of 105 St. Charles' law 44 Stiff valve and irregular pressure 800 Storage houses for ice, con- struction, ante-room of. 150 Storage of hops 210 Of manufactured ice .149, 150 Refrigeration for, piping for (tables) 174-178 Storage rooms, drying of, etc .....195 Rent of. 337 Ventilation 188 Storage rooms, doors for same 178 Strength of brine required 142 Stuffing box for carbonic acid plant.... T. 242 Sublimation 52 Sugar works, refrigeration , in 7. .\. 230 Sulphuric acid, concentra- tion of, "by refrigeration 221 Sulphuric dioxide machine, useful efficiency of 250 Sulphur dioxide, proper- ties of, refrigeration by 249 Sulphuric dioxide, prop- erties (table) -.... 250 Refrigerating effect of (example) 356 Superheated ammonia va- por (table) , 811 Superheated vapors 50 Superheating, water to counteract 125 Surface, tension of liquids. 42 Sweet water 207 For attemperators 207 Syphoning over in absorp- tion plant 889 Symbols, chemical 38 Tables (appendix I) 809-352 Tanks, capacities of, in bar- rels (tables) 325 Taste of ice 164 Temperature 12 And pressure of gases 44 Critical 46, 47 Measuring of high 13. 14 Of mixtures 16, 17 Comparison of, Fahr. and Centigrade (table) 343 Etc., for cold storage.. 188-196 Etc., for storing butter. .. 193 Etc., for storing cheese.. 194 Etc., for storing eggs 194 For hop storage 210 For storing fruit. . 188, 189, 190 For storing liquors 191 For storing milk 194 For storing miscellaneous goods (table) 196 For storing oysters, fish . . 193 For storing vegetables... 191 For storing meat 214 In different localities (table)., 341 Lowest, for cold storage. . 196 Temperatures of cellars... 805 Tension, of vapors 60 Of vapors in air (table). . . Ill Of water vapor