MECHANICS DEPT. THE ELEMENTS OF REFRIGERATION WORKS OF PROFESSOR A. M. GREENE, JR. PUBLISHED BY JOHN WILEY & SONS, Inc. Elements of Heating and Ventilation. A Text-book for Technical Students and a Refer- ence Book for Engineers, vi + 324 pages, 6 by 9, 223 figures. Cloth, $3.50 net. Pumping Machinery. A Treatise on the History, Design, Construction, and Operation of Various Forms of Pumps. Second Edition, viii + 703 pages, 6 by 9, 504 figures. Cloth, $4.50 net. The Elements of Refrigeration. A Text-book for Students, Engineers and Ware- housemen, vi + 472 pages. 6 by 9. 192 figures. Cloth, $4. 50 net. BY SPANGLER, GREENE, AND MARSHALL: Elements of Steam Engineering. By the late H. W. Spangler, A. M. Greene, and S. M. Marshall, B. S. in E. 1& Third Edition, Revised. v + 296 pages, 6 by^Bk 284 figures. Cloth, $3.00 net. THE ELEMENTS OF REFRIGERATION A Text Book for Students, Engineers and Warehousemen BY ARTHUR M. GREENE, JR. ii Professor of Mechanical Engineering and Dean of the School of Engineering, Princeton University FIRST EDITION SECOND IMPRESSION, CORRECTED NEW YORK JOHN WILEY & SONS, INC., LONDON : CHAPMAN & HALL, LIMITED . Engineering Library Copyright, IQTS, 1919 BY ARTHUR M. GRLENE, JR. PREG3 OF I/2A BRAUNWORTH & CO BOOK MANUFACTURERG BROOKLYN, N. Y, PREFACE The aim of the author in preparing this book has been to bring together in a logical order the necessary data from which to design, construct and operate refrigeration apparatus. He has endeavored to describe the apparatus and then to give the theoretical discussion of the principles on which the action of this apparatus rests. A detailed description of the applica- tions of refrigerating machinery to cold storage and ice making is followed by that of other applications. The author has freely consulted the Transactions of the American Society of Refrigerating Engineers and the bound volumes of Ice and Refrigeration, and has gained much information from these two excellent publications. Much of the text has been de- veloped in teaching this subject for many years. Whenever the work of others has been used, credit has been given. The author is indebted to many writers whose work he has used in the class room and in preparation of his lectures, and to the manufacturers of refrigerating apparatus who have given data for the preparation of this text. The aim has been to make the book complete with the necessary engineering data for problem work without reference to other books. The author has added a set of problems in the last chapter illustrating most of the computations which must be made in refrigerating work. The problems illustrate the methods by which questions of the engineer may be answered. The book is intended for the use of upper class men in technical schools, for engineers and those operating re- frigerating apparatus. The work presupposes a knowledge of thermodynamics and heat engineering. The plan of the work has been for a continuous study of the book without any omission. The last two chapters are a r: 3 n I " iv PREFACE intended to give data and methods for actual computations and should be used during the course for problem work. Prob- lems based on the text should be given with the study of the book. These problems should be solved by use of the slide rule. The author desires to thank his wife, Mary E. Lewis Greene, for the aid she has given in the preparation of the manuscript and in the reading of proof. He desires to thank those authors, publishers and manufacturers who have furnished him with data. A. M. G., Jr. SUNNYSLOPE, TROY, N. Y. September i, 1916. TABLE OF CONTENTS CHAPTER I PAGF PHYSICAL PHENOMENA AND INTRODUCTION. Early methods, evaporation, solution, latent heat, heat of fusion, vaporization under reduced pressure, natural ice, compression machines, air, volatile liquid, general principles i CHAPTER II METHODS OF REFRIGERATION. Natural ice, different systems of cold storage, refrigerator cars, air machines, open and closed systems, volatile liquid machines, refrigerants, absorption machine, vacuum apparatus, chemical methods 8 CHAPTER III THERMODYNAMICS OF REFRIGERATING APPARATUS. Air machine, refrigerating effect, cooling, displacement, work, effect clearance, effect friction, incom- plete expansion and compression, moisture, vapor machines, temperature- entropy charts, Mollier charts, dry and wet compression, absorption apparatus, problem, multiple effect 41 CHAPTER IV TYPES OF MACHINES AND APPARATUS. Various machines, cylinders, manip- ulating valves, pistons, CO 2 machines, SOj machines, absorption apparatus, welding, pipes, fittings, condensers, separators, receivers, coolers, vacuum apparatus, binary refrigeration, cooling towers, nozzles, ponds, safety devices 109 CHAPTER V HEAT TRANSFER, INSULATION AND AMOUNT OF HEAT. Radiation, convec- tion, conduction, transmission, constants, walls, partition?, floors, pipe covering, doors, heat from machines, lights, persons, cold storage data.. . 182 CHAPTER VI COLD STORAGE. Purpose, laws, peculiar features of storage for different articles, layout of warehouse, construction, arrangement of piping, vi TABLE OF CONTENTS PAGE special cold storage, amount of insulation, indirect refrigeration, bunkers, fans, amount of refrigeration, coil surface, pipe sizes, central stations, automatic refrigeration, refrigerator cars, precooling 217 CHAPTER VII ICE MAKING. Can system, plate system, apparatus, flooded system, filters, evaporators, raw water system, freezing tanks, expansion coils, curve of consumption, storage 269 CHAPTER VIII OTHER APPLICATIONS OF REFRIGERATION. Candy, breweries, blast furnace, auditoriums, rinks, ice cream, shaft sinking, drinking water, chemical works, dairy, creamery, liquid air 312 CHAPTER IX COSTS OF INSTALLATION AND OPERATING COSTS. Land, buildings, machin- ery, supplies, dimensions of apparatus, power and performance of plants, labor costs, load factors, operating costs, ice data, car data, ice cream data, ammonia, carbon dioxide, sulphur dioxide, testing apparatus, results of tests 343 CHAPTER X PROBLEMS. Insulation, space, refrigeration for rooms, coil surface, pipe length, velocity of brine, bunker coil, fan size, brine main and pump, ammonia main, plate plant, refrigeration of plant, ice storage, cost of pumping, evaporator, filter, compressor, power, condenser,^ multiple effect, water cooling tower, blast furnace refrigeration, test computations. 407 ELEMENTS OF REFRIGERATION CHAPTER I PHYSICAL PHENOMENA AND INTRODUCTION THE practice of cooling bodies below the temperature of the surrounding atmosphere has been followed for ages. This has been done by the evaporation of a liquid as is the practice in Mexico and other warm climates, where the liquid to be cooled is hung in porous vessels. The evaporation of the liquid which percolates through to the outside cools that remaining inside. In India, it is stated, evaporation from the surface of shallow porous vessels even causes a film of ice to form. The solution in water of a salt like saltpetre, or the mixture of snow or ice and saltpetre, has been used for centuries to abstract heat and cool the liquid resulting, or anything that was immersed in it. The first method was applied about one hundred and fifty years ago in a way differing from that of the ancients. It was then found that evaporation of the liquid would occur if the pressure were removed, particularly if the liquid were ether or some other highly volatile liquid. This evaporation would occur at such a low temperature that ice would rapidly form on the surface of the vessel containing the boiling liquid if the vessel were placed in water. It was also found that if the vapor arising from the evaporation of the liquid were compressed to a higher pressure than that at which evapora- tion took place, it could be condensed again by water at ordinary temperature, and the process repeated. The property of the substances utilized in these illustrations 2 ELEMENTS OF REFRIGERATION is the property of latent heat. When a body changes its state, a certain amount of energy must be absorbed by that body to bring about this changed state. To change a body from a solid in which the form and volume are fixed and the con- dition of the molecules is such that their orbits are fixed, into a liquid in which the volume but not the form is fixed, or the molecules have orbits which have more freedom, requires the addition of energy. The name heat energy, or heat, is applied to this. Energy is required to change a body from the liquid state to the vapor state in which the form and volume are not fixed, since the molecules have free paths. The molecules are so far apart that molecular attraction has been broken down. The energy required in the case of the fusion of a solid or the evaporation of a liquid is used to overcome molecular energy of attraction, and for that reason it is potential in form within the body. It is not used up in increasing the kinetic energy of the particles of the body, and hence there is no change of temperature during these additions, and the heat is called latent heat. In general, if heat be continuously added to a solid while the pressure remains constant, its temperature will rise until the point of melting or fusion is reached and then the tem- perature will remain constant until the solid is changed to a liquid. The temperature of the liquid will then continue to rise with the addition of heat until the boiling-point is reached, at which point the temperature will remain constant while the heat is added, although the liquid will be changing to a vapor. The further addition of heat will increase the temper- ature of the vapor. The previous operations were supposed to take place at constant pressure, because to every pressure there corresponds a temperature of fusion and a temperature of vaporization. These are fixed for definite pressures, and at these pressures and temperatures the amount of heat to fuse i Ib. of sub- stance, the heat of fusion, and the heat required to vaporize i Ib. of liquid, the heat of vaporization, are fixed. Should the pressure change, the temperature of these actions would'change. PHYSICAL PHENOMENA AND INTRODUCTION 3 In the ancient way of producing cool liquids, the evap- oration which occurred at the outside of the vessel required heat, and this was largely supplied from the liquid within. The liquid was cooled by the removal of heat. If this removal of heat cools the liquid to its freezing-point (fusion-point of solid), any further evaporation of the liquid from the surface of the vessel would remove heat from the liquid and cause some of it to solidify, forming ice if the liquid were water. In the case of salt being dissolved, this same kind of energy is needed. In this case it is called the heat of solution. To change the condition of the molecules of the salt so that the molecular forces are overcome, energy is applied, and as this energy comes from the liquid, its temperature is lowered. In the case of the vaporization of a liquid under reduced pressure, the object of this reduction is to permit the evap- oration at such a low temperature that heat may be removed from surrounding objects of low temperatures. Water boils at 212 F., but if the pressure were reduced to ^V lb. the tem- perature of boiling would be less than 32 F. and with the evaporation of some liquid, ice could form. Of course, it must be remembered that the evaporation of a liquid can take place only if heat is added to it at the boiling-point. If the liquid is at the boiling-point and there is nothing from which heat can be abstracted, nothing can happen. If it is in contact with substances at temperatures below the boiling-point noth- ing will happen. For this reason the pressure on the lower side must be such that the boiling temperature is below the temperature of the body from which it is to abstract heat, and when evaporated, the pressure must be raised to a point at which the boiling temperature will be above that of the substances used to abstract heat. In this latter condition the substances will abstract heat from the vapor and condense it. These methods have been used for years to obtain cool water, to preserve foods and for other purposes. In many places, however, this preservation was carried on by the use of natural ice harvested in the winter and stored until needed in warm weather. 4 ELEMENTS OF REFRIGERATION It was about the middle of the last century that the Carre Brothers produced commercial machines for the freezing of water. Both machines operated to remove heat by vapor- ization of a volatile fluid, Edmund Carre evaporating water vapor at very low pressures and Ferdinand Carre evaporating liquid anhydrous ammonia. These machines were , not used to produce large quantities of ice, but they produced com- mercial quantities. The compression type of machine introduced in 1835 by Perkins was further developed by Twining, who took out his English patent in 1850 and his U. S. patent in 1853. I n this machine a volatile liquid such as ether, carbon disulphide or sulphur dioxide is allowed to flow through a throttle valve into a region of such low pressure that the boiling temperature of the liquid is low. This liquid will boil by the .abstraction of heat from the substance around the walls of the chamber in which it is placed. The pressure is maintained at a low point by the suction of a compressor which removes the vapor as it is formed and compresses it to a higher pressure. This pressure is high enough to give a temperature of boiling or liquefaction higher than that of a water supply. The water will remove heat from the vapor and cause its liquefaction. The liquid is then passed through the cycle again. In this system the liquid and its vapor are kept separate from everything else by being contained in a closed system. Such a machine produced commercial quantities of ice. There is one other method of abstracting heat, which has been used for some time. This is the compressed-air method. If air is compressed rapidly, its temperature is increased, due to the work which has been done upon it. This air may be cooled to its original temperature by being passed through pipes over which water is allowed to flow, and if this high-pressure air is permitted to drive a piston and do work, the work done will cause a decrease in~temperature, so that the expanded air will be so cold that it will abstract heat from a space or room through which it may be passed in pipes or in the open on its way to the suction of the compressor. In this case PHYSICAL PHENOMENA AND INTRODUCTION 5 the heat abstracted in the refrigerator and that equal to the difference between the works of the compressor and of the expander are taken up by the cooling water. In this machine the compressor and expander work on the same shaft. In all mechanical refrigerating machines the working sub- stance is placed in such a condition that it will abstract heat from the material of low temperature and after this absorption it is placed in such a condition that it will give up this heat and that added to operate the process, to a water supply at a higher temperature than that of the refrigerator space. This is the general principle of all refrigerating machines. In the middle of the last century a development of the western part of the United States took place, and with it arose a desire to ship fruits from the central parts of the country to the East. In 1866 refrigerated boxes holding 200 quart baskets of strawberries and 100 Ibs. of ice were built. These weighed complete 600 Ibs. They proved that fruit could be shipped if kept cool. This was done by Parker Earle. In 1868 Davis of Detroit proposed to insulate cars to handle beef and fish, and in 1872 there were successful experiments. This was the beginning of the refrigerated car industry, which has so extended that in 1910 there were over 130,000 cars in the United States, although only a little over 1000 in Europe. The original refrigeration and even a large amount of modern refrigeration have been accomplished by ice. The machines for the manufacture of .the so-called artificial ice, or better manufactured ice, have made possible the refrigerating of stores or other houses by the use of this apparatus without the em- ployment of ice. In these cold-storage warehouses the vol- atile liquid may be passed through pipes in the various rooms, from which it abstracts heat and vaporizes, or the evaporation of the liquid may abstract heat from a strong brine of a very low freezing-point. This cold brine is pumped through the rooms, removing heat. This latter method is spoken of as the cool-brine system of refrigeration, while the former is called the direct-expansion system. The method of mechanical refrig- eration has made it possible to care for storage in warm countries 6 ELEMENTS OF REFRIGERATION at a distance from ice fields. It has permitted the refrig- eration of certain portions of vessels during long voyages. It has also led to the possibility of the cold storage of food products. In 1905 it was stated that the value of food prod- ucts in cold storage in the United States amounted to over $200,000,000, and the investment in refrigerating apparatus amounted to over $100,000,000. The first long-distance shipment of meats in refrigerators on shipboard was in 1873, but it was unsuccessful. In 1875 successful shipments were made from America to England, and in 1880 Australia shipped meat to England. These ship- ments have so grown that in 1910 the United Kingdom im- ported nearly 13,000,000 carcasses of lamb and mutton and over 4,000,000 quarters of beef from South America, New Zealand and Australia. In 1904 the United Kingdom paid $45,000,000 for fruit, of which one-ninth came from the United States. In 1910 there were more than 800 vessels equipped for the transportation of food products in cold storage. From the above the original importance of this mechanical refrigeration is seen, but with its development further applica- tions have been made and at the present time its use enters into many industries. Cut flowers are kept for a considerable time, and even trees may be held dormant for weeks to prevent budding before trans- planting in the spring. Milk and cream may be kept sweet for some time by means of refrigeration. In the manufacture of wine and beer this apparatus is used to prevent the rise of tem- perature as well as to cool hot liquids. In the refining of oils the apparatus is used for the removal of certain paraffin products. In the ventilation of buildings in warm weather, cooled brine may be employed to cut down the humidity of the air as well as the temperature. This is applied also in metallurgical oper- ations to remove the excess moisture from the air entering a blast furnace, as well as to make the air of uniform quality. In the manufacture of textiles, in the curing of tobacco and in cigar making, in .the making of perfumery, in the manu- facture of photographic films and other products, as well as PHYSICAL PHENOMENA AND INTRODUCTION 7 in developing, the use of the refrigerating machine or its product is indispensable. Even in mining and in excavating the re- frigerating machine has been applied : in the first case to cool warm excavations, and in the second to freeze a ring of quick- sand so that an excavation could be made through this treacher- ous material. In therapeutics, the value of refrigeration is being seen. Mr. W. T. Robinson has stated that he has known of hay fever patients being relieved by visiting cold-storage ware- houses. CHAPTER II METHODS OF REFRIGERATION THE commercial methods of refrigeration or the cooling of materials and spaces are as follows : 1. Natural ice; 2. Air machines; 3. Compression machines using volatile liquids; 4. Absorption machines using volatile liquids; 5. Evaporation; 6. Chemical methods. In describing these methods and in illustrating them, the endeavor has been made to show certain well-known types of apparatus so that the student may study actual forms of machines. The peculiarities of the apparatus must be noted and studied in the examples chosen, since these are found in most apparatus for this purpose. The examples taken are those known to the author, and represent good practice. There are many machines built of value equal to that of those shown, and in buying machinery comparison must be made between all parts before deciding which machine is the best. In the application of natural ice, which is that employed in the common refrigerator, the ice is used to cool the air in contact with it, and then this air, becoming heavy, drops to the bottom of the refrigerated space, displacing warmer air, which rises to the ice chamber, where it is cooled by the melt- ing of a proper amount of ice. Fig. i illustrates the form of refrigerator built by the McCray Company. The ice is introduced on one side of the ice box and the air is circulated downward to the lower part of that side, rising to the provision side of the refrigerator. The walls of the refrigerator are METHODS OF REFRIGERATION made of several thicknesses of materials. As shown, it con- sists of oak, sheathing paper, poplar or some other lumber, sheathing paper, mineral wool, sheathing paper, lumber, felt and opal glass, nine layers in all. This makes a well-insulated box. In Fig. 2 the Jackson system of cold storage is shown. In r^ --'-- ; " Oak -Paper Poplar -"Paper Mineral Wool Paper -*-Poplar Felt Opal Glass FIG. i. McCray Refrigerator. this the cold air falls around the ice and drops into the cold- storage room, after which, on being heated, it ascends to the ice room. The ice is supported on a slat floor and the drip is caught in the necessary pans, from which it is removed by pipes. The columns are properly protected against this drip. The air leaving the ice chest is saturated with moisture at the temperature of the ice, and as it descends into the warmer portions of the box its moisture capacity is increased, so that 10 ELEMENTS OF REFRIGERATION there will not be any deposit of moisture from the air. As the air passes over the goods, there is, if anything, a tendency to take up moisture, and when the air enters the ice chest this Lumber Paper Lumber Bricks Pitch or other Water Proofing Saw Dust between studds Lumber Paper Lumber Air Space Lumber Paper Lumber Dement Concrete ^Pitch Water Proofing Cork Board Pitch Cork Board FIG. 2. Jackson System of Cold Storage. moisture is removed as the temperature falls. This means additional ice melting. This is not a loss, as the evaporation in 'the box abstracts heat and this increases the cooling effect at this point, for which, of course, ice is melted later. The METHODS OF REFRIGERATION 11 methods of insulating floors, walls, and ceilings are to be exam- ined by the student in the figures shown. In Fig. 3 the arrangement of the Dexter system, in which FIG. 3. Dexter System of Cold Storage. the air from the ice room does not enter the cold-storage room, is shown. This drawing is self-explanatory. In all these arrangements the water from the melting ice may be taken 12 ELEMENTS OF REFRIGERATION METHODS OF REFRIGERATION 13 through pipes placed in the cold-storage room. This water is cold and will remove some heat by being warmed to the temperature of the storage room. In this way the apparatus is made more efficient. Fresh air for ventilation may be intro- duced by a duct leading to the outside through the ice room. Fig. 4 illustrates the method of cooling refrigerator cars. In these ice is introduced at each end of the car, and the cir- culation of air, in at the top and out at the bottom, cools the air and maintains a low temperature. The refrigerator car shown has been recently built by the American Car and Foundry Co. for the Illinois Central R. R. for their express service. The cars are 50 ft. long and have a capacity of 40 tons. They weigh 75,700 Ibs. each. They are supported on steel frames. The car proper is built of yellow-pine framing supported on steel under-framing. The insulation is made up of lumber, insulating material and spaces arranged as shown in the figure. The door section is shown on the right of the cross-section as well as the ice chute on the left. The ice is packed in collapsible compartments at each end of the car, and rests on a rack or support at the bottom. This is the Bohn Collapsible ice box. From it the air is deflected by curved slats into the refrig- erated space. It passes through a screen to prevent the en- trance of solid bodies. The rack at the bottom folds up into the end of the car and the slatted front folds up to the roof. The end of the car is protected from the ice by the horizontal strips shown in the cross-section. Ice is charged through the upper doors. Sometimes the ice is broken in a crusher before being introduced and sometimes ice blocks are used. The space for ice is about 3 ft. long, 6| ft. from ice support to roof, and 8 ft. wide. This would hold about 3 tons of ice at each end. There is an insulating plug in each of the four ice hatches, and the covers are:equipped with adjustable latches to give ven- tilation when needed. The water is drained from the bottom. In the above installations, temperatures of 36 to 38 may be obtained in warm weather. When lower temperatures are desired, resort must be made to mixtures of salt and ice. The following table, given by T. Bowen in Bulletin 98, U. S. De- 14 ELEMENTS OF REFRIGERATION partment of Agriculture, gives the temperature resulting from mixtures of ice and salt: Per cent salt in mixture by weight . . o 5 Temperature of mixture 32 27 10 15 20 25 20 II I.S 10 Heat of Solution, B.t.u.per Lb. of Salt. S g g g 8 \ \ \ \ X X \ X ^ ~^- ^ ~--~. - 151 20$ 25$ Weight of Salt as a i of Ice used :x* JT IG . 5. Curve of Heat of Fusion of One Pound of Salt for Different Amounts of Salt. (J. T. Bowen.) The heat of solution of the salt varies from 58 B.t.u. to 1 6 B.t.u., depending on the concentration of the salt. On melting the ice, which requires 143.4 B.t.u., and dissolving the salt, which requires a variable amount, the total heat required will be the sum of that due to the salt solution and the melting of the ice. METHODS OF REFRIGERATION 15 For different percentages of salt added to water the heat of solution is given by the curve of Fig. 5. Since the heat of solution of salt is less than that of ice, the heat of melting of a mixture of ice and salt per pound of mixture 1KA "3 \ ^. 3 ^^ ^ 5 \ ^^ 3 Jj % .. ^^ s^ " O ~^ k. 1 "^ <, 3 no pa 100 3>t Weight of Bait as a Percentage of the Ice used. FIG. 6. Heat of Melting One Pound of Ice and Salt in Different Proportions. (J, T, Bowen.) decreases as the amount of salt increases. This is shown in Fig. 6. The specific heat of the salt brine and of ice must be known to make the necessary calculations for the heat removed and the temperature of the mixtures. The specific heat of the brine for different percentages of salt is given in Fig. 7. 16 ELEMENTS OF REFRIGERATION The specific heat of ice at absolute temperature T, is given by c = 0.5057+0.001863^^-^-, as determined by Dickinson and Osborne. Specific Heat of Salt Briae. > P P P f 3 3 8 8 ^^ ^X X s^ ^ - ^ ^^^^ , - ~-_ 1 ^ ~^- *-^. ^ 0.50 Hty 15^ 20^fc 25$ Salt iis a Percoiitagc of the Water used. 30$ 35^ FlG< 7 ._Specific Heat of Salt Brine for Different Amounts of Salt.) (Bowen.) By mixing ice and salt together low temperatures may be obtained for chilling or freezing. The ice must be brought into intimate contact with the salt, and for that reason the ice is broken into small pieces. This of course necessitates the ice filling a containing vessel, which is placed in the storage room ; although in some cases air is drawn through the mix- METHODS OF REFRIGERATION 17 ture. This is difficult, as the mixture sometimes freezes into a solid mass. Then it becomes necessary to increase the FIG. 8. Diagram of Cooper Gravity Brine Circulating System. surface used to refrigerate the room. Certain patented methods have been proposed. 18 ELEMENTS OF REFRIGERATION The Cooper gravity brine circulation system is shown diagrammatically in Fig. 8. In this ice is broken in a crusher and delivered to the top of the storage house, or it may be crushed at the top after it is delivered. Here it is mixed with salt and introduced into the ice tank. This tank contains a set of coils filled with brine, and con- sequently the mixture of ice and salt removes heat from the brine, cooling it to the temperature of the mixture. After this is done there will be no further melting except that due to the heat loss from the tank. When, howeVer, the valves controlling the brine system are opened, the heavy cold brine will tend to fall to the lowest part of the system, bringing warm brine to the top and producing a strong circulation. The brine then removes heat from the refrigerator rooms, being passed through coils on the walls or ceiling. The ice tanks are about 10 ft. high. The lower part is not very active, as the brine in the coils is cooled by the time it reaches this point, and the salt brine from the melting ice cannot take up any more salt, as its temperature is too low. The ice and salt must be thoroughly mixed before introduction, as the salt is apt to cake. When a new charge is to be introduced, the ice in the tank should be stirred with a stick to prevent any caking. The brine formed from the ice melting is of value for cooling in that it is at a low temperature. It may be passed through the refrigerated rooms in pipes, or it may be used at other points. Cooper claims that two men can handle 4 tons of ice per hour in charging this system and that 4 tons per day will cool a storehouse of 40 cars capacity in average summer weather. The amount required in any case may be computed from the heat losses in the storage house. Air machines are operated in the following manner: Air is compressed in a cylinder A from a pressure pi to a pressure p2. The air is discharged from the compressor through a set of self-acting mushroom valves or by a slide valve, and is passed into cooling coil B, which is surrounded by water. In this coil the air which has been heated by the compressor is METHODS OF REFRIGERATION 19 cooled almost to the temperature of the water, and by this cooling it is reduced in volume and is passed into the expansion cylinder C This is mounted in tandem with the compressor, as in the Lightfoot machine, or beside the compressor attached to the same shaft as in the Allen Dense Air machine. The air-expansion cylinder is arranged in the same manner as the cylinder of a steam engine. It has a slide valve or valve gear, which cuts off the air supply at the proper point and permits expansion to occur. This expansion should be complete (re- FIG. 9. Closed and Open Air Refrigerating Machines. duced to back pressure at the end of expansion). This is accomplished by having the cut off occur at the proper point. ^ As this air expands, doing work at the expense of its intrinsic energy, its temperature is decreased so that when the exhaust pressure is reached the air may be at some temperature between 50 F. and -100 F. The temperature is fixed by the amount of expansion. This cold air is now discharged into a coil D or a room , and it removes much heat before it is brought up to the temperature at which it enters the com- pressor cylinder to repeat the cycle. The system on- tHe left is known as a closed system, while 20 ELEMENTS OF REFRIGERATION that on the right in which the air is discharged into the room E is known as an open system. The air occupying less volume in the air expander than it does in the compressor on account of lower temperature, means that there will be less work returned by the expander than that required by the compressor; hence power must be supplied by an external motor of some form. This may be a steam engine as at F, Fig. 9, or an electric motor may be applied. To show the work done by indicator cards the compressor 7-1 FIG. 10. Cards from Air Refrigerating Machines. and expander cards are shown in Fig. 10, assuming zero clear- ance. This may be assumed, since clearance does not affect the work of a card. These cards may be superimposed and the area 2356 shows the net work which must be supplied if friction be disregarded. This is the work that the motor must supply. The real work, of course, if / is the percentage friction, is , /lOO+A /lOO-A Network=l- 1 area 1 234 ( - ^- ) area 4567. \ 100 / \ 100 / METHODS OF REFRIGERATION 21 In this machine, air, by compression, is put into such a \ condition that the water supply will abstract heat and then, by* expansion, it is put into such a condition that it will abstract^ heat from a place of low temperature. The advantages claimed for these machines are: the use of no chemical which might lead to explosions or loss of life due to accidental escape of gas; the possibility of very low temperatures; simple construction and the accessibility of all parts. The first air machine was designed by Gorrie in 1849. Kirk designed one in 1863. In 1877 the Bell-Coleman improvements made the machine practical, and the application of this machine to ocean steamships made possible the cold-storage shipments of meat. The machine was improved by a number of later inventors. There are few air machines used to-day, owing to the greater efficiency of types of apparatus using other working substances. But efficiency is not always the criterion by which to judge of the advisability of using a certain form of machine. Reli- ability, ease of operation, small maintenance cost, and absence of poisonous substances may be important factors to consider in making a selection. For such reasons air machines are still in use. One of the most common forms of air machines used in the United States is the Allen Dense Air Machine, shown in Fig. n. In this the three cylinders, steam, compressor and expander, are placed beside each other, and are connected to three cranks of a common shaft. The cylinder A in the front of the figure is the expansion cylinder, the second is the compressor cylinder, and the back cylinder is that of the steam engine. Between the compressor and expander is seen the plunger of a small air pump used to maintain the air pressure in the system and make up for any leaks. This is driven by an extension from the cross-head of the compressor. A similar extension on the other side of this cross-head drives a plunger of the circulating pump which forces water through the cooling chamber B placed on top of the machine. Two eccentrics on the shaft control the various valves. The pipe 22 ELEMENTS OF REFRIGERATION C takes the cool compressed air from the coils in the water- cooler to the expansion cylinder A, and after expanding, the air is passed through pipe D to the refrigerator, and then returned to the compressor through E. METHODS OF REFRIGERATION 23 This apparatus is known as a dense air machine. The air is at 60 to 70 Ibs. gauge pressure on the low-pressure side, the high pressure ranging from 210 to 240 Ibs. As will be seen later, the refrigerating effect is due to the ratio of these two pressures and not to the absolute value of each. By using a high pressure on the lower side, the displacement of 24 ELEMENTS OF REFRIGERATION the cylinders for a given amount of refrigeration is materially decreased. The diagrammatic arrangement of the machine is shown by 'the maker, H. B. Roelker (Leicester Allen, 1879, inventor) in Fig. 12. F is the compressor cylinder, in which a special pair of valves, driven by eccentrics G and H through rock shafts, give ample outlet area at the proper time. The com- pressed air is then passed through the copper coil /, placed in the water-cooler B, where it is cooled down almost to the temperature of the water entering at / from the pump K. The pump is driven from the cross-head of the compressor. The water used in the cooler passes through the jacket of the compressor before being discharged. The cooled air passes through the pipe C to the expander A t which is controlled by a riding cut-off valve gear as shown. After expansion the cold air leaves by D and passes through an oil and snow trap L, entering an ice-making box M, or that part of the system in which the lowest temperature is required. The ice box may be a steel brine tank containing coils for the passage of the air, or it may be a double-walled casting containing cells for the ice-making cans. These cells are supplied with brine to fill the space between the casting and can, thus conducting heat from the can to the air at a higher rate than that at which it would otherwise pass through an air space. The hollow part of the casting is that through which the air passes. The air is next conducted to the refrigerating room, where the temperature need not be so low as that required to make ice. If a low temperature is desired in a room, some of the low-tem- perature air will have to be taken directly to that room. The air is distributed through the room in coils of pipe N and then is taken to a water butt, where it cools drinking water to 40 F. or 50 F. The air is then returned to the compressor through the pipe E. If the air is still at a low temperature, it is some- times passed around the pipe C, and this cools the air going to the expander so much that a very low temperature is ob- tained. The pump is the air-charging pump driven from the cross-head of the compressor. This pump draws air through METHODS OF REFRIGERATION 25 its plunger, and after compression the air is delivered to the trap P, which is surrounded by cold water. This cools the air and causes a large part of the moisture brought in from the atmosphere to be separated and drained off. This air is then delivered to the pipe E and is mixed with the air going to the compressor. The valves Q and R cut off the low-temper- ature parts when it is desired to operate the by-pass 5. The valve T allows hot air to enter the expander from the com- pressor and thus pass into the trap L, removing grease and snow from it. The trap or separator L has a double bottom or steam jacket which may be used to melt any congealed oil or water, and so open up the line if closed. To start this machine, the blow-valve on the expander and petcocks on the traps are kept open until no more grease passes through. Then the valves Q and R are opened and S closed. After this T is closed. The circulating water is then turned on, and gradually the low-pressure side should be charged by until a pressure of 60 Ibs. is reached. The high- pressure will then be 210 Ibs. The petcock on the water trap P should be opened to keep the water level below the half-full point. The stuffing-boxes, which contain three or four metallic rings, an oiling ring and three or four rings of soft packing, should be supplied with oil. This oil keeps the packing tight with little tightening of the gland, and consequently little' friction. These stuffing-boxes are placed at places where the greatest loss of air occurs. The sight-feed lubricators are con- nected to the stuffing-boxes. The air pistons are packed with cup leathers which last about two months for steady work. They are made of f in. thickness and are kept flexible by soaking in castor oil. Once or twice a day the machine is cleaned of oil and grease by opening S and closing Q and R, ana then opening T, T' and T" . After this, steam is passed into the jacket of L and the petcock is opened. A blow-off from the expander is also opened. This is done for about one-half hour. A change in the ratio of the two pressures is due to leaky pistons, while a drop in the low pressure is due to leaky stuffing-boxes. These machines are made in small sizes: 26 ELEMENTS OF REFRIGERATION the largest are of 3 to 4 tons capacity. They are used chiefly for marine work. There are a number of foreign air refriger- ating machines. Such firms as Haslam & Co., J. & E. Hall, and I. & W. Cole are engaged in making these. They vary only in the matter of details from the machine just outlined, and for that reason these will not be described. The system of refrigeration using a volatile liquid is shown in Fig. 13. To be a little more definite, assume that anhydrous ammonia is used as the working substance. The compressor A relieves the pressure in the coil B by drawing vapor from FIG. 13. Compression Refrigerating Machine. the coil, since the coil is connected to the suction side of the compressor. The vapor thus removed is compressed by A and delivered under pressure into a condenser coil C. The vapor will be compressed in C until the pressure is such that the temperature of saturated ammonia vapor at that pressure is slightly higher (about 10 to 20) than that of the water coming from the supply D. When this pressure is reached, the water, having a lower temperature than that of saturation of the ammonia, will abstract heat from the ammonia and cause it to condense so that liquid ammonia will flow into the receiver E. If now the pressure in the coil B is such that the tempera- METHODS OF REFRIGERATION 27 ture of boiling for ammonia at that pressure is above the temperature of the substance around the coil B, the ammonia gas and liquid in the coil will give up heat to the substance through the coil and will be cooled off, but nothing further can happen. If, however, the boiling temperature corresponding to the pressure is less than that of the substances around the coil J5, then heat will flow from them into the ammonia in the coil and cause the liquid to evaporate, requiring the further action of the compressor to keep the pressure low enough to remove heat from the substances near the pipe. Of course, if the first condition were true, no vapor would form and the action of the compressor would reduce the pressure so that the boiling temperature would at least be low enough to remove heat from the substances. The supply of liquid ammonia is regulated by the valve F, known as an expansion valve. It is in reality a throttle valve, throttling the liquid ammonia from the high pressure in C to the low pressure in B. The coil B may be placed in a room to be refrigerated or it may be placed in a tank G, containing brine of a low freezing-point. This brine is cooled and sent out to rooms which are to be refrigerated, or to ice tanks, and after receiving the heat, the warm brine is returned to the tank to be cooled again. The first system is known as the direct-expansion system, while the latter is called the brine system of refrigeration. The various types of compressors used will be described in a later chapter. At this point, however, one form of com- pressor will be shown in Fig. 14. This is a steam-driven com- pressor of the Frick Co. A Corliss steam cylinder A drives a shaft B with two cranks. To the steam-engine crank is connected the rod of one ammonia compressor, while on the other crank at 180 is attached the connecting rod of the other compressor. Thus one steam piston operates two ammonia pistons. In some cases the crank to which the two connecting rods are attached is of the center type; three bearings are then used. This compressor is single-acting. Low-pressure ammonia enters at C and passes into the cylinder on the up-stroke of the piston 28 ELEMENTS OF REFRIGERATION D. The long stuffing-box E is quite a common feature of all compressors, as is the long piston with a number of piston rings. These are necessary to prevent the escape of ammonia, ex f which is poisonous and expensive. On the down-stroke of the piston, the large suction valve in the center of the piston is opened by the vacuum produced on the upper side of the piston, and vapor is drawn over to that side. On the return stroke of the piston, the vapor is compressed in the cylinder until the METHODS OF REFRIGERATION 29 pressure is slightly above that in the discharge space E, when it opens the valve F at the center of the head of the cylinder. This valve is forced down by a small spring so that there is only a slight increase in pressure above the line pressure before the valve opens. The vapor pressure in the discharge holds it to its seat on the down-stroke of the piston. The cylinder head G is not bolted fast to the cylinder barrel. It is held down by the springs H which press against the main head /, attached to the barrel. The purpose of the safety compressor head is to avoid the danger of blowing off a head if anything should lodge on top of the piston. If the suction or discharge valve should break, or if scale should accumulate and lie on top of the piston, the small clearance which exists in this com- pressor would not be large enough to care for this material, and with a rigid head the cylinder would break. With the safety head the springs would yield and permit the head to lift. If for any reason liquid ammonia were to collect and the discharge valve would not relieve it, then the head would rise. Around the cylinder is a water jacket / for the removal of some of the heat of compression. The value of the jacket is questioned by some. If too much water is not used, the heat removed will not have to be taken out in the condenser, and so nothing is lost. Moreover, any heat removed during compression decreases the work, so that there is some saving by the judicious use of the jacket. If much water is used, there will be a loss due to the cost of water being greater than the saving due to the jacket. K is an indicator valve and L is a purge valve used to manipulate the compressor. The layout of a plant using the De La Vergne apparatus is shown in Fig. 15. In this the vapor, or, as it is usually called, the gas, enters from the refrigerating rooms or brine tank, and passes to the suction side of the compressor. This line is connected to the gauge board, where a suction gauge is in- stalled. This gauge is, of course, controlled by a valve to permit of its removal and repair. The suction is sometimes connected to the liquid line by an equalizing pipe for manip- ulation of the plant. The compressed gas then passes over 30 ELEMENTS OF REFRIGERATION METHODS OF REFRIGERATION 31 to the condenser. This is a coil of pipe made of return bends. The hot gas enters at the bottom and as it passes upward it is condensed, special bends being used to remove the liquid at different places. These various drip lines are connected, and finally the liquid is delivered to the storage tank B, from which it discharges through the expansion valve C into the expansion coil D. The various euqalizing pipes serve to equalize pressures at various points of the system, so that syphonic action may not be set up. The liquid after entering the re- frigerator is changed into vapor and returned to the compressor. The passage through the scale separator E removes the danger of scoring the cylinders. The valves^at the top of the oil sep- arator A and condenser are to rid the system of non-condensible gases which collect there. These gases are due to air which may be drawn in, or from the oil which may be decomposed. In some cases ammonia may be decomposed. The cooling water is discharged from the pipe F. There are other substances used in compression systems. Sulphur dioxide, carbon dioxide, and methyl chloride are the common ones spoken of to-day. Various ethers and alcohols have been used and certain mixtures of liquids, such as C02 and 862, have been tried. On account of cost, danger from use, pressures demanded, and sizes of parts, some prefer one substance and some another. The theory underlying all of these is the same, and the description given above would apply to any of them. In all machines the vapor is raised by com- pression to such a pressure that the water supply can remove heat from the vapor and condense it, and by use of the throttle valve it is reduced to such a pressure that it will remove heat from a place of low temperature. The absorption machine depends for its action on the fact that for every concentration of aqua ammonia, or for every per cent of a solution of ammonia and water, which is anhydrous ammonia, there exists a certain temperature-at which the solution will boil under a given pressure. Thus, if 35% by weight of a solution of aqua ammonia is NH 3 , this will boil at 227 F. under a pressure of 170 Ibs. gauge, and the 32 ELEMENTS OF REFRIGERATION same solution will boil at 110 F. if under 15 Ibs. pressure. Now ammonia under 170 Ibs. pressure would boil at 91 F., and at 15 Ibs. gauge pressure it would boil at o F. If water were available at 80 F. and steam at 235 F. or 10 Ibs. gauge, the following might be done: If the aqua ammonia or liquor of 35% concentration in the generator A be heated by the steam at 235 F. in the steam coil B, the solution will boil and the ammonia and water vapor will produce a gauge pressure of 170 Ibs., and this is sufficient to have the ammonia condense in the condenser C if water at 80 F. is passed over the pipes. If the ammonia collected FIG. 16. Elementary Absorption Machine. in the receiver D is passed through the throttle valve E into the coil F, where it may abstract heat from brine, it will boil at o F., if the pressure is maintained at 15 Ibs. If an aqua ammonia solution in the tank G, called an absorber, is not allowed to get above 110 F. by the cool water coil H, and is not allowed to get stronger than 35% concentration, it will absorb ammonia and keep the pressure in the absorber and the line leading to F at or below 15 Ibs. gauge. To keep the solution in the absorber in condition to absorb ammonia, the weak liquor in the generator, from which the ammonia was removed, is allowed to flow into the absorber, the pump 7 forcing the strong liquor from G to A . METHODS OF REFRIGERATION 33 This is the explanation of the simple absorption machine, but there are several refinements which are used. Certain phenomena will have to be described. When an aqua solution boils, not only ammonia escapes, but also water vapor. More- over, the heat supplied will have to be not only that required to drive off the ammonia (heat of solution) and that required to .evaporate the moisture, but also enough to superheat the ammonia vapor and water vapor, since these leave the gen- erator in a superheated condition. This excess of superheat must be removed and to reduce the amount of heat to be taken out by cooling water, and to reduce the heat supply to the generator, the cool strong solution coming from the absorber is caused to flow over trays through which the heated gases pass from the generator A. In this way the liquor is heated and economy effected. This apparatus is known as the an- alyzer, K. The water vapor condensing in the condenser would absorb some ammonia and reduce the efficiency of the apparatus. To reduce this loss it is customary to pass the vapors leaving the analyzer through ] tubes L over which the cool, weak solu- tion from the absorber, or water from the condenser, flows. In this way the temperature of the mixture of ammonia and water vapor is so reduced that most of the water vapor is condensed and separated by the separator M, and sent back to the analyzer. L is known as a rectifier or dehydrator. Of course, this water absorbs ammonia and reduces the amount sent to the condenser, but it is not delivered to the condenser and so causes no trouble. The last change which is introduced for economy is to pass the warm, weak solution, which is to go to the cooled absorber, around pipes carrying from the absorber the cool, strong liquor, which has to be heated. This interchange saves much heat. The apparatus is known as the interchanger, /. Before passing to the actual arrangement, one other point must be mentioned. The solution is changed from one con- centration to another in the absorber and in the generator, and it must be remembered that it is the weak concentration which 34 ELEMENTS OF REFRIGERATION fixes conditions in the generator and the strong concentration, those in the absorber. The heat of solution when aqua ammonia changes from one concentration to another must be cared for by the cooling coil in the absorber, so that there is no increase in tempera- ture, which would cut down the possible concentration. The computations for this system will be given in the next chapter. Fig. 17 shows the . absorption machine diagrammatically. In this arrangement the strong solution in A is boiled by the steam in B. The vapor passes through the analyzer K, where - ^ c 1 t i ) 1 FIG. 17. Complete Diagram of the Absorption Machine. it meets the down current of warmed strong liquor coming from the exchanger /. This cools the vapor and warms the liquor, and, it may be, drives off some ammonia. The vapor then passes to the rectifier or dehydrator, L, which is cooled by the strong liquor pumped by pump / from the absorber. This solution is cool enough to condense most of the moisture in the vapors. The water formed absorbs ammonia, and this liquor is removed by the separator M, and is passed back to the analyzer. The liquid from the condenser C passes to the receiver D and through the valve E to the expansion coil F, in the brine tank. From the absorber G with its cooling coil H the liquor is pumped by 7 to L and then to the inter- METHODS OF REFRIGERATION 35 36 ELEMENTS OF REFRIGERATION 8, METHODS OF REFRIGERATION 37 changer or exchanger /, after which it enters the analyzer. The weak liquor from A passes through the exchanger / to the absorber G. Fig. 1 8 illustrates the construction of an actual absorption machine made by the York Manufacturing Company. The condenser, absorber, and expansion coils are all of the exposed- coil type. The water lines going to condenser, deny dra tor, and absorber are not shown. Purging valves are shown at various high points. They are connected by purge lines which are not shown. For purging this system the best location is at the absorber, for here all of the ammonia is absorbed, and the gas remaining is true non-active gas. The various parts of the apparatus, especially the expansion coils, should be purged into the absorber, so that any ammonia coming over may be condensed. Fig. 19 shows the equipment of an absorption plant as made by the Carbondale Machine Co. This differs from that of Fig. 1 8 in that a double-pipe condenser is used, instead of an atmospheric one; the absorber is a tubular absorber; the weak liquor is cooled before entering the absorber and the expansion coil is in a brine cooler. The action of the apparatus can be followed from the description above. The evaporation of a portion of a body of water, so as to freeze the remaining portion, has been used in a natural way for centuries. One of the first successful machines acting on this principle was made by Edmund Carre about the middle of the last century. The apparatus consisted of an air pump attached to a cylindrical vessel containing sulphuric acid. A carafe containing water was attached to the vessel by a hose and then the air pump was started. As the pressure was re- duced, the water in the carafe would boil, due to its own heat, and the sulphuric acid would absorb the water vapor, lower- ing the pressure still further. The heat of vaporization of the vaporized water would be taken from the water in the carafe until finally this removal of heat would cause the re- maining water to be frozen. This invention has been followed by a number of patents, 38 ELEMENTS OF REFRIGERATION and some actual installations. John Patten has invented apparatus for ice manufacture on a commercial scale, but the value of such installations has not been proven. A. J. Stahl has used a Patten plant at South Bend, Indiana, for the pro- duction of 30 tons a day. The drawback is to obtain the high vacuum necessary for freezing. Water boils at 32 F. when the pressure is less than 0.08 lb., or 0.16 in. of mercury. A still lower pressure is required to freeze ice in a short time. That such ice is pure is assumed, because the expansion of the gases within living organisms at this low pressure causes the organism to rupture. Under very low pressures the evap- oration is so rapid that the ice forms immediately. In one type of machine, patented by J. H. J. Haines in 1901, an air pump was attached to a vessel containing water to be frozen, to the space outside this vessel and within an iron receptacle, and to a vessel containing sulphuric acid. As the air pump was operated, the whole system was exhausted. The space outside the water vessel being exhausted, prevented heat from passing across and so, when the pressure was low enough for the water to boil by its own heat, this heat could come only from the water, since the vessel was well insulated from the outside by the vacuum space. This abstraction of heat caused the remaining water to freeze. The acid in the third vessel absorbed the water vapor formed and thus reduced the pressure. In the apparatus patented by W. T. Hoofnagle in 1903, water to be made into ice passes through a vessel A , Fig. 20, which may be used to clear the water or filter it. It enters the chamber B, in which it is sprayed over a series of trays; the fan at the bottom keeps up a circulation. The chamber is connected to the intermediate cylinder D of a three-stage compressor or air pump. This reduces the pressure in B to such an extent that the water is de-aerated, and a small amount of evaporation cools the water. This is admitted from the pipe E into a chamber F by two valves. The chamber F is connected to the low-pressure cylinder G of the three-stage vacuum pump or compressor. The air and water vapor drawn METHODS OF REFRIGERATION 39 out by G is sent to D and after compression it is finally delivered by H. In the chamber F are two trays which are oscillated by rods operated by cams. When in the position shown, water is discharged from the nozzles on these trays, and as it flows along the tray the evaporation of water under the very low pressure causes the remaining water to freeze, making a -cake of ice. It is considered advisable in all these machines to spread the water in a thin layer so that freezing may take place readily, FIG. 20. Hoofnagle Vacuum System of Ice Making. as evaporation can occur over a large surface. Patten sprays his water from a movable head. Another machine for which claims are made is that due to Le Blanc. In this the vacuum is obtained by steam aspirators in series, each compressing the air exhausted by the previous one. By using the Le Blanc condenser pump, this apparatus is used to advantage. In this country the development of this machine is being made by the Westinghouse-Le Blanc interests. This apparatus is being developed for use on ships of the French navy, on some of which serious accidents occurred by the 40 ELEMENTS OF REFRIGERATION bursting of the parts of other forms of refrigerating apparatus. The description of these machines is found in Ice and Refrig- eration, for July, 1912, and Aug., 1910, and Power, Jan. n, 1916. The chemical process refers to the cooling of water by the addition of some soluble chemical. If ammonium nitrate is added to water, the temperature of the solution is much lower than that of the water, a tempera ture^^rease of 40 being obtainable in this way. If the vessel cJMaining the solution surrounds some object, heat will be abstracted and even ice may be formed. If calcium chloride is dissolved in water, a reduction of 30 can be obtained in the jemperature of the water. After this the salt may be recovered by evaporation and used again. This principle has been used for actual appa- ratus to produce low temperatures. CHAPTER III THERMODYNAMICS OF REFRIGERATING APPARATUS WHEN ice perature some of be possible to reduce is difficult to tell at just what tern- forms, and also, after forming, it may perature of some of the ice. Hence 11 FIG. 21. Cards from Air Machine. the amount of heat required to form a pound of ice is not definite. However, if ice melts, the melting does not begin until 32 is reached, and it continues at this temperature until all of the ice is melted. For these reasons the amount of heat required to melt a pound of ice is used as a unit rather than that removed to make a pound of ice. Refrigeration is usually measured in tons of ice-melting capacity per twenty-four hours. Since the latent heat of fusion of ice is 143.4 B.t.u. per pound, according to the latest 41 42 ELEMENTS OF REFRIGERATION experiments, this unit means the removal of 286,800 B.t.u. per twenty-four hours, or 199.2 B.t.u. per minute. The air refrigerating machine has a compressor and an expander, the indicator cards of which are shown in Fig. 21. The expansion and compression curves are of the form pv n = const., and the compression is from the pressures pi to p2. The cards are shown with no cleara^^ The area of the card is Area 3-2-10-11+ area 10-2-1-9 area 4-1-9-11 or />2^2+ I pdv^piVi = area, . . . (i) Jm XC VI n , const. v l ~ n pdv = const. I v n dv= - } i- *= (3) i n Hence Area = (^2 piVi)( i -) .... (4) \ i n/ YI \ f \ ni (6) ni since pv = MBT for perfect gases, where p = pressure in Ibs. per sq.ft.; v = volume in cu.f t. ; M = Ibs. of gas; B = constant - . Ig44 ; mol. wt. gas T = absolute temperature in deg. F. THERMODYNAMICS OF REFRIGERATING APPARATUS 43 k i By the thermodynamic theory B=-Jc p . k Hence Area = work = MJcSTi TI]. ... (7) k n-i The temperature T\ is fixed by the temperature desired in the refrigerator. If the system is open (air discharged from expander into cold room), TI is the temperature of the room, while if a closed system is used, T\ must be about 10 below the cold room, or the warmest place refrigerated, since T n~~ T* vf % M Net work iK i*fl expression for (16) -r-), . (17) (18) (19) The effect of clearance is seen from Fig. 22, in which the compression 12 is followed by the discharge 2 2', and then THERMODYNAMICS OF REFRIGERATING APPARATUS 45 the air 2 '3, which is retained in the clearance space, expands from 2' to i'. The net work is 1-2-2'-!', and the net amount of air drawn in is z'-i. The temperature at 2' is that at 2, hence that at i' is the same as at i. k n i K n i (T 2 -T 1 ), . '.'.. V. (20) n ni (21) where M = M\ M'i, or the weight taken in from i to i'. This expression is the same as that in Eq. (7) without clearance. There is no effect of clearance on the work of a compressor for which the expansion and compression lines are complete, and have the same exponent. This may be said of an expander also, when the cutoff is such that the expansion is complete or just reaches the back pressure at the end of the stroke, and the point of compression is such that the compres- sion is just carried to the initial pressure. The above is true as far as indicated work is concerned, but the work required to drive the compressor is slightly greater with clearance, as displacement must be increased for a given discharge if clearance is present, and there is consequently more friction. Let the clearance 2' 3 be / times the dis- placement Vi V'z or D. r That is, let The volume of air taken in is V\ V f i, or 46 ELEMENTS OF REFRIGERATION The expression within the bracket is known as the clear- ance factor. V For the expander with complete expansion and compression MBT 7 The refrigeration is produced by adding heat to the air, increasing the temperature from T 7 to the original TI, at constant pressure. Hence Refrigeration = M c p ( T\ T 7 ) = 1 99 . 2 X tons of ref . ; . . . (25) M = weight of air required per minute; c p = specific heat at constant pressure = 0.24 for air. The heat removed in the cooler is given by t -q f l n). -. .- (26) M = weight of air per minute; G = weight of cooling water per minute; Refrigeration . , The expression, in B.t.u. s, ~ - is known as the Work refrigerating effect. With no friction this becomes MC,(TI-TI) i (27) rp rp I Now rrr\ ) 2 1 1 THERMODYNAMICS OF REFRIGERATING APPARATUS 47 since t Ti TI \pj /. Ref . eff . = = = ^-. T 2 _ 1 2 1 1 This shows that as T 2 -Ti becomes smaller the refrigerating effect or the refrigeration per unit of work increases. The general expression is Ref.eff. = If a problem is given the following steps are taken: (a) TI is fixed by the temperature of the room or place to be cooled and TQ by the temperature of the cooling water. Of course the coldest water should be brought in contact with the coldest air, or the air and water must flow in opposite directions along the cooling surface, giving a counter-current flow, (b) By (18) and (19) the temperatures T 2 and T^ are found after assuming the ratio . It will be noted that T 2 and TV depend pi upon the ratio , and not upon the actual values of the pres- pi sures. (c) By (25) M, the weight of air per minute, is found for a given number of tons of refrigeration, (d) G, the amount of cooling water per minute, is found by (26). (e) The dis- placement of the compressor per minute is found by (23). (/) The displacement of the expander per minute is given by (24) and the horse-power is given by dividing (17) by 33,000. H.P. to drive machine = ^-ro-d-/)^-^)]. . (29) 33, ooo vi-// There are some changes to be noticed before proceeding with a problem. If in the expander the cutoff is too late, 48 ELEMENTS OF REFRIGERATION the areas 7-10-9 and 11-12-13 will be lost, decreasing the work done by the expander and increasing the net work done by motor which drives the machine. Moreover, TV is now higher than it was when the air was expanded down to the lowest pressure. This gives less refrigeration, since the free expansion 7 to 9 is throttling action and will not cool the air. The temperature at 13 is higher than the temperature T Q of the incoming air, because T'i is higher than TI would have been if the expansion were complete. This even makes TQ 13 12 FIG. 23. Incomplete Expansion and Compression in Expander. higher than it should have been, increasing TV and still further cutting down the refrigeration This incomplete action makes the displacement Vg Vi 2 less than it would be with complete expansion and compres- sion, FIO Fia. This is the only advantage. Since one would be foolish to design an expander with incomplete expansion and compression, this will not be further investigated although by calculations the various temperatures may be found for any conditions. Note. The following discussion gives the temperatures, assuming no compression, with expansion such that p^=2pl. Air entering at temperature T 6 must compress the clearance air ID, at temperature Tr, from pi to p 2 . The energy in the air contained in the cylinder is - . THERMODYNAMICS OF REFRIGERATING APPARATUS 49 The air brought in from the storage tank to bring this up to the pres- sure p 2 is m Ibs., and the energy entering from the tank at constant pressure is mc p T 6 . The energy after mixing is - . k i Hence . RI k I (30) Now the weight of air in the clearance space is -'-' ......... oo The temperature of the mixture in the clearance space, after the air enters to fill the space, is given by* T _ PJD (m+m')B f ID (p 2 -pi)B pi \ (p2 ~ Pl '~k^ , ID J(k-i)c p r 6 + J\, L JcpTe +pl BTr\ f*. A.\ In this TV is higher than T 6 and T 6 " is higher than T 6 . If now the air at volume Fo expands from pressure p 2 to a pressure 2/>i, the temperature of discharge will be n-l 50 ELEMENTS OF REFRIGERATION This will be the temperature of discharge, since the free epxansion is a throttling action of constant temperature. Even if r 6 were equal ! n-l to r 6 , Ti would be higher than it should be by the factor 2 . This means that the refrigeration is decreased. The work returned by the expander in this case is (35) These quantities may all be computed. The compressors, as usually constructed and used, operate in such a manner that complete expansion and compression result, and conse- quently there is no effect, due to clearance space, on the temperature or work of that part of the apparatus. The effect of moisture in the air is to reduce the refrigerating effect and increase the net work. Of course, this moisture effect is not felt if the same air is used 4 over and over again, since the first chilling dries the air and removes the moisture. Air contains a certain amount of moisture. The amount is told by a hygrometer. One form of this apparatus consists of two thermometers, one of which has a wet wicking around it. If now, these two thermometers are whirled in the air, it will be found, usually, that the wet-bulb thermometer Tvill read less than the dry one. The amount by which the wet bulb is lowered depends on the moisture present in the air. If the air is saturated with moisture, there will be no difference, while if the air is dry, there is a large difference in the tem- peratures recorded by each. The amount of moisture is desig- nated by relative humidity. Relative humidity is the ratio of the amount of moisture, m a , in a cubic foot of air compared with the amount of moisture, m s , to saturate it, or / ,N (36) p = relative humidity ; m a = amount of vapor in i cu.ft; m s = amount of vapor to saturate i cu.ft, THERMODYNAMICS OF REFRIGERATING APPARATUS 51 If the vapor pressure (vapor tension or steam pressure) at a given temperature is p s , the actual pressure, p a , exerted by the vapor of relative humidity p is Now, if the wet bulb reads /, and the dry bulb t d , and the barometer reading is given by Bar, then according to Carrier _p w Bar -ft, tg-ty ~ ~ where p = relative humidity ; p w = steam pressure corresponding to /,; p d = steam pressure corresponding to / tf ; Bar = barometer reading; t d = dry-bulb reading; tto = wet-bulb reading. If the air of relative humidity p and temperature T\ enters the compressor, the moisture and air during compression will act as a single gas and the temperature T 2 will be found as before. or The work of compression will be J[Mc p +mc' p ][T 2 -Ti], ..... V (39) or w s = weight of i cu.ft. of saturated steam at temperature T\\ p s = saturation pressure of steam at temperature T\ ; _iS44_ 52 ELEMENTS OF REFRIGERATION When this air is cooled to temperature T 2) an investigation must be made to see if any of the moisture is condensed. If none is condensed the mixture acts as a gas and If now VQm S Q>m no moisture is condensed and m for low pressures, and then m m s V = amount condensed in the cooler. In the first case m Ibs. enter the expander and in the second case m S QV Q enters the expander. This moisture is condensed and frozen as soon as it enters the expander. It then gives up the heat 5.4) =c, ..... (43) to the cylinder walls and leaves the volume of the air n-^p. . . ',-. '.". . (44) p2 The heat c taken up by the cylinder walls may be assumed to be gradually restored during expansion. If this is divided between the temperatures T Q and T 7 , it might be assumed that the amount returned from the walls per dt degrees is J- where a is the value of the fraction. Hence the equation for work at the expense of internal energy and the heat returned is = -pdV, .. ..,-'. (45) THERMODYNAMICS OF REFRIGERATING APPARATUS 53 Jc . , (46) From this T 7 may be found. The work done is W e * = p 2 V & +,pdv -piV 7 = MBTQ+J(mc t +Mc v +ma)(T Q -T 7 )-MBT 7 = J[mct+M(c v +AB)+ma][TG-T 7 ] = J[mc^Mc p +ma\[T Q -T 7 } ....... (48) The net work is r 7 ][i-/]. . (49) The refrigeration is JlfcJtTi-Tt] ....... (50) The refrigerating effect is Work n From the expression for refrigeration it is noted that only air is considered to be delivered back to the compressor, and consequently unless this air received moisture from the space through which it was passed, this problem is of little value. If a large quantity of water is injected into the cylinder during compression to reduce the amount of work by cooling, of course the above discussion of the expander would be im- 54 ELEMENTS OF REFRIGERATION portant, and of course some means would have to be used to remove the ice formed constantly in the cylinder. If the water injected into the cylinder at each stroke is m pounds, the following equations should hold for the com- pression stroke. J[Mc,dt+md(q'+xp)] = -PdV=-(P-p)dV-pdV, . (52) J[Mc,dt+mdq'+mpdx+mxdp] = -pdV-(P-p)dV, dq' ' = dt, approximately; dV = m[(v"-v')dx+xd(v")]. = Jm[p+Ap(v"-v')]dx+mpxdv" = Jm(rdx+Apxdv fr ). . . . . . . . (53) Now dp = dr-Apdv"-A(v"-v')dp, xdp=xdr-Apxdv"-Ax(v"-v')dp. . . . (54) But j.dt (55) Hence r // J JvJWw / s\ v =xdr- (56) ocrdt\\ M --r) \ = - MET xdr l 2 - 1 [Mc,+m] log. +w ! --f =AMB log, . . (57') J- 1 " w THERMODYNAMICS OF REFRIGERATING APPARATUS MBT 2 V 2 Pa- pa ', (60) (61) Ta, V^_V^ _ V, "T 2 ^T~ AMBlCZe T 2 [Mc,+m} log, ^+^%- -^=AMB ^ Equations (59) and ($7") will give 2 and T2. They are to be solved by trial. p2 and r I c p dt+Apv' = q'+r+ j c p dt. . (70") jTaAt JTsat 64 ELEMENTS OF REFRIGERATION The specific heat of superheated vapor is given by the letter c p . This may be a constant or a variable. In most vapors used for refrigeration, the value of c v is considered constant for lack of better information. The value of v is found from the characteristic equation of the superheated vapor, which is usually taken in the form p(v-c)=BT+ap a . (72) FIG. 27. Cards from Vapor Machines. Using these equations, Figs. 24, 25, and 26 are carried out beyond the saturation line into the superheated region as shown. The p-v diagram from the vapor machines with an expander is shown in Fig. 27, considering no clearance, as compression and expansion are complete. The vapor is drawn into the THERMODYNAMICS OF REFRIGERATING APPARATUS 65 / / ' ; \ 2' 5 / 75 F \ 1^^^^ i90 32F A \ i \ 4 / - \ 10 F \ 1' J i 6 0" 6' 1 \ / \ / \ / \ ] - \ -. Abs. Zero a 6 c d ' c / 9 0. 20 0.25 0.50 0.75 1.00 1.25 Entropy FIG. 28. T.S. Diagram of Cycle of Refrigerating Machine Using a Volatile Fluid. 66 ELEMENTS OF REFRIGERATION compressor from 4 to i and is compressed from i to 2. This compression not only raises the pressure, but also the tem- perature at which the liquid will boil or the vapor will con- dense. Hence, if sufficiently high, the pressure will have a sat- uration temperature above the temperature of a water supply, and if passed through condenser tubes with water on the out- Entropy FIG. 29. I.S. Diagram of Cycle of Refrigerating Machine Using a Volatile Fluid. side, the vapor will condense. The vapor is driven out from 2 to 3 into the condenser in which heat is removed to condense the vapor. The liquid, which occupies a very small volume 3-5, is admitted to the expander and expands from 5 to 6, after which it is allowed to enter the expansion coils, where it abstracts heat from the cool material outside of the coils because its pressure has been so reduced that the temperature of boiling is lower than the low temperature of the substance around THERMODYNAMICS OF REFRIGERATING APPARATUS 67 the coils. The liquid boils and finally occupies the volume 4-1. The combination of these two cards gives the net card Constant Heat Content FIG. 30. I.S. Diagram of Cycle of Refrigerating Machine (Inclined Axes). 1-2-5-6, in which 1-2 and 5-6 are adiabatic, and 2-5 and 6-1 are constant-pressure lines. This figure may be placed on the temperature-entropy diagram, Fig. 28, or on the i-s diagram, Figs. 29 and 30. On the line 1-2 the compression carries the vapor into a 68 ELEMENTS OF REFRIGERATION drier region, as drawn X2 = i, so that the vapor is always sat- urated and some liquid is present. This is known as wet compression. If, however, x\ as at i' were unity, the com- pression i '-2' would carry the vapor into the superheated region. This is known as dry compression. The compression from i to 2 would require work shown by the area 1-2-3-4 on Fig. 27. A X work per pound = q2+X2p2 gi xiPi +Ap 2 V2 i2 ii. . . (73) In the superheated region the work per pound would still be given by (73') In the same manner the expression for work in the expander AW.=M(i s -io) ....... (74) Now the work required in the expander is so slight that this part of the apparatus is omitted, the complication and friction being of greater value than the work regained. In that case the net work per minute becomes . . . . (73") This expression for work is shown by the area 1-2-5-4 on Fig. 28, since, Area (b-h-$-2) = q f Area (a-^-i-f) area (a-^-h-b) =#in+s. f superheated vapor leaving with 0.027 Ib. of water vapor, and entering at this point are 8.32 Ibs. of liquor of 39.3% concentration. At the lower end of the analyzer the conditions of temperature and pressure are as follows: CONDITIONS AT ENTRANCE TO ANALYZER Boiling temperature ..................... 222 F. Concentration .......................... 30 . 7% Pressure, total .......................... 169 Ibs. o^ o^- Steam pressure ....... 17.86 = 12.15 1730.7 Ammonia vapor pressure ...... 169 12.15 = 156.85 Sat. temp, of steam ..................... 202 . 5 F. 92 ELEMENTS OF REFRIGERATION Sat. temp, of ammonia .................. 81 . i F. Steam superheat ........................ 19. 5 F. Ammonia superheat ..................... 140. 9 F. Volume of i Ib. of ammonia. ............. 2.60 cu.ft. Volume of i Ib. of steam ................. 33 .o cu.ft. Heat content, ammonia .................. 646. 2 B.t.u. Heat content, steam ..................... 1157.4 B.t.u. Weight of steam with i Ib. of NHs --52. . ..= 0.079 & 33-o In passing up through the analyzer the vapor is changed, so that per pound of NHs passing there is 0.026 Ib. of water vapor present at outlet. The original amount was 0.0785 Ib. of vapor per pound of ammonia. This condensation absorbs enough ammonia to make the strength 41.8%. By the method used with the rectifier the amount of ammonia absorbed is 0.04 Ib. per pound of ammonia leaving, and the amount of liquor formed is 0.0957. The steam condensed is 0.0557 Ik. The total amount of ammonia at entrance being M, the fol- lowing holds: M = i.o4Jlf Xi.045, If =1.087. At entrance there are 1.087 Mbs. f NHs. The liquor formed is o.ioo Ib. Hence the liquid dropping back into the analyzer will be 8.25 Ibs. of strong liquor of strength 39.1%, 0.07 Ib. of strong liquor of strength 65%, o.ioo Ib. of strong liquor of strength 41.8%. This gives 8.420 Ibs. of liquor of strength 39.3%. If there were no evaporation in the analyzer, this liquid would fall into the generator, but because there is heat added to liquor by superheated vapors passing upward some ammonia is driven off. Assume that the temperature of the liquor is raised to 192 F. There must be a balance if this is the case. THERMODYNAMICS OF REFRIGERATING APPARATUS 93 CONDITIONS AT 192 F. AT BOTTOM OF ANALYZER Pressure ................. ............. 169 Ibs. Temperature, assumed .................. 192 F. Concentration /8 5 .6+459.6 \ \ 192 +459.6 / 1700-17X38.8 Steam pressure ...... 9r75 Q Q = 5-84 1735.5 Ammonia pressure ............ 169 5 . 84 = 163 . 16 Saturation temperature, ammonia ........ 83 . 5 F. Saturation temperature, steam .......... . . 169 F. Superheat, ammonia ................. ... 108 . 5 F. Superheat, steam ...................... 23 F. Specific volume, ammonia ............ ... 2 . 36 cu.ft. Specific volume, steam ............ ...... 66.3 cu.ft. Heat content, ammonia ................. 628 . 5 B.t.u. Heat content, steam. .... ............... JI 45- 5 B.t.u. 2 "?6 Weight of water vapor per Ib. of NHs. . -^- = o . 035 06.3 The ammonia set free, M, in changing from 39.3% to 38.8%, is given by (8.42 Xo.393-Af) = 8.42 -I.035M, = 8.42(0.393-0.388) = 0.542 = i -(1.035)0.388 0.598 The amount of water vapor leaving is 0.070X0.035 =0.002. The amount of liquor falling into the generator equals 8.420.070 0.002=8.348 Ibs. The amount of ammonia vapor coming from the generator amounts to 1.0870.070 = 1.017 Ibs. 94 ELEMENTS OP REFRIGERATION The water vapor leaving amounts to 1.017X0.079 = 0.080 Ib. The weak liquor left in the generator is equal to 8.348-1.097 = 7.251. This should mount to 7.248, since 0.002 Ib. of water enters the absorber with the ammonia. Weight Balance for Analyzer Entering: f ammonia 1.017 From generator \ { water vapor .... o . 80 From rectifier, liquor 070 From interchanger, liquor 8 . 250 9.417 Leaving: _ ,.- f ammonia i .045 To rectifier \ ( water vapor 0.027 To generator, liquor 8 . 348 9.420 Heat Balance for Analyzer Entering: ammonia. 1.017X646.2= 656.0 From generator , [ steam. . .0.080X1157.4= 92.6 From rectifier and interchanger Heat of liquid of liquor 8.320X (180 32) = 1230.0 1978.6 Heat of partial absorption, = 262O= 262O Heat of absorbed vapor 8.32X0.393X5.147 = 1675 THERMODYNAMICS OF REFRIGERATING APPARATUS 95' Leaving : f ammonia. .1.045X621.4= 650 To rectifier \ { steam. . . .0.027X1140.4= 30.9 To generator, Liquor, heat of liquid 8.348[i92 32] = 1335 . o 2015.9 Heat of partial dilution Heat of absorbed vapor 8.348X0.388X514.7 = 1662 Heat to drive off ammonia 2620 2600 = 20 B.t.u. Excess leaving ........ 2015.9-1978.6= +37.3 B.t.u. Heat of atm. pressure .... 1662 1675 = 13 B.t.u. In other words there is an excess of 44.3 B.t.u. and con- sequently the liquor cannot be warmed to 192. Try 188. Pressure ............................ 169 Ibs. Temperature assumed. . . . ............ 188 F. Concentration ....................... 39.9 This is stronger than the original liquor, so there can be no evaporation. Try 190. Pressure ............................ 169 Temperature assumed ................ 190 Concentration ....................... 39.3 This is possible, as the liquor is just heated to its limit. Hence all will fall into the generator giving as the weight balance the following: 96 ELEMENTS OF REFRIGERATION Weight Balance for Analyzer Entering: From generator, Ammonia i . 087 Water vapor o . 086 From rectifier and interchange^ Liquor 8 . 320 9-493 Leaving: To generator, liquor (8.32+0.096) 8.420 f ammonia. . . , i . 0415 To rectifier [ steam 0.027 9.492 Heat Balance Entering: f ammonia. i. 087X646. 2= 703.0 From generator \ { steam. .0.086X1157.4= 99.6 From rectifier and exchanger, liquor 2032.6 Heat of partial absorption = 2620.0 Heat of absorbed vapor 8.32X0.393X514.7 = 1685 Leaving: To generator, liquor 8.42(190 32) = 1330.0 f ammonia. . . .1.045X621.4= 649.0 To rectifier \ ( steam 0.027X1140.4= 30.8 2009.8 o . _ Heat of partial absorption -* X 2620.0 = 2650 8.32 Heat of absorbed vapor 8.42X0.393X514.7 = 1700 There are 22.8 B.t.u. entering in excess and there are 30 B.t.u. given off to care for the heat in large amounts of liquor. To allow for condensation of vapor above atmospheric pressure, there will be an excess of 15 B.t.u. This gives 37.8 B.t.u. in excess. This would raise the liquor 5 degrees, but this is THERMODYNAMICS OF REFRIGERATING APPARATUS 97 impossible as 192 is too high. Suppose 190.8 is tried. Since at 192 there are 42.3 B.t.u. in excess leaving, and at 190 there are 37.8 B.t.u. in excess entering. Pressure ............................. 169 Temperature ......................... 190 . 8 Concentration ........................ 39.1 Steam pressure ................ 9.50^^ = 5 . 65 Ammonia pressure ............ 169 5.65 = 163.35 Saturation temperature, ammonia ....... 83 . 5 F. Saturation temperature, steam. . . ....... 167 . 5 F. Superheat, ammonia ................... 107 . 3 F. Superheat, steam ..................... 23 .3 F. Specific volume, ammonia .............. 2.35 Specific volume, steam. ................ 78.00 Heat content, ammonia ................ 628 . o Heat content, steam ................... 1144. 9 Lbs. of water vapor per Ib. of NHs-= 0.030 78.0 NH 3 set free.... 8.42 -^^ - = 0.028 \i- 1.030X0.3917 Steam set free 0.028X0.030= o.ooi Weight Balance of Analyzer ($d Assumption) Entering: From generator, Ammonia 1.085 0.028= 1.057 Steam 0.086 0.001= 0.085 From rectifier and interchange^ Liquor 8 . 320 9.462 Leaving: To generator, liquor 8.4200.029= 8.391 f ammonia = i . To rectifier 9-463 98 ELEMENTS OF REFRIGERATION Heat Balance for Analyzer Entering: From generator, Ammonia 1.057 = 646.2= 683.0 Steam 0.085X1157.4= 98.5 From rectifier and interchange^ liquor. . . = 1230 2011.5 Heat of partial absorption 8,48,3x3,3-^-! = - 2020 Heat of absorbed vapor 8.32 Xo.393 X 514.? = 1680 Leaving : To rectifier, Ammonia i .045 X 62 1 .4 = 649 Steam 0.027 X 1 140.4 = 30 . 8 To generator, liquor. . . .8.391(192.8 32)= 1330.0 2009 . 8 Heat of partial absorption Heat of absorbed vapor 8.391X0.391X514.7= 1683 Heat of absorbed vapor ...... 1683 1680= 3 B.t.u. Heat of concentration ....... 2620 2620= o B.t.u. Excess heat leaving ...... 2009.8 2011.5= 2.7 B.t.u. Excess heat, entering .................. = 0.3 B.t.u. If 190 gave 37.8 B.t.u. excess entering and 190.8 gave 0.3 B.t.u. excess entering, the value of 190.85 is probably correct. It is not worth working as close as this and tJ> 37.8 B.t.u. excess entering may be assumed to be cared for by radia- tion, giving the second computation as the one required. The investigation of the generator now follows. THERMODYNAMICS OF REFRIGERATING APPARATUS 99 Weight Balance for Generator Entering: From analyzer, liquor 8 .420 Ibs. 8.420 Ibs. Leaving : To analyzer, Ammonia i . 087 Steam 0.086 To exchanger, Liquor 7 . 248 8.421 Heat Balance for Generator Entering : From analyzer, Liquor 8.420(190 32)= 1330 Heat of partial absorption. = 2650 Heat of absorbed vapor 8.416 Xo.393 X5I4-7 = 1? Leaving: To analyzer, Ammonia 1.087 X646. 2 = 703 Steam 086X1157.4= 99-6 To interchanger, Liquor 7.248(222.0 32]= 1378.0 2180.6 Heat of partial absorption Heat of absorbed vapor 7.248X.307X5i4.7= 1149 Heat for difference in heats of partial ^absorption ............... 26501845= 805 Heat excess in leaving ...... 2180.6 1330= 850.6 Heat in atm. pressure ....... 1149 1700= 551.0 1104.6 100 ELEMENTS OF REFRIGERATION Pounds of exhaust steam at 20 Ibs. absolute pressure, of quality 0.85 required to produce this heat is given by Lbs. of steam = - = i 3 S Ibs. .85X961.7 If 10% radiation is assumed the steam will be 1.5 Ibs. At the discharge of the condenser at 85 F., the pressure is 167.4 Ibs. and the strength of the solution that can be formed is, by (80), 1=0.00471^+0.655, This result is large, and, moreover, the equation is not true for more than 50% concentration. The condition of the liquor is not known. The quantity formed in any case is not large, so it will be assumed that the strength is 70%, and hence on the condensation of 0.002 Ib. of water, the liquor formed will be 0.005 Mb. This gives the following weight balance. Weight Balance for Condenser Entering: From rectifier, Ammonia ............................ i . ooo Steam.. , . 0.002 i. 002 Leaving : To throttle valve, Liquid NH 3 o . 997 Liquor . . , o . 005 i. 002 The heat balance is as follows: THERMODYNAMICS OF REFRIGERATING APPARATUS 101 Heat Balance for Condenser Entering: From rectifier, Ammonia 1.000X572.8 = 572.8 Steam. ..0.002X1108.0= 2.2 575-0 Leaving To throttle valve, Liquid ammonia .......... 0.997X59.4= 59.2 Liquor ................. 0.005(85-32)= 0.3 Heat of partial absorption Heat of absorbed vapor. . . 0.003 X5i4-7= 1.5 59-3 Heat removed ........ ... .575--59-3 = 5 I 5-7 B -t.u. Lbs. of water heated from 60 to 75 per Ib. of ammonia entering condenser (If water from 68 to 75 is used, the amount required will be 73.7 Ibs., or the water from the absorber could be used in the condenser.) EXPANSION OR THROTTLE VALVE AND EXPANSION COIL NOTE. No radiation is assumed from receiver. This action is constant heat content action. Hence i after expansion is that for the liquid at 85 or 59.4 B.t.u. The heat content for dry ammonia at 15 is 534.3 B.t.u. Hence the refrigeration produced is equal to 0.997(534.3 - 59.4) -0.005(85 - ( - 15)] = 472.9. If 10 B.t.u.'s are assumed for leakage, this gives 462.9 B.t.u. of heat abstracted in the expander per pound of ammonia entering the condenser. 102 ELEMENTS OF REFRIGERATION The number of pounds of ammonia per minute per ton of refrigeration is 100.2 0.430 Ib. 462.9 ABSORBER Weight Balance for Absorber Entering: From expander, Ammonia ..................... o . 997 Liquor ........................ o . 005 From interchanger, Liquor ........................ 7 . 248 - 8.250 Leaving: To interchanger, Liquor ........................ 8 . 250 - 8.250 Heat Balance of Absorber Entering: From expander, Ammonia ............. . . . 0.997 X 534.3 = 53 2 - 8 Liquor .............. o.oo5X(-iS-3 2 ) = -- 2 Heat of partial absorption [142.5X70] 893 -- L^.^-Ly Heat of absorbed vapor ............... = 1.5 From interchanger, Liquor ................ 7.248X(76~32) =319.0 Heat of partial absorption ............. = 1845 Heat of absorbed vapor ............... 1 149 Leaving: To interchanger, Liquor ................. 8.25X(7o~32) =313 Heat of partial absorption Heat of absorbed vapor 8.25X0.391X514-7 = 1658 THERMODYNAMICS OF REFRIGERATING APPARATUS 103 Heat entering heat leaving = [532.8-0.2+319-313] + [2580- 1845 -i. 7] -[1658- 1149- 1.5] = 538-6 + 733.3- 507-5 = 7 6 4-4 B.tu. If 60 water enters and is raised to 68 F. in the cooling coil, the cooling water required will be =95-42lbs. per Ib. This is excessive and in practice a greater range of tem perature would be used. This would reduce the quantity. Work of Pump The work done in the pump is given by - 778 (169 20.00) 144 X8. 25 = 4.18 B.t.u. This heat is added by the pump and is cared for by radi ation. The following heat balance is made: Generator 1104 6 Analyzer 11 8 Rectifier 103 i Condenser CIC 7 Expander 4.62 o IO O Absorber 764 4 Pump. A 2 Interchanger f 105.8 j 4.2 (pump) I 49-9(P- 9i) i57i-7 1383.2 187.7 1570.9 187.7 104 ELEMENTS OF REFRIFERATION If i| tons of refrigeration are required per ton of ice, this apparatus would require 1.5X0.43X24X60 = 930^8. of ammonia entering the condenser per day. The steam needed for this would be 930X1.4 = 1305 Ibs. This would require the exhaust of a 21 H.P. engine to supply the steam \24X30 If the steam were supplied by a boiler, the coal required would be = 130.5 Ibs. The ice per pound of coal would be 10 2000 = 15.3 Ibs. In practice these plants yield from 9 to 10 tons of ice per ton of coal supplied. In a test by N. H. Hiller, 60 tons of ice required 3890 Ibs. of steam per hour. Assuming that this high pressure steam is made at the rate of 8 Ibs. per pound of coal, the coal required for 60 tons of ice would be 11,670 Ibs. or 5.8 tons. This gives a value of 10.3 tons of ice per ton of coal. The steam used for this apparatus could have been the exhaust steam from an engine, and consequently the full coal should not be charged to ice-making. To give some comparative figures from the problems in this chapter, the results have been collected in the following table: | o | | S, o , M l 1 c is d g +* IH o ** In tu o *9 II I be v o d 4- 5j 2J +* w ||| <^ afe 111 I! s d H 2 S o w C C 8 C ft IH . w 8 o > o ^ w 3 r^ 3 fc 5^ C 5^ P w ^ ^ F. F. Lbs. Air atmospheric 10 70 58.8 14. . 7 103 . 9 82 2 4 05 24.4 o 95 Air dense IO 7 235 . 2 58.8 26.0 2O.5 4.O5 24.4 o. 95 Ammonia wet 25 80 152 Q 15 6 8 o I 42 252 3 3 2 Ammonia dry .... 25 80 J 53 -9 15.6 7 o 1.58 25.9 2.06 CO 2 wet 25 80 967.0 2OI . 1 1.76 2.96 ^O.O 2.48 SO 2 , wet -25 80 59-7 5-0 22.7 1-43 25-3 3-31 THERMODYNAMICS OF REFRIGERATING APPARATUS 105 The refrigerant to be used is determined by the designer of the plant. Each has certain advantages. Air is the cheapest of all, but jts properties are such that large displacements are necessary, even with dense-air machines, and for ordinary temperature ranges the refrigerating effect is small. Sulphur dioxide and ammonia are objectionable on account of danger to life and property in case of breaks in the system. Carbon dioxide is not objectionable from this cause. The C02 and SO2 are much cheaper than ammonia; when the pressure range is considered it is found that carbon dioxide requires excessive pressures on both sides of the system, thus necessitating steel cylinders, special packings, heavy piping and fittings, but a small size compressor. The pressures with sulphur dioxide are not great and with ammonia, although the pressure is high on the upper side, it is not so high as to require special con- structions. The sulphur dioxide compressor is large as com- pared with the ammonia compressor. Carbon dioxide is near the critical temperature at ordinary water temperatures, and this causes certain changes to be made. As was shown on Fig. 33, this substance may be operated above the critical point. Ammonia is the most common substance employed, but there is a tendency to use carbon dioxide to a greater extent than formerly. Experimental runs have shown that these substances give about the same practical results. The SCb and NHs corrode metals slightly and C02 and SO2 machines being nearer than NHs to their critical temperatures, will not cause excessive pressure if the condenser-water should fail, as has happened with NHs, causing rupture in the system. NHs with oil forms a combustible, which cannot be said of 862 and CO2. Carbon dioxide can be brought in contact with any metal, while NHs and 862 must be kept in contact with iron and steel only. Mixtures of CO2 and 862 have been tried. Methyl and ethyl alcohol and methyl chloride have been used as refrigerants. In refrigeration, 2 gals, of water per minute are generally required per ton of refrigeration. 106 ELEMENTS OF REFRIGERATION The effect of temperature range is seen by the following table, given by Thomas Shipley in the Bulletins of the York Manufacturing Co.: VOLUMETRIC EFFICIENCY, DISPLACEMENT PER MINUTE PER TON AND COMPRES- SOR HORSE-POWER PER TON FOR YORK SINGLE-ACTING COMPRESSOR. Suction Pressure and Temperatures of Saturation. High Pressure by Gauge and Temp, of 5 Lbs. Gauge or -17-5 F." 10 Lbs. Gauge, or -8.05 F. 15.67 Lbs. o c Gauge or F. Saturation. Disp. Disp. Disp. Vol. Eff. per Min. I.H.P. Vol. Eff. Min. I.H.P. Vol. Eff. per Min. I.H.P. Cu.ft. Cu.ft. Cu.ft. 145 Ibs., 82 F 0.79 7.28 1.65 0.812 5. 7 i .4 0.83 ,1 .5 I . 2 165 Ibs., 89 F. . ... 0-775 7-5 1-83 0.797 5-9 1.56 0.815 4 .6 i-34 185 Ibs., 95-5 F.... 0.76 7.8 2 .OI 0.782 6.0 1.72 0.80 4 .8 1.49 205 Ibs., 101.4 F.. . 0-745 8.05 2.19 0.767 6.2 1.89 0.785 S .0 1-63 Suction Pressures and Temperatures of Saturation. High Pressure by Gauge and Temp, of 20 Lbs. Gauge or 5.7 F. 25 Lbs. Gauge or 11.5 F. Saturation. Vol. Eff. Disp. per Min. H.P. Vol. Eff. Disp. per Min. H.P. Cu.ft. Cu.ft. 145 Ibs., 82 F 0.842 3.9 1. 06 0.855 3-4 0.94 165 Ibs 89 F 0.827 4-i 1 . 2O 0.84 3-5 1.07 185 Ibs., 95.5 F.... 0.812 4.2 i-34 0.825 3-6 1.20 205 Ibs., 101.4 F. . . 0.797 4-3 1.47 0.81 3-7 1.32 From the above table it is seen that the range of temper- ature has a great effect, the variation in the table being from 2.19 H.P. per ton to 0.94 H.P. per ton. It is absolutely nec- essary to know conditions before a given problem can be solved. The smaller the range of temperature, the less the H.P. required. The table has been based on tests made on compressors with a clearance of not more than y^" and with no after cooling. With after cooling there would be a reduction in horse-power. To find the engine horse-power, an allowance of 17% must be added for small compressors, and 15% for large compressors to care for friction. To utilize the fact that small temperature range means THERMODYNAMICS OF REFRIGERATING APPARATUS 107 an increase of efficiency, Mr. G. T. Voorhees patented the application of multiple effect to absorption and compression machines, when different temperatures are applicable on the lower side of the system. The compressor system and absorber system are shown in Fig. 35. In this system the vapor from the compressor or rectifier is sent to the condenser and after it passes a throttle valve to reduce its pressure to a point above 1st Throttl Brine Cooler 24F. Pump Inter changer -<> H.P. Absorber IT,. P. Absorber --=Z^r- L =Tir=i= 15 Lb. Brine Cooler 2iF. FIG. 35. Voorhees Multiple Effect Apparatus. the lowest pressure used, it is caught in a receiver called by Voorhees, a multiple effect receiver. From the receiver some of the liquid may pass without throttling to a brine cooler, and the evaporation from this passes back into the receiver. Some of the liquid from the receiver is passed through another throttle valve and is delivered at a lower pressure to another brine cooler or refrigerating coil. The low pressure in this coil is maintained by a compressor or by an absorber of low pressure. In the case shown in the figure, the absolute pres- 108 ELEMENTS OF REFRIGERATION sure is about 15 Ibs. per square inch. The vapor formed in the receiver from the evaporation in the first cooler and from the throttling of the liquid in the first expansion valve is taken to an absorber of 37 Ibs. absolute pressure in one case, or to a cavity at the end of the stroke of the compressor, so that when the piston overrides a port at the end of the stroke, this vapor at 37 Ibs. pressure will flow in, since the pressure inside of the compressor at the end of the suction stroke is slightly less than 15 Ibs. The ammonia is now compressed and the cycle is followed out again. The card from the compressor is seen in Fig. 32. In the absorber, the low-pressure absorber receives the weak liquor from the interchanger and delivers a stronger liquor through the pump to the high-pressure absorber, and this delivers its strong liquor to the analyzer through the interchanger. The purpose of these two inventions is to utilize different ranges of temperature where possible, as the efficiency may be increased. In cutting down the range for part of the opera- tion, this part is done more efficiently and consequently the total effect is better. There are many cases in which there is some cooling at a higher temperature than another, and whenever that is so, this method can be used. Thus, to reduce the temperature of water to 40, brine at a higher temperature than that required to freeze the water could be used. If certain rooms are re- frigerated to 35 while others are at 20, this method could be employed. One of the latest applications is by the Quincy Market Cold Storage Co., of Boston, in their new looo-ton compressor, the largest ever built. This compressor draws ammonia from two systems, the cold-storage system of low pressure and the conduit system at a higher pressure. CHAPTER IV TYPES OF MACHINES AND APPARATUS THE compressor is the important part of refrigerating apparatus. Fig. 36 shows a section through the housing of a York compressor. The driving of these compressors is accom- plished by an engine or electric motor. The former is shown in Fig. 14. Fig. 36 shows a section through both cylinders. As is true in most large vertical compressors, the two com- pressors are connected to a common shaft with cranks at right angles. One steam cylinder is usually employed. This is hori- zontal and is connected to one of the two crank pins. The form of housing is clearly indicated by Figs. 14 and 36. The housings must be solid and of proper section to make a rigid construction. The box-girder columns are connected at the bottom by the casting which carries the main bearing and gives a very strong form. The working platforms for large machines are carried from the housing or frame. The fly-wheel is placed between the cylinders, being supported in a simple manner by the two bearings. The cylinders are built as shown in the figure. They are single acting and are made of close-grain metal. The suction enters at the bottom of the cylinder on the up-stroke of the piston. The piston is made long and has four piston rings to give tightness. The piston casting is carried by a spider and hub so that the ammonia may pass through the suction valve at the center of it. This valve has a central spindle to which is attached a cushion head. This is a plate. A projecting cup carried by a spider from the removable seat receives the plate. This plate and cup fit so closely that they form a dash pot and prevent the hammering of the valve and limit its motion. A spring is also used to aid in supporting the valve. 109 110 ELEMENTS OF BEFRIGERATION The gas is sucked into the upper end on the down-stroke of the piston, and when the compressor reverses, the valve is closed and the ammonia is compressed until the pressure FIG. 36. Cross-section of York Compressor. beneath the valve at the center of the head is greater than the pressure above. As will be seen, this valve is controlled by a small spring on top of it, but the dash pot into which a cylindrical projection on the back of the valve fits, pre- TYPES OF MACHINES AND APPARATUS 111 Water Overflow FIG. 36a. Sectional View of York Compressor. 112 ELEMENTS OF REFRIGERATION vents this spring from slamming the valve down on the seat. As is the case with the suction valve, the valve seat is removable. The working head of the cylinder is not bolted to the cylinder flange, but is held down by heavy springs pressing against the outer head, which is bolted fast to the cylinder. The joint between the outer head and flange is made tight by a lead gasket in a groove on which a ring projecting from the head presses. The purpose of the inner head is to eliminate the danger resulting from the small clearance used in these compressors. The piston is brought up so that it practically touches the cylinder head. Any incorrect adjustment of connecting rod, or the presence of scale would force the piston against the head and break off the cylinder were it not for this yielding safety head. The stuffing-box is long and contains, in addition to the large amount of packing, a lantern of metal through which oil can be forced on the rods. This lantern is composed of two rings connected by bars at intervals. A long bushing or gland presses against the soft packing. The cap presses this and is screwed on the box by means of a gear wheel, the shaft of which is led to a convenient point for operation. The lower part of the cylinder is a separate casting to simplify construction. The thin sheet-metal cylinder covered with wood lagging and bolted to a large flange at the lower end of the cylinder casting forms a water jacket for the removal of some of the heat of compression. It does remove some heat and so reduces the work of compression, but the amount is not large. The York Company has experimented and found that the jacket as originally made is not an element of gain, and for that reason their later jackets are placed only at the upper end of the vertical cylinder. If heat is removed at all by the jacket there should be a gain. It may have been that the lower part of the jacket warmed the incoming gas and cut down the weight taken in, but as stated above, if the jacket re- moves any heat it should be an element of economy. All parts of this cylinder and piston are easily accessible. This, together with the facts that there is no bottom wear or TYPES OF MACHINES AND APPARATUS 113 friction on the cylinder and stuffing-box, from the piston and rod, in the vertical position, and that there is no stuffing-box exposed to high pressure, has led to the selection of a vertical single- acting compressor. The stuffing-box does not require such tight packing and this reduces the friction. In a double-acting com- pressor it would be difficult to use safety heads, and so the clearance must be greater. Of course this does not increase the work of compression except for friction, but it does cut down the volumetric efficiency, requiring a slightly larger cylinder. The use of two cylinders, whether of double or of single action, is advantageous in that if one must be disconnected for repair, the other may be operated alone and the plant kept in operation. FIG. 37. Indicator Card from Compressor with Guide Lines. Fig. 37 shows an indicator card taken from such a com- pressor. If the clearance line, absolute zero line, suction-pressure line and discharge-pressure line are drawn on this card and then the adiabatic is constructed as shown by the method below, certain information may be had in regard to the operation of the compressor in addition to the knowledge of the power taken. The horse-power is worked out in the usual manner. If the suction-pressure line is much above the back-pressure line, there is excessive valve friction due to the spring being too tight or the valve sticking. If the discharge pressure is much below the upper pressure of the card, the same may be said of the discharge valve. If the adiabatic falls below the compres- sion line, there must be a leaky discharge valve, while a com- pression line below the adiabatic would mean a leaky suction 114 ELEMENTS OF REFRIGERATION \ valve or piston. The jacket does remove heat and causes the compression line to fall below the adiabatic line in theory, but this amount is so small that it can hardly be noticed on the card. Hence, when there is a decided drop below the adiabatic, which is what is desired in theory, one must look for a leaky piston or suction valve, as the ordinary jacket could not pro- duce the result. The construction of the adiabatic is one which would have to be made by use of an equation of the form pv n = const. . ...... (i) If the compression is dry, the adiabatic is of the form # 1 - 33 = const. ....... (2) For wet compression the value of n must be computed for any given condition. The conditions at the ends of com- pression must be known. The quality x at one end is related to that at the other by the equation / , OC\r\ f X2T2 f N Si+^r~=S2+-^- ....... (3) 1 1 2, s' = entropy of the liquid ; Tp: = entropy of vaporization; x = quality. In this x\ may be found from X2 since the two pressures are known, or as is usually the case, X2 is made unity and then f x (4) Having x\ and X2 the volumes per pound may be found by VI = XIV"L . '. . . . . . (5) V2 = X 2 V"2. ..,.,. (6) TYPES OF MACHINES AND APPARATUS v =vol. of i Ib. of mixture; o" = vol. of i Ib. of dry vapor. Then n is given by log^- 2 115 log (7) After the n for wet compression is found, the equation is known. Having the values of n, the volume vi from the zero volume line and the pressure pi from the zero pressure line are measured in inches and then by assuming other volumes the pressures at those points may be found by n log v x These are tabulated for ^ = 1.33 for the card. (8) Point i a b c Volume in inches 2.16 i .20 0.80 O.7O Pressure in inches o 24 o ^3 O.QO I . !? The motor driving the compressor may be one of various types. For large compressors efficient Corliss engines are used for refrigeration, although for ice-making where distilled water is needed, less efficient engines are used. Gas engines are used at times and electric motors are of great value for small plants in hotels, hospitals, stores and residences. One of the early successful ammonia compressors, used in the days of the introduction of mechanical refrigeration, which has remained one of the leading compressors, is that built by the de La Vergne Machine Company. The cylinder of their vertical type is shown in Fig. 38. This is their vertical double- acting compressor. The head of the cylinder contains several 116 ELEMENTS OF REFRIGERATION FIG. 38. De La Vergne Vertical Double-acting Cylinder. TYPES OF MACHINES AND APPARATUS 117 delivery valves placed in a casing. The suction valves are placed in casings inserted in the sides of the cylinder. Each valve is held to the seat by means of a spring and is arranged to be guided by a long sleeve around a central spindle. This forms a dash-pot action and prevents slamming. The suction valves are in cages forced into radial recesses in the cylinder. By removing the cover of the recess, the valves and their seats may be removed for examination or repair since the valve cages include valves, seats, springs, and dash pots. The head discharge valves are placed in a casing or housing. This is held against a projecting part of the cylinder casting making a gas- tight joint by the head pressure in addition to the pressure from a set screw attached to the main head of the cylinder. This set screw has a jamb nut on it and to care for the ammonia leakage around the threads, a cap is fastened over the top. This cap and the main cylinder head are made gas tight by lead-ring gaskets in a groove into which a projecting ring fits. These rings and the method of holding the head are made clear in the picture. The set screw holding down the valve housing is in reality a safety device, for should scale or other obstruction fall on top of the piston the bolt would break when the obstruc- tion was brought up against the valve housing at the top of the stroke. The lower discharge valves are attached to housings at the bottom of the cylinder. The stuffing-box gland is shown in the figure and owing to the peculiar use of oil in this cylinder there is no provision for introducing oil into the gland. A peculiar feature of this compressor and that of the de La Vergne Company is the introduction of a spray of light paraffine oil on each stroke. After spraying this oil forms a thin layer over the top of the piston on the down-stroke and one on the lower cylinder head on the up-stroke. In this way the piston and piston rod are sealed with oil, thus cutting down the tendency to leak. This oil also fills up the clearance space at the top end of the stroke. The excess oil is driven out through the valves. This of course reduces the clearance to zero. At the lower end of the stroke the oil would not flow away readily, so valves are introduced into the piston allowing oil to enter the hollow part 118 ELEMENTS OF REFRIGERATION TYPES OF MACHINES AND APPARATUS 119 of the piston. From this space the oil discharges through the upper discharge valve, when it is connected with this space at the lower end of the stroke by an opening in the side of the piston. In this way the oil is carried out without the danger of breaking the compressor. This injection of liquid also absorbs some of the heat of compression and makes the work less. The piston is fairly deep considering the fact that the oil seal cuts down the amount of leakage. This also reduces the friction. The piston rod is held to the piston by a circular nut and projecting collar. The construction with two parts is clearly shown. The false cap held on the cylinder head by the tap bolt is for finish only. The suction and discharge pipes are attached by means of flange unions. The use of oil requires additional apparatus to recover the oil from the discharge. The heated gas is first passed through the fore cooler, Fig. 39, and after being cooled it is taken to the pressure tank, where the oil separates out and the remaining gas goes to the condenser. The oil taken out goes back through the strainer to the engine; other oil which enters the condenser is finally separated from the liquid ammonia in the separating tank. The oil here separates and passes over to the com- pressor, being sucked in on the proper stroke. Fresh oil may be added to the system by the oil pump when needed. The liquid ammonia is taken from the storage and separating tanks by the main liquid line to the various expansion coils in rooms or brine tank. The suction is brought back to the main suction pipe of the compressor. Fig. 40 illustrates a horizontal type of compressor brought out by this company. The suction valve A opens into the passage B, which is connected to the cylinder C. The suction valve with its seat, spring and dash pot are in a housing which is held in place by a bonnet or cover-plate. The discharge valve D is in a similar housing. Either of the valves may be examined by simply removing the head. The housings are t 1 TYPES OF MACHINES AND APPARATUS 121 arranged with slots so that gas from the suction main E enters the space F and goes through the valve from this into the cylinder. In the same way the discharge from the valve D passes through G into the discharge main H. In this cylinder there is no chance for the valves falling into the cylinder and any scale or obstruction would tend to fall into the space at the lowest point of the cylinder barrel. The piston and its attachment' to the rod are clearly shown. The double-lanterned stuffing-box is shown. This is due to the fact that there is no oil lying around the rod as in the former case. The lubrica- ting oil enters at I and is taken out at /. At K in certain cases, a connection is made to the suction pipe to remove any ammonia which has leaked past the first set of packing rings. The cylinder is surrounded by the jacket M . The cylinder of a horizontal double-acting compressor of the Frick Co. is shown in Fig. 41. This company builds ver- tical compressors which are very similar in general features to the compressor of the York Manufacturing Co., so that no section of that type will be shown. The cylinder is provided with valves in the spherical heads arranged in radial lines. They are arranged in this manner to increase the valve area for a given diameter of cylinder while using a small amount of clear- ance. There are usually two suction valves and two discharge valves on each end. The two upper valve boxes are con- nected, as are the two lower discharge boxes. As shown in the figure, these valves are so arranged that the seats, springs and valves may be removed with the valve housings by simply removing the bonnets. The long stuffing-box, the wide piston, the packing ring for the lead gasket in the heads and bonnets, the water jacket and the other peculiar features of ammonia compressors are clearly seen. The piston rod is properly attached by a nut. Some builders attach the rod by peening over the end after forcing the rod on the piston. This is not good practice and should not be resorted to unless ab- solutely necessary. It is better to use some form of nut or cotter pin. The piston is made in two parts, making a simple core arrangement in casting. To stiffen the cylinder, long E TYPES OF MACHINES AND APPARATUS 123 through bolts are passed from one end to the other, thus relieving the cylinder of strain. The stuffing-box is provided for an oil- supply attachment, and an ammonia pipe returns to the suction pipe gases which leak out; these features are shown by dotted circles at the center of the rods. For the proper operation of compressors it is necessary at times to remove the vapor from the cylinder. To do this there FIG. 42. Frick Manipulating Valves for Small Compressors. are certain by-pass arrangements common to most compressors. The arrangements used by the Frick Company are shown in Figs. 42 and 43. To exhaust the vapor from one compressor the machine is shut down and all of the valves are closed. The purge valve 10 is opened. This permits gas to escape. The machine is now operated slowly. The cylinder head of L may be removed. To exhaust R, the same method is used. To exhaust the condenser and store the ammonia in the expansion coils, close all valves after shutting down, then open 124 ELEMENTS OF REFRIGERATION the valves i, 2, 3, 4 and 12 and start the machine slowly. The gas for compressors is sucked through valves i, 12 and 2 from the discharge main, while after compression it is discharged through 3 and 4 into the suction piping. To admit air into the high side for testing, close the suction valves 5 and 6, and leave the discharge valves 7 and 8 open. Open valves i and 2, removing the plug from tee n. Valves 3, 4 and 12 are closed. Air. is then drawn in by i and 2, when the compressor is driven slowly. To admit air for testing low side, the suction valves 5 and 6 and the discharge valves 7 and 8 are closed. Valves i, 2, 3, 4 U 5 FIG. 43. Frick Manipulating Valves for Large Compressors. are opened and the plug in tee n is removed. T Air will enter i and 2 when the compressor is run slowly and the discharge is passed into the suction main by 3 and 4. Before air is introduced on either side the ammonia is ex- hausted from that side by pumping the ammonia into the other until a low vacuum exists on the side from which the vapor is being pumped. For larger compressors a different arrangement of pipes is used, as shown in Fig. 43. In this case, valves i and 2 are attached to valves 5 and 6 and then valves 9 and 10 are added to the pipes running from 4 to i and from 3 to 2, while valve 1 1 connects to the suction pipe. TYPES OF MACHINES AND APPARATUS 125 To exhaust the compressor R, all valves are closed after shutting down the compressor. Then stop valve 8 is opened with 2 and 3. The valve 10 when closed prevents any con- nection to the suction at that point. If the compressor is started slowly, the compressor L draws from R and frees it of ammonia. Valve 2 opens inside of 6. To exhaust the condenser the valves opened are 8, i, 4, 3, 10 and ii. In this case the gas is sucked from the discharge pipe through 8, 4, and i into R and then the compressor vapor passes over through 3, 10 and n into the suction mains. The FIG. 44. Section of Arctic Horizontal Double Single-acting Compressor. other compressor could have been used. To empty the suction the compressor is operated in the usual way with the reducing pressure valve closed. One recent improvement in the arrangement of compressors is that of the Arctic Machine Co. in their center inlet horizontal double-acting compressor shown in Figs. 44 and 45. In this compressor the inlet valves in the piston are similar to the hurricane inlet valves of the Ingersoll-Rand air compressors. To avoid the piston-rod inlet connection, the two piston faces are separated a distance equal to the stroke of the compressor and the center of the piston barrel is cast with openings leading 126 ELEMENTS OF REFRIGERATION from a ring passage into the cylinder bore. The suction vapor enters this passage and the space between the two piston faces. There are a series of openings extending through the piston face near the periphery and these are -covered by a ring of metal. When the piston starts from one end, a vacuum forms behind the piston, and the gas between the piston faces, being at a higher pressure, forces the ring out against a stop and enters behind the piston with little change in pressure. At the other end of the stroke, the acceleration of the recipro- cating parts when the piston begins the return stroke closes this valve and the piston begins to compress. In this way falve Open Valve Closed FIG. 45. Suction Valves and Pistons of Arctic Compressor. the compressor acts rapidly on the suction stroke with little drop in pressure. The discharge valves and housing are connected to the lowest part of the cylinder at each end, thus caring for scale and liquid. These valves may be examined by removing the bonnet. The springs and dash pot are seen in the figure. The cold ammonia coming to the center does not affect the stuffing-boxes and the jackets are removed from the cold parts of the cylinder. An insulating filling is placed at the center to cut down radiation. The heads are jacketed as well as the barrel ends. The path of the water is seen. The stuffing-box is shown with its oil connections. There is also a connection leading from the stuffing-box to the suction main. The piston detail is shown in Fig. 45. The valve disc is TYPES OF MACHINES AND APPARATUS 127 the ring A , the motion of which is limited by the guard ring or projection B. The openings C are distributed around the periphery of the piston. The method of attaching the piston is proper in this case as the load is taken by a shoulder. Each of the piston faces is in reality a single-acting compressor. The action of the suction valve is so free that, according to reports on the compressor, the suction drop was only i Ib. at 300 R.P.M. The valves of the compressor of the Triumph Ice Machine FIG. 46. Valves of the Triumph Ice Machine Co. Compressor. Co. are shown in Fig. 46. These valves and their seats are held in a housing or cage which is held in place by a nut screwed into the valve cavity and containing set screws to hold the cage tight against the head casting. The suction valve spindle is held up by two springs each with a separate adjusting collar. These collars may be held tight by jamb nuts or set screws. The small collar at the lower end of the suction spindle acts as a dash pot. In the discharge valve there are two springs holding the valve down and a cup acting on a shoulder or collar on the 128 ELEMENTS OF REFRIGERATION TYPES OF MACHINES AND APPARATUS 129 spindle serves as a piston and dash pot. In each case the long spindle guide keeps the valves in line. The cylinder of a carbonic acid machine will be shown because of the special features due to the high pressures carried. One of the best known compressors of this type is that of Kroeschell & Co. and is shown in Fig. 47. The cylinder is a rectangular steel forging in which the ports are drilled from one end. The various valves are placed in housings which are held in place by bonnets. These valves are operated by springs as shown. The suction valves have helical springs while a cap on the top of the spindle limits its movement. The discharge valves have a spring to support them and a flat spiral spring to force them back. The seats are held in by bonnets or cages and may be removed readily. The bonnets are made tight by fiber washers. The piston is packed with cup leathers to sustain the high pressure. One end is flat because of the head and the other end is spherical in order to place the two suction valves and one discharge valve. The piston rod is packed with a series of cup leathers with provision for circulating oil. The two suction passages are connected around the head valve, the suction pipe entering one of the passages at the center as shown. The discharge passage is connected to the top face of the cylinder. Each of these is controlled by a valve. The valves, Fig. 47, have drips or scale chambers at the bottom to catch dirt. The discharge passage is connected to an open- ing covered by a thin plate which will break when excessive pressure is brought on the discharge by shutting off the discharge stop valve or by a stoppage of the system. A relief valve is also fixed on the suction side to relieve excess pressure. The parts of this compressor are made of steel, due to the heavy pressures. The remaining part of the compressor is similar to any other type. Fig. 48 shows one of the Kroeschell marine compressors in which the double-pipe brine cooler and double-pipe condenser 130 ELEMENTS OF REFRIGERATION TYPES OF MACHINES AND APPARATUS . 131 are placed in the base of steel. The steam engine driving this is seen at one side of the compressor. One of the latest types of machines in which the compressor, condenser, brine cooler, and pipe system are contained within the same casing is shown in Figs. 49 and 50. This is the Audiffren-Singrun Refrigerating Machine., as sold by the H. W. Johns-Manville Co. In the spherical case A is a hollow shaft B, supporting as an axis a casting V which is so heavily weighted by W that it will not turn. This casting carries the trunnions TT of a cylinder C, the piston of which is connected to a rod attached to the strap of an eccentric sleeve D on the shaft. If the whole casing is turned and with it the shaft, the heavy weight remains down and the piston in the cylinder is drawn in and out by the eccentric while the cylinder oscillates. Thus oscillation of the cylinder between the faces of the suspended casting causes the face of the cylinder casting to oscillate over the face of the right-hand casting which contains holes. In this way the ports of the two ends of the cylinder are connected to suction ports N in the hanging casting at the proper time in the same way as the distribution of steam is accomplished in the oscillating engine. In this way 862 vapor is admitted to th e cylinder from the annular space E between the two shafts and the space F when the holes at G in the cylinder and face come oppo- site. The vapor is compressed in the cylinder and when the proper pressure is reached the discharge valves at H open and dis- charge the vapor into the casing A . The casing revolves in a tank 7, Fig. 50, containing the cooling water. This condenses the sulphur dioxide and the liquid collects at the outer part of the casing A , and is caught up by a scoop M, and is conducted to the reservoir /. It is then delivered to a regulating float throttle valve after the lubricating oil is removed from the 862. The oil flows over at U into the chamber O in which the cylinder is placed. Thus the eccentric and cylinder are flooded with oil. This whole region is under pressure, so that there is no leakage from the compressor. There is a tendency for the oil to enter around the piston rod and between the valve faces- The spring X holds the system against the sliding face. The 132 ELEMENTS OF REFRIGERATION i TYPES OF MACHINES AND APPARATUS 133 liquid S02 at low pressure after passing the throttle valve travels along the inner pipe extending between the two vessels and finally settles to the circumference of the other spherical vessel, due to centrifugal force, and it is evaporated as it removes heat from the brine in the tank R, Fig. 50. The vapor is returned through a space formed between the two pipes between A and (/, and passes into the SCb compressor. The complete system is con- tained within a tight set of vessels and pipes, and there are no moving joints to be kept tight. There is no danger of leakage. An extension on the right-hand vessel serves as one journal for the system and the intermediate pipe serves FIG. 50. Audiffren Singrun Apparatus. as the other. There is little weight on the journals, as the buoyancy from the immersed vessels supports much of the weight. The gas pressure in A tends to hold the oscillating piston against its face in addition to the spring pressure, and keeps the sliding joint tight. Should the condensing water be shut off and the temperature rise, the high pressure developed Vould finally be sufficient to cause the weight to rotate and so prevent a further rise in pressure. The small valve at 5 is held down, when the apparatus is in opera- tion, by centrifugal force, but upon stopping the machine this valve is opened by the weight of the balls, thus equalizing the pressure. The following table gives the data for these machines: 134 ELEMENTS OF REFEIGERATION Capacity in Tons. Size of Machine. Power Required. R.P.M. Refrigeration. Ice. 2 O.IQ 0.13 0.4 to 0.6 H.P. 380 3 0.48 o ; 32 i to i . 5 280 4 o.q6 i 0.66 2 tO 2.25 190 6 I.Q2 1.32 4 to 4 . 50 140 The great advantage of such a machine lies in the fact that there is no manipulation of valves, stuffing-boxes, gauges or oiling devices. In Fig. 50 the general arrangement of this apparatus is seen. The cooling water in 7 liquefies the SO2, while the evaporation of the SC>2 cools the brine in the tank R. If this brine is cooled completely there will be no evaporation of S02, and there will be no gas sent back to the compressor, and consequently none will be liquefied in the case in A . Hence, after a short time the level of the liquid in / will be such that the float valve K will be closed off and no more liquid 862 can pass over to R. The motor is attached to the pulley Z. The above gives the necessary details of the compression machines. The parts of the absorption machine will now be considered. Generators. In Fig. 19 a cross-section through a generator is shown. This is seen to be made of a circular tank with flanged ends and dished heads, containing several coils of steam pipes connected to manifolds. This is of cast iron, and bolted to a T-connection is the analyzer, containing a series of trays over which the liquor from the exchanger and rectifier flows. The pipes are so arranged that the gases have to pass through the liquid. The cast head, dished to give strength, is shown. In Fig. 51, the generator of the Henry Vogt Company is shown. In this strong liquor flows into the top section of the generator from the exchanger. The excess liquor flows from this at the left-hand end to the next section, and the excess from this might flow into a lower section if used. In this way the liquor travels the whole length of the section before leaving it. TYPES OF MACHINES AND APPARATUS 135 The weak liquor is taken off at the right-hand end of the lower section. The connections are made to give a definite liquid level in each section. The vapor formed in each section is taken up through a main pipe to the rectifier. The steam coils are connected to manifolds which are connected together FIG. 51. Vogt Double Cylinder Generator. FIG. 52. Vogt Modern Generator. on the steam side and at "the discharger end. The cylinders and heads are made of cast iron and the supports are made to carry these from the lower sections. The analyzer is arranged at times to cause the vapors to travel up through the strong liquor which flows over per- forated plates. The gas is then carried to the rectifier. Fig. 52 is a section of one of the later forms of Vogt gen- 136 ELEMENTS OF REFRIGERATION erator. The generator is made of semi steel pipe with dished heads using a tongue and groove packing. The strong liquor pipe passes through a stuffing box and is attached to the analyzer header A. From this point the liquor is carried into a number of tubes forming the analyzer in this case. These are in the space through which the heated gases pass on the way to the outlet and dry pipe B. The weak liquor is taken from C and at DD the glass gauge gives the level of the liquor. The evaporation occurs at the surface of the closed steam pipes, E, which are screwed into the head. The manifold cap has a series of small tubes, G, Liquor Vapor FIG. 53. Vogt Rectifier. attached to it, and taking steam from F to the ends of the closed tubes. Then the condensed steam is removed at the lower part of the head. This construction is quite simple and effective. Rectifier. The rectifier is made in several ways. In some cases, as in Fig. 19, it consists of a coil of pipe made up of return bends, through which the vapors flow to the separator and con- denser while cooling water is passed over it. In other cases it is formed as a double-pipe condenser, the construction of which will be explained later. When this double-pipe apparatus is used, Vogt uses the strong liquor as cooling substance, passing it directly to the rectifier before it enters the exchanger. TYPES OF MACHINES AND APPARATUS 137 Exchanger. The exchangers are of various forms. In Fig. 19 the form is a cast-iron cylinder with a coil within. This coil carries the weak liquor and while the strong liquor passes around this coil as it goes through the shell. The York Com- pany and Vogt use a double pipe construction for this apparatus. Weak Liquor Cooler. This is of double-pipe construction. Absorber. The absorber is made in several forms. In all of them vapor enters at bottom and is distributed through a per- forated pipe. The weak liquor is distributed near the top of the absorber, the flow of weak liquor being controlled by a Weak LiquidJnlet FIG. 54. Vogt Absorber. float shown in Fig. 55. This float is attached to the side of the a sorber. The action of the float is to control the admission of weak liquor by the valve A. The strong liquor is pumped from the bottom of the vessel, which is usually made cylindrical. In the absorber there are sets of tubes carrying cold water to remove the heat of absorption. Fig. 19 gives the construction used by the Carbondale Co., while Fig. 54 is the absorber of Henry Vogt & Co. The drawing shows the construction and the manner in which there are four passes of the water. The other parts of the apparatus being used with this and compression machines will now be described. 138 ELEMENTS OF REFRIGERATION Piping. The piping for ammonia should be full weight or extra heavy wrought-iron pipe. The pipe is united with FIG. 55. Vogt Regulator for Weak Liquor Inlet. screwed fittings, flanged fittings and by welding. For use with CO2 extra heavy pipe must be used. This is determined by the pressure to be carried and the opinion of the engineer. TYPES OF MACHINES AND APPARATUS 139' Ammonia pressures will run as high as 200 Ibs. per sq.in., while carbon dioxide may be 1000 to 1200 Ibs. The best method of uniting these pipes is by welding, as there is no chance for leakage, although they cannot be dismantled easily. Weld- ing is done by the use of thermit, the oxy-acetylene torch or by electricity. In this work the parts are clamped together tightly and thermit is ignited in a crucible, after which the aluminum oxide and the hot iron are poured into a mold around the pipe and produce a welding temperature. Thermit is a mixture of Fe20a and 2A1. It burns to 2Fe and A^Oa, producing a tem- perature so high that the molten iron and slag can heat the pipe to a proper point for welding. The thermit powder is held FIG. 56. Thermit Pipe Welding. in a crucible and after ignition is complete it is poured into the mold around the part to be welded. Before welding the pipe ends are milled smooth by a special facing machine and are then clamped and held tightly together. An iron mold is then put around the pipe and the thermit poured in as shown in Fig. 56. When the operator feels the clamp, Fig. 57, yield he knows that the iron has reached a weld- ing heat, and by pulling the clamps together and giving four quarter turns of the bolt the weld is made. After the weld is made the mold should be left ten or fifteen minutes if possible, and then removed. The iron and slag will fall away. Thermit is placed in bags with the proper amount for a given size pipe. In igniting it, it is customary to use about one-half of the package at first and then, after igniting it by means of an ignition powder and Hatch, the remainder of the package is poured in. The 140 ELEMENTS OF REFRIGERATION slag first forms a coating around the pipe, protecting it from the molten iron. The heat is used only to bring the iron to a welding temperature. Tests of pipes welded in this manner have shown that the weld is as good as the pipe in tension, torsion and bending tests. The cost of thermit welding amounts to 75% of the cost of elbows or flanged joints for small sizes, while for four-inch flanged joints the thermit cost is greater than the cost of fittings. The use of the oxy-acetylene torch is valuable in cutting as well as in welding. C2H2 is mixed with Cb in the nozzle, and if just enough oxygen is introduced, the flame will consist of CO2 and H2O. The heat is produced by the breaking down of the C2H2 and by the formation of CCb and H 2 0. An ( FIG. 57. Thermit Welding Clamp and Mold. intense flame temperature is obtained. When welding is de- sired the mixture is as given above, and by pressing the parts together and melting a stick of steel by the flame to flow into the interstices a fixed weld is made. If it is desired to cut the metal, a correct burning mixture is used on the outer part of the flame and after this heats the metal, a flame rich in oxygen is thrown out from the center of the nozzle and burns a groove through the metal. This torch is particularly valuable for welding plate, work. The temperature is so high that the H 2 O is dissociated and the hydrogen burns on the outside of the flame. In electric welding; an alternating current of low voltage but great current strength is delivered from a transformer through large leads clamped to the pipes to be welded. The TYPES OF MACHINES AND APPARATUS 141 142 ELEMENTS OF REFRIGERATION resistance at the butted ends to be welded soon causes these to become white hot and the metal is welded. The fittings on pipes are usually screwed on. The taper thread is~carefully cut and the joint made tight by a mixture of litharge and glycerine. This forms a cement and makes a good joint if the fittings are made tight. At times, with black iron, the threads are tinned over, when the solder makes a joint if they are screwed together when hot. This method should not be used with galvanized pipe. There are claims for each method. The flanged unions, Fig. 58, are used for uniting sections FIG. 59. Boyle Union. which may have to be separated. They are screwed to the pipe as shown in the figure or sometimes the type shown at C is used. B shows the flange joint of the de La Vergne Co. It has a cavity left at the upper end of the screwed portion of the flange into which solder may be left as it is forced out from the tinned threads when the flange and pipe are heated and forced together. This fills the space and threads at one end with solder so as to make a solid gas-tight joint. The flanges are made of a close-grained malleable iron combining strength and toughness, or else drop forgings or steel castings are employed. The joint between the two flanges is made tight by a lead gasket which fits in a groove in one flange and is pressed down TYPES OF MACHINES AND APPARATUS 143 by a projecting ring on the other flange. At times lead gaskets are placed between flanges as shown in A and C. Fig. 59 FIG. 60. Elbows. illustrates a Boyle union used in refrigerating work. In this a change of alignment is possible by properly finishing the ends of the nipple. Where elbows are needed they may be screwed as shown in Fig. 60 B, and sometimes it may be necessary to use a flanged elbow, the flange being on one outlet as in the figure. Very often both ends of the elbow have flanges. A tee, Fig. 6 1, is used when it is desired to take off a side branch. Return bends are made as shown : ! f-J FIG. 6 1. Tee. 144 ELEMENTS OF REFRIGERATION TYPES OF MACHINES AND APPARATUS 145 in Fig. 62. These tees and bends show different arrangements used in ammonia work. Thus one bend B has an extra flanged outlet on it. It is a special return bend used on the de La Vergne condensers to carry off condensed ammonia. If it is desired to connect two sections of a coil, two flange fittings FIG. 63. Flanged Return Bend. W1WPF FIG. 64. Branch Tee or Manifold. known as return bend flanges are employed. This is shown in Fig. 63. Manifolds, or headers, for the connections of a number of branches, are made by welding. They may take a number of special forms, depending on the peculiarity of design. Fig. 64 illustrates one with fifteen branches for the connection of the 146 ELEMENTS OF REFRIGERATION different coils of a condenser. A cross, Fig. 65, is used at times when two lines are to intersect or three branches are to be taken from a line. All of the fittings are extra heavy to allow for the high pressures, and after erection the whole system is filled with air under pressure. After closing the valves of the compressor the system should hold its pressure for hours. Leaks may be found by coating over the pipes and fittings with soapy water. In the shop welded joints are tested by immersing the apparatus in a tank of water after charging it with air under pressure. Since the compression heats the air and the oil vapor from A \ s: FIG. 65. Cross. the pipe work might form an explosive mixture which would ignite at the temperature due to compression, Block advises stopping the compressor for a while after reaching 50, 100, 150, 200, and 250 Ibs., giving the air some time to cool. The pipe hangers for this work must be strong and well supported, as many pipes are filled with brine and loaded on the outside with ice and snow. The weight of these must be added to the weight of pipe in figuring the strength of the hangers. Fig. 66 illustrates several methods of supporting the pipe. The valves used as stop valves on the vapor line are of various forms with strong flanges and stuffing-boxes. Usually the seat has a soft lead ring for giving a tight joint, and the stuffing-box is long. The bonnet of the valve is bolted on the main body, TYPES OF MACHINES AND APPARATUS 147 o I 148 ELEMENTS OF REFRIGERATION f TYPES OF MACHINES AND APPARATUS 149 using a lead gasket. Two valves are shown in Fig. 67 and each of them is provided with flange connections. For angle con- nections, valves are built in this form, using an angle body. Where liquid ammonia or vapor is to be prevented from return- ing, check valves are used. These are made as shown in Fig. 68, of a lift type known as the cup pattern, due to the guide cylinder on the back, or they may be of the swing pattern. The massive construction is shown here. For expansion valves a small opening which may easily be adjusted for small changes is used. This means a needle valve and hence the forms shown in Fig. 69 are employed. In each of these the needle valve is rrn FIG. 68. Check Valve. raised by a fine-pitch thread so as to give close regulation on the amount of liquid discharged. Safety stop valves are built for the discharge valves of compressors. These valves are pro- vided with a spring-closed by-pass valve which only opens when the pressure reaches a high value. Condensers. The ammonia condensers are of various forms, depending on the plant, its location and size. An open-air surface condenser should be used when the cooling water carries scale-forming salts which would be deposited at 100 F. This condenser may be of several forms. If welded into a continuous coil there would be a difficulty in renewing a part of it. Fig. 70 shows the welded form of Kroeschell & Co. for C02- Welded coils are rarely used as condensers. This form is very often 150 ELEMENTS OF REFRIGERATION used as an expansion coil. In Fig. 71, a condenser fitted with flange joints between the return bends and pipes is shown, while in Fig. 72 screwed joints are used. In Fig. 71 the I X o hot ammonia vapor passes through two lower pipes and then is taken to the top pipe in contact with the coolest water. This water is distributed from the perforated or split pipe at the top of the rack of tubes. In this arrangement there TYPES OF MACHINES AND APPARATUS 151 152 ELEMENTS OF REFRIGERATION is a slight counter-current effect, but the main condenser is of parallel flow. In Fig. 72 the same general arrangement has been used with a change. After the liquid is formed in the condenser, it is passed through a small pipe contained in a larger pipe, and through the annular space formed between the two pipes the coldest condensing water is passed on its way to the sprinkling pipe. In this way the liquid is cooled to almost the lowest temperature of the cooling water. The condenser shown in Fig. 73 is one in which vapor enters at A , which is cooled by Purge Valve ft Water Enters TT -> Saturated Vapor FIG. 71. Ammonia Condenser with Flange Joints. the warmest liquid, and any condensation which occurs is taken off at B, C and D, and is passed to the storage tank. Other liquid is taken off at E. The cooling water enters at F and flows over the slot in the top of the distributing pipe and falls over the pipes. At times plates are placed between successive pipes so that water will follow from pipe to plate to pipe and will not be blown off by a light wind. Flanged joints between elbows forming together a return bend permit an easy method of con- struction. The drips at certain return bends are cast in the bend. The connections between the pipes and fittings are screwed joints. TYPES OF MACHINES AND APPARATUS 153 154 ELEMENTS OF REFRIGERATION Of course, all of these condensers, known as atmospheric condensers, have the water sprinkled over the surface so that when the wind blows the water may be blown away from the pipe surface and the condensers are therefore placed in shallow tanks so that the water may be caught. It is quite customary to shield them from the direct action of the wind by the use of n t .11 h r 1 II gflpj t / x ilLJIi I c II II ; \ \ II II ZJ ) / / (c II II _ \ v .11 II J=D > / / ( C II II i J V Sw .11 II ID ) Q (*""" r II II S-fc . v ' II ii j=> ) / y (< .11 11 \ \ .11 ^^L c r || T n 4= frH .11 /~ (( .11 1 II \ \ .11 1 : E>) B r II | || - U II r ( II ! II n FIG. 73. Sectional Diagram of De La Vergne Condenser. slatted blinds. By inclining these properly the water striking them will be sent back to the tank. The condensers utilize the cooling action of cool air blowing against them and hence in cold weather the supply of water is decreased. In small plants or in places where there would be trouble from the falling water, a submerged condenser, Fig. 74, is used. In this the vapor is admitted at the top and flows downward. Cooling water enters at the bottom of the tank and flows to the TYPES OF MACHINES AND APPARATUS 155 sewer from the top. A drain placed at the bottom will remove all water when necessary to break off the scale. This is of the counter-flow type. One of the best forms of condenser in which the use of free- TV'ater lulet ^ i o ( o 1 o i 0- (( < O H 1 cd> * J " ^ "U 1 ^ 3 ^ |- ra ^- iua I "^ 1 I * ] > 1 (0) I c 0) t o (O) t 0) ~\ o t -J" 3 1 l E=3 r-t > wwi ^ C (L Liqi H LJE i > -jj jid Out s* i s let 1 1 ati Drain FIG. 74. Frick Submerged Ammonia Condenser. falling water is inadvisable and also where there is little danger of scale forming, is the double-pipe condenser, Fig. 75. In this one pipe is placed inside of another one, heavy fittings being used to connect the ends so that cooling water may be passed through the inner pipe while ammonia is condensed in the annular space between the two pipes, thus using the air as a 156 ELEMENTS OF REFRIGERATION heat-absorbing medium as well as the water. The ammonia vapor enters at the top at A. The inner pipe passes through this special casting having a lead packing-ring stuffing-box. From the end B the warmest cooling water leaves. The am- monia passes through the annular space between the two pipes. At the end C, the water pipes are connected by the return bend, while the special casting supporting the two successive sets of pipes are connected and the ammonia passes to the next level and at the other end this run is connected to the next lower. The ammonia and water pipes are connected in this way until D is reached, from which the liquid ammonia Water Water FIG, 75, Frick Double Pipe Condenser. passes out. The cold water enters at E. The special return- bend castings are arranged so that the water pipe is held in place by a stuffing-box and by means of a properly packed joint a projection of one box fits into a groove of a lower one and thus connects the ammonia channel of two successive lines. The bends are held together by bolts. By using the flanges on the outside pipe and the special casting F, any pipe can be removed with little work. In this double-pipe condenser the velocity of water may be increased to a high value, thus increasing the value of the coefficient of heat transfer K. This is one of the important features of the double -pipe condenser. Its main use has been, TYPES OF MACHINES AND APPARATUS 157 however, to remove the free water from the installation which results in dampness. This is also advisable when the water is to be used for other purposes, because the water, which is under pressure, may be delivered to any point after warning. Fig. 76 shows the method of forming double-pipe condensers, as recently suggested by the Philadelphia Pipe-Bending Co. In Ammonia FIG. 76. Philadelphia Pipe Bending Co. Double Pipe Condenser. these condensers a tight joint is made by packing being forced against the pipe by pressure. The latest improvement in condensers is to have a liquid coating on the ammonia side of the pipe, as it has been the experience of those familiar with this apparatus that if the pipes are covered with liquid ammonia they will transmit more heat per degree difference per hour per square foot than they will if not wetted. The York Manufacturing Company obtains this wet condition by injecting a certain amount of condensed liquid from the condenser back with the compressed vapor on its way to the condenser, using an injector nozzle to take up the liquid 158 ELEMENTS OF REFRIGERATION and introduce it into the condenser with the vapor. Block accomplishes the same thing by casting a ridge in the return bends of his condenser, forming a dam which retains a certain amount of liquid in each pipe. In this way increased duty from a given amount of surface is made possible by the presence Block Type - ^ Shipley Type FIG. 77. Block and Shipley Condensers. of liquid inside. This liquid is carried along by the vapor flow. The condenser pipes are supported by vertical pipe supports shown in Fig. 78. The pipes are either held between the sup- ports or on brackets projecting from the side. Bolts are used as the supporting element in the right-hand type, while in the TYPES OF MACHINES AND APPARATUS 159 middle form the pipes are held by the castings when they are held together by bolts. Separators. The separators used in the ammonia systems for scale or oil separation should be of the same form as those used in engine work, but with heavy walls and flanges and a strong gasket packing. Fig. 79 illustrates the Triumph Ice Machine Co. oil separator. The incoming vapor and oil are i I ' FIG. 78. Condenser Pipe Supports. discharged by means of a cone against the side walls of the separator and the oil will cling to the wall while the vapor rises slowly through the large cross-section of the cylinder and passes a strainer A and leaves at the outlet B. The oil and water may be drawn off at the drain valve. Liquid Receiver. Liquid receivers are usually made of pieces of extra heavy wrought-iron pipe with flanged heads welded in. They are strong and durable. These are usually tested to 500 Ibs. air pressure. The outlet from these is con- 160 ELEMENTS OF REFRIGERATION aected to the bottom, the inlet being at the top. In some cases the discharge from the condenser enters at the outlet pipe, and if there is more liquid coming from the condenser than that required by the expander, the liquid can collect/ since the two valves are connected by an equalizing pipe. I From jCompresaor To Condenser FIG. 79. Triumph Oil Separator. Brine Cooler. The brine cooler is an apparatus in which heat is abstracted from the brine by the evaporation of the ammonia. Usually the liquid ammonia is admitted at the bottom of a coil of pipe and the vapor resulting from the evap- oration is taken off from the top. Around this coil the brine is circulated, or in some cases the brine is in the coil while the ammonia is on the outside. In Fig. 19, the brine cooler is TYPES OF MACHINES AND APPARATUS 161 equipped with a brine coil, the liquid ammonia being carried about one-third of the height of the chamber of the cooler. It is always well to have the liquid ammonia in contact with the metal of the coil. It would probably yield a larger heat trans- fer in Fig. 19 if the liquid ammonia were sprayed over the brine coil from the top of the chamber. After the vapor is formed there can be little if any further heat removed, so that all surface in contact with vapor alone is of little value. FIG. 80. Liquid Receiver. In the Vogt brine cooler, Fig. 81, the brine is passed through the horizontal tubes running between the two head plates in a four-pass course, while the liquid ammonia is introduced at the center of the shell. In this there is ample heat transfer and the surface is efficient. Fig. 76 would represent a double-pipe brine cooler as well as a condenser if the liquid ammonia were placed on the inside of the coil and the brine were on the outside. Fig. 82 illustrates a triple-pipe brine cooler. In this, liquid ammonia enters the annular space between the two inner tubes 162 ELEMENTS OF REFRIGERATION of a set of three consecutive tubes at A . This space of one line is connected to the space on the next level by the special return bend B in the same manner as was used in the double-pipe con- denser. This is then repeated at alternate ends until the outlet C is reached. At this point is the suction pipe leading to the compressor. The brine enters at D and passes through the special casting into the outer annular space and then by similar castings at E it enters the second row, finally reaching F } at which point it is connected to a return bend and enters the center of the middle tube. Finally, by pipes and return bend it reaches the Outlet f or NH 3 Vapor Brine Leaves FIG. 8 1. Vogt Shell Brine Cooler. point of outlet G. Of course this appears to be partly counter current and partly parallel flow, but it must be remembered that the ammonia at all parts is at practically the same tem- perature, since there is little drop of pressure through the cooler. The brine cooler shown in Fig. 83 is that built by the Baker Co. The ammonia lies in the inclined inner tubes and is intro- duced at A, passing down to the various pipes. The vapor is drawn through the nozzle B, and up to the separator C to the outlet D. Any liquid taken up is removed by the separator and sent back through E. Brine enters at F and leaves at G. The connections are made by return bends. TYPES OF MACHINES AND APPARATUS 163 164 ELEMENTS OF REFRIGERATION TYPES OF MACHINES AND APPARATUS 165 Steam Condensers. The ordinary forms of steam con- densers can be used when desired, but because of scale troubles and because so much condensation is demanded for distilled FIG. 84. Arctic Oval Flask Steam Condenser. water in ice plants this is done at atmospheric pressure in flask condensers. Fig. 84 is made of sheet iron. Water is dis- charged over the surface of the flask and condenses the steam within. The outside and inside surfaces of the condenser may FIG. 85. York Steam Surface Condenser. be cleaned easily. In Fig. 85, the regular shell type of steam condenser is shown. The tubes are of brass and although usually held in place by soft packing they are expanded in the brass tube sheets in the figure shown. The left-hand tube 166 ELEMENTS OF REFRIGERATION a t w TYPES OF MACHINES AND APPARATUS 167 plate with the water head is allowed to expand back and forth, thus caring for expansion. The steam fills the whole inner chamber of the shell and passes around the left-hand tube sheet and cap. One of the latest developments of refrigerating machines is the Westinghouse-LeBlanc evaporative refrigerating machine shown in Fig. 86. This was described by Mr. J. C. Bertsch before the American Warehouseman's Association in December, 1915, and reprinted in Power for January n, 1916. In this a high vacuum is maintained in the evaporator A by means of a series of steam nozzles B, from which steam at a high velocity issued, entraining with the jet any air or vapor which may be around the steam jets in the space C. By making the nozzles long enough and of proper shape the final pressure of the steam will be low at the end of the nozzle. The jets of steam and entrained air and vapor enter a diffuser D where the velocity is decreased and the pressure increased to such a value that the steam and vapor may be condensed by the water supply in the condenser E. This is supplied by the circulating pump F, the water coming from the cooling tower G which has received the warmed circulating water from E. The air pump H is a Westinghouse-LeBlanc centrifugal air pump and withdraws the condensation and air from E. The water of condensation is discharged into / and is cooled by a coil and flows back as sealing water for the pump. A high vacuum existing in B means a high vacuum in A , and consequently the brine in the tank / is sucked up into this vessel and passes through the perforated plate K into an inner chamber, where it is broken up into a number of drops which, falling through the space of low pressure, are subject to evaporation of part of the water content. This of course cools the brine on account of the heat of evaporation coming from the liquid, and by the time it reaches the bottom of the evaporator it is cool enough to be circulated by the brine pump L through the brine system M t after which the warmed brine is discharged into the surge tank or receiver /. The brine has been concentrated in A by evaporation and consequently 168 ELEMENTS OF REFRIGERATION water must be added in / to reduce the concentration by the proper amount. This is done by the float valve. The various pumps are operated on the same shaft by a steam turbine. The stuffing-boxes of the brine pump are water sealed to keep out the air. TYPES OF MACHINES AND APPARATUS 169 The ejector B, composed of nozzles and the diffuser, are such that the vacuum carried has a temperature of boiling of 50 below the temperature of the cooling water used in the condenser. If a lower temperature is desired, say 70 to 100 below the cool- ing water, two of these are used in the series, as shown in Fig. 87. Binary refrigeration is the name given to the use of a mix- ture of two different refrigerating media such as CC>2 and S0 2 . There has been no gain shown from the use of these. The late Mr. E. Penney reports in the Transactions of the American Society of Refrigerating Engineers experiences of himself and others in this field. In all refrigerating apparatus the use of thermometers is important. By their use combined with that of the pressure gauge the action of the apparatus may be known. Thus the condition of the vapor entering the compressor may be known by the temperature of the vapor at suction pressure, and by thermometers in the discharge pipe the quality of the suction vapor may be known by the amount of superheat in the dis- charge gas. The water and brine temperatures tell whether the surfaces are dirty. All instruments are of value in the proper operation of a plant. Cooling Towers. Where^ water for condensing is scarce some method of cooling is necessary. Cooling towers are used for this purpose. In these, water is allowed to flow over screens of galvanized wire, glazed tiles, wooden slats or some other form of baffle to break the water up into small particles, and while in this condition it is brought in contact with air, which will be heated and absorb some moisture. The heating of the air cools the water and the evaporation of the water taken up by the air removes more heat. This is the principle of the cool- ing tower: the heating of air and the evaporation of part of the water removes sufficient heat to cool the main body of the water so that it may be used again. Of course the only place from which the heat of vaporization and heat for the air can come is the water. Fig. 88 illustrates one form of cooling tower. In this hot 170 ELEMENTS OF REFRIGERATION water is pumped through the pipe C to the boxes D D arranged at the top of the tower on the sides. This water then flows into a series of pipes E, which are slotted on top, from which it flows over the mats B, made of wire screens. The air FIG. 88. Cooling Tower. blown in by four fans F meets the water falling in small drops over the screens. Here it is warmed and as its moisture capac- ity increases there is some evaporation. The tower proper is made of sheets of steel stiffened by angle irons. If a sheet metal top is placed above the top in the form of a TYPES OF MACHINES AND APPARATUS 171 chimney, the fans may be omitted, as the chimney effect is sufficient to cause the proper circulation of air. In some of these cooling tow- ers glazed tiles on end form the surface over which the water is discharged. Such a tower will require about 0.2 sq.ft. of ground area per gallon of water cooled per minute. In the Hart Cooling Tower shown in Fig. 89 there is no fan. The tower consists of a series of cooling decks C, D, E, F, spaced from 3 to 7 ft. apart, depending on the amount of cooling and the quantity of water to be cooled. The cooling decks are made up of trays placed in a staggered position on the upper and lower flanges of the I-beam supporting the deck. The water from the supply pipe A is delivered through a set of spray noz- zles B above the first set of trays and there falls over the successive trays, a total drop of from 20 to 50 ft. The splashing of the water as it strikes the tray causes it to fall in drops. To prevent the spray from being lost the projecting shields G are FIG. 89. Hart Cooling Tower. 172 ELEMENTS OF REFRIGERATION added. These not only catch the water blown away but they drive the air down into the tower when the wind is blowing, causing it to rise through the center or on the other side. In this way the wind is applied to operate the tower and in calm weather the chimney effect from the heated air causes a cir- culation. The moisture in windy weather is usually caught on the leeward shield and delivered to the next deck. This and other atmospheric towers occupy from i to if sq.ft. of ground area per gallon of water per minute. In Fig. 90 the Thomas nozzle, used to spray water over a basin, is shown. In this the hot water is pumped to the nozzle and is delivered in a fine spray. The discharge orifice is made by the helical opening between the edges of a strip formed into a helix. The amount of opening may be regulated by the central spindle operated by a rod which controls all of the nozzles as shown. This spray of water warms the air and permits evaporation, so that the water falls to the tank or pcnd in a cooler condition. These ponds into which the spray falls should have about 2 sq.ft. of area for each gallon per minute flowing. Another method of cooling water is to discharge it into a cooling pond and to cool it by surface evaporation, the hot water entering at one end. If the pond is sufficiently large the water is cooled by the time it reaches the other end of the pond or reservoir from which the cooling water is taken. These ponds should have about 70 sq.ft. per gallon of water per minute or 9 sq.ft. per horse-power hour per day. In all of these arrangements the cooling has been done by the heat utilized to warm air and evaporate water. The heat to do these two things has to come from the water and hence the water is cooled. The amount of moisture which the air will carry is called the amount to saturate it. The air will carry no more moisture at a given temperature, but since the amount to saturate it varies with the temperature the capacity is increased by warming the air. Thus if at 75 i cu.ft. of air will carry 9.4 grains of moisture, the quantity is increased to 14.9 grains if the temperature is increased to 90. If air at 75 TYPES OF MACHINES AND APPAEATUS 173 I f a 174 ELEMENTS OF REFRIGERATION contains only 4.7 grains per cubic foot it is said to be one-half saturated and it could take up 4.7 grains more before satu- ration is reached. If at the same time the temperature were raised to 90 it would take up 10.2 grains before reaching sat- uration. Now this evaporation removes heat and it is one of FIG. 91. Wet and Dry Bulb Hygrometer. the important methods of removing heat in a cooling tower. That cooling towers may evaporate water on rainy or freez- ing days when the air is saturated is seen to be possible by the figures above, when it is remembered that the air is raised in temperature and with it the capacity for moisture. Thus air entering at 75 and saturated will require an evaporation of 5.5 grains per cubic foot of air to saturate it at 90 if this is TYPES OF MACHINES AND APPARATUS 175 the temperature of leaving. In most cases the air will leave at or near the temperature of the hot entering water and hence the capacity for moisture is increased. The amount of evaporation per cubic foot of air will depend on the amount of moisture in the air at entrance. The condi- tion of air is given by its relative humidity. This is the ratio of the amount of moisture in a cubic foot of air to that required to saturate it, as was stated on page 50. The instrument used to determine this is called a hygrometer, and the simplest form is"the wet and dry bulb thermometer type shown in Fig. 91. In this instrument one thermometer has a wet wicking around its bulb and on whirling these in the atmosphere the amount of evaporation from the wicking is fixed by relative humidity and is shown by the drop in temperature. By reading the wet and dry bulbs and the barometer Carrier's equation (38) on page 51 may be used to find the relative humidity. This formula has been used to form the chart of Fig. 92, so that the figure may be used to find the relative humidity for different temperatures of wet and dry bulb, since barometric changes are not sufficient to produce much variation. The chart also gives the amount of moisture per cubic foot at any condi- tion. The air required by a tower for a given amount of water is found by equating the energy in the substances entering and leaving. It is found that the water may be cooled to a temperature much below the atmosphere in dry weather, the final temperature being about 5 above the wet bulb temperature. In times of high relative humidity of 70 or 75% the water will leave at about the atmospheric tem- perature, but when the relative humidity is 40% it may be from 10 to 15 below the atmosphere, showing that the evap- oration of water has produced the principal cooling. The leaving temperature may be taken at about 5 above the wet bulb, although this may be i, 2 or even o above the air for high humidity. To compute the amount of water cared for by i cu.ft. of air entering the following method is used: 176 ELEMENTS OF REFRIGERATION 150 Difference in' Temperature SO 42. 38 34 3Q 26 22 18 14.12 10 8 6 30 4 6 Relative Humidity 70 FIG. 92. Relative Humidity and Moisture according to Carrier's Formula. Let t cd = temperature of dry bulb in air entering; taw = temperature of wet bulb in air entering; t' C d = temperature of dry bulb in air leaving; t'aw = temperature of wet bulb in air leaving; / = temperature of water at exit; t' = temperature of water at entrance; p = relative humidity at entrance of air; p = relative humidity at exit of air; Bar = barometric pressure in pounds per square inch; p = steam pressure at temperature t a a\ TYPES OF MACHINES AND APPARATUS 177 p f = steam pressure at temperature t ' ad ; m = weight of i cu.ft. saturated steam at t ad ', m' = weight of i cu.ft. saturated steam at t' a d\ M = weight of water entering per cubic foot of air at entrance ; Assume: I aw * ad or Then Moisture per cubic foot of air at en trance Volume of air at exit per cubic foot at entrance i44(Bar-pj) 53.35(^+460) = y , , , 53-35 X(/ Moisture in air at exit per cubic foot at entrance Bar pp t'ad +460 t,, / \ =^ vX; -- ^-Xm' = m" ...... (10) Bar p t ad +46o Moisture absorbed = m" mp = m" f ..... (n) Energy entering tower: With i cu.ft. air + )= 4 i44(Baf _ } _ 0.4 , 0.4 With m Ibs. moisture = m$iJ. . . . . (13) With M Ibs. of water =Mq' t J ..... (14) Energy leaving tower: With air of V cu.ft. (,5> 178 ELEMENTS OF REFRIGERATION With m" Ibs. of moisture =m'"i'J. . . , . (16) With (M-m" f ) Ibs. of water = (M-m'"}q r J. . . (17) In these i' is the heat content of vapor in saturated or super- heated condition and q f is the heat of liquid. By equating these the quantity M may be found. This gives the amount of water per cubic foot of air entering, or the reciprocal will give the cubic feet of air per pound of water entering. In this way the air for a given amount of water may be found and the fan to introduce this air or the chimney to suck this air may be computed. The evaporation per pound m'" entering, -rp, will give the amount of make-up necessary. In designing nozzles for cooling fountains the assumption may be made that the evaporation will reduce the temperature provided the final temperature is above the wet bulb tem- perature. The number of nozzles may be found from the quantity of water by using the following data: The capacity of the spray nozzles of the Thomas form is 150 gallons per minute under 4 Ibs. per square inch pressure. For ordinary spray nozzles the discharge in gallons per minute is given by the table : Size, inches. 5 Ibs. pressure. 10 Ibs. pressure. i-5 I S 21 2 . 40 60 2.5 70 9 3.O 1 2O 140 A velocity of 5 ft. per second at the entrance to the nozzle will give the discharge at 5 Ibs. pressure. The tank or reser- voir used with these nozzles should have about i\ sq.ft. of sur- face for every gallon per minute. When the weather is warm a second spraying is necessary in successive nozzles over separate reservoirs. The cooling pond may be made of such a size that i sq. ft. will care for 3^ B.T.U. per hour per degree difference in tern- TYPES OF MACHINES AND APPARATUS 179 perature between air and water; 70 sq.ft. per gallon per min- ute of water to be cooled has been suggested for the area of the pond. Safety Devices. There are several devices which are in- stalled in all plants using poisonous or suffocating gases to pre- vent loss of life and make the operation of the plant possible. One of the important ones is a helmet to wear over the head when it is necessary to enter a room filled with fumes to repair a break, FIG. 93. Improved Vajen Helmet. to shut a valve, or to rescue a person. There are several of these in use. One of them is shown in Fig. 93. The Vajen helmet weighs 10 Ibs. and fits over the shoulders, being strapped tight on a wool gasket. The weight is carried by the shoulders, leav- ing the head free to turn. The air contained in the reservoir under pressure is sufficient for one-half to one and one-half hours' use. The helmet is made of fire and water-proof mate- rials, and by the large double-plate mica- covered openings guarded by cross bars one can easily see to work. Rotary cleaners are provided to clean these if obscured by smoke or 180 ELEMENTS OF REFRIGERATION moisture. Telephonic ear pieces with special sounding dia- phragms enable the operator to hear distinctly and a whistle on front of the helmet makes it possible for the operator to signal others. The air reservoir is charged in two minutes by an air pump, and although this is a short time the reservoir should be kept charged. By opening the valve on the top reservoir air is discharged into the helmet in front of the nostrils of the wearer. This is above atmospheric pressure and forces the gases from respiration through the absorbent lambs-wool collar gasket and prevents the entrance of other gases. The top of the helmet is braced to protect the wearer against danger from falling objects, as the helmet is intended for use in fires or in chemical works. To guard against fatal results from accidents rules are made for the management and installation of refrigerating plants in large cities. Among certain rules formulated by the city of New York the following are noted: It is unlawful to operate a plant with gases under pressure without a license from the fire commissioner. An emergency pipe with valve outside to discharge gases into water sufficient to absorb full charge is to be installed. All refrigerating machines must be equipped with safety valves to discharge at 300 Ibs. per square inch pressure for ammonia, 1400 Ibs. for carbon dioxide, 100 Ibs. for sulphur dioxide and 100 Ibs. for ethyl chloride. These are to discharge into emergency pipes or to the low-pressure side of the system. There must be provisions for exit into the outside air or to a hall from which gas can be excluded for all rooms when the pressures are above the following limits: Ethyl chloride 40 Ibs. per square inch Sulphur dioxide 60 " Ammonia 100 l ' Carbon dioxide 500 1 1 All fittings are to be tested to twice the maximum pressure and pipes to three times the maximum. TYPES OF MACHINES AND APPARATUS 181 No open flames are allowed in any rooms having pressure pipes. Helmets must be installed in all plants. Pipes are to be tagged showing kind of substance within. Storage of extra refrigerating substance will not amount to more than 10% of capacity. The cylinders cannot be kept in the boiler room but in some cool place. When the plant has a capacity of more than 3 tons the operator must have a certificate. The United States Interstate Commerce Commission has provided certain rules relating to the cylinders for the ship- ment of gases under pressure. Some of these are as follows: Cylinders must comply with requirements and be made of lap-welded pipe of soft steel of best welding quality. They may be made seamless. The heads should be welded in. The carbon is limited to 0.20%, phosphorus 0.11%, and sulphur 0.05%. The cylinders must stand 1000 Ibs. per square inch in a water jacket to give extension which must not be over 10% of volume. Cylinders must stand flattening out. They must be annealed. The cylinders must be stamped with name of owner. Gases which combine may not be shipped in one cylinder. Each cylinder must be tested once in five years under pressure. Test pressure is one and one-quarter times the pressure of vapor at 130 F., except for carbon dioxide cylinders, which are tested to 3000 Ibs. per square inch. CHAPTER V HEAT TRANSFER, INSULATION AND AMOUNT OF HEAT HEAT is transferred by radiation, convection and conduc- tion. In the first method a body starts a vibration in the ether, which is transmitted by it to another body which receives this energy of vibration and changes it into heat energy of the body. This form of transmission depends on the difference of the fourth powers of the temperatures of the two bodies. Although important in some cases, radiation does not play an important part in refrigeration. In the second method, particles of some medium, as air, are heated by a hot body and then by the bodily transfer of these heated particles the energy received by them is carried to a cooler body, which abstracts the heat. This method of heat transfer is one used for some types of refrigeration. The third method is that in which heat energy is applied to the molecules of one part of a body, and then by transmitting this energy to adjacent molecules the energy is gradually conveyed through the body. It is in this manner that heat is taken from cold storage rooms by the brine or ammonia, or heat is added to the room from the atmosphere. The last two methods of heat transfer must be examined in detail. If M Ibs. of substance are heated at constant pressure from a temperature ti to / 2 when the specific heat is c p , the heat required to do this is Q = Mc p (t2 1\) . . . ... . . (i) or (2) The first is correct if c p is constant, or is the mean value of Cp, and the second is correct if c p is a variable. The substance 182 HEAT TRANSFER, INSULATION 183 usually employed is air, and although c p for air is not constant, the variation for the temperature ranges used in refrigerating problems is negligible. Hence the first formula may be used with a value of 0.24 for c p . If now the air is conducted to a room or cooler and is brought back to the temperature /i, the same amount of heat must be abstracted, and so the heat Q taken from the first body has been given to a second body and the air or carrying medium has been left in its original condition. This heat has been carried by convection. In conduction the heat transmitted depends on the mate- rial, the temperature, the cross-section of the material and the length of the path. The equation for conduction is similar to that for the flow of the electric current. F = area of cross-section in square feet; / = length of path, or thickness, in feet; / = temperature on either side in deg. F.; C = constant of conduction, or B.t.u. per hour per square foot per degree for i ft. thickness. The value of C has been determined by various experiments, and by its use the amount of heat conducted can be predicted. When heat is transmitted through partitions, it is difficult to compute the amount of heat transmitted because it is hard to determine the temperatures at the edge of the plate on account of films of fluid which cling to the surface and make heat trans- mission difficult. Thus, if heat from the gases of a boiler is to be taken into the water in contact with the tube, and Eq. (3) is used to compute the probable heat transfer, using the C for steel of thickness /, and substituting the temperatures of the gas and boiling water, the heat would be equal to more than 250 times the amount actually transmitted. The great reduction is due to the effect of the films of gas and water fvhich cling to the sides of the tube and cut down the heat trans- mitting power. A thin film of gas or water has a much greater 184 ELEMENTS OF REFRIGERATION resistance than a thick wall of metal. The transmission through the gas or water film could be computed if the thicknesses were known, but these are quantities which vary, depending largely on the velocity of the fluids over the surface, and also upon the viscosity of those fluids. On account of this action exper- iment has been resorted to to determine a constant K, which is the amount of heat transmitted per square foot per hour per degree difference in temperature for the surfaces trans- mitting heat. Since in many cases the surface effects are the controlling factors, and not the main body of the partition, the thickness of the partition will not enter into the expression. With K the equation for heat transmitted becomes (4) K = E.t.u. per square foot per hour per degree; J F = area in square feet; / = temperature in degrees F. The value of K is now determined experimentally for the transmission of heat through metal walls in condensers, absorbers and such apparatus, and it is found that as the veloc- ity of the liquids on either side increases the value of K increases. It is also found that for greater differences in temperature the value of K changes, becoming less usually as the temperature difference increases. For the temperature differences usually found in ammonia and steam condensers, brine coolers, feed-water heaters and such apparatus, the value of K found in experimental work with a given set of temperature conditions may properly be used with other tem- perature conditions since there would not be enough change in temperature difference to affect the value of K. If K is a constant and the temperatures on one or both sides change along the length of the surface it is necessary to find the mean temperature difference in terms of the temperatures at the ends of each surface. Suppose that t hl and t h2 are the temperatures on the warm side at entrance and exit and that t ci and t cz are the temperatures at the same ends on the cool HEAT TRANSFER, INSULATION 185 side of the surface. At any point x the temperatures on the two sides will be t hx and t cx . The amount of heat transmitted through the differential surface at this point measuring from first end will give a rise in temperature of dt c to the cool sub- stance of M c pounds per second, and there will be a drop dt* on the warm side where M h Ibs. per second flow. Hence KdF(t hx -t Cx ) = -$6ooM h c h dt h =3()ooM c c c dt c . . (5) As dF increases dfa decreases and dt c increases for parallel flow but decreases for counter current flow. The upper sign refers to parallel current flow. ccc ^=3600- ........ . (6) Now or MnC* M c c c ~ t hl -t h2 ' Also t hl - foj = ^ M c c c [t Cl - t cx ] . f , (9) 186 ELEMENTS OF REFRIGERATION A/2 Afe Afc ge A..;.;.- . (24) where F = area in square feet; # = heat transmitted per square foot per hour per degree difference of temperature in B.t.u.; /t=room temperature in degrees F.; to = outside temperature in degrees F.; H = B.t.u. transmitted per hour. The value of K depends upon several factors: the surface, thickness and kind of material, air spaces and condition of air at surface. It also depends on temperature difference, but since the temperature differences are not large, this effect may be neglected. The following German method from H. Rietschel's Leitfaden zum Berechnen und Entwerfen von Luftungs- und Heizungs-Anlagen is usual for future reference for cases which have not been calculated in the text. The rate of transmission of heat through any substance depends upon the thickness and on the difference] of tem- perature. If for instance the wall shown in Fig. 96 is made up of several thicknesses, and the temperatures are those marked, the equations for the 3 I FIG, 96. Wall Section. transmission of heat through each section must give the quantity of heat transmitted by the wall, and these therefore must be equal to each other. The amount of heat conducted by any material per square foot of cross-section varies directly with the temperature dif- ference and inversely with the length. This gives (25) 192 ELEMENTS OF REFRIGERATION where C is the constant of conduction for i ft. thickness in B.t.u. per square foot per degree, / is the thickness in feet and t\ /2 is the difference of temperature. Using this for the wall shown in Fig. 96, the following results: Z7 kl/.f ,// \ ^2/,r ./ \ ^3/,r ,// \ / /;\ H = (ti-t 2 )=(t 2 -t3)=(t3-t o). (20) /I /2 /3 At the surface of any material there is to be found a temperature different from that of the contiguous space and it is this differ- ence which determines the flow of heat at the surface. At the surface the same formula holds, but since / is difficult to find, the quantity - has been l replaced by a and experiment is used to find the value of this for different materials and conditions of the surface. If a is the coefficient of transmission per square foot per hour per degree across this surface, this becomes at different sur- faces: The values of H in the sets above are all the same quantity, hence solving for temperature differences and adding, the fol- lowing results: . (28) _ai Ci a2 as L 2 Cs a4J Now X X = ^L. . Hence ^T - : r ; ; r- ( 2 9) HEAT TRANSFER, INSULATION 193 VALUES OF C Air, still o . 03 Air in motion o . 09 Asbestos paper 0.04 Blotting paper o . 04 Brass. . . 61.00 Brickwork 0.46 Building paper 0.08 Cement o . 40 Charcoal o. 03 Copper ' 202.00 Coke 0.05 Cork, compressed 0.022 Cork, granulated 0.03 Cotton 0.03 Feathers o. 040 Felt 0.02 Glass 0.54 Hair felt. . 0.026 Lead 20.00 Limestone 1.35 Lith o . 028 Marble, fine i . 88 Mortar and plaster o . 46 Mineral wool 0.05 Oak 0.13 Pine (along the grain) o. n Pine (across the grain) 0.06 Plaster of Paris 0.34 Sandstone 0.87 Sawdust 0.03 Shavings 0.05 Slate. o. 19 Terra-dotta o. 54 Tin 35-6o Wool o . 03 Zinc 74-oo The values of the quantities a, as given from Grashof and Rietschel, are of the form (30) IO,OOO d and e are constants, d depends on the condition of the air around the surface and e depends upon the material. T is the temperature difference between the air and the surface at any point. To determine the quantity T, a method of approximation is used until by practice one knows what to expect. The value of the term involving T, 10,000 is small, hence for a first approximation this term may be neglected and the value of the various #'s may be found. These may then be used to find K. (31) 194 ELEMENTS OF REFRIGERATION after this is known the following results: = etc. , T = ti-t\ or /"o-/ . These equations give the first approximations for T. In this way after T is found as a first approximation, the value may be used to find a second value of a and then a new value for T. In this way two or three trials will lead to the correct result. In any case the value of T is small and this is true par- ticularly for thick walls or in cases in which hto is a small quantity. Rietschel gives results used in practice for the value of T for masonry walls. These may be put into the form of an equation, T =16.2 4.001 ....... (32) This may be used for masonry walls with air spaces where / is the sum of the various thicknesses of masonry, although the result is slightly too large in this case, as the quantity K(tito) is smaller than for a solid wall of the combined thickness. For a single glass T is taken as (/i /o), while for double windows \(t^ h) is taken at each surface, since glass is so thin there is practically no temperature drop in it, the main resistance being at the surface. The value of T for wooden floors is given as r = i.8 F. The values of d as given from Grashof are as follows: VALUES OF d Air at rest as in rooms or channels ............ .......................... 0.82 Air with slow motion as over windows ............ ..................... i 03 Air with quick motion as outside of building ............................ 1-23 The values of the coefficient e are determined by Rietschel as follows: HEAT TRANSFER, INSULATION 195 VALUES OF e Brass, polished 0.05 Brickwork and masonry o. 74 Cast iron, new o . 65 Cotton 0.75 Charcoal 0.71 Copper o . 03 Glass o . 60 Mortar and lime mortar o. 74 Paper 0.78 Plaster of Paris o . 74 Polished sheet iron 0.092 Rusted iron. o . 69 Sawdust 0.72 Sheet iron 0.57 Tin 0.045 Water i . 07 Wet glass i . 09 Wool 0.76 Zinc ; o . 049 Wood o . 74 To explain the application of the above the wall given in Fig. 97 will be investigated. The wall is composed of 4 ins. of sandstone, 18 ins. of brick work, a 2-in. air space, 8 ins. of brick and i in. of plaster. Where sections of the wall actually *.* *l 'i I I V, l 1 II \ is; -18- FIG. 97. Wall Section. come in contact, there is no surface resistance and the wall may be considered as solid except for differences in values of C for the various materials. When air can circulate it is not considered an insulator as the convection currents carry heat from the warm to the cold side. The value of air space is in the surface resistance. To find a the various values of T must be known; now T is given by the following: 'a = fa t'z ; These quantities vary inversely with the different values of a, since d\ T\ = d2 Ts = a'zT'z = #4 Jo. 196 ELEMENTS OF REFRIGERATION As the quantities a do not differ by great amounts these various values of T are considered as equal quantities in com- puting a. T may then be found from the equation - - \ ? T=i6.2 4.oo/. In this case the total thickness is 31 ins. and r=i6. 2-4X^ = 6 F.; 12 IO,OOO . 03 = 02 = 0i = 0.82 +0.74+ 10,000 as = 1.59 = 02 = K= * _|- -i , i _| _ i _j_o.33 | i-5 + Q-66 , 0-083 2.OI 1.58 1.58 1.58 0.87 0.46 0.46 0.46 I 0.497+0.633+0.633+0.633+0.379 + 3. I 7 .62 = 0.131, The resistance of air channels is negligible because of the convection currents. For a floor or ceiling as shown in A, Fig. 98, the method is quite the same. When the high temperature is at the top, however, there is no circulation in the air space between the plaster and the floor and the air acts as an insulating material. When the high temperature is below or if an air space is in a vertical position, the circulation of the air transmiis heat by convection and the air does not act as an insulating material. HEAT TRANSFER, INSULATION 197 In any case, however, there is a resistance at the surface between the air and the partition due to the drop T. When the same constant K does not hold over a complete wall or floor owing to a change in the construction as occurs at studs in a partition or joists in a floor, the value of K for the whole surface is found thus: K(Fi +F 2 ) (tt - to) = KiFi (/i - to) +K 2 F 2 (h - to) K = KiFi+K2F 2 = 2, Fi+F 2 (33) 1 * 1 - FIG. 98. Floor Sections. In most cases the areas F have a common dimension, so that the areas are proportional to the widths. If these are bi and b 2 there results (Fig. 98), Kibi+K 2 b 2 K = bi+b 2 (34) The mean constant is not usually found for a wall in terms of glass and wall coefficient, as these are kept separate, but there is no reason why this could not be done, as happens with the coefficient for partitions with partition studs in the cases which follow. 198 ELEMENTS OF REFRIGERATION With the high temperatures above the air acts as an insu- lating substance and the following for the floor, Fig. 98 : 10,000 at joists, 0.05 1.57 12X0.06 8X12X0.46 1.57 at space between joists, K a = 12 3 + _ 5 =0.027 1.57 12X8X0.06 1.57 12X0.03 8X12X0.06 8X12X0.46 1.57 Combined K _ 3X0.05 + 13 XQ^7. 16 With the high temperature below on account of the convection currents, the air does not act as an insulating substance and the following results: 0=1.57; ,=0.05; K * -t^-a 4 - 1-25 5 =0.22; 1.57 ' 12X0.06 ' 8X12X0.46 16 This method may be used for various walls and partitions. The following values have been computed by the author and these values compared with those given by Kinealy, Riet- schel and others. HEAT TRANSFER, INSULATION 199 Values of a For brick and plaster or masonry. Outside a = I . 2 3+o.74+ 43Xl - 23+3lXa74r 10,000 = 1.97+0.00757 since 7 = 16.2 4/. Inside = 1.56+0.00577 = 1.65 0.023/. For wood and, approximately, paper, cotton, wool, coal and sawdust: Outside = 1.97+0.00757 = 1.98. Inside = 1.56+0.00577 = 1.57. For glass: Outside = i .83 +0.007 T /T = ti-to \ = 2 ' 7 ( = 35j. Inside with motion : = 1.63+0.0067 = 1.83(7 = 35). Inside without motion: = 1.42+0.0057; = 1-59(7 = 35). Inside with motion and wet from condensation: = 2.n+o.oo87 = 2.39. 200 ELEMENTS OF REFRIGERATION For double windows: Outside = 1.95(7 = 1x70); Center a = 1.51. Inside, dry a = 1.74. Pipe Covering. The use of pipe covering to prevent the conduction of heat from steam pipes or to brine pipes or vessels must be considered in this chapter. The discussion applies to covering on all circular bodies. The constants of this chapter may be used in this case. The transmission formula now becomes For flat plates of insulating material the expression to be used is For cork =0.022. For Q = heat per hour in B.t.u.; c = B.t.u. per hour per degree for i ft. thickness; TO = radius outside of covering in feet ; r\ = radius of pipe in feet; L = length of pipe in feet; F = area of surface in square feet; , -,,. . / = thickness of covering; to = temperature outside covering deg. F. ; t\ = temperature inside of covering deg. F. HEAT TRANSFER, INSULATION 201 Mr. L. B. McMillan has recently given values for c for various temperature differences. VALUES OF C Kind of Covering. Temperature Difference. 25 50 75 IOO 150 200 300 400 Johns-Manville asbestos sponge. Nonpareil high pressure 0.027 0-033 0.034 0.036 0.029 0-035 0.038 0.028 0.033 0.034 0.036 0.030 0-035 0.038 0.028 0.033 0.034 0.036 0.031 0.035 0.039 0.029 0.033 0.034 0.036 0.032 0.036 0.040 0.030 0.034 0-035 0.037 0.033 0.037 0.041 0.031 0.034 0.035 0.037 0-035 0.038 0.043 0.032 0-035 0.036 0.037 0.039 0.041 0.047 0.036 0.037 0.038 0.039 0.044 0.045 0.054 Gary 85% magnesia Johns-Manville magnesia Carey carocel Johns-Manville asbestocel . . Johns-Manville aircell The insulating of cold storage houses is accomplished by the use of wooden walls with air spaces as shown in Fig. 99, brick walls with wooden backing as shown in Fig. 100, brick walls with air spaces as shown in Fig. 101 and brick walls lined with some non-conductor as shown in Fig. 102. The main purpose in using these is to increase the heat resistance. The older storage houses were of wood and the method shown in Fig. 99 gave good satisfaction. The use of paper or felt coated with some substance to waterproof it keeps the saw- dust and air space dry as well as making the wall air tight. Sawdust or mineral wool is used in the air space for the purpose of preventing air circulation. This is accomplished in air spaces by using horizontal strips which should be put at inter- vals between them. Fig. 100 shows a construction recommended by the Frick Company for warehouses. At times cement, concrete or asphalt is put on wooden floors as a wearing sur- face. Fig. 10 1 shows the brick type of insulation which is valuable although expensive. Where space is valuable some of the brick may be replaced by cork board or by lith as these have more resistance. The type shown in Fig. 102 illustrates such a protection. Two thicknesses of cork board insulation with cement between are used to get the neces- sary thickness, as these boards are usually made no greater 202 ELEMENTS OF REFRIGERATION than 3 ins. in thickness. The cement is usually a tar, asphalt or some other waterproof binder. The surface is sometimes protected with a cement plaster of waterproof properties. f FIG. 99. Wooden Wall with Sawdust Fill. (Elevation above, plan below.) At times air spaces are introduced between the various thicknesses of boards as shown in Fig. 103, and in some cases the outer layer may be replaced by two of lumber with paper between. The combination used depends upon the peculiar!- Brick FIG. ioo. Brick Lined with Wood. FIG. ioi. Brick Wall with Air Spaces FIG. 102. Wall with Lining of and Tile Lining. Cork or Lith. 203 204 ELEMENTS OF REFRIGERATION ties of the designer. The Union Fibre Co. suggests the use of their linofelt as part of the construction. This is a felt FIG. 103. Brick Wall with Wood Lining. FIG. 104. Use of Lith and Linofelt. Saw Dusb i;.Saw Dust FIG. 105. Floor Construction. made of flax fiber and held between two thicknesses of water- proof paper. The construction is shown in Fig. 104. Floors are insulated as shown in Fig. 100 and Fig. 105, when above the first floor, while for floors on the ground, Fig. HEAT TRANSFER, INSULATION 205 1 06 shows the method used. These are carefully drained and the endeavor is made to keep all moisture from the insulating 8 S -.- i.-.-y.': '- V,' } : 'J ffSt- Q Z 3) o o: C5 z O cr O 3 material. Fig. 107 shows a form of wall using an interlocking and bonding section. 206 ELEMENTS OF REFRIGERATION The construction used in making grain bins consisting of planks 2 X 10, i X 10 or 1X12 laid on the flat side, has been used for cold storage structure by some builders with success. In some cases such walls have been veneered with 4 ins. of brick. All of the preceding drawings are given to show some of the many methods used. There may be many changes sug- gested. The general method for finding the insulating value of a wall has been given so that for any new type of construc- tion the insulating value may be determined before the con- FIG. 107. Special Tile Wall. struction is made, in order to ascertain whether or not addi- tional expense would be justifiable. There are several elements entering into the problem of construction of a cold storage warehouse. Not only does the original cost and the insulating value enter into the prob- lem, but also the cost of insurance and depreciation must be considered. R. E. Spaulding and J. H. Nielson have pointed out that although a wood ice-house will cost $2.00 per ton of capacity, and a fireproof masonry or concrete structure cf the same insulating power will cost $2.50 per ton of capacity, the latter costs less to operate because the depreciation must be figured at 10% for the wood, and at 3% for the fireproof HEAT TRANSFER, INSULATION 207 structure, building insurance $5.00 per hundred on 80% of the wooden building and 40 cents on 80% of the fireproof building while for the ice the insurance is $5.00 for wood and 40 cents for concrete per 100 tons of ice. Considering the FIG. 1 08. Floor Construction. interest at 5% with the above items the yearly cost is 43 cents for the cheap wooden house, and 21 cents per ton in the fire- proof house. The methods of this chapter have been used to compute the values for various types of insulation and the results are FIG. .109. Reinforced Concrete Roof and Ceiling. given on p. 211. These values may be used, if desired, to make preliminary calculations. Fig. 108 shows a construction of floors using arches while Fig. 109 illustrates the method of hanging a ceiling on an inclined reinforced concrete roof to form an air space or to give a level ceiling. The construction of doors is an important question in the 208 ELEMENTS OF REFRIGERATION operation of a warehouse. Not only must these be non-con- ducting, but they should be air tight, because the temperature difference might set up a strong circulation of air through cracks, and this must be avoided. To prevent this, leakage doors were originally made as shown in Fig. no. The numerous corners caused troubles, and to do away with them other arrangements have been invented. Fig. in illustrates a section through the Stevenson door in which a hemp gasket is forced into place by the closing of the door. The No Equal cold-storage door is shown. In the former the soft gasket projects ^from the door flange while in the latter the hair felt which is inclosed in a ring of canvas or rubber is placed in two grooves beneath a gasket of rubber or leather in the concave quadrant corner of the door. The jamb is rounded, removing all sharp corners which would be bruised FIG. no. Section of Early Form of Door. and which would prevent proper operation. The threshold of the doors requires special treatment. It should be beveled off to the floor line. The packing must be tight here to make a proper fit. > In many cases, the insulation at doors is made more perfect by using a vestibule before the main door, thus requiring two doors to be opened at the time entrance is effected. The insulation of ice tanks is shown in Fig. 112. The method of construction and computation is the same as that used above. The tank may rest on several layers of cork board or on wooden sleepers and the sides may be insulated with granulated cork. The heat loss must be cut down to a low value. In all of the above methods of insulation care must be taken to prevent moisture from entering the insulation, as the value is decreased when this becomes wet and the wood or material HEAT TRANSFER, INSULATION 209 Stevenson Door. . , 1 - :f: ;:^:l i^-f f ' 1 fe 1 ^) FIG. in. Arrangements of Doors. 210 ELEMENTS OF REFRIGERATION may rot. In addition the insulating material should be of such a nature that vermin cannot breed in it. To make the foundation waterproof the cement concrete may be treated with a chemical, but if this concrete cracks a leak occurs. To guard against this the concrete may be coated with a waterproof plaster, which is less likely to crack, or the foundation may be coated with coal tar or pitch and covered Wood Cork Cork FIG. 112. Tank Insulation. with tarred felt and burlap covered with tar. Care must be taken to waterproof concrete, as water is drawn up by capil- lary attraction 10 to 20 ft. above the standing water. A good method of waterproofing is to use bitumen cement, which is strong but not brittle, applying this on both sides of each of two or three layers of felt. For floors use two or three layers on top of the concrete floor and then apply top concrete. For roofs, a layer of brick may be put on top of felt followed by 6 ins. of earth with grass. One of the chief points i to consider is to make the yearly cost of refrigeration a minimum. This includes yearly cost for interest, depreciation, taxes and insurance on insulation, with cost of storage space as well as the cost of refrigeration. The values of K for different types of insulation have been computed and are given as follows: HEAT TRANSFER, INSULATION VALUES OF K 211 Total Thickness of Brick Masonry. Walls. 4" 8" 12" 16" 2O" 24" 28" 32" Solid brick 0.55 o. 30 0.31 o. 25 O. 21 o 18 o 16 0.15 Solid brick with plaster 0-51 o-37 0.29 0.24 O. 21 0.18 0.16 0-15 Brick with one air space o. 27 O. 22 0.19 0.17 0.15 0.13 0.12 Brick with one air space and plaster .... 0.26 O.22 O.IQ 0.17 0.15 0.13 O. 12 Brick with air space, 4-in. tile and plaster o. 14 0.13 O. 12 O.II O. IO 0.09 0.09 Brick with 3-in. cork and plaster 0.07 0.07 0.07 O.O6 0.06 0.06 0.06 0.06 Brick with 2-in. cork, f-in. cement, 2-in. cork, |-in. cement O.o6 0.06 0.05 0.05 0.05 0.05 0.05 0.04 Sawdust Thickness. Walls. o" 6" 12" 18" 24" 30' | in. wood, paper, | in. wood, sawdust, f in wood paper, in. wood o. 167 0.044 0.025 0.018 0.014 O.OII Same with shavings in place of sawdust . . . 0.167 0.062 0.039 0.028 O.O22 0.018 | in. wood, paper, in. wood, sawdust, in. wood, paper, | in. wood, air, | in. wood, paper, in. wood. Fig. 99 O. IO2 0.038 0.023 0.017 0.013 O.OII 1 in. wood, paper, in. wood, air, | in. wood, paper, 3 ins. cork, % in. cement plaster O OS7 Same with 6 ins. cork * w j / 0.036 PARTITIONS | in. wood, 12 ins. granulated cork, f in. wood # = 0.024 \ in. plaster, 3 ins. cork boards, 4 ins. granulated cork, 3 ins. cork board, \ in. plaster # = 0.027 Tile partitions plastered single # = 0.30 j Tile partitions plastered double # = 0.21 FLOORS Fig. 108, ist figure # = 0.022 2d figure # = 0.062 heated room below # = o . 030 heated room above 3d figure K = 0.060 212 ELEMENTS OF REFRIGERATION 12 ins. concrete, 2 to 3 ins. cork boards, 2 ins. cement ^ = 0.038 Glass, single thickness K = i . 06 Glass, air, glass # = 0.41 Glass, air, glass, air, glass . K = o. 26 6 glass and 5 air layers K = o. 12 FIG. 113. Norton's Method of Finding K. The value of K for cork board has been found by Prof. Norton in several ways. In one case he built a cubical box HEAT TRANSFER, INSULATION 213 of the cork to be tested, and placed a piece of ice within. By weighing the amount of water from the ice the heat carried in, was found. In a second test a fan was placed within the box and electric lamps or resistances were used to produce heat and by circulating the air the temperature was made uniform ; then by measuring the energy to hold the box at some temperature above the room temperature, the heat loss per degree was found. To get the area of the box surface, the sur- face of a cube at the mean thickness of the cork was computed. In addition to this the heat added to warm oil circulated in a tin lining on the inside of the box was found electrically and reduced to B.t.u. per square foot per twenty-four hours. Norton also placed a wire grid between two thicknesses of cork board. After allowing for heat losses at the edge by keep- ing grid at a certain state the heat loss in electrical energy per siuare foot per degree per hour was found. The mean value suggested by him for cork is ^ = 0.022. These methods have been used by German experimenters and others for the deter- mination of K for various substances. There are other elements entering into the heat supply of refrigerating plants. Any air leakage or ventilating supply must be cooled off. For M Ibs. of air per second, the heat per hour will be: M = weight of air per second; c p = specific heat of air = 0.24; /o = temperature outside in deg. F. ; ti = temperature inside in deg. F. p = pressure in pounds per square inch; V volume per minute in cubic feet at p Ibs. pressure and absolute temperature T\ = 53-35- The heat produced by persons is given by the following results by Benedict in the table below: 214 ELEMENTS. OF REFRIGERATION Adult at rest, asleep .......... 258 B.t.u. per hour sitting .......... 396 Adult at light work ........... 670 Adult at moderate work ....... 1150 Adult at severe work .......... 1780 For children an allowance of 300 B.t.u. per hour may be made. Heat of Machines and Lights: For electric lights ....... i watt-hour. ... 3 .41 B.t.u. For power ............. i K.W.-hr ..... 3410 i H.P.-hr ...... 2546 For gas where used : i cu.ft. illuminating gas ............... 700 B.t.u. i cu.ft. natural gas ............... ..... 1000 i Welsbach burner uses 3 cu.ft. of gas per hour. i' n?h-tail burner uses 5 cu.ft. of gas per hour If substances are chilled the following specific heats and constants in table on page 215 are used. These values have been obtained by reference to various authors and are collected here in a separate table. See Storage Rate Guide for rules relating to charges for storage, rules for labor charges, liability, etc. Having the amount of goods put in a storage room the heat per hour to cool this refrigeration in tons is: Tons= = . . . (35 ) 199.2X60 M = weight of goods including weight of container; c = specific heat of substance ; t a = temperature of outside air or temperature of goods put in storage ; t r = temperature of storeroom or temperature of goods after storage; /<=heat of fusion if goods are frozen; h = hours required to cool goods; Q = B.t.u. per hour. HEAT TRANSFER, INSULATION 215 COLD STORAGE DATA Substance. Temp. Deg. F Specific Heat Latent Heat of ' Fu- sion. Time of Stor- age. Cost of i mo. Stor- age. Cents. Cost of Each Suc- cessive mo. Cents. Unit of Storage. Before Freez. After Freez. Apples Bananas Beans, gree.i. . . Beans, dried. . . Beef, fresh Beef, salt Beer 30-35 34-40 36-40 40-45 30-38 40-45 30-36 36-40 15-20 32-36 34-36 36-40 40-45 32-36 34 30 40-45 40-45 30-31 - 5 . 35-40c 35-40 25-30 25-30 30-35 15-20 32-36 32-40 32-50 32-36 30-32 32-36 32-50 30-34 36-42 32-36 30-36 30-32 40-45 34-38 15-20 36-40 40-45 36-40 36-40 36-40 34-36 40-45 0.92 0.91 0.90 0.70 0.60 0.90 0.91 0.60 0.93 0.92 O.Q2 0.84 OT64> """oT^rf^ 0.90 6 mo. 3 mo. 20 10 15 itot * ia| i to * i 20 10 IS 12* IS 25 25 5 12* 10 i 20 12* Si.50 t $ .60 t $ .60 t 1 5 10 10 12* i 15 10 10 25 5 5 i * 25 i i * 25 12 5 35 15 10 10 itoi 10 i to * i 15 7i 12 12* 10 25 20 5 12* 7* i 15 12* 2.00 o .75 o .75 i 4 7* 7* 12* i 15 7i 10 25 4 4 i 25 i i i * 25 12 5 35 Barrel Bu. basket loo Ibs. lib. i Ib. Half barrel Quart i Ib. 100 Ibs. Box or crate * bu. basket loo Ibs. loo Ibs. Large crate Barrel Per cu.ft. at $5 val. 100 Ibs. 30 doz. case, 55 Ibs i Ib. glazing loo Ibs. loo Ibs. per season each per season each per season i cu.ft. i Ib. 10 Ib. basket Box Box 40 qt. can lib. 2 bu. sacks Box 100 Ibs. Tub Sack * bu. basket * bu. basket i Ib. i Ib. Barrel 2* bu. i Ib. i Ib. i Ib. i qt. box. i barrel i bu. crate i melon i barrel .... 0.38 0^84 0.48 90 3 mo. Berries Butter Cabbage Cantaloupes. . . Cherries, fresh . Cherries, drie J. Cheese Celery Cider ' 84 129 short 5 mo. 3 wks. 4 mo Cigars Dates Eggs Fish, fresh Fish, dried Fruit, dried. . . . Furs, coats. . . . Furs, rugs Furs, uncured. . Game Grapes Grape fruit .... 0.84 0.76 o.7S 0.58 0.84 0.40 0.40 100 IOO 6 mo. 8 mo. .... 0.80 0.92 0.92 0.92 0.90 0.67 0.91 0.92 0.84 0.40 105 2 mo. 3 mo. 3 mo. 5 mo. 6 mo. 3 mo. 0.47 0.8i 0-44 124 114 Milk Mutton Onions Oranges Oysters, bulk . . Oysters, shell . . Peaches Pears Pork, fresh .... Pork, cured. . . . Potatoes Poultry Sausage, fresh. . Sausage , sm oked Strawberries. . . Vegetables, bbl. crate. Watermelons.. . Wines 0.92 0.92 0.50 0.80 0.80 0.70 0.60 0.92 0.91 0.91 0.92 O.c,0 .... i mo. 2 mo. i mo. 6 mo. 3 mo. short 2 to 4 weeks 2 to 4 weeks 0.30 0.42 0.40 90 105 102 By use of Eq. (35) the amount of refrigeration to cool the goods and freeze them may be computed. It is well 216 ELEMENTS OF REFRIGERATION to note that the time required to do this is an important factor. If the time is short the amount of refrigeration is large. This amount of refrigeration for this reason may be much larger than that required to care for the heat loss from the room. CHAPTER VI COLD STORAGE THE purpose of cold storage is to prevent the development of life which would cause decay of living tissue; it is also used to prevent the development of living organisms. It is used not only for the storage of foodstuffs, but for the storage of furs, trees, flowers and other articles which require a low temperature for their proper keeping. The principal application of cold storage is to the storage of food products. In 1905 W. T. Robinson stated that there were over $200,000,000 worth of products stored, divided between (a) living substances, such as eggs and fruit, requir- ing a moderate temperature and (b) non-living, as meats, butter and cheese, requiring a low temperature. In 1909 the value of goods passing through cold storage amounted to $2,585,000,000, ranging from $25,000,000 in fish to $1,500,000,- ooo in meats, the meat annually chilled alone amounting to 20,000,000,000 Ibs. There were 160,000,000 cubic feet of stor- age space exclusive of breweries, packing houses, creameries and stores. These goods are stored for various lengths of time. Meats may be frozen and then stored for a long time. There is some improvement in quality at first and although with lengthy storage there is no deterioration in the meat, the flavor is lost and for that reason long holdings are not good. Poultry may be frozen and for a certain length of time there is an improvement in quality. Eggs may be held for long periods and except for a loss of weight there is no ill effect. Cheese improves as it ripens in cold storage but after ripening there is no improvement. Butter suffers slightly in taste on long storage. Apples and pears are improved by holding, as certain 217 218 ELEMENTS OF REFRIGERATION chemical changes take place, while strawberries and peaches lose their flavor rapidly. These various articles require special temperatures for their storage and hence there must be special rooms in warehouses for each article. The value of cold storage is to equalize the supply of food- stuffs and make it possible to have certain foods during the whole year. The consumers claim that goods are held until the off- season and then exorbitant prices are asked, while the cold- storage men claim that prices are reduced by the ample supply which exists in the off-season. Formerly one of the great evils of the business was the lengthy storage of articles for times of high prices, hence laws have been made in many States to correct the evils of cold storage of foodstuffs which have hampered the business and brought about other evils. The United States Government is planning a national cold-storage law to cover interstate business and business in the District of Columbia. The cold-storage bills define cold storage to be any recepta- cle where for periods longer than ten days food products are kept at 40 F. and under. There is usually a time limit for most substances; this varies from nine to twelve months. The materials stored must have the dates of receipt and delivery by the warehouse stamped on them and no restorage is per- mitted in some States. No cold-storage goods with dates erased may be sold. When eggs and butter are stored they must be sold as refrigerated articles and signs should state this. This refers to eggs after thirty days. In some States there are fines for the first two offenses and fine and imprison- ment for the third offense. An important feature covered by U. S. Senate Bill 136 was the requirement that no food could be placed in cold storage unless in a sanitary condition. The condition when received and previous history of an article to be stored is as important as the storage. The Senate bill prohibits the manipulation of cold storage goods to resemble fresh goods and frozen articles must be sold in that condition. An investigation by the U. S. Department of Agriculture showed that in three months the various percentages of stored COLD STORAGE 219 goods delivered from storage in certain warehouses expressed as a percentage of goods received at the beginning of the period were as follows: Beef 71.2% Mutton 28.8 Pork 95 . 2 Poultry. , 75 . 7 Butter 40 . 2 Eggs. . ..14-3 Fish 35.5 And in seven months the amounts used were : Beef 99 % Mutton 99 . 3 Pork 99 . 9 Poultry 96 . i Butter 88.4 Eggs 75.8 Fish 64 . 9 The average months of storage were as follows : ist Half Ye~r ad Half Year Months Months Beef 2.6 1.8 Mutton 4.8 3.0 Pork 0.8 i.o Poultry 2.6 2.4 Butter 4.5 4- Eggs 6.1 1.7 Fish 6.8 6.7 This investigation shows that goods do not remain in storage for a long time. The goods stored are handled in special ways and these will now be discussed together with certain data to be used in designing cold-storage warehouses. 220 ELEMENTS OF REFRIGERATION Eggs. It has been stated that of the 3 billion dozen eggs produced in the United States yearly, 240 million dozen, or one-twelfth, are put into cold storage. Eggs are usually placed in cases containing 30 doz. These cases weigh about 50 to 55 Ibs. and are usually stored in tiers five or six high with slats between cases to give a chance for air circulation and the removal of heat. These cases are 12X13X25 ins. and occupy 2\ cu.ft. of space. The eggs lose weight on storage, about 7% being lost in five or six months. If the air in the storeroom is too dry there is considerable loss of weight, while damp air will cause a fungous growth on the eggs. In many cold-storage warehouses there is no forced circulation, the ice on the pipes keeping the air a proper humidity. Should the air become too moist it may be dried by putting calcium chloride trays on top of the refrigerating coils and draining off the solution formed. This salt may be regained by evaporat- ing the water. 80% relative humidity has been found to give good results. The eggs are held at 30 or 31 F. and as they absorb odors they should be placed in rooms containing eggs only. They are placed in storage in April, May and June and are usually kept for about nine months. They have been kept for twenty- three months and except for a shrinkage of 25% they were not affected by storage. The cost of this storage is 10 cents per case for the first month and 7^ cents for subsequent months; 40 to 45 cents would be the charge for the season. At 20 cents per dozen for the original eggs the item of 30 cents for the case, 30 cents for freight, 40 cents for storage, 25 cents for interest and insurance, and 40 cents for buying, packing and grading makes the price per dozen 25.5 cents, leaving about 5 to 10 cents per dozen margin for the owner, wholesaler and retailer. January is considered the end of the season. The eggs should not be washed when put in storage, as this spoils the appearance. At times they are candled before storage, although this is not done regularly. Candling consists of holding an egg in front of an opening in a metal screen, Fig. 114, within which is an electric light (originally a candle), If the egg is not good COLD STORAGE 221 a dark center due to the thickening of the yolk will be noted. A good egg will appear practically uniform in texture, the light shining through the egg. Candlers become very expert and this work is done rapidly. Candling is often done when eggs are taken from cold storage. Good cracked eggs are broken open and the meat placed in cans holding about 50 Ibs., which are sealed and frozen. These are used by bakers. It is neces- sary to use these soon after thawing. Uncracked eggs are broken and canned to reduce the cost FIG. 114. Candling Box. of shipment. In Sedalia, Mo., a large plant is installed for cracking eggs. Here lof millions of eggs are cracked during a season under highly sanitary conditions to prevent con- tamination of the egg meat. The eggs are broken on a knife and the whites are separated from the yolks, the latter being well mixed before sealing the can. This holds 30 Ibs. The canned cracked eggs are frozen and shipped to bakers for consumption. It happens that the output of this plant is used by one baker alone. The shipment of eggs from China is increasing. The U. S. 222 ELEMENTS OF REFRIGERATION Commerce reports from Shanghai, China, state that the ship- ment of eggs amounts to 800 to 1000 tons per month, i ton being 40 cu.ft. This is about 400,000 doz. per month. The storerooms for eggs and for all other storage should be kept clean and should be whitewashed about once a year. The whitewash used to sweeten rooms can be made with a bushel of lime slaked in boiling water with a peck of salt and enough water to make a thin paste. To each i2-qt. pail of this add a handful of Portland cement and a teaspoonful of ultramarine blue to overcome, a yellow discoloration. To prevent dust on concrete floors, a solution of one part sodium silicate (water glass) of 40 Beaume and three to four parts of water has been applied to a dry floor after washing. Butter. This is held at 33 F., or it maybe frozen at a temperature of 15. It is considered that it loses flavor with time of storage, although instances are given where the buyer has not questioned the flavor of butter held for two years. It is better to store it in bulk than in small packages. The ordinary butter tub weighs 50 to 60 Ibs. and occupies about 2 cu.ft. -The tub must be sweet and clean and carefully closed. It is sometimes paraffined on the inside and sometimes lined with parchment paper. If the air is damp mould will form on the parchment. Butter will absorb odors and for that reason it should be placed alone in a room. The amount in storage in the United States in 1909 probably amounted to 100,000,000 Ibs., while the total production of the country is about eighteen times this amount. The temperature does not seem to help in preserving the flavor. On judging cold storage butter there was little differ- ence in the total points of butter at 10 F. and 10 F., but butter at 10 F. was much better than butter at 32 F. It depends on the kind of butter to a large extent. According to Gray, high salt content and hermetical sealing are not advantageous in preserving flavor. A common method of storage is to chill the butter at first to o F. and then allow the temperature to rise to 16 or 20. Oleomargarine and such products may be held at about 20 F. COLD STORAGE 223 The temperature carried is a question of economy; the cost of refrigeration is placed against the saving in value of flavor. The limit of time of storage is about eleven months. The house should be sweetened with whitewash and a wash- ing of roVo bichloride of mercury in water once a year. A mixture of ice and salt is sometimes used for the cooling of these rooms. Cooper reports a butter-freezing room in Kentucky where 1700 cu.it. is held at ioj F. during August by the use of 507 Ibs. of ice and 109 Ibs. of salt per day. The egg room of 3560 cu.ft. is held at 30 F. by 790 Ibs. of ice and 132 Ibs. of salt. At this place such a method was considered best with ice at $2.50 per ton and salt at $7.00 per ton. Cheese. Cheese weighs 60 Ibs. to the box and occupies about 2 cu.ft. It is stored at about 32 F., although 36 to 40 is used. The U. S. Government tests were made at 31 to 32 F. Until it is thoroughly ripened this storage improves the cheese. Beyond that time it is not improved. The cold storage will check ripening and so keep the cheese. It is really to con- trol the ripening that refrigeration is used. To prevent loss of weight it is customary to coat the cheese with paraffin. It should not be frozen. Meat. Meat is improved by exposure to cold for a short time if kept at 25 to 28 F., but after about three weeks it gradually loses its flavor, although the meat is preserved. The fresh meat from the slaughter-house is placed in chilling rooms and it is cooled to the temperature of the main storehouse. In this way the chill room is equipped with excessive coil- cooling surface so as to remove the heat at the proper rate. Siebel states that 80 B.t.u. of refrigeration per twenty-four hours is required for every cubic foot of chill room. He states that i ft. of 2 -in. direct-expansion pipe or 2 ft. of 2 -in. brine pipe will care for 14 cu.ft. of chill room. If the meat is to be frozen for storage it is placed in a room at 10 F. and an allowance of 200 B.t.u. per twenty-four hours per cubic foot is made by Siebel and one-half the previous allowance per foot of pipe is used. This freezing is resorted to for shipment and for storage. This partially destroys the flavor. If thawed 224 ELEMENTS OF REFRIGERATION slowly the flavor is not lost. The freezing should be done slowly and meat should not be stored in such large piles that the heat cannot be removed from the center. It should be held so that heat may be taken from all parts. If this is too rapid, the outer layer freezes before the inner part, and this leads to certain decay at the center of the meat. The amount of refrigeration may be computed from the specific heats and heats of fusion given in Chapter V^when the weights are known. The weight will vary, but the following averages may be used: Beef (two halves) 750 Ibs. Calves 90 Sheep 75 Hogs 250 The time of cold storage of meat may be at least six months if there is no chance of thawing. Poultry. The storage of poultry has been a practice for some years. The poultry is frozen and kept in this condition. Dr. M. E. Pennington has investigated the matter of storage and care of poultry for shipment for the U. S. Government. She points out that the preparation of the fowl for storage is as important as storage itself. The chickens should be starved for twenty-four hours before killing to remove the putrid matter in the intestines, then the blood should be removed from the tissues after killing and the picking should be done without breaking the skin. This should be done dry and not after scalding the carcass. The carcass and especially the feet should be cleaned and prompt storage after chilling should be resorted to. With care of this kind the poultry is good after three weeks even if not frozen. The chill room is held at from 33 to 38 and the packing at from 30 to 32. Certain State laws allow ten months storage of poultry. This is accomplished by freezing. In all cases the entrails are undrawn from the carcass. The poultry is usually placed in small boxes or barrels. The packages should be small so that air can reach all parts. The boxes should not be piled until after the poultry is frozen. COLD STORAGE 225 Milk. Milk, if free from the germs of fermentation, will keep indefinitely, but this condition is difficult to attain, and for that reason the growth of the germs is prevented by lowering the tem- perature. Of course the pasteurizing of the milk by warming it to a temperature of 180 F. will kill the bacteria and not scorch the milk. This is followed by rapid cooling. Milk should be cooled as soon as possible after being drawn from the cow. The temperature at which it is held is about 40 F., for if frozen there is a formation or separation of flocculent par- ticles of albumen or casein compounds which do not redissolve readily on thawing. Fat globules or lumps are formed also. The cooling of the milk is accomplished in special block-tin coolers arranged so that they may be thoroughly cleaned. The milk passes over the outside and the refrigerant on the inside. One of these coolers is shown in Fig. 115. The Creamery Package Co. allows 20 sq.ft. of surface in these coolers per 1000 Ibs. of cream or milk per hour, making the cooler of ij or 2 -in. copper or steel tubes, tinned on the outside. The trough at top or bottom is made of tinned copper. Other coolers are made with a hollow screw, which rotates in the ripen- ing box, while the screw is furnished with a cooling solution. By having a hot supply in the screw the box acts as a pasteur- izer and on following this with a cool solution the milk is cooled and made uniform by the turning of the screw. Cream. In the storage of cream a low temperature is necessarily combined with clean storage vessels. This cream is used largely for butter-making and in many of the eight thou- sand creameries of the United States refrigeration is not employed, resulting in a poorer quality of butter, as cream is often held for some time by farmers before shipment to the creamery is made. The separation of the cream is carried on by the de Laval separator at the dairy or creamery and this may be done best at about 160 F. The cream after being cooled to 50 is stored and finally allowed to ripen at 70 F. Fish. Fish is usually frozen and coated with ice before ship- ment and storage. This method is highly developed in the Northwest, 1000 carloads of halibut being shipped yearly from 226 ELEMENTS OF REFRIGERATION 03 til FlG. 115. Spiral Coil, Disc Coil and Tubular Cooler of Creamery Package Co. COLD STORAGE 227 Vancouver. The fish are decapitated, cleaned, washed and placed in sharp freezers, the refrigerating coils acting as shelves. Certain of these rooms are equipped with two sets of eight shelves made up of i-in. extra heavy pipe 37 ft. long. These pipes are supplied with liquid ammonia for direct-expansion, and by keeping liquid in each of them the system is flooded. Here the fish remain for a day at 10 to 24 F. below zero and they are glazed with ice after freezing by dipping them in water. This ice retains the fish oil and keeps the flavor. After this operation they are wrapped in parchment paper and boxed for shipment at 10 F. Oysters are held in cold storage at 35 F. for some time. After opening, the oysters may be placed in a bucket and frozen solid. This is not advisable. Fruit. Fruits of all kinds are kept in cold storage, but the time in certain cases should not be long, since some of them lose flavor. Apples are usually stored in z\ bu. barrels weighing about 150 Ibs. and occupying 5 cu.ft. of space. They are usually held at 30 to 35 F. for winter apples while the softer summer apples are held about 5 above these. In England 29 to 30 F. has been used. Apples seem to improve on cold storage; there is a transformation of some of the starch into sugar. Apples have been kept for months and even as long as two years. Care must be exercised in picking and packing. If carefully picked they keep for a considerable time. The ship- ment abroad is very extensive and the loss on cold storage apples is very slight, amounting to from about 25 cents to some- thing over a dollar per barrel. This business in 1910 amounted to over nine hundred thousand barrels, valued at mere than two million dollars. Pears aie improved by storage in a way similar to that for apples, but they are not usually kept so long. The temperature is about the same as that for apples or a little higher 30 to 36 F. These are usually placed in boxes of 40 Ibs. weight when full and are picked in an under-ripe condition. Bushel crates are sometimes used. Closed barrels are not advisable, as the heat 228 ELEMENTS OF REFRIGERATION cannot be removed from the center fast enough. Wrappers of paper are advisable to protect the fruit from bruises and to keep the color bright. Peaches are kept for a few weeks only and are placed in boxes or crates weighing about 20 Ibs. They lose flavor if held long. The storage is for the purpose of transportation and to lengthen the season for selling. They are held at from 32 to 36 F. In shipping and storing these the boxes are placed on top of each other about five boxes high, and the fruit should be cooled slowly and warmed slowly to prevent sweating. The fruit should be carefully picked and at times it is stored slightly under-ripe. Strawberries lose their flavor on storage and they are kept for only a short time. They are held at 40 F. to prevent ripening. Experiments have been made which show that these and other berries may be kept for four weeks. Huckleberries have been held at 20 F. for pie making. Plums may be kept for several weeks at 34 F. if firm and sound. Grapes. These may be shipped from the West with success. They are held at various temperatures. Some require 32 F. while with others 34 to 36 is used. They should be dry when stored. They may be held from one to two months. Seventy days have been recorded for storage in redwood sawdust. Oranges and lemons are important items in the commerce of California. This business amounted yearly in 1905 to over $25,000,000 or 30,000 car loads. These cars hold from 15,000 to 30,000 Ibs. of fruit. The matter of storage has received close attention froir. the government as well as from private parties. Oranges are picked at convenient times from February to May and are usually shipped in crates 15X15X30 ins., weighing about 70 Ibs. These are placed on end in storage and usually in two layers. The fruit must be carefully picked, as bruised fruit decays. They should be held in shipment at 32 to 50 F., and on account of the improper care the loss in shipment has amounted to over one million dollars per season. At 32 F. they may be stored three weeks to a month, but oranges are COLD STORAGE 229 uncertain for this time. At times the storage is extended to three months. They give off large amounts of gas and require ventilation and if the air is too dry shrinkage occurs. Melons may be held for several weeks at 35 F. They must be carefully picked and selected for long storage. Usually the storage is for a short period. Bananas are usually picked green and are allowed to ripen gradually, the amount of ventilation determining the speed of ripening. At 34 they may be stored for some time, while at 40 they gradually ripen. At 32 they are apt to turn black. Vegetables. Potatoes are held at 35 F. in bags or barrels and should be so stacked that air may reach them. This must not be dry air. Potatoes are figured at 60 Ibs. to the bushel. If in barrels there will be 5 cu.ft. to about 2\ bushels. The room should be dark. Tomatoes, if picked when just starting to redden, may be kept for two months. They are usually crated after wrapping in tissue paper. They are held at 40. Onions are stored at about 34 for six months. These give out an odor and should be kept in a special room. They are placed in bags or barrels. Celery is held in crates of about 140 Ibs. These crates are about 24X24X30 ins. Celery is held at about 34 F. for three or four months. The seasons for production in different parts of the United States make it possible to get this at all times of the year. Cabbages are held at 35 F. These are stored in barrels or crates. Air circulation is necessary. Tobacco and cigars are held at 40 to 45 F. and will retain their flavor if kept in one condition. This low temperature prevents the development of insect life. Furs, Rugs and Clothing. The matter of the cold storage of goods subject to moths and other insects received attention during the last decade of the nineteenth century. In a paper by Dr. L. O. Howard it was stated that insects caused a loss in cereals of one hundred million dollars per year, and Mr. A. M. Reed conceived the idea of preventing a similar loss from insects 230 ELEMENTS OF REFRIGERATION acting on furs and woolen goods and experimented on the eggs of the moth and buffalo beetle and found that 50 or 55 F. was sufficient to prevent the hatching and 40 prevented the a a a a Temporary Storage Office Elevator a a a a Receiving Room Platform. Upper Floors Eirat Floor Section FIG. 1 1 6. Small Store House. passing from the larval state. The miller and the beetle were killed at 32 F. and in the center of rugs they were killed in several weeks at temperatures of 32 to 40 F. This led to the establishment of cold storage for such articles held at 32. COLD STORAGE 231 Florists hold lily of the valley pips, lily bulbs, feins, smilax and other plants or bulbs for months at low temperature. They also use the cold-storage room to control the growth of plants. The construction of cold-storage warehouses will vary with the peculiarities of the designer and the requirements of the ground selected for the plant. In general there is a receiv- ing room near a railroad track and a truck platform as well, close to the office for the receipt and delivery of goods. In some cases there is only a railroad platform, as goods are handled Upper Floors 1st Floor 2"Cork Cork 2 Brick 24 <- > ,12"Brick 2 "Cork 2"Cork <-24" Brick Cork 2' 2"Cork \ ^n levator > ^^ / J!3 \ / ( Receiving Platform j FIG. 117. Plan of Large Store House. each way in carload lots. The receiving room is sufficiently large to hold several transhipping hand trucks and is connected by elevators to the various floors. In small houses the elevator shaft could pass through the center of the house opening into four rooms placed around it on each floor. The separate rooms are required to give the necessary number of rooms for the differing foodstuffs to be stored. This plan is shown in Fig. 1 1 6. In this way the elevator serves the four rooms. The attic under the roof is used for the condensers and storage and also serves as a heat insulator. The cork insulation on outside walls, certain inner walls, ceiling of first floor and oi> the upper ceiling is shown by heavy lines. 232 ELEMENTS OF REFRIGERATION For extensive plants, as those built in cities, the rooms may be larger and extend over the complete space of one floor. hr luster Finish \ Gutter 1 4 Solid Cork Partition Walls PlasteredVinside and out v * \ V \ v rCement\Top finiehV \^_ N v ^ 2"Concre\e x I" Cork Board Concrete Floor LI Construction 1...I Double Pipe |..r~ll fai Ammonia Condenser//^ 1 | FIG. 118. Arctic Cooling Plant for Store. Such a plant is shown in Fig. 117. The elevators in this plan serve two houses or two rooms of one house. A small storage room for a market is shown in Fig. 118 in which the various COLD STORAGE 233 details may be seen easily. The use of a brine tank or con- gealer makes it possible to shut down the machine at night after freezing the brine, this frozen brine furnishing the re- frigeration during that time. The various parts of the plant may be traced out. The congealer, Fig. 119, for wall coils, is sometimes used in larger rooms. Figs. 120, 121 and 122 show the arrangement of pipes, insu- lation room and machinery for small plants. In Figs. 118 and 122 the air circulation may be followed. Oil Charging COLD STORAGE 235 236 ELEMENTS OF REFRIGERATION The various arrangements of piping are shown in Fig. 123. In Fig. Aj the coil is carried on the ceiling while in B it is carried on the walls. When the coils are carried on the ceil- ing, moisture is likely to drop from the pipes on the goods below/ and then the ceiling coils are placed over aisles or else they are placed in lofts as in D, E and F. In these lofts the FIG. 122. Small Store House of Remington Machine Co. floor is placed under the pipes to catch the drip and take it to a gutter, but there is an open space at the center to allow the cold air to fall, while side partitions near the center or at the sides near the walls aid in circulation of air. The wall coils are better in most cases, although there is danger of cooling the goods near the coils too much. In Figs. C and E there are brine tanks or congealers used in the rooms and the cool- ing of this large amount of brine to a low temperature or the COLD STORAGE 237 freezing of the brine permits the compressor to be shut down. Figs. A, B and D may be used with brine or direct expansion E F FIG. 123. Arrangement of Piping as Shown by Creamery Package Co. of ammonia. C and E are for direct expansion. For inter- mittent operation when brine is to be circulated, Fig. F is employed, the tank supplying the refrigeration on shutting 238 ELEMENTS OF REFRIGERATION down the plant. Such an arrangement is used when ammonia piping is objectionable. In constructing the elevator and well the elevator car has a ceiling a? well as a floor and these are made as air tight as possible, so that when the refrigerator door at any floor is open there is no danger of air circulation from the warmer air out- side. The floor and ceiling of the car have rubber or felt filling FIG. 124. Elevator. strips, closing off the air space so that the heat loss on opening the door is a minimum. Fig. 124 shows this. Fig. 125 gives a section through a storehouse for meats while Fig. 126 illustrates a section of a ship containing refriger- ated space. The arrangement of the cooling coils for cir- culation and drip is to be noted as well as the air loft under the roof as in Fig. 116. The number of rooms used in hotels varies with the hotel. COLD STORAGE 239 240 ELEMENTS OF REFRIGERATION COLD STORAGE 241 Thus in the Blackstone Hotel of Chicago the following cold- storage rooms are found: Basement. Vegetable box n' s"Xio' J'Xf Fruit box 13' g"X 10' 3"X7' Meat box 14' 4"X8' V'X?' Bouillon box 7' 2"X8' 4 /7 X7' Game box 5' 6"X8' 4 "X7' Egg box 4' 6"X4' 2"X7' Butter box Milk box Cheese box Oyster box Fish box Fine wines box . . . 4 '6"X3'2"X7' ....9'Xs'2"X7' -5'4"X3'3"X7' i 2 'o"X6'8"X7' ....6'X6'8"X7' . .7' 9 "X4'7"X7' Ice-cream box 10' o"X 10' o"X 10' Sharp freezer box, 5' o"X 10' o"X 10' o" Draft beer box 9' o"X9' o"X6' Banquet Hall. Refrigerator i4'X4'X9' Kitchen. Poultry box s'Xs'Xs' I0 ' Fish box 9'X3'X3 r 10' Lobster box 5'X3'X3' 10" Bouillon box 2' 8"X 2' 8"X 2' 10" Cold plate box i3 / X3 / 4 // X3 / i" Cold plate box ii / 3 // X4 / X3 / 10" Cold meat box VX4 / X9 / Sandwich box 6'X3'X9' General kitchen 9 'Xi3'X9' Oyster box i6'X4 / X9 / Pantry. 6'X6'X9' Freezers for ices 6'X3 / X7 / Fruit and salad box 5'X3'X9' Milk box 4 / X3 / X3 / Baker's box S'XS'XS' Icecream n' 6"X3' 6"X3 / Short order s'Xs' 4"Xs' 10" Cook's box i6'X4 / X9 / In addition to the above there are some boxes on the dining- room floor and the club floor. To do this work and to cool the dining rooms and certain places as well as to make some ice requires a 5o-ton machine and a 7 5 -ton machine. In Fig. 127 a direct expansion CO2 plant for a brewery is shown. Each storehouse is cooled by large direct-expansion coils. In the air loft above the fermenting tanks is noted a sweet-water cooler. The water which is cooled in this tank is passed through coils in the fermenting vats to remove the heat of fermentation and control this process. The large vats are used for proper aging before storage in the chip casks on the lower floor. The path of the gas from the two compres- sors through the condenser and piping and the construction of the walls should be examined. The refrigeration for storage of food may be done with natural ice and salt as was mentioned in Chapter II. In Minnesota a wholesale and retail market refrigerates 40,000 cu.ft. of space with 553 tons of ice at $1.65 per ton and 67 tons of salt at $7.00 per ton, holding the room at 15 F. 242 ELEMENTS OF REFRIGERATION COLD STORAGE The walls of these houses and the floors are constructed in various ways. Thus at the Boston Terminal Refrigerating Co. plant, a building 156 by 100 ft. with seven floors and a ventilating loft, the walls were made of 4-in. vitrified water- proof brick, 8 ins. of hollow tile and two 2 -in. thicknesses of Nonpareil cork held in place by asphalt cement. This wall does not carry any of the floor load. The building is of reinforced concrete and the only floors insulated for heat are the base- ment floor, third floor, and eighth floor. These floors are insulated with two thicknesses of 2 in. or 2- and 3-in. thick- nesses of cork board with an asphalt wearing surface. This construction forms a fireproof building. A suggestion has been made to use two 4-in. tiles with a third tile 8-ins. from the outer ones with a cork filling between the outer wall for a fireproof building. This wall carries no weight. The columns carrying the weight are of reinforced concrete. In this system the par- titions are made of two 4-in. tiles with a 6- or 8-in. cork fill. The floors are of 6 ins. reinforced concrete, 2 or 4 ins. of cork and asphalt on top. The doors are covered with iron. In an apple-storage warehouse the walls were made of 2X6 hemlock boards laid flat, as are used in grain elevators, and faced on one side with 4 ins. of brick. Fig. 128. Such a construction should give good results. The installation cares for 15 cu.ft. of space with i lin.ft. of 2 ins. direct expansion. In large plants the insulation is such that the heat loss is 1.8 B.t.u. to 0.6 B.t.u. per square foot per hour or for values of K of 0.03 to o.oi. FIG. 128. Grain Bin Construc- tion for Apple Storage. Any of the forms of Chapter VI may be used for the insula- tion and for any form of construction the value of K may be computed as shown. 244 ELEMENTS OF REFRIGERATION Partitions between rooms may be made of two 2-in. cork boards faced with 4-in. tile or with cement plaster. The temperature of the rooms should receive consider- able thought in determining what should be used. The highest possible temperature for good storage should be used. Some storage men claim that zero rooms cost from 50 to 75% more to operate than rooms at 30 F. The proper selection may make a success from what has been a failure. The table on p. 215 gives the temperatures required for different articles. After the temperature is fixed, the amount of insulation should be figured so as to make the annual expense a minimum. The annual expense is made up of interest, depreciation, taxes, insurance on insulation, value of space occupied and insurance on the stored materials and the cost of absorbing the heat leaking through the insulation. If the thickness is increased and the kind of insulation improved, the first items will increase, but the cost of absorption will be decreased and if the sum of these is decreased then the improvement pays. If the sum is increased a poorer insulation would give better results, the increase due to the cost of insulation not making up for the saving in refrigeration. By plotting these costs for different thicknesses the best thickness may be found. In estimating these items the charge in insurance due to various constructions must be considered. Thus in frame buildings, according to J. H. Stone, the insurance is i% while in fireproof buildings it is only J% and ^% for semi-fireproof buildings. This refers to goods as well as buildings and this should be considered in fixing the cost. The depreciation on insulation is taken by him at 4% in good construction and at 8% in wooden buildings. The cost of insulating material is given by Stone as 27 cents per square foot for 2 B.t.u. per square foot per twenty-four hours per degree difference. The cooling is accomplished by coils or by air circulation. The coils, as shown in Fig. 123, are either brine coils or direct- expansion coils. In some plants brine is thought to be neces- sary. In present-day work especially with welded pipes ammonia is safe and is used. COLD STORAGE 245 The direct-expansion system requires less difference in pres- sure between suction and discharge main, giving a more efficient plant. The brine system, however, in addition to the question- able advantage of safety in case of rupture does possess certain 00000 00000 O O O~/P E F FIG. 129. Arrangements of Direct and Indirect Refrigeration. advantages. If a large amount of brine is cooled during the day this may be used when the compressor is shut down and, more- over, the cost of the expensive ammonia to fill the system is eliminated. To increase the storage capacity it is even pos- sible to freeze the brine, removing about 150 B.t.u. per pound 246 ELEMENTS OF REFRIGERATION of brine. These advantages are worthy of consideration, although the lower back pressure on the compressor when brine is used to care for the double transfer of heat makes the advisability of its use a matter hard to determine. The coils, of whatever kind they may be, are best placed on the side walls near the ceiling, as ceiling coils are apt to collect and drop moisture. If the room is over 25 ft. wide a ceiling coil must be used in addition to the side coils. This should be placed over aisles. There should be ample coil surface. Of course it is necessary to keep certain goods at the proper dis- tance from side coils to prevent freezing. The use of cross aisles and the arrangement of goods in tiers to aid in circu- lation of the air of the room are advisable. The cross-sections of rooms are shown in Fig. 129 in which the circulation is indicated. The use of the aisles to separate goods of differ- ent owners is advisable. The use of partitions of tin around the pipes to catch drip and to cause a definite current is shown in E and F. The air for the storage room should be cleaned and dried before allowing it to enter. Ventilation should be accomplished by the air of the room rather than by outside dirty air. In many storehouses such as the 4,300,000 cu.ft. house of the Merchants' Refrigerating Co. of Jersey City, there is no circula- tion provided. The circulation is all brought about by large pipe coils placed over the aisles and not at one place. In the indirect system of cooling by air circulation air is cooled and blown into the room. The coils may be placed in ducts in ceiling or as is generally the case they may be placed in a large space called a bunker room and the air blown across these is carried to ducts and flues leading to the various floors. The distribution of air in the storage room is difficult. In some cases it is distributed through numerous small holes in the ceiling and the warmed air is removed through holes in the floor. In this way an even distribution over the whole room is obtained, although other methods are used. The air may be recirculated if there are no odors. This is one of the objections to the indirect system. Smoke or odors from COLD STORAGE 247 one rooin may contaminate the stored goods in another. 129 illustrates warehouse rooms using forced-air systems. The bunker room is shown in Fig. 130. In this, brine or a volatile liquid is passed through the coils and abstracts heat from the air, which is blown across the pipes. The moisture Dehydrator FIG. 130. Bunker Room. Fan removed from the air freezes on the outside of the pipes, but by circulating brine occasionally over the pipes this frost is removed or warm brine may be turned in when the air is shut off. In some houses the radiation surface is increased by the FIG. 131. Radiation Discs. use of split discs added to the outside of direct-expansion pipes, Fig. 131. These are not used often at present although in former times they were used extensively 4 The air is driven by a fan blower. Forms of blowers arc shown in Fig. 132. The size of the fan and the power to drive the fan are fixed alter the sizes of ducts 248 ELEMENTS OF REFRIGERATION have been computed. The duct sizes are fixed by the allow- able velocities of the air. The velocities to be used are as follows : Main ducts 1200 ft. per min. = 20 ft. per sec. Branch ducts 800 " =13 " Register faces 300 = 5 Buffalo Planoidal Fan. Sturtevant Multivane. American Sirocco. FIG. 132. Fan Blowers. The quantity of air is fixed by finding the quantity of heat to be removed and the allowable rise in temperature m the air. If Q is the heat entering the room per hour, t r is the temperature of the room and fo is a temperature to which the COLD STORAGE 249 air can be cooled in the bunker room, the volume of air per hour V is given by = Mv= , t t ) V = cubic feet of air per hour ; Q = heat removed per hour in B.t.u. figured from methods of Chapter V; U = temperature at outlet from bunker in deg. F. ; t r = temperature of room in deg. F.; v = volume of i Ib. of air = 12 cu.ft. approximately. If w equals the velocity in feet per second in the duct or register the area F in square feet is given by . 3600^ (2) The sizes of the ducts are found and then the hydraulic radius of each duct is computed. This is equal to the cross- section of the duct divided by the perimeter. If b and d are the dimensions of the duct in feet and RI is the hydraulic radius in feet the following are true: -A- (4) The friction loss in pressure along a straight pipe of L ft. length is given in feet of air pressure by .. . .... . . . (5) For bends of radius equal to 2.6, the loss is 250 ELEMENTS OF REFRIGERATION In grills the loss is given by At gradual changes of section there is no loss. For loss in the bunkers with staggered cooling coils the loss of head may be taken as for each coil or line of pipe over which the air must travel. If now in any line the sum of the various losses is taken, the total loss may be found. This is the static pressure to be produced by the fan and in some fans this may be taken as w 2 about three times the velocity pressure, . The sum of these 2 two pressures is called the dynamic pressure, and the ratio of this to the static pressure is usually given in catalogs of fan makers. The static pressure varies from 70 to 90% of the dynamic pressure in various forms. The dynamic pressure is the one listed in most catalogs. Having the dynamic pressure in feet of air found by dividing the static pressure by 0.75, this may be changed to ounces per square inch by dividing by 1 20 for air at 70 or by no for air at 20 F. If pressure in inches of water is desired this pressure in ounces per square inch is multiplied by 1.73. The data for three types of fan are given in the table on p. 251 for the points of best efficiency: From this table the fan must be picked out to deliver the desired volume, at a given dynamic pressure. Since in general the pressure is not a tabular pressure, the equivalent volume must be found for a tabular pressure. When a fan is run at the same point of its efficiency curve, the pressure varies as the square of the velocity or as the square of the number of revolutions; the quantity of discharge varies as the velocity or number of revolutions and the power which COLD STORAGE 251 FAN DATA SIROCCO FAN. Velocity Press. =0.288 Dyn. Press. BUFFALO CONOIDAL FAN. Velocity Press. =0.225 Dyn. Press. STURTEVANT MULTIVANE FAN. Velocity Press. =0.10 Dyn. Press. a a Diam. of Fan Wheel. Dynamic Press. a 1 30 Dynamic Press. S as Dynamic Press. ioz. I OZ. ioz. 2 OZ. ioz. I OZ. 00 3 Cu.ft. R.P.M. B.H.P. 38 2,290 0.005 77 4-580 0.037 Cu. ft. R.P.M. B.H.P. 1,720 632 0.39 3,435 1,255 3. ii 3 Cu.ft. R.P.M. B.H.P. 1,000 502 0.12 2,000 1,003 I.O 4i Cu.ft. R.P.M. B.H.P. 87 15,24 O.OII 175 4,58o 0.084 35 Cu.ft. R.P.M. B.H.P. 2,340 545 0.53 4.675 1,085 4-23 4 Cu.ft. R.P.M. B.H.P. 1,448 4 l8 o. 19 2,895 835 i.S 6 Cu.ft. R.P.M. B.H.P. 155 1,145 o. 018 310 2,290 0.147 40 Cu.ft. R.P.M. B.H.P. 3,060 482 0.69 6,100 960 5-52 5 Cu.ft. R.P.M. B.H.P. 1.950 359 0.25 3.900 717 2.0 it 3 9 Cu.ft. R.P.M. B.H.P. 350 762 0.042 700 1,524 0.333 45 50 Cu.ft. R.P.M. B.H.P. 3,890 422 0.88 7.760 845 7-03 6 7 Cu.ft. R.P.M. B.H.P. 2,565 314 0.33 5.130 62 7 2.6 12 Cu.ft. R.P.M. B.H.P. 625 572 0.074 1,250 1,145 0.588 Cu.ft. R.P.M. B.H.P. 4,78o 378 1.09 9,560 753 8.67 Cu.ft. R.P.M. B.H.P. 4,000 251 o.S 8,000 501 4.0 3 4 18 Cu.ft. R.P.M. B.H.P. 1,410 381 0.^67 2,820 762 i % 33 60 70 90 Cu.ft. R.P.M. B.H.P. 6,875 3i8 1.55 13.650 636 12.38 8 9 10 Cu.ft. R.P.M. B.H.P. 5,8oo 218 0.72 1 1, 600 435 5-8 24 Cu.ft. R.P.M. B.H.P. 2,500 286 0.296 5,000 572 2.35 Cu.ft R.P.M. B.H.P. 9,450 272 2.14 18,750 542 17.00 Cu.ft. R.P.M. B.H.P. 7,850 1 80 0.99 15,700 359 7-9 3 30 Cu.ft. R.P.M. B.H.P. 3,910 228 0.460 7,820 456 3-68 Cu.ft. R.P.M. B.H.P. I5,6oo 2IO 3-54 31,200 419 28.3 Cu.ft. R.P.M. B.H.P. 10,300 157 I 25 20,600 314 10. 6 g 36 Cu.ft. R.P.M. B.H.P. 5,650 190 0.655 11,300 381 5-30 no 130 Cu.ft. R.P.M. B.H.P. 23,100 172 5.24 45,700 343 41.4 ii Cu.ft. R.P.M. B.H.P. 12,925 139 1.64 25,850 278 13.1 48 Cu.ft. R.P.M. B.H.P. 10,000 143 1.18 20,000 286 9-40 Cu.ft. RJ>.M. B.H.P. 32,400 146 7-34 64,700 291 58.6 12 Cu.ft. R.P.M. B.H.P. 16,000 126 2. O2 32,000 251 16.2 38,800 2.28 19.5 10 60 Cu.ft. R.P.M. B H.P. 15,650 114 1.84 31,300 228 14-7 150 Cu.ft. R.P.M. B.H.P. 43,ooo 127 9.80 86,000 253 78.0 13 Cu.ft. R.P.M. B.H.P. 19,400 11^ 2.44 72 Cu.ft. R.P.M. B.H.P. 22,600 95 2.66 45,200 190 21 . 170 Cu.ft. R.P.M. B.H.P. 55,500 112 12.55 110,000 235 88.8 I; Cu.ft. R.P.M. B.H.P. 23,200 105 2.94 46,400 209 23.5 14 8? Cu.ft. R.P.M. B.H.P. 30,800 81 3.6i 61,600 163 28.9 190 200 Cu.ft. R.P.M. B.H.P. 69,000 IOO 15.61 137,800 199 124.8 15 Cu.ft. R.P.M. B.H.P. 27,200 97 3-44 54,400 194 27-50 15 90 Cu.ft. R.P.M. B.H.P. 35,250 76 4.14 70,500 152 33-1 Cu.ft. R.P.M. B.H.P. 76,600 94 17-35 152,500 188 138.0 17 Cu.ft. R.P.M. B.H.P. 36,150 84 4-42 72,300 168 35-4 252 ELEMENTS OF REFRIGERATION varies as the product of quantity and pressure will vary as the cube of the number of revolutions. Hence A7 V V e V l ~ ~ XV V e = equivalent volume discharged at speed N e revolutions per minute ; V a actual volume discharged at speed N a \ N e = revolutions per minute to give total dynamic pressure N a = revolutions to give pressure P a \ P t = tabular pressure ; P a = actual pressure. Having V e the fan may be selected and then N a may be found to give the proper pressure and quantity. N '~ N JJF I - '" ( I0 ) The power to drive this fan is given by T7jL ^; () HP a = actual horse-power to drive fan; HP t = tabular horse-power to drive fan. If the relation between static pressure and velocity pres- sure is changed from that used, these values are changed, and although the tables may be used to get equivalent quantities, there is little use in giving the method of doing this, as the fan would then be working inefficiently. The fan and its power to be used are now known and the dimensions may be found in the tables on pp. 253 and 254. COLD STORAGE FIG. A. Fan Dimensions. DIMENSIONS OF SIROCCO FAN IN INCHES Size. A B C D E F G H I J K N o P 7 28 2Sl 40 42 36 3i* 27* 26^ 23* 28 44 8 20 3i* 8 32 28f 45* 48 40* 36 3i 2Q 25* 32 $c- 9 22 35* 9 36 3*1 Si! 54 45* 40 34* 34 3o| 36 56 9 24 40 10 40 36 57i 60 50^ 44* 38 37 33* 40 62 10 26 44 ii 44 39* 6 2 | 66 55 48 4i* 39* 36 44 68 10 28 48 12 48 43 68| 72 $9* 52* 45 45 4i| 48 74 II 3 52 13 52 46^ 74* 78 64* 57* 49* 48 44i 52 80 II 32 56 14 ,5 5oi 80 84 6g sri 5i 52 47! 56 86 12 34 56 15 60 54 8 5 f 90 73* 64* 54* 53 49* 60 9 2 12 36 60 DIMENSIONS OF BUFFALO CONOIDAL FAN IN INCHES Size. A B C D E F G H I K N P 30 II ioi 14! i6| i3f H 12* 12 9* i7l 3 7 isA 35 "i ia| *7i iQi is! 16 14* 13 io| 20 3 8 i7& 40 Hi 14 19! 22f i7i 18 16 14 nf 22| 3 8 i8tf 45 i6i isi 22f *5f 2ci 20 i7l i5i I2| 25f 4 9 20^ 50 i8| 17* 24* 28 22 22 19* i6i i3i 28^ 4 9 22^ 60 22 21 2 9 * 33! 26i 26 23 19* 16 34i 5 ii 26i 70 25* 24* 34* 39* 30* 30 26 22 18* 39! 6 12 30 80 2 9 * 28 39* 45i 34! 34* 29i Mi 2b| 45* 6 14 34! 90 33 3i* 44i Sof 38| 38* 32i 27i 22f 5i| 7 16 38i no 40| 38* 54 61! 47i 47 38! 32i 27* 62^ 8 20 46! 130 47! 45* 64 73* ss! 55 4Sf 37* 32i 73* 9 24 54 150 55 52* 73f M 64! 64 52| 43 37i 84! ii 28 63i 170 6 2 i 59* 83i 951 72! 72 Sl 49 42* 96 13 32 7ol 190 6 9 f 66$ 93* 107 81 82 66f 54 46| 107 IS 36 82* 200 73* 70 98* II2f 85i 86 69! 56* 48| II2f 16 38 8si 254 ELEMENTS OF REFRIGERATION DIMENSIONS OF STURTEVANT MULTIVANE FAN Size A B C D E F G H I J K M N o p 10 40 30* 45 52i 40! 37* 26* 36f 38! 32| 48i 32* 10} 20 66| ii 45 34* 50* 584 45* 41* 29* 39 42* 36f 54* 361 12 22 73* 12 49* 38* 56* 65l 5i* 46 33 43i 46i 4of 60* 40* 12 24 81* 13 54* 42 6ii 7if 55l 5i 36 46| 5i 44* 66* 44s id 28 8g* 14 59* 45f 67l 7f 6o| 55 39 49 f 54* 48f 72* 48} i*i 32 96 iS 64* 40s 73* 84! 6 5 ! 60 43 54l 59* 52f 78* 52* 14* 36 105 16 69* S3l 781 91* 70 64 45 58f 64^ 56! 85 56* I4| 42 112* i7 74* 57i 84i 97f 74f 68 48 62 69! 6o| 9i 60* i4i 48 I2Oj The amount of coil surface used in the rooms of a store- house should be figured by the usual formula: Q = amount of heat removed per hour in B.t.u.; F = area of surface square feet; K = constant of transmission B.t.u. per square foot per hour per degree; = 5 to 10 for brine or direct-expansion coils to air; f c = mean temperature of brine or ammonia, deg. F.; t r = temperature of room; / r -* c =iotoi5F. The quantity Q is fixed by the heat entering through the walls and the heat gained by lights, motors, persons and goods stored. The heat from the walls and other causes is computed by methods of Chapter V. Thejieat given up by articles is given by c = specific heat ; T a = temperature of articles before storing; TV = room temperature; //= latent heat of fusion; M = weight in pounds ; h = hours to cool and freeze. COLD STORAGE 255 Before computing this, h and T must be assumed for any substance, h is fixed by the designer, and the temperature of the room is given in Chapter V. The time h may be taken as from six to twenty-four hours. In all cases it is better to chill slowly. By adding the various heat quantities the total is found. On account of the ice formation over the pipe the value of K cannot be told exactly, and for that reason the usual method is to allow a number of cubic feet of space for each lineal foot 2-in. pipe for direct expansion or brine. In some cases i ft. of 2-in. brine pipe is allowed to 12 cu.ft. for room temperature of 30 F. while 6 cu.ft. only is used for temperatures of from 5 F. to 10 F. The following based on Levey's tables may be used for 2-in. pipe and direct expansion in rooms with good insula- tion, say 1.5 to 2 B.t.u. per square foot per twenty-four hours. Cu.ft. Per Foot of 2-in. Pipe. Room Small Rooms, Medium Rooms, Large Rooms. Limit of Length, Feet. Temp. 1000 Cu.ft. 5000 Cu.ft. 10,000 Cu.ft. Brine. Dir. Ex. Brine. Dir. Ex. Brine. Dir. Ex. Brine. Dir. Ex. O I I 2 2 3 3 IOO 2OOO IO 4 5 6 8 8 12 175 2OOO 20 6 8 IO 13 13 19 225 2000 30 8 ii 14 17 17 25 275 2OOO 36 10 14 16 2O 20 30 300 2000 The length of the brine coil is limited by the amount of brine which may be cooled and the velocity of the brine, while with direct expansion it is merely a matter of the ammonia which may pass through. The length of the pipes should change with various diameters, since the surface varies as the diameter, while the quantity of brine or ammonia varies as the square of the diameter. The brine coils, however, are not varied in length, as the diameter is changed while the direct expansion-coils vary as the diameter, a i-in. coil having 1000 ft. as its limit of length. The cubic feet of space cooled per foot of length will vary as the diameter of the pipe. 256 ELEMENTS OF REFRIGERATION The allowances made by Louis M. Schmidt are as follows: DIRECT-EXPANSION PIPING Freezing and brine tanks. ... 50 sq.ft. per ton of refrigeration. Brine coolers ............... 10 Freezing chambers .......... 350 sq.ft. per 1000 cu.ft. Storage rooms .............. 35 BRINE PIPING Freezing chambers .......... 500 sq.ft. per 1000 cu.ft. Storage rooms .............. 50 Bunker rooms ......... ..... 20 Skating rinks ............... 0.8 sq.ft. per sq.ft. of ice surface. These two sets of tables are practical rules for determining the amount of surface. The better method is to use the formulae of Chapter V and from them compute the heat lost and the pipe surface to care for the installation, using these tables as checks. E. H. Peterson in Ice and Refrigeration for November, 1915, gives curves showing data for refrigeration of rooms of storehouses. For "rooms at zero degrees his curve is to be given by the following equation: ~ , . , , , . ,. Cubic feet per ton of ref ngeration = 1000 /cu.ft. 1 5000, Increase this by 80% for 10 F., 150% for 20 F., 250% for 30 and 333% for 40. One ton will care for 3000 cu.ft. on an average, and noo sq.ft. of insulated surface. If it is desired to find F for the coil surface in a bunker, the quantity K will depend on the velocity of the air over the pipes. This is given by K = 2.2\/w (for wet pipes and wet vapor) K = i + 1 .3 V_w (for dry pipes and wet vapor) J w = velocity of air in feet per second; t r is then equal to the mean temperature of the air. COLD STORAGE 257 The necessary length of pipe is then found and arranged as in Fig. 130, which shows a bunker for air cooling. It has been found by Sibley that ice formation on the pipe does not cut down the heat transfer, but aids it. An "inch of ice in a brine tank coil serves to increase the transfer from a ij-in. pipe to about four times its previous value, while 2 ins. increases it twelve times. The ordinary allowance of 120 to 150 lin.ft. cf ij-in. pipe of expansion coil in a brine tank per ton of capacity is decreased by him to 40 ft. when ice is allowed to form on the pipes. For ice making this ordinary allow- ance is doubled to from 240 to 300 lin.ft. Sibley states that when ice can form around the expansion coils in the brine tank the rate of transfer is increased as stated above. The weight of ammonia per hour for a room or plant is given by ^=M a . . . ..... (15) ^l-^4 () = heat in B.t.u. per hour; M a = weight of ammonia per hour; i\ = heat content at expansion pressure leaving coils ; 24 = heat content leaving condenser. The lines carrying liquid ammonia should be of such a size that the velocity of the liquid is not over 4 ft. per second. The return lines should be such that the vapor returning is not moving faster than 50 to 100 ft. per second. These lines may be figured from drop in pressure using the steam formula: P= pressure drop in pounds per square inch in length L\ L length in feet; D= weight of i cu.ft.; d = diameter in inches ; M= weight in pounds per minute. From this a drop may be assumed and d found or with a given d, P may be found. 258 ELEMENTS OF REFRIGERATION Brine is formed by allowing water to flow over calcium chloride or sodium chloride. This is best done by having a box or tank into which the brine is pumped and allowed to flow over lumps of the chloride, and after dissolving some of the salt it is allowed to pass out through the bottom of the tank. The density of the brine is fixed by the temperature at which it. is desired to carry the brine. In most cases of closed brine systems it is necessary to keep the brine from freezing, although in congealing tanks it is desired, that the brine freeze. The densities and temperatures of freezing are given as follows : FREEZING TEMPERATURE OF SALT SOLUTIONS Density of cal- / Sp.gr 1.035 1 . 062 1.085 1 .113 I . 122 i -I3S 1-155 cium chloride 1 Deg. Beaum6 at 64. . S-o 8.6 ii. 4 14.7 15-9 17-9 19.7 Density of so- j Sp.gr 1. 022 1.044 i .067 1.091 I. 117 i . 142 1.168 dium chloride \ Deg. Beaume' at 64 ,. 3-0 6.0 9-0 12.0 15-2 18.0 20.9 Temperature of freezing, deg. 28 24 20 16 12 8 4 Density of cal- / Sp.gr i .165 1.174 I.I86 1. 197 I . 2O7 i .216 cium chloride 1 Deg. Beaume" at 64. . 20.7 21.7 23-0 24.1 25-2 26.1 Density of so- ( Sp.gr 1. 193 dium chloride \ Deg. Beaum6 at 64. . 23-5 Temperature of freezing, deg o -4 -8 12 -16 -20 The specific heat of brine varies with the density and the specific gravity. The latest data on this calcium chloride brine are given by Dickinson, Mueller, and George in the bulle- tins of the Bureau of Standards, U. S. Dept. of Interior, Vol. 6, No. 3, or Reprint No. 135. In this the specific heat of brine at c C. is given by = 2.8821 3.62729+1.779432; (17) 3 = specific heat in B.t.u. per pound per degree; D = specific gravity of solution at o C. compared with water at max. density. For changes in temperature from o C. the value of 8 is decreased approximately 0.0008 for each degree centigrade below o C. The specific heat of sodium chloride is taken as 0.78 for 1.2 sp.gr., 0.86 for i.i sp.gr., 0.94 for 1.05 and 0.98 for 1.02 COLD STORAGE 259 sp.gr. Having the amount of heat per hour required for a plant or room, the amount of brine required per hour is given by (18) Q = heat in B.t.u. per hour; M v = weight of brine per hour; 3m = mean specific heat at temp. - 2 to = temperature of brine at outlet = temp, of room 10 F.; ti = temperature of brine at inlet = fo 5 to 8. The length of pipe in one coil is such that this heat of the brine is given up in the length. Thus The kind of brine to use depends on the engineer. Some feel that calcium chloride will not corrode nor rust the iron as fast as the sodium chloride; neither should corrode the piping. On account of the impurities in the salt, brine may corrode the iron. If there is any acid in the brine, corrosion may occur. If there are dissimilar metals in the system, these will set up galvanic action and thus corrosion. Stray electric currents may also start corrosion. In the system there should be no brass pumps if the mains are of iron or steel. It is well to keep the brine alkaline by the addition of lime or dilute caustic soda. The calcium chloride permits of a lower temperature of brine for a given concentration and for that reason it may be employed. The brine is usually forced through the system by pumps of the direct-acting type, although centrifugal pumps are employed at times. The direct -acting pumps should be of such a displacement that they will deliver their full capacity in cubic feet at 45 cycles per minute. After the quantity of brine required per hour is obtained by (18), the size of pump is found and after this the pipes carry- 269 ELEMENTS OF REFRIGERATION j ing the brine should be made of such a diameter that the velocity will be 4 ft. per second. The friction loss is found by using the equation: in feet = S/ +2o.2w . , . . (20) J d 2g $ 2g 2 = summation sign ; L = length in feet of any size pipe; d = diameter in feet of any size pipe ; w = velocity in f eet w per second ; n = number of elbows of any size pipe; L' and d' = dimensions of elbow ; /= coefficient = Pumping work per hour = M t XH. . . (21) Cold-storage warehouses are sometimes operated from a central refrigerating plant. These central stations will pay when there are a number of persons needing refrigeration within a limited radius. In the warehouse districts of Boston, New York, Philadelphia, Baltimore, Norfolk, St. Louis, Kansas City, Denver and Los Angeles and in the hotel district of Atlantic City central stations have been installed. The lengths of mains vary from i to 17 miles and the income amounts to about $12,000 per mile. The systems may be of the brine system or the direct-expansion system. In each case there must be at least two mains, a supply and a return. In the brine system the pipes must be carefully insulated, as the brine is at low temperature and about 2\ H.P. is required by the brine pump motor per ton of refrigeration to drive the brine through the main. The pipes are put in wooden boxes after covering them with hair felt soaked in rosin and paraffin oil. The box is waterproofed. The arrangement of the box is shown in Fig. 133. In this one set of pipes is arranged in a wooden box while in the other a split-tile conduit is used. The pipe is carried on supports at i2-ft. intervals for 2 -in. pipe and over, while for i-in. pipe 8-ft. intervals are allowed. At certain points the pipe line is anchored and on each side of this anchor COLD STORAGE 261 expansion is allowed to take place. Expansion amounts to 0.08 in. per 100 ft. for each 10 of temperature change. Expan- sion joints are placed at about 175 ft. intervals and should be of the pipe bend or swinging ell type, although the slip joint as shown in Fig. 134 is used. The anchor points should be FIG. 133. Conduits tor Refrigerating Pipes. points at which branches are taken off. The pipes used for brine may be of cast or wrought iron. In the direct-expansion system there is no need of insula- ting the supply main, as this will not absorb heat from any- thing as cool as or cooler than the cooling water, since the Ammonia is under pressure. The return main should be in- 262 ELEMENTS OF REFRIGERATION sulated, although this is not necessary if the ammonia vapor is warmed by the abstraction of heat in the storehouse to at least earth temperature. In direct-expansion installations it is customary to run three mains with cross-connections at man- holes and warehouses. One pipe is used as the pressure main, one as the return and a third as a vacuum line to be used when it is desired to test the piping in buildings. This line can be used to charge the pipe system of a building with compressed air for testing or for any other purpose. The joints in this system should be welded, as leaks are very expensive, ammonia being worth about 25 cents per pound. The cost of ammonia to charge such a system is another of the drawbacks. The FIG. 134. Expansion Joint for Ammonia Line. pressure in the suction main would be fixed by the coldest temperature necessary in any warehouse, and usually a drop of 15 Ibs. is allowed in the main to drive the vapor. The main should be anchored at points with expansion allowed for by bends in manholes. The load for such a station is figured by allowing i ton for. about 3000 cu.ft. for spaces up to 40,000 cu.ft. For insu- lated areas an allowance of noo sq.ft. to the ton will care for walls, floor and ceiling. The temperature on the three hottest consecutive days is used in computing the peak load. These may be found by getting the records of the nearest weather bureau office. For brine lines bell and spigot cast-iron pipe has been used. Voorhees has installed 1500 ft. of lo-in. pipe of this kind and is COLD STORAGE 263 supplying two warehouses of a total capacity of 1,500,000 cu.ft. He could not detect a rise of temperature in this length on thermometers reading 2 to |" ', showing that the gain of heat in the duct was not great. The pipes should be installed perfectly dry and kept that way. Paint is of little value when pipes become wet. The best thing to use as a paint is some form of bituminastic solution. AUTOMATIC REFRIGERATION The use of automatic apparatus by which the tempera- ture of rooms is kept constant is one of the recent develop- Temperature Suction Control FlG, 135. Automatic Refrigerating Plant. ments of the art. In this method an electric device controls the expansion valve and the pressure in the expansion coil regulates the motor operating the compressor. In a similar way the pressure in the discharge main controls the water supply to the condenser and on the pressure reaching a limiting high value the apparatus is shut down, thus guarding against the failure of the condensing water supply. The claim for such a machine is that the amount of refrig- 264 ELEMENTS OF REFRIGERATION eration is just that which is needed. It will be easily under- stood that when a room is cooled off below the required tem- perature the heat flow is increased and more work than that necessary for the plant is done. In automatic installations a constant temperature may be maintained and one no lower than that required. Of course this also prevents the temperature from rising above the desired point, and although this would rarely happen in a well-operated plant, a much lower tempera- ture may be carried to prevent it. To obviate the necessity of charging refrigerator cars with ice, compressor plants have been proposed. For instance in Ice and Refrigeration for May, 1910, there is a description of a patented system in which a small compressor is placed on the car. A device exhibited in Paris in 1900 for the Russian railroads is worth noting. In this a tank of liquid ammonia was placed beneath the car and connected to an expansion coil in the car. An absorber filled with weak liquid was attached to the other end of the coil, absorbing the vapor and main- taining a low pressure in the system. Enough liquid ammonia is carried for a given run and at the end of this run the liquid cylinder and the absorber are removed and replaced by new ones. The liquor can then be boiled and the ammonia regained and liquefied. In this way the most remote points of the car may be kept cool. The cold storage of foodstuffs on refrigerator cars has been recently improved by precooling the car and its contents before shipment. This is accomplished by forcing cold air in at one end of the car and drawing out warm air from the other. After a given length of time the current is reversed and air is drawn from the end into which it was forced, and withdrawn from the other end. In this way a large amount of heat can be taken from the car before ice is introduced. There are several of these precooling stations. The Santa Fe System has one at San Bernardino, California, and the Southern Pacific, one at Roseville, California. At these stations twenty-four to thirty- two cars are placed in connection with ducts which are covered with a heat insulator. By movable, COLD STORAGE 265 266 ELEMENTS OF REFRIGERATION telescopic or bellows tubes either the main door or one of the ice hatches is connected to one duct and both ice hatches or the other ice hatch is con- nected to another duct. The connection and ducts are well insulated. Air is then blown over brine coils or direct-expan- sion coils in a bunker room and is delivered at about 10 F. to one of these ducts, the ice forming on the coils from the moisture in the air being removed by blowing over warm air when the cold brine is cut off or by the use of calcium chloride brine which trickles over the coil. The air is then delivered by fans to a duct and then by means of tele- scopic tubes to the car, where it is warmed 20 or 25 F. and is drawn out through another duct by the suction of other fans. The pressure of the forcing fan is from ^ to f in. of water, while an equal vacuum is produced" by the suction fans giving atmospheric pressure at the car door. This is neces- sary on account of the leaks through the car walls. The air currents in the car are arranged to reach all parts and by a system of valves the air currents from the ducts are reversed in the cars. The fruit should be arranged in tiers sep- arated for ventilation. In some cases the air discharged into the car is shut off while the suction is continued, giving a partial vacuum in the car. On admitting the cold supply this enters the parts of low pressure. The vacuum also tends to draw out some of the gas from the COLD STORAGE 267 fruit. At San Bernardino the rate of 6000 to 8000 cu.ft. per minute per car is used for a period of four hours, reducing the tem- perature of car and goods to 40 F. The arrangement of the car is shown in Fig. 136. Fig. 137 shows the general arrangement of the plant, which represents an investment of about $900,000. After these cars are reduced to 40, or the temperature desired, they are iced at the station and then shipped east. The car may then be sent to Chicago without further icing and the fruit will be in far better condition than when treated with ice in the ordinary way. The cost of refrigeration as ordinarily run with ice from California to Chicago is $62.50 per car, while after precooling and original icing by the shipper the further icing is reduced to $7.50 per car. The cost of precooling is $30.00 per car and the original icing is $25.00. At Springfield, Mo., the United Fruit Co. cool their cars by this method, lowering the temperature 26 in twenty-four hours. In this way they may be held cold, the rise being 2 or 3 in 500 miles of travel. At these precooling stations ice is made for charging cars, and for that reason the plants are equipped with ice storage rooms. A storage plant is necessary for the cooling of the cars and the manufacture of ice. The plant equipment is as follows* Santa Fe at San Bernardino, Cal. : Ice-making capacity: 225 tons per day. Ice storage: 30,000 tons of ice (day room 900 tons). Compressors : two 3OO-ton Vilter refrigerating machines. Cars at one setting: 32. Bunker rooms: 44 ft. 6 ins. by 48 ft. by 9.3 ins., and 8 ft. 9 ins. Fans: eight i2o-in. Sirocco fans, 65,000 cu.ft. per minute each at f in. Insulation: 3 -in. cork on concrete. Pacific Fruit Express Co., Roseville, Cal. (S. Pac. Co.); Ice-making capacity: 250 tons per day. Ice storage: 20,000 tons (112 by 115 by 32 ft. and 75 by 115 by 32 ft). 268 ELEMENTS OF REFRIGERATION Cars at one setting: 24. Bunker rooms: 80 by 26 by 9 ft. and 8 ft. high. Compressors: two 25o-ton York compressors. Insulation ice house: concrete walls with 3 -in. lith. Air duct i-in. boards: |-in. asphalt, i-in. boards, 3j-in. granulated cork, i-in. boards. Fans: four fans 85 in. diameter, 27! in. wide, 44,500 cu.ft. per min. at 380 R.P.M. Pressure 3 oz. That this is not an untried invention is shown by the fact that over 2 2 ,000 cars have been precooled at the Santa Fe plant alone during a period of about five years. CHAPTERJVII ICE MAKING In making ice two methods have been used for a number of years. In one, distilled water is placed in cans and these cans are surrounded by brine, liquid ammonia, or cold air, which removes heat from the water and causes it to freeze. In the other, water taken from a stream or other supply (known therefore as raw water) is placed in a large tank which con- tains a number of coils of pipe for vaporizing ammonia or cir- culating brine. This removes heat from the water until gradually a plate of ice is formed on each face of the coil. If a large tank, 20 ft. wide by 60 ft. long by 8 ft. deep, contain 20 coils, 40 plates of ice could form. The first method is known as the can system; the second as the plate system. To study the peculiar details of these systems two general plans will be examined, after which the details of construction and operation will be considered. Figs. 138 and 139 are the plan and elevation of a 25-ton standard can system of the York Mfg. Co. In the plan view, Fig. 138, the compressed ammonia is delivered from the com- pressor to a double-pipe condenser, passing through a separator before entering the condenser. From this point the liquid ammonia is carried to an ammonia receiver shown dotted and seen in Fig. 140, and it is then taken to a liquid line on top of the brine tank at A, Fig. 139. From the liquid line it passes through expansion valves and enters the expansion coils of i J-in. pipe shown in the longitudinal section, Fig. 139. The liquid enters at the top of the coil and flows down to the bottom, abstracting heat from the brine. From Fig. 140 it will be seen that there is a coil between each two rows of cans. The manifold or pipe line A leading the liquid to the coils is carried 269 270 ELEMENTS OF REFRIGERATION ICE MAKING 271 272 ELEMENTS OF REFRIGERATION in a box filled with cork, as seen in Fig. 139, to prevent the abstraction of heat from the room. after leaving the expansion r n FIG. 140. Cross Sections of 25-ton Ice Plant. York Mfg. Co. valve. The cans are 30olb. cans, and the tank, which is 49 ft. 9 ins. by 21 ft. by about 5 ft., contains 352 cans, or fourteen 3oo-lb. cans per ton of capacity per twenty-four hours. The ICE MAKING 273 cans are nj" by 22\" by 44". The brine-freezing tank is made of J-in. steel and is well insulated on the sides. As shown in Fig. 141 the brine is given a circulation by means of a propeller blade driven by a motor or belt from an engine. This propeller is placed on one side of the end of the tank and by running a vertical partition longitudinally along the FIG. 141. Plan of De la Vergne Freezing Tank with Brine Agitator. center of the tank to within 2 ft. of each end a channel is made to cause a definite circulation. The vapors formed in the coils are collected in a return or gas header and are taken to the suction of the compressor. This line, Figs. 138 and 140, is carried through a storage water tank so as to remove heat from the distilled water which is to be placed in the cans. This completes the passage of the ammonia and the compressor delivers the ammonia again 274 ELEMENTS OF REFRIGERATION to the condenser. The water from the storage tank is taken to a point on the outside wall of the center of the freezing tank length and then discharged by a hose into cans which have just been emptied. An automatic device shown in Fig. 142 cuts off the water supply when the tank fills. These fillers are of various forms, dif- fering in detail. The K-C Filler shown in Fig. 142 has a ball at the top of the discharge pipe, the raising of which closes the valve controlling the flow of water. This is lifted by the water as it fills the can. When the water is frozen the wall of ice grows from the surfaces of the can and gradually forms a core at the center. All of the impurities in the water are forced toward this point, as the ice first forming is clear, and if the water is dirty or contains scum an opaque core is found at .the center. Hence the water in the early methods was dis- tilled and boiled to prevent the formation of this core. For this reason the exhaust steam was condensed and used. In the plant shown, Figs. 139 and 140, the exhaust from the engine is carried through a grease separator to a condenser placed on the roof of the boiler house. From here the condensed steam is carried to a reboiler. In this the water is brought to a boiling temperature by a steam coil and the oil and other im- purities remaining in the condensed steam as well as air are forced out. This reboiler is placed in the monitor of the roof. The water FIG. 142. K. C. Can Filler. ICE MAKING 275 -0 00 W'AV WI SlWJttWJJi 276 ELEMENTS OF REFRIGERATION is then taken through a cooling coil and finally passed through several filters for cleaning and deodorizing before entering the storage tank. When the water in the can is frozen it is taken from the brine tank by a crane operated by compressed air to a can dumper in which the ice is freed from the can and sent to the ante- room, from which it is passed into the ice-storage room. This room is cooled by a coil of pipe in which liquid ammonia is allowed to evaporate. Attention is called to the insulation of the freezing tank and the ice-storage room. The table below gives the various dimensions of York plants of different sizes with necessary data: . Lin.ft. cf Tons. Boiler Room. Compression Room. Tank Room. Storage Room. Ante Room. H" Exp. Coil in 300-lb, Wdth. Lgth. Wdth. Lgth. Wdth. Lgth. Wdth. Lgth. Wdth. Lgth. Brine Cans. Tank. 10 IS X 40 25 X 40 20 X 35 20 X 27 20 X 8 2.500 1 60 20 15 X 44 25 X 44 22 X 50 22 X 40 22 X 10 5 ooo 320 30 18 X 5'> 25 X 5') 28 X 53 28 X 43 28 X 10 7,500 480 40 1 8 X 5<"> 25 X Sfi 28 X *2 28 X 60 28 X 12 10,000 640 50 18 X 56 25 X 56 28 X 97 28 X 97 12,500 800 18 X 56 25 x 56 28 Xi28 28 Xi28 18,750 I2OO 18 X 56 25 X 56 28 Xis8 28 Xi58 25,000 1600 Fig. 143 gives the outline of a 50- ton Frick can ice plant from which dimension may be taken. In Figs. 144 and 145 the arrangement of a plate system for 50 tons capacity as designed by the Frick Co. is shown. In this plant a producer gas engine is used to drive the com- pressor, as raw water may be used and there is no need of dis- tilled water. The ammonia is compressed in a vertical compressor and delivered to a double-pipe condenser placed on the second floor of the engine house, Fig. 144. From the condenser it is taken into a receiver A in the freezing room near the wall and then delivered to a header B running along the freezing tanks. In the figure shown there are seven tanks about 20 ft. long, 10 ft. wide and 10 ft. deep, each well insulated against ICE MAKING 277 278 ELEMENTS OF REFRIGERATION ICE MAKING 279 heat loss. In each of these tanks are four direct-expansion coils supplied from a header connected to the main liquid line. By throttling the ammonia is allowed to enter the coil and the vapor is taken off from the mixture leaving through the main suction pipe C at the top. The arrangement of feed is such that there is much liquid left in the coil at the top and the mixture is taken from the top of the coil to an accumulator D where the vapor is separated, the liquid passing back into the lower part of the coils. On each side of an expansion coil is placed a heavy sheet of steel on which the ice forms. This ice forms gradually, taking six or seven days to make 12 ins. of ice, the plate weighing about 6 or 7 tons. As the ice forms the impurities are forced ahead of the ice, leaving clear ice from raw water. To release the ice when ready to harvest, the liquid is cut off from the coil and warm vapor is allowed to enter from the header E y this melts the ice from the plate and steam or warm brine is passed through pipes placed beneath the tank and on the sides to melt the ice from the sides and bottom of the tank. This is the only function of the thaw pipes shown in Fig. 144. The plate of ice is now lifted by a crane, using iron rods frozen in the ice to carry the load and after placing the plate on a tilting table and bringing it to a horizontal position, a saw is used to cut the ice into small blocks. The saw is mounted on a motor and moves on a sliding table. The blocks are stored in the anteroom or in the main storage room. The tanks are carefully insulated and the piping beyond the expansion valve is covered to prevent loss of refrigerating power. The tanks are well braced. The arrangement of piping is such that when warm ammonia is introduced from a special line the condensed ammonia may be drawn from the coil by a liquid transfer header. The liquid ammonia could go to one of the coils using ammonia liquid. The size of each tank is sufficient to give the complete tonnage of the plant for one day so that this tank can be emptied of ice and filled with fresh water the same day. The water remaining with the impurities is taken off. This would require that the num- 280 ELEMENTS OF REFRIGERATION ber of tanks equal the number of days required to freeze the ice to its desired thickness. The plant shown will make about 50 tons. With plate ice raw water may be used and there is no need of distilled water. Hence high-grade steam engines, gas engines or electric motors may be used for the prime movers. The use of the electric motor when power is taken from a central station during the off-peak hours of a public service company, furnishes a cheap method of driving, as the off-peak rate may be very low. The Chicago Edison will sell off peak power at i cent per kilowatt hour. In the figures shown the plant is driven by gas engines throughout. The water-circulating pump, the agitator blower, the air pump for the deep well, the electric generator and the filter pump are driven by a small gas engine. Air-storage tanks for starting the gas engines are placed on the side of the room. The gas producer and coal-storage room may be seen. The cold-water storage tank is used to cool the raw water after it has been filtered. This filtering is resorted to to take out suspended matter and bacteria. Having the general arrangement of the two systems, it will be advisable to examine the peculiar apparatus used with each. The distilled water apparatus is of various forms. When there is sufficient steam from the engines an arrangement is used as shown in Fig. 146. This is that used by the York Mfg. Co. The exhaust steam from the engine passes through an oil separator and feed-water heater and then to a condenser, where it is condensed by water used in the ammonia condenser. The line is equipped with a free exhaust valve set to relieve the pipe after a certain pressure is reached. The condensed steam is then collected in a return tank, from which it is pumped into the reboiler. This reboiler is operated with steam from the exhaust main or from live steam with the condensate pass- ing to the exhaust line. After reboiling the water is passed to a double-pipe water cooler and is delivered to a storage tank after passing two filters and a regulator. The cooling may be ICE MAKING 281 282 ELEMENTS OF REFRIGERATION done by warm condensing water from the condenser or by a cool supply. . The amount of skimming in the reboiler regulates the flow of water through the system by taking the scum to the regulator. ICE MAKING 283 When the exhaust steam is not sufficient to supply the dis- tilled water required, some form of evaporator is installed by which the exhaust steam is used to evaporate water and thus increase the yield of distilled water. At times the Lillie evap- orator is used, although any type may be employed. A single effect evaporator (one evaporator only) is in general sufficient for an ice plant. The arrangement of such a distilled water system as pro- posed by the De La Vergne Co. is given in Fig. 147. In this the exhaust from the engine passes through a pipe containing a free exhaust valve and passing through a grease separator enters the space around a set of tubes in a vertical evaporator. These tubes are held between tube plates and are filled with raw water which rises to a point above the upper tube plate. The condenser B has a vacuum maintained by the air-pump at such a pressure that the water in the tubes of the evaporator boils and passes over to the condenser. The boiling of the raw water removes the heat of the exhaust steam and this con- denses around the tube and collects on top of the lower tube plate. The condensate is drawn over through pipe A to the steam space of the condenser by the vacuum in B and is allowed to flow by gravity into the vacuum reboiler which is connected at the top to the steam space of the condenser. The air pump G is connected to the condenser above the water level and removes only air and vapor. The reboiler is freed from water by the pump H, which has an automatic float control in the reboiler. The reboiler takes live steam from the pump supply and the condensate from the coil is caught in a reservoir from which it is drawn by the vacuum in the reboiler whenever the valve K is opened by the float. The exhaust steam discharged from the engine may be by-passed around the evaporator by closing D, I and E and opening F and by partially opening D; when F is partially opened and 7 and E are open, some of the engine steam is allowed to flow to the condenser without evaporating any water. In this way the amount of distilled water is regulated. The reboiled water is pumped into the skimmer and then 284 ELEMENTS OF REFRIGERATION enters the hot-water storage tank and passes successively through the cooler, deodorizer and fore-cooler. The storage tank for hot water is provided with a float so that when this water FIG. 148. De la Vergne Grease Separator. is low the butterfly valve on the final discharge pipe is closed and prevents water from being drawn away. The atmospheric water cooler is cooled with water which may be used later for water supply. The deodorizer is a charcoal filter to remove FIG. 149. York Reboiler. odor and certain suspended matter. In the fore-cooler the water passes from it through a set of pipes which are cooled by ice water flowing over the set. This ice water is pumped from a tray beneath the coil and passed first over pipes which ICE MAKING 285 contain low- temperature amm&nia gas or ammonia liquid. In this way the cooling water is cooled and there is no danger of freezing the water within the lower pipes, as the flowing water cannot reach a point below 32 unless it freezes on the outside of the ammonia coils. FIG. 150. De la Vergne Reboiler and Skimmer, The arrangements in these figures give the general outline of all apparatus for distilled water. The arrangement of the grease separator of the De La Vergne Co. is shown in Figo 148, The action. of the baffle plates on the steam and oil is to remove the oil and waten The reboiler of the York Co. is shown in Fig. 149 while Fig. 150 gives that of the De La Vergne Co. In each of these a steam coil causes the water to boil and thus drives off air or 286 ELEMENTS OF REFRIGERATION other gases, while the oil which' forms a scum is taken off by the skimming edge of the holes at the right-hand end of the outlet chamber. The filters are vessels containing a layer of quartz sand FIG. 151. Sand Filter. on top of which is placed charcoal. This removes the last suspended matter as well as the odor and taste, and in order to clean this an occasional supply of steam can be admitted to melt off the oil which may collect. The same can be done to the pipes of the condensed water cooler. See Fig. 147. When raw water plants are used the filters may be of the ICE MAKING 287 sand type as shown in Fig. 151. In this there is a large shell of steel containing a number of collecting heads in a lower diaphragm, through which the water passes after traversing a 4-ft. thickness of graduated sand, fine at the top where the water enters and coarser as the bottom is reached. By introducing a small amount of alum solution from the coagulent box into the water in inlet pipe the suspended matter coagulates and collects on top of the bed. This collection, known as the " schmutz- decke," gradually becomes so thick that filtration is slow. The current is then reversed by valves A and B, the water entering FIG. 152. Frick Distilled Water Storage Tank. from the bottom by E, while valve D is closed and a valve to one side of A connects the top to the sewer. In this way the washing removes the deposit from the filter. A glass cup shows the condition of the water passing. After the main washing is completed, the current is reversed to its proper direction and the discharge allowed to waste to the sewer through a valve on the left of E until the water is clear, after which it is cut off from the sewer and passed back to the line. The maximum amount of water cared for by such filters with safety is 2.5 gallons per minute per square foot of filter bed. If a storage tank is used in place of the fore-cooler the water is cooled by the circulation of ammonia. The ammonia 288 ELEMENTS OF REFRIGERATION is either allowed to evaporate in a coil in the tank or the cool ammonia vapor from the expansion coils is taken through the coil and is warmed by the extraction of heat from the water. In this way ammonia may be superheated on entering the com- pressor. Fig. 152 is a view of the Frick storage tank with the coil shown as if the tank were transparent. The construction of the freezing tank for the can system of the De La Vergne Co. is shown in Fig. 141. The inner partition makes a circulation from an agitator positive, as shown by the arrows. The coils are arranged so that two FIG. 153. Frick Flooded System. are controlled from one branch. In the figure liquid ammonia is carried to the bottom of the coil and the vapor is taken from the top. This is the arrangement used with the new flooded system which has been introduced within the last few years. As shown in Fig. 153 this system consists in supplying liquid to the lower part of the expansion coil in large quantities so that the liquid will rise through a vertical branch into the accumu- lator to a point above the level of the top of the expansion coil. Then as the suction pressure is decreased by the action of the compressor there will be not only a further rise in the liquid through the liquid line but also a flow of vapor and liquid ICE MAKING 289 through the upper pipe leading from tank to accumulator. The accumulator acts as a separator, allowing the liquid separated to flow out at the bottom, while the dry vapor flows to the compressor or to the coils of the filtered water-storage tank. The level of liquid in the accumulator is carried near the bottom and the check valve leading to the liquid line allows liquid to flow from the accumulator. The reason for the employment of this system is the fact that when all the pipes of the coils have liquid ammonia in them they are all effective and moreover there is a slightly better transfer of heat due to a high coefficient for liquid to liquid. In the ordinary system certain of the upper or lower pipes are rilled with vapor because of the danger of getting liquid into the suction line and as a result these pipes are of little value since, after the liquid is vaporized, there can be little if any ab- straction of heat, because the brine is prac- tically at the same temperature as the vapor. Little heat can be abstracted to superheat the vapor. There is a small amount of heat transfer in these pipes, but small because the ammonia could not take up the heat rather than that the coefficient is small. In the flooded system (invented by J. Krebs in 1890) liquid ammonia finds its wav to the highest coils and although mixed with much vapor it may remove heat from the last foot of pipe. As a result of this the pipe surface necessary for a given tonnage may be decreased from 300 FIG. 154. Ice Can. lin.ft. of i|-in. pipe per ton to 180 feet per ton, although with longer pipe, not absolutely necessary, the efficiency of the plant is higher. The structure of ice cans is shown in Fig. 154. The various 290 ELEMENTS OF REFRIGERATION manufacturers make these cans in about the same shape and size. The following sizes are used by the largest manufacturers: ICE CAN DIMENSIONS Weight of Ice. Width and Breadth at Top. Width and Breadth at Bottom. Length Inside Over All. Galvanized Iron, Thickness. SO 8X8 7iX 7* 31 32 No. 16 U.S.S. IOO 8 Xi6 7iXi5i 31 32 16 20O 111X22^ LO|X2I| 31 32 16 300 11^X22^ IO^X2l 44 45 16 4OO II^X2 2 i loixaii 57 58 14 The band around the top is made of J by 2 -in. iron for the three largest sizes and J by i\ for the other sizes. The iron is turned over at the top and bottom and is well riveted and soldered. All metal is galvanized. The cans are handled by electric hoists or air hoists as shown in Fig. 155. These are mounted on light traveling cranes which carry the tanks to the ice dump. The air hose or electric cables are hung from roller hangers so placed that the loops will not reach the floor. The ice dump, Fig. 156, is arranged so that when a can with ice is placed within it, the center of gravity is above the point of support and it may be easily placed in an inclined position. This motion turns on the water sprinkler. When the water has melted enough ice to free the cake, it slides out and leaves the can and frame in such a condition that the center of gravity is below the support and the frame returns to the vertical position, automatically shutting off the water. The water which issued from small holes in the pipe is caught in the tray and sent to the sewer and the ice slides free of all contamina- tion. This is necessary, as the brine washed from the outside of the can should not come in contact with the ice. .The latest improvement in the can system of ice making has been the use of raw water for can ice. There have been numerous methods suggested for the production of clear ice from raw water. The raw water can ice of the earlier day was quite opaque and although as valuable for cooling as clear ICE MAKING 231 IJG. 155. Can Hoists. FIG. 156. Frick Can Thawing Dump. 292 ELEMENTS OF KEFRIGERATION ice this opaque ice would have little if any value for domestic service. When the water was filtered the cake would be fairly clear if little air was present except for the central core, and hence proposals were made to form a large cake and then cut this into four pieces on lines passing through the core, placing the opaque part on one edge. It was also proposed to freeze all but the core and then to remove this water containing the FIG. 157. Double Drop Tube. De la Vergne Co. impurities and introduce enough distilled water to nil this space. To prevent the formation of opaque ice it was found neces- sary to agitate the water while freezing to prevent the reten- tion of the small air bubbles which cause the whiteness. One method of agitating this water (patented in Italy in 1877 by Turretini) is to introduce air at the bottom of the can at a pres- sure slightly above that due to the water depth and this air jet produces necessary agitation. The air is introduced at the center of the bottom as shown in Fig. 160 entering in one of several patented ways. In Fig. 157 the air is introduced by ICE MAKING 293 a drop tube. The tubes are connected to a tee which is placed on an air outlet of the air pipe running between every other pair of cans on the framework which carries the top of the tank. The connection to the air main is made so that the drop tubes may be withdrawn from an automatic self-closing valve, Rotary Blower Core Pump FIG. 158. Plan of De la Veigne Raw Water Ice Plant. which prevents air discharge when the connection is removed. As the impurities gradually collect at the center in the core space they are finally drawn out by the core pumps and the space filled with distilled water or good clear raw water which has been filtered as carefully as the original water used. The general arrangement of the core-pump hose and refilling hose is shown in Fig. 158. In this figure will be seen 294 ELEMENTS OF REFRIGERATION ICE MAKING 295 the general arrangement of one air-supply header running from the main' header which receives air from the rotary blower. The core pump is connected to two lines of hose which may be put in any can for the removal of the core water. This amounts to about 10 Ibs. in 3oo-lb. cans. The water from the fore cooler is attached to four large hose lines for filling tanks and to two small ones for filling the cores, the same water being used for each purpose. The motors driving four agitators are shown in the figure. The air taken into the blower is first cooled to remove the moisture from it so that this moisture will not freeze in the air headers or drop tubes. The air is taken from the atmosphere at a high point in the plant and passed to a header from which it enters a series of pipes, Fig. 159, over which water near 32 F. is passed. In this way the air is cooled and the moist- ure in the air is condensed and dripped from the collecting header before the air enters the air main. The air may be taken through a screen to remove dust or any form of air cleaner may be used. The water is taken by a small centrif- ugal or rotary pump from the cold-water storage tank and dis- tributed over the air coil, after which it falls over an ammonia- expansion coil, which cools it to about 32 F. This water is then collected in the tank from which it is pumped to the cans as needed or back over the air coil. The air thus dried will not clog the drop tubes as it enters and meets the cold walls of the tube. The pressure necessary for 3oo-lb. cans is about 2 Ibs. per square inch, due primarily to the amount of sub- mergence of the end of the drop tube. This air keeps the water agitated and thus wipes off any bubbles of air which might cling to the surface of the ice. In Fig. 1 60 the tube A is fastened to the side of the can and in this the air is forced from the end B through the ice as it forms, leaving a small seam through which air flows, driving the water out of it and keeping the water above agitated and driving the impurities gradually to the top D of the can. This leaves the hollowed top of ice with all impurities above the grid F in the unfrozen water. This water is thrown away when 296 ELEMENTS OF REFRIGERATION the can is taken out and the grid with the ice on it is removed, leaving clear ice of uniform length for storage. The grid also serves to freeze the center cup at the end due to the conduction of the iron. In this system the pressure has to be increased as the ice forms. This of course is automatic through the use of a valve which throttles the air discharge until resistance is brought FIG. 160. York Raw Water Can. on by the formation of ice. The pressure at the pump remains constant, being used up in pipe and valve friction when first applied, and finally the ice friction requires the full pressure as the ice closes in. The gauge pressure is about 18 Ib. per square inch. The power used in the compressor is about 0.4 H.P. per ton of capacity. The air used amounts to 1.8 cu.ft. per can per minute at start to 0.3 cu.ft. per minute after freezing. ICE MAKING 297 The two methods described are those used by two large manufacturers. There are many other methods employed which have given satisfaction. For instance, the agitation has been accomplished by drawing water from the core and then allow- ing it to discharge back again, th'.s back and forth motion pre- venting the formation of opaque ice. One of the first methods was to rock the cans and after this, agitation was by rods and then by air discharge. Another method patented by Ott Jewell is an ice can in which the brine is passed through a double wall of the can and air is introduced at bottom to agitate. The Beal patent of 1913 is similar to the York method described above. The Ulrich patent brings the air pipe in on the out- side of the can. The plate system accomplishes the result of the raw-water can system without the complication of air-pump or rocking apparatus. On account of the increased space and an increase of about 30 to 70% in the initial cost, due to the larger building, the plate system is not installed as frequently as the can system. In 1915 the De La Vergne Company stated that there were 150 plate plants in operation in the United States. Of course with the plate system almost any kind of water may be used. The generation of the liquid ammonia may be accomplished by an absorption system as well as the compression methods described. The arrangement of the ice apparatus is practically the same when the absorption system is used to compress the ammonia. If an absorption system is placed where compres- sors are shown in the previous figures the apparatus would be that used by the makers of that type of apparatus for ice making. There are more than one thousand plants in the United States, of which about 81% are operated by compression and 1 8% by absorption. The output of these is over twenty- three million tons of ice. The natural ice crop is probably equal to or greater than this. The curve of delivery of ice will follow the curve cf temperature difference above 32 F., although there may be some changes due to manufacturing 298 ELEMENTS OF REFRIGERATION or other application of ice. In any case it is well to draw a consumption curve to be expected or known from previous records. From this curve the capacity of the plant and the size of the storage room may be found. These various methods are ap- plicable in special cases. The plate system is advisable with expensive fuel and very poor water, while with better water the raw- water can sys- tem may be used. When fuel is cheap the distilled can system may be used and when there is exhaust steam from other machines the ab- sorption system should be employed. The absorption system may be operated in an isolated plant with economies as good as the compres- sion system. The water for ice plants is usually taken from deep wells. The wells are rarely artesian and the water has to be pumped. The pumps are of various forms. Deep-well pumps have a pump bucket operated at the end of a long rod by a steam piston in engine room, Fig. 161. An air-lift pump is one, Fig. 162, in which compressed air is allowed to enter the- water pipe and by aerat- ing the column of air and making it lighter than the water outside of FIG. 161. Deep-well Pump. the casing it drives the water out of the discharge main. Other pumps are used. The air-lift pump has the advantage of being simple to install, and of having all of the working parts accessible as well as being able to deliver a large quantity from a given well. ICE MAKING 299 FIG. 162. Air-lift Pump. Exhaust Steam Drain Drain FIG. 163. Oil Separators. 300 ELEMENTS OF REFRIGERATION It is very inefficient in the use of power and hence is more expen- sive to operate. Its advantages are such, however, that the pump is extensively used. The power to drive a deep-well pump may be figured from the quantity M w and the lift H as H.P. for deep-well pump = ^^r- 55oXerL M w = weight of water per second in pounds per second; H = height in feet from water level in well to discharge nozzle ; Eff. = 70% for deep-well pump from steam to water; = 30% for air-lift pump from compressor motor to water. u- t tt WxH Air per minute in cubic feet of free air = . 10. W = cubic feet of water per minute. To treat water from which the oil cannot be removed in the ordinary way A. A. Gary suggests in the Transactions of the American Society of Refrigerating Engineers to pass the water through a long coke filter, or to pass the steam through a steam washer in which the steam has to pass through water or over water as shown in Fig. 163. An enlarged chamber on the steam main to cut down the velocity of the steam and per- mit the steam to come in contact with a series of screens was also suggested. In planning for the amount of distilled water for an ice plant an allowance of a waste of 25% of that turned into ice must be made. If the amount of steam from the various machines is not sufficient to supply the necessary distilled water some form of evaporator as shown in Fig. 147 must be used. Fig. 164 shows the form of Lillie evaporator. In this exhaust steam from the engine and other auxiliaries is discharged at H and enters the tubes E, which have a reduced oressure within, due to the suction through the small holes drilled in the caps of the left-hand end of each of them from the low pressure which ICE MAKING 301 exists in B. This low pressure is caused by a vacuum pump attached to a condenser which is joined to the evaporator by the pipe N. Water from the sump K is pumped by the centrifugal pump L through M to the G box whence it discharges through eleven pipes F and falls over the pipes E. 302 ELEMENTS OF REFRIGERATION This water is heated and condenses some of the steam inside of the tube E, and the pressure is so reduced that the water will boil at a lower temperature than that of the steam inside. The evaporation of this water will cause further condensation of the steam inside. The condensed steam drops to the front of C and is removed. As the water in the shell is evaporated the sump box K does not contain enough water to lift the float and hence more water is introduced. When the water in A becomes heavy with salts after evaporating a lot of water, the heavy liquid is removed by opening R. To compute the necessary surface and size of evaporator the following equations may be used: From the equation M,(i' t -i' )=M(i'' t -i" )+Q e , . . . (i) the amount of water M w from the steam M s is found. In this M s = weight of steam condensed per hour; M w = weight of water evaporated per hour; Q e = heat radiated from covered evaporator, computed from Chapter V; i'i and i'o = heat contents of dry steam entering and water leaving at pressure of exhaust steam; i' f Q and i" i = heat contents of dry steam leaving at pressure assumed in B (20 less than entering steam) and of the entering water. The surface is figured by M w (i'i-i'o) , , ~ ' ' to = temperature of entering steam; /'o = temperature of steam leaving; K = 400. An important consideration in planning an ice plant is the sanitary condition around the plant. Since ice is to be used for domestic purposes and may be introduced into food or ICE MAKING 303 drink, it is necessary that cleanliness be insisted upon. The men walk over the covers of the cans, and dirt on the footwear may fall into the cans, hence there should be no chance for the workmen employed in harvesting from going through places when contamination may occur. The floor of water- closets for instance should be kept so clean that nothing can cling to the footwear. The water-closets should not be placed so that workmen would have to pass through stable yards or over roadways to reach them. In many ice plants conditions exist such that men must pass through regions where the boots take up this contaminating matter. The condition of the water- closet should be bright and clean. Money spent here on tile work and terazzo flooring is not wasted. The wells or springs from which the water is taken must be placed so that they may not be contaminated by materials blown by the winds or from ground or subsurface seepage. The use of cesspools for water-closets should not be tolerated, especially where wells or springs are used for water supply. To keep the plants clean they must be so constructed that dirt will show, and hence the covers, walls and all parts of the plant should be painted white. It is also advisable to have no one walk over the tank tops who does not put on rubber over- shoes which are not worn anywhere else. Freezing Tanks. Freezing tanks are usually made of steel plate with insulation beneath and around them. This is shown in Fig. 141. The insulation is sufficiently heavy to cut down the heat loss to a low value. The thickness is fixed by finding the minimum yearly cost due to heat loss, interest, depreciation, taxes, insurance and maintenance. The tanks for the plate system are sometimes made of timber. These must be care- fully braced whether of wood or metal because of the depth. Reinforced concrete has been used for brine tanks. The bottom and sides are made of 6 or 8 ins. of concrete with f in. reinforc- ing bars placed i ft. apart and 2 ins. within the concrete from the brine side. This is followed by 2 ins. of cork board and then five layers of tar felt put on with hot coal tar, on top of which is placed 2 ins. of concrete with a smooth finish. To cut 304 ELEMENTS OF REFRIGERATION down the heat transfer a thick layer of cinder may be used around the tank, 16 ins. of dry cinder being equal to 2 ins. of cork. There is a difference of opinion as to the advisability of using concrete for the brine tank, as some claim calcium chloride disintegrates the concrete, but others say that concrete is perfectly satisfactory. In planning the size of brine tanks the time of freezing must be assumed and sufficient cans or plate tanks must be installed to give the required capacity. In plate work one freezing tank should be large enough to give the required output. If the weight of ice is taken 57^ Ibs. per cubic foot, the volume of the plates for the given tonnage, assuming a thickness of 12 or 14 ins., may be found, and from this the volume of the tank, the Reinforcement Concrete FIG. 165. Reinforced Concrete Brine Tank. depths being about 10 ft. and the widths 16 ft. The time of freezing the plate ice is given by Macintire as 2 1 a 2 (3) h = hours of freezing; a = thickness in inches; //= temperature in refrigerating pipes in deg. F. This takes about six days, so that six or seven tanks are used. The number of cans is found in the same way. If the smaller thickness of the can is represented by a, then the time is given by Macintire as h = ^. (4) a = thickness of can at top in inches. ICE MAKING 305 In this way the total output during the freezing is /?Xtons 24 And the number of cans is given as // X tons 24XWt. per can = number of cans. - (5) Ordinarily fourteen 3oo-lb. cans are used per ton of capacity. This means fifty hours for the formation of the ice. If the number of cans is increased it means that there is a longer time for the ice formation and hence a smaller difference in brine and water temperatures, which means a higher back pressure and less work, while a decrease in the number means a lower brine temperature to give the smaller time for freezing. This means a lower back pressure on the compressor and hence more work. It is well to compute the yearly cost of ground, build- ing and equipment against the cost of power in figuring the number of cans. To compute the temperature of the brine a value of 2.6 for K is used. This same thing is true in regard to the number of tanks in the plate system. To show this Thomas Shipley has computed the following table: EFFECT VARIATIONS IN CAN ALLOWANCE HAVE ON HORSE-POWER REQUIRED TO PRODUCE ONE TON OF ICE. (With Single-acting Compr.) I 2 3 4 5 6 No. 300-lb. Cans Per Ton Ice Making. Average Brine Temperatures Needed to Produce Ice. Rate of Heat Transmission B.T.U. per Sq.ft. per Hr. i MD. Temperature Required in Pipe. Corresponding Evaporating G. Pressure. Total Brake H.P. per Ton Ice Making 185 Lbs. C. P. F. for Pipes. op Lbs. IO 12 14 7 ii 14 15 15 -3-3 . +0.7 3-7 13-3 16.2 2-77 2 -.45 .. 18 16 18 15 5-7 7-7 20 21.7 2-352 2.27 Note. Evaporating surface in the freezing tank assumed in this table is 108 sq.ft. or 250 ft. of ij-in. pipe per ton of ice. Note. Tables are based upon the water to be frozen being delivered to the cooling and freezing system at 70 F. Work done by cooling system =30 B.t.u. per pound of ice. Work done by freezing system = 200 B.t.u. per pound of ice. 306 ELEMENTS OF REFRIGERATION Expansion Coils. In the coils of brine tanks the liquid ammonia may enter the upper or lower pipe. When the flooded system is used the liquid is introduced at the bottom, and it seems unreasonable to bring it in at any other point if the coil is to receive its full supply of liquid. In this case the vapor header may be drained to the low liquid line to return any liquid unevaporated. This really gives a flooded system. Before the wide introduction of the flooded system there was a great difference of opinion over this point among the refriger- ating engineers, but this matter seems to be settled by the adoption of the flooded system. In some cases the brine may be cooled in a brine cooler on one of the types shown in Figs. 19, 8 1 and 82 and the brine pumped to the freezing tank. Such a device is not so good as the use of expansion coils in the freezing tank, as this method keeps the brine at a low temperature throughout by abstracting heat from it as it abstracts heat from the freezing water. The amount of this surface in a brine tank is figured by allowing a value of K of 15 due to the low velocity of the brine over the coils. In a brine cooler especially of the double pipe type or the shell type a much higher value of K is used, due to the higher velocity of the brine. Since this method is rarely used the case of the expansion coil in the tank will be con- sidered. It has been found that 120 to 150 lin.ft. of i^-in. pipe is sufficient to care for a ton capacity with ordinary coils and about 80 ft. have been found necessary in the flooded system. In any case it is a matter of abstracting the heat and if the surface is cut down the back pressure must be decreased to give the necessary temperature difference. This means greater power for the same refrigeration. One must compute the yearly cost on investment on pipe against the cost of power. Assuming sixteen cans per ton, Thomas Shipley has computed a table showing the effect of change of pipe length. The powers required are the powers applied to the compres- sors to drive them, whether by belt, direct-connected motor or engine. The auxiliaries require about 0.3 to 0.4 H.P. ICE MAKING 307 EFFECT OF VARIATIONS IN EVAPORATING SURFACE ON HORSE-POWER REQUIRED TO PRODUCE ONE TON OF ICE WITH SINGLE-ACTING COMPRESSOR. I 2 3 4 5 6 7 Lineal Ft. of ij-in. Pipe per Ton of Ice Making. Sq.ft. Pipe Surface, External. Rate of Heat Trans- fer for Pipe = K. Average Tempera- ture of Brine. Tempera- ture in Pipe. Gauge Press in Coil. Total Brake H.P. per Ton of Ice Making at 185 Lbs. Comp. Pres. F. F Lbs. 150 65 IS 16 i.i 14.85 2.661 2OO 87 15 16 3-2 18.1 2.468 250 108 IS 16 5-7 20. o 2.352 300 130 IS 16 7-45 21.5 2.279 350 152 IS 16 8.7 22.5 2.218 The pressure of compression has an important bearing on the efficiency of the plant. An endeavor should be made to use as cool water as possible for the condenser to keep this pressure low.* The effect of this is seen in the following table by Thomas Shipley: POWER REQUIRED PER TON OF ICE AT DIFFERENT CONDENSING PRESSURES WITH A SINGLE-ACTING COMPRESSOR WORKING UNDER A SUCTION PRESS- URE OF 20 LBS. Condensing pressure 85 105 125 145 165 185 205 225 245 Corresponding Tem. 47.6 58.6 68.1 76.6 84.2 91 .0 97.3 103.2 108.9 H.P. per ton of ice . . i . 162 1.408 i .646 1.874 2.114 2.352 2.587 2.851 3-098 The rule for the number of tanks and size of the expansion coil has been worked out on the assumption of 200 B.t.u. per pound of ice in the freezing tank and 30 B.t.u. per pound in the cooling tank. Of course there are average results, but in some cases the quantity must be computed owing to peculiar conditions. The heat to be removed in the cooling system per pound of ice made, if 15% excess is allowed and water is at t F. and is to be cooled to 32 is . ...... (6) * If water has to be pumped and is bought, a calculation must be made for the cost of water and of power for the compressor and for the pump for different quantities of water and the one giving the best result used. 308 ELEMENTS OF REFRIGERATION The heat of fusion is 143.4 B.t.u. and the specific heat of ice is given by c specific heat ice; t = temperature of ice in degrees C. This has been tabulated by Dickinson and Osborne as follows : HEAT TO FREEZE ONE LB. OF WATER AT 32 AND TO COOL ICE TO TEMPERATURE. t Q t Q t Q 20 167. 2 2 159-5 16 151.2 -18 166.3 158.6 18 150-3 -16 I65-5 2 157-7 20 149-3 14 164.7 4 156.8 22 148.4 12 163.8 6 155-9 24 147-4 10 163.0 8 155-0 26 146.4 - 8 I62.I 10 I54-I 28 145-4 - 6 l6l.3 12 I53-I 3 144.4 - 4 160.4 14 152.2 32 143-4 The heat used then will be i. t$Q f =Q = 1. 15 x 160 = 184 B.t.u. approx. . . (8) Although only 184 B.t.u. are needed, the radiation will be an additional amount, making 200 B.t.u., used by Shipley. The radiation loss may be computed. The size of pipes for brine, ammonia and water are com- puted by method of Chapter VI. From the curve of ice consumption, as shown in Fig. 166, the main demand for ice can be found and the question arises: Is it better to put in enough ice-making capacity to carry the peak load, having idle machinery during a large part of the year, than to install apparatus for the mean capacity and operate at this capacity, storing at time of low demand to carry the amount demanded at times above the mean curve? This problem is one which can be computed. The extra apparatus ICE MAKING 309 and plant needed beyond that for mean load is found and the cost of interest, depreciation, taxes and insurance is compared with the cost of storing, loading and removing ice, including the cost of the building. To store ice and hold it from spring to midsummer and then take it from storage costs 25 to 30 cents per ton according to W. E. Parsons. J. N. Briggs increases this by the yearly cost of the storehouse, 15 cents brings the cost to 40 or 45 cents per ton. This includes the expense of holding, and in this AUU 300 200 23F. 23F. 33 F. 46 F. 59 F. 68 73 71 63 51 39 28 Mean Height 100 Jan, Mar. Apr, June July Months Aug. Sept Oct. FIG 166. Curves of Tons per Day. Arranged for months for Troy, N. Y. Monthly average temperature for forty years. problem the cost of insulation isj^ompared with Hjat qf absorb - ing the .heat transferred to determine the amount of insula- tion. After this is fixed the amount of heat loss is found and cared for by melting ice or by refrigerating coils. The latter method is the better, as it is cheaper to cool the room than to make an equivalent amount of ice to do this. The data from a storehouse of this kind will be mentioned. From the amount of heat to be supplied by the brine coils in the freezing the surface may be computed by assuming the temperatures of the water in cans, brine, and ammonia. Call these t w , /&, and t a , 310 ELEMENTS OF REFRIGERATION Can surface in sq.ft. per ton of ice _2oooX[i.i5Q/+Qr] _ 6410 . Coil surface in sq.ft. per ton _2oooX[i.i5(?/+(?r] _ mi ( ^ n ~~; T v IO J The amount of refrigeration for plant per ton of ice = [ft+i.i5Q/+(?r]2ooo 199.2X24 249 An ice-storage plant in Philadelphia for 10,000 tons of ice is 113 ft. long, 78 ft. wide, 60 ft. high. It is built of brick 22 ins. thick. It has a 6-in. reinforced concrete roof carried on girders. The insulation of the walls is two 2 -in. cork boards held in place with cement and furnished with a cement plaster. The floors are of concrete over which two 2 -in. cork boards are laid in hot asphalt for insulation. The ceiling is insulated with 3 ins. cork attached by Portland cement to the rein- forced concrete. To refrigerate the room, 15,000 ft. of 2 -in. wrought -iron pipe for direct expansion are used. This held the room at 22 F. in the warmest weather. To handle the ice, plunger elevators with oil and brine as the working fluid are used. Ice is stored in these houses in such a way that the ice will not press against the walls and the blocks should be so placed that they will make a stable pile. This is important. In distributing ice it is well to use a map of the city and plan routes so that they will not overlap. Inspectors must be employed to watch men and foremen to direct their work. To guard against loss of money ice books are sold by drivers, who are held responsible for them, and in addition the amount of ice delivered to the driver and the amount sold by him must receive a daily check. It is best to use a single-horse wagon ICE MAKING 311 in charge of one man, since where two men are on the wagon there is apt to be talking, drinking and more waste of time. To encourage better work it is well to give a bonus. The use of 3 -ton automobile trucks has been found to cut down the expenses of distribution in the saving of time in reach- ing the point of delivery. This is especially true if the truck is used to carry ice to the delivery wagons. In using automobile trucks the work must be arranged to handle ice quickly. There must be no waiting, as the fixed charges are so great that unless a large volume of work is done, there is loss. Solicitation of trade in an unobtrusive way, care in adjust- ing all complaints and judicious use of advertising will bring good results. It is absolutely necessary for the foreman to be acquainted with the kind of service given to consumers. CHAPTER VIII OTHER APPLICATIONS OF REFRIGERATION THE use of refrigerating in various industries is increasing. In a recent list of applications over one hundred industries were mentioned in which refrigeration played an important role. A few of these will be described. In the manufacture of candy, especially chocolate-coated candy, there is a necessity for a uniform temperature to set the chocolate and to give uniform results. Cool air is blown into the rooms to keep them at a temperature of about 68 F. as chocolate cannot be dipped above 72. This air may either enter from an overhead duct at 50 F. and be used to cool the room enough to set the chocolate, or air may be intro- duced into setting boxes shown in Fig. 167. The chocolates are placed in this box as soon as one plate has been filled with dipped chocolates. By pressing a pedal the plates in the box are raised to admit a new plate from beneath. The plates are separated by distance pieces so that there is no danger of the candies being mashed by contact. Cool air is introduced into the interior of the box from the duct A and before entering the room this air chills the candy, setting the outer coating. The heat which it removes would have to be removed in any case to hold the room at 65 or 68, and so this apparatus requires no extra refrigeration, but it applies the cool air where it will do the greatest good. The springs B B hold the plates in position. This is employed by Harter & Co. of Ohio. They have a 6^-ton machine, cooling a bunker 5' X 5^X22', using five stands of 2-in. direct-expansion pipes 12 ft. high and 20 ft. long for cooling. A 52-in. Buffalo Forge Fan at 120 R.P.M. drives the air through a 24-in. riser to i6-in. pipes with 3-in. branches leading to the cold boxes. This saves refrigeration, 312 OTHER APPLICATIONS OF REFRIGERATION 313 as the room need not be cooled to such a low temperature. In the plant under discussion the 72 boxes, each caring for 150 Ibs. of chocolate per day, required 6| tons while it would require 15 tons for the ordinary cool room according to the designer. At the Baker Chocolate Plant six loo-ton absorption machines are used to supply 40,000 lin.ft. of 2 -in. galvanized FIG. 167. Setting Box for Chocolates. iron pipe. The pipe is carried throughout the plant and bunkers and fans are placed where required. The specific heat of chocolate is given as 0.9 by Siebel, and he also recommends the air to be supplied at such a satura- tion that the relative humidity at room temperature is 72%. The heat removed in this case is similar to that for the blast furnace as given on p. 324. The heat from the walls of the buildings, machinery, lights, persons and chocolate are given by the following: 314 ELEMENTS OF REFRIGERATION Heat leaking through walls per hour = Qe=2KF(ta-t r ). . . .'., . . (l) Heat from machines and lights per hour = g,= 25 4 6H.P.+MQ,. . . Y . . (2) Heat from persons =Q P = N2Q' (3) Heat from chocolate = Q C = M C X 0.9 X(/ c /r). . ... (4) K = coefficient of transmission B.t.u. per deg. per sq.ft. per hr.; F = square feet of different wall areas; t a = outside temperature ; t r = temperature of room ; HP = horse-power of machines; N = number of lights; Q g = heat per hour per light ; ^2 = number of persons; Q f = heat per person ; M c = weight of chocolate per hour; t c = temperature of chocolate ; Q=Q e +Q,+Q P +Q c . In breweries the refrigerating machine is of great value. Here the cooling of liquids and the removal of the heat of fer- mentation are the chief applications. After the beer is brewed the solution, known now as wort, has to be cooled and this is done usually in a Baudelot cooler. The Baudelot cooler, Fig. 168, consists of a series of horizontal pipes formed in a coil through which cold water is passed and below this is another coil in which liquid ammonia is allowed to boil or brine or cold water is circulated. Over these coils the hot wort is distributed. The wort is exposed to the air and will take up oxygen, thus throwing down certain matter in solution, and also there is some solid matter thrown out due to the cooling. The room in which this occurs is usually OTHER APPLICATIONS OF REFRIGERATION 315 enclosed in glass or copper so that it may be kept clean and free from foreign bacteria, which would produce growths not desired in the fermentation. This cooling is intended to reduce the temperature to prevent bacterial growth should any enter. The heat removed from the wort depends on the range of temperature and the specific heat. The specific heat varies from 0.941 at specific gravity 1.032 to 0.861 at specific gravity 1.0832, with a negative allowance of 0.00015 for each degree Water Outlet Upper Portion of Baudelot cooled by Well or Hydrant Water FIG. 168. Frick Baudelot Cooler for Beer Wort. above 60 F. The ordinary drop in temperature is from boil- ing to 110 F. in a storage vat and then the wort is passed over the cooler and reduced to 70 F. on the upper coil and to from 40 to 50 F. on the lower coil. The beer is then taken to fermenting tubs where the sugar, formed in the operation from the starchy matter by the diastase which was produced by the change of barley to malt, is split up into CO 2 and alcohol by the action of yeast added to the wort for the fermentation process. The bacteria of the yeast 316 ELEMENTS OF REFRIGERATION take up oxygen and also nitrogen. This action produces heat and as a rise in temperature would make brewing difficult FIG. 169. Brewery Plant Showing Cellars and Beer Cooler, After De la Ver^ne. and because the beer is to be reduced gradually in temperature, it is necessary to cool this liquid in the fermentation tubs. This is done by circulating cool water through attemperating OTHER APPLICATIONS OF REFRIGERATION pipes. The water is cooled in the^ attemperator by brine or direct expansion. After this the beer is placed in storage tubs to age and finally put into large casks, where it is properly finished off. From this point it is placed in kegs for shipment. This is known as racking. The heat removed is the heat leakage through the walls, Q w ; the heat from the Baudelot cooler, ()&; the heat from the attemperator, Q h for the fermentation. The heat Q w is computed in the manner mentioned before as soon as the temperatures of the rooms are fixed. The fer- menting room is kept at 42 F., the storage rooms at 33 F., the cask rooms at 36 F. and the racking room at 32 F. The heat Qj, is given by Q b = vol. X62. 5 Xsp.gr. Xc(fe-//), .... (5) V = volume of wort per hour in cubic feet; sp.gr. = specific gravity = i .05 mean; c = specific heat = 0.9 mean; t h = temperature from brewing =150 to 190 F. ; //= temperature to tubs = 40 F. According to Siebel the heat removed in fermentation is given by ....... (6) M m = lbs. of maltose split up per hour into CCb and alcohol; 330 = B.t.u. produced by the breaking up of i Ib. of maltose. This may be written as Q f =6soXM a . . . i '..... (7) Ma = lbs. of alcohol produced per hour. This usually amounts to a ton of refrigeration per 40 to 60 barrels per day. The total refrigeration of the brewery amounts, according to Siebel, to a ton for every four barrels per day. 318 ELEMENTS OF REFRIGERATION The amount of surface may be computed by the methods of Chapter V. Ordinarily the Baudelot wort coolers are made of ten 2 -in. pipes 16 ft. long for fifteen barrels of beer per hour to cool the wort from 70 to 40 by the use of direct ammonia expansion. With brine these pipes would care for ten to twelve barrels per hour. The water portion of the cooler to cool the wort from 170 to 150 to 70 would be made of about the same number of pipes. These pipes may be made of copper. In the at tempera tors, coils are made usually of a coil diameter of two-thirds the tub diameter. Twenty-four square feet is allowed by Siebel per 100 barrels of wort. The rooms for storage of hops should be held at about 36. The cooling of air is one of the modern applications of refrig- eration. This cooling is not always undertaken to obtain cool air, for it is used in blast-furnace work where warm air is needed, but in this case the cooling is to reduce the moisture content of the air. Air at any temperature may contain a definite quantity of moisture, and when this amount is present it is said to be saturated. The amount of moisture per cubic foot to saturate the air is different for each temperature. It amounts to the weight of i cu.ft. of steam at that temperature. The air and moisture are really the mixture of several gases and a vapor, and by Dalton's law the amount of each constit- uent is proportional to its partial pressure. The moisture or steam may exert the pressure corresponding to its tempera- ture if saturated, and with this pressure the weight must be that required to produce saturation. If the air is not saturated the moisture is in a superheated condition. The ratio of the amount present to the amount required to saturate the air is known as the relative humidity, as was stated on p. 50. The method of finding the relative humidity was given on p. 175. From Fig. 92 it is seen that air of relative humidity 0.90 and of temperature 85 contains 13.7 grains of moisture per cubic foot. If this air is cooled to 82 F., it will be saturated, and if cooled to 70, it can only contain 8 grains of moisture. So that 5.7 grains must be thrown out of suspension. If the air is cooled to 36 F., the air contains only 2 grains per cubic foot. OTHER APPLICATIONS OF REFRIGERATIO, 319 Thus in the summer, warm air may be passed over a set of coils containing cool brine and when this air is delivered into building it will be cooled and contain less moisture than in its first atmospheric state. If atmospheric air is always cooled to a low temperature, say 34, before being introduced into a system, the air will always contain the same amount of moisture no matter what the original relative humidity of the warm air has been. It is this fact which has been applied by James Gayley to the drying of blast-furnace air. In an article by Gayley in the Transactions of the American Institute of Mining Engineers, he points out that in the Pitts- burg district the variation of monthly average temperature is from 31.7 to 76.2 during the year, the amount of moisture per cubic foot in these two cases being 1.83 grains and 5.60 grains. The moisture varies from 0.56 to 8.78 grains, changing by large amounts even in one day. In January this change was from 0.56 grain to 0.88 grain on the same day and from 5.55 to 5.74 grains on a day in July. This means that although the ore, and coke and limestone have a definite composition within 10% variation, the moisture content may vary 100%. This results in a varying amount of coke to care for the dis- sociation of the moisture and a difference in iron produced. The ordinary furnace uses about 40,000 cu.ft. of air per minute and this contains 40 gallons of moisture per hour for every grain. To make this uniform Gayley proposed to cool the air and after trying an experimental installation he applied it to the Isabella furnace at Etna, Pa. In this plant the air is drawn over the pipes A , which are supplied with brine. These pipes are arranged in three coils of twenty-five 2 -in. pipes, 20 ft. long. The three coils are placed above each other and are supplied from the headers C and dis- charged into the 4-in. headers B. The coils are arranged with staggered 2 -in. pipes and there are sixty coils in the width of the bunker room, making 1 80 coils of twenty-five pipes. Cross- walls divide the coils into four sets. There are 90,000 lineal feet of pipe. The room is 44 by 28 by 36 ft. and is lined with 2- 320 ELEMENTS OF REFRIGERATION FIG. 170. Gayley Air Cooler. OTHER APPLICATIONS OF REFRIGERATION 321 in. cork. Air is drawn in by fan D and put into the space E under 1.2 oz. pressure to care for the frosting of the pipes and the closing of the air passage. The fans F keep the air evenly distributed over the brine coil. The air finally enters the 6-ft. pipe G and passes to the blowing engine and after compression it is sent to the hot-blast stoves. The moisture taken out amounts to from 3000 to 5000 gallons in twenty-four hours. Some of this freezes on the pipe as the brine enters at 16 F. and leaves at 33. The defrosting is necessary every fourth day, and for that reason the brine is shut off of one of the four compartments and the warm water from the ammonia condenser is passed through the pipes for two or three hours. The plant is equipped with two 225-ton compressors requiring 460 H.P. There are thirty-seven coils in the atmospheric ammonia con- denser and twenty submerged double-pipe brine coolers placed in a brine tank 7 ft. 6 in. deep and 22 it. 6 in. long. The coolers are made of twelve double pipes, 2 ins. and 3 ins. diameter and are 17 ft. 12^ in. long. The brine in the tank and in the inner tube is cooled by the ammonia in the annular space. There are 40,000 gallons of CaCl2 brine of sp.gr. 1.2 in the system. The brine pump and fan D take 75 H.P. The total power needed is 535 H.P., while the three air compressors use 3 times 671 or 2013 H.P. in place of 3 times 900 or 2700 H.P., as was required with the warm air. The smaller power is due to the smaller volume occupied by the cooler air with small vapor pressure. There is a slight saving in power, but the main saving is in the amount of coke used and in the uniformity of operation; 358 tons of iron were made with 2147 Ibs. of coke per ton originally while 447 tons per day were made with 1726 Ibs. of coke per ton after the installation of the dry blast. This plant was started in August, 1904, and since then a num- ber of plants have been installed. In general the output may be increased by 10% and the saving in coke is 15% when this apparatus is used. Gayley has patented a scheme of passing the air through two coolers in series and using cool liquid to abstract the heat. In this case air is blown in at A and passes up through grids or 322 ELEMENTS OF REFRIGERATION baffles over which a cold liquid such as water falls. The water is pumped by the centrifugal pump C to the top of the tower where it is discharged over brine or direct-expansion coils D, which cools off the water and this flows down over the grids. FIG. 171. Gayley's Two-stage Air Cooler. FIG. 172. Air Conditioning Apparatus. The cooling of air for churches, hotels and auditoriums or for rooms used in some manufacturing process is accomplished in the same way. In this case the air is freed from the pre- cipitated moisture by first passing it through water to wash it and then over a set of baffle plates arranged as in A, Fig. 172, called eliminators for the purpose of removing the moisture. OTHER APPLICATIONS OF REFRIGERATION 323 The figure shows the arrangement of fan B and bunker C. The bunker C contains a number of pipes through which brine is passed to cool the air and precipitate the moisture. The eliminator E removes the moisture. The air enters at F and is passed through tempering coils G and H in cold weather. The washers / consist of a spray through which the air passes. This spray washes the air, taking out the dirt and gases. The upper coils C serve to warm part of the air if necessary. The mixing FIG. 173. Bunker Room. dampers at K are used to get a proper temperature of dis- charge. The air may be cooled by passing it through a spray current of cold water or brine or the air may be passed over a set of revolving discs which dip into a cold-water or brine tank, and when they emerge they are cool and prepared to cool more air. Fig. 173 illustrates another bunker room with vertical coils made up of horizontal pipes and return bends. These are con- nected to two mains. The coils are filled with brine. 324 ELEMENTS OF REFRIGERATION At the Congress Hotel in Chicago a 3oo-ton machine is used in cooling the air and washing it for proper service. At the Luther Memorial Church at Orange, Texas, a cooling plant is used to reduce the temperature from 90 and over to 70. The City Theatre of Rio Janeiro has recently been finished. This building seats 1700 persons with 200 on the stage. Over 50,000 cu.ft. of cold air per minute is introduced to bunker, cooling the air from 95 to 68. This requires 7^000,000 B.t.u. to cool the air and 2,340,000 to condense the moisture. The operation is carried out by 105 H.P. motor operating an S02 compressor. The problem in these cases is to find the amount of refrigera- tion. In the case of the air for a blast furnace the known data consist of the amount of air to be handled per minute, Fi, the maximum temperature T\< the relative humidity of this pi and the condition to which it must be changed TV Weight of air entering = (Bar ~ lpl)Fl =M a .... (8) Bl i Weight of moisture entering = m\ pi V\ = M\ .... (9) Volume of air leaving = - 1 - =2 ..... (10) (Bar p 2 ) Weight of moisture leaving ==W2F2 = M2 ..... (n) Water condensed = M\ M 2 =M C ....... (12) Energy in air above 32 entering = o.24 M a [Ti4gi]=Qi (13) Energy in moisture above 32 entering = Mi [ii] =Q2 . (14) Energy in air above 32 leaving = o.24 M a [T2 491] =Qs (15) Energy in moisture above 32 leaving = M2fe] =Q (16) Energy in condensed moisture = M c q2 f = Q 5 . . (17) Heat removed per minute = 6 = Ci +62 -(Qs +64+65) (18) mi = weight of i cu.ft. of saturated steam; Bar = Barometric pressure ; pi = pressure of steam at temperature T\\ OTHER APPLICATIONS OF REFRIGERATION 325 Ti = absolute temperature of entering air; pi = relative humidity; z'i = heat content of moisture at entrance (superheated); of liquid. For the cooling of buildings it is well to fix the temperature of the incoming air so that when heated to the temperature of the room it will have absorbed the heat entering into the room from the outside and from processes in the room. If the various heat losses through the walls be found from the K's of Chapter V, Heat from walls Q e = 2KF(t a -t r ) . . . (19) Heat from persons Q P = nQ' - . ( 20 ) Heat from machines and lights Qi = 2$46XH-.P.+Q g ni . (21) Now .02V(tr-t e ) .... (22) o.o2=B.t.u. to heat i cu.ft. air i F; V = volume of air per hour; t a = temperature outside air; t r = temperature room ; t e = temperature of entering air. V is fixed by the number of persons in the room. In some cases this is made 1800 cu.ft. per hour per person. This may be reduced to 1200 cu.ft. per sitting in an auditorium where the number is not fixed. The value of V is given by F=i2oo n. . ........ (23) n = number of persons. Having F, t e may be found and the problem is the same from this point as the original problem for the blast furnace. Having the heat removed from air the amount of surface required is given by =^ ....... (24) A/i o '7T A/2 326 ELEMENTS OF REFRIGERATION F = bunker surface in sq.ft; K = 2.2\/w a for wet surfaces; K = i + i.$\/Wa for dry surfaces; Ah = difference in temperature between air and brine at entrance or exit ; Ate = difference in temperature between air and brine at exit and entrance. The capacity of the refrigerating plant Tons of refrigeration = ^ .... (25) 199.2 The brine cooler, condenser and compressor are fixed in the same manner as for any other problem. This method may be used for the air needed and refrigera- tion for a chocolate factory. Rinks. The use of expansion coils or brine coils for skating rinks has been employed in many places. The pipes are placed close together, using about 0.8 sq.ft. of brine pipe or 0.6 sq.ft. of direct-expansion pipe per square foot of rink. The heat to be removed is that from persons, walls, lights and fresh air. Ice Cream. The making of ice cream has become a refrig- eration problem of late years. The use of cold brine for the freezer in place of ice and salt was invented about 1902. The cream when first received is stored in rooms or vats at a temperature of about 33 F. It is allowed to season for about twelve hours and after this it is put into a mixer in which the various ingredients are worked together. The mixture is now taken to the freezer, which may be of the batch or the continuous form. In the Fort Atkinson Horizontal Freezer of the Creamery Package Co., Fig. 174, a seamless German- silver cylinder with a scraper revolving against it has a brine coil of seamless copper pipe around it. The dasher of tinned bronze is caused to revolve in the opposite direction from the scraper. The whole tank is properly insulated. Above the cylinder is the feed tank to gauge the batch accurately. The OTHER APPLICATIONS OF REFRIGERATION 327 arrangement at the end of the feed tank permits one to put fruit in at this point without placing it in the main feed tank. In this freezer the mixture is discharged into the main cyl- inder and the dasher started. The cream is churned and cooled, and as the heat is removed there is a swell of about 69% of the volume, which occurs as the cream passes from 34 Tic. 174. Fort Atkinson Freezer of Creamery Package Co. to 28^ F. It depends on viscosity and the rate of freezing. The swell is due to air being introduced. After 23^ is reached the cream becomes brittle and the dasher will beat down the cream. The cream is not frozen hard in the freezer, but when the swell has occurred it is drawn of! while it is still thin enough to flow slowly and is put into cans and fixed by storage. If the mixture is at 34 when introduced into the freezer it will be necessary to operate the dasher for from twelve to sixteen 328 ELEMENTS OF REFRIGERATION minutes. The cream is now put in a hardening room at o F., where a fan keeps the air in circulation and thus removes the heat to harden the cream in six or eight hours. The old method of submerging the can in brine is not as good as the circulation method. The freezers are made of various sizes, the 5 -gallon size uses f to i H.P. to drive, while a lo-gallon one takes i| to 2 H.P., a i5-gallon, 3, and a 25-gallon, 5 H.P. In a drug-store plant a 3-ton Larsen machine with 5-H.P. motor and a 40-quart freezer with 2-H.P. motor was placed in a space of 2 by 8 ft. and a dry hardening cabinet 3! by 18 by 3 ft. with a cream and fruit storage 10 by 12 by 8 ft. were installed. This shows what a small space is absolutely nec- essary. In computing the heat to be extracted in making cream the following average figures may be used, although there is some' variation from the various flavors of cream. Specific heat of milk o . 90 Specific heat of cream o . 68 Specific heat of liquid ice cream o. 78 Specific heat of hard ice cream . 0.42 Heat of fusion ice cream 80.0 B.t.u. Temperature of hard cream. ... 10 F. Temperature of soft cream. ... 16 F. The first operation is the cooling from temperature of receipt, or if pasteurizing the cooling from the pasteurizing temperature to the storage temperature, after which the heat loss from the storage vat is cared for. The next cooling is from the mixing temperature to the temperature of 34 F., and then the heat to reduce the temperature to 28, after which it is drawn out and stored. Part of the heat of fusion is taken out in the freezer and part in the hardening room. It may be assumed that one-half of the heat of fusion is removed in the freezer. An important application of refrigeration is the Poetsch process for sinking shafts, first used in 1885. This is used OTHER APPLICATIONS OF REFRIGERATION 329 where a shaft has to be sunk through quicksand or where a soft wet stratum has to be penetrated. In these cases the side walls of the shaft would be forced out by the weight above, and to prevent this sheet piling or a caisson may be used, or when these are not possible the ground around the shaft is frozen. To do this a series of pipes is placed in holes left by a drill. This casing is put down and must penetrate the soft stratum. It is usually put down after a drill has bored a hole. By capping the end of the pipe and forcing water out of a small opening in the end of another pipe on one side of the large casing, this may be driven through the soft, sandy stratum by washing the sand before it. After the casing is put down, a separate pipe is put inside and then cold brine is pumped down and allowed to pass up through the annular space between the two pipes, removing heat from the damp earth, and freezing it into a solid wall, as shown by dotted lines in Fig. 175. In the Gobert system liquid ammonia is allowed to vaporize in a large casing, removing heat from the ground around. To compute the amount of heat to be removed the tem- perature of earth must be found and its weight determined. The specific heat is 0.2. The amount of water to be frozen must be determined by drying out a sample of the earth of known volume and then the heat abstracted is found by using the general values of specific heats of water and ice and the heat of fusion of ice. The brine will freeze the earth for about i yd. from the pipe with the ring of pipes and half that distance on the outside with o brine, but the cooling will extend about 2 yds. beyond. This cooled layer repre- sents the heat insulator and the heat carried across this area represents the heat which must be supplied to keep the ring frozen. The heat transmitted from zero brine amounts to about 85 B.t.u. per sq.ft. per hr., according to Lorenz. The time taken to do this may be months, and for that reason a non-conducting house should be built around the top of the cooling pipes and the brine pipes must be carefully covered. 330 ELEMENTS OF REFRIGERATION IJlf g, OTHER APPLICATIONS OF REFRIGERATION 331 The sections of the heavy outer piping are joined on the inside, while the inner pipe is connected by ordinary couplings. Another use for refrigerating machinery is the cooling of drinking water. This has been demanded in hotels by guests, and in factories it has been required by the manu- facturer on account of the effect on the workman, by the workman for his bodily comfort, and by the legislature in laws for the bettering of working conditions. Of course this may be done by ice placed against cooling coils and ice put into the old-fashioned water cooler made of a barrel with a faucet, or the older pail and dipper, but the most hygienic method is to send filtered water through a brine or direct-expansion water cooler, then through a circuit of insulated pipe to the cooler again, taking off sanitary fountains at intervals. Dr. Thomas Darlington states that about 3^ pints of water should be drunk daily to care for water given off from the body. This water is necessary to aid digestion, to carry away waste and to properly regulate the actions of the body. The amount of water required varies with the amount of muscular exercise and with temperature. He states that the temperature should be about 50, as ice water is apt to produce cramp and water that is not cool is so unpalatable that persons wiD not drink sufficient of it. At the National Tube Works water is cooled to 45 F. in summer and to 50 F. in winter. The water should not be carried in lead pipes, to avoid the danger of lead poisoning, and the endeavor should be made to filter the water to remove bacteria and sediment. Filtration makes the water attractive. The use of the drinking-cup common to all men should be discontinued, because of the easy transmission of disease thereby. A large drinking-water cooling system has been installed by the National Tube Co. in Pittsburgh at their Continental Works. The plant supplies fountains for about 1000 men, one fountain being used for each thirty men. These fountains must be located at convenient points, so that the men will drink, and so that the drinking will not consume too much time. The distri- 332 ELEMENTS OF REFRIGERATION bution is made through 15,000 ft. of ij-in. galvanized steel pipe covered with ij ins. of Nonpareil cork. The temperature rises about 7 in passing the circuit. The line loops down at each drinking-fountain, Fig. 176, as shown by the Nonpareil Cork Co. in their bulletin. In this way a continuous circuit of cold water is obtained so that there is always a discharge of cool water when the faucet is opened. The water from the city filtration plant is first passed through two charcoal and gravel filters and then to a tank FIG. 176. Drinking Fountain. containing direct expansion coils, reducing the water to 45 in summer and 52 in winter. It is passed by means of a pump through three lines leading to all parts of the mill. The in- stallation uses a lo-ton refrigerating machine for this plant. The amount of water, including waste, varies from about i gal. per man per day of ten hours in winter to 2\ gallons in summer. The cost of this plant was $1.82 per employee per year against about $5 per man when ice and water tanks were used with the loss of men's time from sickness due to cold water. The system cost about $9000 to install. In planning a system, \ gallon per hour per person should OTHER APPLICATIONS OF REFRIGERATION 333 be allowed to cover all wastes for summer use with hard mus- cular labor. In less active work . this might be decreased to i or TO gallon. In carrying this water a study must be made of the cost of pumping, which decreases with the size of pipe; the cost of heat loss through the insulation, which increases with the size of pipe; and the yearly cost of the covering and pipe for interest depreciation, taxes, and insurance, which o- Various Mains -O -0 (-8-/J Fountain pply Ammonia Compressor Motor ^Cork Insulation FIG. 177. Diagram of Drinking Water Plant. varies with the size of pipe. The first demands a large pipe, the second and third a small pipe. The yearly cost of several pipes should be figured, and that requiring the smallest cost used. The Nonpareil Co. recommend a velocity of about 3 ft. per second, which is considered in Chapter X. This figure may be used as a starting-point. A low velocity pre- vents the disturbance of any sediment in the pipe. The piping, of course, is arranged in a loop from the cooling tank back to 334 ELEMENTS OF REFRIGERATION the tank. The fixtures are connected to the main flow pipe, as no dead ends are used. Long sweep elbows and bends will reduce the cost. The pipe may be covered by special ice-water pipe covering of Nonpareil cork ij ins. thick and specially made for this service. The heat required for such a system is made up of two parts : (a) the heat to cool the drinking water to 45 F. in summer and (b) the amount to care for the radiation from the pipe 3.00 U 16 Pipe size in inches FIG. 178. Heat Loss per Lineal Foot of Pipe per Hour per Degree. covering. This latter should be such that the water is only warmed 7 in circulating through the pipe. This temperature is fixed by the length of circuit and the size of the pipe. The cork covering has been tested as shown in Chapter VI, and methods of that chapter may be used to compute the loss or 0.36 B.t.u. may be taken as the loss for i in. of thickness per square foot of cork surface at mean circumference per hour per degree difference in temperature. The loss from plain pipe is 0.8 B.t.u. per square foot per hour per degree dif- OTHER APPLICATIONS OF REFRIGERATION 335 ference. The heat loss is given in curve below for ice water thickness of cork, Fig. 178. Water needed per hour ,, o. 25 X No. of men at one time. , f N M w = a- -X62.4. (26) 7.48 Heat loss from pipe in any circuit = H XL, . . (27) # = heat loss per foot of pipe from curve for assumed diam. pipe; L = length of pipe. Heat loss in water flowing for 5 rise = M e X 5 . . (28) Hence the weight of water circulated to care for heat loss is given by : '. ' : ^=Y- -' V". . . . (29) The area to allow for a 3 ft. per second velocity is given by pf,+M c = J F p X3X36ooX62.4 = 673,92oF P . . . (30) F p = interior cross-sectional area of pipe in square feet. The area thus found must check with that assumed for (27) and (29) and if it does not the assumed size must be changed. Heat loss in pipes = Q p = 2HL or 2 M c X 5 . . . (31) Heat to cool water entering = Q v , = M to (q i qo). g = heat of liquid at temperature of city supply (80); go = heat of liquid at outlet temperature (45) F. Heat loss from tanks = Q t = FK(t r -to) . . . . (32) F = area of surface of tank ; K = coefficient of transmission; T T = temperature of room; To = temperature of water in tank. 336 ELEMENTS OF REFRIGERATION Heat equal to work, Q f = 778 h = friction drop in system. Tons of refrigeration = 60X199.2 . (33) (34) FIG. 179. Methods of Covering Pipes and Fittings with Nonpareil Cork. Fig. 179 illustrates the section of cork covering of various fittings and pipe, and Fig. 180 the insulation of an ice-water tank. This covering is made of boards of compressed cork OTHER APPLICATIONS OF REFRIGERATION 337 and to fit around pipes the cork is molded to form and where separated sections come together, a waterproof cement is used to make a tight joint. The sections are held together with four copper-covered steel wires. The pipe sectional coverings are put in so that the half sections break joints as shown. The outer surface is painted with an asphaltic paint and cavities are filled with brine putty or granulated cork and paraffin. Fig. 181 illustrates the arrangement of the ice-water plant of a large office building or hotel. The ,7-2 "Cork Hoards .Granulated Cork or Brine Putty -Flanges -Wire 4 Segments of Cork Board FIG. 1 80. Armstrong Covering for Water Tank. centrifugal pump, A, forces the water through the closed sys- tem. The filter B is used to supply fresh water to the cooler C, which is cooled by the direct-expansion coil or by brine around the water coil, which gives up its heat in the brine cooler. A closed system must be used in high buildings to balance the great static head, so that the pump will be re- quired for friction only. In chemical works the use of refrigeration to remove heat is similar to that for water cooling or chocolate making. There is nothing special in the methods of calculation. The quan- tities required are ; 338 ELEMENTS OF REFRIGERATION (a) Heat loss through walls. (b) Heat from persons. (c) Heat from motors. (d) Heat of vaporization to condense vapors in process. (e) Heat to cool liquids in process. (/) Heat of fusion to solidify liquids in process. FIG. 181. Drinking Water System in Hotel or Office Building. The sum of these quantitites gives the heat to be removed and consequently the tonnage. The surface to abstract this heat is then found by fixing the temperatures on the two sides of a cooling surface and obtaining the coefficient of heat transfer. The problem is similar to any of the others. OTHER APPLICATIONS OF REFRIGERATION 339 The application of refrigeration to the manufacturing of photographic supplies and to oil refining has demanded large installation. Another use is to prevent chemical action by lowering the temperature of ammunition holds of war vessels. The application of refrigeration to the dairy is shown in a cut from the Remington Machine Co. in Fig. 182. In this the apparatus used in a dairy is shown with the refrigerating machine near the office. The direct-expansion pipe used in the cold-storage room and in the cooler is not shown. The cold- FIG. 182. Complete Dairy Plant, 3o'X48'. Remington Machine Co. storage room is necessary to care for the milk and cream properly. The apparatus of the Creamery Package Co. shown in Fig. 183 gives the requirements of the modern creamery. The ammonia compressor draws the ammonia from the brine cooler placed in the storage room or above it, the liquid being delivered to the cooler from the condenser by an expansion valve. The oil trap on the line from the compressor to the condenser is marked as well as the liquid receiver below the condenser. The brine pump circulates the brine from the brine tank to the pasteurizer and wizard back to the cold-storage 340 ELEMENTS OF REFRIGERATION room. The milk is placed in the receiving vat and after reaching the proper temperature it is passed to the separator and from this the cream is passed to the pasteurizer and then to the wizard ripener, where it is allowed to age before being sent to the churn. It may be necessary to cool the cream in the pasteurizer or wizard, and for that reason these are connected by pipes to the brine system. For storage of butter, cream or milk a cold- storage room is used. Another application is to the manufacture of liquid air. It is known that the throttling action of perfect gases occurs FIG. 183. A Modern Creamery. Creamery Package Co. at constant temperature because the heat content, which remains constant under such action, is a function of the temperature. However, there is no truly perfect gas and consequently when gases are throttled there is a slight drop in temperature known as the Thompson- Joule effect. Tripler, Hampson and Linde used this effect to obtain low temperatures. Linde machines have given the best results and are shown in Fig. 184. In this system a two-stage air compressor is used. One stage compresses atmospheric air to 240 Ibs. per square inch pressure and the other stage to 3000 Ibs. per square inch. The atmospheric air is com- pressed in the first stage and sent through a coil around the cylinder A placed in the jacket where it is cooled before going OTHER APPLICATIONS OF REFRIGERATION 341 to the second stage. The air there passes through an after cooler around the second stage B, Rafter which it enters a separator C for oil and moisture. It then passes through a coil Z>, where it is cooled and then enters the inner pipe of a coil of three pipes E. In this coil the air is cooled by a current of low-pressure air which has been cooled to a low temperature, so that when the air reaches the end F of the coil it is quite cold. It is here allowed to expand from 3000 to 240 Ibs. by the valve G and as a result its temperature should be lowered 203 C. FIG. 184. Linde Liquid Air Machine. The incoming air could be cooled to 136.5 when the throttling is from 3000 Ibs. to 240 Ibs. per square inch absolute. Aooo 240 i -/ 2 = 0.276 - 1 \i4-7 i4'-7 273 = 203 (35) Of course the air could not drop so much and the heat required to keep the heat content constant means that part of the air must be liquefied. Part of this air at 240 Ibs. is throttled to 14.7 Ibs. by H and is then sent out to the atmos- phere through the outer annular space to 7. The amount left between G and H is four-fifths of the total air, and this is sent * Equation for Thompson- Joule effect. 342 ELEMENTS OF REFRIGERATION back through the first annular ring. This air is at 240 Ibs. per square inch and is taken to the intermediate receiver of the compressor. This air is cooled in the coil surrounding the cylinder B and the coil around D removes some of the heat from the high-pressure gas. When the machine is started the air leaving at G and H may not liquefy, although there is a drop of 50 C. and this cools the next lot of gas, which of course drops to a lower temperature and soon liquid air appears. In this apparatus the liquid air which forms is collected in the vessel L. The air is at a low temperature, corresponding to the boiling temperature at atmospheric pressure. These low temperatures may be used for any abstraction of heat to tem- perature at a little above that of the air, the liquid boiling away as the heat is abstracted. CHAPTER IX COSTS OF INSTALLATION AND OPERATION TESTS THE cost of equipment, supplies, fuel and labor will vary from time to time and the figures given in this chapter have been collected, through the kindness of many manufacturers, as a guide to the student in determining cost of apparatus and manufacture. They should be used as guides only on ac- count of the fluctuation in prices. They were compiled in 1916, but prices in use before the outbreak of the European war were employed. Land. The cost of land will vary with the location in a city and with the city. In the outskirts of small towns it may be worth from i cent per square foot or $400 an acre to 5 cents a square foot or $2000 an acre. In a small city this will vary from $1000 an acre to $12,000 an acre, near the railroad. This latter price is about 30 cents per square foot. In the business districts of large cities $25 per square foot has been paid. Buildings. The cost of buildings will vary with the type of structure. There are a number of variable units which enter into the problem and unit costs of various parts of a struc- ture are given. For preliminary estimating the total cubic contents of the building, including cellar, may be found and then a unit cost selected from the table below is used to find the total cost. This is known as " cubing the building." . COST OF BUILDING PER CUBIC FOOT, UNINSULATED Office Buildings Frame 10 cts. per cu.ft., $1.00 per sq.ft. floor Brick and timber 13 1.25 ' ' Brick and steel 20 " i . 75 " Reinforced concrete 20 ' ' i . 75 " 343 344 ELEMENTS OF REFRIGERATION Storehouses Frame 6 cts. per cu.ft., $0.60 per sq.ft. floor Brick and timber 8 0.80 Brick and steel 12 1.20 Reinforged concrete 12 1.20 Power Houses Frame 9 cts. per cu.ft., $0.90 per sq.ft. floor Brick and timber n i.io Brick and steel 15 1.50 Reinforced concrete 15 1.50 UNIT PRICES OF BUILDING ELEMENTS Excavation and Hauling Earth $ . 30 to . 50 per cu.yd. Rock i . 50 to 3 . oo ' ' Masonry Ordinary brick 33 cts. per cu.ft., $8 .91 per cu.yd. Rubble stone 22 6.00 " 1:3:5 concrete 22 6.00 " Reinforced concrete 37 " 10 . oo " Concrete forms $3 . oo to $5 . oo per cu.yd. Brick chimneys $13 . oo per cu.yd. Fireproofing 20 cts. per sq.ft. Steel Work 5 cts. per Ib. Lumber Heavy Georgia pine timber $50.00 per M bd. measure Georgia pine joist 40 . oo " Spruce joist 34 oo " Yellow pine boards 25 . oo " Spruce boards 32. oo Ship lap, pine or spruce 26 . oo l ' Clapboards, pine or spruce 32 . oo " Cypress boards 60 . oo Yellow pine flooring, vertical grain, " 50.00 per M Oak flooring, |" 70.00 " Maple flooring 50 . oo " Shingles 2 . 50 to 5 . oo per M Lath (10 cts. per sq.yd. wall) 4-65 Studding, 3 / 'X4 // and 2"X4" spruce 30.00 per M Carpentering Allow from one-half to full value of lumber for labor. Plastering Lime and hair 30 cts. per sq.yd. COSTS OF INSTALLATION AND OPERATION TESTS 345 Floors and Roadways Asphalt facing, i" $i . 20 per sq.yd. Concrete sidewalks , $i . 80 Concrete roadway, 6" o . 70 Macadam roadway, 6" i .00 Brick roadway 1.75 Asphalt roadway 3 . 50 Concrete fireproof floors 18.00 per cu.yd. o . 60 per cu.ft. Partitions Tiles 4" thick (i 2 "Xi2") 5 i cts. per sq.ft. 8" thick (i 2 "Xi2") 10 Labor equals cost of tile. Roofing Copper roofing $25 . oo per square (100 sq.ft.) Slate roofing $10 .00 " Tin roofing 7 . 50 ' ' Slag roofing 4 . oo " Book tiles, 2" 07^ per sq.ft. 3" _ 08^ " Rain conductors, tin .12 per ft. Copper .35 " Mill Work Windows with sash and trim $8.00 to $12 .00 Outer doors and frames 25 . oo to 100 . oo Inner doors and trim S.ooto 15. oo Base boards 08 to .16 per lin.ft. Stairs 2 . oo to 10 . oo per step Plumbing Water-closets $25 . oo per unit Wash basins $12 .00 per basin Urinals 25 .00 per stall Soil pipe (iron) 25 per ft. Painting White lead and oil 38 cts. per sq.yd. for 3 coats Mineral paint 24 " " Asphaltum 35 ' ' " Whitewash 15 " " 2 " Insulation Building paper . . . . $2 .00 to $8.00 per roll of 500 sq.ft. Asbestos, loose . . . .' $1.25 to $2.25 per 100 Ibs., filling 3 cu.ft. 85% magnesia $2.00 to $3.00 per 60 Ibs., filling 3 cu.ft. Hairfelt i" thick 06 per sq. ft. 346 ELEMENTS OF REFRIGERATION Cork boards: Walls. 2" thick on brick or wood walls with cement finish, erected. 25 cts. per sq.ft. 2-2" thicknesses, 40 cts. per sq.ft 1-3" " 30 2-3" " 60 Add 8 cts. for cork partition with two sides plastered. Floors. 2" cork board in asphalt, 3" concrete top on asphalt cov- ering with i" surface, 34 cts. per sq.ft. Same with 3" cork, 40 cts. per sq.ft. 2-2" layers, 50 cts. 2-3" layers 60 cts. Ceilings. 2"of cork on concrete or wood and \" cement plaster, 27 cts. per sq.ft.; 3" cork, 32 cts.; 2-2", 43 cts; and 2-3", 64 cts. Granulated cork: Unscreened granulated cork . . $70 . oo per ton. ^o rescreened granulated cork ... 60.00 " /o granulated cork 35 . oo " Coarse regranulated cork 45 . oo ' Fine regranulated cork 35-o " PIPE COVERING CORK (NET) COST PER FOOT. COST PER FITTING. Size Pipe. Standard Brine Ice Water Cold Water Standard Screwed Fittings. Standard Flanged Fittings. Thick- Thick- Thick- 1 ness. ness. ness. Ells. Tees. Valves. Ells. Tees. Valves. Flanges. } $0.34 43 $0.27 34 $0.24 30 $0.46 54 $0.50 .63 $0.54 7i $2 . 2O 2.20 $2.60 2.60 $3-05 3-05 $0.76 76 i 54 43 39 7i 79 .87 3.05 3-50 3-90 96 ij .63 50 45 79 .88 .96 3-50 3-85 4-30 I . IO it' .71 57 Si .88 .96 i .04 3-90 4-30 4.90 1,24 2 .80 .64 57 .96 i. 08 1.23 4-35 4.90 5-50 1.36 4 I . 21 97 .87 i. 60 1.79 2.08 7-30 8.15 9. 20 2.05 6 1.70 1.34 2.00 2.30 3-02 II . IO 12.05 13-50 3.05 10 3.40 2.70 3.45 21 .30 42 .00 20.85 28.90 41.90 5.60 16 4-30 3-18 23.55 32.30 39-75 55.90 71 .00 6.80 PIPE COVERING, 85% MAGNESIA (NET) COST PER FOOT. COST PER FITTING. Size Pipe. ij Ins. Thick. 2 Ins. Thick. Elbows. Tees. Valves. I $0.13 $0.21 $0.08 $0.09 $0.14 2 .16 25 .09 .11 15 3 .19 .29 . 12 14 .16 4 .22 34 15 .16 .38 6 .28 43 33 .40 .70 IO .42 .60 .90 . I- IS i-55 COSTS OF INSTALLATION AND OPERATION TESTS 347 Machinery Costs. These costs are made up of various items listed in the tables which follow. The prices represent average cost prices with discounts taken off. The items are for indi- vidual machines, but for complete equipment Mr. Thomas Shipley gives the following as a guide for the cost of ice plants per ton of ice-making capacity when they are at least of 50 tons capacity. Compression can system $550 per ton Compression block system $$(? Compression plate system (direct expansion) 800 Compression plate system (brine) 1000 Absorption can system 500 The yield of these plants will be 7^ to 10 tons of ice per ton of coal in distilled-water can plants, 10 to 35 tons in raw- water can plants, and 10 to 15 tons in plate plants. Refrigerating Plants. Cost of Mechanical Equipment: Plants of 50 tons and over $150 to $300 per ton of refrigeration Plants of 8 to 20 tons 250 Plants of 3 to 8 tons 300 Plants of i to 3 tons 250 Efficiency of Apparatus: Boilers 60 to 80% Producers 60 to 80 Steam engines (indicated thermal) : Non-condensing: Simple 6% Compound 10 Unaflow. ii Corliss 9 Condensing: Compound 20% Mechanical efficiency of engines. 85 to 95% Steam turbines (overall thermal) : Non-condensing 6% Condensing, small 8 Condensing, medium 10 Condensing, large 21 Gas and oil engines: Indicated thermal efficiency 25 to 35% Mechanical efficiency 85 Compressors: Mechanical efficiency 85 to 95% Volumetric efficiency 88 348 ELEMENTS OF REFRIGERATION Fuels: Crude Oil: Heating value per Ib IQ,OOO to 20,000 B.t.u. Weight per cu.ft 50 Ibs. Cost per barrel of 42 gallons $i . 50 Gasoline: Heating value per Ib 20,500 B.t.u. Weight per cu.ft 50 Ibs. Cost per gallon 20 to 30 cts. Bituminous coal: Heating value per Ib 13,800 B.t.u. Weight per cu.ft., loose 50 Ibs. Cost per ton of 2240 Ibs. at mine $i . 55 Cost of freight for 300 miles i . 90 Anthracite pea coal: Heating value per Ib 13,400 B.t.u. . Weight per cu.ft., loose 56 Ibs. Cost per ton of 2240 at mine $2 . 65 Cost of freight, 200 miles i . 60 Anthracite buckwheat coal : Heating value per Ib 12,800 B.t.u. Weight per cu.ft 56 Ibs. Cost per ton of 2240 Ibs. at mines $i .85 Cost of freight, 200 miles i . 50 BOILERS AND SUPERHEATERS. EFFICIENCY 65 TO 80% COST or BOILERS BOILER HORSE-POWER (10 SQ.FT. PER H.P.). 50 100 200 300 400 500 Return tubular $ 760 $1120 $2OOO $2800 Water tube I ^OO 2300 3600 4700 $5700 $7500 Superheaters, 10 to 15% of boiler surface for 100 to 120 F superheat 600 600 IOOO 1300 1500 1600 PRODUCERS. EFFICIENCY 60 TO 80% COST OF PRODUCERS H.P. Cost. 80 $1600 IOO $1800 150 $2200 200 $2500 250 $2800 300 400 $3200 $3800 Producers are based on 1.2 Ibs. of coal per hr. per H.P. to burn 9.4 to 10 Ibs. of coal per sq.ft. per hour. Grate areas of size COSTS OF INSTALLATION AND OPERATION TESTS 349 ENGINES AND TURBINES Steam consumption of engines per I.H.P. hour: Simple non-condensing 24 to 40 Ibs. Compound non-condensing 2 1 to 36 Compound condensing 14 to 20 COSTS CORLISS ENGINES, SIMPLE (100 Ibs. per sq.in. gauge) Indicated H. P.. Size 20 8X18 40 10X30 70 12X30 100 14X36 150 16X36 200 18X42 300 22X42 Cost $1000 $1200 $1500 $1900 $2150 $27OO SltjOO CORLISS ENGINES, COMPOUND (125 Ibs. per sq.in. gauge) Indicated horse-power Size IOO 10 and 18X36 600 20 and 36X42 1000 26 and 50X48 Cost Tandem $3000 Cross $10,000 Cross $2O,COO HIGH-SPEED ENGINES Indicated horse-power. . . Size 47 to 107 10X10 75 to 162 12X12 87 to 189 13X12 107 to 240 14X14 185 to 390 18X18 Cost belted $7 5 5 $080 $1015 $1260 $2510 Cost, direct connected . . IO2O 1270 1375 1617 3000 Piston speed from 550 to 650 ft. per min. Steam pressure, 80 to 150 Ibs. per sq.in. gauge. Mechanical efficiencies, 85 to 95%. Steam consumption, 29 to 35 Ibs. per I.H.P. hour. TURBO-GENERATORS Capacity in K.W. Cost 25 D.C. $l-27tr loo D.C. $3800 150 D.C. $(T2OO 200 D.C. $6200 loo A.C. $4100 200 A.C. $ II^O 1400 18^0 24.OO ELECTRIC MOTORS (B.C.) Efficiency 85 to 95% Horse-power 7! I C 25 5 75 IOO 150 200 Cost $213 $290 $450 $605 $7i5 $1225 $1290 $2400 SWITCHBOARBS SWITCHBOARDS FOR B.C. GENERATORS Capacity in amperes 12< 2^O 37C =500 75 IOOO Cost $69 $ 7 8 $78 $87 $155 $175 Voltmeter, ammeter, rheostat, main switch and fuses. SWITCHBOARDS FOR A.C. GENERATORS Capacity in amperes 100 " 200 Cost $125 $150 (Ammeter, voltmeter, exciter field switch, exciter and generator rheostat mounting, triple pole main switch and fuse.) COSTS OF INSTALLATION AND OPERATION TESTS 351 AMMONIA COMPRESSORS Mechanical Efficiency 85 to 95% Capacity in tons of ice 2-ton refrigeration = i ton ice. 2 5 10 25 50 $3400 5000 6500 IOO 2OO Cost of compressor (belt drive) Cost of compressor and simple engine .... Cost of compressor and compound engine. $550 730 $700 1150 $1150 1800 $1850 2675 4550 $8,700 10,670 13,750 $17,950 21,160 27,500 AIR COMPRESSORS Mechanical efficiency of compressor and motor 85%. Efficiency of system from compressor motor to air motor 40%. Free air in cu.ft. per min Diam steam cylinder inches 55 6 no 8 250 IO 350 I 2 Diam air cylinder inches . 7 Q 12 14 Stroke, inches. 6 8 IO 12 Price of engine compressor, governor and unloader $^2O $700 $1080 $1500 Price of belt-driven compressor with un- loader 270 400 64O O4O Max. pressure by gauge in Ibs. per sq.in. . IOO IOO IOO IOO PUMPS Direct acting for boiler feed, brine, or aqua ammonia. Mechanical efficiency, 75%. Steam per I.H.P. hour, 100 to 400 Ibs. Gallons brine per minute Size in inches for brine (Simplex) . Cost IOO 6X6X7 $170 250 8X8X13 $260 500 12X12X20 $?7O IOOO $870 Weight in Ibs 800 1660 4OOO 8650 Boiler horse-power GO IOO 42^ IOOO Size in inches for boiler feed (Simplex). 5X2|X6 e V^iV? 6X4X12 .9X6X13 Cost $00 $IIO $1 SO $2^0 CENTRIFUGAL PUMPS Mechanical Efficiency 60% Gallons per minute IOO 2 so soo IOCC Speed 1800 1800 2OOO 1600 Horse-power 7 ^ J C 2 S CQ Weight in Ibs CQO 72C ooo i soo Cost without motor $180 $190 $27O $330 Pressure in Ibs. per sq.in IOO IOO IOO IOO 352 ELEMENTS OF REFRIGERATION AIR LIFT PUMP Mechanical Efficiency 40% FAN BLOWERS Mechanical Efficiency 60% Capacity at i oz. in cu ft per min 2OOO 4OOO 8OOO 16 ooo 26 ooo Diam. wheel in inches. Cost 15 $I2O 21 $IOO 30 $27O 4i $400 53 $600 64 $800 :>4,uuu $11 H<2* o^rntoo NO, N MM - ]J M Tj-0 0\ M 00 00 roo Oi t^- o oi in Oi 0000 OO ro t ro ro 00 t^ O t^OO 00 00 01 00 01 ro mo t>- 01 00 t o 8 < Oi |.s ON OiOO tO 00 t m Ol 01 01 m ino ino ro ro ON M o t mo 01 o O ro O 01 tO ro I>O 01 O O 00 t- 2 M ***+ O\ 01 m o> t t moo 01 o ro t m t^ O\ M 01 "rt t t- s Jfi ft m moo o roo O\ m ro t to t mo t- t- t- t *o tf i hS^ M M M M M N M 01 ro ro ro 1 C iu OlOt-tONON MinOlMOl o o t^oo o O m ro o r- ro mo oo 01 M m O ro t^ %% ex II O W~ M M M M M 01 o< 01 ro ro rot J) o fj oOoOMOro t mtt S*5*3 in m EH S^ a "3 111 1 1 ro t 00 M t^-00 t^O O\ W 01 too MOO Ol ro tO 00 O rOO O t t-ooo oo m tN o t o mo mo m ro 01 r^ O\ O 01 00 ro M O O OiOO m Ol *Hr H^MM w -1- -1C, lill H 356 ELEMENTS OF REFRIGERATION IH ' 4 ffi N IO t^- O PO M O OO o' pi 4 o co MMMNP.J >IPE )OT OF "c3 ill NO O ON POOO r-Tj-o O ON O O HI to ONO oo t> PO Tt N PO C ' PO HI 1 VQ H *** i B ^tl V "S 3fc yC/2 PO t- to T}- ro rf O O toO ON r^ to rj- PO O M N O\ PO O O PO o o>oo o to i ill O HI ONPO-* 00 O M PI M M PI PO rl- 00 PO N IO PO Tt ONOO OiOO O 00 O Tf N N IO IO o t- <* M to PO "0 4o oo at c & " PO 00 ON HI N POO PO PO IO O HI M tt M tt-io 1 rOO O>O o PO r- tortO>0 IOOO Tj- M Ol e^ MMNTt O oo M oo to 2 External Square. Inches. ON ONOO Tj-O PI PI IO tOO M Pi PO tOOO 00 Tj-10 N too PO PO ON ro HI 00 Tf T}- O to O\ PO ^t O\ N to T}- Tfr M M PI PO M u 11 Tt N N O HI O ONPOI-PO 00 O T}- ro ro 'aolo O N" to C> to O Tf 00 rt Oi NO to ON HI H H M M M M N N POTj-o r- C\ O HI 1000 i o 11 N O HI ON ON t- ON N PO ON M IO O\ HI N PO M O O PO M N ONTt-0 O O t- t- PO O\O PO t^ M OMO M Tj-00 SMM-M-S 1 Wire Gauge Number. ci M o ONOO t^HM 00 ION HI O O O I, 8 N N Tf to oo ovo NOO ^^^5 H*"* Actual Internal Inches. 10TJ-M PIO O ON N Tf PO N N Tfior- M N Tt- PO IO ON P* Tf ON PO N 00 OO PO OMOM M 10 oo POOO oo r- N PO PO 4 10 H ill to to Tt-OTj-lO Tj-lOO OO O to to to MO t* r- roO drooo O N 10 10 IOO Q M HI M HI N PI PO Tj- TfioO Nominal Internal Inches. H^*** M M M N N HW POPO-O Tf PO 41; .. too a POO O N Oi IO * O ro O ONOO ISiH liSSs POOO M M M N rj- too OO M M tSsss M N Tfio t^ IOO N 00 100 too PO IOOO PO M 00 M PI P| N MO * PO ON N O O Tj-O ON N to M M O N O t* PO Tj- Tj- -< M POO fej . O M w PO OO : : : : ^^^^ o t^ I> J~- 00 M v ' O WfrOWW M H5 ^^^ ^ ^^^^^ O q POO O* O OOMOOO M O MMMM P)P) -^ V V ^ V c^ : ; ; ;M" ^'oV^o %M R3 : : ;o o,~ooo o o M M M MM 00 OOOMM-* M v 55555 555 -**5 -*5 ^ ; ; ;o ~b\ooo"b M * "b -V"> -ys:?3 V- S . - M m ' [ ) O OOO O O O O eu %*"> 2 o^<*^0 : : : ri : : : :^ ^ ^ ^ v ^ pi 15 > cS oo ^ ^ o o o M c\ Jfv 5 i 5 "b"b O O H-He.Hl-W O HI : : : : -,o 0,0 <-> MM -.^ ^^tts l?s ^ >,Q 5^555 5^^^v MO OOOoO^* Or^oOO\O Mr-i fo POPOPO -0 O it; H-H5 5 ^ HC< 555 55 rt M M Q g'c si : : : 5 s3sl S S s, -NHc.5 H Hc.^5 5 5 ^ SJ M o aJ^ SslZ o c-r o <-< r^HH U3 (UQHH oJS M POOO 10 l-l TfO MM >O 00 M" POO" d * M" M" t^ - "POO "bv'bv'pO 5 c*e*MHe.5 H5 "io"iO*ioV-~Ov ^ ^ v ^ v ^ ^ HI O t- O PO O * M M M M M M PO a 5 5 nl<5 00 K s I XXXXX XXXXX XXoo 8 3 M ^ J tH 10OOO-K.HN O O TtO HM TtO "* MPO MMMNOO PO <*),& MM IN s : : ^ tJ^^t: v O fe M M PO PO PO ^ IO s 2 6 to g oi-* '^ ^ "-! X M ^-\Q OO HI Tf t^- O rfO Ot-C\ MMMM M t- 10 O MM 0) 10 COSTS OF INSTALLATION AND OPERATION TESTS 359 T FIG. A. York Compressor. 360 ELEMENTS OF REFRIGERATION PARTICULARS OF " DE LA VERGNE " STANDARD HORIZONTAL AMMONIA COMPRESSORS ONE COMPRESSOR WITH SIMPLE ENGINE AND Two COMPRESSORS WITH COMPOUND ENGINE Capacity, tons of ice melted per 24 hours * 25 35 50 75 IOO 125 150 200 Diameter compressor cylinder, ins 10* "1 I3i I4s 16 18 20 22 Diam. steam cylinder, ins. . . . IS 17 19 20 22 26 26 32 Stroke, ins 18 20 22 26 30 33 33 36 R.P.M. 63 65 62 68 65 58 16 c*7 Rated H.P. 45 60 85 130 I7O 215 o u 255 O / 34O Dimensions main bearings, ins. Diameter crank pin ins 6iXu 4* 7Xi2i 4i 8X15 5* 9Xi5 Si IOXI8 6 II X20 7 12 X22 7i I3 8 X i 24 Diameter cross-head pin, ins. . . 3 3i 4 4i 4* If Si si Steam pipe, ins. 3 3 4 4 5 6 o n Exhaust pipe, ins 4 4 6 6 6 7 8 9 Ammonia suction, ins 2 2i 3 3 4 4 5 5 Ammonia discharge, ins 2 2 2i 3 3 4 4 5 Diameter flywheel, ins 96 IOS 120 128 136 144 160 1 60 Weight, do, Ib 5OOO 60OO 7OOO 9000 10,500 14,000 17,000 19,000 Length over all. 13' 10" IS' l" i6'3" 1 8' <;" 2 l' 2 fr 22' 7" 24' 7 /f 27' V Width over all. 8' 6" 8'o" 9' 6" / // no II' 2" 12' 6" 12' 6" i / ISI I Height above floor 6'o" 6' 5" 7' i" 7' 7" 8' 2" 9' 3" 9' s" 10' o" Capacity, tons of ice melted per 24 hours * Diameter compressor cylinder ins Diam. steam cylinder, ins Stroke, ins R.P.M Rated H. P Dimensions main bearings, ins. . Diameter crank pin, ins Diameter cross-head pin, ins. . . Steam pipe, ins Exhaust pipe, ins Ammonia suction, ins Ammonia discharge, ins Diameter fly-wheel, ins Weight, do. Ib Length over all Width over all Height above floor 250 300 250 300 400 500 600 24 26 2-18 2-2O 2-22 2-24 2-26 34 36 24 & 48 27&S4 2Q&58 32&64 34&6S 40 48 33 33 36 40 48 54 45 58 56 57 54 45 425 Sio 440 525 700 875 1050 14X28 16X28 14X28 IS X28 17 X30 18X34 20 X36 9 9i 12 I2i 13 *3i IS Si 9 41 Si Si Si 9 7 8 5 6 7 7 8 10 10 14 15 16 18 20 6 6 6 6 7 8 9 5 6 5 5 6 7 8 174 192 160 160 174 192 216 23,000 40,000 19,000 23,000 26,000 40,000 50,000 29' o" 33' o" 34' 5" 38' o" 40* 2" 43' 4" 47' 4" 1 6' 6" 1 7' 6" 12' 6" 12' 6" 12' 8" 13' 0" 13' n" 10' 7" II'O" 10' 8" II' 0" n' 7" 13' 0" 12' II" * The ice-making capacity of these machines is from 50 to 60% of this rating. FIG. B. De La Vergne Compressors. COSTS OF INSTALLATION AND OPERATION TESTS 361 BRUNSWICK REFRIGERATING AND ICE MAKING MACHINES COMPRESSOR DATA COMPRESSORS WITH STEAM ENGINE DIRECT CONNECTED * is spunoj 'a^ajd -UIOQ ap^s H 3 IH PUB JossaiduioQ pa^oauuoQ ^oaaiQ tot^OOOiooto NOTE. Complete J-ton compression side with automatic expansion valve mounted on pedestal, ready for connection to coils, overall dimensions: 32 ins. long, 22 ins. wide, 38 ins. high. OO fOPOPOO^^ttOW M" 00 M spunoj puB JossaiduioQ OlOOOOOOO o\Nt^toortooo w N PO 10 10 l^ ait ^aa^ puB saqouj '^i{3iajj 7 11 1 11 11 ^aa^ puB saupuj 't[^piAY \o *o 10 o ^t* o N T ? ? ? ? r r r ^aa^ puB saqouj 'i^3uaq POOOO o Tj-TfrM to ii 0*9 saqouj '^snBqxg H W "rTN^ro saqoui 'a^oa^s w saipuj 'aap -UT|XQ jo aa^auiBiQ He, He, M 1 3 1 O 55 U Q M pq 03 GO * spuno^ 'a^d -0103 apig H 3 IH puB jossajduioQ oiooootooto IOO>00 t^t^rfN t^ M M PO O l> O\ spuno00 10 ' ' \r> O O t* O O t?- fO PO N 1-1 M M . . . So rt o o' O H :* O 00 - to O l> O 10 10 PI "t < Q n f*5 M O 1O IO M t- O m 77^ "? . X" ... * !,!. : a * inlll"^ tlllllhtfii bflbOCCW4>4)4)^3^3 CCaJrt.ti.tl^r^aJrt WWHHPH^OO^J Total Labor cost per to O O O O O >OtO 100 O O t-t- M M to G ca PI IOTfPIPIPIPIIHI-1 M O M g I c o M O O O O O 00 0000 *fr rt PI N M PI 1 1 1 1 1 1 o r- \r> M o d motor-d c : : s 1 Q (- r???TT : : iO 2 ? o o o *n (*) r<5 M w M 1 1 1 1 1 M O ^aj 3 -1J FRIGERATION IO ro O O O >0 O OO t- <^ ei ei M ' ' '. '. M M M M ^ tfi \n N Ul (N l^ PO a T3 ^ ^ ^ 1 M C "s ^ M l/> N t! O v o> en ca'O c fe aJ .S.SSSvTJoo MbflO) 0) wwSSSSjj Total Labor cost per ton. . NOTE. In th omit oilers and firem 374 ELEMENTS OF REFRIGERATION COST OF FUEL AND SUPPLIES PER DAY TONS OF ICE PER 24 HOURS S 10 IS 20 25 35 So 75 IOO 200 Fuel cost at $3 per ton. 3.25 3.20 8.80 So 6.50 4.20 16.80 75 9-50 4.80 19. 20 1 .00 12.00 4-40 17.00 I . IO 13.00 5-00 20.00 I. IS 16.00 24.00 7.00 10.00 28.00 40.00 i-4S! i.QO 34-00 14.00 56.00 2.75 43-00 20.00 80.00 3-75 78.00 40.00 1 60.0 7-25 Oil at 4 cts. per gal Electricity at 2 cts. per K.W. Oil, waste, etc Cooling Water. Starr in Ice and Refrigeration for Sept., 1911, points out that the head pressure increases when the quantity of water is decreased. This increases the cost of compression but decreases the cost of water and the cost of pumping water. There may be some point at which the com- bined cost of compression, water and pumping water is a mini- mum. This point will vary with cost of water, lift of water and cost of compression. This should be investigated for any given problem. Cost of Water. B. C. Sloat in Ice and Refrigeration for Dec., 1910, gives the following costs of pumping water per 1000 gallons: Head lifted, feet 50 100 150 300 Deep-well pump 1.7 cts. 3.4 5.1 10.3 Air-lift pump 1.2 3.6 7.7 Displacement pump o . 85 ct. 2.3 4.2 Cities charge from 5 to 20 cts. per 1000 gallons for water. Cost of Supplies in Ice Plant. Ice Plant of Moderate Size by Charles Dickerman in Transactions A. S. R. E v 1908. Year. Total Tons. Tons per Day. 300 Days. Cost Coal. Wages. Supplies. Repairs. Improve- ments. General Expenses. 1904 1905 1906 1907 Avera 6667 8720 9M4 8866 ge per 23 29 30 30 ton $1321.08 1550. 16 1481. 15 1377-05 $4749.90 4677.70 5398.55 5204.19 $1266.72 936.64 837-25 887.51 1354.40 823.14 1075.36 933.8o $1352.02 756.46 301.15 556.00 $ 679-23 1614.48 604. 26 $0.172 $0.600 $0.118 $o. 125 $0.089 $0.087 Total cost per ton exclusive of overhead charges $1.19 Receipts per ton at plant $i . 50 to $8 COSTS OF INSTALLATION AND OPERATION TESTS 375 Data from plant: Capacity, 30 tons. Compressors, two 13X30 vertical. Condensers, double pipe, 2 and 3-in. six banks, 12 high, 18 ft. tubes. Brine tank, 24 coils 2-in. pipe, 6 high, 44 ft. long, 6336 ft. Ice cans, 483 cans, 300 Ibs. Two bulkheads and two engine-driven agitators in tank. Fore cooler i2-in. diam.Xi6 ft. long. Ice house, 60 tons capacity, cooled by brine. Boiler, 66-in. return tubular, 18 ft. long. Fortyeight 4^-ia. long. Stack, 30-in., 125 ft. high. Bituminous coal, $2.40 to $2.50 per ton. Water, 3 cts. per ton of ice. Ammonia, $150 to $200 per year. Performance, 6| tons of ice per ton coal. Cost of labor, fuel and supplies at a plant in Asbury Park was 85 cts. per ton } 3ne-half of which was labor cost. Load Factors. The load factor sometimes assumed covers one-third year at full capacity, one-third year at half capacity and one-third at quarter capacity. This gives Load factor o . 583 = 58% Nordmeyer suggests that the operation at full capacity for July with no storage capacity represents 15% of year's demand (use of ice in July equals 15% of total yearly amount) i Load factor = - =0.56 = 56%. 12 With storage space the plant may be run at full capacity for even the whole year. Of course the cost of storage is offset partially or completely by the smaller fixed charges on the smaller equipment. Cost of Storage. W. E. Parsons states that it cost 25 cents per ton to store ice, hold it from spring until midsummer and remove it to delivery platform in a 75-ton plant. J. N. Briggs increases this to 45 cents per ton to cover the charge for the storehouse. 376 ELEMENTS OF REFRIGERATION 1 O Tf to to to O to N M 6 d | o o o to s H 0) OO CO N M M o 0) S b% M * a rt o o o to S 00 V a Tf t^ M CS o ' CO *^ w *^ | o o o to 10 N N 10 o to O 00 N N M to 1 3 | 1 10 10 ON 10 Ov O ^ 1 ^ a M O j o o to w ^J rt o IO ON t^. 00 i 0) CO OO co o M o o ^ 5 S o ^ 2 >; te 1 00 00 4 o' ^ S O t* ** *^ I fc " d N y Q g. 00 NO o gl 2 H 1 s M t> M v> o g j | a g o to o M) CO -> CJ 2 cS o t- |^ o\ U M O (^ 3 u I CO 5 CO 4 M OO ll d CO R S 10 I- N M o to ^ w ^ 5 g M 1 o to o o to IO OO I- 10 g M Tf O Hi w *% w <** g i o o to 10 l^ 10 HH ^_> to N CO sd M CO * "c g : E " : : 1 - :|^f :* : '3 o* 2 : N^ :^ : c 0) ^ -J V-( *^ o a J3 a> a ! 2 t IH jchanic ij2 o o"-2 ,0 o o O t-0 O NO l- te% W> CO a 1 go C OO + o ; o J SS o" 2 S" s M N W 00 N Cs CO < IO w S ^ w W U a 1 o o to 10 ON 5 s rt 0) IO IO M rf & 2 ** N CO M w W O COO to o to 5 ^ O w w w H 1 00 to q W co 10 o" 1-- N M J, M N ^ S w W a OS o o 8 o O O O to o to S ac " t-1 t-- M ^ CO CO W A t* W W I : c :| : O . 11 .2* "o rt cr o> rt a3 cs -g o ; '7> ' M ' Q ^ a "* ; j3 ' vo| .. ' C X ' : 3 L *o 13. 3 >ld 13 d gh .s ul^ B^ 8|3 ^3 1* bSJ ft 3 si t aflS "ft 2 D a a? w O* *> 2* ** >-> 0.0 *> rt*!u ^ & pffi ft 1 ?H M N C 1 > uijPL, Q. a 1 "" 3 i H ffi M 9 w W H w CO 5 GO H t P i' r f" P * 5' r/r 5" v' v" m / 25 15-6 -59.8 591. i 531-3 542.1 49.0 o. 129 1.360 1.231 0.024 16.95 0.059 -25 2O 17-9 -54-6 587.4 532.8 538.0 49-4 0.117 .336 i. 219 0.024 14.89 0.067 20 IS 20.5 -49-4 583.6 534-3 533.9 49-7 o. 105 .317 1.207 0.024 13-15 0.076 -is 10 - 5 2:1 -44.2 -38.9 579-9 S76.I 535-7 537-1 529.8 525.6 50. i 50.5 0.094 0.082 .290 .267 1 . 196 1.185 0.024 0.024 11.63 10.32 0.086 0.097 10 -5 o 29.9 -33.7 572.2 538.5 521.4 5O.8 0.071 .245 .174 0.024 9.19 o. 109 o 5 33.8 -28.4 568.3 539-9 517.1 SI. 2 0.059 .223 .164 0.024 8.20 0.122 5 10 38.0 -23.2 564.4 541-2 512.9 51.5 0.048 .202 .153 0.025 7-34 0.136 10 IS 42.7 -17-9 56o_. 4 542.5 508.6 51.8 0.037 .181 .143 0.025 6.58 0.152 15 20 47-7 -12.6 5S6.3 543-7 504.2 52.1 0.026 .160 134 0.025 5-92 o. 169 20 25 53-3 - 7-3 552.2 545-0 499.8 52.4 0.015 . 140 .124 0.025 5-34 0.187 25 30 59-4 - L9 548.1 546.2 495.4 52.7 0.004 .119 .115 0.025 4.82 0.208 30 35 65.9 3-5 543 - 9 547-4 491.0 52.9 0.006 . IOO .106 0.025 4-36 0.229 35 40 73-0 8.9 539-7 548.5 486.5 53-2 0.017 .080 .097 0.025 3.96 0.253 40 45 80.8 14-3 535-3 549-7 481.9 53-4 0.028 .061 .089 0.026 3.6o O.278 45 50 89.1 19.8 531-0 550.8 477.3 53-7 0.039 .042 .081 0.026 3.28 0.305 SO 55 98.0 25-3 526.5 551.0 472.7 53-8 0.049 .023 .072 0.026 2.99 0.334 55 60 107.7 30.9 522.0 552.9 468.0 54-0 0.060 .005 .065 0.026 2.73 0.366 60 65 118.1 36.5 517.5 554-0 463.3 54-2 0.071 0.986 .057 0.026 2.50 0.400 65 70 129.2 42.1 512. 8 555-0 458.5 54-3 0.081 0.968 .050 0.026 2.30 0.435 70 75 141.1 47-8 508. 1 556.0 453.7 54-4 0.092 0.950 .042 0.027 . II 0.474 75 80 153.9 53.6 503.4 557-0 448.8 54-6 O. IO2 0.933 .035 0.027 94 0.516 80 85 167.4 59-4 498.5 557-9 443.9 54-6 o. 113 0.915 .028 0.027 -79 0.559 85 90 181.8 65.3 493.5 558.9 438.9 54-6 o. 124 0.898 .022 0.027 65 0.606 90 95 197.3 71.3 488.5 559-8 433.9 54-6 0.134 .881 .015 0.027 52 0.656 95 IOO 213.8 77.3 483.4 560.7 428. 7 54-7 o. 145 0.864 1.009 0.028 41 0.710 IOO 105 231.2 83.4 478.2 561.6 423.5 54-7 0.156 0.847 1.003 0.028 30 0.766 105 no 249.6 89.6 472.9 562.5 418.3 54-6 0.166 0.830 0.997 0.028 .21 0.826 no US 269.2 95-9 467.4 563.3 412.9 54-5 0.177 0.814 0.991 0.028 . 12 0.891 115 120 289.9 IO2.2 461 .9 564-2 407.5 54-4 0.188 0.797 0.985 0.028 .04 0.960 120 125 311.6 108.7 456.3 565.0 402.0 54-3 0.199 0.781 0.979 0.029 0.97 i .031 125 386 ELEMENTS OF EEFRIGERATION II 00 PO I^OOOOOOO lONiOf-OO Tt rtoO O t- 00 'o l> -* NO OOwt^PO O lO w t^ Tt NOt^iOPO i-i O 00 r- oypVdg ooV t^oo o 10 10 4 4co n n ro N N N N N ' M N OvO O O OO 1OO O\CS^t PO'-'^'POOs 1OO O to IO t^t^Ot^OO OOONt^O N-^twiOOi If) l-l O & ' r- PO C\ if) IH OO ro OO PO M O\O ^ N O O* t^O OOiOiOiO 't'tPOPOPO PONNNN NWMM 4 <> 4 a PO M ao N oo 4 w oo 4 N o' o PO : ~ ; t^oo PO ^fr-ooo o o OMOO o\ o 10 M o If) If) If) VOI/31OIOIO 1OIOOOO . . . N PO ^" IOO OO O* M N rO ^*O t^ O\ 00 lOOt^POM ^t^WPO'-i Tt lOO O t^>OO OO O\ O\ O M IO IOIOIO1OIO If) If) lOO O PO ^to i^oo o b N Tt 100 oo o\ <-> OO O O i-t 1000 N O O O 10 HI rtPOOO w o PO O O PO O t- 1OO t- t-- 00 00 Ov O OOONN Tt^-0 POO NOOW MMMMM MMNN ^t ONOO O N Nt^MPOO it ^t w Tt 10 PO POO POO O>-iiOTtO\ t^O\t^M (MMMMM r^NOiOO TtOO N O O "* w t- POOO POOO rj- O if) N 00 rC O III I I III >-i>-ii-iNNPOPO T fr*3-'OiOOO t^OO 00 O> Oi O M ui 'bg 10 t- OM-" PO OMMN ganiBjgdtugj, P) | _|_ M M PO Tf in t-OO OMM ^toO OO MoOMOOOOOO<>lt^ . -PON MOO\0000 t- t-OO lOlO^'t'^POPOPOPONN NNNM lug^uoQ . . . ^T . . t M .. M . N .^ t . . . *7 "? T "? . "? .. *? t N . . . . .ioiOU1iO>Oii/5U}U}i/5iou} iflO OO OOOOO OOOO ^Baaduzaj, : : : : : :">% S% ^vo^oo'o, o P?5*o a'S^^o SSo OO M ''TJp^dg ..... :-:'22?5?j?224li25S?iw2f5S 1U91UOQ M OO O\ 1OO ^fOO NC^OOOO ^'MO X . IM OOt^PO Tf Tf in uio O t-00 OOOvOOM MNPOrJ-ioOOt-OO \n in m m m m in if> 1/510000 ooooo oooo gan^gduzgx MMMMMMS(NNNN(NP) J -39Q '9JU1B 't O\OO O N C^lMPOO ^"^M^iO PO POO POO OMIOT}-O* t^OitM N > a 3 3 jj hn to fj >J ^W d +J l w 3a3 P* Q, "8 . "o . *O ^^ ^^ >*~* 5 6 ressure, Sq.in. lit *o - -> O.Q ill lit Is |f ntropy ization O gaS i-T-O fii 1 1 H ew 8 W tu HI w M H W CO CO CO H t P' i' r i" P * s' r/T 5 " v" *' m t -25 202 22.2 124.7 102.5 108. i 16.6 0.050(0.287 0.237 0.015 0-459 2.17 25 20 2lS -20.5 123.2 102.7 107. i 16.1 o. 04610. 280 0.234 0.016 0.416 2.42 20 -is 238 -18.8 121. 6 102.8 105.5 16.1 0.042 0.274 0.232 0.016 0.381 2.62 15 10 -5 260 283 I7.I 120.0 102.9 IS- 3'n8. 31103.0 1 104.0 IO2.4 16.0 15.9 -0.039 0.034 o. 267 0.260 0.228 0.226 0.016 0.016 0.348 0.320 2.87 3-12 10 -5 o 308 -13-5 116.5 103.0 IOO.7 15.8 0.030 0.254 o. 224 0.016 0.293 3.41 o 5 334 it. 4 JI4-7 103.1 99-1 15.6 0.027 0.248 0.221 0.016 0.268 3.73 5 10 362 9.7 112. 7 103.0 97-4 15-3 O.O22 0.240 0. 2l8 0.017 0.245 4.08 10 IS 391 -7.7 no. 6 102.9 95.6 15.0 O.OI7 0.232 0.215 0.017 o. 224 4.46 IS 20 422 -5-6 108.3 IO2.7 93-6 14.7 0.013 0.225 O.2I2 0.017 0.205 4.88 20 25 454 -3-5 105.8 102.3 91-4 14.4 0.008 0.217 o. 209 0.017 0.188 5.32 25 30 489 i.i 102.9 101.8 88.9 14.0 O.003 0.209 0.206 0.017 o. 172 5.8i 30 35 526 . 1.5 99.7 IOI . 2 86.1 13.6 +0.002 O. 2OO O.2O2 0.018 0.157 6.37 35 40 565 4.3 96. i 100.4 82.9 13-2 O.OO7 O.I9I 0.198 o.oi 0.144 6.94 40 45 606 7-4 92.0 99-4 79-2 12.8 0.012 O.!8l 0.193 0.018 0.132 7-58 45 50 650 10.8 87-4 98.2 75.2 12.2 0.017 0.172 0.189 0.019 O. 120 8.33 50 55 696 14-3 82.6 96.9 71.0 II. 6 O.O23 0.161 0.184 0.019 0.109 9-17 55 60 744 17-9 77-4 95-3 66.5 10.9 0.030 0.149 0. 179 0.020 0.099 10. 10 60 65 795 21.9 71-4 93-3 61.3 IO. I 0.037 0.137 0.174 O.O2O 0.089 11.24 65 70 848 26.4 64-7 91. i 55-4 9.3 0.045 o. 123 0.168 0.021 0.080 12.50 70 75 904 31-5 56.8 88.3 48.6 8.2 0.055 0.106 o. 161 O.O22 0.071 14.08 75 80 962 37-2 47-5 84.7 40.7 6.8 0.065 0.089 0.154 0.024 0.062 16.13 80 85 1022 45-4 33.8 79-2 28.5 5-3 0.080 0.061 o. 141 O.O2( 0.054 18.52 85 87 1048 52.0 22.8 74-8 19.7 3-1 0.091 0.040 0.131 0.028 0.044 22.73 87 88.4 1070 63.0 O.O 63.0 O.O O.O 0. 112 0.000 O. 112 0.035 0.035 28.57 88.4 COSTS OF INSTALLATION AND OPERATION TESTS 389 S 1 g w S 1 1 II cfl o 3 en O I! BoS er * tn S * l! OO*O N PO to M o* M O O O O ON ^toO t^t/SPO N O O*OOO OOTJ-PON NM OO\ OOO OOOOO OOOOO OO OO lO^ff) O O O N f OO\NTfM MPO V)*t- ff) if\r> Ot^O\MN rtirt t^OO O M PO UJ r~ OOO OOOMM |_|MMMP< CSM NN OON rj-OoO'4-O 00 OOO 00 OOO "too 00 ^J-M 00 ^ O POO O t~O N N M OO NO M N N 'tO r~00 O\ O M (N PO Tf 10 t>-OO Oi f*5O fO ro ir> M OO r-O >O TfPONNM MO O\O\ O d o d d d odd do o d 00 ^tOO PO t-~ POO O> HI NO N 00 N^tior^ OOOMOI^" tor-- O\O 0000 OMMMM MM MN O HI irjoo O HI o O\OO t^ O " OO O\ O M N fO *s> t^OO ... O>OvOOO 00 00 . . . 1/5O t^OO Oi O M N Tf O N O\ MO 'tO '.*.'. '. '. M 00 O S" OO ; ; ; d o d d d d d too ^ 00 O\ M N o\ o\ c\ c\ o\ o o OOO O ** ON N M o o\ o o' d> O t-oo 00 O M N NNOOfO O'tMOOrJ- I I MM MNPOfO^ OOOOO o -oO ON O M 'tO O* M 00 IOIOOO 0* t*- Ov HH O U dfo NMOO 1 * 't't'tmoo NOOON OOOO Tft N N II t-~ PO PO >OO ifl Tj- PO 1-1 t^ ro TtO >OOO _)_ I-H N PO 't "W5O t^OO 00 O\ O M N PO ONOO O w O Tj-lO t-00 Ov M ON O M PO c ' u O o || OOOOO OOOOO OOOOO o o o' o o )-l M MM 00 O ROPY. Tt o "rt OPOO OOOOON 't >-i O 00 t^O 10 't N M OOO PO O N O O fOO PO N MO -oo ooooo ooooo ooooo o o' o' o'
  • PC U . . . O M o ONOO >o O IOOO t^ 00 oo ' Pressure, T,hs. npr Sn.in. 1 0000 ooooo ooooo O O IO O - "0 IOO 10 O t~ t^OO 00 ooooo O O t^ O O O.O Q M .s p II M> 11 83s lit < o ft * empera Degrees H 04 w 1 w W H w C/3 tt> C/3 H / P i' r i" p * s' r/t s" < v" m t -25 S.i 17-4 165.5 148.1 135.0 13.1 0.038 0.380 0.342 O.OI 13.89 0.072 25 20 5-9 -15-9 164.9 149.0 135.9 13. i -0.035 0-375 0.340 O.OI 12 .02 0.083 20 is 6.8 14.4 164.2 149.8 136.6 13.2 0.031 0.369 0.338 O.OI 10.42 0.096 15 10 7-9 -12.9 163.6 150.7 137.4 13-3 0.028 0.364 0.336 O.OI 9. 12 O.IIO IO - 5 9-1 -ii. 4 162.8 151.4 138. i 13-3 0.025 0.358 0.333 O.OI 8.05 0.124 -5 o 10.4 9.9 162.0 152. i 138.7 13-4 O.O2I 0.352 0.331 O.OI 7.12 0.140 5 11. 8 -8.3 161.3 153.0 139.5 13-5 O.OI8 0.347 0.329 O.OI 6.27 0.159 5 10 13-3 -6.8 160. 5 153.7 140.1 13.6 O.OI5 0.342 0.327 O.OI 5.56 .180 10 15 15-0 -5-3 159-7 154-4 140.7 13-7 O.OII 0.336 0.325 O.OI 4-95 .202 IS 20 17.0 -3-8 I59.I 155.3 141-5 13.8 0.008 0.332 0.324 O.OI 4.42 .225 20 25 19.2 2.2 158.3 156. i 142.1 14.0 0.005 0.326 0.321 O.OI 3.96 .253 25 30 21.5 -0.6 157.4 156.8 142.5 14. i O.OOI 0.321 0.320 O.OI 3.56 .281 30 35 24.0 1.0 156.3 157.3 143.1 14.2 0.002 0.316 0.318 O.OI 3-20 0.312 35 40 26.7 2.6 155.4 158.0 143.7 14-3 0.005 0.311 0.316 O.OI .88 0.347 40 45 29.8 4.3 154-3 158. 6 144.2 14.4 0.008 0.306 0.314 O.OI .61 0.383 45 50 33-0 6.0 153.3 159.3 144.8 14-5 O.OI2 0.301 0.313 O.OI .36 0.424 50 55 36.5 7-7 152.1 159-8 145.3 14-5 O.OI5 0.296 0.311 O.OI 15 0.465 55 60 40.4 9-3 151.1 160.4 145-8 14.6 0.018 0.291 0.309 O.OI .96 0.510 60 65 44-7 II .0 149.9 160.9 146.2 14-7 O.02I 0.286 0.307 O.OI .78 0.562 65 70 49-2 12.7 148.8 161 . 5 146.8 14.7 0.025 0.281 0.306 O.OI .62 0.617 70 75 54-0 14.4 147.6 162.0 147.2 14.8 0.028 0.276 0.304 O.OI .48 0.676 75 80 59-3 16.1 146.4 162.5 147.7 14.8 O.O3I o. 271 0.302 O.OI .37 0.730 80 85 64.9 17.8 I45-I 162.9 148.0 14.9 0.034 0.266 0.300 O.OI .25 0.800 85 90 70.9 19-5 143.9 163.4 148.5 14.9 0.037 o. 262 0.299 O.OI . 15 0.870 90 95 77-5 21.3 142.5 163.8 148.8 15.0 0.041 0.257 0.298 O.OI .05 0.952 95 IOO 84.4 23. 1 140.9 164.0 149.0 15.0 0.044 0.252 0.296 O.OI 0.96 1.042 IOO 105 91.8 24-8 139-4 164.2 149.3 14-9 0.047 0.247 0.294 O.OI 0.88 1.136 105 no 99-4 26.6 137-7 164.4 149-5 14.9 0.050 o. 242 o. 292 O.OI 0.82 I . 22O no us 107.2 28.4 136.3 164.7 149.8 14-9 0.053 0.237 0.290 O.OI 0.77 1.299 us 392 ELEMENTS OF REFRIGERATION i< O -O O v O S A yP 9( Jg O^(>OPHi OOvOOt-ui TtrONwHi O N M W M ^U9^UO^) H/BgjJ ^(NrONHi OO\O\ Ov , Jn , 8Jad ^ rfoo M t^O 0^0 ^ ^troOO o O O suinjoy^ oijpadg '^U9^UOQ T 69 !! fO^J"oOO OOOOOMM "^fOt^ooO MC^ro^}" -M^X OOO\OOO OHiMMro fO^J*>OOO t^oOOOC\ O auinjoA 3 yi3 9 dg 3ss2 ^^:-o^ ^-^s^?. sss^ eo oo a oo u, "?"~~o_ oor ? ? o -7^00^ M M M M HH MMMHTtT M M "2 "2 "2 ^"2^2 ajn^Bjaduiaj^ l-t-000000 OvaOOHi MNPOrt^t i^OOJ- o '9Uin|Oj\ OtJIDadg ^fONOO O\oOt-OO fONWHiO OOvOOO "?"?"? N . M . ^ . "? T . ^ . M . t ? ^ "? ? ? 00000 OOOOt- t-t^t-t-t- ^.S<00 J^vSovo^ So; ^^g^?? ^5^S o O -npAo^ds -O\ oOoOt-O'l- rONMHO OOOvoO : : : : g^^J &^II^ ci^4^t ^.nvvejadtuax : : : :5 32E2 ZZ^ZZ a^S^ o aiunp^Y oijpadg in 00 CS t- M t^ Tf -MOO O Oi 00 00 HI M HI O -,-,-oa ,H ..... ; ; ; ; ; ; ; ^ o - 'S^'S V S'2'2 V 2 ajn^asduigx ::::: ::::: :: aS; oMS _ W 0,,^ S ^untoioio OOOOl^ oooooOOO\ OOOO UT -bg jad -sqq 'aanssajj 394 ELEMENTS OF REFRIGERATION TABLE or CHLORIDE OF CALCIUM (CaCl 2 ) SOLUTION Specific Gravity at 60 F. Degrees Beaum6 at 60 F. Degrees Salom- eter at 60 F. Lbs. (CaCls) per gal- lon So- lution. Lbs. (CaCU) per Cu. ft. Solu- tion. Percent- age (CaCU) by Weight. Freezing- point F. Specific Heat at 32 F. Weight per Gallon at 60 F. .O2I 3 12 k 3l 3 + 20 0.965 8-54 043 6 27 I 7* 5 + 27 0.920 8.70 .066 9 36 a g* 7 + 25 0-883 8.88 .074 10 40 if i 9 + 2 3 0.868 8.96 .082 ii 44 if 13 10 + 21 0.857 9-05 .099 13 52 2 -15 12 + 18 0.830 9.19 US 15 62 2l 17 14 + 14 0.808 9.29 . 160 20 80 2^ J 9 18 +4 0-753 9-65 .179 22 88 3 I 20 - J -5 0.732 9-83 .198 24 95 3^ 26 22 -8 0.714 IO.OO .219 26 104 4 3 24 -17 0.695 10. 16 239 28 112 4i 34 26 -27 0.678 10.32 .261 30 I 2O 5 37^ 28 -39 0.661 10.50 .283 32 128 5^ 4i| 30 -54 0.643 10.72 If more chloride is used the freezing-point is raised. Use about i ton of CaCl 2 for each ton of ice-making capacity. TABLE OF SODIUM CHLORIDE (SALT) SOLUTION Specific Gravity at 39 F. Degrees Beaume at 60 F. Degrees of Salom- eter at 60 F. Pounds of Salt per Gal- lon of Solution. Pounds of Salt Cu G ft. Percent- age of Salt by Weight. Freezing- point Fahren- heit. Specific Heat. Weight per Gal- lon at 39 F. 1 .007 I 4 0.084 .628 I 31-8 0.992 8.40 1.015 2 8 o. 169 1 . 264 2 29-3 0.984 8.46 1.023 3 12 0.256 1.914 3 27.8 0.976 8-53 1.030 4 16 0-344 2-573 4 26.6 0.968 8-59 1.037 5 20 0-433 3-238 5 25-2 0.960 8.65 1-045 6 24 0-523 3.912 6 23-9 0.946 8.72 1.053 7 28 0.617 4.6l5 7 22.5 0.932 8.78 I .061 8 32 0.708 5-295 8 21.2 0.919 8.85 1.068 9 36 p. 802 5-998 9 19.9 0.905 8.91 1 .076 10 40 0.897 6.709 10 I8. 7 0.892 8-97 1 .091 12 4 8 i .092 8.168 12 16.0 0.874 9.10 I.H5 15 60 1.389 10.389 15 12. 2 0-855 9. 26 I-I55 20 80 1.928 14.421 20 6.1 0.829 9.64 if; i.F 9 6 24 25 9 6 100 2.376 2.488 17.772 18.610 24 25 1.2 o-5 0-795 0.783 9.90 9-97 1.204 26 104 2.610 19.522 26 i .1 0.771 10.04 COSTS OF INSTALLATION AND OPERATION TESTS 395 Correction for temperature of aqua ammonia to reduce Beaume readings to 60 readings subtract J Beaume for the following number of degrees F: From 18 to 20 B. for each 8 F. above 60 F. From 20 to 22 B. for each 7 F. above 60 F. From 22 to 23^ B. for each 6 F. above 60 F. From 23^ to 25^ B. for each 5 F. above 6o d F. Above this for each 4 F. above 60 F. COMPARISON OF THERMOMETERS Cent. Fahr. Cent. Fahr. Cent. Fahr. -40 40.0 8 46.4 56 132.8 -38 -36.4 IO 50.0 58 136.4 -36 -32.8 12 53-6 60 140.0 -34 -29.2 14 57-2 62 143-6 -32 -25-6 16 60.8 64 147.2 -3 22 .O 18 64.4 66 150.8 -28 18.4 20 68.0 68 154-4 -26 -14-8 22 71.6 70 158.0 -24 II .2 24 75-2 72 i6!.6 22 -7.6 26 78.8 74 165.2 2O -4.0 28 82.4 76 168.8 -18 -0.4 3 86.0 78 172.4 -16 +3-2 32 89.6 80 176.0 -14 6.8 34' 93-2 82 179.6 12 10.4 36 96.8 84 183.2 10 14.0 38 100.4 86 186.8 -8 17.6 40 104.0 88 190.4 -6 21 . 2 42 107.6 90 194.0 -4 2 4 .8 44 III . 2 92 197.6 2 28.4 46 II4.8 94 2OI .2 32.0 48 Il8.4 96 204.8 2 35-6 5 122.0 98 208.4 4 39-2 52 125.6 100 212.0 6 42.8 54 129. 2 TESTING REFRIGERATING APPARATUS Tests of refrigerating apparatus are difficult to perform because the changes of temperature in various parts of the appa- ratus are very slight, because the weight and quality of the refrigerating medium is difficult to determine and because the 396 ELEMENTS OF REFRIGERATION errors at start and finish of the test make it necessary to carry the test over a considerable time. Tests are necessary to determine the effects or values of new devices and alterations and particularly to determine whether or not the guaranteed amount of refrigeration or the guaran- teed refrigerating effect has been obtained. To find the yield of the apparatus, the refrigerating effect may be measured from the ammonia or from the brine or in an ice plant the amount of ice produced may be found. If the guarantee is the production of a certain amount of ice or the cooling of certain rooms to a definite temperature with a given amount of power and cooling water this test is simple except for the length of test, which should never be less than twenty-four hours and would be much better if continued for one or two weeks. When, however, the refrigerating effect is to be found the test is difficult because of the quantities to be measured. The refrigeration produced from the ammonia is given by Q r =M(ii-h)\ M = weight of ammonia in given time; 2*1= heat content in suction main leaving expansion coil; 4= heat content at entrance to expansion valve. To determine this, the various factors on the right-hand side of the equation must be found. The weight of ammonia, M , may be found by collecting the ammonia in a receiver resting on a platform scale. This is connected to the piping sys- tem by a long piece of pipe so that there will be only a slight effect from the rigidity of the pipes. If the pipes are 10 ft. long the weight necessary to deflect the pipe an amount equal to the movement of the scale platform will be so small that little error results. By using two receivers, one may be filling while the other is being emptied. The ammonia may be col- lected in two tanks and the volumes measured, this being changed to weight by calibration. Care must be taken to have no pockets in the piping in which the ammonia may collect. In fact the uncertainty of the amount of ammonia which may lodge in pockets makes this method a difficult one and for that COSTS OF INSTALLATION AND OPERATION TESTS 397 reason in some tests, such as those at the Eastman Kodak Co., the refrigeration is measured from the brine side. The quantities i\ and is are difficult to determine if by chance there are liquid and vapor present together. To prevent this, the liquid going to the expansion valve is after-cooled so that it is below the temperature of vaporization corresponding to the pressure and must be all liquid (hence iz=qz) and the vapor entering the suction valve is slightly superheated so that the quality may be determined by a thermometer In this way it is possible to find the value of i\ and i%. The compression is dry compression. If it is desired to have wet compression it would be possible to have slightly superheated ammonia in the suction pipe and add an amount of liquid ammonia from a calibrated tank. The thermometers placed in the thermometer wells are subject to errors, due to the warming of the stem if any mercury projects above the well, and if none projects above there is difficulty in reading the thermometer, as the stem often freezes fast to the well on the suction side. To correct for stem error it is well to determine the temperature of the stem t s by a small thermometer tied to the stem and if t t is the reading of the thermometer, and / is the reading of the point of the ther- mometer opposite the edge of the well so that the number of degrees exposed, above the well is t t t w , the correction to be added to the reading is At = 0.000088 (t t - t,) (t t - O . This assumes that the length (t t t w ) is heated (t t t s ) degrees above the temperature it should have been, and 0.000088 is the difference between the coefficient of expansion of glass and mercury. Constant immersion thermometers which have been calibrated to read correctly in rooms *of a certain tem- perature when immersed to a mark on the stem may be used with no correction. 398 ELEMENTS OF REFRIGERATION To save corrections and troubles in observation, thermo couples or resistance thermometers may be used. Calibrated gauge readings as well as temperatures are neces- sary on suction and discharge to determine the quantities i\ and 2*3. The suction pressure is often measured by using a mercury U-tube so that small pressure differences may be read. On account of the errors in the method above, the refrigera- tion is sometimes determined from the brine, which is cooled by the ammonia. Mi) = weight of brine; c specific heat of brine; to = temperature of brine at outlet from cooler; /, = temperature of brine at inlet to cooler. In this case the weight of brine -M b is measured by weighing in large tanks; by the use of a meter which is calibrated at intervals during test; by the use of a Venturi meter or weir. The calibrations of these pieces of apparatus are absolutely necessary. The specific heat c must be determined by a formula from the specific gravity of the brine and the temperature or by tables given earlier or, what is better, by an experimental determination made in a Dewar flask by finding the watt hours used in a coil and required to warm a certain amount of brine between the temperatures used during the test. Corrections can be made for radiation by cooling curves and the water equivalent may be found by method of mixtures or by heating distilled water. In finding c by the formula or table the mean temperature is used and the specific gravity is determined by a hydrometer of some form. The temperatures to and t t are subject to the same corrections mentioned before and because the difference between them is so small the thermometer should be graduated to tenths of a degree, or smaller, divisions. The use of Beckman thermometers would prove of value here. COSTS OF INSTALLATION AND OPERATION TESTS 399 The power of the engine required to drive the compressor and the power of the compressor are determined by indicator diagrams. The small clearance on the compressor makes it necessary to use close and small connections for the indica- tors as the increase of clearance when the indicator is opened will change the form of card. It would be well to have a com- pensating volume to cut out when the indicator is connected or the indicator might be placed so that the piston would move vertically downward and the passage from the cylinder could be filled with oil so that this volume is not filled with ammonia. The usual formula for horse-power is used. It is necessary to test the springs and have the reducing motion correct. The amount of cooling water is weighed, metered, passed through an orifice or over a weir and its temperature is deter- mined by thermometers. The heat is given by In all cases the machines should be brought to an operating condition before starting the test and a running start should be made. With brine to determine refrigeration ten hours after steady conditions are obtained may be sufficient, although with ammonia a longer test must be used. In testing absorp- tion machines calibrated meters are used to determine the flow of liquor and the strength of the liquor is determined by drawing off samples and using a hydrometer to give the speci- fic gravity. Thermometers and gauges give the conditions at the various points. Meters are used to measure the cooling water and thermometers give the temperatures from which the heat may be determined. The drip from the separator may be determined by passing it into one of two cylinders and measuring its volume on the way to the analyzer. The test of ice plants should extend over a number of days five or seven, and in this test the ice is pulled at regular inter- vals during the twenty-four hours. The test is started after the plant has been run at least seventy-two hours to get steady conditions. 400 ELEMENTS OF REFRIGERATION General observations should be made at fifteen-minute intervals. These include the following: Temperatures: out- side atmosphere, engine room, refrigerated rooms, condensing water at inlet and outlet, brine at inlet to cooler and at outlet, ammonia at entrance to expansion valve and at entrance to suction main, at suction valve and at discharge main on com- pressor, at inlet and outlet to jacket; pressures on suction and discharge main, and in expansion coil, barometer; volume shown by meter on brine line, condensing water line and jacket water line, indicator cards, revolutions of compressor, weight of water going to ice tanks with temperature, weight of water left unfrozen, weight of coal, weight of boiler feed, feed tem- perature, calorimeter readings, flue gas temperature. The computation for such a test will be given in the next chapter. For absorption machines the readings are somewhat similar and are used in the same manner. A form of test has been discussed by the A. S. R. E. in its proceedings. The following data are obtained from a series of tests: RESULTS or TEST ON DOUBLE-ACTING COMPRESSOR, MADE BY THE DE LA VERGNE Co. AT THE EASTMAN KODAK Co., DATE FEB. 5, 1908 Temperature: Discharge ammonia R.H 149.44 F. L.H 143. 36 F. Suction at compressor, before liquid injection 17 . 80 F. At brine cooler 19.40 F. Before expansion valve 58.91 F. Brine at inlet to cooler 25 . 11 F. Brine at outlet from cooler 14.81 F. Engine room 65 . 85 F. Ammonia receiver room 55 . 58 F. Outside atmosphere 14.93 F, Revolutions in i5-minute compressor 512.1 Revolutions in i5-minute brine pump 419 COSTS OF INSTALLATION AND OPERATION TESTS 401 Specific heat of brine o. 678 Weight of brine per revolution 41-15 Ibs. Specific heat of liquid ammonia. . . . ' i . i Pounds of liquid ammonia in 15 min 236.6 Pressures: Suction at cooler 20.45 at compressor 20 . 03 at condenser 185 .06 Steam at engine 84 . 1 1 Barometer 15.01 M.E.P. Head end 38 . 95 Crank end 39-67 I.H.P .. 55.83 Tons of refrigeration by brine 36 . 91 Equivalent tons with 20 Ib. suction 36.88 I.H.P. per ton i . 514 Size of compressor. .. njx 22 (2^ piston rod) double acting Size of engine 22X22 (3! piston rod) RESULTS OF TEST ON SINGLE-ACTING COMPRESSOR MADE BY THE YORK MFG. Co. AT THE EASTMAN KODAK Co., DATE MAR. 9, 1908. Temperatures: Discharge ammonia R.H 248.3 F. L.H 243. 3 F. Suction at compressor R.H 14 . 34 F. L.H i 5 .2oF. At cooler 9 . 29 F. Before expansion valve 77 . 91 F. Brine at inlet to cooler 22 . 73 F. Brine at outlet from cooler 13 .02 F. Engine room 64 . 80 F. Ammonia receiver room 73 .46 F. Outside atmosphere 24. 79 F. R.H. water jacket 180.7 F - L.H. water jacket 168.45 F . Revolutions in i5-minute compressor 514. 7 Brine pump 426 . 85 402 ELEMENTS OF REFRIGERATION Specific heat of brine o. 678 Weight of brine per revolution 41-15 lb. Pounds of liquid ammonia in 15 minutes 2 33-9 Pressures : Suction at cooler 20.46 at compressor 20.04 at condenser 187 . 27 Steam at engine 81 . 96 Barometer 14 . 95 M.E.P.: Headend 36.56 Crank end 37 . 09 I-H.P 5^57 Tons of refrigeration by brine 37 . 01 Equivalent tons with 2o-lb. suction 36.97 I.H.P. per ton i . 42 Size of compressor 15X22 (single acting) Size of engine 22 X22 (3! piston rod) TEST or Two DE LA VERGNE STANDARD HORIZONTAL RE- FRIGERATING MACHINES, DATE OCT. 27, 1910 Temperatures: Ammonia discharge 245 .80 F. Ammonia suction at brine coolers . . 5 . o F. Ammonia before expansion valves. 8. 14 F. Brine at inlet 6 . 20 F. Brine at outlet 17.6 F. Revolutions of compressors 43-5 Pressures: Suction 16 . 23 At condensers < . . 165 . 50 Total horse-power 517 . 88 Tons of refrigeration 373 . 23 I.H.P. per ton 1.398 Size of compressors double acting. . i8j // X33 // Size of engine 22 & 44 X33 Volumetric eff. : Apparent 95 . 38 True 82.15 Rated capacity, two, 275 tons, 550 tons COSTS OF INSTALLATION AND OPERATION TESTS 403 TEST OF KROESCHELL BROS. ICE MACHINE Co.'s CO2 COM- PRESSOR, DATE AUGUST 9, 1907 Compressor, double acting, horizontal. Bore 138 M/M = s&" Stroke 508 Piston rod 58 Speed 65 R.P.M. Compressor gas displacement 54,914.6 cu.in. per min. Condenser pressure 65 atm. Evaporating pressure 23 atm. Evaporating temperature ; 5F. Water temperature condenser inlet 53 F. Water temperature condenser outlet ... 81 F. Temperature of brine cooler inlet 25 . 9 F. Temperature of brine cooler outlet 17 F. Quantity of brine pumped per hour .... 1000 cu.ft. Strength of brine . . . 26 Beaume Estimated loss in brine tanks and cooler 10% Amount of refrigeration 50. 76 tons Indicated power at engine . . 67 . 25 H.P. Indicated power at compressor 51 . 3 H. P. Compressor gas displacement per ton per per min 1082 cu.in. Horse-power -v- cooling effect = i .010 H.P. per ton of refrigeration. TEST OF VOGT ABSORPTION PLANT Aqua ammonia pump 5l X 12 Average speed pump 22 R.P.M. Temperature: Brine inlet ,15 F. Brine outlet 13 F. Ammonia at condenser 105 F. Liquid from condenser 78 F. Strong aqua to rectifier 89 F. Strong aqua from rectifier 120 F. Strong aqua from exchanges 189 F. 404 ELEMENTS OF REFRIGERATION Weak aqua from cooler ...................... 89 F. Cooling water .............................. 65 F. Cooling water from condenser ................ 72 F. Cooling water from absorber ................. 88 F. Cooling water from weak aqua cooler ......... 117 Strong aqua at 60 F ........................ 26^ Beaume Weak aqua at 60 F ........................ 23! Beaume Total cooling water per min .................. 252 gals. Ice per ton of coal ........ -. ................. 10.3 tons TEST OF WESTINGHOUSE-LEBLANC REFRIGERATING MACHINES, DATE AUG. 4TH AND 5TH, 1916 Barometer .............................. 29. 17" Temperature atmosphere ................. 86 F. Live steam pressure ...................... 200 Ibs. per sq.in. Vacuum: ist ejector ..................... 29 2d ejector ..................... 28 . 95 Condenser ................. .... 27.80 Temperature: Condensing water inlet ...... 82 . 5 F. Condensing water outlet ..... 92 F. Brine inlet ....... : ......... 18 .40 F. Outlet .................... 15.00 F. Weight of brine per hour ................. 19826 Specific heat brine ........................ 833 B.t.u. of refrigeration per hour ............ 56,202 Tons per twenty- four hours .............. : 4 . 60 Loss by radiation ......................... 37 Total loss ............................... 5 .05 Steam and vapor condensed per hour ....... 1125 Vapor per hour .......................... 61 Steam per hour .......................... 1064 Tons of refrigeration per ton of coal at 8 Ibs. of steam per pound of coal: 3 1.596 1064 X? 8X2000 COSTS OF INSTALLATION AND OPERATION TESTS 405 TEST OF WESTINGHOUSE-LEBLANC APPARATUS FOR COOLING WATER. MARCH 24, 1915 Barometer 29 . 18 Vacuum in ist ejector 28.91 Vacuum in condenser 27 . 40 Steam pressure (gauge) 125 ist ejector 112.5 2d ejector 110.5 Quality 98.7% Temperatures : Water to be cooled (brine ordinarily) at inlet 40.5 F. at outlet. 34 . 9 F. Steam, line 357-3 F . Atmosphere 69 . i F. Condenser, top 155 . 5 F. Condensate 89. 7 F. Circulating water inlet 79.9 F. Outlet. 89.7 F. Weights per hour: Water to be cooled . . 101,320 Circulating water 450,000 Condensed steam 2513 Heads pumped against 67 . 2 ft. Power brine pump 8 . 83 H.P. Condenser 35-7 H.P. Refrigeration 567,392 B.t.u. per hr. 406 ELEMENTS OF REFRIGERATION TESTS OF HART COOLING TOWER TEMPERATURE. Water. Air. Gallons Rel. Hu- Above Below Wet Atmos- Enter- Reduc- Dry Wet Bulb. phere. ing. Leaving. tion. Bulb. Bulb. 78 74 4 88 72 2 14 600 41 77 7i 6 88 71 O 17 600 39 81 76 5 88 . 74 2 12 600 46 79 76 3 84 74 2 8 600 57 82 75 7 81 73 2 6 600 64 75 69 6 7i 67 2 2 600 78 108 76 32 87 73 3 II 1800 46 in 73 36 76 66 7 3 1800 55 1 08 76 32 81 72 4 5 1800 60 109 78 3i 79 73 5 i 1800 7i 1 08 74 34 74 69 5 1800 74 83 68 15 77 62 6 9 3000 4i CHAPTER X PROBLEMS THIS chapter is devoted to problems illustrating the appli- cation of the text. They are typical problems, and the student is urged to consider them as illustrating principles so that other problems of similar nature may be solved in the same man- ner. Certain problems are solved for a given set of conditions and if these conditions change the results will, of course, differ from those obtained. The general problems of design are repe- titions of certain fundamental problems and it has been the aim of the author to include these fundamentals in this set. The data to be used in actual problems must be obtained for the particular locality. Problem i. Find the best thickness of cork insulation for an 8-in. wall on a room which is to be held at 20 F. Cork thicknesses possible: 2 in., 3 in., two 2 in., 2 and 3 in., two 3 in., etc. Cost of i sq.ft. of cork installed (page 346) : 2 in 25 cts. 3 jn 3 cts. 4 in 40 cts. 5 in. . : 50 cts. 6 in 60 cts. Value of i cu.ft. of storage space, per mo 5 cts. (p. 215) Cost of i ton of refrigeration 40 cts. (p. 376). Average outside temperature per year 48 F. (Fig. 166). Fixed charges (p. 379). Interest 8% Taxes i% Insurance i% Depreciation 3% Repairs 2% Total 15% 407 408 ELEMENTS OF REFRIGERATION Coefficient for 8-in. walls with plaster ........ ^" = o.37(p2ii) C for cork ............................. 0.022 C for plaster ........................... o . 46 For completed walls the effect of additional layers of materials may be computed in the following way: .. K' =new constant; K = former constant for wall; / = thicknesses of new layers; C = coefficients of new layers. (a) K for 8" brick, 2" cork, i" plaster. K' = - -=0.095. 1 , 2 + T 0.37 12X0.022 12X0.46 (b) K for 8" brick, 3" cork, i" plaster. K' = - =0.070. 0.37 12X0.022 12X0.46 (c) K for 8" brick, 4" cork, i" plaster (2", J", 2", %").} ^ = 0.055- (d) K for 8 X/ brick, 5" cork, i" plaster (2", \" , 3", J"). ^ = 0.046. Heat Loss per Year in Tons of Refrigeration per square foot. (a) (V) 0,81 X = o.6o ton; 0.095 PROBLEMS 409 (c) 0.81X^^=0.47 ton; 0.095 (d) 0.81 X- =0.39 ton. Cost of Refrigeration per Square Foot per Year. (a) 0.81X40 = 10.324; (b) 0.60X40= 0.240; (c) 0.47X40= 0.188; (d) 0.39X40= 0.156. Cost of Space Required per Year. (a) X 1X0.05X12 =0.120; (b) X 1X0.05X12=0.180; 12 (c) X 1X0.05X12 =0.240; () - X i Xo.o5 X 1 2 = 0.300. Yearly Cost of Insulation Investment per Year, (a) 0.25X0.15=10.037; (b) 0.30X0.15= 0.045; (c) 0.40X0.15= 0.060; (d) 0.50X0.15= 0.075. Total Yearly Cost. (a) 0.324+0.120+0.037=10.481; (b) = 0.456; (c) = 0.488; (d) = 0.521. 410 ELEMENTS OF REFRIGERATION From the above it is seen that for the assumed conditions the 3-in. thickness is the best. If conditions (assumed data) be changed, a different result will be obtained. If space is worth 2\ cents per cu.ft. per month, a wall made up of two 2-in. boards would be best. Problem 2 Find the space required to store the following: 180,000 doz. eggs, 25,000 bu. potatoes, 200,000 Ibs. butter, 200,000 Ibs. cheese, 25,000 bu. apples, 400,000 Ibs. beef, 200,000 Ibs. mutton, 200,000 Ibs. pork, 20,000 Ibs. poultry, 500 crates celery, 2000 bbls. vegetables, 2000 boxes oranges and lemons. (a) Size Egg Room. , 180,000 , No. of cases = - = 6000 ; 30 Volume of cases = 6000X2^ = 1 3, 500 cu.ft.; Height of piles = 6 ft.; Net floor area = = 225o sq.ft.; 6 Allow | for aisles. Total floor area = 2 250X1 = 337 5 sq.ft. (b) Size Potato Room. No. of barrels = - = 10,000 bbls. ; 2-5 Space required = 10,000 X 5 = 50,000 cu.ft. ; Height of piles = 8 ft.; Net floor area = = 6250 sq.ft.; o Allow i for aisles. Total floor area = 6250X1 = 7812 sq.ft. (c) Size Butter Room. No. of tubs = = 4000; 50 Space = 4000 X 2 = 8000 ; Height of piles = 6 ft. PROBLEMS 411 Net floor area = = 1 143 = 1 200 sq.ft. ; Total floor area = 1400 sq.ft. (d) Size Cheese Room. Same as (c), 1400 sq. ft. (e) Size Apple Room. Same as (b), 7812 sq.ft. (/) Size of Beef Room. No. of halves of beef = - - - X 2 = 1070. 750 Assume these to be hung at i8-in. intervals and 3 ft. apart. Floor space = 1070 X i^ X 3 = 4800 sq.ft. (g) Size of Mutton Room. Assume carcass weighs 60 Ibs per cu.ft. in piles and that piles are 4 ft. high with aisles occupying one-quarter space. Floor space = ^ - X- = 1 100 sq.ft. 60X4 3 (h) Size of Pork Room. Same as (g), noo sq.ft. (i) Size of Poultry Room. Same as (g), noo sq. ft. (j) Size of Celery Room. Total volume = 500 X 10 = 5000 cu.ft. ; Height of piles = 8 ft.; Net floor area = = 625 sq.ft.; 8 Allow ^ for aisles. Total floor area = 625 X f = 940 sq.ft. 412 ELEMENTS OF REFRIGERATION (k) Size of Vegetable Room. Space = 2000 bbls. X 5 = 10,000 cu.f t. ; Height piles = 8 ft.; 10,000 Net floor area = 8 = 1250 sq.ft.; Allow i for aisles. Total floor area = 1250 Xf = 1600 sq.ft. (/) Size of Orange Room. .- Space = 2000 X4 = 8000 cu.ft. ; Height = 5 ft; Net floor space = 1600 sq.ft.; Allow i for aisles. Total floor area = 2000 sq.ft. The layout shown in Fig. 185 is suggested for this problem. The height of the stories would be 10 ft. in the clear. The 5th Floor 6th Floor FIG. 185. Typical Warehouse. height of the building with a 4-ft. basement and a 5-ft. attic would give a total height of 75 ft. PROBLEMS 413 Problem 3. Find the probable amount of refrigeration for the plant in Problem 2, assuming that all goods are received at 70 F. and that 90 F. is the warmest weather. Insulation: Main walls, 8-in. brick with two 3-in. thicknesses of cork at- tached with plaster and plaster finish. Partitions: 8-in. tile with plaster and 2 ins. of cork on one side, plastered. Floors at second story and ceiling of sixth floor: second figure, Fig. 108; other floors: brick arches with ^ = 0.25. (a) Temperature of Rooms. Eggs, 31 F.; Meat, 30 F.; Cheese, 32 F.; Apples, potatoes, vegetables, 36 F.; Butter, 1 5 F. ; Oranges, lemons, 40 F. ; Poultry, 20 F. ; Celery, 34 F. (6) K's for Walls. K for walls (from p. 211) =0.039; K for partitions. K = I =0.081. 0.21 12 2Xl2 0.022 0.46 0.21 for tile with plaster, p. 211; 0.022 from p. 193 for compressed cork; 0.46 from p. 193 for plaster. K for floors. K = 0.062 p. 2ii (second story); = 0.25 assumed for hollow arch bricks without insulation (3d to 5th) ; = 0.030 (p. 211), ceiling, top floor. (c) Heat Loss through Walls, Floors, Ceilings, Partitions. Heat loss from rooms in B.t.u. per hour. 414 ELEMENTS OF REFRIGERATION FIRST FLOOR Holding room : Wall, 35X10 X (90-30) Xo.039 = 820 Partitions (45 + 154- 10+20+35) XioX (90 30) X 0.08 1 = 67 50 Floor = oo Ceiling, 35X35X(36-3o) Xo.o6 2 1 loX 15 X (40-30) Xo.o62j 8119 Total for first floor 8119 SECOND FLOOR Celery room: Walls (55+35) XioX (90-34) Xo.039 = 1965 Partitions [35 XioX (36 -34) + 20 XioX (90-34) +35 XioX (40-34)1X0.081 = 1134 Floor 35X55 X (90 34) X 0.062 = 6684 Ceiling [35X35X(3i-34)+35X2oX (i5-34)]Xo.25 = -4244 5539 Vegetable room: Walls (55+35) XioX (90-36) Xo.039 = 1895 Partitions [3 5 XioX (34 36) + 20 X 10(90-36) +35X10(40-36)1X0.081 = 931 Floor [35 X35X (30-36) +20X35(90-36)] X 0.062 = 1888 Ceiling (35X55) X(3i-36)Xo.2 5 = -2406 2308 Orange room I: Walls (55+35) XioX (90-40) Xo.039 = 1755 Partitions [3 5 XioX (36 40) + 20X10 X(90-4o)+35Xio(4oX4o)]Xo.o8i = 697 Floor [(35X45X90-40) + 10X15(30-40) + 20 X 10 X (90 -4o)]Xo.o62 = 5410 Ceiling 35 X55X (32 -40) Xo.25 = -3850 4012 PROBLEMS 415 Orange room II . Walls (55+35) XioX (90-40) Xo.039 1755 Partitions [35 XioX (34 40) + 20X10 X (90-40) +35 X 10 X (40-40)10.081 640 Floor 35 X55X (90-40) Xo.o62 5964 Ceiling [35 X3$X (15-40)4-29X3$ X (20-40)1x0.25 =-11,156 -2797 Total for second floor 9062 THIRD FLOOR (In the same manner as before.) Egg room , 6,760 Butter rocm 22,642 Cheese room 5,3*8 Poultry room 7,128 Total for third floor 41,848 B.t.u. FOURTH FLOOR Beef room . 12,433 Mutton room 4466 Pork room 742 Total for fourth floor J 6,i57 B.t.u. FIFTH FLOOR Total for floor 22,632 B.t.u. SIXTH FLOOR Total for floor 23,554 B.t.u. Totals: First floor 8,119 Second floor 9,062 Third floor 41,848 Fourth floor J 6,i57 Fifth floor 22,632 Sixth floor 23,554 122,372 r r> J , 2 ons Required: = 10.2 ;, 60X199.2 416 ELEMENTS OF REFRIGERATION (d) Heat from Goods. The greatest amount received at one time will have to be assumed together with the time required to reduce the goods to warehouse conditions. The cooling is assumed to take place in forty-eight hours. The greatest amount received at any one time is assumed to be the following: Beef, 40,000 Ibs. ; Butter, 6000 Ibs. ; Mutton, 15,000 Ibs.; Poultry, 2000 Ibs.; Pork, 25,000 Ibs.; Apples, 300 bbls.; Eggs, 300 crates; Potatoes, 200 bbls. Heat Removed (see p. 215): From B eef: 40,0001X70 30) X 0.70 +90] = 4,720,000 Mutton: i5,ooo[(7o 3o)Xo.67+Qo]= 1,752,000 Pork: 25,0001(70-30) Xo.5o+9o] = 2,750,000 Eggs: (30oX5o)[(7o-3i)Xo.76] = 444,600 Butter: 6ooo[(7o i5)Xo.6o-h84] = 702,000 Poultry: 2ooo[(7o 20) Xo. 80+102] = 284,000 Apples: (300X1 50) [(70-36) X 0.92] = 1,407,600 Po tatoes: (200^X1 50) [(70 36) X 0.80] = 816,000 Total 12,876,200 rr T> ' 1 I2,876,2OO Tons Required: = 22.4. 48X60X199.2 (e) Heat from Lights (p. 341). In rooms 55X35 there would probably be ten 20- watt lamps. If six rooms are being used at one time the heat from these will be , 10X20X6X3.41 T e = -^ = 0.34 ton. 199.2X60 (/) Heat from Men (p. 214). Assume 10 men working at one time. , 10X1150 T m = =0.96 ton. 199.2X60 (g) Leakage through Doors. This is a difficult quantity to estimate and if the assumption is made that K = 2 and that the PROBLEMS 417 door area is 8x8 and that 10 of these may be open at one time, the following results: = 60X199.2 Totals: Walls .......................... 10.25 Goods ......................... 22.40 Lights ................ .......... 34 Men ............................ 96 Leakage ....................... 6.20 40.15 If 33% excess is allowed for safety the total will be 54 tons. To check this, various general rules will be used. Volume of Building: cu.ft. From Peterson's rule, on p. 256, using 20,000 cu.ft. as the average size of the room and 30 as the average temperature: [20 oooH = 4000; 5000 J Tons required = -- = 104 tons. 4000 From average rule on p. 256: Tons required = ---- = 140 tons. 3000 The difference in these results is due to the assumptions made. In the first case the insulation is heavy and the time to cool goods is moderately long. If this time were made less and the insulation poorer, the tonnage would be increased. In the general rules, there is no specific value for these items. In this problem two 30- ton machines should be installed. 418 ELEMENTS OF REFRIGERATION Problem 4. Find the amount of radiation to be placed in the room for beef storage. Heat from walls = 12,433 B.t.u. per hr. Heat from beef = - = 100,000 B.t.u. per hr. 48 Heat from lights = 20X20X3. 41 = 1364 B.t.u. per hr. Heat from men = 5X1150 = 5750 B.t.u. per hr. Heat from door = 64X2X60 = 7680 B.t.u. per hr. 127,227 B.t.u. per hr. (a) Direct Expansion. tr =30 F.; t a =20F.; # = 5 (p. 244); Using extra heavy 2-in. pipe, i. 608 ft. of length will give i sq.ft. Total Length = 2544X1. 608 =4100 lin. ft. From rules on pp. 255 and 256 the following is obtained: Volume of room ............... 45>5oo Temperature ........... ....... 30 F. Allow f of 25 cu.ft. per lin. ft. on account of first freezing. ' -700 lin. ft " Allow f of 35 sq.ft. per 1000 cu.ft. to allow for freezing in forty-eight hours- Surface = -xx35 = 2350 sq.ft. Lin. ft. = 2350X1.608=3790 lin. ft. Amount allowed for room, 4000 lin. ft. This will be arranged in eight coils 37 \ ft. long and four coils 25 ft. long. Each coil will be five pipes high and two pipes wide. PROBLEMS 419 (b) Brine. Surface, first method, using 7^ difference in place of 10 will require 6100 lin. ft. Levey's table: Lin. ft. =- = 4000 lin. ft.; Schmidt's table: Lin. ft= X-X 50X1.6 = 5460 lin. ft. IOOO 2 Amount to be used, 6000 lin. ft. Problem 5. Find the length of 2-in. brine pipe with a drop of 5 and a mean temperature difference of 7^ F. between room and brine, assuring a 4-ft. per second velocity of brine. Internal area standard 2" pipe 3-355 sq.in. Outside circumference standard 2" pipe . 7461 in. Brine, sp.gr 1.119 Specific heat 0.8 K : 5.0 From (19) p. 259: :. 119X0.8X5 =4260 ft. In table on page 255 it is noted that Levey suggests that these coils be made 275 ft. long. If such is done there will be different conditions from those noted: First, the velocity must be much less than 4 ft., and second the temperature drop will be less than 5 F. Of course, if K is taken as 10 instead of 5, there will be a decrease in length. If i ft. per second is used as velocity, and the drop is taken as 2, although the tempera- ture drop is 7^, and if K is used as 10, the length is found to be about 215 ft. = 2i ft. 420 ELEMENTS OF REFRIGERATION Problem 6. Find the velocity of brine in a 2-in. coil, 190 ft. long, if the mean temperature difference is 5 F., K = $, and temperature drop is 5 F. 13 = 190X^^X5X5 = 2^^X^X3600X62.4X1. 119X0.8X5 12 144 ^ = 0.127 ft. per sec. Problem 7. Find the amount of ammonia which will be evaporated in a 2-in. coil, 190 ft. long, of extra heavy pipe, if the ammonia is at 60 F. before throttling it to 20 F., and the temperature difference is 10 F. Heat from Pipe = 190 X X5X 10 = 5900 B.t.u. per hr. Heat for i Ib. of Ammonia = (ii is) = 512.8(75) p. 69. i for 60 F. and x = o = 30.9 i for 20 F. and x = i = 543.7 Pounds of ammonia per hour = . = 11.5 Ibs. 512.8 Quality of ammonia after throttling to o 30.9 ( 12.6) 20,* = ^- =0.078. 556.3 Specific volume after throttling = 0.078 X 5.92 +0.922 Xo.0244 = 0.484. Velocity of mixture in 2-in. pipe at entrance : w = i23 - ^x 144 = 0.078 ft. per sec. If longer pipes are used a greater quantity will be admitted and a higher velocity will be used. Problem 8. Find the amount of air to be admitted in an indirect system for the data of Problem 4 during the time of filling. Find the surface required in bunker coils. PROBLEMS 421 Heat removed per hour = 127,2 2 7 B.t.u.; Temperature of room, 30 F.; Assumed temperature of air, 20 F. 127 227 Amount of air per minute = '- = 10,602 cu.ft. 10X0.02X60 This assumes that air retains the same amount of moisture. Use i-in. pipes for bunker coils. Assume velocity of air 900 ft. per minute. Area through clear space in bunker 10,602 900 X 144 = 1700 sq.in. If pipes are 6 ft. long and i in. is allowed between pipes, the number of sections will be 1700 - = 24. 72 =6.03, (14), p. 256. Air is cooled from 30 to 20 with ammonia at 15 F. Mean A/ = , ,,=Q.I. fog, Surface = I2 7> 22 7 =232050. ft. 9.1X6.03 or 2320X2.904 = 6750 lin. ft. Lines of pipe per section = '- =47. 24X6 This excessive number of lines and surface is due to the small difference of temperature assumed. If a greater difference in temperature were used, the coil surface would be smaller, but the cost of compression would be greater, as a lower back pres- sure would be needed. This problem has not considered any change in moisture content. If this were taken into consideration, more surface would be required. The problem of heat and surface required 422 ELEMENTS OF REFRIGERATION when there is a change of moisture content is given in Prob- lem 25. Problem 9. Find the size of ducts for air of Problem 8 together with pressure drop, size of fan, and power required. Velocities in System (p. 248) : In register 300 ft. per min. In branches 800 ft. per min. In main 1200 ft. per min. Size of main= I ^=S.S sq.ft., 4 / X2.2 / . Assume main 80 ft. long with 5 bends, 4' X2.2 r . Assume branch 20 ft. long with 3 bends, 2' X i'. (_3JLO\2 Loss in grill = o.8x\? = Q-3 1 (p. 250). 64-3 2O (8_Q_0\2 Loss in branch =o.02X -X Vf =0.83 (p. 240). 4X0.33 64.3 (.800)2 Losshi3bends = 3 Xo.i5X^ - = 1.24. 4-3 g (i 2.0.0.) 2 Loss in main =o.o2X 4X0.71 64.3 8.8 ( i2.AO.N2 Loss in 5 bends = 0.15 X 5 X^-^ = 4.66 04-3 2 Loss in 47 lines of pipe = 47 X 0.4 X^^ = 65.6 64-3 (300) 2 Velocity head at end = J ' = 0.39 04-3 Total loss 76.54 ft. of air. PROBLEMS 423 Oz. pressure = =0.696 (p. 250). no Inches of water =0.696X1.73 = 1.20. Dynamic pressure for Sirocco fan (p. 251)=' 9 =0.977 oz 0.712 Equivalent tabular volume for i oz. = io,6o2 A /- J = 10,750. \o.977 No. 6 fan is the nearest fan in the table. Speed = 38lX J = 376. Discharge = 1 1, 300 X A /-^^ = 11,150. \ i.ooo Power This fan is slightly too large, but using tabular values only it is the one which must be selected. Problem 10. Find the size brine main, size of pump, and power to pump brine for warehouse. For 60 tons capacity and 10 drop in brine, the weight of brine to be circulated per minute is given by (18) p. 259. M 6 Xo.8X 10 = 60X199.2. M b = 1498 Ibs. Volume per min. = = 21.44 cu.ft. = 160 gal. per min. 62.4X1.119 Q T A Area main = ~ X 144 = 12. 9 sq.in. 60X4 Use 4-in. pipe. Area, 12.65 sq.in. This gives a velocity of 4.1 ft. per sec. Duplex pump size to discharge brine at 45 cycles per minute. 424 ELEMENTS OF REFRIGERATION Assume 8-in. stroke. 21.44X1728 45X4X8 = 2S ' Diameter, 5! in. Use 6 X 8-in. brine end to pump. To find power to drive brine through warehouse it would be necessary to lay out all lines, branch circuits and compute losses in various parts. To find, the approximate power it will be assumed that the 4-in. line extends to the top of the building and back again with 200 feet of pipe and eight right-angle bends, and the longest branch, near end, is 400 feet of 2-in. pipe with thirty right-angle bends. The velocity is 0.127 ft. per second in the branch and 4. i f t. per second in the main. The main has branches taken off from it at intervals and is, therefore, equivalent to a main of length equal to one-third of the length on line. From p. 260: , 0.021; /=/ H7 =0.065. (0.17X0.127)* .. 0.33 64.3 0.33 64.3 0.167 2.2 ft. . 64.3 2 64.2 There is no head lost in forcing the brine to top of the system, as the pipe is full. The slight difference in density, due to 10 difference in temperature in ascending and descending pipes, is neglected. Total hydraulic work = 2. 27X1498 = 3410 ft.lbs. per min. Assuming 60% for the mechanical efficiency of pump, the power required to drive pump is 3410 x-[- I.H.P. = - = 0.172 H.P. 33,000 PROBLEMS 425 Problem n. Find the size of supply main for liquid am- monia and return main for vapor for warehouse. Total ammonia per min. = ^ = 23.3 Ibs. (See Prob. 7.) Volume of liquid at 60 F. = 23.3 Xo.o26og= 0.609 cu.ft. 0.600 Area pipe = X 144 = 0.365 sq.m. 4X00 Diameter = f". Use i" extra heavy pipe. Volume of vapor at 15 = 23. 3X6. 583 = 153 cu.ft. (a) From Velocity Considerations. Assume velocity 60 ft. per sec. (p. 257). Area = ^4^X144 = 6.1 sq.in. 60X60 Use extra heavy 3 -in. pipe. (b) From Pressure Drop Considerations. Assume J Ib. drop in 50 ft. of pipe (p. 257). d o.i5i 9 Xd Use 3" for d within bracket. d =3.16. Use $\" extra heavy pipe. Problem 12. Find the size of a freezing tank for a 50-ton plant using 3oo-lb. cans. Size of can from p. 290: 1 1| X 22^ at top, io| X 21^ at bottom, 45 in. length over all, 44 in. length inside. Surface transmitting heat for 42 in. water depth = 20.83 Sq.ft. Heat per hour with 20 brine and a coefficient of 3.3 B.t.u. = 20.83 X(32 -20) X3-3 =826. 426 ELEMENTS OF REFRIGERATION Heat from can = 3001144.3 + (40 32)1=48,390 B.t.u. (Temperature of water from cooler, 40; p. 308.) (Temperature of ice 20 F.) Hours to remove heat = -~- =58.5. 826 (3) P- 34' -2 Time to freeze = ^- = 46.3 hrs. 32 - 20 These do not check, because the value of K used above is lower than can be used. If 4 were used in place of 3.3, the two would check. However, the previous value of 3.3 will be used. If now the temperature of the brine is reduced to 16 F. the heat removed per hour would be 20.83 X (32 - 1 6) X3-3 = i ioo. Hours = 4 hrs. I IOO Total cans per ton per day with 15% allowance 2000 24X300 X44Xi. 15 = 14.1 From p. 305 it is seen that 14 cans are allowed per ton, but 16 cans are allowed by Shipley (p. 307). Using 16, the total number of cans would be Number of cans = 50 X 16 = 800 cans. If this is made 16 cans wide and 50 cans long the tank sizes will be Length = 5o[nJ + 1 + i + i] = 6 2 ' 6"; Width = i6[ Depth=45"+6"=4'3". Problem 13. Find the space required for a plate plant of 50 tons capacity, using ammonia at 16 F. PROBLEMS 427 Volume of ice per day = = 1 740 cu.f t. Total length if 8-ft. depth and i2-in. thickness is used If 6 coils are used, giving 12 plates, the length is given by 12 Using 1 2 -in. clearance the length of the tank will be i2Xi2"+6Xi2"+6"+6" = i 9 '. Tank size= 19' X 18^X3'. Time to freeze = =189 hrs. = 7.9 days = 8 days (P- 34). Eight tanks will be required. Floor space = 43' X 92'. Problem 14. Find the coil surface required for the tank of Problem 12. Heat removed per pound of ice made = 200 B.t.u. (p. 308) L 'I 50X2000X200 Heat from coil= - = 833,400 B.t.u. per hr. 24 Assume 10 difference between ammonia and brine. K=i5 (p. 306). Surface of coil = = 5560 sq.ft. Linear feet of i|-in. pipe = 5560X2. 301 = 12,800 ft. From p. 307 the requirement would be Lin. ft. = 250X50 = 12,500. If 17 coils 60 ft. long are used the coils must be 13 pipes high. 1 XT i_ r 12,800 Number of pipes = J =12.5. This requires 41 in. of height if 3 centers are used. 428 ELEMENTS OF REFRIGERATION Problem 15. Find the tons of refrigeration for plant of Problem 12, if 30 B.t.u. are required for cooling. , r . . 50 X 2000 X (200 +30) Tons of refrigeration = = 80. 2 . 24X60X199.2 Problem 16. Find whether or not ice storage will pay with load curve shown on p. 309. Average machine capacity, 150- tons. Peak load capacity, 325 tons. Ice to be stored with 150 ton machine: May 25X31= 775 June 65X30= 1950 July 175X31 = 5425 August 170X31= 5270 September 130X30= 3900 October 55X31= 1705 Total I 9; 2 5 tons. ,, , r . 19,025X2000 ,, ,, Volume of ice = -^ = 662,000 cu.ft. 57-5 Size of house = 130 X 1 30 X4o = 676,000 cu.ft. Cost of building = 0.06 X 676,000 = $40,560.00. (From p. 344.) Insulation, two 2" cork. 0.40X37,700= 15,080.00. $55,640.00 Yearly cost on building: Interest 6% Taxes and Insurance i% Depreciation 5% Repairs i% / ' - :' - 13% 13% of $55,640.00 = $ 7,233.20 Cost of handling and holding = $0.25X19,025= 4,756.25 (P- 375-) Total cost of storing ice $11,989.45 PROBLEMS 429 Cost of extra apparatus if no storage is used: 175-ton compressor and engine with condenser, piping, receiver, oil separator $ 23,000.00 BoileJ l75X2 - 5X2 = 292 Boiler H.P.Y V 3 / including chimney piping, pump (p. 378) .... 9,000.00 Cans, tank and coils 19,000.00 Distilling apparatus '. 3,800.00 Erection 9,000.00 Additional building space 400,000 at 10 cts. (100X20X20) 40,000.00 Total cost $102,800.00 From p. 347, the cost per ton is $500.00, giving as the probable cost $ 87,500.00 Amount assumed as cost 95,000.00 With 8% depreciation and 3% for repairs the fixed charges willbei8%. Fixed cost per year= i8%X95,ooo = $17,100.00 Additional labor cost 1,500.00 Total $18,600.00 Saving by use of storehouse = $18,600 $i 2,000 = $6,600.00 Problem 17. Find the cost per ton of pumping water for ice in a raw-water plant of 100 tons capacity if the water is 200 ft. below surface, using anthracite buckwheat coal. 100X2000X1.15 ,. Water per minute = ^ = 160 Ibs. 24X60 160X200 Water horse-power = = 0.965. 33>oo (a) Power of steam end of deep-well pump = '^ ** = 1.29 H.P. -75 Steam required = 1.29X1 20 =I 55 lb. (P- 35I-) 430 ELEMENTS OF REFRIGERATION n J u I55XICOO ., Pounds coal per hour = = 16.1 12,800X0.75 Tons of coal for water pumping per ton ice = 100X2240 = 0.00172 ton. Cost of coal for pumping per ton of ice = 0.00172X13.10 = $0.00533. Cost of attendance per ton of ice (50 cts. per ton of coal) = $0.0008. Cost of pump end equivalent part of boiler, assumed $100.00. A.L erf .c j t. r $100.00X0.20 At 20%, fixed charges per ton of ice = 365X100 = $0.00055. Total cost of pumping per ton of ice = $0.00668. (b) Power for air-lift pump= = 2.41 H.P. 0.40 Pounds of steam per hour = 2.41X35 =84.4 Ibs. rr r 84.4X1000X24 Tons of coal per ton of ice = 12,800X0.75X100X2240 = 0.00095. Cost of coal for pumping water per ton of ice = 0.00095 X $3. 10 = $0.00244. Cost of attendance, = $0.00048. Cost of pump end equivalent part of boiler, = $250. ~ ,. . , - , , $250X0.20 Cost per ton of ice for fixed charges = - ^ 100X365 = $0.00137. Total cost of water pumping per ton of ice = $0.00429. Problem 18. Find the steam and surface necessary to evap- orate 40 tons of water per 24 hours, with steam at 5.3 Ibs. per sq.in. gauge pressure and of quality i.oo. PROBLEMS 431 Temperature of steam at 20 Ibs. abs ........ 228 F. Temperature assumed in evaporator ......... 193 F. Pressure in evaporator, Ibs. abs. .... ........ 9 .96 Vacuum in evaporator ..................... 9.7" Heat content of steam entering ............. IJ 57 7 Heat content of steam leaving .............. H44-3 Heat content of water at 193 F ............ 160.92 External surface of evaporator, assumed ..... 250 sq.ft. Heat loss from 2 in. of 85% magnesia = 2 50 X-^ [193 90] T^ = 5408 B.t.u., using (i) p. 302. M,(i 157-7 ~ 160.92) = - [i 144.3 - 160.921 + 5408 = 3,278,000+5408 = 3,283,408. 996-7 4O X 2000 f , ^ (1144.3-160.9) Tube surface required = - - =4205 sq.ft. 400(228-193) This requires thirty-two 4-in. tubes 6 ft. long, using a drum about 5 ft. in diameter. Problem 19. Find the size of filter to be used for filtering the raw water for a loo-ton plant. < 1. 15 = 19.1 gal. per min. 02.5X24X231x00 Allow 2.5 gal. per min, per sq.ft. of filter (p.. 287). Area of deck = ^^ = 7. 6 sq.ft. = 1094 sq.in. Diam. =38''. 2-5 Problem 20. Find the size of compressor to be used for a raw-water ice plant of 100 tons capacity. (a) Find Power. 100 tons requires 1600 cans of 3OO-lb. capacity each . Air required =^ (1.8+0.3) ~ -7 cu.ft. per min. per can. Total air = 0.7X1600 = 1120 cu.ft. of free air per min. 432 ELEMENTS OF REFRIGERATION Assume 90% for volumetric efficiency of a compressor running at 120 R.P.M. Displacement = = 5.2 cu.ft. = oooo cu.in. 0.90X240 Use 20" X 30". Displacement = 9 560 cu.in. . Power required = 0.4X1 oo = 40.0 H.P. (p. 296). Power required for air compressor by calculations to com- press 1 1 20 cu.ft. per minute to 18 Ibs. per sq.in. by gauge will be found to be 64 H.P. Problem 21. Find the power to drive the compressor required for Problem 15, the size of the compressor and parts, the amount of water for the condenser, and the condenser sur- face. Temperature of cooling water 65 F. (See pp. 72, et seq.) Temperature of evaporation 6 F. Temperature of cooling water at inlet. . . 65 F. Temperature of water at point at which ammonia reaches the saturated state . . 80 F. Temperature of after-cooled liquid 7 5 F. Temperature of ammonia in saturated portion of condenser 90 F. Heat content of dry saturated ammonia at 6 F : 540.1 Entropy of dry saturated ammonia at6F. 1.1616 Specific volume of dry saturated ammonia at6F 8.02 Pressure at 6 F 34.60 Ibs. per sq.in. Pressure at 90 F 181 . 80 Ibs. per sq.in. Heat content at 181.8 and entropy 1.1616. 644.0 B.t.u. Heat content of dry vapor at 181.8 558.9 B.t.u. Heat content of liquid at QO F 65.3 B.t.u. Heat content of liquid at 75 F 47 . 8 B.t.u. Temperature of ammonia at end of com- pression 211 F. Specific volume at end of compression. . . 2.18 cu.ft. PEOBLEMS 433 Amount of ammonia to produce 80.2 tons 80.2X199.2 Power to drive compressor^ '^ - 54 ; = 42.42X0.75 102 H.P. The size of the compressor is fixed after the clearance is known. The clearance is made small so as to give a large volu- metric efficiency. The clearances of ^ in. on the upper end and J in. on the bottom end have been used on double-acting cylinders and in single-acting cylinders with a safety head -gV in. and even eV in. have been used on the upper end, while that at the lower end may be anything. With small clearances the clearance volume will amount to about J%. As was pointed out earlier there is no effect of clearance on the work done, except in a slight degree, due to friction from longer strokes with larger clearances. The effect on volumetric efficiency is quite marked and hence, the amount of ammonia handled at a given speed and with it the amount of refrigeration. The York Mfg. Co. has performed a number of experiments on their double- and single-acting compressors with various amounts of clearance and has obtained the results given in the following table: COMPRESSOR I. H. P. PER TON FOR SINGLE-ACTING AND DOUBLE-ACTING COM- PRESSORS WITH VARIOUS CLEARANCES Clearance Volume H.P. at H.P. at H.P. at Linear in % of Displace- ment, S Lbs. Suction Pressure 15.67 Lbs. Suction Pressure 25 Lbs. Suction Pressure Cle arance S.A. D.A. S.A. D.A. S.A. D.A. S.A. D.A. fc" 0.24 1-75 1.30 1.0 9 7T-" o 42 2.18 1. 60 I 26 1" 0.76 0.85 1.77 2-34 1.32 1 .62 1 .10 1.28 r 1.46 1-55 i.Si 2-45 i-34 1.64 1 .11 1.30 i" 2.85 2-93 1.82 2.56 1.36 1.72 I .12 1-35 i" 5.63 5-7i 1.83 2.8 9 1-39 2.OI I-I3 1-44 NOTE. S. A. Single-acting Compressor. D. A. Double-acting Compressor. Clearance Volume includes indicator connections, valve shut. 434 ELEMENTS OF KEFRIGERATION TONNAGE PER 24 HOURS FOR SINGLE-ACTING AND DOUBLE-ACTING COMPRESSORS WITH VARIOUS CLEARANCES Clearance Volume Tons at Tons at Tons at Linear % of Displace- ment 5 Lbs. Suction Pressure 15.67 Lbs. Suction Pressure 25 Lbs. Suction Pressure Clearance S.A. D.A. S.A. D.A. S.A. D.A. S.A. D.A. JL" o 24. 22 7 38 o CQ A. ITf" 0.42 IO 2 -35 O 47 A. r 0.76 0.85 22.6 17-3 37-2 32.1 50.1 45-i i" 1 .46 i-55 21.0 16.0 35-6 30.0 49.1 44-8 i" 2.85 2-93 19.7 14-3 34-4 28.9 47.0 42.3 i" 5.63 5-71 15-5 10.6 29.7 22.9 42.6 36.5 For |% clearance the clearance factor is 1+0.005 o.oo5( : =o - A 34.0 If 5% leakage around valves and piston is assumed the volumetric efficiency is 0.95X0.988 = 0.939. Displacement per min. =^ ^ = 278 cu.ft. 0-939 The piston speed used in refrigeration work varies from 140 ft. per minute in compressors of 5 tons to 500 ft. per minute with compressors of 300 tons capacity. These give 140 R. P. M. for the small compressors and 50 R. P. M. for the large ones. Using 2 compressors with 2 cylinders each at 80 R. P. M. the displacement of one cylinder is Displacement = -- = 0.87 cu.ft. = 1500 cu.in. 2 X 2 X oO Sizes 10X19. 12X13. Either of the above might be used as the ratio of stroke to diameter used in practice varies from 2 to i to i to i. The cylinders are made of close-grain cast iron. They are designed to stand 300 per sq.in., using the ordinary formulae for PROBLEMS 435 cylinder thickness. One-quarter to f in. is added for reboring. The upper portion of the cylinder is jacketed. Valves. The valves should be as large as possible. About 25% of the piston area is sometimes found in valve area. The velocity through the valves may be used to determine the valve area. In this case 4000 ft. per minute is used in the suction valves where the increase of pressure is noticeable, while 10,000 ft. per minute has been used through discharge valves. In any case make the area as large as possible. In single-acting compressors or their equivalent the suction valves are prac- tically as large as the piston. The discharge valves may be single large valves as in the Frick vertical or a number of smaller valves as in the Frick horizontal compressor. Pipe Connections. The pipe connections are of such a size that the velocity is 4000 ft. per minute on the suction side and 8000 on the discharge. F mc =-- X 144 = 4.7 sq.in. or 3-in. extra heavy pipe. "-X 144 = 0.64 sq.in. or i-in. extra heavy pipe. s 2 X oOOO Use 3-in. and 2-in. pipes. Pistons. The ammonia pistons are designed for 300 Ibs. per sq.in. They are made deep. The depth is about equal to the diameter or f the diameter of the piston. Some makers use three piston rings, ground to fit the ring groove, while others use four or five rings. The usual design of rings is made. The pistons are made of cast iron or steel. They are designed as flat plates supported by a series of beams. Empirical constants are found in handbooks of machine design. Piston Rod. The piston rod should be made of high-grade alloy steel and a factor of safety of 10 should be used. The rod is attached to the piston by a thread, using the piston as a nut or using a separate nut. The section at the root of the thread should be designed for tension. The main body of the rod is designed as a column. 436 ELEMENTS OF REFRIGERATION Condenser. Heat removed in superheater portion per pound of ammonia = 644.0 558.9 = 85.1 B.t.u. Heat removed in saturated portion per pound of ammonia = 558.9-65.3=493.6 B.t.u. Heat removed in after cooler per pound of ammonia = 65. 3 -47.8 = 17.5 B.t.u. Amount of cooling water per minute 48.05-33.08 = 17.75 cu.ft. per min. = 132.5 gal. per min. 48.05 =q' at 80 for water; 33.08 = 2' at 65 for water. Temperature of water at end of superheat is given by M 9o=48 . 05+ 3^5 = 48.05 + 2.5=50.55. / = 82.5. Temperature of water at end of aftercooler and entrance to saturated portion is given by M w mo = 33.08+0.51=33.59; ' = 65.5- Temperature Differences: At inlet aftercooler 75 65 = 10 At outlet aftercooler 90 65.5 =24.5 At inlet superheater 90 80 = 10 At outlet superheater 211 82.5 = 128.5 PROBLEMS 437 Mean Temperature Differences: For aftercooler AJ = 24 ' 5 ~ IQ = 16.2 ; For saturated portion AT = 24 '^ = 16.2 ; For superheated portion Ar = * '^ * =46.3. , I2O.S 2.3 log - IO If the water is forced through the double-pipe condenser at 5 ft. per second, the value of K would be 275, from Fig. 94. From formula (18) the value is 291 and by (20) it is 220 with 2-in. and 3-in. pipes. On Fig. 188 the value of K is 100. The value of 200 will be used in the problem. 16.2X200 For the aftercooler 400 will be used for K (p. 187). = 60X32.5X17.5 ft 16.2X400 For the superheated portion (22) p. 188 gives K = $o. 60X32.5X85.1 ^ Fm = -- r^ *- = 122.0 sq.ft. 46.3X30 Total surface with | increase as safety factor = 566 sq.ft. The ordinary rules call for from 8 to 18 sq.ft. per ton. This would give 640 to 1440 sq.ft. The difference between 556 and 640 is due to temperature difference. With water at tempera- tures taken 556 sq.ft. is sufficient. If the condenser is made up of 2-in. and 3-in. pipes and no allowance is made for cooling from the outside, the total length will be Total length = 566 X i .608 = 910 ft. Number of stands of 12 pipes, 20 ft. long = 11$ =4. 438 ELEMENTS OF KEFRIGERATION In Block condensers 9 lin.ft. per ton is allowed. This requires about 720 linear feet. Shipley uses 8 ft. per ton in his improved condenser. Ordinarily with temperatures occurring in practice 25 Im.ft. per ton may be allowed in double-pipe con- densers of 2-in. and 3-in. pipes. In the problem just worked out about ii lin.ft. per ton is used. This is due to the velocity of the water and the assumed temperatures. Problem 22. If one-third of the refrigeration of Problem 21 is possible at 20 F. in place of 6 F., find the size of compressor and power required for this if a Voorhees multiple effect in- stallation is used. Refrigeration at 6 F ................ 53.5 tons Refrigeration at 20 F ................ 26.7 tons Dry compression or x = i at discharge from coils: i" * ...................... 540. i B.t.u. Ao ....... .............. 543. 7 B.t.u. ^750 .............. ........ 47 . 8 B.t.u. V"Q ...................... 8.02 cu.ft. z/ r 2o . ................... 5 . 92 cu.ft. PQ* ..... ........... ... 34-6 #2o ...................... 47-75 53- 5 X 199. 2 21.7 . 540.1-47.8 j,, 26.7X199.2 M 2 ...................... : = 10.8 543.7-47.8 Volume of cylinder for 21.7 Ibs. at 6 = 21. 7 X8.O2 = 174 cu.ft. Volume of i Ib. after adiabatic compression from 34.6 to 47.75, 6.32 cu.ft. Volume of cylinder to care for addition at 20 = 21. 7X6.32 + 10.8X5.92 = 201 cu.ft. If the compressor is built of 174 cu.ft. capacity, the 10.8 Ibs. of ammonia will not be drawn in at 47.75 Iks. pressure and the refrigeration cannot be done while a displacement of 201 cu.ft. PROBLEMS 439 per minute would lower the back pressure in the lower system to 29.3 Ibs. per sq.in. and more work would have to be done. Specific volume = - = 9.28 ; 21.7 Pressure = 29.3. This cannot be changed if it is necessary to divide refrigera- tion, as stated. Condition after mixing is given from specific volume. Specific volume = f f J = 6. 18 ; Pressure =47.75 Ibs. per sq.in.; Temperature =35 F. (superheated 15); Heat content =553.1; Entropy =1.153. After compression to 181.8 the conditions are: Entropy =1.153; Heat content = 638.0. Work of compression = (Mi + M 2) fe ii)+A(p\ po)v = 32- 5[^-553-i]+TT8 i44(47-75-29-3)20i = 3453 B.t.u. per min. I.H.P. of motor = - -- = 108.5. 42.42X0.75 The power required in Problem 21 was 102, so that this is not of any advantage on account of the lower back pressure. If, however, the load could be divided so that a smaller tonnage would be taken, at the higher pressure then there might be some economy. If 18 tons are used at the higher pressure the results are better. ,, 62.2X199.2 Mi= = 25.1 Ibs.; 492.3 -,, 18X199.2 M 2 = - = 7. 2 Ibs. 495-9 440 ELEMENTS OF REFRIGERATION Volume of cylinder for low pressure = 25.1 X8.O2 = 201. Volume of cylinder for high pressure = 2 5. 1X6.3 2 + 7. 2 X5-92=20I.2. This checks and the system will operate. *7OT Specific volume of mixture at 47.75 Ibs. = = 6.21. 3 2 4 Temperature = 35 F. Heat content = 553.0; Entropy =1.153- After compression to 181.8 at entropy 1.153 the heat content is 638. I.H.P. = [32-3(638- 553) +TT 144(47.75-34.6)201] 42.42XO.75 = IOO.2. This means a saving of 2% over the simple arrangement. With other conditions this saving may be greater. Problem 23. Find the quantity of water at 60 F. which gives the most economic results if water for condensing is raised 100 feet from a stream. Use data in Chapter IX to fix costs. Assume temperature in coils to be 5 F. (a) Find cost of producing i ton of refrigeration if tempera- ture of condensation has different values by methods below. DATA COMPUTED FOR DIFFERENT QUANTITIES OF WATER / of condensation 70 75 80 85 90 95 105 p of condensation 129.2 141. 1 153-9 167.4 181.8 197-3 231.2 i 1637 i at end of comp i of liquid at 68 F t of water. 621.3 39-9 65 F. 627.1 68 F. 633.5 70 F. 639.6 75 F. 645.2 80 F. 65L9 85 F. 666.0 95 F. I.H.P Gallons per minute I.H.P. pump Steam per hour for engine . . Steam per hour for pump. . . Total steam per hour Cost of coal and labor in cts . Fixed charges on engine .... Fixed charges on pump . . . Fixed charges on condenser . 1.02 5.56 o. 187 24.5 28 S3. 5 1.07 0.038 o. 105 0.014 I . 10 3-52 0.118 26.4 17.8 44-2 0.88 0.041 0.066 0.009 1.18 2.83 0.096 28.3 14.4 42.7 0.85 0.044 0.054 0.007 1.25 I.9I 0.064 30.0 9 'f 39.6 0.79 0.046 0.036 0.006 1.32 1.44 0.049 31-5 7.8 39-3 0.79 0.050 0.027 0.005 1.41 1.07 0.036 33.8 5-4 39.2 0.78 0.052 0.020 O.O05 1.59 0.85 0.029 38.0 4-3 42.3 0.85 0.059 0.016 0.005 Total in cts per ton per hr. . 1.227 0.989 0.955 0.878 0.872 0.857 0.930 PROBLEMS 441 The method of computing is given as follows: j|f = - E99^ - = 0.308 Ib. per min. 539-9-39-9 I.H.P. _ 42.42X0.75 Gal per min. (65-60)62.4X231 ... .. 1728X33,000X0.75 Steam consumption of engine on compressor, 24 Ibs. per I.H.P. hr. Steam consumption of pump, 150 Ibs per I.H.P. hr. Steam per hr. = 24 X 1.02 = 24.5. Steam per Ar. = 150X0.187 = 28. Cost of buckwheat coal, $3.25 per ton. Cost of firing, 40 cts. per ton. Efficiency of boiler, 65%. Temperature of feed, 200 F., pressure of steam 125 Ibs. abs. Cost of coal per 1000 Ibs. of dry steam _ iooo(iq ) Xcost per ton ~ Heat per Ib.Xeff.X 2240 ' _iooo[ii92.o- 167.951X365 = 2Q ctg> 12,800X0.65X2240 Cost of coal and labor = ^^ X 20 = i .07 cts. 1000 Cost of fixed charges on compressor engine of TOO H.P. size based on 1 5% allowance and 8000 hours of use .feo-ooXi.oaXo.is 8 cts . 8000 There is no allowance for fixed charges on compressor, as com- pressor size is the same in all of these cases. 442 ELEMENTS OF REFRIGERATION . , , $300.00X0.15X0.187 Fixed charges on pump=-^ - - = .105 cts. oooo Condenser surface _ 0.398(^235) X6o 100 X A/ 100X7.5 Cost of condenser at 40 cts. per sq.ft and 15% for depreciation, 18.6X40X0.15 taxes, etc., and 8000 hours = - ~ - =0.014. 8000 From the total of cost it is seen that 1.07 gallons per minute is the most economical rate. If now instead of having water free from a stream it must be purchased at 3 cents per 1000 gallons, the sums above are increased giving the following table: Gallons per minute r r6 "? <2 2 83 i .91 I .44 I .07 0.85 Cost for water free I . 227 o 080 O.O^ 0.878 0.872 0.857 0.930 Cost of water I .OOO O.632 0.510 0.344 o. 259 O.I93 O.I53 Total cost with water 2.227 I.52I 1.465 I .222 I.I3I 1.050 1.083 Cost of water = ^- X 60 X 3 = i .00. 1000 The result is the same as before, although, if these results are plotted into a curve, the most economical rate will be found higher. At 6 cents per 1000 gallons the total cost at 1.07 gallons would be 1.243 c ^ s - against 1.236 at 0.85 gallon; show- ing that at this cost for water, the cost of water would offset the additional cost of power. Problem 24. Find the size of cooling tower to cool the water required in Problem 22 for 80.2 tons of refrigeration with 102 H.P. and a steam consumption of 25 Ibs. of steam per horse-power hour. The water is to be cooled from 95 to 60 F. in 70 weather, with the wet bulb temperature of 60 F. Amount of water from ammonia condenser = 1.07X80. 2 = 85.8 gallons per min. PROBLEMS 443 Amount of water from steam condenser ^102X25X1000^728 Q " 35X60X62.4 ' 231 Total water per minute to tower = 228.8 gallons = 1910 Ibs. Relative humidity from Fig. 92 .......... 0.49 Relative humidity at discharge .......... i . oo Temperature of air at entrance .......... 70 F. Temperature of air at discharge ......... 95 F. Temperature of water at entrance. ...... 95 F. Temperature of water at discharge. . ..... 60 F. Barometric pressure .................... 14.7 Assume volume of air at entrance ......... i cu.ft. Weight of moisture at entrance = 0.001153 X 0.49 = 0.000564. Volume of air at discharge _ 144(14.7-0.49X0.3628) ^ (460+95) _ r 460+70 (14.7-0.815)144 Moisture in air /em>wg = 1.095X0.002474 = 0.002 71 Ib. Moisture absorbed = 0.00271 0.00056=0.00215 Ib. Assume water entering when i cu.ft. of air enters is equal to m". Energy Entering: With water, w"X63.oi =63.01 m" \ VIT-^L i-4 144(14.70.40X0.3628) With air, --X- ' ^ = 9.42; 0.4 778 With moisture, o.ooo565[io8i.5 + (7o 50)0.6]= 0.62. Energy Leaving: . With water, (m" -0.002 15) (28.08) = 28.o8w" -0.06. With air, 14 x 144(14.7-0.815)1.095 = 86 . 0.4 778 444 ELEMENTS OF REFRIGERATION With moisture, 0.00271X1102.3 = 2.99. Equating: 63.01 m"+<). 42 +0.62 = 28.08 m" 0.06+9.86 + 2.99. i -77 = 12.7 m" 12.7 cu.ft. of air must be taken in per Ib. of water entering. 12.7X0.00215=0.0273 Ib. moisture absorbed per pound entering. Total air per minute = 12. 7X1910 = 24,200 cu.ft. per min. With a velocity of 700 ft. per second, this would require a cross- sectional area of = 35 sq.ft. ( S 'X7'.) . An atmospheric tower would require 228X1 = 228 sq.ft. (15X15'.) A cooling pond for this plant would contain 228X70 = 15,960 sq.ft. (160X100'.) The basin for spray nozzles would contain 228X2 = 556 sq.ft. There would be a set of four 2^-in. nozzles, as each would care for about 70 gallons. Two sets would be required for 35 cooling. Problem 25. Find the amount of refrigeration, surfaces for brine cooler, condenser and bunker, and fan size for the air conditioner for a 450-ton furnace (450 tons per day), when the air is at 90 F. and the wet bulb shows 85 F. (a) Refrigeration: Relative humidity (Fig. 93) ........ 0.82 Partial vapor pressure = 0.82 X. 698. . 0.57 Temperature of air leaving ......... 34 F. Assume air required per minute ..... 40,000 cu.ft. Volume of air leaving = 40,000 X I44 / 14 ' 7 ~ ; 57) (460+90) (460+34) 144(14.7-0.0961) PROBLEMS 445 TIT T.^ r 4O,OOO X 144 X (14. 13) Weight of air entermg= -^ = 2700 Ibs. 53-35X550 Weight of moisture entering = 40,000X0.82X0.002 13 7 = 70 Ibs. Weight of moisture leaving = 34,900X0.000327 = 11.4 Ibs. Water condensed per minute = 58.6 Ibs. , , , 58.6X60X24X1728 Water condensed per day - - - = 10.100 gal. 62.4X231 Entering: Energy in air at entrance above 32 F. = 0.24X2790(90-32)= 38,900 Energy in moisture at entrance above 32 F. = 70 X [1097.3 + (90 -34)0.6]= 77,063 Total ............................... 115.963 Leaving: Energy in air at exit above 32 F. = 0.24X2790(34-32= 1335 Energy in moisture at exit above 32 F. = 11.4X1074= 12,250 Energy in water at exit above 32 F. = 58.6X2.01 = 118 Total ................................ 13.703 Heat removed, 115,963 13,703 = 102,260 B.t.u. per min r~ r r - 4- f i 102,260 Tons of refrigeration for air alone = = 513 tons. 199.2 (b) Surfaces required: Air temperature entering, 90 F.; Air temperature leaving, 34 F.; Brine temperature entering, 24 F.; Brine temperature leaving, 39 F. Mean Ar = --- = _ log.fi 2.12 446 ELEMENTS OF REFRIGERATION Assume velocity of air 900 ft. per min. ,-, 102,260X60 ,, F = = 38,200 sq.ft. 19.4X8.5 Use 2-in. pipes, 20 ft. long. Pipe surface = 20 X 7- = 12.45. i. Number of pipes = = 3060 pipes. 12.45 If sections are made up of sections 25 pipes high and 3 sec- tions above each other, the number of rows will be Rows= 3X25 - . 40,000 -, Area for air = = 44.4 sq.ft. 900 Width between rows of tube = - Xi2 =0.65". 41X20 Total length=--- = I ^ 4 y/. If three division walls or plates are placed in bunker, this may be made 13 ft. o in. long. The width of bunker will be 30 ft. to allow 5 ft. at each end. The height will be 75(4" centers) +3 X6" = 26' 6". The heat loss from bunker with 3-in. cork insulation on i2-in. brick will be 2340X [90-2^41 Xo.o7=458o B.t.u. (# = 0.07, p. 211). Tonnage in radiation = = 23 tons. 199.2 Tonnage in 6/^ = 513 + 23 = 536 tons. PROBLEMS 447 Brine coils: Assume ammonia at 9. 0.692 Assume velocity of 5 ft. per sec. From Fig. 95, # = 137. 536X199.2X60 r , F = -- ^ = 2145 sq.ft. 137X21.7 Using i|-in. pipe 20 ft. long and 10 high for one coil, the surface per coil will be 200X = 99-5 s q- ft -> 2.OI Number of coils = 22 coils. 99-5 With no circulation in pipe the rules on Fig. 189 would require 29,315 sq.ft., but in this rule the temperature difference is small. Suppose brine tank is 20X11X8 ft. The surface will be 936 sq.ft. and the heat loss will be 936X0.07X^90-^^] =3800. Tons of Radiation = -~ = 19 tons. 199.2 Total /0?wage = 536H-i9 = 555 tons. Condenser surj 'ace = 5 55X40 = 22 ,200 sq.ft. If the ammonia were in condition of Problem 21, the surface would be 555X7=3885 sq.ft. This would require 12 stands of 2- and 3 -in. double pipe con- densers, each 10 high and 20 ft. long. 3885 y =12.1. 20XIOXI.608 448 ELEMENTS OF REFRIGERATION (d) Fan Size. Pressure in actual plants (p. 321) = 1.2 oz. Use Buffalo conoidal type. Pressure 1.2 oz. Equivalent volume at 2 oz. = 4o,ooo\/ = 51 ,600 cu.f t. per min. Use No. 130 fan; 2 = 226; Actual quantity = 64,700. = 50,000; +J y" 2 64,700 The fan is larger than required, but it is the nearest that can be obtained from table. The fan would be 129 in. high, 6 ft. 6 in. wide and 109^ in. long. Problem 26. Find the amount of refrigeration and power to operate a water-cooling system to supply 1000 men in a plant when the length of the circuit is 5100 ft. arranged in parallel circuits 1700 feet long with 20 elbows. The water is 75 in 90 weather. Men on i shift 600 Quantity of water 600 X| = 150 gals, per hr. = 50 gals, per hr. in circuit = 412 Ibs. Number of fountains - 6 3or = 20 Length of pipe at each fountain, 20 ft. Total length of i circuit, i7oo+- 2 3 6 -X2o=i84O ft. Elbows in i circuit = 4X7 + 20 = 48. (a) Refrigeration: ~, Mean temperature of water, 50 F.; Drop in line temperature, 5 52.5 to 47.5 F, PROBLEMS 449 Using ice water covering and assuming i|-in. pipe, the heat loss is (2 = 1840X0.23(90- 50) = 16,900. Weight of water to care for radiation with 5 fall Ibs. perhr. Area required to give 3-ft. velocity (30), p. 335. 7^ = 0.00562=0.81 sq.in. Use ij-in. pipe. For i^-in. pipe Velocity = 37Q2Xl44 - = 1.2 ft. per sec. 3600X62.4X2.036 Total refrigeration in pipe and water = i6,9boX3 + i2 3 6[75-5o] = 6>8 199.2X60 Loss in two storage tanks of 6 ft. diameter, 10 ft. high = 220X0.07X40 = 617 B.t.u. per hr. = 0.05 ton. Total tonnage = 6. 88 tons. (b) Power required: Head loss ' ^+48X0.2 X^l^ = 13.8 ft. M * 1-5 64.3 I2 12 33,000 X 60 X. 60 UsejH.P. Problem 27. Using data from test of Feb. 5, 1908 (p. 400), reduce refrigerating effect. (a) From brine: Weight of brine per revolution of pump ... 41 . 15 Ibs. Revolutions of brine pump in 15 min ...... 419 Weight of brine per minute, 4 I QX4 I - I 5 = 450 ELEMENTS OF REFRIGERATION Temperature of brine at inlet to cooler ...... 25.nF. Temperature of brine at outlet from cooler. 14.81 F e Specific heat of brine .................... 0.678 Heat removed per minute = ii5oX (25.1 1- 14.81) Xo.6y8 = 8049. Tons of refrigeration = 49 = 40. 2 . 199.2 I-H.P .............. .....: ............. 55.83 I.H.P. per ton ................... 55^3 = I>39 40.2 (6) From ammonia: Mean discharge temperature .......... 146.4 Discharge pressure by gauge .......... 185 . 06 Barometer .......................... 15.01 Absolute pressure .................... 200 . 07 Temperature of saturation ____ , ....... 95. 9 Heat content at 185.06 Ib. and 146.4 F. 595.9 Temperature at expansion valve ........ 58.91 F. Heat content of liquid at 58.91 F ..... 29.8 Temperature in suction ............... 17 . 80 Pressure of suction ............. 20.45 Barometer .................... 15 . 01 Absolute pressure .................... 35 .46 Temperature of saturation ............ 6.5 F. Heat content at 35.46 Ibs. and 17.8 F. . . 547 Ammonia per minute 2 ^ ' =15.8 Ibs. Refrigeration = 15.8(547 - 29.8] = 8180. Tons of refrigeration. --- =41.2. 199.2 PROBLEMS 451 This is slightly greater than the brine result. Cooling = 15.8(595.9 -29.8) =8960 B.t.u. per min. Problem 28. Check data from test of Westinghouse-Leblanc machine. Refrigeration = ^^Xo.833X (18.40- 15.00) =935-8. oo Tons of refrigeration, 935 ' =4.69. 199.2 INDEX A Absorber 32, 137 , tubular ,. . . 37 Absorption machine 31, 79 system 49 Accumulator 279 Adiabatic, construction of 114 After cooling . . ...... . . ... ........ 69 Air 105 blower ...... .... 295 circulation 245 compressors, cost of 351 cooling 318 of churches, hotels, auditoriums .-.-. 322 drying 319 drying design '. 444 for cooling tower I ?6 leakage, heat of 213 lift pump 298 machine advantage 21 operation . . 25 work of compression , 2O pump 283 quantity ... . . 248, 254 refrigerating machines 18 required for raw water ice 295 required for room 420 supply header 295 system closed 19 open 20 velocity 248 Allen 24 Allen dense air machine 19 Ammonia compressors, cost of 351 evaporated, in coil 420 main, size of 425 required 257 Amount of refrigeration for ice making 310 Analyzer , , , , , , , , , , , , , , , , 33 453 454 INDEX PAGE Apples 227 Applications of refrigeration 312 Aqua ammonia 31 , partial pressure 80 , specific heat 83 , specific gravity 83 , temperature of boiling 80 Arctic machine 125, 1 26 Audiffern-Singrun, machine 131 Auditorium air cooling 322 Automatic refrigeration 263 Automobiles, use of 311 B Bananas -.-.. 229 Baudelot cooler 314 Beal 297 Bell-Coleman 21 Belting, cost of . 352 Berthelot 81 Bertsch T6; Binary refrigeration 169 Blast furnace application ... 318 Bohn ice box 13 Boilers, cost of, dimensions of .....:.-... 348, 363, 365 Boiling-point 2 Boyle Union 142 Branch tees 145 Brewery 241 , 314 , refrigeration for 317 Brine 258 , amount of 2 so cooler 160, 163, 164, 306 , forcing ' 259 freezing tank 273 , kind of 2.59 pipe and pump, size 423 , specific heat 258 system 27 245 tank . 34 tank coil 259 velocity determination 420 Buildings, cost of 343 Bunker 247 piping 256 room 323 surface, determination of 421 INDEX 455 C PAGE Cabbages 229 Candling 220 Candy 312 Cans, cost of , 357 Can filler 274 , ice 289 , number of 305 required 426 surface 310 system 269 Car, precooling 264 refrigerated data 381 refrigerator , 13 Carbondale machine 36 Carbon dioxide machine 31, 105, 128 properties 390, 391, 392 Carpentering, cost of 344 Carre 37 Carre" Machines 4 Carrier 51 Carrier's chart 175 Celery 229 Cement wall 201 Central refrigerating plant 260 station load 262 Characteristic equation , 62, 64 Cheese 223 Chemical work 337 Chocolate, specific heat 313 Church air cooling 322 Cleanliness of plants 303 Clearance 433 effect 44, 71, 433 factor 46 Clothing 229 Closed air system 19 Coefficient for brine pipes 306 of transmission of pipes 255 Coil, cooling 18 , cost of 352, 353 , data for 352, 353 surface 310 , amount of 254 , required 427 , testing 123, 124 Coke filter 300 456 INDEX PAGE Cold storage 217 , average length of time 219 for brewery 241 for florists 231 for hotels 238 for markets 232 for packing houses 239 for ships 240 heat loss 243 laws 217 products, value of. 217 with ice 241 warehouses 5 Cole. I. & W 26 Comparison of thermometers 395 Complete absorption, heat of 81 dilution, heat of 81 Compressed air machines 4 Compression, dry 68 , machines 4 refrigerating machine 26 , wet 68 Compressor air, size required 431 , cost of 351 , ammonia, cost of 351 , size required 432 , arctic 125 , De la Vergne 29, 116, 118 , dimensions of 358, 360, 361 , exhausting 125 , Frick 28, 122 , power required 43 2 , single acting 27 , York no , aqua ammonia 31 Condenser 31, 32, 149 Block, cost of 352, 353 , data for '.. 352, 353 , De La Vergne 154 , design ....... 43 6 , double pipe 37 , exhausting , . 1 23 , flanged 152 , Philadelphia 15? , oval flask steam. . . . 165 , screwed .... ... ....... ...- ...... T 53 , Shipley , , . .............158 INDEX 457 PAGE Condenser, submerged 155 , supports 159 , surface steam 165 , welded 151 Conduction 182, 183 Conduits 261 Congealer 233 Constant quality 58 vapor weight line 58 volume line 59 of transmission 187 Construction warehouses 231 Cool brine system 5 Cooler for sweet water > 241 Cooling 46 , by evaporation i , by solution ~- t , by ice . 3 , determination of , 399 , drinking water 331 method of 244 pond 172 pond design 178 tower 167, 169 tower design v 1 76, 442 tower test 406 water 374 Cool water coil 32 Cooper system of refrigeration 18 Cork, best thickness 407 board 201 covering 336 loss. 334 Correction for hydrometer 395 of thermometer' readings 397 Cost of air compressors 351 ammonia compressors 351 belting 352, 353 fan blowers 352 boilers 348 buildings 343 cans 357 carpentering 344 coils 352, 353 condensers 352, 353 distilling apparatus , 357 electric generator 350 458 INDEX PAGE Cost of electric motors 350 engines 349 excavations 340 floors 345 gas engines 350 ice, natural 384 , manufactured 384 storage 309 insulation 345, 346 land 343 lumber "..... 344 machinery 347 masonry 344 millwork 345, 395 miscellaneous apparatus 357 operating 376, 377, 378, 379 partitions 345 painting 345 plumbing 345 pipe and fittings 354 pipe coverings 346 pipe for storage 357 plant, initial 376, 377, 37$, 379 plumbing, initial 345 producers 348 pumps 351 receiver 353 roadway 345 roofing 345 separators 353 space 409 storage 215, 375 supplies 357, 374 switchboard 35 water : 374 Counter current flow 47 Curves, construction of. . . 115 Cream 225 Creamery refrigerators 339 Crosses 145 Curve of ice consumption 308 Cushionhead 109 Cycle diagram 66 Cylinders 116, 120, 122, 434 Cylinder expansion .. . 19 head 29 operation of 123 INDEX 459 Dairy refrigeration 339 Data for coils and condensers 352, 353 engine 349 gas engine 350 ice cream 382 ice delivery 380 ice storage plant 310 Pipes 355, 356 pumps, 351 rinks 382 turbines 349 warehouse '. 383 Deepwell pump 298 Dehydrator 33, 34 De la Vergne 116, 118, 120 machine 30 freezing tank 273 Dense air machine 57 Density of salt 258 Deodorizer 284 Depreciation 206, 379 Design of pistons 435 piston rod 435 Determination from Le Blanc machine test 451 amount of ammonia and air 420 amount of water for condenser and power 432 of best quantity of water 440 of best thickness of cork 407 brine pipe and pump 423 bunker surface 421 coefficient of wall 408 coil surface 427 condenser surface 436 cooling 399 cost of pumping 429 data for air drying 444 fan and power 422 heat loss through walls 413 ice storage 428 length of pipe 419 multiple effect installation 438 number of cans 426 Pipe sizes 43S plate plant 426 radiation 418 refrigeration 396, 398, 428 460 INDEX PAGE Determination refrigerating effect test 449 size of air compressor 431 size ammonia main 425 size of cooling tower 442 of size of evaporator 430 size of filter 431 size of freezing tank 425 specific heat 398 storage space required 410 value of ice storage ". . , . 428 of valve area . . . : 435 velocity of brine 420 water-cooling system 448 Dexter system of refrigeration 1 1 Diagram of cycle 66 Dickinson 16, 258, 308 Diffuser 167 Dimensions of boilers . . . 365 compressors 358, 360, 361 Dimensions of engines 362 generators 368 motors 369 producers 367 turbo-generators 363 Direct-expansion system 5, 27, 245 Displacement 7 Distilled water 79 Distilling apparatus 280 , cost of 357 Distribution of air 246 Door, heat leakage -, 416 construction 208 Drinking water, cooling 331 computations 335 for hotels 33 8 Dry bulb thermometers 5 compression 68 Drying air 3 T 9 Duct, size of 248 Dump, ice 290 Dust preventing 222 Dynamic pressure 2 5 E Efficiency apparatus 347 Eggs 22 , candling 22 INDEX 461 PAGE Eggs, cracking 221 , temperatures of storage . . ; 222 , weight 220 Elbows. . 143 Electric generators, cost of 350 motors 115 welding 140 Elevator 238 Engines, cost of 349 , data 349 , dimensions of 362 , steam 115 Equivalent speed 252 volume 252 Ethyl alcohol 105 Evaporating surface, effect of varying 306 Evaporation, heat of ,. a Evaporator, refrigeration by 26 , design of 283,302,307,430 Excavation costs 244 Exchanger 34, 137 Expander 66 Expansion coils 31 , storage of ammonia in 123 for freezing 306 joint , 262 valve 31, 289 F Fan blowers, cost of and dimensions 352, 353 data 251 , size and power : 422 Fermenting tank 241 tub 315 Filter 276, 286 size required 431 Fish 225 Flange union 141 Flooded system 288 Floor construction 207 insulation 204 costs 345 Fore cooler 284 Freezing by evaporation 37 , coils for .... , 306 , tanks 303 , time of 304 462 INDEX PAGE Freezing tank 273, 288, 303 , size -. 425 Frick Co 27 machine 28, 122, 123, 124, 275 Friction effect 44 loss 249 Fruit 227 Fuels 348 Furs 229 Fusion, heat of 2, 215, 308 G Gauge board 29 Gas Engine 115 , cost of 350 , data 350 Gayley 319 Generator 32, 134 dimensions 368 George. 258 Gobert system 329 Goods, heat from 416 Gorrie 21 Grapes 228 Grease separator . . 285 H Hall, J. & E 26 Hampson 340 Hangers 146 Hart cooling tower 171 Haslam & Co 26 Haynes 38 Head cushion . -. . . 109 Headers 273 Heads 117 , false 119 , spherical 121 Heat content 59 -entropy diagram . . . . * 61 for breweries 317 hem door leakage 4*6 goods 416 men 4 J 6 loss from pipe 334 in cold storage 243 per year .,,,,, 408 INDEX 463 PAGE Heat of air leakage 213 complete absorption 81 partial absorption 81 complete dilution 81 fusion 2, 215, 308 lights 214 machines 214 persons 213 solution 3 of salt 14 vaporization 2 transfer 182 through walls 190 transmission 184 Helmets 1 79 Hoofnagle 38 Hoists 290 Horse-power to drive 47 Hotel air cooling 322 boxes , 238 Hydraulic radius 249 Hydrometer, correction for 295 Hygrometer 50 I Ice, amount of refrigeration 310 and salt mixture ; 223 , artificial , 5 , manufactured 5 , can 289 cold storage 241 cream data 382 cream freezer 326 consumption, curve of 308 , cooling by 3 , cost of storage 309 , delivery data - 380 , distribution 310 , dump 290 , heat of fusion 308 , latent heat of fusion 41 making 265 , absorption system 297 , passenger car 382 plant, Frick 275 , York 270 saw 279 464 INDEX PAGE Ice storage amount and economy 428 plant data 310 room 276 tank insulation 208 Inclined coordinates 62 Incomplete expansion 48 effect 48 Indicator cards 41 , from vapor machines 64 , use of 113 valve 29 Indirect system 246 Injecting liquid, effect of 119 Insulation 190, 201 , amount of 244 , cost of 345, 346 , experimental determination of value 212 values of K 211 Insurance 206, 379 Interchanger 33, 37 Interest 379 Interstate Commerce Rules 181 J Jacket 1 26 , effect of 112 Jackson system of refrigeration 9 Johns-Manville Co 131 K Kirk 21 Kroechel machine 128 L Labor for plants 373 Lagging 112 Land cost 343 Lantern 112 Latent heat 2 of fusion of ice 41 Laws, cold storage 217 Le Blanc 39 machine test 451 Lightfoot machine 19 Lights, heat of , 214 , heat from 416 Lillie evaporator , 300 INDEX 465 PAGE Linde 340 Liquid air 340 Liquid-air machines 341 Liquid line 58 Liquid receiver 341 Lith 201 Load factor 375 Lorenz 329 Loss of heat per year 408 Low temperature by ice and salt . 16 Lubrication 121 Lucke 80 Lumber, costs 344 M Machine, absorption 31 , Carbondale 36 , York 35 Allen dense air 19, 57 compressed air 4 , heat of 214 , Lightfoot 19, 57 , test of 400-405 Machinery, costs 347 Marine compressor 1 29 Market 232 Masonry costs 344 McCray refrigerator $ Methyl alcohol 105 chloride 31, 105 Meat 223 Melons 229 Men, heat from 416 , required 373 Milk 225 Mill work, cost of 345 Miscellaneous apparatus 357 Motors, dimensions of 369 , electric, cost of 350 for driving compressors 115 Moisture effect 50 Mollier 80 diagram 63 Multiple effect 107 , installation 438 , Voorhees , < ........ 71 466 INDEX N PAGE Nozzle design 178 steam 167 O Oil pump ng separator. 31 spray 117 Onions 229 Open air system 20 Operating costs 376, 377, 378, 379 Operation of cylinders 1 23 Oranges 228 Osborne 16, 308 Ott Jewell 297 Oxy-acetylene welding . 140 Oysters 227 P Packing house 239 , leather 1 29 Painting, cost of 345 Partial pressure from aqua ammonia 80 Partial absorption, heat of 81 Partition, cost of 345 Passenger car ice 382 Patten 38 Peaches 228 Pears 227 Penny 169 Performance of plants 370, 371, 372 Perkins '. 4 Perman 80 Persons, heat from 213 Pipe and fittings, cost of 354 Pipe coefficients 255 covering 200, 346 data 355, 356 for storage, cost of 357 heat loss , . 334 joints 142 length, determination of 419 lines, bell and spigot 262 line, brine 262 line, size 257 , size at compressor 435 , size of 38 INDEX 467 PAGE Pipe, suction and discharge 119 Piping 138 arrangement 236 for brine tanks 259 for bunkers 256 for rooms 256 Piston 27, 109, 129 , arctic 126 design 435 rod 121 rod attachment 121 rod design 435 speed 434 Planck 75 Plant cost 376, 377, 378, 379 Plate plant, size of 426 Plate system 269, 276, 297 Plumbing, cost of 345 Plums 228 Poetsch system for shaft sinking 328 Point of boiling 2 fusion 2 melting 2 Pond, cooling, design 178 Poultry 224 Power for deep well 300 plants 370, 371, 372 raw water ice 296 to drive 106 Precooling cars 264 charges 382 Pressure, effect of varying 307 volume diagram 64 Principle of refrigerating machines 5 Problems, absorption machine 83 , air machine 55 , vapor machines 72 , miscellaneous 407-451 Producers, cost of 348 dimensions 367 Properties of ammonia 3 8 7~389 of carbon dioxide 390-392 of sulphur dioxide 393~395 Pump, air lift 298 , cost of 351 data 3Si , deep well 298 468 INDEX PAGE Pump, oil 119 Pumping, cost of 429 Purge valve 29 R Radiation 182 , required 418 Raw water 79, 269 system 290 Reboiler. 274, 282, 284, 285 , vacuum : 283 Receiver 161 Receiver, cost of 353 Rectifier 33, 34; 136 Reduced pressure 3 Refrigerants 105 Refrigerating capacity 41 effect 46 effect, vapor machines 70 effect from test 449 machine compression 26 machines,, general principle 5 machines, diagram of cycle 66 mediums 31 plants, cost of 347 Refrigeration 46 applications of 312 automatic 263 by chemical process . . 40 ice 8 evaporation 26 , central station 260 , determination of 396, 398 for brewery 317 creamery 339 dairy 339 plant 428 methods 8 Refrigerator 8 cars 13 household, data 384 Relative humidity 50 chart 175 Repairs 379 Return bends 31, 144 Return tubular boilers 363 dimensions of 363 INDEX 469 PAGE Rietschel 191 Rinks 326 Rink data 382 Roadway, cost of 345 Roelker 24 Roofing, cost of 345 Rooms, piping for 256 Rooms, temperature of 244, 413 Rugs 229 Rules for safety 180 S Safety devices 1 79 head. . , 29 plate 1 29 Salt, heat of solution 14 Saturated ammonia, properties of 385-387 Saturation line 58 Scale separator 31 Separator 33, 34, "9, *59 , cost of 353 , oil 31 scale , 31 Setting box 312 Shaft sinking ' 328 Ship cold storage 240 Single acting compressor, advantage of 113 Skimmer 283 Solution, heat of 3 Space, cost of 409 , storage, determination of 410 Spangler 8c Specific heat, determination 398 of aqua ammonia 83 brine 15, 258 chocolate 313 ice 16 materials 215 superheated steam 44 vapors 64 Speed, equivalent 252 Spider 109 Spray nozzles 172 Stahl 38 Static pressure 250 Steam for plants 371 washer 300 470 INDEX PAGE Storage, cost of 215, 375 tank 31, 287 unit for 215 Strainer II9 Strawberries 228 Stuffing box 27, 112, 117, 121, 126 Suction side '. . . 29 valve 28 Sulphur dioxide 31, 105 machine 131 properties of 39i"393 Supplies, cost of 357, 374 Superheat, degrees of 63 Sweet water cooler 241 Switchboard, cost of 350 T Taxes 379 Tees 143 Temperature at points on cycle 19 -entropy diagram 57 mean difference 185 of freezing for brine 258 ice and salt mixtures 14 rooms 244, 413 range, effect of 78, 79, 106 Testing coils 1 24 Test of apparatus 395 cooling tower . 406 machines 400-405 Tests 395 Thermit welding 138 Thermodynamics of refrigeration 41 Thermometer comparison 395 correction 397 , use of 169 Thomas spray nozzle 172 Thompson- Joule effect 340 Throttle valve 32 Tilting table , 279 Time of freezing 304 storage 215 Tobacco 229 Tomatoes 229 Tripler 340 Triumph ice machine 127 Tub, fermenting 315 INDEX 471 PAGE Turbines, cost of 349 data 349 Turbo-generators, dimensions 363 Twining 4 Two cylinders, use of 113 U Ulrich 297 Unions 141 Unit for storage 215 V Values of K 187 Valves 121, 148 , cylinder. 117 , hurricane 125 , indicator 29 , manipulation of 123 , mushroom 18 , purge 29 , sizes 435 , slide 18 , Triumph Co 127 Vaporization, heat of 2 under reduced pressure 3 Vapor machine 57 pressure 51 pension .....; 51 Vegetables 229 Velocity of air 248 pressure 250 Ventilating air cooling 322 Vogt Co 134 Volume equivalent 252 Volumetric efficiency 70, 434 Voorhees 71, 107, 438 W Wall coefficient, determination of 408 constants 192 for cold storage 243 heat loss 413 Warehouse construction 231 data 383 \Vater, best quantity of 44 , cooling system design 448 , cost of 374 472 INDEX PAGE Water, distilled 79 , distilled, amount required 300 , effect of large quantities in air 53 for condensing 432 for cooling 374 for ice making 298 jacket 29 jacket, value of 29 per pound of aqua ammonia 81 , raw 79 storage tank 273 tank insulation 337 tube boiler, dimensions 365 Weak liquor cooler 137 Welding 138 Westinghouse 39 Westinghouse Le Blanc machine 167 Wet and dry bulb hygrometer 174 Wet bulb thermometer 50 Wet compression 68 White-wash 222 Wood insulation 202 Work of compression 43 , air machine 20 expansion 43 with friction 44 Y York ice plant 270 machine 36, no, in UNIVERSITY OF CALIFORNIA LIBRARY BERKELEY Return to desk from which borrowed. This book is DUE on the last date stamped below. LD 21-100m.9,'48(B399sl6)476 UNIVERSITY OF CALIFORNIA LIBRARY