Class '! IVoiC i.
Book , H 7 ,
>.'■■
HANDBOOK
FOR
HEATIM AND YENTILATIM
ENGINEEES
JAMES D.%OFFMAN, M. E.
PBOFESSOR OF MECHANICAL ENGINEERING AND PRACTICAJ/
MECHANICS, UNIVERSITY OF NEBRASKA
MEMBER AND PAST PRESIDENT A. 8. H. A V. E.
MEMBER A. S. M. E.
ASSISTflD BY
' BENEDICT P^^RABER, B. S., M. E.
ASSISTANT PROFESSOR OF MECHANICAL ENGINEERING
UNIVERSITY OF NEBRASKA
THIRD EDITION
THIRD IMPRESSION, CORRECTED
McGRAW-HILL BOOK COMPANY
239 WEST 39TH STREET, NEW YORK
6 BOUVERIE STREET. LONDON. E. G.
1913
)
(Copyright, 1913
BY
James D. Hoffman
(First Edition: Copyright, 1911).
By James D. Hoffman)
^ transfer froj^
War Department.
<P
^V^
cv^
•3
EXTRACT FROM PREFACE TO FIRST EDITION.
OTb
— In the development of Heating and Ventilating work, It
?'? IS highly desirable that those engaged in the design and the
(^ installation of the apparatus be provided with a hand-book
Ur? convenient for pocket use. Such a treatise should cover the
entire field of heating and ventilation in a simplified form
and should contain such tables as are commonly used in
every day practice. This book aims to fulfill such a need and
is intended to supplement other more specialized works. Be-
cause of the scope of the work, its various phases could not
be discussed exhaustively, but it is believed that all the fun-
damental principles are stated and applied in such a way as
to be easily understood. It is suggestive rather than diges-
tive. The principles presented are the same as those that
have been stated many times before, but the arrangement of
the work, the applications and the designs are all original.
Many formulas and rules are necessarily given; but it will
be seen that, in most cases, they are developments from a few
general formulas, all of which can be readily understood and
remembered. Practical points in constructive design have
also been considered. However, since the principles of heat-
ing and ventilation are founded upon fundamental thermo-
dynamic laws, it seems best to accentuate the theoretical
side of the work in the belief that if this is well understood,
practical points of experience will easily follow. A pamphlet
containing suggestions and problems for a course of instruc-
tion in technical schools is included with every book.
It is hoped that the material here given will be simple
enough for the beginner and, at the same time, sufficiently
complete and exact for the engineer with years of experience.
If it merits the approval of the reader, or if any part is de-
fective or misleading, we trust that statements of criticism
will be freely contributed. The only way to perfect such a
book Is to have the good wishes and the co-operation ot en-
gineers In all branches of the work. These are solicited.
All the standard works upon the subject have been freely
consulted and used. In most cases where extracts are made,
acknowledgment is given In the text. In addition to this,
references for continued reading are quoted at the close of
each important topic. Because of these references through-
out the book, we do not here repeat the names of their
authors. We wish, however, to express our sincere apprecia-
tion of their valuable assistance.
J. D. H.
PREFACE TO SECOND EDITION.
The demand for copies of the first edition of the hand-
book was so great as to make a second edition necessary
within the second year after publication of the first edition.
A few corrections were made on the first edition and all
the material has been revised to bring It up to date. The
work on air conditioning has been amplified. The descrip-
tions of hot water and steam heating have been improved
by diagrams of the various piping systems. Two chapters
have been added on refrigeration and many tables have
been added in the Appendix. Many suggestions have come
from men In practice and these suggestions have been con-
sidered, thus enlarging upon the practical side and the ap-
plications. It is believed now that every subject discussed
within the scope of the book has been revised to meet the
present state of the science.
Lincoln. Neb. J. D. H.
CONTENTS
CHAPTER I. (Heat)
Arts. Pages
1- 4 Introductory. Measurement of Heat and
Temperatures 9- 13
5 Radiation, Conduction, Convection 14- 15
CHAPTER II. (Air)
6- 9 Composition of Air. Amount Required per
Person 16- 24
10- 13 Humidity 25- 30
14- 15 Convection of Air. Measurement of Air Ve-
locities 31- 34
16- 20 Air Used in Combustion. Chimneys 35- 37
References pn Ventilation 38
CHAPTER III. (Heat Losses)
21- 29 Heat Losses from Buildings 39- 47
30 Teimperatures to be Considered 47- 48
31 Heat given off from Lights and Persons.... 49
References on Heat Losses from Buildings. . 50
CHAPTER IV. (Furnace Heating)
'32- 34 Essentials of the Furnace System.... 51- 53
35- 37 Air Circulation in Furnace Heating 53- 55
38- 47 Calculations in Furnace Design 56- 61
48 Application to a Ten Room Residence 62- 66
CHAPTER V. (Furnace Heating, Continued)
49- 51 Selecting, Locating and Setting the Furnace 67- 71
52- 57 Air Ducts. Circulation of Air in Rooms.... 71- 76
58 Fan-Furnace Heating 77
59 Suggest'ioms for Operating Furnaces 78- 79
60 Best Outside Temperature 79- 83
References on Furnace Heating 84
OHAPTER VL (Hot Water and Steam Heating)
61- 66 Comparison and Classification of Systems... 85- 90
67 Diagrams of Piping Systems 91- 95
68 Accelerated Systems 95- 99
69 Vacuum Systems for Steam 99-102
CHAPTER VIL (Ht. Water and St. Heating, Cont'd)
70- 75 Classification and Efficiencies of Radiators. .103-108
76- 79 Heaters and Boilers. Combination Systems.
Fittings 108-113
CHAPTER VIII. (Ht. Waaler and St. Heating Cont'd)
Arts. Pages
80- 83 Calculation of Radiator Surface 114-121
83- 86 Pipe Sizes. Grate Area. Piping Connections. 121-124
84 General Application to Hot Water Design .. .125-131
88- 89 Insulating Steam Pipes, Water Hammer, . .131-133
yO Feeding Return Water to Boiler 133-137
91 Suggestions for Operating Boilers 137-138
References on Hot Water and Steam Heat'g 139-140
CHAPTER IX. (Mechanical Vacuum Heating)
92- 96 General. Webster, Van Auken, Automatic
and Paul Systems 141-151
97 References on Mechanical Vacuum Heating 152
CHAPTER X. (Mechanical Warm Air Heating)
98-104 General Discussion, Blowers and Fans.
Heating Surfaces 153-165
105-107 Single and Double Duct Systems, Air Wash-
ing 165-168
CHAPTER XI, (Mech, Warm Air Heating, Cont'd)
108-112 Heat Loss. Air Required. Air Tempera-
tures 169-172
113-114 'Air Velocities. Area of Ducts 172-173
115-120 Heating Surface in Coils. Arrangement of
Coils 173-183
121-122 Amount of Steam Used in the System 183
CHAPTER XII. (Mech. Warm Air Heating, Cont'd)
123-129 Air Velocity and Pressure, Horse-Power in
Moving Air 184-195
130-133 Fan Drives. Speeds. Size of Engine. Piping
Connections 195-200
134 General Application to Plenum System 200-205
References on Mechanical Warm Air Heat-
ing 206-207
CHAPTER XIII. (District Heating)
135-139 General. Conduits. Expansion Joints.
Anchors 208-222
140-14t2 Typical Design. Heat in Exhaust Steam 222-228
143-146 Hot Water Systems. General Discussion 229-231
147-149 Pressure and Velocity of Water in Mains. . . .231-235
150-154 Radiation Heated by Exhaust Steam 236-238
155-160 Reheating Calculations 238-244
161-164 Circulating Pumps. Boiler Feed Pumps. .. .244-251
165-169 Radiation Supplied by Boilers and Economiz-
ers 251-255
170 Total Capacity of Boiler Plant 255-258
171-173 Cost of Heating from Central Station 258-263
174 Steam System. General Discussion 264-265
Arts. Pages
175-177 Pipe Sizes. Dripping the Mains 265-267
178 General Application of Steam System to Dis-
trict 268-262
References on District Heating 270
CHAPTER XIV. (Temperature ContiTol)
179-182 General. Johnson, Powers and National Sys-
tems 271-279
CHAPTER XV. (Electrical Heating)
183-185 Discussion and Calculations 280-282
CHAPTER XVI. (Refrigeration)
186-187 Discussion of Systems 283-284
188-189 Vacuum and Cold Air Systems 284
190-191 Compression and Ab'sorptiion Systems 285-288
192 Condensers 289-291
193 Evaporators : 292-293
194 Pipes, Valves and Fittings 294
195-196 Absorption System 294-297
197-198 Generators 298-299
199-203 Condensers, Absorbers, Exchangers and
Pumps 299-301
204-205 Comparison of Systems 302
206 Me.thods of Maintaining Low Temperatures 303-305
207 Influence of Dew Point 305
208 Pipe Line Refrigeration 306-307
CHAPTER XVIL (Refrigeration, Cont'd)
210-212 Calculations 308-312
213-216 General Applicatdon 313-315
217 Cost of Refrigeration 316-317
References on Refrigeration 318
CHAPTER XVIIL (Specifications)
218 Suggestions on Planning Specifications 319-325
APPENDIX.
Tables and Diagrams 327
CHAPTER I.
HEAT — ITS NATURE, GENERATION, USE, MEASUREMENT
AND TRANSMISSION.
1. Introductory: — In all localities where the atmosphere
drops in temperature much below 60 degrees Fahrenheit,
there is created a demand for the artificial heating- of build-
ings. As the buildings have grown in size and complexity
of construction, so also this demand has grown in extent
and preciseness, with the general result that from the
antiquated open fire-place and iron stove, there has devel-
oped a science growing richer each day from inventive
genius and manufacturing technique — the science of the
Heating and Ventilating of Buildings. The purpose of this
hand-book shall be to outline, concisely, the fundamental
principles and practical applications of this science in its'
various branches.
To the heating engineer of to-day, it may be that the
exact nature of heat itself is of much less moment than
its generation and transmission, but this fact should be
impressed, — that heat is one form of energy, that it cannot
be created except by conversion from some other form, and
that it is infallibly obedient to certain physical laws and
principles.
In generating heat to-day for heating purposes, the
almost universal method is combustion. The union of such
substances as coal, wood or peat with the oxygen of the
air is always attended by a liberation of heat derived from
the chemical action of the combination; and this heat is
carried by some common carrier, such as air, water or
steam, to the building or room to be heated where it is given
off by the natural cooling process. In some instances this
heat is converted into electrical energy, which is carried by
wire to the place of use and given off by passing through a
set of resistance coils, which convert it into heat; but this
method is not much favored because of its inefficiency and
the resulting expense. This latter objection would not hold
in the case of water power installation, where the combus-
tion of fuel is entirely eliminated.
10 HEATING AND VENTILATION
2. Meannrenient of Heat: — In the measurement of heat,
the most commonly accepted unit in practical engineering
work is the British thermal unit, commonly abbreviated B. t. u.,
which may be defined as that amount of heat which will
raise the temperature of one pound of pure water one de-
gree Fahrenheit, at or near the temperature of maximum
density, 39.1° F. (See also definition for Specific Heat).
This unit value, the B. t. u., measures the quantity of heat,
while the temperature measures the degree of heat. In
equal masses of the same substance the two are propor-
tional. The Fahrenheit is the more commonly used tem-
perature scale, especially in steam engineering. The unit of
this scale is derived by dividing the distance on the ther-
mometer between the freezing point and the boiling point
of water into 180 equal degrees, the freezing point being
marked 32°, and the boiling point 212°. All temperatures in
this work will be taken according to the Fahrenheit scale,
and all quantities of heat expressed in British thermal units.
There is a second unit of quantity of heat considerably
used, especially in scientific research, known as the calorie,
commonly abbreviated cal., and defined as that amount of
heat which will raise one kilogram of pure water one de-
gree Centigrade, at or near the temperature of maximum
density, 4° C. This Centigrade is a second temperature
scale, the unit of which is derived by dividing the distance
on the thermometer between the freezing point and the
boiling point of water into 100 equal degrees, the freezing
point being marked 0°, and the boiling point 100°.
It is often found desirable to change the expression for
temperature or for quantity of heat from one system of
terms to that of the other. For this purpose the following
formulas will be found useful:
F=^C + S2 and C= {F—32)^ (1)
where F = Fahrenheit degrees and C = Centigrade degrees.
From these equations it may be seen that the two scales co-
incide at but one point, — 40 degrees. For conversion of the
quantity units tlie fullowing may be used:
1 British thermal unit = 0.252 Calorie.
1 Calorie = 3.968 British thermal units.
These are for the ajbsolute conversion ot a certain quantity
of heat from one system to the other. If, however, the
effect of this heat is considered upon a glveriHvoight of sub-
MEASUREMENT OF TEMPERATURE
11
Stai^ce and the "weight also is expressed in the respective
systems, the following values hold:
1 Calorie per kilogram = 1.8 British thermal units per pound.
1 British thermal unit per pound = 0.555 Calorie per kilo-
gram.
Far conversion tables from kilograms to pounds and vice
versa, see Suplee's Mechanical Engineering Reference Book,
page 72, or Kent's Mechanical^ Engineers' Pocket-Book,
page 22.
3. 3Ieasureinent of High Temperatures: — For the meas-
urement of temperatures up to the boiling point of mer-
d.
Fig, 1.
CUry, or approximately 600' F., the mercurial thermometer
of proper range may be employed. It is more common, how-
ever, to use some form of pyrometer for temperatures above
600° F., as when the temperatures of stack gases or of fire
box gases are desired. Pyrometers are built upon many dif-
12 HEATING AND VENTILATION
ferent principles, the graphite expansion stem type, shown
in Fig. 1, a; the thermo-electric type, shown In Fig. 1, b; or
the Siemens water calorimeter type, shown in Fig. 1, c.
Various other methods might be mentioned, one of the best
being temperature determination by the Seger cones, which,
due to varying compositions, melt at different temperatures.
A line of tliese numbered cones is exposed to the sweep of
the gases to be measured, and their temperature determined
very closely by noting the number of the last cone which
melts. The cones are numbered from 022 to 39 and indicate
temperatures from 590° to 1910° F., by approximate incre-
ments of 20°. Fig. 1, d, shows cones 010, 09, 08 and 07, of
which only the last is unaffected, and, from the table fur-
nished with the cones, this indicates a temperature of 1000° F*
4. Absolute Temperature: — In experiments that hav^
been carried on with pure gases with the use of air ther-
mometers, it has been found that air expands approximately
•2-4-Tj- of its volume per degree increase in temperature at
zero F. or -»-4t ^^ ^^^ volume at zero C. From the same
line of reasoning, by cooling the air below zero, the reverse
process should be equally true, that is, for each degree
Fahrenheit of cooling the volume at zero would be contract-
ed -r-i-jr. Evidently, then, if a volume of gas could be cooled
4
to — 460° F., it would cease to exist. This theoretical point
is called the absolute zero of temperature. All gases change
to liquids or solids before this point is reached, however, and
hence do not obey the law of contraction of gases at the very
low temperatures. The fact that air at constant pressure
changes its volume almost exactly in proportion to the abso-
lute temperature, T, (460 + t, where t is temperature Fahren-
heit) gives a starting point to be used as a basis for all air
volume temperature calculations. For instance, if a volume
of 20000 cubic feet be taken in at the air intake of a build-
ing at 0°, and heated to 70°, its volume, by *he heating, will
become greater in the same proportion that its absolute tem-
X 530
perature becomes greater; that Is, = ; x = 23000
20000 460
cubic feet, or an increase of 15 per cent.
Gage and Absolute Pressures. — Two common ways of ex-
pressing pressures are in use. One is denoted by the expres-
sion pressure by gage, and refers to the total pressure in a
container minus the pressure of one atmosphere. Thus the
expression "65 pounds boiler pressure, by gage" means that
MECHANICAL EQUIVALENT OF HEAT 13
the boiler is carrying" 65 pounds pressure, per square inch of
surface, above the pressure of the atmosphere, which is, for
approximate calculations, taken at the standard pressure of
14.696 pounds per square inch. Hence, the boiler carries
within it a total pressure of 65 pounds plus 14.696 pounds or
79.696 pounds pei square inch. This total pressure is what
is known as absolute pressure, and when stated in pounds per
square foot of area, is called specific pressure. Like the volume
of a gas, so also the absolute pressure varies directly with
the absolute temperature, other things being constant. Hence
the equation P V = R T, where P is the absolute pressure
in pounds per square foot, V is the volume of one pound in
cubic feet, T is the absolute temperature, and i? is a con-
stant which for air is 53.22. From this equation, having
given any two of the quantities, P, V or T, the third may be
found.' In very accurate calculations where the value 14.696
is not considered close enough, the barometer may be read,
and its readings, in inches of mercury, multiplied by the
constant .49, to obtain the pressure of the atmosphere in
pounds per square inch.
Mechanical Equivalent of Heat. — ^By precise experiment, it
has been determined that, if the heat energy represented by
one B. t. u. be changed into mechanical energy without loss,
it would accomplish 778 foot pounds of work. Similarly,
one calorie is eqiuivalent to 428 kilogrammeters. One horse-
power of work is equivalent to the expenditure of 33000 foot
pounds of work per minute. Hence one horse-power of
work represents 42.416 B. t. u. per minute.
Latent Heat. — Not all the heat applied to a body pro-
duces change in temperature. Under certain conditions, the
heat applied produces internal or molecular changes, and is
called latent heat. Thus if heat is applied to ice at the freez-
ing point, no rise of temperature is noted until all the ice
is melted; and again, heat applied to water at boiling point
does not raise the temperature, but changes the water into
steam. The first is called latent heat of fusion, and for
ice is 142 B. t. u. per pound, while the latter is called latent
heat of evaporation, and for water is 969.7 B. t. u. per pound.
Specific Heat. — The ratio of the quantity of heat required
to raise the temperature of a substance one degree, to that
required to raise the temperature of the same weig-ht of
pure water one degree from the temperature of its maxi-
mum density, 39.1 degrees, is commonly called the specific
heat of the substance. The above is the accepted rule among
14 HEATING AND VENTILATION
physicists. This, however, has been modified by engineering
practice so tliat tlie statement specific heat of tcatrr is now
understood to mean the average specific heat Oif w«.ter be-
tween 32 degrees and 212 degrees. (Amount of liea-t neces-
sary to raise one pound of water from 32 degrees F. to 212
degrees F.) 4- 180 = 1 approximately. Table 24, Appendix,
gives specific heats of substances.
5. Radiation. Conduction and Convection: — The transmis-
sion of heat, next to its generation, forms an item of vital
interest to the heating engineer, for different forms of heat-
ing installations are based fundamentally on the different
ways in which heat is transmitted. These ways are usually
quoted as being three in number — radiation, conduction and
convection.
Radiation, — This transmission of heat occurs as a wave
motion in the ether of space, and is the way by which the
heat of the sun reaches the earth. Heat of this form, usu-
ally referred to as radiant heat, requires no matter for its
conveyance, passes through some materials, notably rock-
salt, without change or appreciaJble loss, and travels, as does
light, at the rate of 186000 miles per second. In the combus-
tion of fuel the radiant heat given off to the surrounding
metal from the rays of the fire is no doubt of much greater
value than has ever been credited to it. We are indebted
to the noted French physicist, L. Ser, who followed Peclet
in his experiments in radiant heat in fire box boilers, for a
very valuable amount of information. It is to be hoped
that further experimentation "may soon see the relation be-
tween the "heat radiated from the incandescent surface of
the fuel" and the "sensible heat in the escaping gases."
This would be of great value to those engaged in the design
and operation of boiler furnaces.
Conduction. — The second method of transmission is more
commonly evident to the senses. If a rod of metal is heat-
ed at one end, it is known that the heat is transferred, or
conducted, along the rod until the other end becomes heated
also. Conduction being, essentially, the way by which solids
transfer heat, is hence of special significance in the calcu-
lation of heat losses through the walls of a building. Rel-
ative conductivity of a substance may be defined as the quantity
of heat which passes through a unit thickness of the sub-
stance in a unit of time across a unit of surface of the sub-
Btance, the difference of temperature between the two sides
of the substance being one unit of the thermometric scale
HEAT TRANSMISSION
15
Fig. 2.
employed. Since the complexity of our building construc-
tions renders it obviously impossible to reduce all losses to
losses per unit thickness of the structure, we are not per-
mitted to use the term "relative conductivity" but another
term, i. e., "transmission constant," or rate of transmission.
Thus Table IV, page 40, the rate of transmission K, given
for a 6 inch studded frame wall, is .25 B. t. u. per square
foot of surface per degree difference of temperature for one
hour. It is readily seen that this table is the basis for the
heat loss calculations of buildings.
Convection. — Gases and liquids convey heat
most readily by this method, which is funda-
mental with hot air and hot water heating
installations. If it is attempted to heat a
body of water by applying heat to its upper
surface, it will be found to warm up with
extreme slowness. If, however, the source of
heat be applied below the body of water as
in Fig. 2; it will be found to heat rapidly, the
water being distributed by circulating cur-
rents having more or less force, and follow-
ing, in general, the direction shown by the ar-
rows. What actually happens is this: — water
particles near the source of heat become lighter,
volume for volume, than the colder particles
near the top; then, because of the change in
density, gravity causes an exchange of these
particles, drawing the heavier to the bottom and
allowing the heated and lighter particles to rise
to the top, thus forming the circulation currents.
This process is Icnown as convection. It will
never o^ccur unless the medium expands con-
siderably upon being heated, and unless the
force of gravity is free to establish circulating
currents. The hot water heating system may
be considered merely as a body of water. Fig. 3,
furnished with proper pipe circuits. When
heated at one point, the water rises by convec-
tion to the radiators, is there cooled, hence be-
comes heavier, and descends by the return cir-
cuit to the point of heat application, thus completing the
circuit. The warm air furnace installation works similarly,
air, however, being the heat-carrying medium.
ry
Fig. 3.
CHAPTER II.
AIR COMPOSITION — VENTILATION HUMIDITY.
6, Composition of Atniosplieric Air; — The subject of
ventilation as applied to buildings would naturally be in-
troduced by a brief consideration of the properties of the
air supplied. This supply Is a very important factor as re-
gards both quality and quantity. In addition to its value
as a heating medium, it determines, in a large measure, the
health of the occupants of the building.
The human body may be considered as a well equipped
and very complex power plant. As the carbon, hydro-
gen and oxygen in the fuel and air supply in any mechan-
ical power plant are consumed in the furnace, the resulting
heat absorbed in the generating system and finally turned
into work through the attached mechanisms, so the human
body in a similar way, but at a much slower xate, absorbs
the heat of combustion and turns it into work. The prod-
ucts of combustion in both cases are largely carbon dioxide
and water. The chief requisites of the mechanical plant
are good fuel, good draft and good stoking. Similarly, the
human body needs pure food, pure air and healthful exer-
cise. Of the three, the second is probably of the greatest
importance, since no person can keep in health with im-
pure air, even though accompanied with the best of food
and plenty of exercise.
Air, to the average person, is made up of two elements,
oxygen and nitrogen, in the volume ratio of about 20.9 to
79.1 and a density ratio of about 23.1 to 76.9, respectively.
We find in making a complete analysis of pure air, that a
number of other elements and compounds enter into it, mak-
ing a mec4ianical mixture which is somewhat complex. To
the heating and ventilating engineer, however, two im-
portant substances must be added to the two just stated,
and a revision of the percentages will therefore be neces-
sary. It may be said that pure air, as taken from the good
open country and not contaminated with poisonous gases
or the dust and refuse from the cities, would have about
COMPOSITION OF AIR 17
the following composition. See Encyclopedia Britannica,
Respiration.
Oxygen Symbol O Per cent, of volume 20.26
Nitrogen • " N " " " 78.00
Moisture " H2O " " " 1.7
Carbon dioxide " CO2 ' -04
These values are fairly constant, except that of the mois-
ture, which may vary according to the humidity anywhere
from + to 4 per cent, of the entire weight of the air. In
places where the air is not pure, the following substances
may be found in small quantities: carbon monoxide (CO),
sulphuretted hydrogen (H2S), ozone, argon, compounds of
ammonia, and compounds of nitric, nitrous, sulphuric and
sulphurous acids.
In the process of respiration, the lungs and the skin
of the average person will change the composition of the
air film around the person from that given above to
Oxygen ^ Per cent, of volume 16
Nitrogen " " " 75
Moisture " " " 5
Carbon dioxide " " " 4
Comparing these values with 'those for pure air, it will
be seen that the oxygen has been reduced about one-flfth,
the nitrogen has been reduced about one twenty-fifth, the
vapor has increased three times and the carbon dioxide has
Increased one hundred times. Oxygen has been consumed
in its uniting with the excess carbon and hydrogen in the
System, and is given off as carbon dioxide and water vapor.
It may be seen from these ratios, that the very rapid increase
in CO2 'and the accompanying irnpurities of animal matter,
would soon render unfit for use the air in almost any build-
ing occupied by a number of people. To avoid this state of
affairs, fresh -air should be supplied continuously and at
such points as will provide the mo'St uniform circulation.
7. Oxygen and Nitrogen: — The oxygen of the air fills
about one-fifth of the volume in atmospheric air and is the
element that makes combustion possible. The other four-
fifths of the space might be said to be filled with nitrogen.
In a providential way, this nitrogen acts as a sort of buffer
In its mixture with the oxygen and serves to control the
rapidity with which the combustion takes place. Nitrogen
seems to h^ave little effect upon the respiration, except to
18 HEATING AND VENTILATION
retard the chemical action between the oxygen and carbon
and the oxygen and hydrogen. If one were to attempt to
live in an atmospliere of pure oxygen, the chemical action
in the lungs would be so rapid that the human body would
not be able to maintain it.
8. Carbon Dioxide! — The amount of COo in the air is
used as an index to the purity of the air. This is not con-
sidered a. poisonous gas. It has slight taste and odor but no
color. It is found in many natural waters and manufac-
tured beverages, the chief one being "(soda water," which is
made by forcing carbon dioxide into water under pressure.
The real action of CO2 w.hen taken into the lungs is not
well known. It has the effect of producing physical depres-
sion, and where found in sufficient quantity would even cause
death by suffocation, very similar to a submergence in
water. Whatever its effect upon human life may be, its pres-
ence in any room used for habitation is usually an indica-
tion of the lack of oxygen and an excess of impurities thrown
off by respiration. Pure air has four parts CO2 in
10000 parts of air, and room air should never be
allowed to have more than eight 'to ten parts in 10000 parts
of air. It becomes the problem of the heating engineer,
therefore, to provide air in sufficient quantities, and to enter
and withdraw the air from the room in a manner such as
will not be uncomfortable to the occupants, at the same
time keeping the air fairly uniform in quality, throughout
the room. Carbon dioxide in the exhaled breath is about 2.5
times heavier than air of the same temperature, and there-
fore would have a tendency to fall. It is exhaled, however,
with excessive moisture and at a temperature higher -than
that of the room air, both qualities giving it a tendency to
rise. These latter factors probably neutralize the excessive
density, and as long as the air is not absolutely quiet, would
eventually result in a fair diffusion throughout the room
air. In large audiences the heat given off from the occu-
pants is sufficient to cause strong air currents which, in
rising, lift thiis impure air to the upper part of the room.
In mosit systems the vitiated air Is withdrawn from the
room near the floor line. If, as Is urged by some, the ven-
tilating air enters near the floor line and is removed from
the upper part of the room near the celling, the problem
of heating the room will be more difficult and expen'slve.
DETERMINING THE PURITY OF AIK
19
The circulation of air within rooms is being given much at-
tention now and it is hoped that some conclusive results
may soon be obtained. There is no doubt that less air will
be needed for proper ventilation if it is entered and removed
in such a manner and from such parts of the room as will
keep all the air within the room constantly moving and yet
free from localized air currents.
A method of determining the percentage of carbon dioxide in the
air, based upo'n the fact that barium carbonate is nearly in-
soluble in water, may be performed as follows: Provide
eleven bottles with rubber stoppers having two holes each,
and connect them continuously by glass and rubber tubing,
so that if suction be applied at the first bottle of the series,
air will be drawn in at the last of the series and the sajne
air will be passed through all. In this way a sample of the
air to be tesited may be drawn into each bottle. The capac-
ities of the bottles must be made to be respectively, in
ounces, 23y2, Igi/z, leVz, .14, 9i^, 71/2, SVa, 4, 31^, 2i^ and 2.
This may readily be done by partially filling with parafRne.
Into each bottle is then placed V2 ounce of a 50 per cent, sat-
urated solution of barium hydrate, Ba(OH)2. More of the
air to be tested is drawn through the system until assurance
is had that each bottle contains a fair sample. Each bottle is
then thoroughly shaken, so that the liquid may be brought
into good contact with the air sample. If the least turbidity
or cloudiness appears in the
First or largest bottle indicates 0.04 per cent. CO2
iSecond bottle indicates
Third
Fourth
Fifth
Sixth
Seventh
Eighth
Ninth
Tenth
Eleventh "
0.06 '
0.07 '
0.08 '
0.10 '
0.15 '
0.20 •
0.30 '
0.40 '
0.60 '
0.90 '
Care must be taken to have a fair sajnple of the air in
each bottle. The glass tubes through the rubber stoppers
should extend no farther than the bottom of the stoppers.
Vis. 4^ a. shows four of the bottles and their connections.
20
HKATINO AND VENTILATION
As an example, suppose tliat tlie air of a room was tested
and that in the first, second, third, fourth, fifth and sixth
bottles the liquid became turbid after vigorous shaking.
Such room air would have contained 0.15 per cent, of carbon
dioxide, and would have been considered quite unfit for
breathing.
Fig. 4.
A. second, less cumbersome, and more delicate method of testing
for the percentage of carbon dioxide will be described, as it
is the method commonly used and only requires compara-
tively simple apparatus, as shown in Fig. 4, b. A bottle of
about 6 ounces capacity is fitted with a rubber stopper hav-
ing two holes. Through one hole a glass tube is brought
from the bottom of the bottle, and to the outer end of the
tube is connected a valved bulb similar to those found on
atomizers. Into the bottle are placed 10 cubic centimeters
of a solution made by dissolving .53 grams of anhydrous
sodium carbonate, Nao OOs, in 5 liters of water, and adding
.01 gram of phenolphthalein. The water used must have been
previously boiled for at least one hour in an open vessel.
With the apparatus so prepared, squeeze the bulb, thus forc-
ing air from the room through the liquid and into the bot-
tle. The open hole in the rubber stopper is then closed with
the thumb, and the bottle shaken for twenty seconds,
then another bulb-full of air is inserted, and again shaken.
This process is continued and the number of bulbs of air
noted until the red color of the solution, due to the phenolph-
thalein, disappears. This number of bulb fillings is indica-
tive of the purity of the air according to the table below.
After such an apparatus is completed, it must be calibrated
DETERMINING THE PURITY OF AIR 21
before being used. This is done by testing the number of
bulb fillings of pure country air necessary to clear the
liquid, which will usually vary from 40 to 70. A new table
for that special apparatus Is then obtained from the one
given below by proportion. In the table given, this number
of bulb fillings, with purest country air, is 48. If, with the
apparatus made up, it is found that, say, 60 bulb fillings are
required, then the proportionate table would be made by
multiplying the number of bulb fillings given below by the
ratio of 60 -r- 48, or 5 to 4. It is important that the bulb be
compressed the same amount for each filling, and that the
shaking of the bottle and contents be continued the same
length of time after each filling, to obtain uniform results.
TABLE I.
Fillings
Per Cent. CO2
Fillings
Per Cent. CO2
48
.030
15
.074
40
.038
14
.077
35
.042
13
.08
30
.048
12
.083
28
.049
11
.087
26
.051
10
.09
24
.054
9
.10
22
.058
8
.115
20
.062
7
.135
19
.064
6
.155
18
.066
5
.18
17
.069
4
.21
16
.071
3
.25
The methods outlined for tht, approximate estimation of
CO2 are satisfactory for determining whether or not ventila-
ting systems maintain a proper degree of purity of air. If
exact percentages of CO, CO2, O and N are required, the Orsat
apparatus must be employed, for description of which see
Engineering Chemistry by Stillman, page 238. See also Car-
penter, H. & V. B., Chap. II, and Hempel's Gas Analysis,
translated by Dennis.
9. Amount of Air Required per Person: — The need of a
continuous supply of fresh air in our residences and business
houses can scarcely be over-estimated. Health is probably
22 HEATING AND VENTILATION
the greatest of all blessings and pure air is absolutely es-
sential to health. The average adult, when engaged in or-
dinary indoor occupations, will exhale about twenty cubic
inches of air per respiration. He will also have sixteen to
twenty respirations per minute, making a total of 400 cubic
inches or, say, .25 cubic foot of air exhaled per minute. If
as in Art. 6, exhaled air contains 4 per cent. COo, then
the average person will exhale 60 X .25 X .04 = .6 cubic foot
COo per hour, (Pettenkofer, Smith & Parker), which is con-
stantly being diffused throughout the air of the room, thus
rendering it unfit for use. If the carbon dioxide and the
other impurities could be disassociated from the rest of the
air and expelled from the room without taking large quan-
tities of otherwise pure air with it,- the problems of the heat-
ing engineer would be simplified, but this cannot be done.
Because of this rapid diffusion, it is necessary to flood the
room with fresh air in order that the purity may be main-
tained at a safe value. The ideal conditions would be to
have it the same as that of the outside air, but the mechan-
ical difficulties around such a ventilating system, would be so
great as to render it prohibitive. The standard of purity
which should be aimed at, and one, as well, which may be
attained with a first class system, is, .06 of one per cent.
CO2, i. e., six parts of CO2 in 10000 parts of air. A system,
however, which maintains a st-andard of 8 parts in 10000
would be considered fairly satisfactory. This may be put in
a simple form for calculation.
Let Qi = cubic feet of atmospheric air needed per hour
per person; A = cubic feet of CO2 given off per hour per
person; n = vthe standard of purity to be maintained (al-
lowable parts of COo in 10000 parts of air); and p = the
standard of purity in atmospheric air, say, 4; then
A
Oi = (2)
n — p
If we wish to maintain a purity in the room of seven
parts COo in 10000 parts of air, and pure air contains four
parts in 10000, we have Oi = .6 -f- (.0007 — .0004) = 2000
cubic feet of air per hour.
Another formula, quoted from Carpenter's Heating and
Ventilating of Buildings, very similar to the above, is
06
n — 4
AIR REQUIRED PER PERSOl^^ 2S
where a = the purity of the exhaled breath, say 400 parts
in 10000, n = the purity to be maintained in the room and
6 = the cubic feet of air exhaled per minute. Substituting,
as above,
Qi = (400 X 60 X .25) -^ (7 — 4) = 2000 cubic feet.
Based upon .6 cubic foot of CO2 exhaled per person per
hour, Table II gives the amount of air needed to maintain
the various standards of purity.
It should be understood that no hard and fast rule can
be given for the air requirement per person. This, natur-
ally, would be a different amount when considering the
physical development for each person in health; it would
also be different for the same person according to his occu-
pation at the time, sleep 4)eing the least, waking rest some-
what greater, and physical exercise the greatest; but it
varies decidedly with the state of the person's health, or the
sanitary value of his surroundings. According as the degree
of purity is demanded, the air supply must be increased to
suit it.
TABLE II.
Cubic Feet of Air per Person per Hour.
n
A
Qx
6
.6
3000
7
.6
2000
8
.6
1500
9
.6
1200
10
.6
1000
Generally, it is understood that the average adult sub-
jected to average conditions will require 1800 cuMc feet of air
per hour. The amount of air needed for ventilation then in
most cases can be represented by the formula Q' = 1800 N,
where N = the number of people to be provided for.
The following table quoted from Carpenter's H. & V. B.,
and from Morin in Encyclopedia Britannica, gives a fair
value for the amount of air per occupant per hour, that
should be supplied to rooms used for various purposes.
r
24 HEATING AND VENTILATION
TABLE HI.
Hospitals, ordinary 2000-2400 cu. ft. per hour
epidemic 5000
Workshops, ordinary 2000
unhealtliy trades ....3500
Prisons 1700
Tlieaters 1400-1700
Meeting iialls 1000-2000
Scliools, per child 400- 500
" adult 800-1000
Recent practice would tend to increase these values
somewhat; especially those relating to school house ventil-
ation, where a good estimate would be 800 to 1800 respec-
tively.
One ordinary gas burner of 20 candle power, using four
cubic feet of gas per hour, will vitiate as much air as three
or four people. Where many lamps are used, this fact
should be taken into account.
In summing up the subject of fresJi air supply, it is well to call
.attention to the fact that the ordinary running conditions of
any room cannot be absolutely determined by a single test
for carbon dioxide. Trials should be frequently made and
records kept. Upon one day the conditions may be unusually
favorable and would show a small -amount of CO2 even
though a very small amount of fresh air be admitted; while
on other days, when the conditions are not so favorable, a
large amount of fresh air would have to be supplied to main-
tain the proper purity within. If the only requirement,
therefore, governing the ventilation of buildings should be
that a satisfactory CO2 test be passed, there would be a large
opportunity to overrate or underrate, as the case may be,
the ventilating system of the building. The only safe method
in rating ventilating systems is to require a minimum air supply
in addition to a maximum permissible percentage of CO2.
The purification of air by ozonizing it has recently been advo-
cated and by some it is claimed to be the real solution of
the bad air problem. Definite scientific data are still lack-
ing upon which to base any authoritative statements, al-
though the invigorating effects of breathing ozonized air
will be testified to by many. Ozone Is an unstable form of
MEASUREMENT OF HUMIDITY 25
oxygen, probably containing' a greater number of atoms per
molecule, and is formed by passing air through a highly
charged electric field. Because of its unstability as a sub-
stance it readily breaks up and becomes more active as an
oxidizing agent than oxygen itself. In its decomposition a
part goes into combination with substances in the air, such
as carbon impurities thrown off from the human body, and
burns them up, leaving the balance which is probably pure
oxygen. If in the future the purifying effects of ozone are
found to substantiate the claims made by some, ventilation
problems may thus be readily solved by air washing and
ozonizing.
10. Moisture ^vith Air: — Moisture with the air is a bene-
fit to both the heating and ventilating systems in any room.
"Wlith moisture in the room, a person may feel comfortable
when the temperature is several degrees lower than the
comfortable temperature of dry air. Dry air takes up the
moisture from the skin. The vaporization of this moisture
causes a loss of heat from the body, and gives to the per-
son a sense of cold, which is only relieved when the tem-
perature of the room is increased. Air space that is fairly
saturated with moisture will not permit of much evaporation
from the skin, because there is not much demand for this
moisture with the air; consequently the body retains that
heat and the person has a sensation of warmth which is
only relieved by lowering the temperature of the air of the
room. On the other hand, at low temperatures the mois-
ture with air chills the surface of the skin by convection,
a condition that is not so noticeable when the air is dry.
It follows from the above statement that the range of com-
fortable temperatures is less for moist air than for dry air.
Concerning the effect of moisture in its relation to the
heating and ventilating of the room, we may say that thor-
oughly dry air has not the quality of intercepting radiant
heat; moisture, however, has this quality. Moist air has
also somewhat less weight than dry air and is more buoyant.
Because of the possibility of storing up the radiant heat
within the particles of moisture, and, because of its con-
vection qualities, it serves as a good heat carrier for the
heating system.
11. Humidity of the Air: — The actual humiditp is the
amount of modsture, expressed in grains or in pounds per
26
HEATING AND VENTILATION
cubic foot, mixed with tlie air at any temperature. The
relative humidity is the ratio of tlie amount of moisture actu-
ally with the air divided by tlie amount of moisture which
the same volume could hold at the same temperature when
saturated. It is very important that the heating engineer
be able to add to or to take away from the amount of the
moisture in the air supply of any building. To find the
amount of moisture that should be added or subtracted in
any case, it is first necessary to determine the humidity of
the air current at various points along its course. This
may be obtained by the aid of the wet and dry bulb ther-
mometer or by any one of a number
of hygrometers supplied by the
trade. The wet and dry bulb ther-
mometer has a very simple appli-
cation, and is probably in most gen-
eral use. The principle of its ap-
plication is as follows: having two
thermometers, V^g. 5, let one of
them register the temperature of
the room air, the other one being
kept wet by a cloth which covers
the bulb and projects into a vessel
filled with water, shown between
the two thermometers. If tlie air
is saturated the two thermometers
will record the same temperature;
if, however, the air is not saturated
the thermometer readings will dif-
fer an amount depending upon the
humidity. It will readily be seen that
the lowering of the mercury in
the wet thermometer is due to the extraction of the heat
in vaporizing the moisture from the bulb to the air.
In taking readings, let the mercury find a constant level
in each thermometer and then note the difference in tem-
perature between the two. In Table 11, Appendix, at this
difference and at the room temperature read off the rela-
tive humidity; then take from Table 12, Appendix, the
amount of moisture with saturated air at the temperature
recorded by the dry thermometer, and multiply this by the
humidity. The result is the amount of moisture with the
air per cubic foot of volume.
?=— ^-=---. - ■;i
.^""S-^^
XX*s.
/dpi X
f* f X
fffl#f 1
m mtK.
100-
- c\
-no
■100 1
90^
80-
I
! -90 '
r
60-
■
i~ -60 ':
iSO-
■50
40-
*
■M
50-
; 20^
-iO
■20
10-
o-
^
-lO
1 -° '
: ">i
i
« I"
1 lilL
r
\
i
<L^^ .^ _^
Fig. 5.
MEASUREMENT OF HUMIDITY
27
Application. — Room air, 70 degrees; difference in readings,
6 degrees. From Table 11, the humidity is 72 per cent.
From Table 12, col. 7, .72 X .001153 = .00083 pounds pel
cubic foot.
To avoid the necessity for the use of tables, various in-
struments have been designed, which, graphically, give the
relative humidity directly. Fig. 6 shows such an instrument.
commonly known as the hi/grodeik. To find, by it, the relative
humidity in the atmosphere, swing the index hand to the
left of the chart, and adjust the sliding pointer to that de-
gree of the wet bulb thermometer scale at which the mer-
cury stands. Then swing the index hand to the right until
the sliding pointer intersects the curved line which extends
downward to the left from the degree of the dry bulb
thermometer scale, indicated by the top of the mercury
column in the dry bulb tube. At that intersection, the in-
dex hand will point to the relative humidity on scale at bot-
tom of chart. Should the temperature indicated by the wet
bulb thermometer be 60 degrees and that of the dry bulb
70 degrees, the index hand will indicate humidity of 55
28 HEATING AND VENTILATION
per cent., when the pointer rests on vhe intersecting line
of 60 degrees and 70 degrees.
For accurate work any instrument of the tret and dry bulb type
should be used in a current of air of not less than 15 feet per second.
Note. — A very elaborate series of experiments conduct-
ed by Mr, Willis H. Carrier of Buffalo, New York, and pre-
sented as a paper before the American Society of Mechan-
ical Engineers in 1911, seems to show a theoretical humidity
under varying conditions of temperature somewhat different
from that obtained by the U. S. Weather Bureau, which has
always been considered as a standard. Tables 11 and 12,
Appendix, are used as reference in this book but Fig, A fol-
lowing Table 13, shows the variation between the results
obtained by Mr. Carrier and those obtained by the Govern-
ment. The two charts Fig, B and Fig, C in addition to Fig.
A are extracted from Mr, Carrier's work with his permis-
sion. The completeness with which this data has been
worked up permits almost any information desired to be
obtained from these two charts.
12. For Close Approximations and to avoid calculations,
the humidity chart, Fig. 7, may also be used in determining
relative humidity, absolute humidity, dew point, temperature
of wet bulb and temperature of dry bulb. On the left of the
chart is a scale referring to horizontal lines giving tempera-
tures of the wet bulb. The scale on the right hand, referring
to the lines curving downward from right to left, is the ^cale
of the room, or dry bulb, temperatures. The scale along the
bottom of the chart is one of relative humidity. The scale of
numbers up the center of the chart refers to the lines curving
downward from left to right, and indicates the absolute hu-
midity, i. e,, grains of moisture per cubic foot with the air.
The use of the chart may be most readily understood by a
few applications.
Application. — Given dry bulb 70 degrees and wet bulb CO
degrees. Determine relative humidity, absolute humidity,
temperature of dew point for room, etc. First, starting on
the right hand scale at 70, follow down the line this number
refers to until It crosses the horizontal line of 60 degrees,
wet bulb temperature. From this intersection drop to the
relative humidity scale and read there 55 per cent. This may
be checked with the table. To obtain the absolute humidity
't will be noticed that the intersection of the 70 degree and
MEASUREMENT OF HUMIDITY
29
HYGROMETRIC CHART
OIVINO
HYGROMETER TEMPERATURES. RELATIVE HUMIDITY GRAINS OP MOISTURE PER CU FT.
140
130
120
110
100
30 40 50 60 70
RELATIVE HUMIDITY IN t»ER CENT.
Fig. 7.
80
90 100
NOTE. — Fig. 7 represents two charts in one. First: the dry bulb
temperature curve, -tthich drops to the left, unites with the wet bulb
and relative humidity coordinates. Second: the absolute humidity
curve, which rises to the left, unites with the dry bulb and relative
humidity coordinates. This makes it possible to use the two charts ar
one. through the relative humidity scale which is common to both.
30 HEATING AND VENTILATION
55 per cent, coordinates shows 4.4 grains per cubic foot. If the
room should cool, the absolute humidity would remain the
same until the dew point is reached (neglecting air contrac-
tion), hence, following down the 4.4 grain line to 100 per cent.
gives the room temperature as 52 degrees, showing that if so
cooled the air would begin depositing nxoisture at this tem-
perature. Again if the room should heat to 90 degrees, the
relative humidity may be obtained by following the 4.4
grain line to its intersection with the 90 degree coordinate
line of room temperature, and from this intersection dropping
to the relative humidity scale, reading there 31 per cent.
Thus, having given air under any set of conditions, the
effect that a change in any one of these would have upon
the remaining may be obtained without calculations.
13. The Theoretical Amount of Moisture to be Added to'
Air so as to Maintain a Certain Humidity; — -Warm air has a
much greater capacity for holding moisture than cold air.
According to the law of Gay-Lussac, when air is taken
at a given outside temperature and heated for interior
service, the volume increases with the absolute tempera-
ture. See Art. 4. On the other hand the humidity de-
creases rapidly. Air thus treated becomes dry and unpleas-
ant to the occupants, as well as being detrimental to the
furnishings of the room. Some means should, therefore, be
provided to supply this moisture to the air current.
In calculating the amount to be added, let Q = volume
of aiir in cubic feet per hour entering the room at tlie reg-
ister; t = its temperature in degrees and T = (460 + f) =
its absolute temperature; let Q' and Qo = the correspond-
ing volumes after entering and before entering, with
*' and to the temperatures in degrees, and T' =■ (460 + t')
and To = (460 + to) the absolute temperatures; also, let u'
and Uo be the humidities, respectively, of the room air and
the outside air. Then, from the equations
TQ' = T'Q and TQo = ToQ (4)
find Q' and Qo.
From Table 10 or 12, Appendix, find the amounts of mois-
ture M' and Mo in one cubic foot of saturated air at the tem-
peratures f and to; multiply these by the respective humidi-
ties and volumes, and the difference between the two final
quantities will be the amount of moisture required per hour
as expressed by the formula
W = Q'M'u' — QoMoUo (5)
MEASUREMENT OF AIR VELOCITIES
31
A —
Application. — Let Q = 5000, t = 130, f = 70, to = 30, u' = .50,
uo = .50, M' = 7.98, and Mo = 1.935, then
Q' = 5000 X 530 -7- 590 = 4490
Qo — 5000 X 490 -T- 590 = 4154
W = 13896 grains, or 1.983 pounds per hour.
This means that approximately 2 pounds of water would be
evaporated for every 5000 cubic feet of fresh air entering
the register under the above conditions.
14. Velocity in the Convection of Air by the Applica-
tion of Heat:— Let ho Fig. 8, be the height of the chimney
.,£■ or stack. If the temperature of the gasea
'< within the chimney D be the same as that
• of the entering air, then there will be no
— O natural circulation, because the column G D,
will just balance a corresponding column
A B upon the outside; but if the temperature
of the chimney gases C D and entering air
A B he tc degrees and to degrees, respectively,
the chimney gases being (tc — to) degrees
greater than that of the outside air, then,
upon entering the chimney, the gases will
become less dense and expand an amount
proportional to the absolute temperature.
With an outside column of ho feet in height,
it will then require a column within, ho + ho
feet in height to produce equilibrium; in oth-
er words, the column of gas producing mo-
Fig. 8. tion in the chimney has a height of he feet.
Assume, in the system of A B C D E, that the
cross sectio^ns at all points be uniform, then the volumes of
A B (imaginary column) and C E (actual column) are to
each other as their respective heights, i. e.,
Vo :Vo + Vc : : ho :ho + he, or ho : 4Q0 -]- to :: ho + he : 460 + te
From this we obtain he (460 + to) = ho (tc — to) and
ho (tc — to)
6'
ho ^
460 + to
(6)
Substituting for h in the equation v = \/2 gh, its correspond-
ing value he, we have
(7)
V = Vighc = 8.02 ^/ ft" (tc — to)
V 460 -h to
It is found in practice that the theoretical velocity as
given by this formula is never obtained, because of the
32 HEATING AND VENTILATION
friction of the sides of the chimney and other causes. Mr.
Alfred R. Wolff quoted the actual discharge from the chim-
ney as 50 per cent, of the theoretical. This estimate may
be fairly correct for chimneys of the larger sizes, but may
not be realized on the smaller ones used in residences. As
the transverse area becomes smaller, the percentage of fric-
tion increases very rapidly and soon becomes the principal
factor. Prof. Kent assumes a layer of gas two inches thick
next the interior surface as being ineffective. This, If ap-
plied to small cross-sectional areas, increases the size of
the chimney rapidly from the calculated amount.
When formula 7 is applied to hot air stacks in the
heating systems, the friction is much less because of the
smooth interior, and the actual velocity of the air should
reach 60 to 70 per cent, of the theoretical.
15. Measurement of Air Velocities:— See also Arts. 123-
125. In ventilating work it is often of the greatest impor-
tance to determine air velocities accurately. The correct de-
termination of the sizes of air propelling fans or blowers
depends upon the ability to accurately measure the velocity
of delivery. In acceptance and other tests this measurement
is equally important. However, no entirely satisfactory and
trustworthy method of obtavining this measurement has as
yet been devised.
The velocity of moving air is most commonly measured
by means of a vane wheel instrument called the anemometer.
It consists essentially of a delicately pivoted wheel holding
from 6 to 15 vanes and similar to the common wind-mill
wheel. See Fig. 9. To the shaft is connected a recording
mechanism of some sort, the simplest
being merely dials which show the
velocity of the air traveling past the
instrument, by the reading of which
against a stop-watch, the speed per
unit of time may be obtained. Since
the instrument works ag«,inst the
friction of movdng parts, its readings
are subject to serious variation, and
even with frequent calibration, it is
not to be relied upon where results
are required accurate to within 20
per cent. Various tests of anemom-
Filg. 9. eters by comparison to the absolute
PITOT TUBE
33
reading's of a gas tank have shown errotrs as high as 35
per cent, slow, to 14 per cent, fast, with the discharge from
pipes 8 inches to 24 inches in diameter. Hence, in general,
it is very safe to say that the anemometer as an instrument
for velocity measureiment in precise work should be used
with great care.
A second method of velocity measurement, and one
applying as readily to liquids as to gases, is that of using
the Pitot tube principle. "Whenever, in a liquid or gas, a
pressure produces a flow, part of this pressure, usually
termed the velocity head, is considered as transformed into
velocdty; while a second part, usually called the pressure
head, acts to produce pressure in the fluid. If now, as at
A, in Fig. 10, a tube be inserted into a pipe carryingr *
Fig. 10.
current of air or other moving fluid, and the end Of this
tube be bent so the plane of the opening is perpendicular
to the direction of the flow, a pressure in the tube will
result, due to both the velocity head and the pressure head;
and the difference in levels in the connected manometer
tube will indicate this sum of pressures in terms of inches
of water or mercury. If, however, a tube be inserted as at
B, with the plane of its opening parallel to the direction
of the flow, a pressure in the tube will result, due only
to the pressure head in the moving fluid; and the difference
in levels in the connected manometer tube will indicate this
pressure only. Then, by subtraction of the two manom-
eter readings, the velocity head only is obtained, expressed
in inches of water or mercury, whichever the manometer
may contain. v*
At C is shown the instrument as commonly applied,
with both tubes together and connected one to either leg
of the manometer tube so that the subtraction is automatic
34
HEATING AND VENTILATION
and the difference in levels read is caused by the velocity
only. Having, then, the head of pressure due to velocity,
to find the actual velocity apply the formula v = VYgh where
V = velocity in feet per second, g = acceleration of gravity
in feet per second, per second, and h = the velocity head of
the air in feet. If the manometer contains water, then,
at 60 degrees, the ratio between the specific gravity of air
62.37
- = 816.4. See Tables 12 and 8, Appendix.
and water is
.0764
Hence the above formula may be reduced to the more read-
ily available form of
«=V'
2 X 32.16 X 816.4 X
12
or
r = 66.2 V /iio
(8)
where hu> = the difference in height in inches of the columns
of a water manometer, with both legs connected as described,
and a temperature of 60 degrees. By a similar method the
formula may be reduced for a mercury or other manometer,
or for other temperatures than 60 degrees. (See Art. 1021,
Trans. A. S. M. E. Vol. XXV.)
In using the Pitot tube or the anemometer, the fact
should not be lost sight of that the velocity varies from
a minimum at the inner walls of the tube to the maximum
at the center of the tube. It seems that the friction at the
Inner walls throws the moving fluid into a number of
concentric layers, those toward the center moving the fast-
est, those toward the Inner wall of the pipe the slowest.
With a circular tube, the variation of velocities of these
different layers may be approximately represented by the
abscissae of a parabola, Fig. 11, with its axis on the axis of
the circular pipe. Weisbach, on page 189 of his Mechanics of
Fig. 11.
CHIMNEYS 35
Air Machinery, quotes tlie average speed at two-thirds of the
radius from the center, this value being obtained by ex-
periments. For conduits of other shapes the position of
mean velocity must be determined experimentally. This
variation of velocity from the center of the stream less-
ening- tow^ard the walls may possibly account for the varia-
tions shown by the anemometers. It is evident that
if such an instrument, with a given diameter of vane
wheel, be placed at the center of a pipe of large radius it
would tend to register a higher velocity than the average.
Automatic recording meters may be obtained for keep-
ing permanent records of the flow of air and steam through
pipes and ducts. The record from the meter indicates direct-
ly the cubic feet of free air or other fluid used during each
hour of the day.
16. Amount of Air Required to Burn Carbon: — The chief
product in the combustion of carbon with the oxygen of the
air is CO2. The atomic weight of carbon is 12 and that
of oxygen is 16, hence the chemical union of the two form-
ing CO2 is in the proportion of carbon 12 and oxygen 32
or as 1 : 2.66. For each pound of carbon consumed, 2.66
pounds of oxygen will be needed and the product will weigh
3.66 pounds. If pure air contains 23 per cent, oxygen, then
one pound of carbon will need 2.66 -^ .23 = 11.7, say 12
pounds of air for complete combustion. One cubic foot
of air at 32 degrees weighs .0807 pounds, then 12 -f- .0807 =
148 cubic feet of air necessary to burn one pound of car-
bon if all the oxygen of the air is burned. With volumes
proportional to the absolute temperatures, this air at 70
degrees would be 160 cubic feet; at 200 degrees, 200 cubic
feet; at 400 degrees, 260 cubic feet; and at 600 degrees, 320
cubic feet.
17. Probable Amount of Air Used: — It seems reason-
able to assume, however, that in practice from two to three
times as much air goes through a furnace as would be
needed for perfect combustion. Taking this at 2.5, then the
cubic feet of air found from the above would be approxi-
mately: 32 degrees, 370 cubic feet; 70 degrees, 400 cubic
feet; 200 degrees, 500 cubic feet; 400 degrees, 650 cubic feet;
and 600 degrees, 800 cubic feet.
18. To Determine the Transverse Area of a ChlmneT-
for Any Given Heigrht: — Substitute ho and the assumed
36 HEATING AND VENTILATION
values of to and io in formula 7, Art. 14. From this find
the velocity of tlie chimney gases, and divide the total
volume of air used in any given time, Art. 17, by the corre-
sponding velocity.
19. Application io the Chimney of a lO-Room Resi-
dence: — Given: total heat loss from the building per hour,
10000 B. t. u.; coal, 13500 B. t. u. per pound; furnace
efficiency, 60 per cent.; temperature at bottom of chimney,
200 degrees F. ; height of chimney, 30 feet above the grate;
average temperature of chimney gases, 150 degrees. (The
greatest difficulty is experienced when the fire is first
started before the chimney is warmed up. The temperature
of the stack gases at such a time is very low.) Take the
outside air temoaerature, 40 degrees F., and find the size of
the chimney.
A heat loss of 100000 B. t. u. per hour will require
100000 -^ (13500 X .60) = 12.4 pounds of coal per hour at
the grate; 'then wdth a temperature of 200 degrees at the
bottom of the chimney, this will need to pass 500 X 12.4 =
6200 cubic feet of air per hour. The velocity of the chim-
ney gases, according to formula, is 20.5 feet per second or
73800 feet per hour. Assuming the real velocity to be
25 per cent, of this amount, we have approximately 18450
feet per hour; then the net sectional area is 6200 -^ 18450
= .34 square foot or 49 square inches. To fit the brick
work this would probably be made 8 inches X 8 inches.
20. All Chimneys should have a Smooth Finish on the
Inside: — -Probably the best arrangement that can be made
is to build the chimney of hard burned brick around hard
burned tiles of suitable internal size. These tiles can be
had of outside sizes such that they can easily be made to
work in with the brick work. Table 15, Appendix, shows
chimney capacities that will be safe in average practice.
Flues should preferably be made round in section, as this
form presents less friction to the gases than any other.
Flues should never be built less than ten inches in diam-
eter, or eight by ten inches rectangular. Tlie value of a
flue depends very much upon the volume of passage due
to area, and velocity due to height. Velocity alone is no
proof of good draft for there must also be sufficient area
to carry the smoke. The top of a chimney with reference
CHIMNEYS 37
to its position relative to neighboring structures is a very
important consideration. If the top is below any nearby
portion of the building, eddy currents tending to enter the
top of the flue may be formed and seriously reduce the draft.
Under such conditions a shifting cowl, which always turns
the outlet away from adverse currents, may be advisable.
Good draft is very essential to the success of any type of
heating system, and the purchaser of a furnace or heater
should be required to guarantee sufficient draft before a
maker is expected to guarantee a stated rating of his
furnace or heater,
38 HEATING AND VENTILATION
REFERENCES.
References on Ventilation und the Air Supply
Technical Books.
Moore, The School House, p. 24. Monroe. Steam Heat, d Vent.,
p. 99. Carpenter, Heat, d Vent. Bldgs., p. 21. Hubbard, Power,
Heat. & Tetit., p. 408. Allen, Notes on Heat. & Tent., p. 91.
Ency. Brit., Vol. XXIV, p. 157, also Vol. XX, p. 474.
Technical Periodicals.
Engr. Rev., Sanitation and Ventilation in Boston School
Houses, W. B. Snow, March 1908, p. 15, Subwy Ventilation,
J. B. Holbrook, Jan. 1905, p. 18. Ventilation of School Rooms,
Nov. 1905, p. 6, Heat. & Yent. Magazine. A Scotchman's Notes on
Ventilation, Alex. Mackenzie, May 1906, p. 15. Air Analysis as
an Aid to the Ventilating- Engineer, J. R. Preston, Oct. 1906,
p. 11. Domestic Engineering. Ventilation in its Relation to Health
W. G. Snow. Vol. 52, No. 4. July 23, 1910, p. 102; Vol. 52, No.
6, Aug. 6, 1910, p. 154. Ventilation of Isolated Offices. C. L.
Hubbard, Vol. 45, No. 10, Dec. 5, 1908, p. 274. Humidity,
Its Necessity and Benefits, W. W. Brand, July 1910.
The Permanent Place of the Air W'asher in Heating
and Ventilating Work, Feb. 1910. Trans. A. S. H
d V. E. The Necessity of Moisture in Heated Houses, R. C.
Carpenter, Vol. X, p. 129. Need of Ventilation in Heated
Buildings, Vol. X, p. 183. Changing the Air in a Building,
Vol. X, p. 285. Effect of Humidity on Heating Systems, Vol.
IX, p. 323. Necessity of Ventilation, H. Eisert. Vol. V. p. 57.
The Engineering Magazine. Humidifiers, — Their Principles and
Useful Applications. S. H. Bunnell. June 1910. The Heating,
Ventilating and Air Conditions of Factories. P. R. Moses,
Aug. and Sept. 1910. Engineering Record. Ventilation of Three
Basement Floors of the Marshall Field Retail Store, Chica-
go, Jan. 23, 1909. Ventilation of a Newspaper Photo-En-
graving Plant, June 26, 1909. Ventilation of the First
Church of Christ, Scientist, Boston. Sept. 19, 1908. The Ven-
tilation of a Weave Shed, Aug. 8, 1908. Ventilation of the Bat-
tery Tunnels of the New York Subway Extension to Brook-
lyn, Oct. 5, 1907. Railway Tunnel Ventilation, Feb. 20. 1904.
Railtcay Age Gazette. Detroit Return Trap System, July 23,
1909, p. 175. Washington Union Station Ventilation. June
12, 1908, p. 84. Heating and Ventilating the Storage Battery
Stations on the New York Central & Hudson River, April
13, 1908, p. 489. Ventilation and Heating of Engine Round-
houses as Adopted bv the New York Central Lines. June 18.
1909, p. 1335. The Metal Worker. A Remarkable Theatre Ven-
tilation Plant. Jan. 15. 1910. p. 63. An Interesting Factory
Ventilation Plant. Jan. 15. 1910. p. 90. Ventilation of Factories,
A'uditoriums. Stores and Schools in Chicago. Mav 7. 1910, p.
634. Ventilation in Relation to Health, Wm. G. "Snow. June
25. 1910, p. 866; July 30. 1910. p. 142. Heating and Ventilat-
ing Plant Complying with Factory Law, July 10. 1909. p.
41. Heating from a Physician's Standpoint. Mav 14. 1910.
p. 658. Ventilating a Restaurant. Sept. 25. 1909. p. 39.
CasHier'H Magazine. The Purification of Air. Oct. 1910.
CHAPTER III.
HEAT LOSSES PROM BUILDINGS.
21. Loss of Heat by Conduction and Radiation: — In
planning- the heating system for any building, the first and
probably the most important part of the work is to esti-
mate the total heat loss per hour from the building. Un-
fortunately this is the part which is the least open to
satisfactory calculations and we find little valuable theo-
retical data upon the subect.
Heat is lost from a building in two ways, by radiation
and by convection, 1. e., that transferred through walls, win-
dows and other exposed surfaces by conduction and lost
by radiation; 'and that carried off by the movement of the
air as it passes out through the openings- in the building
to the outside air. The radiation loss is usually of greater
importance, but the convection loss is of much more im-
portance than is generally considered. In the average
building both of these values are difficult to determine.
Radiation losses are considered under various heads,
such as glass, wall, floor, ceiling and door losses. Concern-
ing the conduction of heat through these various materials,
the available data have been obtained by experimentation
and do not agree very closely. Peclet in France, and Gras-
hof, Rietschel, Klinger and Rechnagel in Germany, each
carried on experimental research to determine the heat
transmission through various materials and structures.
These published data form the basis for a large part of the
heat loss calculations of the present time. Much valuable
material can be found in the more recent writings of
Hood, Wolff, Box, Carpenter, Kinealy, Allen, Hogan, Hub-
bard and others, but many of the values quoted are only
rough approximations at best. The reason for so much
uncertainty in this part of the work is found in the fact
that there are such great differences in methods of build-
ing ^ '^onstruction. Conductivity tests for the various ma-
terials have been satisfactorily made, but when these same
materials have been put into a building wall the quality
of the workmanship often permits more heat loss by con-
40 HEATING AND VENTILATION
vection than would be transmitted through the materials
themselves. The values quoted for brick walls and glass
agree fairly well. The greatest difficulty is found in the
balloon-framed building with its studded walls, where the
dead air space in a well constructed wall may be a good
non-oonductor, or where, on the other hand, the same space
in a poorly constructed wall may become a circulating air
space to cool the walls by the movement of the air.
Table IV has been compiled from a number of the
best references as stated above, and represents a fair aver-
age of all of them. The value K (rate of transmission), in
some of the references, varied for the same material, being
somewhat greater for small temperature differences than
where the temperatures differed widely. In general, the
transfer af heat through any substance is about propor-
tional to the difference of the temperature between the two
sides of the substance. This was noticeably true for most
of the quotations.
TABLE IV.
Conductivities of Building Materials.
it = B. t. u. transmitted per sq. ft. per hour per degree dif.
Materials. K.
Brick wall, 8" 4
Brick wall, 12" 31
Brick wall, 16" 26
Brick wall, 20" 23
Brick wall, 24" 21
Brick wall, 28" 19
Brick wall, 32" 17
Brick wall, furred, use .7 times non-furred in each case.
Stone wall, use 1.5 times brick wall in each case.
Windows, single glass '. i.O
Windows, double glass 6
Skylight, single glass 1.1
Skylight, double glass 7
Wooden door, 1" 4
Wooden door 2" 36
Solid plaster partition, 2" 6
Solid plaster partition, 3" 5
Ordinary stud partition, l-ath and plaster on one side 6
HEAT LOSSES FROM BUILDINGS 41
Ordinary stud partition, lath and plaster on two sides.. .34
Concrete floor on brick arch 2
Fireproof construction as flooring 1
Fireproof construction as ceiling 14
Single wood floor on brick arch , . .15
Double wood floor, plaster beneath 10
Wooden beams planked over, as flooring 17
Wooden beams planked over, as ceiling 35
Walls of the average wooden dwelling 25 to .30
Lath and plaster ceiling, no floor above 62
Lath and plaster ceiling, floor above 25
Steel ceiling, with floor above 35
Single %" floor, no plaster beneath 45
Single %" floor, plaster beneath 26
Occasionally it is convenient to reduce all radiating
surfaces to equivalent wall surface and take account of the
heat losses as a part of the wall.
The following equivalents for doors, floors and ceilings
have been found to give good results:
Doors not protected by storm doors or vestibule = 200% of
equal wall area.
Floor over unheated space. Air circulation = same as wall.
Floor over unheated space. Still air = 40% of equal wall area.
Ceiling below unheated space. Air circulation = 125% of
equal wall area.
Ceiling below unheated space. Still air = 50% of equal wall
area.
In all references from French and German authorities,
one is impressed by the extreme care and exactness with
which every detail is worked out, even to those minor parts
usually considered in this country of no special moment.
Table IV has been reduced to chart form, Fig. 12, where
the table values agree with — 10° outside temperature and
wind velocity. The application of this chart is as follows:
Assume the outside temperature — 10°, still air, inside tem-
perature 70°, south exposure. WTiat is the heat loss from
a square foot of 12 inch brick wall, also from a square foot
of single glass window? Beginning at the right of the
chart at — 10° outside temperature trace to the left to the
wind velocity, then up the ordinate to the 12 inch wall
42
HEATING AND VENTILATION
(interpolate between 8 and 16), then to the left to the line
indicating 70" inside temperature, then down to the south
exposure, then to the left showing 25 B. t. u. transmitted
Fig. 12.
per hour. For the glass, trace from — 10° to the wind
velocity, then up to the single window, then to the left to
the inside temperature, 70°, then down to south exposure.
ESTIMATION OF HEAT LOSS 43
then to the left showing- 80 B. t. u. per square foot per hour.
Checking this with the table for a 12 inch brick wall we
have .31 X 80 = 24.8 B. t. u. For glass 1 X 80 = 80. The
values given in the table must be increased for west, north
and east exposures. The effect of the wind velocity upon
the heat loss is very ^marked. Locations subjected to high
winds should have extra allowance made. For example,
take the 12 inch brick wall just mentioned. Assume the
wind to be 30 miles an hour. By the same process as before
we find for a south exposure, 36 B. t. u. loss as compared to
25 with wind velocity.
22. L.OSS of Heat by Air Leakage : — The exact amount
of air leaving a building by leakage is impossible to de-
termine. Many experiments have been carried on in the
last few years to determine the amount of leakage around
windows and doors. These in the specific cases have been
successful, but no actual values can be quoted for general
use. Again, a considerable amount of air passes through
the walls, thus rendering the case more complicated. In all
the experiments, however, it has been found that these
losses have been much greater than was supposed. In rooms
not heavily exposed, or in touch w^ith heavy winds, two
changes per hour may be safely allowed for all leakage
losses.
23. Exposure Losses and Other L.osses: — Radiation
losses are much greater on the exposed or windward side of
the building. Moving air passing over the surface of any
radiating material will wipe the heat off faster than would
be true of still air. The north, north-west and the north-
east in most sections of the country get the highest winds
and have the least benefit of the sun and are therefore
counted the cold portions of the building. In figuring a
building it is customary to figure each room as though it
were a south room, which is assumed to need no additions
for exposure, and then add a certain percentage of this
loss for exposure to fit the location of the room. The exact
amount to add in each case is Largely a matter of the judg-
ment of the designer, who, of course, is supposed to know
the direction of the heavy winds and the protection that
is afforded by surrounding buildings. A wide variety of
values covering the American practice might be quoted for
this, but the following will give satisfactory results:
44 HEATING AND VENTILATION
TABLE V.
North, north-east and north-west rooms heavily exposed,
10-20 per cent
East or west rooms moderately exposed .... 5-10 per cent.
Rooms heated only periodically 20-40 per cent.
The German practice is somewhat more extreme than
ours in this part of the work:
North, north-east and north-west rooms heavily exposed
15-25 per cent.
East and west rooms 10-15 per cent.
Surfaces exposed to heavy winds 10-20 per cent.
Heat interrupted daily but rooms kept closed 10 per cent.
Heat interrupted daily but rooms kept open 30 per cent.
Heat off for long- periods 50 per cent.
Rooms 12 to 14% feet from floor to ceiling .. 3 per cent.
Rooms 14% to 18 feet from floor to ceiling ... 6 per cent.
Rooms 18 feet and above from floor to ceiling 10 per cent.
24. Loss of Heat by Ventilation: — A certain amount of
fresh air leaks into every building and displaces an equal
amount of warm air, but this amount of fresh leakage air
is not considered sufficient for good ventilation. When
warm air is displaced either by leakage or by ventilation,
it is exhausted to the outside air and as it leaves the room
carries a certain amount of heat with it. This is a direct
loss and should be taken into account.
Since the loss by leakage is practically the same for
all systems of heating, it is accounted for in the ordinary
heat loss formula, but losses by ventilating systems must
be considered In '^xcess of this amount. Let Q' = cubic feet
of fresh air supplied per hour, t' — to = drop in temperature
from the inside to the outside air; then the heat lost by ex-
hausting the air, Art. 27, is
0' «' — to)
55
25. Two General Methods of Eiitimatinsr the Kent Loss B
from a Bulldlngr arc in Common line: — First, estimate all
radiation losses and add to their sum a certain per cent.
ESTIMATION OF HEAT LOSS 45
of itself to allow for leakage by convection; second, esti-
mate all radiation losses and add to their sum a certain
amount which depends upon the volume of the room. The
first is by Equivalent Radiating Surfaces only and the second is
by Equivalent Radiating Surfaces and Volume combined.
26. Method No. 1: — Figuring by Equivalent Radiating
Surface. — Let H ■-- B. t. u. heat loss from room per hour;
G = exposed glass in square feet; W = exposed wall minus
glass, plus exposed doors reduced to equivalent wall surface
in square feet; F = floor or ceiling separating warm room
from unheated space; tn = difference between room temper-
ature and outside temperature; tv = difference between
room temperature and temperature of the unheated space;
K, K' and K" = coefficients of heat transmission; o = per-
centage allowed for exposure and h = percentage allowed
for loss by leakage, varying in per cent, of other losses
from 10 in the average house to 30 in the house of poor
construction.
From the above, we have
H = (KGtx + K'Wtx + K"Fty) (1 + a + 6) (10)
(Application. — ^Assume the sitting room. Fig. 15, to have
a total exposed wall surface, W, exclusive of glass, 242
square feet; total exposed glass, (?, 38 square feet; and
floor, F, 195 square feet. Assume that all the rooms are
heated to 70 degrees with an outside temperature of zero
degrees and that all workmanship is fair. Assume also the
floor to be of the ordinary thickness and not ceiled below, with
a temperature below the floor of this room of 32 degrees;
and that two people are using the room. Under such con-
ditions what is the heat loss from the room? Since this
is a south room there is no exposure loss and a = 0. Then
assuming 6 = .20 we have
H = (1 X 38 X 70 + .3 X 242 X 70 + .45 X 195X 38) (1 + .20)
= 13270 B. t. u.
Good judgment will be necessary in selecting the proper
outside temperature for the calculation. The value of this
outside temperature varies -among men in the same locality
as miuch as 20 degrees. In t'he above application if to = —
20° and the 'temperature of the unheated space below the
floor remains at 32 degrees, formula (10) becomes H = 15946
B. t. u. See discussion of this point under Art. 60.
46 HEATING AND VENTILATION
27. Method No. 2: — Figuring- by Equivalent Radiating
Surface and Volume. — The general formula for this is
H = iKGtm + K'Wtm + K"Ftv + oc nCU) (1 + a) (11)
where U, K, O, U, ty, W, F and a are as given above; = oubic
volume of the room; n = number of times the air is sup-
posed to change in the room by leakage and convection per
hour, recommended, 1 to 2; oc = -^ and is usually taken .02
for convenience of calculation. This constant refers to the
heat carried away by the air. The specific heat of the air
at 32 degrees is .238; then the number of pounds of air
heated from 32 to 33 degrees by 1 B. t. u. is 1 -r- .238 = 4.2.
Now if the weight of a cubic foot of air at 32 degrees is .0807
pounds, we would have 4.2 -^ .0807 = 52 cubic feet of air
heated from 32 to 33 degrees by 1 B. t. u. However, most
of the heating is not done at from 32 to 33 degrees but
from 32 to 70 degrees, in which case, the volume of air
heated from 69 to 70 degrees by 1 B. t. u. is 52 X 530 -r-
492 = 56 cubic feet. See absolute temperature. Art. 4. It
is evident that some approximation must here be made. No
exact value can be taken because of the great range of
temperature change of the air, but 55 is commonly used
as the best average. The difficulty of handling formula
with the constant ^ has Jed to the simple form .02. (See
55
last column Table 12, Appendix.)
Application. — With the same room as used in Application
1, we have, if a = 0,
^ = (1 X 38 X 70 + .3 X 242 X 70 + .45 X 195 X 38 +
.02 X 1 X 1950 X 70) (1 -f 0) = 13806 B. t. u.
28. Method No. 3t — Professor Carpenter reviews the
work of the various authors and quotes bhe following
formula, which Is the same as that given in Method No. 2
in a more simplified form, with the terms the same as
before:
H = (O + .25 TF + .02 nC) U (12)
In his opinion 'the very elaborate methods sometimes used
are unnecessary. K may be assumed .25 for any ordinary
wall surface, brick or frame, and the ceilings adjoining an
attic or the floors above a cellar of the average house need
not be considered. Floors above an unexcavated space
where no heat is obtained from the furnace and where there
ESTIMATION OF HEAT LOSS 4/
Is more or less circulation of air should no doubt have
some allowance. This would probably be the same as given
in Art. 21. The values of n are quoted by the same author-
ity as follows:
"Values of w.
Residence heating, halls, 3; sitting room and rooms on the
first floor, 2; sleeping rooms and rooms on second floor, 1.
Stores, first floor, 2 to 3; second floor, 1*^ to 2.
Offices, first floor, 2 to 2^^; second floor, li/^ to 2.
Churches and public assembly rooms, ■% to 2.
Large rooms with small exposure, ^ to 1.
Applicatiok. — Assuming the same room as before,
Zr = [38 + .25 (242 + .4 X 195) + .02 X 2 X 1950] 70 = 13720.
29. Combined Heat Loss H^ = (H + Hv) : — In buildings
where ventilation is provided, the total heat loss is that lost
by radiation, H, + that lost by ventilation, Hv, (isee also Art.
36). Letting Qv = cubic feet of air needed per hour for
ventilation, we have
Qv tx
H' — H -\ (13)
55
Rule. — "-To find the total heat loss from any building, add to
the heat loss calculated by formula, the amount found by multiply-
ing the num,ber of cubic feet of ventilating air exhausted from the
building per hour by one-fifty-fifth of the difference between the in-
side and outside temperatures.
30. Temperatures to be Considered: — The tem-perature
maintained in heated rooms in this country is 70 degrees.
Outside temperatures used in figuring heat losses are gen-
erally taken, southern part, + 10 degrees; northern part —
20 degrees; ordinary value, degrees. (See Art. 60.)
The German Government requires estimates on the fol-
lowing temperatures, as quoted in "Formulas and Tables
2o< Heating," by Prof. J. H. Kinealy.
48 HEATING AND VENTILATION
TABLE VL — Values of t'.
The temperatures of heated rooms are generally as-
sumed by the German Engineers to be as follows:
Rooms in which the occupants are for the most part at rest:
Living rooms, business rooms, court houses, offices,
schools 68
Lecture halls and auditoriums 61 to 64
Rooms used only as sleeping rooms 54 to 59
Bath rooms in dwellings 68 to 72
Sick rooms 72
Rooms in which the occupants are undergoing bodily ex-
ertion:
Workshops, gymnasiums, fencing halls, etc., in which
the exertion is vigorous 50 tO 59
Workshops in which the exertion is not so vig-
orous 61 to 64
Rooms used as passage rooms or occupied by people in
street dress:
Entrance halls, passages, corridors, vestibules 54 to 59
Churches 50 to f>i
Miscellaneous:
Prisons for tlie confinement ot prisoners during
the day 64
Prisons for the confinement of prisoners during
the night 50
Hot houses 77
Cooling houses 59
Bath houses:
Swimming halls 68
Treatment rooms, massage rooms 77
'Steam bath 113
Warm air bath 122
Hot air bath 140
ESTIMATION OF HEAT LOSS
49
TABLE VIL
Values of to When Applied to a Room.
The temperatures of rooms not heated are quoted as
follows, with the outside air at 4 degrees below zero:
Cellars and rooms kept closed 32
Rooms often in communication with the outside air,
such as passages, entrance halls, vestibules, etc. 23
Attic rooms immediately beneath metal or slate
roof 14
Attic rooms immediately beneath tile, cement, or
tar and gravel roof 23
31. Heat given off from Lig^hts and from Persons
Within the Room: — As a credit to the heating system, some
heating engineers take account of the heat radiated from
the lights and the persons within the room. The following
table by Rubner is quoted by Prof. Kinealy:
TABLE Vlli.
Gas, ordinary split burner, B. t. u. per candle power hr. 300
Gas, Argand
Gas, Auer
Petroleum
Electric, incandescent
Electric, arc
200
31
160
14
4.3
According to Pettenkofer, the mean amount of heat
given off per person per hour is 400 heat units for adults
and 200 for children.
50 HEATING AND VENTILATION
RBFERENCBS.
References on Heat Liosses and Radiation.
Technical Books.
Snow, Principles of Heat., p. 54. Carpenter, Heating and
Ventilating Bldgs., p. 64. Hubbard, Potcer, Heat, and Vent., p. 417.
Allen, Notes on Heat, and Vent., p. 13.
Technical Periodicals.
Engineering Review. Air Leakage Around Windows; Its
Prevention and Effects on Radiation, Harold McGeorge, Feb.
1910, p. 64. The Heating and Ventilating Magazine. Austrian Co-
efficients for the Transmission of Heat through Building Ma-
terials, W. W. Macon, Feb. 1908, p. 36. Air Leakage through
Windows and its Effect Upon the Amount of Radiation, B.
S. Harrison, Nov. 1907, p. 18. Air Leakage Around Windows
and its Prevention, H. W. Whitten, Dec. 1907, p. 20. Deriva-
tion of Consrtants for Building Losses, R. C. Carpenter,
March 1907, p. 34. Methods of Estimating Heat Losses from
Buildings, C. L. Hubbard, Sept. 1907, p. 1. Trans. A. 8. H. A
V. E. Heat Losses and Heat Transmission, Walter Jones,
Vol. XII, p. 233. Loss of Heat through Walls of Buildings,
R. C. Carpenter, Vol. VIII, p. 96. Engineering Record . An In-
vestigation of the Heat Losses in an Electric Power Station,
Jan. 16, 1909, p. 77. Derivations of Constants for Bldg.
Losses, R. C. Carpenter, Feb. 23, 1907. p. 214. The Metal Worker.
Humidity of Air and Its Determination, with Chart, Aug. 21,
1909, p. 56. Heating Water by Steam, Sept. 18, 1909, p. 53.
Coal Consumption in Two English Hot Water Heating
Plants, Sept. 19, 1908, p. 47. School House Warming and
Ventilation, Serial, Jan. 6, 1906, p. 58. Potcer. Heat Trans-
mission through Corrugated Iron, A. H. Blackburn, Oct. 29,
1912. Coal Required to Heat Modern City Building, E. F.
Tweedy, Jan. 16, 1912.
CHAPTER IV.
FURNACE HEATING AND VENTILATING.
PRINCIPLES OF DESIGN.
32. Furnace Systems Compared Trltli Other SystemM: —
The plan of heating residences and other small buildings
by furnace heat, in which the air serves as a heat carrier, is
a very common one in this country. Some of the points in
favor of the furnace system are: low cost of installation,
heating combined with ventilation, and the rapidity with
which the system responds to light service or to sudden
changes of outdoor temperatures. Compared with that of
other heating systems, the furnace system can be installed
for one-third to one-half the cost. In addition to this, the
fact that ventilation is so easily obtained, and the fact that
a small fire on a mild day may be sufficient to remove the
chill from all the rooms, give this method of heating many
advocates. The objections to the system are: cost of operation
when outside air is circulated, difficulty of heating the
windward side of the house, and the contamination of the
air supply by the fuel gases leaking through the joints In
the furnace. In a good system well installed, the only
objection to be seriously considered is the difficulty of heat-
ing that part of the house subjected to the pressure of the
heavy wind. The natural draft from a warm air furnace
is not very strong at best and any differential pressure
in the various rooms will tend to force the air toward the
direction of least resistance. The cost of operating can be
controlled to the satisfaction of the owner, consistent to his
ideas of the quality of the ventilation needed. Arrange-
ments may be made to carry the warm air from the room
back again to the furnace to be reheated, in which case,
if the fresh air be cut off entirely, the cost of heating is
about the same as that of any system of direct radiation
having no provision for ventilation. Any amount of fresh
air, however, may 1 '^ taken from the outside for the pur-
pose of ventilation, thus requiring the same amount of air
62
HEATING AND VENTILATION
to be exhausted at the room temperature and causing an
increased cost of operation, as discussed in Art. 36.
33. Essentials of the Furnace System: — Fundamentally,
this installation must contain: first, a furnace vipon proper
settings; second, a carefully designed and constructed sys-
tem of fresh air supply and return ducts; and third, the
warm air distributing leaders, stacks and registers. Fig.
13 shows, in elevation, a connmon arrangement of these
essentials, and gives, also, the air circulation by arrovv
Fig. 13.
directions. The installation shown is rendered flexible in
operation by the basement dampers, proper adjustment of
which will allow fresh air to be taken from either side
FURNACE HEATING 53
of the house or furnished to the pit under the furnace by the
duct from the first floor rooms. This return register Is
usually placed in the hall, under the stairway, or in some
room which is generally in open connection with the other
roomis on the first floor, as a large living room.
34. Points to b,e Calculated in a Furnace Design: — Be-
sides the calculated heat loss, H, which of course would
probably be the same for all methods of heating, other
points in furnace design would be taken up in the follow-
ing order: first, find the cubic feet of air needed as a
heat carrier and determine if this amount of air is sufllcient
for ventilation; then calculate the areas of the following:
net heat register, gross heat register, heat stack, net
vent register, gross vent register, vent stack, leader pipes,
fresh air duct and total grate area. From the total grate
area the furnace may be selected.
35. Air Circulation in Furnace Heating; — The use of air
in furnace heating may be considered from two standpoints,
each very distinct in Itself. First, air as a heat carrier;
second, air as a health preserver. The first may or may not
provide fresh air; it merely provides enough air to carry
the required amount of heat from the furnace to the rooms,
i. e., to take the place of the heat lost by radiation plus
the small amount that is carried away by the natural in-
terchange of air from within to without the building, as
would be true in any residence that is not especially planned
to provide ventilation. With certain allowable temperatures
at the various parts of the system, this volume of air may
be easily calculated. One point here should be remembered:
when the cubic feet of air per hour as a heat carrier is
found at the register, this volume remains the same, no
matter if it enters the furnace through a duct from within
or without the building. So this plan may be both a heat
carrier and a ventilator if desired, subject only to the
amount of air required. The seco- plan requires that
enough air be sent to the rooms to provide ventilation. If
this amount is less than that needed as a heat carrier, all
well and good, the first amount will be used; but if it
should be greater, then the first amount will need to be
Increased arbitrarily to agree. This increased volume will
then be used instead of that calculated as a heat carrier
54 HEATING AND VENTILATION
only. As previously stated, the cubic feet of air per hour
as a ventilator may be taken as 1800 N, where N is the
number of persons to be provided for. See Art. 9.
36. Air Required per Hour as a Heat Carrier :»A safe
temperature /, of the circulating air as it leaves the heat
register, is 130 degrees. This may at times reach 140 de-
grees but it is not well to use the higher value in the
calculations. If, as is nearly always the case, the room
air temperature, f, is TO degrees, the incoming air will
drop in temperature through 60 degrees and, since one cubic
foot of air can be heated through 55 degrees by one B. t. u.
(see Art. 27.), it will give off 60 h- 55 = 1.09 (say 1.1) B. t. u.
Let Q = cubic feet of air per hour as a heat carrier: H
= total heat loss In B. t. u. per hour by formula; t = tem-
perature of the air at the register; and f = temperature of
the room air; then
55 H
Q = (14)
t — f
Rule. — To find the cubic feet of air necessary to carry the heat
to the rooms, multiply the heat loss calculated by formula by fifty-
five and divide by the difference between the register and the room
temperatures.
For ordinary furnace work this becomes
H
Q =
1.1
Now if this air is not allowed to escape from the building,
Jig. 13, but is taken back to the furnace and recirculated,
the only loss of heat will be H, that calculated by the
formula; but as a matter of fact, air thus used would soon
become contaminated and wholly unfit for the occupants to
breathe, hence, it is customary to exhaust through ventil-
ating flues, either a part or all of the air sent from the
furnace. This makes an additional loss of heat from
the building corresponding to the drop In degrees from 70
to that of the outside air. Let the temperature of the out-
side air, to, be degrees, then the resulting heat loss would
be (see also Art. 110 on blower work.) H' = U plus (f — to)
divided by 55 and multiplied by the amount of air intro-
duced for ventilation. Stated as a formula for the special
conditions, this becomes
H' = H + 1.27 Q, (15)
FURNACE HEATING ff6
Take for illustration the Sitting Room, Pig. 15, and
consider it under three conditions on a zero day: first, when
all the air is recirculated; second, when only enough air is
exhausted to give good fresh air for ventilation; third,
when all the air is exhausted. Under the first case the loss
H, by formula is, say, 14000 B. t. u. per hour and no other
loss is experienced. In the second case, let three people oc-
cupy the room and allow 1800 cubic feet of fresh air per hour
for each person, or a total of 5400 cubic feet per hour, then
the total heat loss from the room will be. Formula 13,
14000 + 5400 X 70 -^ 55 = 20873, say 21000 B. t. u. The
third case, where all the air is exhausted, gives 14000 -j- 1.1
= 12727 cubic feet of fresh air exhausted at 70 degrees,
which requires the same amount of fresh air being raised
from zero to 70 degrees to replace it. This necessitates the
application of 12727 X 70 -i- 55 = 16198 B. t. u. additional,
or a total heat loss of 30198, say 30000 B. t, u. per hour.
The second condition is that which would be found most
satisfactory. It is evident from inspection that the cubic
feet of air necessary as a heat carrier will supply excessive
air for ventilation in the average residence, and the de-
signer need not necessarily consider the amount of air for
ventilation except as he wishes to investigate the size of
the furnace, the amount of coal burned or the cost of
heating; the latter being in direct proportion to the respect-
ive total heat loisses. (See also Art. 60.)
Application. — Referring to Table IX, page 63, the calcu-
lated amount of air per hour for the various rooms and for
the entire building may be found.
37. Is this Amount of Air Sufficient for Ventilation if
Taken from the Outside? — Take the 13 X 15 X 10 foot sitting
room, Fig. 15. Let the estimated heat loss be 14000 B. t. u.
per hour, then Q = 12727 cubic feet. With a room volume
of 1950 cubic feet, the air will change 6.5 times per hour,
and, allowing 1800 cubic feet of air per person, will supply
seven people with good ventilation if fresh air be used.
Stated as a formula,, this would be
B B
N = = approx. (16)
1.1 X 1800 2000
As a matter of fact, ventilation for half this number would
be ample in an ordinary residence room excepting on extraor-
56 HEATING AND VENTILATION
dinary occasions. So it would seem that the subject of
ventilating air will be more than taken care of if the ducts
and registers are planned to carry air for heating purposes
only.
38. Given the Heat Loss H and the Volnme of Air Q' for
any Room, to find t, the Temperature of the Air Entering at
the Register: — If for any reason Q is not sufficient for ven-
tilation, then more air must be sent to the room and the
temperature dropped correspondingly to avoid overheating
the room. Let Q' = total volume of air per hour, including
extra air for ventilation, measured at the register, then
55 H
t = 70 + (17)
0'
Rule. — Whe7i it is necessary for ventilation purposes to circu-
late more air than that calculated from the heat loss formula, then
the temperature at the register ivill be found by addi7ig to seventy
degrees the amount found by multiplying the heat loss by fifty-five
and dividing by the cubic feet of ventilating air.
Application. — Suppose it were necessary to send 18000
cubic feet of fresh air to this sitting room per hour to ac-
commodate ten people, the temiperature of the air at the
register should be
55 X 14000
« = 70 -I = 113°.
18000
39. Net Heat Registers: — The velocity of the air r,
as it leaves the heat register, varies from 3 to 4 feet per
second according to different designers. The first figure
is objected to by some because it gives too large register
areas; while the latter value is claimed to be great enough
that the occupants of the room will notice the movement
of the air. Practice no doubt tends to the higher velocity.
Most heat registers in residences are placed at the floor
line. If, however, they be placed above the heads of the
occupants of the room (see Art. 102), higher velocities than
the ones named ean be used. The general formula for net
registers is
H X 66 X 144
2^. H. R. = (18)
(t — t') X »• X 3600
Rule. — To find the square itichcs of net heat register, muUiphi
the heat loss calculated by formula by two and two-tenths and di-
vide by the product of the velocity in feet per second times the
difference in temperature between the register and the room air.
FURNACE HEATING 57
Assuming a mean velocity of 3.5 feet per second, and
60 degrees drop in teni'perature from the register to the
room, then the square inches of net register for any room
are found by the formula:
fl-X 55 X 144
N. H. R. = = .01 H (19)
60 X 3.5 X 3600
40. Net Vent Registers: — Vent registers should be put
In with any furnace plant, although this is not always done.
In order that any room may be heated properly, it is abso-
lutely necessary that the cold air in the room be allowed
to escape to give room for the heated air to come in. This
in some cases is done by venting through doors, windows
or transoms. A tightly closed room cannot be properly
heated by a furnace.
If all the air were to pass out the vent register at the
same velocity as it entered through the heat register, the
area of the vent register would be to the area of the heat
register as the ratio of the absolute temperatures of the
leaving and entering air; that is, the area of the vent
register = .9 of the area of the heat register. As a matter
of fact, since some of the air leaves* the room through other
openings, the vent register need not be so large. Practice
has decided this area to be about
N. V. R. = .008 H = .8 N. H. B. (20)
41. Gross Register Area: — The nominal size, or catalog
size, of the register is usually stated as the two dimensions
of the rectangular opening into which it fits, and varies
from 1.5 to 2 times the net area. The larger value Is prob-
ably the safer to follow unless the exact value be known
for any special make of register. Floor registers have
heavier bars and consequently for the same net area have
somewihat larger gross area.
G. R. = (1.5 to 2) times the net register (21)
Round registers may be had if desired. Register sizes may
be found in Tables 17 and 19, Appendix.
42. Heat Staclcs; — To get the proper sizes of the stacks
In any heating system is a very important part of the de-
sign of that system. By some designers the cross sectional
area is taken roughly as a certain ratio to that of the net
58 HEATING AND VENTILATION
register. This has been quoted anywhere from 50 to 90
per cent. Such wide variations between extremes of air
velocity should certainly require careful application. Prof.
Carpenter in H. and "V. B. Arts. 54 and 141, suggests 4, 5
and 6 feet per second respectively, as the air velocities for
the first, second and third floors. Mr. J. P. Bird, in the
"Metal Worker" of Dec. 16, 1905, uses 280, 400 and 500 feet
per minute, which is approximately 4.5, 6.5 and 8 feet per
second under like conditions. The formula for cross sec-
tional area of the heat stack, from formula 19, then becomes,
If the velocities are 4, 5.5 and 7 feet per second.
H X 55 X 144 r. 0091 Hist floor]
B. S. = = -{ . 0066 H 2nd floor ^ (22)
60 X (4, 5.5 or 7) X 3600 I .0052 H 3rd floorj
Rule. — See rule under net heat registers with chayiged value
for velocity.
The air velocity in the stack Is based upon the formula
V = V2gh, where h = (effective height of stack) X (f — t') -r
(460 + t'); V is in feet per second; t is the temperature of
the stack air and f is the temperature of the room air.
The calculated results from this formula are much higher
than those obtained in practice because of the shape of
cross sections of the stack, the friction of its sides and the
abrupt turns in It.
From the basis of the net register (figured at 3.5 feet
per second) the two quotations by Carpenter a..d Bird give
heat stack areas as follows: first fioor, 80 to 88 per
cent.; second floor, 55 to 70 per cent.; and third floor, 44 to
60 per cent. Good sized stacks are always advisable (see
Art. 55), but because of the limited space between the stud-
ding it becomes necessary at times to put in a stack that
Is too small or to increase the thickness of the wall, a thing
which the architect Is occasionally unwilling to do. From
the above figures, checked by existing plants that are
working satisfactorily, the following approximate figures,
reduced to the basis of the net heat register area, will no
doubt give good results.
r.8 times the net heat register. 1st floor -^
H. B. =1 .66 times the net heat register. 2nd floor y (23)
L.5 times the net heat register. 3rd floorj
43. Vent Stacks:— F. 8.= .S H. 8. (24)
44. Leader Plpeat — Since all the air that passes through
the stacks must pass througli the leader pipes. It seems
FURNACE HEATING 59
reasonable to assume that the areas of the two would be
equal. It must be remembered, however, that the stacks,
because of their vertical position, offer less resistance in
friction, while on the other hand the leader pipes, being:
nearly horizontal and having more crooks and turns in
them, will have considerable friction and will consequently
retard the air to a greater degree. There will also be some
loss of temperature in the air as it passes through the
leader pipes, consequently the volume of air entering the
leader from the furnace will be greater than that goinsr
up the stack.
It would be well, from the above reasons, to make the
area of the leader pipes
L. P. = (1.1 to 1.2) times the stack area, (25)
the exact figures to depend upon the length and inclination
of the leader and the selection of the diameter of the pipe.
45. Fresh Air Duct: — The area of the fresh air duct is
determined largely by experience as in the case of the vent
register. It is generally taken
F. A. D.= .8 times the total area of the leaders. (28)
Assume the average velocity of the air in the leaders to be
6 feet per second and the area of the fresh air duct to be
as shown above, then, if the air in each were of the same
temperature, the velocity in the fresh air duct would be
6-4- .8 = 7.5 feet per second; but since the temperatures
are different the velocities will be in proportion to the ab-
solute temperatures. Hence it is, at degrees, .78 X 7.5 "=
5.8; at 25 degrees, .82 X 7.5 = 6.2; and at 50 degrees, .88
X 7.5 = 6.6 feet per second. It is seen by this, that al-
though the area of the fresh air duct is contracted to 80
per cent, of that of the leaders, the velocity is in all
cases below that of the leaders. It is always well to have
a fresh air duct that is large in cross sectional area and
free from obstructions and sharp turns.
46. Grate Area: — The grate area of a furnace is esti-
mated from the total heat lost from the building, figured
on a basis of a certain degree of ventilation. In obtaining
the grate area it is necessary to assume the quality of the
coal, the efllciency of the furnace and the pounds of coal
burned per hour per square foot of grate. The quality of
60 HEATING AND VENTILATION
coal selected would be between 12000 and 14000 B. t. u. per
pound as shown in Table 14, Appendix. The efficiency of
the average furnace is about 60 per cent., and the coal
burned per square foot of grate per hour ranges from 3 to
7 pounds. Concerning the last point there may be a wide
difference of opinion. Higher temperatures in the combus-
tion chamber are conducive to economy, because of the
radiant heat of the fire; hence, to reduce the size
of the fire pot, and fire small amounts of coal with
greater frequency would seem to be the ideal way. On
the other hand, with high temperatures in the combustion
chamber, the loss up the chimney is increased. Probably
the one factor which is most effective in settling this point
is the inconvenience of frequent firing. Furnaces are
charged from two to four times each twenty-four hours.
This requires a good sized fire pot and a possibility of
banking the fires. To allow 5 pounds per hour is probably
as good an average as can be made for most coals in fur-
nace work.
Let E' = total heat loss from the building including
ventilation loss; E ^ efficiency of the furnace; f = value of
coal in B. t. u. per pound; and p = pounds of coal burned
per square foot of grate per hour; then the formula for the
square inches of grate area is
H' X 144
O. A. = (27)
E X f X p
Rule. — To find the square inches of prate area for any furnace,
multiply the total heat loss from the building per hour by one
hundred and forty-four and divide by the quantity foxind by multi-
plying the total pounds of coal burned per hour by the heat value of
the coal and the efficiency of the furnace.
Application. — In the typical illustration, the total heat loss
on a zero day by formula is, say, 100000 B. t. u. per hour.
This will require 90909 cubic feet of air as a heat carrier.
Assuming as a maximum that 10 people will be in the
house and that they will need 18000 cubic feet of fresh air
per hour for ventilation, this air will carry away approx-
imately 22900 B. t. u. per hour, making a total heat loss
from the building of 122900 B. t. u. per hour. Now, if the
furnace Is 60 per cent, efficient and burns 5 pounds of
14000 B. t. u. coal per hour per square foot of grate, we
will have
122900 X 144
0. A. = ^ 421 square Inches = 23.2 inches
.60 X 14000 X 5
FURNACE HEATING 61
diameter. With coal at 13000 B. t. u. per pound, the grate
would be 454 square Inches or 24 inches diameter. In either
case a 24 inch grate would be selected. With the assump-
tions as made above, the formula becomes G. A. = .0035 H'
for the better grade of coal, and G. A. = .0037 H' for the
poorer grade, from which the following approximate form-
ula may be taken:
G. A. square Inches = .0036 H' (28)
47. Heating: Surface: — The amount of heating surface
to be required In any furnace is rather an indefinite quantity.
Manufacturers differ upon this point. Some standard may
soon be looked for but at present only rough approximations
can be stated. One of the chief difficulties is in determin-
ng what Is, or what is not, heating surface. Some quota-
tions no doubt include some surface in the furnace that is
very inefficient. In estimating, only prime heating surface
should be considered, i. e., such plates or materials having
direct contact with the heated flue gases on one side and
the warm air current on the other. If these plates trans-
mit K, B. t. u. per square foot per degree difference of tem-
perature, tx, per hour; if, also, one square foot of grate
gives to the building £7 X / X p B. t. u. per hour, there will
be the following ratio between the heating surface and
grate surface:
B. 8. E f p
G. S. Etz
(29)
Application. — Let the value K tz be 2500, as suggested by
W. G. Snow, Trans. A. S. H. & V. E., 1906, page 133, and
with the same notations as in Art. 46 obtain
B. 8. .6 X 14000 X 5
=17
G. 8. 2500
In practice this ratio varies anywhere between 12 and 30.
In the investigations being made by the Federal Fur-
nace League their furnaces show an average of 1% square
feet of direct heating surface and 1 square foot of indirect
heating surface per pound of coal burned in the furnaces
per hour, making a total of 2% square feet of heating sur-
face per pound of coal burned per hour. The average size
of the furnaces submitted for tests, and probably the aver-
age size of furnaces used in actual practice, have a top fire-
62 HEATING AND VENTILATION
pot diameter of 24 inches and a bottom fire-pot diameter of
21 inches, making an average flre-pot diameter of 22 ^^ inches
and an average cross-sectional area of 2.83 square feet.
The average depth of pot in this size of furnace is about
13% inches, and for the purpose of rating under the Fed-
eral System would burn 7.2 pounds of coal per hour per
square foot of average fire-pot cross-section, making the
ratio per square foot of grate surface about 8^ pounds of
coal per hour. This gives a ratio of heating surface to
grate surface of approximately 20 to 1.
48. Application of the Above Formulas to a Ten Room
Residence: — In every design the calculations should be made
very complete and the results tabulated for easy reference
and as a means of comparison. Such a tabulation is ahown
in Table IX, giving all the calculated quantities necessary in"
the installation of the furnace system illustrated in Figs.
14, 15 and 16. The value of so condensing the Work will be
readily apparent. The tabulation of the values used
for the various terms of the formula facilitates checking
and the detection of errors. Plans should be carefully
drawn to scale and accompanied by a sectional elevation.
The scale should be as large as can conveniently be made.
The location of the building with reference to the points
of the compass should always be given, as well as the
heights of ceilings and the principal dimensions of each
room. There will be a wide variety of practica in making
allowance for exposure, floors, ceilings, closets and small
rooms not considered of sufficient importance to have Inde-
pendent heat. The personal element enters into this part of
the work very largely. Such points as these are left to
the discretion of the designer who, after having had con-
siderable experience Is able to Judge each case very closely.
FURNACE HEATING
6S
TABLE IX.
Formula. H = (G + .25 W + .02 nC) 70
,.H
Fi
fl
o
®
S
u
0)
beg
boo
4"
^
p
43
p
?,&
0^
43
P<0j
i-
So
S3
i''
^
-»;?
.i-(
7^
+3
\A
si
43
XI
d
ti
02
M
OQ
P3
O
o
Q
O
P4
o
.25 TT^
.02 n C
n
H
Q
Area of Net Heat Register
Heat Reg ster Size
Area of Heat Staclc..
Area of Leader
Area of Net Vent Register
Vent Register Size...
rea of Vent Stack...
38
85
78
2
14000
12727
140
14x16
100
112
12x14
67
28
28
84
2
10800
108
12x14
77
86
10x12
52
42
28
29
42
38
28
28
14
52
65
73
45
60
26
30
17
78
55
104
85
36
31
22
26
2
2
3
1
1
1
1
2
18250
11900
14000
9400
9850
6600
5600
4400
12045
10818
12727
8544
8954
6000
5091
4000
132
119
140
94
98
66
56
44
14x16
12x14
14x16
12x12
12x12
9x12
8x10
8x10
61
67
64
70
43
47
36
40
28
81
94
85
100
106
95
112
75
78
53
45
85
12x14
12x12
12x14
10x12
10x12
8x10
8x10
8x8
64
60
67
45
48
32
27
22
315
481
99800
711
Remarks.
u
O
o
< <
+3
Q, ft
5*
p.
o
I— I
o
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Diameter of grate allowing ventilation for ten people =
24 Inches. Cold air duct = 569 square inches = 18 X 32 inches.
In selecting the various stacks and leaders it would be
well to standardize as much as possible and avoid the extra
expense of installing so many sizes. This can be done if
the net area is not sacrificed.
^
64
HEATING AND VENTILATION
II
rtOTLnCA^Ttp.
f
If
"°^
If
15' 9i" Ljii L 9 _ 9^-.
— ~- 3 2- g-
4 6' •
FOUNDATION PLAN.
Ceiling 6'.
Fig. 14.
FURNACL] HEATING
65
W*a-
FIRST FLOOR PLAN.
Ceiling 10'.
Fig. 15
56
HEATING AND VENTILATION
SECOND FLXDOR PLAN.
Ceiling 9'.
Fig. 16.
CHAPTER V.
FURNACE HEATING AND VENTILATING.
SUGGESTIONS ON THE SELECTION AND INSTALLATION OF
FURNACE HEATING PARTS.
40. Selection of the Furnace: — In selecting a furnace
for residence use or other heating- service, special attention
should be paid to the following points: easy movement of
the air, arrangement and amount of heating surface, shape
and size of the fire-'pot, method of feeding fuel to the fire
and type and size of the grate. The furnace gases and the
air to be heated should not be allowed to pass through the
furnace in too large a unit volume or at too high a velocity.
The gases should be broken up in relatively small volumes,
thus giving an opportunity for a large heating surface.
Concerning the gas passages themselves, it may be said
that a number of small, thin passages will be found more
efficient than one large passage of equal total area. This
is plainly shown In a similar case by comparing the effl-
ciency of the water-tube or tubular boiler with that of
the old fashioned flue boiler; i. e., a large heating surface
is of prime importance. Again, it is desirable that the
total flue area within the furnace should be great enough
to allow the passage of large volumes of air at low velocities,
rather than small volumes at high velocities. This permits
of less forcing of the fire and consequently lowers the tem-
perature of the heating surface. The latter point will be
found valuable when it is remembered that metal at high
temperatures transmits through its body a greater amount
of impure gases from the coal than when at low tempera-
tures. Concerning velocities, it may be said that on account
of the low rate of transmission of heat to or from the
gases, long flue passages are necessary, so that gases mov-
ing at a normal rate will have time to give off or to take
up a maximum amount of heat before leaving the furnace.
Air is heated chiefly by actual contact with heated sur-
faces and not much by radiation. Consequently, the ef-
ficiency of a furnace is increased when it is designed so
that the gases and air in their movement impinge perpen-
68
HEATING AND VENTILATION
dlcularly upon the heated surfaces at certain places. This
point sliould not be so exaggerated that there would be
serious interference with the draft. The efldciency is also
increased if the general movement of the two currents be
in opposite directions.
Furnaces for residences are usually of the portable type.
Fig. 17, the same being enclosed in an outer shell composed
of two metal casings having a dead air space or an asbes-
tos Insulation between them. Some of the larg^er sized
Fig. 17.
plants, however, have the furnace enclosed in a permanent
casement of brick work, as in Fig. 18. Each of the two
types of furnaces give good results. The points usually
governing the selection between portable and permanent
settings are price and available floor space.
The cylindrical fire-pot is probably better than a con-
ical or spherical one, there being less danger of the fire
clogging and becoming dirty. A lined fire-pot i-s better
than an unlined one, because a hotter fire can be maintained
in it with less detriment to the furnace. There is of course
a loss of heating surface in the lined pot, and in some forms
FURNACE HEATING
69
of furnaces the fire-pot is unlined to obtain this increased
heating surface. It seems reasonable to assume, however,
that the lined pot is longer lived and contaminates the air
supply less.
Fig. 18.
Fig. 19.
70
HEATING AND VENTILATION
Some topm of shaking or dumping grate should be se-
lected, as a stationary grate is far from satisfactory. Care
should be exercised also, in the selection of the movable
grate, as some forms not only stir up the fire but permit
much of it to fall through to waste when being operated.
The fuel is fed to the flre-pot from the door above the
fire. This is called a top-feed furnace. In some forms, how-
ever, the fuel is fed up through the grate. This is called
the under-feed furnace, Fig. 19, and is rapidly gaining in
favor. The latter type requires a rotary ring grate with
the fuel entering up through its center.
The size of the furnace may be obtained from the estimated
heating capacity in cubic feet of room space as given in the
sample Table 18, Appendix. Another and perhaps a bet-
ter way, and one that serves as a good check on the above,'
Is to select a furnace from the calculated grate area. See Art.
46. Having selected the furnace by the grate area, check
this with the table for the estimated heating capacity
and the heating surface to see if they agree.
What is known as a combination heater is shown In
Fig. 20. It is used for heating part of the rooms of a resi-
dence by warm air, as in
regular furnace work, and
the remainder of the rooms
by hot water. In this
manner, rooms to be ven-
tilated as well as heated
may be connected by the
proper stacks and leaders
to the warm air deliveries
of such a combination
heater, while rooms requlr-
ing less ventilation or heat
only may have radiators
Installed and connected to
the flow and return pipes
shown in the figure. Also,
because of the difficulty
in heating certain exposed
rooms with warm air, these
rooms may be supplied by
i^'iS- 20. ^j^g positive heat of the
more reliable water circulation.
FURNACE HEATING 71
50. Location of Furnace; — Where other things do
not interfere, a furnace should be set as near the center
of the house plan as possible. Where this is not wise or
possible, preference should be given to the colder sides, say
the north or west. In any case, it is advisable to have the
leader pipes as near the same length as can be made. The
length of the smoke pipe should be as short as possible,
but it will. be better to have a moderately long smoke pipe
and obtain a more uniform length of leader pipes than to
have a short smoke pipe and leaders of widely different
lengths.
The furnace should be set low enough to get a good
upward slope to the leaders from the furnace to their re-
spective stacks. This should be not less than one inch per foot
of length and more if possible. These leader pipes should be
dampered near the furnace.
The location of the furnace will call forth the best
judgment of the designer, since the right or wrong decis-
ion here can make or mar the whole system more com-
pletely than in any other manner.
51. Foundation: — All furnaces should have directions
from the manufacturer to govern the setting. Each type of
furnace requires a special setting and the maker should
best be able to supply this desired information concerning
it. Such information may be safely fallowed. In any case
the furnace should be mounted on a level brick or concrete
foundation specially prepared and well finished with cement
mortar on the inside, since this interior is in contact with
the fresh air supply.
52. Fresh Air Duct: — This is best constructed of hard
burned brick, vitrified tile or concrete, laid in four inch
walls with cement mortar and plastered inside with ce-
ment plaster, all to be air tight. The top should be covered
with flag stones with tight joints. The riser from this,
leading to the outside of the building, may be of wood, tile
or galvanized iron, and the fresh air entrance should be
vertically screened. The whole should be with tight joints
and so constructed as to be free from surface drainage,
dirt, rats and other vermin. This duct may be made of
metal or boards as substitutes for the brick, tile or concrete.
Board construction is not so satisfactory, although it is the
cheapest, and whenever used should be carefully constructed.
7>
HEATING AND VENTILATION
In addition to the opening for the adm/ission of the
fresh air duct, another opening may be made under the
furnace for the purpose of admitting the duct which carries
the recirculated air from the rooms to the furnace. Both
of these ducts should liave dampers that may be opened or
•I 'I 11 '1
l^||UJ|,^l|
EISH AIR RETU
FRESH AIR
TURN
FRONT
FRONT
FRONT
Fig. 21.
closed. See Figs. 13 and 21. Both ducts should also be provid-
ed with doors that can be opened temporarily to the cellar
air. Sometimes it is desirable to have two or more fresh
air ducts leading from the different sides of the house to the
furnace so as to get the benefit of
any change in air pressure on the
outside of the building.
Proper arrangements may be
made for pans of clear water in the
air duct near the furnace to give
moisture to the air current, although
only a small amount of moisture
will be taken up at this point. In
most cases where moistening pans
are used, they are installed in con-
nection with the furnace itself. A
good way to moisten the air is to
have moistening pans built in just
behind the register face, Fig. 22.
These pans are shallow and should
not be permitted to seriously inter-
fere with the amount of air enter-
ing through the register.
53. Reolrculatlns: Duct: — A duct should be provided
from some point within the building, through the cellar
and entering into the bottom of the furnace. This is to car-
FURNACE HEATING
73
ry the warm air from the room back to the furnace to be
reheated for use again wiithin the building. In many cases
tin or galvanized iron is used for the material for the
recirculating pipe. Where this enters the furnace it
should be planned with sufficient turn so that the
air would be projected through the furnace, thus
placing a hindrance to the fresh cold air from following
back through this pipe to the rooms. The exact location
of the same will depend, of course, on the location of the
register instaiaed for this purpose. The construction of the
duct may agree with the similar construction of the fresh
air duct.
54. Leader Pipes: — All leader pipes should be round
and free from unnecessary turns. They should be made
Fig. 23.
74
HEATING AND VENTILATION
from heavy galvanized iron or tin and should be laid to an
upward pitch of not less than one inch per foot of length,
and more if it can possibly be given. The connections with
the furnace should be straight, but if a turn is necessary,
provide long radius elbows. All connections to risers or
stacks should be made through long radius elbows. Rect-
angular shaped l>oots having attached collars are sometimes
used, but these are not so satisfactory because of the im-
pingement of the air against the flat side of the stack; also
because of tlie danger of the leader entering too far into
the stack and thus sliutting off the draft. Leaders sliould
connect to the first floor registers by long radius el-
bows. Leader pipes should have as few joints as possible
and these should be made firm and air tight. Fig. 23 shows
different methods of connecting between leaders and stacks",
also between leaders and registers.
The outside of all leader pipes should be covered to
avoid heat loss and to provide additional safety to the plant.
The covering is usually one or more thicknesses of asbes-
tos paper or mineral wool.
55. Stacks or Risers: — The vertical air pipes leading to
the registers are called stacks or risers. They are rect-
angular or oblong in section and are usu-
ally fitted within the wall. See Fig. 24.
The size of the studding and the distances
they are set, center to center, limit the
effective area of the stack. All stacks
should be insulated to protect the wood-
work. This is done by making the stack
small enough to clear the woodwork by
at least one-quarter inch and then wrap-
ping it with some non-conducting material
such as asbestos paper held in place by
wire.
Another way, and one which is prob-
ably more satisfactory, is to have pat-
ented double walled stacks having an air
space between the walls all around. The
outside wall is usually provided with vent
holes which allow the circulation of air
between the walls, thus protecting any
one part frqjjn becoming overheated. All
Fig. 24. stacks sliouli, be made With tight Joints
FURNACE HEATING 75
and should have ears or flaps for fastening to the studding.
Patented sacks are made in standard sizes and of various
leng-ths. The sizes ordinarily found in practice are about
as given in Table 19, Appendix.
A stack is sometimes run up in a corner or in some
recess in the wall of a room where its appearance, after
being finished in color to compare with that of the room,
would not be unsightly. This is necessary in any case
where the stack is installed after the building is finished.
This method is desired by some because of its additional
safety and because more stack area may be obtained than
Is possible when placed within a thin wall.
All stacks should be located in partition walls looking
toward the outside or cold side of the room. This protects
the air current from excessive loss of heat, as would be the
case in the outside walls. It also provides a more uniforfia
distribution of air.
The area of the stack best adapted to any given room
Is another point in furnace work which brings out a wide
diversity of practice. Results from different installations
show variations as great as 50 per cent. This is not so
noticeable in the first floor roomo as it is in those of the
second floor. In a great many cases the architect specifies
light partition walls between large upper rooms, say, four
inch studding set sixteen inch centers, between twelve foot
by fifteen foot rooms, heavily exposed. From theoretical
calculation of heat losses, these rooms require larger stacks
than can be placed between studding as stated; however, it
is very common to find such rooms provided for in this way.
One possible excuse for it may be the fact that the room is
designed for a chamber and not for a living room. Any
sacrifice in heating capacity in any room, even though it be
used as a sleeping room only, should be done at the sug-
gestion of the purchaser and not at the suggestion of the
architect or engineer. Every room should be provided with
facilities for heat as though it were to be used as a living
room in the coldest weather, then there would be fewer
complaints of defective heating plants and less migrating
from one side of the house to the other on cold days.
This lack of heating capacity for any room is some-
times overcome by providing two stacks and registers in-
76
HEATING AND VENTILATION
stead of one. This plan is very satisfactory because one
of the registers may be shut off in moderate weather; how-
ever, it requires an additional expense wliicli is scarcely
Justified. A possible improvement would be for the archi-
tect to anticipate such conditions and provide suitable
partition walls so that ample stack area could be put in.
The ideal conditions will be reached when the architect act-
ually provides air shafts of sufficient size to accommodate
either a round or a nearly square stack. When this time
comes a great many of the furnace heating difficulties will
have been solved.
A double stack supplying air to two rooms is some-
times used, having a partition separating the air currents
near the upper end. This practice is questionable because
of the liability of the pressure of air in the room on the
cold side of the house forcing the heated air to the other
room. A better method is to have a stack for each room
to be heated.
56. Vent Stacks: — Vent stacks should be placed on the
inner or partition walls and should lead to the attic. They
may there be gathered together in one duct leading to a
vent through the roof if desired.
57. Air Circulation AVithin the Room: — The location of
the heat register, relative to the vent register, will deter-
^^^.i^M^^^.^^^^^^^^^^^
Ill',
^^•,^^^,^:,,,^ ^/>i2^^k ^
'l////w/
i"'''V''':'.. '.'.Ml ''';'"'•
Fig. 25.
FURNACE HEATING 77
mine to a large degree the circulation of the air within the
room. Fig. 25, a, b, c and d, shows clearly the effect of the
different locations. The best plan, from the standpoint of
heating, is to enter the air at a point above the heads of the
occupants and withdraw it from the floor line, at or near the
same side from which the air enters. This gives a more uni-
form distribution as shown by the last figure. It is doubtful,
however, if this method will give the best ventilation in
crowded rooms where the foul air naturally collects at the
top of the room. Furnace heating is not so well cared for
in this regard as are the other forms of indirect heating, the
air being admitted at the floor line and required to find its
own way out.
58. Fan-Furnace Heating System: — In large furnace
installations where the air is carried in long ducts that are
nearly, if not quite, horizontal, and where a continuous sup-
ply of air is a necessity in all parts of the building, a com-
bination fan and furnace system may be installed. These
are frequently found in hospitals, schools and churches. Such
a system may be properly designated a mechanical warm
air system. In comparison with other mechanical systems,
however, it is simpler and cheaper. The arrangement may
be illustrated by Fig. 96 with the tempering coils omitted
and the furnace substituted for the heating coils. The fan
should always be between the air inlet and the furnace so as
to keep a slight pressure above atmosphere on the air side
and thus reduce the leakage of the fuel gas through the
joints of the furnace. By this arrangement there is less
volume of air to be handled by the fan and a smaller sized
fan may be used.
Fan-furnace systems may be set in multiple if desired, i.
e., one fan operating in connection with two or more fur-
naces.
Fig. 26 represents a two-furnace plant showing the
fan and the two furnaces. The air is drawn into the fresh
air room through a grate in the outside wall and is forced
through the fan to the furniaces where it divides and passes
up through each furnace to the warm air ducts. Part of
the fresh air from the fan is by-passed over the top of the
furnaces and is admitted to the warm air ducts through
mixing dampers. These dampers control the amount of
hot and cold air for any desired temperature of the mix-
78
HEATING AND VENTILATION
Fig. 26.
ture. Temperature control may be applied, also air washing
and humidifying apparatus can be installed and operated
with satisfaction. Paddle wheel fans are preferred, al-
though the disk wheel may be used where the pipes are
large and where the air must be carried but short distances.
For fan types see Chapter X.
59. Sugrgrestions for Operating: Furnaces: — Furnaces are
designated hard coal and soft coal, depending upon the type and
the construction of the grate, hence the grade of coal best
adapted to the furnace should be used. The size of the open-
ings in the grate should determine the size of the coal used.
Keep the fire-pot well filled with coal and have It evenly
distributed over the grate.
FURNACE HEATING 79
Keep the fire clean. Clinkers should be removed from
the fire once or twice daily. It is not necessary to stir the
fire so completely as to waste the coal through the grate.
When replenishing a poor fire do not shake the fire, but
put some coal on and open the drafts. After the coal is well
ignited cleai. the fire.
The ash pit should be frequently cleaned, because an
accumulation of ashes below the grate soon warps the grate
and burns it out.
Keep all the dampors set and properly working.
Have a damper in the smoke pipe and keep i't open only
so far as is necessary to create a draft.
Keep the water pans full uf water.
Clean the furnace and smoke pipe thoroughly in all parts
at least once each year.
Keep the fresh air duct free from rubbish and impurities.
Allow plenty of pure fresh air to enter the furnace. -In
cold weather part of this supply may be cut off.
Have the basement well ventilated by means of outside
wall ventilators, or by special ducts leading to the attic.
Never permit the basement air to be circulated to the diving
rooms.
To bank the fires for the night, clean the fire, push the
coals near the rear of the grate, cover with fresh fuel to
the necessary depth (this will be found by experience), set the
drafts so they are nearly closed and open the fire doors
slightly.
60. Determination of the Best Outside Temperature to
Use in Design and the Costs Involved in Heating by Fur-
naces:— As a basis for the work of the heating and venti-
lating engineer it is necessary that he be well acquainted
with the temperature conditions in the locality where his
services are employed. He should compile a chart showing
extreme and average temperatures covering a period of
3'ears and with this chart a fairly safe estimate may be
made upon the costs involved dn operating any heating
and ventilating system during any part of the average
season or throughout the entire heating season. Any costs
of operation arrived at are only illustrative of method and
probability, however. All one can say is that if the tem-
perature in any one season averages what is shown by the
average curve for the period of years investigated, then
the cost in operating the system may be easily shown by
80 HEATING AND VENTILATION
calculation. Costs in heating are relative figures only and
cannot be predetermined exactly except under test condi-
tions. The heating engineer should also know the mini-
mum outside temperatures covering a period of years in
that locality so as to determine upon an outside tfentipera-
ture for his design work. Any design is somewhat of a
compromise between average conditions and the minimum
or extreme conditions, approaching the extreme rather than
the average. Patrons are willing that the heating systems
be designed so as to give normal temperatures in the rooms
on all but a few of the coldest days. These minimum con-
ditions usually have a duration of from two to three days
and it would not be considered good engineering from an
economic standpoint to design the system large enough to
heat to normal inside temperature pn the coldest day ex-
perienced in a period of years. The plant would be too
large and would require too much financial in-put. As an
illustration of the method of obtaining the outside tem-
perature to be used in design, also methods of determining
approximate costs for heating, see Fig. 27. This has been
worked up as an average for the temperatures of each of
the days respectively between September fifteenth and May
fifteenth, covering a period of thirty years, at Lincoln,
Nebraska. The minimum temperature curve includes the
outside temperatures for December 1911, and January 1912,
which may be regarded as a period of unusual severity.
Referring to the chart it will be seen that a cold period of
one month was experienced from December nineteenth to
January twenty-first, reaching its minimum temperature of
— 26° on January twelfth. If this curve were assumed to
be the most severe weather that would be found in this
locality, then by a study of conditions one may easily de-
termine a good value for outside temperature in design.
There were twenty days when the temperature was below
zero, twelve days below — 5°, six days below — 10°, four
days below — 15°, two days below — 20°, and a part of one
day below — 25°. Each of the extreme and sudden drops
were such as to last from two to three days and were only
experienced in two or three instances. It is very evident
that a system designed for 0° outside would fall far short
of tfie requirement even when put under heavy stress. On
the other hand one desiigned for — 25° outside would actu-
ally come up to its capacity for only a part of one day out
FURNACE HEATING
;i
of the 240 Jieating days. One designed for — 10° would
fulfill condition.s without forcing- excepting at two or three
periods of very short duration, at which times the system
could be forced sufficiently without detriment. The per-
TtMPCTAnjfiE IN DECREES AND HEAT uOSS IN THOUSAND BTU
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sonal equation enters into the calculation of the heat loss
somewhat and there will be some difference of opinion con-
cerning which to use, — 10° or — 15°. Probably the latter
would be a safer value. All that is .lecessary is to plan
82 HEATING AND VENTILATION
for ample service at all but one or two of the cold periods
of short duration and the system wdll be considered very
satisfactory from the standpoint of size and capacity. Any
additional amount put in would be an investment of money,
which is scarcely justified for the small percentage of time
that this additional capacity would be called for.
After the mlnlm'um outside temperature has been de-
cided and the plant is designed, one would like to know
the probable expense in handling such a plant throughout
the heating season. Assume an inside temperature through-
out the building of 70°. Comlbine the two half months, Sep-
tember and May, into one month, and take the average of
these average temperatures for the days of each month,
thus giving the drop in temperature between the inside
and the outside of the building. The heat loss from the
building is then proportional to these drops in tempera-
ture. In this case the dilTerences are as follows:
iSeptember + May 7" below 70*
October 17°
November 32.3°
December 44°
January 48.7°
February 45° " "
March 34°
April 19.5°
Taking the sum of all these differences as the total,
100%, and dividing each individual difference by the total,
we have the percentages of loss for the various months
as follows:
September + May 2.84% of total yearly loss
October 6.9 %
Novem>ber 13.1 %
December 17.8 % "
January 19.7 % "
February 18.2 % "
March 13.7 % "
April 7.9 % "
These percentages of loss indicate what may be ex-
pected in the expense for coal at various times of the heat-
ing year, based upon the average temperatures existing In
the past thirty years. From this the lieat loss has been
^
FURNACE HEATING 83
calculated for the sample design stated under Furnace
Keating'. The results are shown upon the chart in tons
of coal per year, assuming that the entire house is heated
to 70° upon the inside for each hour between September
fifteenth and May fifteenth. The lowest curve as that for
direct radiation only. The next superimposed curve as-
sumes fresh air for ten people. The third curve assumes
one-half of the required air to be recirculated and the upper
curve assumes all the air to be fresh, air.
Jk
8-: HEATING AND VENTILATION
REFERENCES.
ReferenecH on Furnace Heatin^r.
Technical Books.
Snow, Prin. of Heat., p. 27. Snow. Furnace Heat., p. 7. I. C. S.
Prin. of Heat, d Vent., p. 1237. Carpenter, llcat. tt Vent. Bldgn., p.
310. Hubbard, Power, Heat. & Tent., p. 423.
Technical Periodicals.
Engineering Review. Warm Air Furnace Heating, C. L. Hub-
bard, Nov. 1909, p. 42; Dec. 1909, p. 45; Jan. 1910, p. 66; Feb.
1910, p. 48; March 1910, p. 51; May 1910, p. 48; Aug. 1910, p.
29. Warm Air System of Heating and Ventilating. R. H.
Bradley, May 1910, p. 32. Mechanical Furnace Heating and
Ventilating, June 1910, p. 49. Heating and Vent. System
Installed in Public School, Fairview, N. J., July 1910, p. 47.
Combined System of Warm Air and Hot Water Heat, for a
Residence, Jan. 1909, p. 26. Warm Air Heating Installation
in a Brooklyn Residence, March 1909, p. 38. The Heating and
Tentilaiing Magazine. Advanced Methods of Warm Air Heat-
ing, A. O. Jones, Aug. 1904, p. 88. Air Pipes, Sizes Required
for Low Velocities, Oct. 1905, p. 7. Report of Committee
(A. S. H. V. E.) to Collect Data on Furnace Heating, Jan.
1906, p. 35. An Improved Application of Hot Air Heating,
A. O. Jones. July 1906. p. 31. The Official Federal Fur-
nace League Method of Testing Furnaces, W. F. Col-
bert. July 1910. Domestic Engineering. Sanitation in Hot
Air Heating, James C. Bayles, Vol. 25, No, 6, Sept.
25, 1903, p. 261. Trans. A. S. H. d "> E. Test of Hot Air Grav-
ity System. R. C. Carpenter, Vol. IX, p. 111. Heat Radiators
Using Air Instead of Water and Steam, Geo. Aylsworth, Vol.
IX, p. 259. Velocities in Pipes and Registers in a Warm Air
System, Vol. XII, p. 352. Relative Size Hot Air Pipes, Vol.
XIII. p. 270. Velocity of Air in Ducts, Vol. VII, p. 162. The
Metal Worker. Battery of Furnaces with Vent Ducts, Jan. 15,
1910, p. 85. Air Blast System. Jan. 15, 1910, p. 93. Origin
and Comparative Cost of Trunk Main Furnace System,
Aug. 6. 1910. p. 171. Example of Trunk Line Furnace Piping,
April 2, 1910, p. 463. Furnace System with Piping 50 ft. Long,
July 3, 1909, p. 45. Heat Unit in Furnace Heating. Aug. 8,
1908, p. 43. Data on a Notable School Heating Plant, Nov. 6,
1909, p. 37. Fan-Furnace Residence System. Oct. 3. 1908.
p. 43. Theoretical Construction in Designing Furnace Heat-
ing. Dec. 26. 1908, p. 33. School Fan Furnace Heating
Plant, Oct. 8. 1910. Combination Heating in Cold Terri-
tory, Sept. 29, 1911. Underwriters' Tests of Wall Stacks.
July 1, 1911. Design of Fan Blast Heating, H. C. Russell,
Jan. 21, 1911; Feb. 25. 1911.
CHAPTER VI,
HOT WATER AND STKA3I HEATING.
DESCRIPTION AND CLASSIFICATION OF THE SYSTEMS.
61. Hot W'ater and Steam Systems Compared to Fur-
nace Systems; — As compared to the warm air or furnace
plant, the hot water and the steam installations are more
complicated in the number of parts; they use a more cum-
bersome heat carrying medium, for which a return path to
the boiler must be provided; and have parts, in the form
of radiators, which occupy valuable room space. But the
steam and hot water plants have the advantage in that
their circulations, and hence their transference of heat,
are quite positive, and not affected by wind pressures, A
hot water or a steam system will carry heat just as readily
to the windward side of a house as it will to the leeward
side, a point which, with a furnace installation, .is known
to be quite impossible. Furnace heating, on the other hand,
has the advantage of inherent ventilation, while the hot
water and steam systems, as usually installed, provide no
ventilation except that due to air leakage.
62. The Parts of Hot Water and Steam Systems: — ^A hot
water or a steam system may be said to consist of three
principal parts: first, the boiler or heat generator; second,
the radiators or heat distributors; and third, the connecting
pipe-lines, which provide the circuit paths for the hot water
or the steam. In the hot water system it is essential that
the heat generator be located at the lowest point in the
circuit, for, as was explained in Art. 5, the only motive
force is that due to the convection of the water. In the
steam system this is not essential, as the pressure of the
steam forces it outward to the farthest points of the system.
The water of condensation may or may not be returned by
gravity to the boiler. Hence, with a steam system a radiator
may be placed below the boiler, if its condensation be trapped
or otherwise taken care of.
86
HEATING AND VENTILATION
C3. Definitions: — In speaking of the piping of heating
Installations, several terms, commonly used by heating en-
gineers, should be thoroughly understood. The large pipes
in the basement connected directly to the source of heat,
and serving as feeders or distributors of the heating me-
dium to the pipes running vertically in the building, are
known as mains. The flow mains are those carrying steam
Fig. 28.
Pig. 29.
or hot water from the source of heat towards the radiators,
and the return mains are those carrying water or
condensation from the radiators to the source of
heat. Those vertical pipes in a building to which
the radiators are directly connected are called risers,
w^hile the short horizontal pipes from risers to radi-
ators are usually termed riser arms. As there are flow
mains and return mains, so also, there are flow risers and
return risers. A radiator should have at least two tappings,
one below for the entry of the heating medium, and one
on the end section opposite, near the top for air discharge
as shown by the connected steam radiator of Fig. 28. It
noay have three, a flow tapping and a return tapping at the
bottom of the two end sections, and the third or air tapping
near the top of the end section at the return end as shown
by the connected hot water radiator of Fig. 29. A return
HOT WATER AND STEAM HEATING
87
main traversing the basement above the water line of the
boiler is designated as a dry return and carries both steam
and water of condensation; one in such position below the
water line as to be filled with water is designated a wet
return, and the returns of all two-pipe radiators connecting
with wet returns are said to be sealed.
64. Classification: — One classification of hot water and
steam systems is based upon the position and manner in
which the radiators are used. The system which is, per-
haps, most familiar is the one wherein radiators are placed
directly within the space to be heated. This heating is ac-
Fig. 30.
Fig. 31.
complished by direct radiation and by air convection cur-
rents through the radiators, no provision being made for a
change of air in the room. This is known as the direct
system, and, while it causes movements of the air in the
room, it produces no real ventilation. See Fig. 30.
Ivi the direct-indirect system, the radiator is also
placed within the space or room to be heated, but its lower
half is so encased and connected to the outside of the build-
88 HEATING AND VENTILATION
Ing- that fresh air is continually drawn up through the
radiator, is heated, and thrown out into the room as shown
by Fig-. 31, Thus is es-tablished a ventilating system more
or less effective.
In the purely indireci si/sfem. Fig. 32. the radiating sur-
face is erected somewhere remote from the rooms to be
heated, and ducts carry the heated air from the radiator
to the rooms either by natural convection, as in some in-
stallations, or by fan or blower pressure, as in others.
When all the radiation for an entire building is installed
Fig. 32.
together in one basement room, and each room of the build
iiig has carried to it, its share of heat by forced air througli
ducts from one large centralized fan or blower, the system
is called a Plenum System, and is given special consideration
in Chapters X to XII.
65. A second classification of steam and hot water sys-
tems is made according to the method of pipe connection
between the heat generator and the radiation. That known
as the one-pipe system, Fig. 33, is the simplest in construc-
tion and is preferred by many for the steam installations.
As the name indicates, its distinguishing feature is the
single pipe leading from the source of heat to the radiator,
the steam and the returning condensation both using this
path. In the risers and connections, the steam and ton-
densation flow in opposite directions, thus requiring larger
pipes than where a flow and a return are both provided.
In this system the condensation usually flows with the
steam in the main, and not against it, until it reaches such
a point that it may be dripped to a separate return
and then led to the boiler. In the so-called one-pipe
hot water system, radiators have two tappings and two
HOT WATEK AND STEAM HEATING
89
Fig. 33.
risers, but the flow riser is tapped out of the top of the
single basement main, while the return riser is tapped into
the bottom of that same main by either of the special fit-
tings shown in section in Fig. 34. The theory is that the
hot water from the boiler travels
along the top of the horizontal base-
ment main, while the cooler water from
the radiators travels along the bottom
of this same main. Hence the neces-
sity for tapping flow risers out of the
top and return risers into the bottom
of this main, thus avoiding a mixing
of the two streams. Where mains are
short and straight as in the smaller
Fig, 34. residence installations, this system
90
HEATING AND VENTILATION
seems to give satisfaction; but it is very evident that, wlicxc
basement mains are long and more complicated, a mixing
©f the two streams is unavoidable, thus rendering the sys-
tem unreliable.
The tvco-pipe system is used on both s.team and hot
water installations. For steam work it is probably no
better than the one-pipe system but for hot water work it
is much preferred. In this system two separate and dis-
tinct paths may be traced from any radiator to the source
of heat. In the basement are two mains, the flow and the
return, and the risers from these are always run in pairs,
the flow riser on one side of a tier of radiators, the return
riser on the other side. A two-pipe steam system must
have a sealed return. Typical two-pipe main and riser con-
nections are shown in Fig. 35.
Fig. 35.
Fig. 36.
66. A third system, known as the attic main, or Mills
system, has found much favor with heating engineers in
the installation of the larger steam plants although it could
be applied as well to the larger hot water plants. The
distinguishing feature, when applied to a steam system,
is the double main and single riser, so arranged that the
condensation and live steam flow in the same direction.
HOT WATER AND STEAM HEATING 91
This is accomplished by taking- the live steam directly to
the attic by one large main, which there branches, as need
be, to supply the various risers, only one riser being used
for each tier of radiators and the direction of flow of both
steam and condensation in risers being downward. Hence,
this system avoids the unsightliness of duplicate risers, as
in the two-pipe system, and avoids the disadvantage of the
one-pipe basement system, the last named having steam
and condensation flowing in opposite directions in the same
pipe. Fig. 36 shows two common methods of connecting
risers and radiators with this system.
67. Diagrrams for Steam and Hot Water Piping: Systems t
— iFigs. 37 to 43 inclusive show somie of the methods for
connecting up piping systems between the source of heat
and the radiators. At the radiators A, B, C and D are shown
different methods of connecting between the radiators and
mains. In every case the various forms of branches below
the floor and behind the radiators are for the purpose of
taking up the expansion. It will be noticed that the two-
pipe steam systems have sealed returns where they enter
the main return above the water line of the boiler.
In some steam systems where atmospheric pressure is
maintained, special valves with graduated control admit steam
to the upper part of the radiator. The returns enter into a
receiver near the boiler with a vapor and air relief to the
atmosphere through some form of condenser, having an out-
let pipe leading to an air shaft or to a chimney. The pres-
sure upon this return is maintained in such a case approx-
imately 14.7 pounds. The water type of radiator is used,
having the sections connected both top and bottom and with
this graduated control only that amount of radiation which
is necessary to heat the room on a given day is employed.
Such a system is economical, safe and can be operated in
connection with any kind of radiation. Pig. 43 is typical of
such systems.
92
HEATING AND VENTILATION
ONt PiPL STEAM SYSTEM -BASEMENT MAIN
FiS. 37.
TWO PIPE STEAM SYSTEM-BASEMENT MAIN
Fig. 38.
HOT WATER AND. STEAM HEATING
93
A
O
MILLS SYSTEM
&
0=s
STEAM- ATTIC MAIN
D
ORv RETURN
WET RETURN
^ y^ a
ORY RE Turn
:#---
WCT RETuRM
Fig. 39.
ONE PIPL ~5YSTLM-H0T WATER
Fisr. 40.
94
HEATING AND VENTILATION
TWO PIPL SYSTEM HOT WATER -BASEMENT MAIN
Fig. 41.
Fig. 42.
HOT WATER AND STEAM HEATING
95
VAPOR SYSTEM OF STEAM HEATINO
Fig. 4;
68. Accelerated Hot Water Heating Systems: — Improve-
ments have been devised for hot water heating whereby the
circulation of the water is increased above that obtained by
the open tank system. By increasing the velocity of the
water, pipe sizes may be reduced, resulting in an economy
in the cost of pipe and fittings. In addition to this, where
the temperature of the water is carried above that due to
atmospheric pressure, the radiation may theoretically be
reduced below that for the open tank system. How far
these economies may be pursued in designing is a question
which should be very carefully considered. In many cases
the amiount of radiation is kept the same and the chief dif-
ference merely thiat of pipe sizes. This article is descriptive
of several of the types of accelerated systems in use and is
not intended as a critical analysis of the merits of any one
as compared to the others.
Of all the principles employed for accelerating the cir-
culating water, four w'ill be mentioned. First, by increas-
ing the pressure of the open tank system thus raising the
temperature above 212 degrees. Second, by superheating a
part or all of the circulating water as it passes through the
heater and condensing the steam thus formed by mixing it
96
HEATING AND VENTILATION
with a portion of tlie cold circulating water of the return.
Third, by introducing steam or air into the main riser pipe
near the top of the system. Fourth, by mechanically oper-
ated pumps or motors.
Descriptive of the first principle. Fig. 44 shows a mer-
cury-seal tube connected between the upper point of the
^ main riser and the expansion tank. This is
designed to hold a pressure of about 10 pounds
gage, the water from the system filling the
casement and pressing down upon the top
of the mercury in the bowl. Increasing the
pressure in the system lowers the level of the
mercury in the bowl and forces the mercury
up the central tube A until the differential
pressure is neutralized by the static head of
the mercury. If the pressure becomes great
enough to drop the level of the mercury to
the tube entrance, water and steam will force
through the mercury to chamber D and from
thence through the expansion tank to the over-
flow. Any mercury forced out of the tube A
by the velocity of the water and steam, strikes
the deflecting plate C and drops back through
the annular opening B to the mercury bulb
below. As the pressure is reduced in the
system the mercury drops in tube A to the
level of that in the bulb and water from the
expansion tank passes down through the
mercury-seal into the heating system to replace any that
has been forced out to the expansion tank. This action is
autom.atic and is controlled entirely by the pressure within
the system. The only loss, if any. is that amount which
goes out the overflow. The above represents essentially
what is known as the Honeywell System of acceleration.
A modification of the above is used in the Cripps System.
In this the mercury-seal Is placed beyond the expansion
tank and puts the expansion tank under pressure.
The second principle is illustrated by Figs. 45 and 46.
Fig. 45, known as the Koerting System, has a series of
motor pipes leading from the upper part of the heater to a
mixer, where the steam is condensed before it reaches the
Fig. 44
HOT WATER AND STEAM HEATING
97
expansion tank by the water entering through the by-pass
from the return. The velocity of the steam and water
through the motor pipes and the partial vacuum caused by
the condensation in the mixer produces the acceleration up
the flovv^ pipe.
"3l
DVERrya*
EXP TANK
FLOW
/
9
pt»
r
>iixe:r
T f
UJ
— f
o
0.
a:
o
IT
»-
in
o
o
t
Mill
<
-1
UJ
m
HEATER
C3€Z1
RETURN
=B
Fig. 45.
Fig. 46.
In the Jorgensen and Bruchner Systems the heater K
delivers the hot water up the flow pipe to a regulator R,
where a separation takes place between the steam particles
and the water, thus causing an acceleration up the motor
pipe to the expansion tank A. The water in the flow pipe 2
is probably near to the temperature of that in 1. After
passing through the radiators the water in 3 is at a lower
temperature than that in 2. The steam particles which
have collected in the expansion tank A above the water line
are condensed in "F. The acceleration in the system is thusi
produced by a combination of the upward movement of the
steam particles in motor pipe 1 and the induced upward
current in 3 toward the condenser F. It will be noticed
In the figures that the condensation in one system takes
place before the expansion tank and in the other system after
98
HEATING AND Vl«JNTlL,ATiUN
it has passed the expansion tank. Each of the systems illus-
trated may be carried under pressure by a safety valve as
at B or by an expansion tank located high enough to give
sufficient static head.
The third principle is well shown by what is known as
the Reck System. Fig. 47 is a diagrammatic view and Fig.
48 a detail of the accelerating part of the system. The
m
^1^
Fig. 4"
IT y
DETAIL OF A.B.ANOC
Fig. 48.
water passes directly from the heater up the main riser
where it enters the condenser C and thence into the expan-
sion tank A -SiS a. supply to the flow pipes of the system.
Steam from a separate boiler is admitted to the mixer Ji
above the condenser and enters the circulating water just
below the expansion tank. The velocity of the steam and
the partial vacuum caused by the condensation induces a
current up the flow pipe to the expansion tank. W^hen the
water level in the expansion tank reaches the top of the
overflow pipe the water returns to the steam boiler through
the condenser C where it gives off heat to the upper cur-
rent of the circulating water. It will be seen that the
HOT WATER AND STEAM HEATING
99
water in the system and the steam from the boiler unite
from the inlet at the mixer to the expansion tank. On all
other parts of the systems they are independent.
Fig:. 49 is a modification of this same principle, wherein
air is injected in the riser pipe at B and causes the acceler-
ation by a combination of the par-
tial vacuum produced by the steam
condensation as just mentioned and
the upward current of the air par-
ticles as in an air lift. Steam enters
through the pipe J and ejector H to
the mixer at B where it is con-
densed. In passing through H airpLow.
is drawn from the tank E and en-
ters the main riser with the steam.
The upward movement of this air
through the motor pipe to the tank
induces an upward flow of the water
in the main riser. By this combina-
tion there are formed three com-
plete circuits, water, steam and air,
uniting as one circuit from the mix-
er B to the expansion tank E. The Fig. 49.
steam furnished in principle 3 may be supplied by a separate
steam boiler or by steam coils in the fire box of a hot water
boiler.
In the fourth principle the acceleration is produced by
some piece of mechanism as a pump or motor placed direct-
ly in the circuit. This principle is discussed under District
Heating and will be omitted here.
69. Vacuum System.s for Steam: — Most com'monly, the
systems mentioned, when steam, are installed as the so-
called low pressure systems, which term indicates an abso-
lute pressure of about 18 pounds per square inch or 3*^
pounds gage pressure. On extensive work, it has been
found advantageous to install a vacuum system to increase
economy, also to insure positive steam circulation by prompt
removal of condensation through vacuum returns. Even
for comparatively small residence installations vacuum ap-
plications of various kinds are becoming common.
Vacuum systems may be divided into two* classes, ac-
cording to the way in which the vacuum is maintained. For
100
HEATING AND VENTILATION
/T\
comparatively small plants, not using exhaust steam, the
vacuum is maintained by mercury seal connections, and
these plants are usually referred to as mercury seal vacuum
systems. These mercury seals may be attached to any
standard one or two-pipe system by merely replacing the
ordinary air valve by a special connection, which in real-
ity is only a barometer. An iron tube. Fig. 50, dips just
below the surface of the mercury in the well on the floor
and extends vertically to the radiator air tap-
ping to which the tube connects by a fitting
] which will allow air to pass into and through
the barometer, but will not allow steam to
pass. When the system is first fired up and
steam is raised to several pounds gage, the air
leaves all the radiators by bubbling through
the mercury seal at the end of the vertical
iron tube. If the fire is then allowed to go out,
the steam will condense, and produce an almost
perfect vacuum in the entire system, provided
all pipe fitting has been carefully done. This
system may be operated as a vacuum system
at 4 or 5 pounds absolute pressure and have
the water boiling as low as 150 to 160 degrees.
The flexibility of this system recommends it
highly. Applied to a residence or store, the
plant may be operated during the day at sev-
eral pounds gage pressure, if necessary, but
when fires are banked for the night, steam re-
mains in all pipes and radiators as long as the
temperature of the water does not fall much
below 150 degrees. This is in sharp contrast
with the ordinary system, where steam disap-
pears from all radiators as soon as the water
temperature drops below 212 degrees. The
promptness with which heat may be obtained in the morn-
ing is noteworthy, for, if the vacuum has been maintained,
steam will begin to circulate as soon as the water has been
raised to about 150 degrees. According to demands of the
weather, the radiators may be kept at any temperature
along the range of 150 to 220 degrees, thus giving great
flexibility.
"V
Fig. 50.
1
HOT WATER AND STEAM HEATING
101
Instead of having a barometric tube at each radiator,
one mercury seal may be supplied in the basement, and the
air tappings of all radiators connected to the top of the
tube iby i/4 inch piping. In practice it is found very difficult
to obtain a system of piiping isufflcient'ly tight to maintain
a high vacuum Oin the mercury seal system.
The second class of vacuum systems includes those
designed especially for use in office buildings, and where-
in the vacuum is maintained by an aspirator, exhauster or
pump of some description. This exhauster may handle only
^
Fig. 51.
Pig. 52.
the air of the system, that is, it may be connected only
to the air tappings of all radiators, as in the Paul system.
Fig. 51, or the exhauster may handle both air and con-
densation and be connected to the return tappings of all
radiators, as in the Webster system. Fig. 52. The Paul
system is fundamentally a one-pipe system, using exhaust
or live steam and maintaining its circulation without back
pressure, by exhausting each radiator at its air tapping,
and also exhausting the condensation from the basement
tank in which it has been collected by gravity. For an
102 HEATING AND VENTILATION
aspirator this system uses either air, steam, or hot water,
as the conditions may determine. The Webster system Is
fundamentally a two-pipe system and exhausts . from the
radiators both the air and water of condensation, all radi-
ator returns being connected to the (usually) steam driven
vacuum pump. These systems arcdesigned to use both exhaust
and live steam, and hence are finding wide application in the
modern heating of manufacturing plants. See also Chapter
IX.
CHAPTER VII.
HOT WATER AND STEAM HEATING.
RADIATORS, BOILERS, FITTINGS AND APPLIANCES-
The various systems just described are merely different
ways of connecting- the source of heat to the distributors
of heat, i. e., methods of pipe connections between heater
and radiators. Many forms of radiators exist, as well as
many types of heaters and boilers, each adapted to its own
peculiar condition. It is in this choice of the best adapted
material that the heating engineer shows the degree of
his practical training, and the closeness with which he fol-
lows the latest inventions, improvements and applications.
70. Classification as to Material: — Radiators may be
classified, according to material, as cast iron radiators,
pressed steel radiators and pipe coil radiators. Cast radi-
ators have the hollow sections cast as one piece, of iron.
The wall is usually about % inch to % inch thick, and is
finally tested to a pressure of 100 pounds per square inch.
Sections are joined by wrought iron or malleable nipples
which, at the same time, serve to make passageways be-
tween any one section and its neighbors for the current of
heating medium, whether of steam or hot water. Cast iron
radiators have the disadvantage of heavy weight, danger
of breaking by freezing, occupying much space, and having
a comparatively large internal volume, averaging a pint and
a half per square foot of surface.
Pressed radiators are made of sheet steel of No. 16
gage, and, after assembly, are galvanized both inside and
out. Each section is composed of two pressed sheets that
are joined together by a double seam as shown at a, Fig.
53, which illustrates a section through a two-column unit.
Fig. 53.
The joints between the sections or units are of the same
kind. It is readily seen that such construction tends to-
ward a very compact radiating surface. Pressed radia*
104 HEATING AND VENTILATION
tors are comparatively new, but, in their development,
promise much in the way of a light, compact radiation. In
comparison with the cast iron radiators, they are free from
the sand and dirt on the inside, thus causing less trouble
with valves and traps. The internal volume will approxi-
mate one pint per square foot of surface. See Fig. 54.
Radiators composed of pipes, in various forms, are
commonly referred to as coil radiators. They are daily
becoming less common for direct and direct-indirect work,
because of their extreme unsightliness. Piping is still
much used as the heat radiator in Indirect and plenum
systems, although both cast and pressed radiators are now
designed for both of these purposes where low pressure
st3am Is used. In all coil radiator work, no matter for
what purpose, 1 inch pipe Is the standard size. However,
in some cases pipes are used as large as 2 inches in diam-
eter. Standard 1 inch pipe is rated at 1 square foot of heat-
ing surface per 3 lineal feet and has about 1 pint of con-
taining capacity per square foot of surface.
71. Classification as to Form: — Radiators may again be
classified in accordance with form, into the one, two, three,
and four-column floor types, the wall type, and the flue
type. See Fig. 54. These terms refer only to cast and
pressed radiators. By the column of a radiator is meant
one of the unit fluid-containing elements of which a sec-
tion is composed. When the section has only one part or
vertical division, it is called a single-column or one-column
type; when there are two such divisions, a two-column;
when three, a three-column; and when four, a four-
column type. What is known as the wall type radiator Is
a cast section one-column type so designed as to be of
the least practicable thickness. It presents the appear-
ance, often, of a heavy grating, and is so made as to
have from 5 to 9 square feet of surface, according to the
size of the section. One-column floor radiators made with-
out feet are often used as wall radiators. A flue radiator
Is a very broad type of the one-column radiator, the parts
being so designed that the air entering between the sections
at the base is compelled to travel to the top of the sections
before leaving the radiator. This type is therefore well
adapted to direct-indirect work. See Fig. 54.
HOT WATER AND STEAM HEATING
105
Stairway Type Dining Room Type Flue Type Circular Type
CAST RADIATORS
Two-Column
Type
Three-Column
Type
Four-Column
Type
PRESSED RADIATORS
Single-Column Two-Column
Type Type
Three-Column
Type
WaU Typ«
Fig. 54.
106 HEATING AND VENTILATION
Many special shapes of assembled radiators will be
met with, but they will always be of some one of the fun-
damental types mentioned above. For instance, there are
"stairway radiators," built- up of successive heights of
sections, so as to fit along the triangular shaped wall under
stairways; there are "pantry" radiators built up of sections
so as to form a tier of heated shelves; there are "dining
room" radiators with an oven-like arrangement built into
their center; and there are "window radiators" built with
low sections in the middle and higher ones at either end,
so as to fit neatly around a low window. Fig. 54 shows a
number of these common forms as used in practice.
72. Classification as to Heating: 3Iedium: — A third class-
ification of radiators, according to heating medium em-
ployed, gives rise to the terms steam radiator and hot
water radiator. Casually, one would notice little difference
between the two, but in construction there is a vital differ-
ence. Steam radiation has the secvjont. joined by nipples
along the bottom only, but hot water radiation has them
joined along the top as well. This is quite essential to the
proper circulation of the water. Steam radiation is always
tapped for pipe connections at the bottom. Hot water rad-
iation may have the flow connection enter at the top, and
the return connection leave at the bottom, or may have
both connections at the bottom. Hot water radiation can
b heated very successfully with steam, but steam radia-
tion cannot be used with hot water.
73. Hlgrh versns Lo^- Radiators: — In the adoption of a
radiator height, the governing feature is usually the space
allowed for the radiator. Thus, if a radiator of 26 inches
in height requires so many sections as to become too long,
then a 32 inch or a 38 inch section may be taken. In gen-
eral, however, low radiators should be used as far as
possible, for, with a high radiator, the air passing up along
the sides of the sections becomes heated before reaching the
top, and therefore receives less heat from the upper half
of the radiator, since the temperature difference here is
small. Hence, the statement that low radiators are more
efficient, that is, will transmit more B. t. u. per square
foot per hour than will the high radiators.
The amount of heat that will be transmitted through a
radiator to a room is controlled also by the width of the
HOT WATER AND STEAM HEATING 10'
radiator, narrow radiators being more efficient than wide
ones. Considering- both height and number of columns the
rate of transmission, used in formulas 30 and 31 as 1,7, would
change to:
1 column radiator, 30" high 1.8 B. t. u.
2 and 3 " " 30" " 1.7
4 " " 30" " 1.6
For high and low radiators this may be reduced or increased
ten per cent, respectively for a 48 inch and a 16 inch radiator,
74. ESect of Condition of Radiator Surface on the
Transmission of Heat; — The efficiency of a radiator depends
very largely upon the condition of its outer surface, a
rough surface giving off very much moTe heat than a
smooth surface. Painting, ^bronzing, ishellacing or cover-
ing the radiatoir in any manner affects the ability of the
radiator to impart heat to the air circulating around it.
Various tests bearing upon this question have been con-
ducted, agreeing fairly well in general results, A series
of tests conducted by Prof, Allen at the University of
Michigan, indicated that the ordinary bronzes of copper,
zinc or aluminum caused a reduction in the efficiency below
that of the ordinary rough surface of the radiator of
about 25 per cent., while white zinc paint and white enamel
gave the greatest efficiency, being slightly above that of
the originail surface Numerous coats of paint, even as high
as twelve, seemed to affect the efficiency in no appreciable
manner, it being the last or outer coat that always de-
termined at what rate the 'radiator would transmit its heat.
75, Amount of Surface Presented by Various Radiators:—
Table X, gives, according to the ■columns and heights,
the number of square feet of heating surface per section
in cast and pressed radiators. This table will be found to
present, in very compact form, the similar and much more
extended tables in the various manufacturers' catalogs.
An approximate rule supplementing this table and giving,
to a very fair degree of accuracy, the square feet of sur-
face in any standard radiator section, Is as follows: mul-
tiply the height of the section in inches hy the number of columns
and divide ty the constant 20. The result is the square feet of
radiating surface per section. The rule applies. with least ac-
curacy to the one-column radiators.
108
HEATING AND VENTLATION
TABLE X.
Dimensions and Surfaces of Radiators, per Section.
Type of
Radiator
11
c —
"SB
Radiator Heiglit!
i.
^i
gg
45'
38"
82»
26»
23"
22"
20"
18"
16«
14»
8
3
9M
2
1^
\%
1 Ool 0. I.
2 0ol. 0. I
8
8
6
4
8H
iy^
2}i
2
SOol.O.I
9%
8
6
5
4H
s%
3
2J<
40ol.O. I
11
8>^
10
8
6}i
5
4
8
....
Flue Wide....
1?^
8
(f
5^
4%
4
8
8
7
fm
4V4
1 Ool. Press...
4
IH
1%
l>i
1
....
X
2 Ool. Press ..
7%
2
4
S'A
2J4
2
IM
8 Ool. Press . .
WA
2%
....
Wk
4?i
8H
....
....
2Vi
1 Ool. Wall
8H
1%
1
^
Pressed
76. Hot Water Heaters: — Heaters for supplying the hot
water to a heating system may be divided into three classes-.
— the round vertical, for comparatively small installations;
the sectional, for plants of medium size; and the water tube
or fire tube heater with brick setting for the larger In-
stallations and for central station work. The round and
sectional types usually have a ratio between grate and
heating surface of 1 to 20, while the water tube or fire tube
heater will have, as an average, 1 to 40. Many different
arrangements of heating surface are in use to-day, every
manufacturer having a product of particular merit. Trade
catalogs supply the most up-to-date literature on this
subject, but cuts of each of the types mentioned above may
be found in Fig. 55.
77. Steam Boilers: — The products of many manufac-
turers show but little difference between the hot water
heater and the steam boiler. The latter is usually supplied
with a somewhat larger dome to give greater steam stor-
age capacity. For heating purposes, steam boilers fall
into the same three classes as mentioned under water heat-
HOT WATER AND STEAM HEATING
109
ers, having about the same ratio of heating surface to grate
surface. With the steam boiler generating steam at
5 pounds gage, the temperature on one side of the heating
surface is about 227 degrees, while in a water heater the
temperature on the same side is about 180 degrees. Hence,
with the same temperature of the burning gases, the tem-
perature difference is greater in a water heater than in a
Bound Under-Feed
Sectional Top Feed
Fire Tube Type
Fig. 55.
110
HEATING AND VENTILATION
boiler, resulting in a more rapid transfer of heat, and A
correspondingly greater efficiency.
78. Combination Systems;— Combination systems are
frequently used, principally the one which combines warm
air heating with either steam or hot water. For such a
system there is needed a combination heater, as shown In
Fig. 20. It consists essentially of a furnace for supplying
warm air to some rooms, the downstairs of a residence for
instance, and contains also a coil for furnishing hot water
to radiators located in other rooms, say, on the upper floors,
or in places where it would be difficult for air to be de-
livered. Considerable difficulty has been encountered in
properly proportioning the heating surface of the furnace
to that of the hot water heater, and the systems have not
come into general use.
79. Fittingrs: — Common and Special t— 'Couplings, elbows
and tees, especially for hot water work, should be so formed
as to give a free and easy sweep to the contents. It is
highly desirable in hot "water work to use pipe bends of a
Fig. 56.
radius of about fiVQ pipe diameters, instead of the common
elbow. In either case all pipe ends should be carefully
reamed of the cutting burr before assembling. This is
most important, as the cutting burr is sometimes heavy
enough to reduce the area of the pipe by one-half, thus
creating serious eddy currents, especially at the elbows.
If the single main hot water system be installed, great
care should be used to plan the mains in the shortest and
most direct routes, and the special fittings described and
shown in Art. 65 should be used.
Eccentric reducing fittings are often of value In avoiding
pockets in steam lines. Fig. 56 shows types of these, which
should always be used when, by reduction or otherwise, a
HOT WATER AND STEAM HEATING
111
harizontial steam pipe would present a pocket for the col-
lection of condensation with its resultant water hammer.
Valves for either steam or hot water should be of the
gate pattern rather than the globe pattern. The latter is
objectionable in hot water systems because of the resistance
offered the stream of water, due to the fact that the axis
of the valve seat opening is perpendicular to the axis of
the pipe. The globe valve is objectionable in some
steam lines because of the fact that in a horizontal run
of pipe it forms very readily a pocket for the collection
of condensation, thus often producing a source of water
hammer. In every way gate valves are preferable, for, as
shown in Fig. 57, they present a free opening without turns.
The same caution applies
in the use of check valves.
Swing checks should al-
ways be specified rather
than lift checks, for the
former ofEer much less re-
sistance to the passage of
the hot water, or the
steam and condensation, as
the case may be. Fig. 58
shows a lift check and a
Fie 57
^* swing check.
To avoid the annoyance so often experienced by leaky
packing around valve stems, there have been designed and
Fig. 58.
placed on the market various forms of packless valves.
These are to be especially recommended for vacuum work,
as the old style valve with its packed stem Is, perhaps, the
cause of more failures of vacuum systems than any other
one item. Fig. 59 shows a section of this type of valve using
112
HEATING AND VENTILATION
the diaphragm as the flexible wall. AW
packless valves will be found to use a dia-
phragm of one 'form or another.
Quick-opening Valves, or butterfly valves,
are much used on hot water radiators; one-
quarter turn of the wheel or handle serves
to open these full and, when closed, they
are so arranged that a small hole through
IFigr. 59. the valve permits just enough leakage to
keep the radiator from freezing. Special radiator valves for
steam may also be obtained.
Air valves have a most important function to dischargee.
As the air accumulates above the water or steam In th«
Fig. 60.
radiators, Its removal becomes absolutely necessary, If all
of the radiating surface is to remain effectual. For this
purpose small hand valves or pet cocks, Fig. 60, are in-
serted near the top of the end section in all hot water
work; and either these same valves or automatic ones are
inserted for steam work. Valves are not as essential on
two-pipe steam systems as on water or single-pipe steam
systems, yet are generally used. For steam the air valve
should be about one-third the radiator height from the top.
Fig. 61 shows a common type
of automatic air valve using the
principle of the expansion stem. As
long as the air flows around the
stem and exhausts, the stem re-
mains contracted, and the needle
valve open; but when the hot steam
enters and flows past the expansion
stem. It lengthens sufllciently to close the needle valve. In
other forms of air valves the heat of the steam closes the
needle valve by the expansion of a volatile liquid in a small
closed retainer. In still other forms the lower part of the
valve casing is filled with water of condensation upon
which floats an inverted cup, having air entrapped wlthla.
Fig. 61.
HOT WATER AND STEAM HEATING
113
This cup carries the needle of the valve at its upper ex-
tremity, the heat of the steam expanding the air sufficiently
to raise the cup and close the valve. Where the system is de-
signed to act as a gravity installation, special air valves must
be used which will not allow air to enter at any time. Fig.
€2 shows a type of automatic valve designed to accommo-
date larger volumes of air with promptness,
as when a long steam main or large trap is
to be vented. This type employs a long cen-
tral tube, as shown, which carries at the top
the valve seat of the needle valve. The
needle itself is carried by the two side rods.
As long as the air flows up through the
central pipe, the needle valve will remain
open; but when hot steam enters the tube,
it expands, and carries the valve seat up-
ward against the needle, thus closing the
valve. The size and strength of parts makes
this form a very reliable one.
The expansion tank. Fig. 63, for a hot wat-
er system is often located in the bath room or
closet near the bath room and its overflow
connected to proper drainage. It should be
at least 2 feet above the highest radiator.
The connection to the heating system mains
Is most often by a branch from the nearest
radiator riser, or it may have an independ-
ent riser from the basement flow main. The
capacity of the tank is usually taken at
about one-twentieth of the volume of the
entire system, or a more easily applied rule
is to divide the total radiation 6|/ 40 to obtain the
See Table 39, Appendix.
{Fig. 62.
capacity of the tank in gallons
Fig, 63.
CHAPTER VIII.
HOT >VATER AND STEAM HEATING.
PRINCIPLES OF THE DESIGN, WITH APPLICATIOK.
In a hot water or steam system, the first Important
Item to be determined by calculation is the amount of
radiation, in square feet, to be installed in each room.
Nearly all other items, such as pipe sizes, boiler size, grrat«
area, etc., are estimated with relation to this total radia-
tion to be supplied. The correct determination, then, of
the square feet of radiation in these systems is all-Im-
portant.
80. Calculation of Radiator Surface: — Considerlngr the
standard room of Chapter III, where the heat loss was de-
termined to be 14000 B. t. u. per hour on a zero day, the
problem is to find what amount of surface and what size of
radiator will deliver 14000 B. t. u. per hour to the room,
under the conditions as given. Experiments by numerous
careful investigators have shown that the ordinary cast Iron
radiator, located within the room and surrounded with com-
paratively still air, gives off heat at the rate of 1,7 B. t. u.
(1.6 to 1.8, or 1.7 average) per square foot per degree
difference between the temperature of the surrounding air
and the average temperature of the heating medium, per
hour. This is called the rate of transmission. With hot
water the average conditions within the radiator have
been found to be as follows: temperature of the water en-
tering the radiator 180 degrees; leaving the radiator 160
degrees; hence, the average temperature at which the in-
terior of the radiator is maintained is 170 degrees. Since,
In this country, the standard room temperature is 70 de-
grees, and, for hot water, the "degree difference" Is 170 —
70 = 100, then a hot water radiator will give off under
standard conditions 1.7 X 100 = 170 B. t. u. per sq. ft. per hour.
The temperature within a steam radiator carrying steam at
pressures varying between 2 and 5 pounds gage is usually
taken at 220 degrees, and the total transmission is approx-
imately 1.7 X (220 — 70) = 255 B. t. u. per square foot per
hour. The general formula for the square feet of radiation,
then, is
H — Total B. t. u. lost from the room per hour
1.7 (Temp. diff. between inside and outside of rad.)
For Jiot water, direct radiation heating, this becomes, to the
nearest thousandth
H
Rw = = .006 H (30)
1.7 (170 — 70)
For steam, direct radiation
H
Rs = = .004 H (31)
1.7 (220 — 70)
Rule. — To find the square feet of radiation for any room divide
the calculated heat loss in B. t. u. per hour hy the quantity 1.7
times the difference in temperature "between the inside and the out-
side of the radiator.
It will be noticed from (30) and (31) that Rw = 1.5 Rs which
accounts for the practice that some people have of finding
all radiation as though it were steam, and then, when hot
water radiation is desired, adding 50 per cent, to this
amount.
Application. — From the standard room under considera-
tion, formula 30 gives Rw = .006 X 14000 = 84 square feet
of radiator surface for hot water; and formula 31 gives R*
= .004 X 14000 = 56 square feet of radiator surface for
steam. From these values the number of sections of a giv-
en type of radiator can be determined by dividing by the
area of one section, as explained in the preceding chapter.
The length of the radiator may also be found from this
same table, by noting the thickness of the section*?, and
multiplying by their number.
Formulas 30 and 31 give the standard ratios be-
tween the heat loss and direct radiation. If, however, the
radiation is installed as direct-indirect, it is quite common
practice to increase the amount of direct radiation by 25
per cent, to allow for the ventilation losses. On this basis
formulas 30 and 31 become, respectively,
Rw = .0075 H (32)
Rs = .005 H (33)
Duct sizes for properly accommodating the air in
direct-indirect heating may be taken from the following:
116 HEATING AND VENTILATION
To obtain the duct area in square inches, multiply the square feet
of radiation by .75 to 1 for steam, and by .5 to .75 for hot water.
To obtain the amount" of air which may be expected to enter and
pass through the radiator into the room, multiply the square feet
of radiation by 100 for steam, or by 75 for hot water. This gives
the cubic feet of air entering per hour.
Again, if the radiation is insta'lled as purely indirect,
yet not as a plenum system, it is common to increase the
amount of direct radiation by 50 per cent. Now formulas 30 and
31 become, respectively,
Rw — .009 H (34)-a
Rs = .006 H (34)-b
For proportioning the duct sizes in indirect heating
use the following table. To obtain the duct area in square
Inches, multiply the square feet of radiation installed by
Steam Hot Water
First Floor 1.5 to 2.0 1.0 to 1.33
Second Floor 1.0 to 1.25 .66 to .83
Other Floors .9 to 1.0 . 6 to .66
Vent ducts, where provided, are usually taken .8 of the
area of supply ducts. Also, for finding the amount of air In
cubic feet, which may be reasonably expected to enter
under these conditions. Carpenter gives the following:
Multiply the square feet of indirect radiation by
Steam Hot Water
First Foor 200 150
Second Floor 170 130
Other Floors 150 115
If this amount of air is insufficient for the desired degree
of ventilation, more air must be brought in by correspond-
ingly larger ducts, and for each 300 cubic feet additional
with steam, or each 200 cubic feet additional with hot
water, add one square foot to the radiation surface.
A steam system may be installed to work at any pres-
sure, from a vacuum of, say, 10 pounds absolute, to as high
a pressure as 75 pounds absolute. To calculate the prop-
er radiation for any of these conditions use formula 31 or
its derivatives, and substitute the proper steam tempera-
ture in place of 220 degrees.
In like manner, to find the amount of hot water radi-
ation for any other average temperatures of the water
HOT WATER AND STEAM HEATING 117
than the one given, merely substitute the desired average
temperature in the place of 170. One point should be re-
membered, the maximum drop in temperature as the water
passes through the heater will seldom be more than 20
degrees, even under severe conditions. More often it will
be less, but this value is used in calculations. Again, the
temperature of the entering water may be at the boiling
point, if necessary, thus causing each square foot of sur-
face to be more efficient and consequently reducing the to-
tal radiation in the room. To illustrate, try formula 30
with a drop in temperature from 210 to 190 degrees and find
64 square feet of radiator surface for this room. Since a
radiator always becomes less efficient from continued use, it
is best to design a system with a lower temperature as
given in the formula, and then, if necessary under stress
of conditions, this system may be increased in capacity by
increasing the water temperature up to the boiling point.
81. Empirical Formulas: — All of the above formulas may
be considered as rational and checked by years of experience
and application. Many empirical formulas have been de-
vised in an attempt to simplify, but the results are always
so untrustworthy that the rules are worthless unless used
with that discretion which comes only after years of prac-
tical experience. Many of these rules are based on the
cubic feet of volume heated, without any other allowance,
these being given anywhere from one square foot of steam
surface per 30 cubic feet of space, to one square foot to
100 cubic feet. The extreme variation itself shows the un-
reliableness of this method, and under no conditions should
it be used for proportioning radiating surface. Various
central heating companies, and others, proportion radia-
tors for their plants according to their own formulas,
among which the following may be noted.
G W G G W G
(a) Rv, = 1 1 R, = h f-
2 10 60 2 10 200
2
(b) Rio — G + .05 W + .01 C Rs =— (G + .05 W + .01 C)
3
(c) Rw = .75 G + .10 W + .01 C Rs = .B G + .05 W + .005 G
It is evident that these are really simplified forms of Car-
penter's original formula. "When applied to the sitting
room, where Carpenter's formula gave, for hot water and
steam, 84 square feet and 56 square feet, respectively, (a)
118 HEATING AND VENTILATION
gives 85.5 and 63, (b) gives 75 and 50, and (c) gives 82.5
and 46 respectively.
Another approximate rule devised by John H. Mills
anl still used to some extent is "Allow 1 square foot of
steam radiation for every 200 cubic feet of volume, 1 square
foot for every 20 square feet of exposed wall and 1 square
foot for every 2 square feet of exposed glass." Applying
this to the standard room, it gives 9.75 + 13.25 + 18 = 41
square feet of steam radiation as against 56 square feet
by rational formula. This shows a considerable difference
from the. rules preceding,
82. Greenhouse Radiation: — The problem of properly
proportioning greenhouse radiation is considered, by some,
of such special nature as to justify the use of empirical
formulas. The fact that the glass area is so large compared
to the wall area and the volume, combined with the fact
that the head of water in the system is small and that the
radiation surface is usually built up as coils from 1%, 1% or
2 inch wrought iron pipe, gives rise to a problem that differs
essentially from that of a room of ordinary construction. It
is not surprising, therefore, to find a great variety of empir-
ical formulas designed exclusively for this work. Whatever
merit these may ^ave, they do not give the assurance that
comes from the application of rational formulas. It Is always
best to use rational formulas first and then check by the
various empirical methods.
Formulas 30 and 31, stated in Art. 80, when properiy
modified, are applicable to greenhouses and give very re-
liable results. As stated above, the radiating surface is
usually that of wrought iron pipes hung below the flower
benches or along the side walls below^ the glass. The trans-
mission constant, K, for wrought iron or mild steel is 2.0 to
2.2 B. t. u. per square foot per degree difference per hour,
making the total transmission per square foot of coil surface
per hour about 2(170 — 70) = 200 for hot water, and 2(220
— 70) = 300 for steam. These values may be safely used.
The only necessary modification of the two formulas men-
tioned, consists in replacing the constant 1.7 by 2, giving
for hot icater jj
RxB = = .005 H (35)-a
2(170 — 70)
And for ateam
"•= 2(220-70) =■«»'"' ""-"
HOT WATER AND STEAM HEATING
119
If, however, the highest temperature at which it is desirable
to maintain the house in zero weather is other than 70 de-
grees, this temperature should be used instead of 70.
In a greenhouse there is very little circulation of air,
hence the heat loss, H, would be found from the equivalent
glass area i. e., (G + -25 W). Formulas 35-a and 6 would
then reduce to Rxo = .35 (G + .25 W) and Rs = .23 ((? + .25 W).
It is noticed that these values give about one square foot of
H. W. radiation to 2.8 square feet of equivalent glass area, and
one square foot of steam radiation to 4:. 4: square feet of equivalent
glass area as approximate rules. These figures should be considered
a minimum.
Empirical rules for greenhouse radiation, quoted by
many firms dealing in the apparatus, are usually given in
the terms of the number of square feet of glass surface
heated by one lineal foot of 1^4 inch pipe. A very commonly
quoted and accepted rule is, one foot of 1% inch pipe to
every 2^/4 square feet of glass, for steam; or, one foot of
1^/4 inch pipe to every 1% square feet of glass, for hot water,
when the interior of the house is 70 degrees in zero weather.
Table XI, taken from the Model Boiler Manual, shows
the amount of surface for different interior temperatures
and different temperatures of the heating medium.
In general, it may be said that in greenhouse heating,
great care should be used in the rating and the selection
RISE FOF
WATER OR STEAr-l
Fig. 64.
of the boilers or heaters. It is well to remember that the
severe service demanded by a sudden change in the weather
is much more difficult to meet in greenhouses than in ordin-
ary structures, and that a liberal reserve in boiler capacity
is highly desirable.
If any greenhouse under consideration can be heated
from some central plant where the heat will be continuous
throughout the night with a man in charge at all times,
120
HEATING AND VENTILATION
then steam Is very desirable because of the reduced amount
of heating surface necessary. If, however, In cold weather
the steam pressure to be allowed to drop during the night-
time, then hot water should be used. This permits a better
circulation of heat throughout the greenhouse during the
night. The same rules apply in running the mains and
risers as would apply in the ordinary hot water and steam
systems. In greenhouse work the head of water is very
low and this makes the circulation rather sluggish but with
sufficient pipe area and a minimum friction a hot water
system may be used with satisfaction. In some houses the
coils are run along the wall below the glass and supported
on wall brackets, in others they are run underneath the
benches and supported from the benches with hangers,
while in greenhouses with very large exposure there -are
sometimes required both wall and bench coils. In all of
these piping layouts it is necessary that a good rise and
fall be given to the pipes. Fig. 64 shows two systems of
pipe connections, one where the steam or flow enters the
coils from above the benches and the other where it enters
from below, the return in each case being at the lowest
point. These bench coils could be run along the wall with
equal satisfaction.
TABLE XL
©a,
Temperature of Water in Heating Pipes
Steam
S
E-t
140O
I6OO
I8OO
200'5
Three lbs.
Pressure
Square feet of glass and its equivalent pro
portioned to
one square foot of surface In heating pipes
J or radiator
40°
4.33
5.26
6 66
7.69
8.
7.6
45°
8.63
4.65
6 56
6.66
7.6
6.75
600
8.07
8. 92
4 76
6.71
7.
6.0
650
2.63
8.39
4. 16
5.
6.6
6.6
60O
2. 19
2. 89
8. 68
4.83
6.
5.0
66°
1.86
2. 58
8. 22
8.84
5.6
4.5
70O
1.68
2.19
2.81
8 44
6.
4.26
750
1.87
1.92
2 6
8.07
4.6
4.0
800
1.16
1.68
2. 17
2 78
4.
3.75
850
.99
1.42
1.92
2.46
8.5
8.6
This table is computed for zero weather; for lower
temperatures add 1% per cent, for each degree below zero.
HOT WATER AND STEAM HEATING 121
The last column in Table XI- has been calculated from
formula 35-b and added for purpose of comparison.
Application. — Given an even span greenhouse 25 ft. wide,
100 ft. long and 5 ft. from ground to eaves of roof, having
slope of roof with horizontal 35°. Ends to be glass above
the eaves line. What amount of hot water radiation with
water at 170° and what amount of low pressure steam radia-
tion would be installed?
Length of slope of roof = 12.5 -^ cos. 35° = 15.25.
Area of glass = 15.25 X 100 X 2 + 2 X 12.5 X 8.8 = 3270
sq. ft.
Area of wall = 5X100X2 + 5X25X2 = 1250 sq. ft.
Glass equivalent = 3270 + .25 X 1250 = 3582.5 sq. ft.
Rw= .35 X 3582.5 = 1253.8 sq. ft.
iJs = .23 X 3582.5 = 824. * ,sq. ft.
From Table XL
Riv= 3582.5 -r 2.5 = 1433 sq. ft.
Rs = 3582.5 -r- 5 = 716. .sq. ft.
♦Check with last column of Table XI.
83. The Determination of Pipe Siz^s: — The theoretical
determination of pipe sizes in hot water and steam systems
has alw^ays been more or less unsatisfactory, first, because
of the complicated nature of the problem when all points
having a bearing upon the subject are considered, and
second, because it is almost an impossibility to even ap-
proximate the friction offered by different combinations and
conditions of piping. The following rather brief analysis
gives a theoretical method for determining pipe sizes where
friction is not considered.
In a hot water system let the temperatures of the water,
entering and leaving the radiator be, respectively, 180
and 160 degrees; then it is evident that one pound of the
water in passing through the radiator, gives off 20 B. t. u.
Under these conditions the standard room would have 14000 -4-
20 = 700 pounds of water passing through the radiator per
hour. Converting this to gallons, it is found to be 84.03.
But the radiation for this room was found to be 84 square
feet. Therefore, it may be said that a hot water radiator
unde" normal conditions of installation and under heavy
service requires one gallon of water per square foot of sur-
face per hour. Knowing the theoretical amount of water
per hour, it remains only to obtain the theoretical speed
122 HEATING AND VENTILATION
at which it travels, due to unbalanced columns, to obtain
finally, by division, the theoretical area of the pipe.
Consider a radiator to be about 10 feet above the
source of heat, and the temperature in the flow riser to be
180 degrees and in the return riser 160 degrees, good values
in practice. Now the heated water in the flow riser
weighs 60.5567 pounds per cubic foot, while that in the
return riser weighs 60.9697 pounds per cubic foot. The mo-
tive force Is f =^ g ( ) where g is the acceleration
\ W + W /
due to gravity, W is the specific gravity (weight) of the
cooler column and W is the specific gravity (weight) of the
warmer column. Substitute / for g in the velocity formula
and obtain v = •^2fh and
W — W
v=^l 2ghl ) (36)
: J 2gh{ )
Inserting values W, W and assuming 7» = 10 feet, we have
p = V2 X 32.2 X 10 X .0034 = V2.1S96 = 1.47 feet per second.
From this it has become a custom to speak of 1.5 feet per
second or 5400 feet per hour, as the theoretical velocity of
water in, say, a first floor riser, disregarding the effect of
all friction and horizontal connections. Theoretical veloci-
ties for any other height of column and for other temper-
atures may be obtained in like manner. Continuing this
special investigation and changing the 84 gallons per hour
to cubic inches per hour by multiplying by 231, the internal
pipe area may be obtained by dividing by the unit speed
per hour which gives (84 X 231) -^ (5400 X 12) = .3 square
inch. This corresponds to approximately a % inch pipe
and without doubt, would supply the radiator if the sup-
position of no frictional resistances could be realized. This
ideal condition, of course, cannot be had, nor can the fric-
tion in the average house heating plant be theoretically
treated with any degree of satisfaction. Hence it is still
the custom to use tables for the selection of pipe sizes,
based upon what experience has shown to be good practice.
Such tables, from various authorities, may be found in the
Appendix. It is safe to say that one should never use any-
thing smaller than a 1 inch pipe in low pressure hot water
work.
■^'ith steam system*, where the heating medium is a vapor.
HOT WATER AND STEAM HEATING 123
and subject in a lesser degree to friction, the discrepancy
between the theoretical and the practical sizes of a pipe
is not so great as in hot water. Each pound of steam, in
condensing, gives off approximately 1154 — 181 = 973 B. t. u.
To supply the heat loss of the standard room, 14000 B. t. a.
per hour, it would require 14.5 pounds of steam per hour.
When it is remembered that the calculated surface of the
direct steam radiator for this room was 56 square feet, it
appears that a radiator, under stated conditions and under a
heavy service, requires one-fourth of a pound of steam per square
foot of surface per hour. This may be shown in another way:
each square foot of steam radiation g-ives off 255 B. t. u.
per hour; then, each square foot will condense 255 -r- 973 =
.26 + pounds of steam per hour.
Now the volume of the steam per pound at the usual
steam heating pressure, 18 pounds, absolute, is 21.17 cubic
feet. Since the standard room radiator required 14.5 pounds
per hour, it would, in that time, condense steam corres-
ponding to a void of 21.17 X 14.5 = 307 cubic feet per hour.
This is the volume of the steam required by the radiator,
and, if the speed of the steam in the pipe lines be taken
at 15 feet per second, or 54000 feet per hour, the area of
the pipe would be 307 X 144 ~- 54000, or .82 square inch,
corresponding very closely to a 1 inch pipe. For a two-
pipe system this would be considered good practice under
average conditions; but in a one-pipe system, where the
condensation is returned against the steam in the same
pipe that feeds, a pipe one size larger would be taken.
Table 35, Appendix, calculated from Unwin's formula,
may be used in finding sizes and capacities of pipes carrying
steam. In addition to this, Tables 31, 32, 33 and 34 give sizes
that are recommended by experienced users.
For a theoretical discussion of loss of head by friction
in hot water and steam pipes, see Arts. 147 and 175.
84. Grate Area; — To obtain the grate area for a direct
radiation hot water or steam system by the B. t. u. method,
the same analysis as found in Chapter IV may be applied.
The total B. t. u. heat loss, H, is that calculated by the
formula and does not include Hv, the heat loss due to ven-
tilation, since with the direct hot water or steam system as
usually installed no ventilation is provided. In any special
case where ventilation is provided in excess, use H' instead
of H. The commercial rating of heaters and boilers is a
124 HEATING AND VENTILATION
subject each day receiving greater attention at the hands
of manufacturers; yet it is a subject where much uncer-
tainty is felt to exist. Hence the recommendation, "Always
check grate area by an actual calculation," rather than rely
entirely upon the catalog ratings.
85, Pitch of Mains: — The pitch of the mains is quite as
important in liot water as in steam work. This should be
not less than 1 inch in 10 feet for hot water systems, and not
less than 1 inch in 30 feet for steam systems. Greater
pitches than these are desirable, but not always practic-
able. In hot water plants the pitch of the basement mains,
whether flow or return, is upward as these mains extend
from the source of heat, that is, the highest point Is the
farthest from the heater. In steam plants the mains, under
any condition of arrangement, always pitch downward
in the direction of the flow of the condensation.
86. Location and Connection of Radiators: — In locat-
ing radiators, it is best to place them along the outside or
the exposed walls. When allowable, under the windows
seems to be a favorite position. Especially in buildings
of several stories, the radiators should be arranged, where
possible, in tiers, one vertically above another, thus re-
ducing the number of and avciding the offsets in the risers.
In the one-pipe system any number of radiators may be con-
nected to the same riser. In the two-pipe system several
radiators may have either a common flow riser, or a common
return riser, but should never have both, either with hot
water or with steam.
The connections from the risers to the radiators should
be slightly pitched for drainage and are usually run along
the ceiling below the radiator connected. These connections
should be at least two feet long to give that flexibility of
connection to the radiator made necessary by the expan-
sion and contraction of the long riser. Similarly, all risers
should be connected to the mains in the basement by hori-
zontals of about two feet to allow for the expansion and
contraction of the mains. A system thus flexibly connected
stands In much less danger of developing leaky joints than
does one not so connected. For sizes of radiator connections
see Table 29, Appendix.
HOT WINTER AND STEAM HEATING 125
87. General Application: — Figs. 65, 66 and 67 show the
typical layout of a hot water plant. Due to the similarity be-
tween hot water and steam installations, the former only will
be designed complete. In attempting the layout of such a
system, the very first thing to be done is to decide at what
points in the rooms the radiators should be placed. This
should be done in conjunction with the owner as he may
have particular uses for certain spaces from which radia-
tors are hence excluded. The first actual calculation should
be the heat loss from each room, with the proper exposure
losses, and the results should be tabulated as the first
column of a table s.imilar to Table XII. In the
example here given, this loss is the same as, and taken
from, the table of computations for the furnace work. Art.
48, the house plans being identical. The second column
of Table XII, as indicated, is the square feet of radiation;
and since this is a hot water, direct radiation system. It
is obtained by taking .006 of the items in the first column
according to formula 30. Knowing this, a type and
height of radiator can be selected, and the number of
sections determined by Table X. Next obtain the lengths
of radiators by multiplying the number of sections by the
total thickness of the sections, as given in Table X, and
determine whether or not the radiator of such a length
will fit into the chosen space. If not, then a radiator of
greater height and larger surface per section must be
selected. Riser sizes and connections may be taken ac-
cording to Tables 31 and 29 respectively. The column of
Table XII headed "Radiators Installed" gives first the num-
ber of sections; second, the height in inches; and third, the
number of columns or type of the section.
Locate radiators on the second floor and transfer the
location of their riser positions to first floor plan, then to
the basement plan. Locate radiators on the first floor and
transfer their riser locations to the basement plan, which
will then show, by small circles, the points at which all
risers start upward. This arrangement will aid greatly in
the planning of the basement mains.
The keynotes in the layout of the basement mains
should be simplicity and directness. If the riser positions
show approximately an even distribution all around the
basement, it may be advisable to run the mains in
126 HEATING AND VENTILATION
complete circuits around the basement. If, again, the
riser positions show aggregation at two or three localities,
then two or three mains running directly to these localities
would be most desirable. As an example, take the applica-
tion shown here. The basement plan shows three clusters
of riser ends, one under the kitchen, another under the
study, and a third on the west side of the house. This
condition immediately suggests three principal mains, as
shown. The main toward the kitchen supplies the bath,
chamber 4 and the kitchen, making a total of 131 square
feet. Being only about 13 feet long, it would readily carry
this radiation if of 2 inch diameter. See Table 34, Appendix.
The main to the study and the hall supplies chamber 1, the
hall and the study, making a total of 221 square feet, which,
can be carried by a 2^^ inch pipe. The main to the west side
of the house supplies chamber 2, chamber 3, the sitting room
and the dining room, a total of 249 square feet, which would
almost require a 3 inch main, according to the table, were
it not for its comparatively short length. A 2^4 inch pipe
would amply supply this condition.
In hot water work, as well as in steam, it is customary
to take the connections to flow risers from the top of the
mains, thus aiding the natural circulation. Fig. 35. If not
taken directly from the top of the main, it is often taken at
about 4.5 degrees from the top. This arrangement, with a
short nipple, a 45 degree elbow, and the horizontal connec-
tion about 1^/^ to 2 feet long, makes a joint of sufficient
flexibility between the main and riser to avoid expansion
troubles.
In the selection of a heater or boiler much that has
been said concerning furnaces applies. The heater or boiler
should, above all, have ample grate area, checked on a B.
t. u. basis, and should have a sufficient heating surface so
designed that the heated gases from the flre impinge per-
pendicularly upon it as often as may be without seriously
reducing the draft. As shown by the total of the radiation
column, a hot water boiler should be selected of such rated
capacity as to include the loss from the mains and risers.
Since this loss is usually taken from 20 to 30 per cent., de-
pending upon the thoroughness with which the basement
mains are insulated, the heater for this house should have
a rated capacity of not less than 720 square feet of radiation.
HOT WATER AND STEAM HEATING
TABLE XII.
127
rt a
<a o
^B
oil
84
65
80
70
Radiators
installed
Leng-ths
of rad'or
installed
Riser
sizes
1 to
a)
M
to
4>
CO
o
a
to
to
p
to
C<1
D
42
54
60
24
o
VA
1%
a
i-i
■u
VA
V4
VA
Sitting R
14000
10800
13250
11900
15-32-3
14-26-3
32-14-3
12-32-3
14-44-3
18-26-3
20-14-F
8 -45-4
34
32
72
26
IJ^
Dining R
1J<
Study
IJ^
Kitclien
1J4
Rec'p'n Hall . . .
14000
84
15-32-3
14-44-3
84
42
VA
IVi
VA
Chamber 1
9400
57
13-26-3
16-26-3
30
48
VA
VA
VA
Otiaraber 2
9850
60
13-26-3
16-26-3
30
48
VA
VA
IVa
Chambers
6600
40
10-26-3
12-26-3
23
86
1
1
1
Chamber 4
5600
35
10-26-3
12-26-3
23
36
1
1
1-
Bath
4400
26
601
6-26-3
7-26-8
14
21
1
1
1
J
128
HEATING AND VENTILATION
17 — 6
i+e-'U*
■-•'» ;*
»«i»;f-i
FOUNDATION PLAN.
Ceiling 6'.
Flgr. 65.
HOT WATER AND STEAM HEATING
129
FIRST FLOOR PLAN.
Ceiling 10'.
Fig. 66.
130
HEATING AND VENTILATION
' i.\n.v-iA' /\
SECOND FLOOR PLAN.
Ceiling 9'.
Fig. 67.
HOT WATER AND STEAM HEATING
131
1226^ 7-26-3
ExpTonK.
I6-26-3
l4-'^A-3
16-26-3
MAIN AND RISER LAYOUT.
Fig. 67a.
88. Insulatlns Steam Pipes: — In all heating systems,
pipes carrying steam or water should be insulated to protect
from heat losses, unless these pipes are to serve as radiating
surfaces. In a large number of plants the heat lost through
these unprotected surfaces, if saved, would soon pay for first
class insulation. The heat transmitted to still air through
132 HEATING AND VENTILATION
one square foot of the average wrought iron pipe is from 2
to 2.2 B. t. u. per hour, per degree difference of temperature
between the inside and the outside of the pipe. Assuming
the minimum value, and also that the pipe is fairly well
protected from air currents, the heat loss is, with steam at
100 pounds gage and 80 degrees temperature of the air,
(338 — 80) X 2 = 516 B. t. u. per hour. With steam at 50, 25
and 10 pounds gage respectively this will be 436, 374 and 320
B. t. u. If the pipe were located in moving air, this loss would
be much increased. It is safe to say that the average low pres-
sure steam pipe, when unprotected, will lose between 350 and
400 B. t. u. per square foot per hour. Taking the average of
these two values and applying it to a six inch pipe 100 feet
in length, for a period of 240 days at 20 hours a day, we have
a heat loss of 171 X 375 X 240 X 20 = 307800000 B. t. u. With
coal at 13000 B. t. u. per pound and a furnace efficiency of 60
per cent, this will be equivalent to 39461 pounds of coal,
which at $2.00 per ton will amount to $39.46. From tests
that have been run on the best grades of pipe insulation, it is
shown that 80 to 85 per cent, of this heat loss could be
saved. Taking the lower value we would have a financial
saving of $31.56 where the covering is used. Now if a good
grade of pipe covering, installed on the pipe, is worth $35.00,
the saving in one year's time would nearly pay for the
covering.
To l:e effective, insulation should be porous but should
be protected from air circulation. Small voids filled with
still air make the best insulating material. Hence, hair
felt, mineral wool, eiderdown and other loosely woven ma-
terials are very efficient. Some of these materials, however,
disintegrate after a time and fall to the bottom of the pipe,
leaving the upper part of the ripe comparatively free. Many
patented coverings have good insulating qualities as well as
permanency. Most patented coverings are one inch in thick-
ness and may or may not fit closely to the pipe. A good ar-
rangement is to select a covering one size larger than the
pipe and set this off from the pipe by spacer rings. This
air space between the pipe and the patented covering is a
good insulator itself. Table 45, Appendix, gives the
results of a series of experiments on pipe covering, obtained
at Cornell University under the direction of Professor Car-
penter. These values are probably as nearly standard as
may be had. (See Art. 138 for conduits.)
HOT WATER AND STEAM HEATING
133
89. Water Hammer: — <When steam is admitted to a cold
pipe, or to a pipe that is full of water, it is suddenly con-
densed and causes a sharp craclcing noise. The concussion
produced by this condensation may become so severe as to
crack the fittings and open up the joints. The noise is due to
a sudden rush of water in an endeavor to fill the vacuum
produced by the condensed steam. Steam at atmospheric
pressure occupies 1644 times the volume of the water that
formed it, hence, by suddenly condensing- it, a very high
vacuum may be produced. This action causes a relatively
high velocity in any body of water adjacent to it. The
worst condition is found when a quantity of steam enters
a pipe filled with water. Condensation suddenly takes place
and the two bodies of water come together with high ve-
locity causing severe concussion. Steam should always be
admitted to a cold pipe, or to one filled with water, very
slowly.
90. Returning' tbe Water of Condensation, In a Lotv
Pressure Steam Heating System, to the Boiler; — In re-
Fig. 68.
Fig, 69,
turning the water of condensation to the boiler four methods
are in use; gravity, steam traps, steam loops and steam or
electric pumps. The gravity system is the simplest and is used
in all cases where the radiation is above the level of the
boiler and where the boiler pressure is used in the mains.
In a gravity return, no special valves or fittings are neces-
sary, but a free path with the least amount of friction in It
is provided between the radiators and a point on the boiler
below the water line. No traps of any kind should ^be
placed in this return circuit.
All radiation should be placed at least 18 inches above
the water line of the boiler to insure that the water will
not back up in the return line and flood the lower radiators.
134 HEATING AND VENTILATION
This flooding- is usually the result of a restricted steam main.
When the radiation is below the water line, or wiiere tlie
pressure in the mains is less than that in the boiler, some
form of steam-trap or motor pump must be put in with special
provision for returning this water to the boiler. Two kinds
of traps may be had, low pressure and high pressure. The
first is well represented by the bucket trap, Fig. 68, and the
second, by the Bundy trap. Fig. 69. The action of these traps
is as follows. Bucket trap. — Water enters at D and collects
around the bucket, which is buoyed up against the valve.
The water collects and overflows the bucket until the com-
bined weight of the water and bucket overbalances the
buoyancy of the water. The bucket then drops and the
steam pressure upon the Inside, acting upon the surface of
the water, forces it out through the valve and central stem"
to the outlet B. When a certain amount of this water has
been ejected, the bucket again rises and closes the valve.
This action is continuous. Bundy trap. — Water enters at D
through the central stem and collects in the bowl A, which
is held in its upper position by a balanced weight. When
the water collects in the bowl suflficiently to lift the weight,
the bowl drops, the valve E opens, and steam is admitted
to the bowl, thus forcing the water out through the curved
pipe and the valve E. This action is continuous.
Each trap is capable of lifting the water approximately
2.4 feet for each pound of differential pressure. Thus, for a
pressure of 5 pounds gage within the boiler and 2 pounds
gage on the return, the water may be lifted 7 feet above
the trap, or say, to the top of an ordinary boiler. This is not
sufficient, however, to admit the water into the boiler
against the pressure of the steam. A receiver should be
placed here to catch the water from the separating trap
and deliver it to a second trap above the boiler which. In
turn, feeds the boiler. Live steam is piped from the boiler
to each trap, but the steam supply to the lower trap is
throttled, to give only enough pressure to lift the water
into the receiver. A system connected up in this way is
shown in Fig 70. Traps which receive the water of con-
densation for the purpose of feeding the boiler are called
return traps and sometimes work under a higher pressure
of steam than the separating traps. Many different kinds
of traps are in general use but these will illustrate the
principle of returning the condensation to the boiler.
HOT WATER AND STEAM HEATING-
135
VtNTPiPE TO ASH FIT
Fig-. 70.
A very simple arrange-
ment, and yet a very difficult
one to operate satisfactorily,
is by the use of the steam loop.
Fig. 71. The water of con-
densation from the radiators
drains to the receiver A,
which is in direct communi-
cation with the riser B. The
drop leg D, being in com-
munication with the boiler
through a' check valve which
opens toward the boiler at
the lowest point, is filled
with water to the point X,
.sufficiently high above the
water line of the boiler that
the static head balances the differential pressure between the
steam in the boiler and that in the condenser. The horizon-
tal run of pipe C serves as a condenser and, in producing a
partial vacuum, lifts the water from the receiver. This
water is not lifted as a solid body, but as s-'ugs of water
interspersed with quantities of steam and vapor The water
in A is at or near the boiling point and the reduced pressure
in B reevapOrates a portion of it which, in rising a? a
vapor, assists in carrying the rest of the water over the
goose-neck. When the condensation in D rises above the
point X, the static pressure overbalances the differential
steam pressure, and water is fed to the boiler through the
check.
To find the location of the point X, above the water line
in the boiler, the following will illustrate. Let the pres-
sures in the boiler, condenser and receiver be respectively
5, 2 and 4 pounds gage, then the differential pressure between
the boiler and condenser is 3 pounds per square inch. If the
weight of one cubic foot of water at 212 degrees is 59.76
pounds, then the pressure is .42 pounds per square inch for
each foot in height. Stated in other words, one pound dif-
ferential pressure will sustain 2.4 feet of water. With a
pressure difference of 3 pounds, this gives 3 -r- .42 = 7.2
feet from the water level in the boiler to the point X, not
taking into account the friction of the piping and check
which would vary from 10 to 30 per cent. Assuming this
136
HEATING AND VENTILATION
friction to be 20 per cent, we have 7.2 ^ .80 = 9 feet of head
to produce motion of the water.
The length of the riser pipe B and its diameter, depend
upon the differential pressure between the condenser and
the receiver, and upon the rapidity of condensation In the
horizontal.
With a differential pressure of 2 pounds this would sus-
pend 2 X 2.4 = 4.8 feet of solid water. The specific gravity,
however, of the mixture in this pipe Is much less than that
of solid water. For the sake of argument let this specific
gravity be 20 per cent, of that of solid water, then we would
Fig. 71.
have a possible lift, not including friction, of 5 X 4.8 = 24
feet. This is 24 — 9 = 15 feet below the water level in the
boiler. The diameter of the riser may vary for different
plants, but for any given plant the range of diameters Is
very limited. These, as has been stated, are usually found
by experiment.
A drain cock should be placed in the receiver at the
lowest point. When cold water has collected In the re-
ceiver It Is necessary to drain this water to the sewer before
the loop will work. An air valve should be placed at the top
of the goose-neck to draw off the air. If the horizontal pipe
Is filled with air, there will be no condensation and the loop
will refuse to work. Nover connect a steam loop to a boiler
HOT WATER AND STEAM HEATING
137
in connection with a pump or any other boiler feeder. To
determine whether a loop is working or not, place the hand
on the horizontal pipe. If this is cold it is not working.
The last method mentioned for feeding condensation to
the boiler was by the use of a steam or electric pump. The
operation of the steam pump is fully discussed in Art. 92.
An electric motor-pump with its receiver and pipe connec-
tions is shown in Fig. 72. Its operation is very similar to
that of the steam pump. When the returning condensation
Fig. 72.
fills the receiver to a certain point a float regulator starts
the motor and pumps the water from the receiver to the
boiler. When the water level drops the operation is re-
versed and the pump is automatically stopped. The motor
pump is used especially on low pressure heating systems
where the water of condensation from the coils and radia-
tors drains below the boiler. If the boiler pressure were
high then the ordinary steam pump would be used. Where
the pressure wtthin the boiler, however, is near that in the
return main the operation of such a piece of apparatus is
less expensive than that of the steam pump.
91. Sugr^estions for Operating Hot W^ater Heaters and
Steam Boilers: — Before firing up in the morning, examine
the pressure gage to see if the system is full of water. If
there be any doubt, inspect the water level in the expan-
sion tank. If it is a steam system, examine the gage glass
and try the cocks to see if there is sufficient water in the
boiler.
138 HEATING AND VENTILATION
See that all valves on the water lines are open. On the
steam system try the safety valve to make sure that it Is
free. Also see If the pressure ga.ge stands at zero.
Clean the fire and sprinkle over it a small amount of
fresh coal.
Open up the drafts and when the fire Is burning well
fill up with coal.
In starting a fire under a cold boiler it should not be
forced, but should warm up gradually.
Hard coal may be thrown evenly over the fire. Soft coal
should be banked in front on the grate, until the gases are
driven off. It is then distributed back over the fire.
The thickness of the fire will vary from four inches to
one foot depending upon the draft and the kind of coal.
Clean the fire when it has burned low, partially closing
the drafts while cleaning.
In a boiler or heater, using the water over continuously,
there will be little need of cleaning out the inside. In a
system using fresh water continuously, however, the boiler
should be blown off and cleaned about once or twice a month.
Never blow off a boiler while hot or under heavy pressure.
In every system the heater or boiler should be thoroughly
overhauled and cleaned before firing up in the fall.
Keep the ash pit clean and protect the grates from burn-
ing out.
Keep the tubes and gas passages clean and free from soot.
Inspect the pressure gage, glass gage, water cocks and
thermometers frequently.
In case of low water in a steam system, cover the fire
with wet ashes or coal and close all the drafts. Do not
open the safety valve. Do not feed water to the boiler. Do
not draw the fire. Keep the conditions such as to avoid any
sudden shock. After the steam pressure has dropped, draw
the fire.
Excessive pressure may be caused by the sticking of the
safety valve in the steam system, or by the stoppage of the
water line to the expansion tank in the hot water system.
The safety valve should never be allowed to lime up, and the
expansion tank should always be open to the heater and to
the overflow.
When leaving the fires for the night, push them to the
rear of the grate and bank them as stated In Art. 59.
HOT WATER AND STEAM HEATING 139
References on Hot Water and Steam.
Technical Books.
Snow, Principles of Heat., Chap. IX, X. I. C. S., Prin. of Heat,
and Vent, p. 1185, 1091. Monroe, Steam Heat. & Tent., p. 13.
Lawler, Hot Water Heating, p. 19. Carpenter, Heat. & Vent. Bldga.,
pp. 150, 231. Thompson, House Heat, by Steam & Water, p. 15.
Hubbard, Power, Heat. & Vent., pages 433, 464, 484, 505, 510.
Technical Periodicals.
Engineering News. Suggestions for Exh'st Steam Heat,
Apr. 7, 1904, p. 332, An Improved Steam Heat. System, Ther-
mograde System, July 23, 1903, p. 80. Factory System of the
United Shoe Machinery Co., Y/. C. Snow, May 25, 1905, p. 537.
Heating a Trolley Car Barn, J. I. Brewer, April 29, 1909, p.
462. Engineering Review. Heat. & Vent, of the New Parental
Home and School at Flushing, L. I., Jan. 1910, p. 48. A Hot
Water System with Radiators and Boiler on the Same Level,
J. P. Lisk, Aug. 1908, p. 34. A Hot Water Heat. System for
a City Residence, J. P. Lisk, June 1909, p. 44. Hot Water
Heat. Apparatus in Plymouth Church, Brooklyn, N. Y., Dec.
1908, p. 19. Heat., Vent, and Temperature Regulation in the
Measles Pavilion of the Kingston Ave. Hospital, Brooklyn,
N. Y., Jan. 1910, p. 35. Heat, and Vent. Plant of the Boston
Safe Deposit and Trust Company's Building, C. L. Hubbard,
April 1910, p. 37. Heat, and Vent. Installation in the Burnet
St. School, Newark, N. J., Jan. 1909, p. 20. A Unique Low
Pressure Steam Heat. Apparatus, Feb. 1909, p. 38. Practical
Points on Steam Heating (Direct Heating), C. L. Hubbard,
Aug. 1908, p. 29. (Indirect Heat.), Sept. 1908, p. 19. (Exhaust
Steam Heat.), Nov. 1908, p. 21. Steam Heating Systems,
Wm. J. Baldwin, March 1905, p. 7. Machinery. Shop Heating
by Direct Radiation, C. L. Hubbard, July 1910, p. 884. Sizes
of Pipe Mains for Hot Water Heating, C. L. Hubbard, Sept.
1909, p. 38. The Railway Review. Heating System of the Scran-
ton St. Railway Shops, June 13, 1908, p. 480. Heating of
Passenger Trains, May 23, 1908, p. 408. The Pennsylvania
R. R. System of Heat, and Vent. Passenger Cars, Feb. 22, 1908,
p. 157. Vent, and Heating of Coaches and Sleeping Cars,
July 18, 1908, p. 586. Hot Water Heating Arrangements for
Passenger Stations, Oct. 10, 1908, p. 829. Typical Heating
Plants, Horace L. Wiinslow Co., June 18, 1910, p. 596. The
Heating & Ventilating Magazine. Residence Heating by Direct
and Indirect Hot Water, July 1905, p. 25. Carrying Capac-
ities of Pipes in Low Pressure Steam Heating, Wm. Kent,
Feb. 1907, p. 7. Standard Sizes of Steam Pipes, Jas. A. Don-
nelly, Jan. 1907, p. 21. Formula for Pipe Sizes in Hot Water
Heating, Oliver H. Schlemmer, Sept. 1907, p. 9. Coefficient
of Transmission in Cast Iron Radiation, John R. Allen, Aug.
1908, p. 20. Relative Capacities of Pipes, John Jaeger, May
1907, p. 1. Methods of Figuring Radiation. Gerard W. Stan-
ton, Dec. 1907. p. 1. Computation of Radiating Surface, J.
Byers Holibrook, Nov. 1904. p. 77. Coefficients of Heat Trans-
mission, John R. Allen, July 1911. Domestic Engineering. A
Practical Manual of Steam and Hot Water Heating, JE. R.
Pierce, (Series of Articles), Vol. 51, No. 2, April 9, 1910; Vol.
53, No. 9, Nov. 26. 1910. Proportions and Power of Low
Pressure Heating Boilers, Vol. 47, No. 11, June 12, 1909, p.
319. How to InstaJll and Cover a Steam or Hot Water Main,
"Phoenix," Vol. 46, No. 10, March 6, 1909, p. 278. How to
140 HEATING AND VENTILATION
Secure Correct Pipe Sizes for Low Pressure Steam Heating,
E. K. Monroe, Vol. 45, No. 9, Nov. 28, 1908, p. 243. Rules for
Proportioning- Indirect Heating Plants, R. T. Crane, Vol, 49,
No. 6, Nov. 6, 1909, p. 143. Tratts. A. S. H. d V. E. Circulation
of Hot Water, J. S. Brennan, Vol. XI, p. 93. Residence Heat-
ing" by Direct and Indirect Hot Water, E. F. Capron, Vol.
XI, p. 174. Standard Sizes of Steam Mains, J. A. Donnelly,
Vol. XIII, p. 43. The Carrying Capacity of Pipes in Low
Pressure Steam Heating-. Wm. Kent, Vol. XIII, p. 54. Heat-
ing and Ventilating- a Group of Public Schools, S. R. Lewis,
Vol. XIII, p. 187. The Combined Pressure and Vacuum Sys-
tems of Steam Heating-. G. Hoffman, Vol. XIII, p. 223. Sizes
of Return Pipes in Steam Heating Apparatus, J. A. Donnelly,
Vol. XII, p. 109. Proportioning Hot Water Radiation In
Combination Systems of Hot Water and Hot Air Heating,
R. C. Carpenter, Vol. VII, p. 132. Tests of Radiators with
Superheated Steam, R. C. Carpenter, Vol. VII, p. 206. Rela-
tive Economy of Steam, Vapor, Vacuum and Hot Water
Heating for Residences, Vol. XII, p. 341. The Relation be-
tween the Completeness of Air Removal and the EfTiciency
of Steam Radiators, Vol. XII, p. 315. Measurements of Wall,
Radiators, Vol. XII, p. 361. Advantages of Standard Dimen-"
sions of Radiator Valves and Connections, Vol. XIII, p. 145.
The Relative Healthfulness of Direct and Indirect Heat-
ing Systems, Vol. XIII, p. 136. Improving the Heating
Capacity of a Radiator by an Electric Fan, Vol. VIII, p. 222.
Engineering Record. Mechanical Plant of the Harvard
Medical School, No. 2, Aug, 7, 1909. Mechanical Equipment
of the Hotel LaSalle, Chicago, Sept. 11. 1909. Mechanical
Plant of the Washington Municipal Bldg., Oct. 30, 1909.
Heating and Ventilation of the Museum of Fine Arts, Bos-
ton, Nov. 13, 1909. Heating Plant for a Railway Storehouse,
Dec. 18, 1909. Heating and Ventilation of the Hotel Plaza,
N. Y,, Mar. 13 and Mar. 20, 1909. Central Heating and
Lighting Plant for the United States Military Academy, May
1, May 8 and May 15, 1900. Electric Railway Journal. Heating
System In Car House of Toronto & York Radial Rail-
way, March 26, 1910, p. 543. The Elevated Shops and Ter-
minals of the Brooklyn Rapid Transit Co, — Organization and
General Layout at East New York, Feb, 2, 1907, p, 170. The
Elevated Shops and Terminals of the Brookilyn Rapid Tran-
sit Co, — The Thirty-sixth St, Inspection Plant, March 9. 1907,
p. 406. The Metal Worker. Unstable Water Lines In Steam
Boilers. March 26. 1910. p. 429. Air Venting Hot Water Sys-
tems, June 4, 1910, p. 755, Heating Swimming Pool. June 25,
1910, p, 854. Air Venting Steam Systems, July 9. 1910, p. 30
Heating- and Ventilating Six Room School Building-, Oct. 23
1909, p, 45. Steam Heating In a Cottage, July 11, 1908, p.
45. Indirect Hot Water Heating in Residence. Oct. 24, 1908,
p. 43. Hot Water Heating In a Factory In Hoboken. N. J.,
April 4, 1908, p. 39. Poirrr. Economics of Hot Water Heating,
Ira N. Evans, Sept. 12, 1911. Hot Water Heating for Institu-
tions. Ira N. Evans, May 14, 1912. Forced Circulation In Hot
Walter Heating, Clmrles L. Hubbard, Dec. 20, 1912; Nov. 15,
1912.
CHAPTER IX.
MECHANICAL VACUU3I, STEAM HEATING SYSTEMS.
92. In Addition to the Brief Discussion of vacuum steam
heating as found in Art. 69, it will be well to discuss
more in detail the various systems by which this heating is
accomplished. The advantages to be derived by the positive
withdrawal of the air and the condensation from the radi-
ators and pipes, compared to the natural circulation of the
gravity system, are now too well established to need much
discussion. Mains and returns that are too small, horizontal
runs of piping that are unevenly laid so as to form air and
water pockets, radiators that are only partially heated be-
cause of the entrapped air, leaking air and radiator valves,
radiators partially filled with condensation and all the accom-
panying cracking and pounding throughout many of
the gravity systems, are sufficient causes to de-
mand a cure, if such cure can be found. One should not
understand by this statement that every mechanical vacuum
system is a cure for all the ills in the heating w^ork, for even
these systems may be improperly designed. The steam pipes
may be too small to supply the radiators, although smaller
pipes may be used in this than in the gravity work, the
valves may be defective, or the vacuum specialties may be
inefficient. Most of the defects in the average plant, however,
are because of imperfections in that "part of the system
from the radiator to the boiler, and all of the first class
vacuum systems are planned to meet just these conditions.
Vacuum systems have other advantages over the gravity
work, the principal one being that of lifting the return con-
densation to a higher level. This is noticeable in the plac-
ing of radiators or coils in basement rooms. Another very
important advantage is in the laying out of the heating coils
for shop buildings and manufacturing plants. Low pres-
sure gravity coils are limited to a length of about 75 feet.
Usually the condensation .in a long coil of this kind is very
great and requires extra heavy pressure on the steam end
to circulate it. The steam follows the line of least resistance
142
HEATING AND VENTILATION
and forces the air out of certain pipes and permits It to re-
main in others, the differential pressure not being great
enough to eliminate all the air and heat the pipes uniformly.
As a result of these conditions some of the pipes remain
cold and ineffective as prime radiating surface. A vacuum
system, with its positive circulation, increases the differ-
ential pressure, removes the air and gives uniform heating
effect in coils that are several times as long as can be
safely supplied by the gravity system. The accumulation of
air in the radiators and coils is especially noticeable in
systems using exhaust steam.
When exhaust steam from engines or turbines is used
in a gravity heating system, the back pressure is carried
from atmospheric pressure to 10 pounds gage. With the ap-.
plication of the vacuum system it is possible to maintain
this constantly at about atmospheric pressure. It is
claimed by some, that it is possible to reduce the pressure
in the radiators to such a degree that the pressure in the
supply mains vi^ill fall considerably below atmosphere. No
doubt the specialty valves may be set so as to do this, but
it would scarcely be considered an economical arrangement.
BACK PRESSURE
VALVE
V^CR
Wfit
• — i |C0K)ErfiCR|
Z(fN. PUMPCD=^^
Fig. 73.
MECHANICAL VACUUM HEATING 143
The principal features of a mechanical vacuum system
are shown in Fig". 73. Live steam is conducted to the engine
and to the heating main, the latter through a pressure re-
ducing valve to be used only when exhaust steam is insuf-
ficient. The exhaust steam from the engines and pumps
is conducted to the heating' main and to the feed water
heater. The exhaust steam line opens to the atmosphere
through a back pressure valve which is set at the desired
pressure for the supply steam. An oil separator shown on
the exhaust steam line removes the oil and delivers it to an
oil trap. At the entrance to the feed water heater, the
exhaust steam passes through a series of baffle plates which
remove the oil and entrained water from that part of the
steam which enters the heater. A boiler feed pump and a
vacuum pump, with the attending valves and g'overning ap-
pliances, complete the power room equipment. The steam
supply to the heating system is piped to radiators and coils
in the ordinary way, w^ith or without temperature control.
A thermostatic valve, or patented motor valve, is placed at
the return end of each radiator and coil and these returns
are then brought together in a common return which leads
to a vacuum pump or ejector. The return pipe and specialty
valve for any one unit is usually i/^ inch. The combined re-
turn increases in size as more radiation is taken on. Hori-
zontal steam mains usually terminate in a drop leg w'hiclh is
tapped to the return 8 to 15 inches above the bottom of the
leg. Each rise in the system has a drop leg at the lower
end of the rise. These points and all -other points where
condensation may collect are drained through specialty
valves to the return. "Water supply systems may be tapped
for steam and return condensation the same as any ordi-
nary radiator. Steam is carried in the main at about at-
mospheric pressure, and just enough vacuum is maintained
on the return to insure positive and noiseless circulation.
In many cases where special lifts are required, these return
systems are run under a negative pressure of 6 to 10 inches
of mercury. Under such conditions water may be lifted
fro(m! 6 to 10 feet. Either clo^sed or opened feed water
heaters may be used w^ith the layout as given. (For com-
parative sizes of gravity and vacuum returns see Table 38,
Appendix.)
Fig. 74 shows a section through the Marsh vacuum pump
which represents a type very generally used dn this work.
144
HEATING AND VENTILATION
Fig. 74.
It will be noticed that this pump has a steam operated valve.
The automatic governing feature of this valve tends . to
equalize the cylinder
fi pressure to meet the
varying resistance in
the main return of the
heating system. Such
a pump is handling al-
ternately solid water
and vapors, hence
there is great tenden-
cy of the ordinary
pump to race and
pound at such times.
In its operation the
steam enters at A and
passes into the space
B through the annu-
lar opening C be-
tween the reduced
neck of the valve and
the bore of the first chest wall. It is thus projected against
the inside surface of the valve head before entering into
the port and passing to the cylinder. On reaching the
cylinder and driving the piston to the right, the reaction of
the steam through port D to the opposite side of the valve
head, tends to further open the steam port C. The valve
then holds a position depending upon the relative strength
of the forces which tend to move it in opposite directions,
i. e., admission steam which tends to close the valve, and the
cylinder steam which tends to open the valve. This is
the governing feature. It will be noticed that the pump
piston is in two parts and carries steam at admission pres-
sure upon the inside. This steam is admitted along the
dotted line to the center of the cylinder head, thence through
a sm>all tube and packing box to the liollow piston rod,
w>hich has a direct connection with the center of the piston.
When the piston has moved suffi'ciently to bring the central
space E in line with the duct D, steam is admitted to the
right of the piston valve thus forcing it back, cutting off
the steam at C, opening up the exhaust to the atmosphere
through F and -admitting steam to the other end of the
cylinder. The action Is thus reversed and continuous. Ejec-
MECHANICAL VACUUM HEATING
145
tors operated by steam, water and electricity are also used
to produce a vacuum. No comparison is made here of t'he
various systems of producing vacuum since each gives satis-
faction when properly installed. In each case there is a
loss of energy but this loss is amply repaid in the added
benefits.
Several patented systems of mechanical vacuum heating
are now upon the market. These are in large measure an
outgrowth of the original Williames System, patented in
1882. Each system is well represented by the above diagram
in all particulars concerning the steam and water circu-
lation. The chief difference between them is in the thermo-
static or motor connection at the entrance to each individual
return.
93. Webster System: — In this system a pump is used to
produce the vacuuinr. A special fitting, called a water-seal
motor, or thermostatic valve, is used on all radiators, coils and
drainage points. Fig. 75 shows a section of one of the motor
valves. Other models are constructed so as to have the out-
let in a horizontal direction, either parallel with or 90 de-
grees to the inlet. Fig. 76 shows an application of this to a
radiator or coil. The dirt strainer is usually placed between
the radiator or coil and the motor valve. This strainer
Fig. 75.
DIRT 5traine:r
CONNECT INTO
TOP OF RETURN
Fig. 76.
collects the dirt and protects from clogging the motor valve.
C attaches to the return end of the radiator or coil and L
leads to the vacuum pumip. O is the central tube, the lower
end of which is a valve. A is a hollow cylindrical copper
float, the central tube of which fits loosely over spind'le B.
146
HEATING AND VENTILATION
The function of the cylinder A Is to raise the tube O from
the seat H and open the discharge to the pump. Ordinarily,
the float is down and the central tube valve is resting upon
the seat and cuts ofC communication with the radiator, ex-
cepting as air may be drawn from the radiator down the
central tube around the spiral plug. The water of conden-
sation accumulating in the radiator or coil passes into the
chamber E, sealing- the valve, and when sufficient water has
accumulated to lift the float, it opens a passageway for a
certain amount of the water to be withdrawn to the return.
"When this water becomes lowered sufficiently, the valve
again seats itself and the cycle is completed. This action
continues as long as water is present in the radiator. These
motor valves are made of three sizes, Vz inch, % inch and 1
inch. The first is the standard size and has a capacity of
approximately 200 feet of radiation.
Fig, 77 shows thermostatic valves. It will be seen that
the automatic feature in a is the compound rubber stalk,
which expands and contracts under heat and cold. The
Fig. 77.
adjusting screw at the top permits the valve to be set for
any conditions of temperature and pressure within the radi-
ator. The water of condensation passes through a screen
and comes in contact with the rubber stalk. The tempera-
ture of the water being less than that of steam the stalk
contracts and the water is drawn through the opening A by
the action of the pump. As soon as the water has been re-
MECHANICAL VACUUM HEATING
147
moved, steam flows around the stalk and expands until it
closes the seat. This process is a continuous one and auto-
matically removes the water from the radiator. The screen
serves the purpose of the dirt strainer as mentioned above.
Fig. 77, 6, shows a sylphon arrangement where the movement
of the valve is obtained by the expansion and contraction of
the fluid inside* the bellows. -^
A suction strainer, which is very similar to the dirt strain-
er only larger in capacity, is placed upon the return line
next the pump. This fitting usually has a cold water con-
nection to be used at times to assist in producing a more
perfect vacuum. The piping system for the automatic con-
trol of the vacuum] pump is shown in Fig. 78. It will be
seen that the vacuum in the re-
turn operates through the gover-
nor to regulate the steam supply
to the pump cylinder, thus con-
trolling the speed of the pump.
Occasionally it is desirable to
have certain parts of the heating
system under a different vacuum.
An Illustration of this would be
where the radiators within the
building were run under a neg-
ative pressure of about one
pound, and a set of heating coils
in the basement were to be carried under a negative pressure
of four pounds. The Web-
ster System, type D, Fig.
79, imeets this condition.
The exact difference be-
tween the suction pressure
and the pressure in the
radiators can be varied to
suit any condition by the
controller valve. A trap
and a controller valve
should be applied to each
line having a different
VACUUM PUMP'
Fig. 78.
HIGH \ACUUM
Lt=3
> Fig. 79.
pressure from that in the suction line.
A modulation valve, foY graduating the steam supply to the
radiator, has been designed by this Company and may
be applied to any Weibster Heating System to assist in its
148
HEATING AND VENTILATION
regulation. This modulation valve serves to graduate the
steam supply to the radiators so that the pressure may be
maintained at any point to suit the required heat loss from
the building.
94. Van Auken System: — In this system, as in the pre-
vious one, the vacuum in the return main is produced by a
vacuum pump wlhich is controlled by a specially designed
governor. The automatic valves which are placed on the
radiators, coils and other drainage points along the system,
are called Belvac Thennofiers, and are shown in section by
Fig. 80. This valve is automatic and removes the water of
condensation by the controlling ac-
tion of a float. It is connected to the
radiator or coil at fi^ and to the vacu-
um return pipe at L. The water of
condensation is drawn through the
.f^ return pipe into chamber D until it
reaches the inverted weir E which
gives it a water seal. It 1^ thence
drawn upward into space D until it
overflows into the float chamber AA,
where it accumulates until the line
of flotation is reached. When the
float C lifts, the valve seat at B
opens and allows the water to es-
cape into the vacuum return pipe.
After the removal of the water the float again settles on seat
B until sufficient water accumulates in the float chamber to
again lift it, when the cycle is repeated.
The air contained in the radiators or coils is drawn
through the return and up through chamber D into the top
of the float chamber. Here its direction follows arrows OO,
being drawn through the small opening in the guide-pin at
F, down through the hollow body of the copper float and
valve seat B, into the vacuum return. This removal of air la
continuous regardless of the amount of water present. The
by-pass /, when open, allows all dirt, coarse sand or scale
to pass directly into the vacuum return, thus cleaning the
valve. By opening the by-pass I only part way, the con-
tents of chamber A may be emptied into the vacuum return
without interfering with the conditions in space D. The
ends of the float are symmetrical, hence it will work either
w^y. The thermoflers are made In four standard sizes of
Fig. 80.
MECHANICAL VACUUM HEATING
149
outlets, two having- V2 incli and two having % inch outlets.
These valves have capacities of 125, 300, 550 and 1200 square
feet of radiation respectively.
Drop legs, strainers, governors and other specialties
usually provided by such companies are supplied in addition
to the thermofiers. When a differential vacuum is to be ob-
tained a special arrangement of the piping system is planned
to cover this point. The piping- connections around the auto-
m.atic pump g-overnor are the same as are shown in Fig-. 78.
95. Automatic Vacuum System; — In this system the
automatic vacuum valve, which takes the .place of the motor
valve and thermofier in the two preceding systems, is shown
in Fig-. 81. K is the entrance to the radiator and L to the
vacuum return. Screen F
prevents scale and dirt
from entering- the valve.
By-pass E is for emerg-
ency use in draining ofC
accumulated water and
dirt, should the valve
clog-. With such an ad-
justment the bonnet of
the valve inay be re-
moved for inspection
without overflowing-. Be-
fore the steam is turned
on in the radiator the float is tipped, as shown in the figure,
making a small wedge shaped opening- through which the
vacuum can pull on the radiator. When steam is admitted
to the radiator, condensation flows into the valve, lifting
the float and sealing the outlet against the passage of
steaimi As the valve continues to fill with water the float
is lifted, and water passes
to the vacuum return. As
the water is drawn ofC the
float falls and reseats on
the nipple when about V2
inch of water remains in
the valve, thus maintaining
the water seal. Fig. 82
shows the piping connec-
tions around 'the automatic
pump governor. It will be
Fig. 82. seen that this connection
150 HEATING AND VENTILATION
differs from those of the Webster and VanAuken Systems,
in that the pressure in the return main controls the flow
of injection water into the suction strainer.
96. Dunhnm System: — The special valve used upon the
returns from radiators, coils and drainage points in the
Dunham System is shown in Fig. 83. The chamber between
the two corrugated disks AA is filled with a liquid which
vaporizes at low temperatures. The adjustment is so made
that the tem^perature of the steam creates pressure enough
between the disks to close the valve and cut off drainage
to the vacuum pump. "When
water collects under the disks
the temperatui*e of the water
| rad is sufl[iciently cooled below
that of the steam to condense
some of the liquid, reduce the
socTiofsi pressure and open up the valve.
Fig. 83. . . ,
The action is therefore auto-
matic and controlled entirely by the temperature of the
water or steam in contact with the disks. In other re-
spects this system is very similar to those previously de-
scribed.
97. Paul System: — Referring to Art. 69 it will be seen
that the Paul System is essentially a one-pipe system, with
the vacuum principle attached to the air valve. Its use is
not restricted to the one-pipe radiator, since it may be ap-
plied to the two-pipe radiator as well. The advantage to
be gained, however, when applied to the former, is much
greater than in the latter because of the greater possibility
of air clogg'ing the one-pipe radiator. This one fact has
largely determined its field of op'eration. This system dif-
fers from the ones just mentioned in two essential points;
first, the vacuum effect is applied at the air valve and the
water of condensation is not moved by this means; second,
the vacuum effect is produced by the aspirator principle
using water, steam or compressed air, as against the pumps
used by the other companies. The same principle may also
be applied to the tank receiving the condensation. By this
means it is possible to remove all the air in the system and
to produce a partial vacuum if necessary. Ordinarily the
vacuum is supposed to extend only as far as the air valve
S/t the radiator. If desired, however, this valve may be ad-
MECHANICAL VACUUM HEATING
151
justed so that the vacuum effect may be felt within the radi-
ator, and in some cases may extend into the supply main.
Many modifications of the Paul System are being- used. In its
latest development, the layout of the system for large plants.
I AlP VALVE
AIR VALVE
STEAM IMLET
TO RECE IVER
OR RETURN
Fig. 84.
//////////////////Tm f.
TOArnoSPHERE
DRAIN
Is about the same as that shown in Fig. 73, where all of the
principal pieces of apparatus that go to make up the power
room equipment are present. Fig. 84 shows a typdcal vacu-
um connection between one-pipe and two-pipe radiators and
the exhauster. This diagram shows the discharge leading
to a tank, sewer or catch basin. If exhaust steam were
used, the discharge would probably lead into the steam
supply to one or more of the radiators and then into the
atmiosphere. Where electric current can be had this ex-
hausting may be done by the use of an electric motor. A
specially designed thermostatic air valve is supplied by the
Company to be used on this system.
Other vacuum systems, each having a full line of specialty
appliances, might be mentioned here but the above are con-
sidered sufficient.
152
HEATING AND VENTILATION
REFERENCES.
RefereneeN on MeehanionI Vneuum Heating.
Technical Books.
Snow, Priuri]th's of Heating, Chap. XL. Carpenter, Ilcatinrj d
Tentilatinfi liuiUUngs, p. 285. Hubbard, Power, Ueatinij & Yentiln-
tion, p. 568.
Technical Periodicals.
Engineering Review. Steam Heating Installation In the
Biology and Geology Building and the Vivarium Building,
Princeton University (Webster System), Jan. 1910, p. 27.
Steam Heating and Ventilating Plant Required for Addition
to Hotel Astor (Paul System), March 1910, p. 27. Heating
Four Store Buildings at Salina, Kans., (Moline System, Vacu-
um Vapor), April 1910. p. 45. Steam Heating System for
Henry Doherty's Mill, Paterson, N. J., May 1910, p. 37. Heat-
ing Residences at Fairfield, Conn., (Bromell's System of
Vapor Heating), June 1910, p. 52. Heating Residence at
Flemington, N. J., (Vapor-Vacuum System), July 1910, p. 43.
Heating System Installed in the Haynes Office Building,
Boston, (Webster Modulation System), Aug. 1910, p. 44.
Heating the Silversmith's Building, New York, (Thermo-
grade System), Jan. 1908, p. 8. Heating System in the New
Factorv of Jenkins' Bros., Ltd., Montreal. Canada, (Positive
Differential System). Dec. 1907, p. 14. The Railway Review.
Vacuum Ventilation for Street Cars, Oct. 23, 1909, p. 948.
The Metal Worker. A Vapor Vacuum Heating System, April 4,
1910, p. 494. Heating Church by Vacuum System, Sept. 11,
1909. p. 46. Rehabilitation bv Vacuum Heating, Jan. 21, 1911.
Potter. Combined Vacuum and Gravity Return Heating Sys-
tem, Charles A. Fuller, Aug. 11. 1911. Vacuo Hot Water
Heating, Ira N. Evans, Mar. 12, 1912. Heat, d Vent. Magazine.
Vacuum Heating Practice, J. M. Robb, Jan. 1912.
CHAPTER X.
MECHANICAL. WARM AIR HEATING AND
VENTILATION. FAN COIL SYSTEMS.
DESCRIPTION OF SYSTEMS AND APPARATUS EMPLOYED.
98. Fire-places, Stoves, Furnaces and Direct Radiation
Systems of both steam and hot water have, individually,
advantages and disadvantages, but, in common, all lack
what is increasingly being considered as of more import-
ance than heating, namely, positive ventilation. Merely to
heat a poorly ventilated apartment only serves to increase
the discomfort of the occupants, and modern legislative
bodies are reflecting the opinion of the times by the passage
of compulsory ventilation laws affecting buildings with
numerous occupants, such as factories, barracks, school
houses, hotels and auditoriums. To meet this demand for
the positive ventilation of such classes of buildings, there
has been developed what is variously known as the hot blast
heating system, plenum system, fan Mast system or mechanical warm
air system.
99. Elements of tlie Meclianical Warm Air System:^
Known by whatever name, this system contemplates the
use of three distinctly vital elements; first, some form of
hot metallic surface over which the forced air may pass
and be heated; second, a blower or fan of some description
to propel the air; and third, a proper arrangement of ducta
or passageways to distribute this heated air to desired
locations. Figs. 96 and 97 show these essentials, fan,
heating coils and ducts in their relative positions with con-
nections as found in a typical plant of this system. Many
attachments and improved mechanisms may be had to-day
in connection with this system, such as air washers and
humidifiers, automatic damper control systems, and brine
cooling systems whereby the heating coils may be used
as cooling coils, and, during hot weather, be made to
maintain the temperature within the building from 10 de-
grees to 15 degrees lower than the atmosphere. None of
these auxiliaries, however, change in any way the necessity
154
HEATING AND VENTILATION
for the three fundamentals named and their general ar-
rangement as shown.
100. Variations In the DcNii^n of Meflianloal Warm Air
Systems: — With regard to the position of the fan, two meth-
ods of installing the system are common. The first and
most used is that shown in Fig. 85, a, where the fan Is in
the basement of the building and forces the air by pressure
upward through the ducts and into the rooms. This causes
the air within the entire building to be at a pressure
•a. Plenum System. b. Exhaust System.
Fig. 85.
slightly higher than the atmosphere, and hence all leak-
ages will be outward through doors and window crevices.
A system so installed is usually called a plenum syf^icm. The
fan may, however, be of the exhausting type. Fig. 85, b,
and placed in the attic with which ducts from the rooms
connect, so that the fan tends to keep the air of the build-
ing at a slight vacuum as compared with the atmosphere,
thus inducing ventilation. Air is then supposed to enter
the basement inlet, pass over the coll surface, and, when
heated, pass to the various rooms through the ducts pro-
vided. But air from the atmo.<?phere will Just as readily
leak In at windows or other crevices, as come in over the
PLENUM WARM AIR HEATING
155
heaters, and then the system will fail in its heating work.
For this reason the exhaust heating system, as it is usually
known, is seldom installed, except where aid in the prompt
removal of malodors is desired. Combined plenum and ex-
haust systems are to be recommended wherever the expense
can be justified.
101. Blowers and Fans: — Many methods of moving- air
for ventilating and heating purposes have been devised;
some positive at all times, others so dependent upon the ex-
istence of certain conditions as to be a constant source of
trouble. It is coming to be a very generally accepted fact,
that if air is to be delivered at definite times, in definite
quantities and in definite places, it must be forced there, and
not merely allowed to go under conditions readil-y changing
or disappearing. The recognition of this fact has led to a
very common use of the mechanical fan or blower for im-
pelling air, and this use has, in turn, caused the develop-
ment of fans and blowers to a fairly high degree oil
efficiency.
By the aid of mechanical apparatus, air may be moved
positively in either of two ways, by the exhaust method or
by the plenum method, each having fans developed best suited
to its needs. In the exhaust method the fan is commonly
of the disk av propeller blade type, shown in Figs. 86 and
156
HEATING AND VENTILATION
S7, ana moves the air by suction. It is usually Installed In
the attic or near the top of the building, although with a
system of return ducts it may be installed in the basement.
The plenum system uses a fan of the paddle wheel or mul-
tiple blade type, shown in Figs. 88 and 89; the first is the
standard form of fan wheel in common use, and the second
is a more recent development of the same, called the "tur-
bine" fan wheel, shown direct connected to a De Laval
steam turbine. The wheels of the fans are also shown.
Fig. 87.
Tests of the latter wheel seem to show a somewhat higher
efficiency than has heretofore been possible witli the older
forms. Both of these forms of fans are used in plenum
work, and are placed on the forcing side of the circulating
system just between the air intake and the heater coils,
or just following the heater coils, and hence produce a pres-
sure within the building or suite heated, so that leakages
are outward and not so detrimental to the good working
of the plant as in the exhaust system.
The motive power for fans may be of four kinds,
electric direct drive, steam engine or steam turbine direct
drive, and belt and pulley drive, as shown in Figs. 87, 88, 89
and 90. Which of these drives will be the most appropriate
win depend entirely upon local conditions and the nature
PLENUM WARM AIR HEATING
157
of the available power supply. The steam engine or steam
turbine drive is perhaps the most common, since some
steam must be present for the supply of the heating coils,
and since, too, the exhaust of the engine or turbine may
be used to supplement the live steam used for heating.
See Art. 122.
Fig.
Fig. 89.
Fan housings are made in many different styles, and
of various materials, the more readily to fit any given set of
conditions. Materials employed may be of brick, wood, sheet
steel or combinations of these. Steel housings are the most
common and are made in such a variety of patterns as
will fit any requirement of plenum duct direction. What
are known as full housings are those in which the entire fan
wheel is encased with steel and the entire unit is self-con-
tained and above the floor line. Three-quarter housings are
those in which only the upper three-fourths of the fan wheel
Is encased, the completion of the air-sweep around the
158
HEATING AND VENTILATION
paddles being obtained by properly forming the brick foun-
dation upon which the fan is installed. The larger fans
are commonly three-quarter housed, especially if they are
to deliver air directly into underground ducts. Fig. 88
shows a full housing and Fig. 90 a three-quarter housing.
Fig. 90. Fig. 91.
The circular opening in the housing around the shaft
of the wheel is the inlet of the fan, the air being thrown
by centrifugal force to the periphery and at the same time
given a circular motion, thus leaving the fan tangentially
through the discharge opening. Fans may be obtained which
will deliver at any angle around the circumference, and fans
may be obtained with two or more discharge openings, usu-
ally referred to as "multiple discharge fans," as shown in
Fig. 91. Some fans have double side inlets, 1. e., air enters
the fan from each side at the center. These openings are
smaller than the single side inlet. All fan casements should
be well riveted and braced wit)h angles and tee irons. The
shaft should be fitted with heavy pattern, adjustable, self-
oiling bearings, rigidly fastened to the casement and prop-
erly braced. The thickness of the steel used in the casement
varies according to the size of the fan, from No. 14 to No. 11
for sizes in general use. The fan wheel should be well con-
structed upon a heavy spider to protect against distortion
from sudden starting and stopping. The side clearance be-
tween the wheel and casement should be small. Fans should
be bolted to substantial foundations of brick or conert-tr.
When connecting them to metal ducts where any sound from
the mation of the fan may be transmitted to .the room®, the
connection should be made tlirough llexible rubber cloth
PLENUM WARM AIR HEATING
159
102. Fresh Air Entrance to Building and to Rooms:—
The air may enter through the building wall at the ground
level or it may be taken from a stack built for the pur-
pose, providing a down draft with entrance for the air
at the top. This may be done in case no washing or clean-
ing systems are applied and in case the air is heavily
charged with dust or dirt from the street. Usually in
isolated plants or in small cities, the air is taken in near
the ground level from some area-way that is fairly free
from dust. In the larger cities, however, either a washing
sj'stem is installed to cleanse the air before it is sent
around to the rooms, or the air is taken from an elevation
somewhat above the ground as spoken of before. The ve-
locity of the air should be from 700 to 1000 feet per minute
at this point and where grill work or shutters of any sort
are put in the opening, they are usually so planned as not
to seriously obstruct the flow of the air. Usually a plain
flat wire screen is placed in the opening to keep out leaves,
and doors are swung from the inside in such a way as to be
thrown open, leaving practically the full value of the open-
ing as a net area.
Air entrance to rooms is accomplished through registers
or gratings which cover the ends of rectangular ducts or
conduits called stacks, built into the brick walls and open-
ing into the respective rooms much as shown in section by
Fig. 22. Register sizes considered standard are given in
Table 17, Appendix. The velocity of the air at a plenum
register may be somewhat higher than in a simple fur-
nace installation. In the plenum system the heat reg-
isters are usually placed well above the heads of the occu-
pants, near the ceiling, and the vent registers near the
floor. Velocities allowable at registers and up stacks are
shown in Table XIII, page 172.
103, Plenum Heating Surfaces: — 'Heating surfaces as
used to-day in connection wit'h plenum systems may be
divided into two classes: coil surface, made of loops of 1 or
l^/i inch wrought iron pipe and cast surface, made of hollow
rectangular castings -provided with numerous staggered pro-
jections to increase the outside surface and provide greater
air contact. To make a heater of either kind of surface,
successive units are placed side by side, until the requisite
total area and depth have been obtained. The total number
of square feet of cast or pipe coil surface exposed to the
160
HEATING AND VENTILATION
air determines the total number of heat units given to the
air per hour, wlhile the depth of the heater controls the final
temperature of the air leaving the heater. Each of these
points must be considered in designing the heater system.
(See Arts. 118 and 119).
Pipe coils may be used
under high pressures
but cast coils should
never be used under
pressures exceeding 25
pounds per square inch
gage. All plenum heat-
ing surfaces should be
well vented and drained.
Ample allowance also
should be made for ex-
pansion and contraction.
Coil surface is of
three kinds, that hav-
ing the pipes inserted
vertically into a hori-
Fig. 92. zontal cast iron header
wthich forms the base of the section, Fig. 92, that having
the pipes horizontally between two vertical side headers,
Fig. 93, and that having one header vertical and one
header horizontal called the mitre coil. Fig. 94. The first
and last forms shown are made with two, three or four
pipes in depth. The stand-
ard number of pipes In any
one section is four. Some-
times these pipes are spaced
in straight lines parallel
with the wind and some-
times are staggered. Stag-
gered spacing no doubt
makes each pipe slightly
more efficient but it adds
friction to the air cur-
rent and power to the fan. Efficiency tests of both spac-
Ings, however, show little difference in these methods. The
horizontal sections and the mitre sections present this ad-
vantage over the vortical pipe sections, that the stoam and
condensation are always flowing In the same direction and
Fig. 93.
^
PLENUM WARM AIR HEATING
161
Fig. 95.
drainage is very simple. With
the vertical pipe section,
steam in one-half of the
pipes must pass upward
against the direction of the
flow of condensation or it must
carry the condensation with it.
That half of the header sup-
plying pipes which carry
steam upward is usually
drained for condensation by
a small hole directly into the
return with the result that
steam often blows through
the header without travers-
ing the pipe circuits. The
third, or mitre section, in ad-
dition to perfect drainage, has
perfect expansion. The ver-
tical header serves as a
steam supply and the horizon-
tal header as a drain, permit-
ting every pipe to assume any
position necessary to account
for a reasonable change of
length.
Cast iron radiating surface
for plenum systems is shown
in Fig. 95. It is composed,
primarily, of sections not un-
like the sections of an ordi-
nary direct radiator in the
way in which they are joined
together at the top and bot-
tom by nipples, thus forming
what is termed a stack. Stacks
are again assembled, one in
front of another, with respect
to the direction in which the
air passes through them, the
completed heater being then
more or less cubical in pro-
portion. The figure shows a
heater two sections in depth
162 HEATING AND VENTILATION
and ten sections in width. Provided the conditions demand
It, the heater may be built two or even three stacks In
height, thus doubling- or tripling the gross wind area. See
Art. 119.
'Cast iron heaters are usually of the Tcnto type and are
m^de in two thicknesses, 6.75 and 9.125 inches in the direc-
tion of the air velocity. They are also made in three
heights, 40, 50 and 60 inches. These heaters present the fol-
lowing amounts of heating surface: 6.75 inch sections —
7.5, 9.5 and 11 square feet; 9.125 inch sections — 10.75, 13.5
and 16 square feet of surface for the 40, 50 and 60 inch
sections respectively. These sections give such a variety of
sizes as to permit combinations to fit almost any possible
requirement In net area, gross area and heating surface.
It is unusual to assemble less than five or more than twenty-
five sections to the stack. By the proper adjustment of
number of sections to the stack, and of stacks to the heater,
any requirement of hot blast work may be met.
No matter what kind or type of heaters may be selected,
certain methods of installing them have become common.
They may be placed on either the suction or the force side
of the fan, usually the former in drying or evaporating
plants, but more often the latter in heating plants. Because
of their weight, ample and firm foundations must be pro-
vided. In most installations for heating purposes, wliere
both tempered and heated air is supplied, the heater should
be raised on Its foundation 18 to 24 .inches to allow a
damper and passage way for tempered air.
104. Division of Coll Sur£aoe:^It is considered best
practice to install a hot blast heater in two parts, known
as the tempering coil and the heating coil. In the calculations.
Arts. 115-119, the total heating surfaoe is first obtained and
then this is split up into whatever arrangement is desired.
The tempering coils should be placed in the air p>assage
just within the intake for the building and should comtain
from one-fourth to one-third of the total heating surface.
In this way the air Is tempered before it reaches any other
apparatus, thus protecting from accumulation of frost on
fan and bearings and aiding in the process of lubrication.
The main heat cod is placed just beyond the fan on Its force
side. Referring to Figs. 96 and 97 it will be seen that, the
PLENUM WiARM AIR HEATING
163
PLAN.
ELEVATION.
Fig. 96. Fan Room Layout with Single Ductr along
Basement Ceiling and all Mixing Dampers at Plenum
Chamber.
164
HEATING AND VENTILATION
Fig. 97. Fan Room Layout with Double Underground
Ducts and Mixing Dampers at Base of Room Stacks.
PLENUM WARM AIR HEATING 165
heating coils can be of service only at such times as the
fan is in operation. If now these coils were split up into
small heaters and placed at the foot of the stacks leading
to the various rooms then air could be by-passed through
the plenum chamber and ducts, over the various radiating
surfaces to the rooms. In this way the heaters could be
used as indirect gravity heaters. The radiation in such a
case would be insufficient to keep the rooms at the same
temperatures as if the same amount of surface were placed
in the plenum coil next the fan. When the fan is in oper-
tion the air is moving at a high velocity over the heating
surface and the rate of transmission is very high. On the
other hand, when they are placed at the foot of the stacks
and used as indirect heaters, without the operation of the
fan, the air velocity and the amount of heat delivered to
■ the rooms are correspondingly reduced. In some cases the
heating coils are arranged in this way and used when the
building is not occupied. The convenience of such an in-
stallation can readily be seen; however, the expense of in-
stalling is greater than where they are assembled as coiis
at the fan. Exhaust steam from the engine is commonly
used in the tempering coil and live steam of low pressure
in the main heating coil. This may be varied by conditions,
however, and all surface supplied by exhaust steam if it is
thought advisable.
105. Single Duct Plenum System: — Duct systems in hot
blast work may be either of the single duct type or the
double duct type. In the single duct plant, every horizontal
duct is carried independently from the base of the room to
be heated to the small room called the plenum chamber, which
receives the hot blast from the heater. This chamber is
divided into an upper and a lower part, the upper receiving
the heated air that has been forced through the heater,
while the lower part receives only air that has been through
the tempering coilsi, or vice versa. The leader duct from
the base of each vertical room duct is led directly opposite
the partition between these two chambers, and a damper,
regulated by some system of automatic control from the
rooms to be heated, governs whether cool air from the lower
chamber, or hot air from the upper chamber, or a mixture
of both, shall be sent to the rooms. This system produces
rather a complicated net work of dampers and ducts at the
plenum chamber and this disadvantage has limited its use
very much.
166
HEATING AND VENTILATION
106. Double Duct Plenum System: — As its name Indi-
cates, this system runs a double leader duct from the
plenum chamber to the base of each vertical room duct, the
upper one of these ducts being in direct communication
with the upper part of the plenum chamber and carries
hot air, while the lower
one is in communication
with the lower part of
the plenum chamber and
carries cool air. No mix-
ing- or throttling is done
except at the base of the
vertical room duct, where
the mixing damper is lo-.
cated, it being controlled
by hand or automatically
directly from the room
above. With this scheme
it is evident that the
leader ducts for each
xoom need not be run
singly, but all the ducts
having the same general
direction combined in
one large double trunk,
from which branches are
taken to the various
room ducts as required.
The difference between
the two systems is shown by the two sketches, Figs. 96
and 97.
A hot blast plant may be installed as a basement or as
a suh-bascmcnt system. If the former, the leaders will be
suspended from the basement ceiling and usually con-
structed of sheet metal, thus forming what is often called a
"false ceiling." If the latter, they will be just below the
floor of the basement and will be constructed of brick and
mortar, or of concrete, about four inches thick. For designs
of conduits, ducts and dampers, see Figs. 90, 96, 97 and
98, the last showing a simple and direct installation often
applied to factories of several stories. Fig. 99 shows a
complete steel housed plenum unit of fan, coils, dampers
and duct connections.
Fig. 98.
PLENUM WARM AIR HEATING
167
Fig. 99.
107. Air Washing and Humidifying Systems: — In con-
nection with mechanical warm air heating and ventilating
systems, there is often installed apparatus for washing
and humidifying the air. In crowded city districts where
the air is laden with dust, soot, the products of combus-
tion and other harmful gases, its purification and moisten-
ing becomes a most important problem. The plenum system
of heating and ventilating lends itself most readily to
the solution of this problem, with the result that modern
practice is tending more each day toward the combined
installation of ventilating and humidifying apparatus. Fig.
100 shows a plenum system augmented by an air washing,
purifying and humidifying apparatus,
A purifier contemplates the installation of two parts, a
washer and an eliminator. The washer is built in the main
air duct, located immediately behind the tempering coils,
and provided with streams or sprays of water through
which the air must pass. Numerous schemes for breaking
up the water in the finest sprays are on the market, and
their relative merits may be judged from trade literature.
Having caught the dust particles and dissolved the soluble
gases from the air, the water falls to a collecting pan at
the bottom of the spray chamber, and from there is again
pumped through the spraying nozzles. As the water be-
comes too dirty or too warm, a fresh supply is delivered to
the collecting pan. A small independent centrifugal pump
is commonly used for the circulation of the spray water.
After passing through the washer, the air next encoun-
ters the eliminator, the purpose of which is to remove the
surplus moisture and water particles remaining suspended
in the air. This is accon\plished by an arrangement of
168
HEATING AND VENTILATION
more or less complicated l)affle plates, which cause the air
to change its direction suddenly many times in succession,
with the effect that the water particles impinge upon and
adhere to, the baffle plates. These are suitably drained to
the collecting" pan beneath the washer. As the air leaves
the eliminator and enters the fan it may, with good ap-
paratus, be relieved of 98 per cent, of all dust a-»d dirt, may
Fig. 100.
be supplied with moisture to very near the saturation point,
and, in summer time under favorable conditions, may be
cooled from 5 to 10 degrees lower than the atmosphere.
This is due to the cooling effect of vaporizing part of the
water.
Special air cooling plants have been installed in connec-
tion with the plenum system of ventilation, whereby refrig-
erated brine could be circulated in the regular heating coils.
The description of such a plant with data, may be found in
the transactions of the A. S. H. & V. E. for the year 1908.
^
CHAPTER XI.
ME3CHANICAL. WARM AIR HEATING AND
VENTILATION. FAN COIL SYSTEMS.
AIR, HEATING SURFACE AND STEAM REQUIREMENT.
PRINCIPLES OF THE DESIGN.
108. Definitions of Terms: — In the work under this gen-
eral heading, some of the technical abbreviations that are
frequently used are the following: H = B. t. u. heat loss
per hour by the formula, Ev = B. t. u. heat loss per hour by
ventilation, i/' = total B. t. u. loss including ventilation
loss, Q = cubic feet of air used per hour as a heat carrier,
Q' = cubic feet of air used including extra air for ventila-
tion, B = total square feet of heating surface in indirect
heaters, ts = temperature of the steam or water in the
heaters, t = highest temperature of the air at the register
(let this be the same as the temperature of the air upon
leaving the heater), V = temperature of the air In the room,
tv = temperature of the air at the register when extra air
is used for ventilation, to = temperature of the outside air,
K = rate of transmission of heat per square foot of surface
per degree difference per hour, N = the number of persons
to be provided with ventilation, V = velocity in feet per
minute and v = velocity in feet per second. Other abbre-
viations are explained in the text,
109. Theoretical Considerations: — For illustrative pur-
poses, references will frequently be made throughout this
discussion to a sample plenum design. Figs. 104, 105 and 106.
These show the essential points of most plenum work and
will serve as a basis for the applications. In working up
any complete design the following points should be' theo-
retically considered for each room: the heat loss, the cubic
feet of air per hour needed as a heat carrier (this should
be checked for ventilation), the net area of the register
in square inches, the catalog size of the register, and the
area and size of the ducts. In addition to these the follow-
ing should be investigated for the entire plant: the size
of the main leader at the plenum chamber, the size of the
170 HEATING AND VENTILATION
principal leader branches, the square feet of heatlngr sur-
face in the coils, the lineal feet of coils, the arrangements
of the coils in groups and sections, the horse-power and
the revolutions per minute of the fan including the sizes
of the inlet and the outlet of the fan, the horse-power of
the engine including the diameter and the length of stroke,
and the pounds of steam condensed perTiour in the coils.
Fresh air is taken into the building at the assumed
lowest temperature, to degrees, is carried over heated coils
and raised to t degrees, is propelled by fans through ducts
to the rooms and then exhausted through vent ducts to the
outside air, thus completing the cycle. It will be the object
to so discuss this cycle that it will be general and so it will
apply to any case which may be brought up.
110. Heat Loss and Cubic Feet of Air Exliausted per
Hour: — It is assumed here, that in all mechanical draft
heating and ventilating systems, the circulating air is all taken
from the outside and throicn aicay after being used. Some installa-
tions have arrangements for returning the room air to the
coils for reheating, but such schemes should be considered
as features added to the regular design rather than as being
a necessary part of it. It is best to design the plant with
the understanding that all the air is to be thrown away,
it will then be large enough for any service that it is ex-
pected to handle. Having found // by some acceptable
formula, the total heat loss is (compare with Arts. 29 and
36.)
(Q or 0') (t' — to)
H' = H + (37)
When t' = 70 and to = zero, this formula reduces tO
jr = H + 1.27 (0 or Q')
To determine whether Q or Q' will be used find how many
people would be provided with ventilating air with the
volume 0. If Q = 55 F -i- (« — f),t= 140 and t' = 70, then
55 /f zr //
2J = = = approximately (38)
1800 (t — f) 2290 2300
If more people than N will be using the room at any one
time, then Q' will be used instead and this value would be
1800 times the number of persons in the room. In any or-
dinary case, Q will be sufficient. When this is so, formula
37 reduces to
W = 2 II (39)
PLENUM WARM AIR HEATING 171
The reasoning- of this formula is easily seen when it is re-
membered thcit the heat given off from the air in dropping
from the register temperature, 140°, to the room tempera-
ture, 70°, goes to the radiation and leakage losses, H, while
that given off from the inside temperature, 70°, to that of
the outside temperature, 0°, is charged up to ventilation
losses, Hv. Since these values are equal, H' = H -^ Hv =^ 2 H.
Application. — Referring to Fig. 105, room 15, and Table
XVI, page 176, it is seen 'that the calculated heat loss H, for
this room, with f = 70 and to = 0, is 70224 B. t. u. per hour;
also, that the cubic feet of air, Q, if f = 140, is 54775 per
hour. Applying formula 39, the total heat loss, H', be-
comes 140448 B. t. u. per hour, or twice the amount found
by the heat loss formula. With 54775 cu'bic feet of air sent
to the room per hour, this will provide good ventilation for
thirty persons. Suppose, however, that fifty persons were
to be provided for; this would require 50 X 1800 = 90000
cubic feet of air per hour. With this increased number of
people in the room, the total heat loss would not be as
stated above, but would 'he according to formula 37.
90000 (70 — 0)
H' = 70224 H = 184864.
55
111, Temperature of the Entering: Air at the Register t
— In plenum work, the registers are placed higher in the
wall and the velocity of the air is carried a little higher
than in furnace work. It may be said that 140° is probably
the accepted temperature for design, excepting where an
extra amount of air is demanded for ventilation purposes.
In- the latter case, the temperature of the air would neces-
sarily drop below 140° in order that the room would not be
overheated. The general formula is
55 H
tv = r -] (40)
Q'
Application. — Referring to room 15 and (compare with
Art. 38) assuming the heat loss to have been figured as
before with ventilating air supplied sufficient for 50 per-
sons, 90000 cubic feet per hour, then the temperature of the
air at the register is
55 n
f = 70 ^ = 113'
90C00
172
HEATING AND VENTILATION
The temperature of the air at the register Is the
same or slightly less than the temperature of the air upon
leaving the coils. If this room were to be the only one
heated, then the coils would be figured for a final temper-
ature of the air at 113°, but other rooms may have air
entering at higher temperatures, hence the temperature *
upon leaving the coils should be that of the highest t at
the registers.
112. Cubic Peet of Air Needed per Hour: — The following
amount of air will be needed per hour as a heat carrier
(compare with Art. 36).
Q
55 H
■; where t = 140 and f = 70, g =
t — r 1.27
If extra air be needed for ventilation, Q' = 1800 N.
113. Air Velocities, T, in the Plenum System; — Table
XIII gives the velocities in feet per minute that have been
found to give good satisfaction in connection with blower
systems.
TABLE XIIL
Air Velocities in the Plenum System.
Offices,
schools, etc.
Auditoriums,
churches, etc
Shops and
factories.
Fresh
air
intake
^S
8
Over
coils
si
O o3
Main
duct
near
fan
1200 to
18(X)
say 1500
1600 to
2()00
say 1800
1500 to
8000
say 2000
Smaller
branch
ducts
800 to
1200
say 900
1000 to
1500
say 1200
1000 to
2000
say 1500
Stacks
500 to
700
say 600
Reg'rs
or other
open'gs
600 to
1000
say 800
300 to
400
say 800
600 to ! 400 to
800 I 600
say 700 I say 400
400 to
800
say 500
114. Cross Sectional Area of Registers, Ducts, etc.:—
With the above velocities in feet per minute, the square
inches of net opening at any part of the circulating sys-
tem can be obtained by direct substitution in the general
formula
144 (0 or Q')
A = (0 or g') X
60 V
= 2.4
(41)
PLENUM WARLi AIR HEATING
173
The calculated duct sizes, of course, refer to the warm
air duct. The cold air duct in double duct systems need not
be so large because on warm days, when only tempered air
is needed, the steam may be turned off from one or more
of the heaters and the warm air duct can then be used to
furnish what otherwise would be required from the cold
air duct. On account of this flexibility, it seems only nec-
essary to make the cold air duct about one-half the cross
sectional area of the warm air duct. For convenience of
installation, therefore, it would be well to make the former
of equal width to the latter and one-half as deep, unless by
so doing the cold air duct becomes too shallow.
Application. — Assuming 2000000 cubic feet of air to pass
through the main heat duct, Fig. 104, per hour at the veloc-
ity of 1800 feet per minute, the duct will be approximately
20 square feet in cross section, or 2^/^ by 8 feet. The two
inain branches at B will carry about 800000 cubic feet per
hour each at the same velocity and will be 7.4 square feet
in area or, say 2 by 4 feet. The same branches at C will
carry about 400000 cubic feet per hour each at a velocity of
1500 feet per minute and will be 4.4 square feet in area or,
say 2 by 2^/^ feet and the branch D will carry about 300000
cubic feet at a velocity of 1200 feet per minute and will be,
say 11/^ by 2% feet.
The stack sizes were first figured for the velocity of 600
feet per minute. These sizes were then made to fit the lay-
ing of the brick work such that the velocities would be
anywhere between 300 to 600 feet per minute. The net
register was figured for an air velocity of 300 feet per
minute and the gross registers were assumed to be 1.6
times the net area. See Art. 134.
115. Square Feet of Heating: Surface, i?, in the Coils: —
To determine theoretically the number of square feet of
heating surface in the coils of an indirect heater, the fol-
lowing formula may be used:
R = (42)
ts
t+to
Rule. — To find the square feet of coil surface in an indirect
heater, divide the total heat loss fro7n the building in B. t. u. per
hour by the rate of transmission, multiplied by the difference in
temperature between the inside and outside of the coils.
174
HEATING AND VENTILATION
Since the colls are figured from, the entire building loss,
//' will include the sum of all the heat losses of the various
rooms. Tlie chief concern in the use of this formula, as
stated, is to determine the best value for K, the rate of
transmission. Prof. Carpenter in H. and V. B., Art. 52,
quotes extensively from experiments with coils in blower
systems of heating- and summarizes all in the formula, K =
2 + 1.3 v. where v = average velocity of air over the coils
in feet per second. With the four velocities most appli-
cable to this part of the work, i. e., 800, 1000, 1200 and 1500
feet per minute, this becomes
800 feet per minute K = 6.9
1000 feet per minute K = 1 .3
1200 feet per minute Z = 7.8
1500 feet per minute JT = 8.5
In the table of probable efficiencies of indirect radiators in
Art. 54 by the same author, the values are somewhat higher,
being
750 feet per minute K = 7.1
1050 feet per minute K = 8.35
1200 feet per minute K = 9.
1500 feet per minute K = 10.
The values of K, as given here, are certainly very safe
when compared to quotations from other experimenters,
some of them exceeding these values by 50 per cent. It
is always well to remember that a coil that has been in
service for some time is less efficient than a new coil, be-
cause of the dirt and oil deposits upon the surface, hence
it is best in designing, not to take extreme values for ef-
ficiency. Assuming K = 8.5 and 1000 feet per minute air
velocity, which are probably the best values to use in the
calculations, also ts = 227 (5 pounds gage pressure), t =
140 and to = 0, formula 42 becomes
R =
H'
H'
H'
8.5
( 227
140 +
1335
say
1400
(43)
Table XIV quoted by Mr. C. L. Hubbard in Power Heat-
ing & Ventilation, Part III, page 557, gives the efficiencies
of forced-blast pipe heaters and the temperatures of air
delivered.
PLENUM WARM AIR HEATING
175
TABLE XIV.
EfRciencies of Forced-Blast Pipe Heaters, and Temperatures
of Air Delivered.
Velocity of air over coils at 800 feet per minute.
Rows
Temp,
will be
to which the air
raised from zero
of pipe
deep
Steam pressure in heater
51b.
20 lb.
60 lb.
4
30
35
45
6
50
55
65
8
65
70
85
10
80
90
105
12
95
105
125
14
105
120
140
16
120
130
150
18
130
140
160
20
140
150
170
Efficiency of the heating: sur-
face in B.t.u. per sq.ft. per hr.
Steam pressure in heater
5 lb.
1600
1600
1500
1500
1500
1400
1400
1300
1300
20 lb.
60 lb.
1800
1800
1650
1650
1650
1500
1500
1400
1400
2000
2000
1850
1850
1850
1700
1700
1600
1600
For a velocity of 1000 feet per minute multiply the
temperatures given in the table by 0.9 and the efficiencies
by 1.1.
Mr. F. R. Still of the American Blower Co., Detroit,
gives the following formula for the total B. t. u. trans-
mitted per square foot of surface per hour between the
temperature of the steam and that of the entering air.
Total B. t. u. transmitted = c Vv (ts — to)
(44)
in which case v is the velocity in feet per second and c is
a constant as follows:
176
HEATING AND VENTILATION
TABLE XV.
Values of c.
Safe factor
Max. factor
1 section 4
rows
of pipe
8.45
4.40
2 sections 8
rows
of pipe
8.00
8. 40
8 sections 12
rows
of pipe
2.63
2. 85
4 sections 10
rows
of pipe
2.83
2.45
5 sections 20
rows
of pipe
212
2 20
C sections 24
rows
of pipe
1.06
2.05
7 sections 28
rows
of pii>e
1.80
1.95
8 sections 32
rows
of pipe
l.«5
1 85
9 sections 86
rows
of pipe
1.62
1.80
10 sections 40
rows
of pipe
1.40
1.76
From the above values of c, Table XVI has been com-
piled, assuming ts = 227, to = and c = a safe value.
TABLE XVI.
Total transmission in B.
t. u. per sq.
Ct. per
hour.
«s
ts = 22'
•; to = 0.
o'r
^ ©
"
Rows of pipe deep.
>B
4
8
12
16
20
24
28
82
BOO
2840
2470
2164
1990
1760
1606
1460
1860
1000
8200
2790
2440
2170
1900
1810
1670
15S5
1200
8600
8040
2670
2860
2160
1980
1826
1678
1600
8960
3400
2961
2646
2400
2220
2020
1870
Cast iron heaters are being used for indirect heating In
many cases, replacing the old-fashioned pipe coil heaters.
The efficiency of these heaters is, according to tests, about
the same as that of the pipe coil heaters and hence formulaifl
42 and 43 will apply to both pipe and cast heaters. Table
^
PLENUM WARM AIR HEATING
177
XVII gives values of heat transmission for various sections,
taken from tests upon Vento oast iron heaters set up In
banks, and is added as a means of comparison with the
values quoted on the pipe coil heaters.
TABLE XVIL
Rate of Transmission of Heat, K, through Vento Colls.
Steam 227% Adr Entering at 0'.
Velocities of air over colls.
Sections
800
1000
1200
1500
1
7.6
8.8
10.0
11.8
2
7.1
8.2
9.2
10.5
8
6.6
7.7
86
9.7
4
6.1
7.1
7.9
9.0
5
5.6
6.5
7.3
8.8
6
5.2
6.0
6 7
7.7
7
4.8
5.5
6.2
7.1
In applying these values of K to formula 42 it should
be remembered that to would be used instead of - — ^^— ^ —
Application 1. Where Heating Only is Considered. — Referring
to Table XXV let H for the entire building be 1483251.
Then from Art. 112, Q = 1156935, by formula 39, H' = 2966502
and by formula 43, the coil surface is
2966502
B =
/ 140 + 0\
.5(227 -_)
= 2222 square feet.
With three lineal feet of 1 inch pipp per square foot of
surface, we have 6666 lineal feet of coils in the heater.
Application 2. Where Ventilation is Considered. — Assume 1100
people in the building on a zero day and Q' = 2000000, then,
H' = 1483251 + 1.27 X 2000000 = 4023251 and
4023251
R =
8.5 f 227
140 +
)
= 3014 sq. feet = 9042 lineal feet
178 HEATING AND VENTILATION
This value is probably the greatest amount that would
be needed. In such a case, when the rooms are supplied
with extra air, the register temperatures over the entire
building may be less than 140 degrees. Suppose in this
case the temperature is, by formula 40, t = 70 -f 55 X 1483251
-^ 2000000 = 111°, then
4023251
R = = 2760 sq. ft. = 8280 lineal ft.
Ill +
8.5
(--
2 /
In using this formula, the value t = 140 is to be recom-
mended wherever part of the rooms are not provided with
extra amounts of ventilating air. By so doing the ducts and
registers may be held down to a more moderate size and at
the same time give a safer figure for the heating surface.
Suppose that in a certain building most of the rooms
are to be ventilated and that these rooms will have large
amounts of air delivered at low temperatures. In such a
case it wnll be economy to heat the air for all rooms to this
temperature and supply more air to the rooms that would
otherwise be heated with air at 140 degrees, than to put
in a heater large enough to heat all the air to 140 degrees
and then dilute with large amounts of cold air to lower the
temperature to what it should be. Again, suppose that a
school building contains, in addition to the regular class
rooms, laboratories, etc., an auditorium and gymnasium, the
two together requiring an amount of air sufllcient to justify
a separate fan system (a condition which frequently exists),
it would be economy to separate the heating system for
these rooms from the rest of the building because of tlie
comparatively short time the rooms are in use. When not
in use the fan unit may be shut down without interfering
with the rest of the system. On the other hand, if united
with the rest of the building, the capacity of the unit would
be reached only when these rooms were in use, while at
other times it would run at a very low efficiency.
116. Approxininto Riilea for Plenum Heating: Surfaces t
— The following approximate rules are sometimes used In
checking up heating surface in the coils. These are not
recommended and should be used with caution.
Rule 1. — "Allow oue lineal foot of 1 inch pipe for each 65 to
125 cubic feet of room space"; 65 for office buildinps, schools, etc.,
and 125 for shops and laboratories. Sirice this buildinp has approx-
imatelii 500000 cubic feet of room space, it gives 7700 lineal feet
of 1 inch pipe in the heater.
PLENUM WARM AIR HEATING
179
Rule 2. — "Alloio 200 lineal feet of 1 inch pipe for each 1000
cubic feet of air per minute at a velocity of 1500 feet per minute."
Applying to the above building when the air moves over the coils at
1000 feet per minute, the heated surface is only about four-fifths as
valuable and xoould require 250 lineal feet per each 1000 cubic feet
of air per minute. This gives 8333 lineal feet of coils.
117. Final Air Temperatures: — Since the amount of
heat transmitted is directly proportional to the difference
of temperature between the two sides of the metal, the first
coils in the bank are the most efficient, and this efficiency
drops off rapidly as the air becomes heated in passing over
the coils. Final temperatures for different numbers of coil
sections in banks have been found by experiment and may
be taken from Table XVIII. See also Table XIV, page 175.
TABLE XVIII.
TempeTatures of Air upon Leaving Colls, Steam 227°, Air
Entering at 0".
Velocities of air through coils in F. P. M.
Sections
No. of
Rows
800
1000
1200
1500
1
4
42
33
28
23
2
8
71
62
56
52
3
12
96
87
80
75
4
16
119
108
101
93
5
20
136
125
116
108
6
24
153
140
131
120
7
28
169
155
143
131
8
32
183
166
154
141
These temperatures may be increased about 10 per cent,
for 20 pounds gage pressure.
Table XIX shows similar results quoted for the Vento
cast Iron heaters.
,
180
HEATING AND VENTILATION
TABLE XIX.
Temperatures of Air upon Leaving Vento Coils, Steam 227'
Air Entering at 0°. Regular and N-arrow Sections
5 Inch Centers.
o.
•M *
O'O
Velocities of air through colls In F. P. M.
800
1000
1200
1500
0°
-10°
-20°
0°
-10°
-20°
0°
-10"
-20°
0°
-10°
-£0°
1
Reg.
Nar.
88
86
82
80
2
Reg.
68
61
bb
Q'i
55
48
59
51
44
53
46
t8
Nar.
51
48
36
46
88
81
48
85
89
81
8
Reg.
93
87
82
87
80
76
82
75
69
74
68
61
Nar
70
64
bV
65
58
52
61
54
47
55
48
41
4
Reg.
113
108
103
106
1(K)
96
100
95
90
92
86
81
Nar.
88
82
77
82
76
70
77
70
6-t
70
68
66
6
Reg.
130
126
122
122
118
114
116
111
107
108
102
97
Nar.
103
97
m
96
90
86
90
84
80
83
77
71
6
Reg.
148
140
136
136
132
128
129
126
121
120
116
112
Nar.
115
111
107
108
104
100
102
98
93
94
8<)
84
7
Reg.
154
151
148
147
144
141
141
137
\m
182
128
134
Nar.
127
123
120
120
115
111
114
109
105
105
100
96
118. Arrangement o£ Coil.s in Pipe Heaters: — Coil sec-
tions are arranged with 2, 3 and 4 rows of pipes per sec-
tion. Unless special reference is made to this point, the
latter value is understood. Having found the total square
feet of heating surface in the heater, obtain from the tem-
perature tables the number of sections deep the heater will
need to be to produce the desired temperature, and find the
number of square feet of heating surface per section and
per row of coils. Let this latter value be A. Also find the
net wind area across the coils, assuming, say 1000 feet per
minute velocity. From the net wind area, find the gross
cross sectional area of the heater by the value
Gross wind area = 2.5 times net wind area. (45)
From the gross area the size of the heater may be selected.
In selecting the heater, the following check should be ap-
plied. Find the number of square feet of heating surface,
B, in each row of the coils as figured from the gross area
and compare with A. These must be made to agree.
Let the net area between the tubes, N. A., the space
i
PLENUM WARM AIR HEATING
181
occupied by the tubes, T. A., and the gross cross sectional
wind area through the tube, G. W. A., be respectively
2\^. A.
QoyQ' QotQ' QotQ'
-; T. A. = ; and G. W. A. = (46)
60 y 40 y 24 y
Since the cross sectional space T. A. occupied by the tubes
is to the coil surface per row as 1 : 3.1416, the total coil
surface in one row of tubes is
3.1416 (Q or Q') (Q or g')
Ri = = .08
40 y y
Reduced to the basis of the net area, N. A., we have
i?i = 4.8 times N. A. (47)
If B is greater than A, then the total heating surface
must be increased in that proportion, since the number of
sections cannot be less or the final temperature will drop
below the required degree, and the net cross section cannot
be less or the velocity of the air will be greater than that
desired. On the other hand, suppose B should be less than
A. In that case the total heating surface will not change
from that calculated. Either B may remain the same as
calculated and the number of sections increased (if de-
sirable) until all the heating surface is accounted for, or A
may remain constant and B may be increased. The latter
method is probably a better one since it gives larger wind
areas and consequently reduced velocities of the air, which
in many cases is desirable, and avoids placing heating .sur-
face at the rear of the bank where it is less efficient.
Assembled sections of pipe coil heaters are supplied by
manufacturers from the smallest size of 3 feet x 3 feet, to
the largest size of 10 feet x 10 feet; these dimensions being
those of the gross cross-sectional area, and not dimensions
overall. Between the two limits, both height and breadth
usually vary by 6 inch increments. For exact sizes, consult
dimension tables in manufacturers' catalogs.
Application 1. — In Article 115, let R = 2222, Q = 1156935,
V = 1000 and t = 140; then from Table XVIII the heater will
require 24 rows of coils in depth to give the required tem-
perature. Next find Ri = 93 square feet of heating surface
per row, also
N. A. ~ 19.7; T. A. = 29.6; and G. W. A. = 48.3.
Checking N. A. with an air velocity of 1000 feet per min-
ute gives 1156935 -^ (60 X 1000) = 19.3 square feet, which
282 HEATING AND VENTILATION
shows that the above arrangement is satisfactory. Now
from the value O. W. A, = 48.3 select a heater, say 6 feet
X 8 feet.
Application 2. — In article 115, let R = 3014, Q' = 2000000,
V = 1000 and t = 140; then as before, the heater will need
24 rows of coils. Find in this case Ri = 126 and
N. A. = 26.3; T. A. = 39.4; and G. W. A. = 65.7.
Checking from the volume of air delivered, obtain
N. A. = ZZ.Z; T. A. = 50; and O. W. A. = 83.3.
From N. A. = 33.3 find Ri = 160, which shows that it will
160
be necessary to increase the total heating surface to
126
X 3014 = 3826 square feet. If it were considered advisable
to have 1200 feet air velocity the heating surface per row
would be reduced to 135 and the temperature, t, would be
reduced to 131. Both conditions are reasonable and in many
cases would be considered satisfactory.
Selecting the heater for the gross area of 83.3 square
teet, from the catalog size, would probably give a single
section 9 feet X 9 feet or a double section, each part 6
feet X 7 feet.
119. Arrangrement of Sections and Stacks In Vento Cast
Iron Heaters: — Applying only to Case 2, Art. 115, let R =
3014, Q' = 2000000, V = 1000, N. A. (least value) = 33.3, and i
= 140.
From Table 48, Appendix, either of the following ar-
rangements will give the necessary N. A. First. — Six stacks
deep, two sections high, 50 inches on top of 60 inches and
twenty sections wide. This makes a total of 590 square
feet to the stack or 3540 square feet total. The gross wind
area looking in the direction of the wind is 103 inches by
110 inches. Second. — Six stacks deep, two sections high, 60
Inches on top of 60 inches and eighteen sections wide. This
makes a total of 576 square feet to the stack or 3456 square
feet total. The gross wind area looking in the direction
of the wind is 93 inches by 120 inches. These arrangements
will guarantee a temperature of 136 degrees upon leaving
the coils. If this temperature is not sufficient then the
coils must be made seven sections deep and the total heat-
ing surface arbitrarily increased. Other arrangements
could be worked out with 4% inch and 5% inch spacings.
Also, narrow sections could be used in place of the regular.
It will be found, however, that the two stated are probably
PLENUM WARM AIR HEATING 183
the best arrangements that could be made. (See Table XIX
for temperatures.)
120. Use of Hot Water in Indirect Colls: — In most cases
low pressure steam is used as a heating medium in the in-
direct coils. It is possible, however, to use hot water in-
stead, where a good supply is to be had. In such an ar-
rangement the coils will be figured from formula 42, using
all values the same as for steam excepting ts, which will
be repilaced by the average temperature of the water. The
piping connections and the arrangement of the coils will
follow the same general suggestions as already stated.
121. Pounds of Steam Condensed per Square Foot oi
Heatin§r Surface per Hour: — From Art. 115 the number of
pounds of condensation per hour per square foot of surface
in the coils is
H'
m = (48)
R X Heat given off per pound of condensation.
Application. — Let R = 3014 and H' = 4023251; also let
one pound of dry steam at five pounds gage in condensing
to water at 212 degrees give off 1155.6 — 180.9 = 974.7. (See
Tables 4 and 8, Appendix), then
4023251
m = =1.37 pounds.
3014 X 974.7
This amount should, of course, be considered an average.
The first and last section in any bank would vary above
and below this amount by as much as 50 per cent, in the
average plant. The first coils may condense as much as 2
pounds of steam per square foot of surface per hour.
122. Pounds of Dry Steam Needed in Bxcess of the
E^xhaust Steam Given off From the Engine: — Let the heat-
ing value of the exhaust steam from the engine be 85
per cent, of that of good dry steam, also let the engine
use 40 pounds of dry steam per horse power hour in driv-
ing the fan. From Art. 132, the engine will use 40 X 13.6
= 544 pounds of steam per hour and the heating value will
be 974.7 X .85 = 828 B. t. u. per pound or 828 X 544 = 450432 B.
t. u. total per hour. Then 4023251 — 450432 = 3572819 B.
t. u., and 3572819 -4- 974.7 = 3664 pounds of steam. The
boiler will then supply to the engine and coils, 3664 + 544
= 4208 pounds of steam total and will represent, approx-
imately, 4208 -r- 30 = 140 boiler horse power.
CHAPTER XII.
MECHANICAL WARM AIR HEATING AND
VENTILATION. FAN COIL SYSTEMS.
PRINCIPLES OF THE DESIGN, CONTINUED.
FANS AND FAN DRIVES.
123. Theoretical Air Velocity: — The theoretical velocitiv
of air V, flowing from any pressure, pa, to any pressure, pb,
is obtained from the general equation v = y/^gh, where v
is given in feet per second, g = 32.16 and h = head in feet
producing flow. This latter value may be easily changed
from feet of head to pounds pressure and vice versa.
When exhausting air from any enclosed space into
another space containing air at a different density, the
force which causes movement of the air is pa — p6 = p*.
These recorded pressures may be taken by any standard
type of pressure gage and show pressures above the at-
mosphere. When exhausting into the atmosphere, the value
pb is zero and pa = px. Tlie fact that a difference of pres-
sure exists between two points indicates that there are
either two actual columns (or equivalent as in Fig. 8) of
air at different densities connected and producing motion,
or that, by mechanical means, a pressure difference is crea-
ted wliich may easily be reduced to an equivalent head h,
in feet, by dividing the pressure head by the density of the
air, as
pressure difference pa — pb
h =
density d
Let Pa — Pb = Px = ounces of pressure per square inch of
area producing velocity of the air; also, let g = acceleration
due to gravity = 32.16 and d = density, or weight, of one
cubic foot of dry air at 60 degrees and at atmospheric pres-
sure (Table 12, Appendix), then, substituting dn the general
equation, we have
"61.32 X liipx
= 87 V;^' (49)
.0764 X 16
Since the pressure producing flow is usually meas'ured
in inches of water, ^«., the above can be changed to equiva-
lent height of air column by
weight of water, per cu. ft. at given temp. X Tiio
h = (50)
weight of air at given temperature X 12
.=j
PLENUM WARM AIR HEATING
185
Applying- this to dry air at 60 degrees and water at the
same temperature (Tables 12 and 8, Appendix, also Art. 15),
62.37 Jix
li =
= 68 hi
12 X .0764
then substituting in the general equation, find
V = V64.32 X 68 hw = 66.2 Vhw (51)
Formula 50 at the temperatures 50, 55, 60, 65 and 70
degrees respectively, gives results varying between v= 65.5
V?ri7 f or 50 degrees and v = 66.5 V^ for 70 degrees, which
leads to the approximate general rule that the theoretical
velocity of air, when measured by a water column gage that meas-
ures in inches of water, equals sixty-six times the square root of the
height of the column in inches. Stated as a formula
V 1= 66 V~^ (52)
for calculations requiring- accuracy, several factors af-
fect the final result; atmospiheric pressure, humidity, and
the density and change of temperature in the air current.
Let the atmospheric pressure and the humidity be
constant, since these would affect the result but little, and
first take into account ti ^ density of the air. Let the
pressure of the atmosphere be 29.92 inches of mercury
(14.7 pounds = 235 ounces per square inch area) then,
since the density is proportional to the absolute pressure,
the temperature remaining constant, we have from form-
ula 49 with air exhausting into the atmo.sphere.
-4
64.32 X 144 px
.0764 X 16 X
235 + Px
235
=: 1336
i
Px
235 + Px
(53)
Also from the relation existing between formulas 49 and
51, formula 53 reduces to
V = 1336
V
T,
(54)
407 + hw
From formulas 53 and 54 the second columns in Tables
XX and XXI have been calculated.
Application. — Air is exhausted from an orifice in an air
duct into the atmosphere. The pressure of the air within
the duct is one ounce by pressure gage or 1.74 inches by a
Pitot tube. Assuming the air to be dry and tne barometer
standing at 29.92 inches when the water in the tube is 60
degrees, what is the velocity of the air? By the approxi-
mate formulas 49 and 52
186
HEATING AND VENTILATION
r = 87 Vr~= 87 F. P. 8.
and v = 66 y/l.li = 87.2 F. P. 8.
By formulas 53 and 54
17 = 1336
^ 235+1
!6.3 F. P. 8.
and V = 1336
^ 407 + 1.7
= 87.1 F. P. B.
+ 1.74
TABLE XX.
Column 2 figured from formula 53.
8 .
o a
is
« 0)
Velocity of dry air at 60o es-
caping into the atmosphere
through any shaped orifice in
any pii)e or reservoir in which
a given pressure is main-
tained.
Vol. of air in cu.
ft. which may be
discharged in 1
min. through an
orifice having an
eflfective area of
discharge o f 1
SQ. inch.
H. P. required to
move the given
vol. of air under
the given con-
ditions f dis-
charge.
( Col. 3 X Col 1 )
Ft. per sec.
Ft. per min.
Ool. 8 H- 144
16X33000
Ks
30.80
1848.00
12.83
0.00044
J<
4856
2613.60
18.15
0.00124
^
53.27
3196 20
22.19
0.00227
'A
61.56
3693.60
25. 65
0.00:349
n
68.79
4127.40
28 66
0.00489
H
75.35
4521.00
31.47
0.00612
'A
81.87
4882.20
83.90
0.00809
1
86.97
5218.20
36.24
0.00988
1%
92.18
5530.80
88.41
0.01178
VA
97.18
5830.80
40.49
0.01380
IH
101.90
6114.00
42.46
0. 01592
VA
106.40
6384.00
44.33
0.01814
IH
110.82
6619. 20
46.11
0.02W6
IK
114.86
6891.60
47.86
0.022»4
VA
118.85
718100
49.52
0.02633
2
122 47
7»18.20
51.03
0.02787
PLENUM WARM AIR HEATING
187
TABLE XXL
Column 2 figured from formula 54.
Velocity
of dry air at 60° escapinsr into the atmosphere
Pressure
througrh
any shaped orifice in any pipe or reservoir in
head in
which a
gfiven pressure is maintained.
Inches of
water
Feet per second
Feet per minute
1
29.04
1256.40
.2
29.67
1780 20
.3
86.25
2175.60
.4
41.86
2511.60
.5
46.80
2708.00
.6
51.26
3075.60
.7
65. 36
3321.60
.8
59.10
8546.00
.9
62.60
3756.00
1.
66.14
3968.40
1 1
69.36
4161. 60
1 2
72.44
4346.40
1 3
76 39
4523. 40
1.4
78.21
4692.60
1.5
80.96
4857.60
1 6
83.59
5015.40
1.7
86.16
5169.60
18
88.65
6319.00
1.9
91.27
6476.20
2.
93.42
5605.20
2.1
95.72
5743.20
2 2
97 96
5877.60
2 3
100 15
6009.00
2.4
102.29 ■
6137.40
2 5
104.39
6263.40
2 6
106.43
6385.80
2 7
108.46
6507.60
2.8
110.43
6625.80
29
112.37
6742.20
3.
114.28
6856.80
3 1
116.15
6969.00
8 2
118. 00
7080.00
3 3
119. 81
7188.60
8 4
121.60
7296.00
8.6
123.36
7401.60
Finally, after considering the change of velocity that
takes place when the density changes with a constant tem-
perature, let the temperature change. With a constant
pressure, the volume changes with the absolute temperature
(460 + t). From this basis the values given in the second
inn
HEATING AND VENTILATION
columns of Tables XX and XXI, which were figured for 60
degrees, would be multiplied by the relative factors for
the given temperature as expressed in column two. Table
XXII, to obtain the velocity of the exhausting air at any
pressure and any temperature. Having found the data
from Column 2, find other points of information concerning
velocities, pressures, weights and horse powers in moving
air by multiplying by the factors as given in the respective
columns.
TABLE XXII.
Factor for rel-
a>
ative vel. at
same pressure
also relative
Factor for
relative pres-
sure, also wt.
Factor for rel-
ative vel. to
move same
Factor for rel-
ative power to
a
•a
a
powers to
move same
vol. of air at
same vel. =
of air moved
at same ve-
locity =
wt. of air also
relative pres-
sure to pro-
duce the vel. to
move same
•w t. of air at
vel. in column
4 and pressure
a
460O + 60O
T
move same wt.
of air =
1 -^ Col. 3.
in column 4 =
factor in col-
umn 4 squared
/ Wf. at any T
e-
'\Wt. at460o + B0o
80
.97
1.07
.93
.87
40
.98
1.04
.96
.93
60
.99
1.02
.98
.90
60
1.00
1.00
1.00
1 00
70
1.01
.98
1.02
1.04
80
1.02
.96
1.04
108
90
103
.94
106
1.18
100
1.04
.92
1.09
1.1»
125
1.06
.89
1.12
1.26
150
1.08
.85
1.18
1.80
175
1.10
.82
1.99
1.49
200
1 13
.79
1.27
1.61
250
1.17
.73
1.87
1.88
300
1 21
.68
1.47
2.10
860
1.25
.64
1.56
2.48
400
1.28
.60
1.67
2. 79
600
136
.64
1.86
8. 43
flOO
1.43
.49
2. 04
4 10
700
1.49
.45
2. 22
4.03
800
1.66
.41
2.44
696
124. Actual Amount of Air Exhnunted: — When air of any
pressure is exhausted from one receptacle to another through
an orifice, the actual velocity remains about the same as
the theoretical velocity, being slightly reduced by friction,
but the volume of air discharged Is greatly reduced because
PLENUM WARM AIR HEATING
189
of the contraction of the stream just as it leaves the ori-
fice. The greatest contraction or least size of the jet is
located from the orifice a distance of about one-half the
diameter of the opening. A round opening is the most effi-
cient. Since the velocity is slightly reduced and the effec-
tive area of the opening reduced a still greater amount, the
actual amount of air exhausted in any given time will be
found by multiplying the theoretical amount by a constant
wihich is the product of the coefficient of reduced velocity
and the coefficient of reduced area. From tests by Weisbach
the following approximate values are quoted by the Sturte-
vant Company in Mechanical Draft, page 152.
Orifice in a thin plate, .56
•Short cylindrical pipe, .75
Rounded off conical mouth piece, .98
Conical pipe, angle of convergence
about 6°, .92
125. Results of Tests to Determine the Relation be-
tween Pressure and Velocity in Air Transmission: — In fan
construction the number of blades, the shape of the blades,
the sizes of the inlet and outlet openings, the shape and
size of the casement around the blades and the speed, all
have an effect upon the relation between the pressure and
the velocity of the air discharge. From recent tests con-
ducted in the Mechanical Engineering Department, Univer-
sity of Nebraska, the curves shown in Pig. 101, a, were ob-
12
5£
H
si==
ri
^
K^ "
H
m
H
n
T
9
b'
cr
-A
Si
i?-^
^^
^
w^
n
^
b
a
.2 3 4 .5
RATIO OF OPENING
Fig. 101a.
.6 9
190
HEATING AND VENTILATION
2 .3 4 5
RATD or OPENING
Fig. 101b.
tained. A Number 2 Sirocco blower was belted to an elec-
tric motor and delivered air to a horizontal, circular pipe
whose length was nine times the diameter. This pipe was
provided with reducing nozzles which varied the area of
discharge by -tenths from full opening to full closed. The
air tube was provided also with manometer tubes for static,
dynamic and velocity pressures, arranged with an adjustable
scale to read to either .01 or .002 inch of water. The gross
power was taken by wattmeter and the delivered power
from motor to fan was taken by dynamometer. In addition
to this, the frictional horse-power of the fan and motor
unit was obtained by removing the fan wheel from the
shaft and taking readings with all other conditions remain-
ing as nearly constant as possible. The friction power,
when deducted from tlie grcss power recorded by the watt-
meter, gave the readings for the net horse-power curve.
A galvanized iron intake, enlarged from the size of the
fan intake to a rectangle four square feet in area and
divided up by fine wires into rectangles the size of the
standard anemometer, was used to find the volume of air
moved per minute. This volume Is shown In the curve
C. F. M. To check the curve, the volume was calculated for
each opening by the Pitot tubes on the side of the experi-
mental pipe.
PLENUM WARM AIR HEATING 191
To fully understand this article, refer to Art. 15 and note
that 4, Fig. 10, registers static pressure plus velocity pressure. This
sum may be called the dynamic pressure. Also, note that B reg-
isters only static pressure, i. e., that pressure which acts equally
in all directions and serves no usefulness in .moving the air.
Also, note that A — B = C, i. e., dynamic pressure minus
static pressure equa,ls velocity pressure. When applied in
the form shown by C, the pressure recorded is that due to
the velocity only. This is the form commonly used. Now
referring again to Fig. 101, A. Y. P. is that pressure re-
corded by C w.hen applied .to the air current at the fan out-
let, = air velocity pressure. P. V. P. is that pressure (ob-
tained by formulas 49 to 54) that would be shown on C if
the air were moving as fast as the tip of the blades on the
fan wheel, = peripheral velocity pressure, P. T. P. = 1 In
Fig. 101, b. D. P. is the dynamic pressure and would be
found by applying A only. 8. P. is the static pressure as
stated above.
In the tests, the *fan was run at constant speed and the
dynamic, static and velocity pressures were measured about
midway of the pipe at full opening. Then the openings were
changed by ten per cent, reductions until the piipe was fully
closed and similar readings taken for each reduction. T-hese
readings were plotted in the upper set of curves. Because
of the fact that the manometer tubes were located some
distance from the end of the experimental pipe, there was a
static pressure, ah, recorded at full opening. This caused
the dynamic pressure to be raised a corresponding amount,
a' b'. If the tubes had been loca.ted at the delivery end of
the pipe the static and dynamic pressures would have fallen
from & and 6' to a and a'. The peripheral velocity of the
wheel was 2828 feet per minute and the corresponding pres-
sure, with corrections for temperature, was found by formula
52 to be .5 in. of water. The relation between this peripheral
velocity pressure and the air velocity pressure is shown in
the lower set of curves. In applying the lower curves to .
fan practice they are very valuable in showiing the relation
between the velocity of the wheel circumference and that of
the air leaving the wheel. Notice that the relation between
the observed air velocity pressure and the calculated periph-
eral velocity pressure at full opening and discharging into
free air, is 1.20 : 1. Since the velocities vary as the square
roots of the pressures (v = V2gh), we find the velocities to
192 HEATING AND VENTILATION
be VI. 20 : VI = 1.1 : 1. That is to say, for this fan the air
velocity at the free opening of the fan is 1.1 times the per-
ipheral velocity of the wheel. The corresponding velocity
of the air from the average steel plate fan as reported by
the American Blower Company and as shown on the lower
chart, is VAb : VI = .67 : 1, or .61 of the speed of the
Sirocco fan for the same wheel speed. The resistance offered
by the ducts in the average plenum heating system is
equivalent, we will say, to that offered by a 75 per cent,
gate opening in the experimental pipe. According to the
diagrams for this opening, the ratio A. T. P. to P. 7. P is
1.04 for the Sirocco fan and .25 for the steel plate fan. The
ratio of the air velocities to the peripheral velocities then
are, respectively, V04 : Vir= 1.02 : 1 and V.25 : Vir= .5 : Ir
These show that with a 75 per cent, opening and with the
fan wheels running with a peripheral velocity of 3000 feet
per minute, the air would be entering the ducts at
1.02 X 3000 = 3060, and .5 X 3000 = 1500 feet per minute
respectively for the two types. Conversely, if it were de-
sired to ihave the air enter the ducts at 1500 feet per minute,
with a resistance equivalent to a 75 per cent, opening, the
fan wheels would have peripheral speeds of 1500 H- 1.02 =
1470, and 1500 -7- .5 = 3000 feet per minute respectively.
From these we obtain the wheel diameter for any given
R. P. M. Other models of the Sirocco and multiple blade
type of fans show less variation from the steel plate fan
than the one under consideration. It will be seen from the
above that the late change in construction from the steel
plate type to the multiple blade type permits a smaller
wheel and fan to be installed for any given work. This can
be shown to be a desirable change. From formula 61, it is
seen that the power required to drive a fan varies as the
fifth power of the diameter and as the cube of the speed.
With any given amount of air, Q, required per minute, the
power will be reduced very greatly by reducing the diam-
eter or by reducing the speed of the fan. Manufacturers'
catalogs should be consulted for capacities, sizes, etc. Such
tables are supplied by the trade in form for easy reference
and use.
126. Work Performed and Horne-Poirer Consamed In
Movlnisr Air; — The foot pounds of work performed in moving
air equals the product of the moving force into the distance
PLENUM WARM AIR HEATING
193
moved throug-h in any given time. Let pa — pb = px :=
moving force of the air in ounces per square inch and A :=
cross-sectional area of current in square inches. Then the
pounds per square inch will be px -^ 16, and the foot pounds
of work, W, and the horse-power, H. P., absorbed per min-
ute by the current of air in being moved, will be
W =
H. P. =
60 Px A u
16
3.75 Px Av
33000
= 3.75 Px A V
= ,000114 Px A V
(55)
(56)
This formula may be stated in terms of the cubic feet of
air discharged per miinute. Take the relation between px
and hw at 60 degrees as 12 p* = 16 X .433 hw; also, A X v =
144 Q' when Q' = cubic feet of air discharged per second
and, from formula 54, hw = v^ -^ 4356. Then by substituting
in formula 56
3.75 X .577 X v^ X 144 Q'
H. P. =
4356 X 33000
= .0000022.172 g' (57)
Application 1. — Let the effective area of a stream of dry
air at 60 degrees, exhausting between the pressures of pa =
1% ounces and p = V2 ounce, be 400 square inches. What is
the work performed per minute and the horse-power con-
sumed? (For velocity see second column Table XX).
W = 3.75 X (1% — %) X 400 X 87 = 130500 foot pounds,
and H. P. = .000114 X (11/2 — V2) X 400 X 87 = 3.96.
Application 2. — A fan is delivering 1000000 cubic feet of
aiir per hour to a heating system with a pressure of %
ounce. What is the theoretical horse-power of the fan?
H. P. = .0000022 X (74.5)2 x 277 — 3.38
127. Actual Horse-Po^ver Consumed in Moving Air by
Blower Fans: — The theoretical horse-power of a fan is that
horse-power necessary to move the air. This amount is al-
ways exceeded, however, because of the ineflficiency of the
blower. Let E = efficiency of the blower, then formulas 56
and 57 become
H. P. =
n. p. =
.000114 Px A V
E
.0000022 r2 Q'
E
(58)
(59)
194 HEATING AND VENTILATION
The value of E varies with the peripheral velocity and
the percentage of free outlet. When subjected to ordinary
service, the efficiency of the fan or blower may vary any-
where from 10 to 40 per cent. Probably a safe figure, for
an efficiency not definitely known, is 30 per cent, for cen-
trifugal fans in heating systems. Later improved types,
such as the Sirocco and Multivane fans, will be found from
40 per cent, to 60 per cent, efficient. See also Art. 131.
128. Carpenter's Practical Rules: — Many experiments
have been run upon blower fans to determine their capacity
in cubic feet of aiir delivered per minute and to determine
the horse-pow^er necessary to move this air. Probably as
satisfactory as any are the rules quoted by Prof, Carpenter
in H. & V. B., Art. 162, as follows:
Rule. — "The capacity of fans, expressed in cubic feet of air de-
livered per minute, is equal to the cube of the diameter of the fan
wheel in feet multiplied by the number of revolutions, multiplied by ■
a coefficient having the following approximate value : for fan with
single inlet delivering air without pressure, 0.6; delivering air with
pressure of one inch, 0.5; delivering air with pressure of one ounce,
0.4; for fans with double inlets, the coefficient should be increased
about 50 per cent. For practical purposes of ventilation, the ca-
pacity of a fan in cubic feet per revolution uHll equal A the cube
of the diameter in feet."
Rule. — "The delivered horse-power required for a given fan or
blower is equal to the 5th power of the diameter in feet, multiplied
by the cube of the number of revolutions per second, divided by one
million and multiplied by one of the folloxcing coefficients : for free
delivery, 30; for delivery against one ounce pressure, 20; for de-
livery against two ounces of pressure, 10."
The two above rules stated as formulas are as follows:
-V
Cu. ft. of air per min.
(60)
C X R. P. M.
where D = the diameter in feet and C = the coefflclent, .4
for pressure of one ounce, .5 for pressure of one incli, and
.6 for no pressure.
Z)» (ft. P. 8.)» X C.
H.P.= (61)
1000000
where C = 30 for open flow, 20 for one ounce and 10 for two
ounces pressure respectively. Tliese two rules may be
PLENUM WARM AIR HEATING
195
checked up by sizes obtained from catalogs. They give,
however, in ordinary calculations, very close approxima-
tions.
2Sfote. — In using formula 60 for Sirocco or Multivane
fans, the coefficient, C, becomes 1.1, 1.2 and 1.3 respectively.
Likewise, for formula 61 it becomes 100, 95 and 90 respec-
tively.
129. If it is Desired to Obtain the Approximate Sizes of
tlie Different Parts of the Fan Wheel and Opening, the same
can be found by the following table which gives good aver-
age values for steel plate fans. For more complete data
see tables in catalogs.
TABLE XXIIL*
Diameter wheel
Diameter inlet, single
Diameter inlet, double
Dimensions of exhaust
Width of wheel at outer ciTCumference
Least radial distance from wheel to casing
Maximum radial distance from wheel to
casing
Least side distance from wheel to casing
D
.66 D
.50 D
.60 D
X
.50 D
.50 D
to
.60 D
.08 D
to
.16 D
.50 D
to
1.00 D
.05 D
to
.08 D
Occupied space
of
full-housed fan
Length
Width
Height
Discharge vert.
1.7 D
.7 D
1.5 D
Discharge horiz.
1.5 D
.7 D
1.7 D
*This table does not apply to Sirocco or Multivane fans.
130. Fan Drives: — Fans for heating and ventilating
purposes, may be driven 'by simple horizontal or vertical,
throttling or automatic steam engines, or by electric mo-
tors; the principal advantage of the latter being the clean-
liness. In either case the power may be direct-connected
or belt-connected to the fan. Direct-connected fans make
a very neat arrangement, but they require slow speed
engines or motors, occasionally making them so large as to
be prohibitive. Where engines are used, any unusual noise
or pounding in the parts is frequently carried through the
fan to the air current and up to the rooms. Belted drives
may run at higher speeds but they must of necessity be set
Off from the fan ten feet or more to get good belt contact.
196 HEATING AND VENTILATION
Chain drives that are fairly quiet in operation will permit
the same reductions of speed and will allow the engine to
be set very close to the fan. Where a reduction is made in
the space between the engine and the fan, it had best be
made in the last named way.
In deciding between an engine drive and a motor drive
for use with steam coils, the amount of steam used In the
engine should not be considered a loss, since this is all
exhausted into the heater coils and is used instead of live
steam from the boilers. An engine of high efficiency is not
so essential either, unless the exhaust steam cannot be
used. Enclosed engines running in oil are preferred when
used on high speeds. The belt when used should, if pos-
sible, have the tight side below to increase the arc of
contact.
Electric motors have more quiet action and in special
cases should be specified. They would generally be speci-
fied for installations where the exhaust steam could not
be used, as in systems for ventilating only. This method of
driving the fan is more satisfactory in many ways but its
operation is usually more expensive. Direct current motors
are desirable, whenever they can be applied, because of the
convenience in obtaining changes of speed and because the
motors may easily be direct-connected to the fan. Alter-
nating current motors are used but they usually run at
higher speeds, requiring reduction drives and are not so
satisfactory in regulation. Speed reductions of 40 per cent,
may be had with alternating current machines where re-
quired.
131. Speed of the Pan: — A blower fan, exhausting into
the open air, will deliver air with a linear velocity slightly
below the peripheral velocity of the fan blades, but if this
same fan be connected to a system of ducts and heater
coils, the linear velocity of the air becomes much less be-
cause of the increased resistance and the lag or slip that
takes place between the fan blades and the moving air. In
the average heating system this slip may be as great as
40 to 50 per cent. See Art. 127. It is customary, therefore,
in applying blowers to heating systems, to consider the
linear velocity of the air as it leaves the fan to be one-
half that of the periphery of the fan blades. Since the
velocity of the air upon delivery from the fan should not
exceed 1800 to 2500 feet per minute, the outer point on the
PLENUM WARM AIR HEATING
197
fan blades should not be expected to move faster than 3600
to 5000 feet per minute. Knowing- this peripheral velocity,
the revolutions per minute may be selected and the diameter
obtained.
In all direct-connected fans the revolutions per minute
must agree with that of the engine or motor. In belted fans,
however, this restriction need not apply. It is found that
ordinary blower fans running at high speeds are very noisy
and so practice has determined largely the number of revo-
lutions to use. Speeds used by the American Blower Com-
pany in the latest type of Sirocco fan are given in the fol-
lowing table.
TABLE XXIV.
Speeds of Blower Fans in R. P. M.
Diameter of
Differential pressures.
wheel in
Inches.
1-2 oz.
3-4 oz.
1 oz.
11-2 0Z.
2oz.
18
538
660
762
933
1076
24
404
495
572
700
807
38
269
330
381
466
588
48
202
248
286
350
403
60
161
198
228
280
322
72
134
165
190
233
269
84
115
142
163
200
231
90
107
132
152
186
214
In the recent developments for blower fans the num-
ber of blades is increased and the depth of the blades is
diminished, making the operation of the fan somewhat sim-
ilar to that of the steam turbine. These fans seem to de-
velop a much higher efficiency under tests than the ordi-
nary paddle wheel fan. As a result, the diameter of the
w.heel may be smaller with the same revolutions for a given
work or the wheel may have the same diameter with a re-
duced speed for a given work. Tables 50, 51 and 52,
Appendix, give a summary of the latest catalog data.
132. Size of the E^nsinc: — In obtaining the size of the
198 HEATING AND VENTILATION
engine, it will be necessary first to assume the horse-power.
This had better be taken as a certain ratio to that of the
fan. Probably a safe value would be
E. P. of the engine = | //. P. of the fan (62)
Having obtained the horse-power of the engine, it will
next be necessary to find the size of the cylinder. Let pa =
the absolute initial pressure of the steam in the cylinder,
i. e., atmospheric pressure -|- gage pressure, and r = number
of the steam expansions in the cylinder, i. e., reciprocal of
the per cent, of cut-off. The cut-off allowed for high speed
engines in economical power service, approximates 25 per
cent, of the stroke, but in engines for blower work this
may be taken at 50 per cent, or half stroke. Find the
mean effective pressure, pi, by the formula
1 + hyperbolic logarithm of r
Pi = Pa back pressure (63)
r
Next, let I = lengtli of the stroke in inches and ^ = number
of revolutions per minute and apply the formula
2 pi I A N
n.P.= (64)
12 X 33000
and find A, the area of the cylinder, from which obtain rf,
the diameter of the cylinder. In applying formula 64 it
will be necessary to assume I. This, for engines operating
blowers, may be taken
2 i 2V = 200 to 400
Formula 63 assumes that the steam in the cylinder expands
according to the hyperbolic curve, pv = p'v'. For values
of hyperbolic or Naperian logarithms see Table 5, Appendix.
It also assumes no loss In the recompression of
the steam in the cylinder. Both assumptions are only
approximately correct, but the errors are sliglit and to a
certain degree, tend to neutralize each other, hence the
final results from this formula are near enough to be used
for approximate calculations. For such work as this, r
may be taken from 2 to 3, the former being probably pre-
ferred. The back pressure should not be taken higher than
5 pounds gage (19.7 pounds absolute), since this is deter-
mined by the pressure in the coils carrying exhaust steam.
This pressure, in o-rdinary service, drops nearly to atmos-
pheric pressure.
PLENUM WARM AIR HEATING
19»
lln finding the dianaeter and length of the stroke of the
cylinder, it may 'be necessary to make two or more trial
applications before a good size can be obtained. Owing
to the fact that the initial steam pressure is frequently
low, say not to exceed 40 or 50 pounds, the mean effective
pressure is small, thus calling for a cylinder of large
diameter. In such cases, the diameter of the cylinder may
be greater than the length of the stroke. In cases where
high pressure steam is used, say 100 pounds gage, the
diameter of the cylinder would be less than the length of
the stroke.
Application 1. — Assume the following to fit the design
shown in Figs. 104, 105 and 106: good dry steam from the
boiler to the engine at 100 pounds gage pressure; direct-
connected engine to fan, running at 180 revolutions per
minute and delivering 2000000 cubic feet of air per hour
to the building; steam cut-off in the cylinder at one-third
stroke and used in the coils at 5 pounds gage pressure;
find the sizes and horse-powers of the fan and engine unit.
Applying formulas 60, 61, 62, 63 and 64
D. of fan =
'4
2000000
= 5.5 feet.
H. P. of fan =
60 X 1.1 X 180
(5.5)5 X (3)3 X 87
1000000
= 11
Check the fan size and horse-power by Table 52, Appendix.
H. P.
of Engine = j X 11.8 = 15.7
Pi = 115
1 + 1.0986
)-
19.9 = 60.5 pounds per
250
square inch. Now if 2 I N = 250, then I =
360
= .69 feet =
8.25 inches and A =
15.7 X 12X 33000
= 34.5 square
2 X 60.5 X 8.25 X 180
inches = 6.625 inches diameter. The engine would be 6.625
inches X 8.25 inches, at 180 R. P. M.
Application 2. — Assuming the values as in application 1,
excepting that the steam is taken from a conduit main
under a pressure of, say 30 pounds per square inch gage,
that 2 I N =: 300, and that the steam cut-off in the cylinder
Is at one-half stroke. Then, as before, D of fan = 5.5 feet;
200 HEATING AND VENTILATION
n. p. of fan = 11.7; and 77. P. of engine = 15.7; the mean
effective pressure is, liowever,
1 + .6931
Pi = 45 / ) — 19.9 = IS. 2 pounds per sq. in.
= ,5 ( ^ )-
15.7X12X33000
and A = = 95 square inches.
2 X 18.2 X 10 X 180
Size of engine would be 11 inclies X 10 inches, at 180
R. P. M.
133. Piping: Connections around Heater and KnKlnet —
Where the fans are run by steam power it is considered
best to reduce the pressure of the steam by a pressure re-
ducing valve before allowing the live steam to enter the
coils. Where this reduction is made to 5 pounds or below,
it may be entered into the same main with the exhaust
steam from the engine, if desired; the back pressure valve
on the exhaust steam line providing an outlet to the at-
mosphere in case the pressure should run above the 5
pounds allowable back pressure. If the value of the back
pressure is increased much above 5 pounds, the efficiency
of the engine is seriously affected. In many installations
where the condensation from the live steam is desired free
from oil, a certain number of coils are tapped for exhaust
steam and this condensation trapped to a waste or sewer,
the other coils delivering to a receiver of some sort for
boiler feed or other purposes as may be required.
Every system should be fully equipped with pressure
reducing valves, back pressure valves, traps and a sufficient
numiber of globe or gate valves on the steam supply, and of
gate valves on the returns to make the system flexible and
responsive to varying demands. Figs. 102 and 103 show a
typical plan and elevation for such connections. Some en-
gineers advocate lifting the returns about 20 or 30 inches
as shown at A and B to form a water seal for each sec-
tion, thus making them independent in their action. This,
in some cases where the coils are very deep, would be a
benefit.
134. Application to ««chool niiildinp:: — The three follow-
ing figures and summary show the results of an applica-
tion of the above to a school building. The summary.
PLENUM WARM AIR HEATING
201
Table XXV, gives in compact form such calculated results
as admit of .tabulation. Most of the applications through-
out Chapters X, XI and XII, also refer to this same building.
The plans show the double-duct system, with plenum
chamber and ducts laid just below the basement floor. The
small arrows show the heat registers and vent registers for
each room. The same stack which served as a heat car-
(i)TRAP
R?3;5?»
|ENGlNi: I
OSTEAM 5tPAf»T0«
PR£b5.Rta VALVE
Fig. 102.
TO 4TM05PHER£
BACK PRE55U«[ VMVE
r.i
* GATE »»Ut5 -^ i^aW
Fig. 103.
fr
rier to the room on one floor serves as the vent stack
for the corresponding room on the floor above, there being
a horizontal cut-off between them. The cut-off at the heat
register should be so curved as to throw the current of
heated air into the room with the least possible friction or
eddy currents, as shown in Fig. 22.
202
HEATING AND VENTILATION
TABLE XXV.
Data Sheet for Figs. 104, 105, 106.
Room
n
Heat loss in B.t.u. per
hour from room not
counting ventilation
c
o
O u
w
•0
1
o
u
Cubic feet of air needed
per hour as a heat
carrier
•p
"3
«
c
w
u
*^
6e
a
u
o
d
o|
03 .
t. OQ
o3
*^£
03 ^
C
05
«
o:
"S
OS
w
(U
.£3
O
a
d
!^
o
09
00
«^
O
N
m
1
1
V/t
VA
VA
VA
"i\V
VA
VA
51,520
74.200
29,400
86,260
42,210
85,360
16'.520
16,520
42,210
40.185
57.876
22,982
28,288
82,923
27,578
i2';886
12,885
82,923
2
i"
1
1
1
i'
1
1
822
184
226
268
220
103
108
263
18x20
"lYxis
17x21
17x25
17x21
Y3"xi8
13x18
17x25
18x18
2
8
17x13
4
17x18
6
17x18
6
7
8
9
»-"-
17x18
isx 8
18x 8
10
17x13
Totals.
844,190
268,466
11
1
12
5i
18
VA
14
VA
15
VA
16
VA
17
1
18
1%
19
IH
20
VA
Totals.
81,180
115,430
40,600
66,370
63,840
48,440
51,940
23,660
28,660
63,840
540,100
63,281
99,039
31,775
47,507
54.775
89.672
40.518
19,377
18.466
49,796
2
4
1
2
2
1
2
1
1
2
506
792
278
880
488
817
824
166
148
898
17x24
17x18
17x26
17x18
17x21
17x80
13x20
13x20
13x20
17x18
126,973
44,585^
60,907
70,221
50,862
10
10
10
10
5
24,843
5
467,189
17x13
17x18
17x18
17x18
17x13
17x13
18x13
18x18
18x18
17x18
21
22
28.
24
25
26
27
J
28
%
29
80
Totals.
81.130
17,160
103,460
17,160
81,900
48,680
93,030
28.420
37,;«0
64,110
698,961
63.281
13.377
88.764
13.377
27,447
41,682
79,819
22,16;i
29,156
42,206
2
1
2
1
1
2
2
2
1
2
606
107
710
107
220
ms
im
177
2:38
s;58
17x24
13x18
21x28
13x13
17x21
13x20
17x80
13x15
17x21
13x20
118.800
10
85.189
53.4;}8
102.a38
10
10
10
421,272
17x18
18x 8
17x18
13x 8
17x18
13x13
17x18
18x 8
17x18
13x13
Vent registers taken same size as heat registers. For sizes of
engine, fan, heater colls, etc., see applications under these heads
PLENUM WARM AIR HEATING
203
«A
O en Q
204
HEATING AND VENTILATION
Fig. 105.
PLENUM WARM AIR HEATING
205
0)
O >
<
(/)
3
r K t" >
? -'^^
^ Cu Z O
O Q
'C o
W (0
M M
M°°^
1=1 M
H M
•^^"o^
'^is:
M M M~^
:/
I
"\ /■
i
"\
"^
~\
o a
i
Pig. 106.
^=-! I=t t^t"^"
L
s
\
:/ \:
i^
s
M.
M M ^M-^
i
tl
1
206 HEATING AND VENTILA.TION
REFERENCES.
References on Mechanical Warm Air Heatlngr.
Techxical Books.
Snow, Furnace Heating, p. 99. Monroe, Steam Heat, d Tent.,
p. 124. Carpenter, Heating and Ventilating liuihUngs, p. 333.
Hubbard, Power, Heating and Tetitilation, pages 525 and 551.
Technical Periodicals.
Engineering Review. Ventilating and Air Washing Appar-
atus Installed in the Sterling- Welch Building, Cleveland,
O., Jan. 1910, p. 38. Steam Heat, and Vent. Plant Required
for Addition to the Hotel Astor, New York, March 1910, p.
27. Heating and Ventilating Plant of the Boston Safe De-
posit and Trust Company's Building, C. L. Hubbard, April
1910, p. 37. Heating and Ventilating Installation on the
Burnet St. School, Newark, N. J., Jan. 1909, p. 20. Heating
and Ventilating the New Jersey State Reformatory, Sept.
1909, p. 27. Comparison of Heat, and Vent. Plants Installed
in Chicago Schools and Buildings at Various Periods, T. J.
Waters, June 1906, p. 14. Heating and Ventilating of
Schools, F. G. McCann, June 1906, p. 11. The Heating and
Ventilation of Schools, Dec. 1904, p. 1; March 1905, p. 4;
Sept. 1905, p. 1; Oct. 1905, p. 5. Note: — The last two articles
taken together comprise a complete series of the heating
and ventilating of the schools of Nev/ York City. Machinery.
Fans, C. L. Hubbard, Oct. 1906, p. 49; Nov. 1905, p. 109;
Dec. 1905, p. 165. Heaters for Hot Blast and Ventilation,
C. L. Hubbard, March 1907, p. 353. The Heating and Ven-
tilation of Machine Shops, C. L. Hubbard. Sept. 1907, p. 1.
Heating and Ventilating Offices in Shops and Factories, C.
L. Hubbard, Feb. 1910, p. 437. Fans, Machinery's Reference
Series, No 39. The Heating and Tentilating Magazine. Figuring
Flow of Air in Metal Pipes bv Chart, B. S. Harrison, Dec.
1905, p. 1. Flow of Air in Metal Pipes, J. H. Kinealy, July
1905, p. 3. Friction of Bends in Air Pipes, J. H. Kinealy,
Sept. 1905, p. 1. A Test of Hot Blast Heating Coils, March
1905, p. 1. Simplifying the Installation and Operation of
School Heating and Ventilating Apparatus, S. R. Lewis, July
1908, p. 10. A Rational Formula Covering the Performance
of Indirect Heating Surface, Perry West, March 1909, p. 1.
Charts Showing the Performance of Hot Blast Coils, B. S.
Harrison, Oct. 1907, p. 23. Loss of Pressure in Blowing Air
through Heater Coils, with New Formula, E. M. Shealy,
Nov. 1911. The Engineering Magazine. Modern Systems for
the Ventilation and Tempering of Buildings, Percival R.
Moses, Feb. 1908. Domestic Engineering. Practical Sugges-
tions about Blower Systems for Shop Heating, F. R
Still, Vol. 46. No. 4. Jan. 23, 1909, p. 100; Vol. 46, No.
5, Jan. 30, 1909. p. 125. Trans. A. 8. H. d V. E. Supplementing
Direct Radiation by Fans, Vol. X, p. 286. Methods of Test-
PLENUM WARM AIR HEATING
20t
Ing Blowing Fans, R. C. Carpenter, Vol, VI, p. 69. Some
Experlmients with the Centrifugal Fan, W. S. Monroe, Vol.
V, p. 117. The Metal Worker. Heating and Ventilating Willard
Parker Hospital, New York, July 6, 1907, p. 43. New Yo.rk Stock
Exchange, Aug. 5, 1905. p. 55. Fans, serial article beginning
May 2, 1908. p. 44. Heating and Ventilating a Factory, Sept.
12, 1908, p. 45. Obviating Noise in Fan Systems, serial begin-
ning Oct. 31, 1908, p. 52. Heating Messiah Home, Fordham, N,
Y., Nov. 21, 1908. p. 37. Filters for Air Supply, serial begin-
ning Nov. 28, 1908, p. 44. Heating Christian Science Church,
Boston, May 9, 1908, p. 35. Ventilation by Individual Air Ducts,
Frederick Bass, June 7, 1912. Railway Age Gazette. Heating Plant
for Mill, Nov. 13, 1908, p. 1369. The Engineering Record. A
Formula for Indirect Heating. Dec. 13, 1909. Temperatures
for Testing Indirect Heating Systems, W. W. Macon, Feb. 2,
1907, p. 135. Performance of Hot Blast Heating Coils, Jan.
28, 1905. Some Features of Indirect Heating, May 27, 1905.
Heating and Ventilating in the Carnegie Residence, N. Y.,
Oct. 3, 1903, Vol. 48, p. 403. Ventilating and Heating the
Rochester Athenaeum & Mechanics Institute, July 19, 1902,
Vol. 46, p. 60. Poicer. Horse-Power of a Fan Blower, Alibert
E. Guy, June 13, 1911. Heating and Ventilating System of
the Ritz-Carlton Hotel, Charles A. Fuller. Mar. 19, 1912.
Ventilating System for Small Schools, Charles A. Fuller,
Dec. 10, 1912.
CHAPTER XIII.
DISTRICT HEATING OR CENTRALIZED HOT WATER
AND STEAM HEATING.
GENERAL.
135. HeatlnpT Residences nnd Business Blocks from a
central station is a method that is being employed in many
cities and towns througliout the country. The centralization
of the heat supply for any district in one large unit has an
advantage over a number of smaller units in being able to
burn the fuel more economically, and in being able to re-
duce labor costs. It has also the advantage, when in con-
nection with any power plant, of saving the heat which
would otherwise go to waste in the exhaust steam and stack
gases, by turning it into the heating system. The many
electric lighting and pumping stations around the country
give large opportunity in this regard. Since the average
steam power plant is very wasteful in these two particulars,
any saving that might be brought about should certainly be
sought for. On the other hand, however, a plant of this
kind has the disadvantage in that it necessitates transmit-
ting the heating medium through a system of conduits, which
generally is a wasteful process. The failure of many of the
pioneer plants has cast suspicion upon all such enterprises
as paying investments, but the successful operation of many
others shows the possibilities, where care is exercised in
their design and operation.
136. Important Considerations In Central Station Heat-
ing:— In any central heating system, the following consider-
ations will go far towards the success or the failure of the
enterprise:
First. — There should be a demand for the heat.
Second. — The plant should be near to the territory heated.
Third. — There should be good coal and water facilities at
the plant.
Fourth. — The quality of all the materials and the Instal-
lation of the same, especially in the conduit concerning in-
DISTRICT HEATING 209
sulation, expansion and contraction, and durability, are
points of unusual importance.
Fifth. — The plant must be operated upon an economical
basis, the same as is true of other plants.
Sixth. — The load-factor of the plant should be high. This
is one of the most important points to be considered in com-
bined heating and power work. The greater the proportion
of hours each piece of apparatus is in operation, to the total
number of hours that the plant is run, the greater the plant
efficiency. The ideal load-factor requires that all of the ap-
paratus be run at full load all the time.
The average conduit radiates a great deal of heat, henoe,
the nearer the plant to the heated district the greater the
economy of the system. Likewise a location near a railroad
minimizes fuel costs, and good water, with the possibility
of saving the water of condensation from the steam, assists
in increasing dhe economy of the plant. It is to be expected
that even a well designed plant, unless safeguarded against
ills as above suggested, would soon succumb to inevitable
failure.
Two types of centralized heating plants are in use, hot
water and steam. Each will be discussed separately. In the
discussion of either system, certain definite conditions will
have to be met. First of all, there should be a demand in
that certain locality for such a heating system, before the
plant can be considered a safe investment. To create a de-
mand requires good representatives and a first-class resi-
dence or business district. When this demand is obtained
the plan of the probable district to be heated will first be
platted and then the heating plant will be located. In many
cases the heating plant will be an added feature to an al-
ready established lighting or power plant and its location
will be more or less a predetermined thing.
In addition to these material and financial features just
mentioned, one must consider the legal phases that always
come up at such a time. These relate chiefiy to the franchise
requirements that must be met before occuping the streets
with conduit lines, etc. All of these considerations are a
part of the one general scheme.
137. The Scope of the Work in central station heating
may be had from the following outline:
210
HEATING AND VENTILATION
Central Sta-
tion Heating'
Hot Water Heating
by use of
Steam Heating.
Exhaust steam heaters
Live steam heaters
Heating boilers
Economizers
Injectors or
Com-minglers
Exhaust s-team
Live steam
In the liot tcatcr system the return water at a lowered tem-
perature enters the power plant, is passed through one or
more pieces of apparatus carrying live or exhaust steam, or
flue gases, and is raised in temperature again to that in the
outgoing main. From the above, a number of combinations
of reheating can be had. Any or all of the units may be put
in one plant and the piping system so installed that the
water will pass through any single unit and out into the
main; or, the water may be split and passed through the
units in parallel; or, it may be made to pass through the
units in series. All of these combinations are possible, but
not practicable. In most plants, two or three combinations
only are provided. In the existing plants the order of pref-
erence seems to be, exhaust steam reheaters, economizers,
heating boilers, injectors or com-minglers, and live steam
heaters.
All of the above pieces of reheating apparatus operate
by the transmission of heat througli metal surfaces, such as
brass, steel or cast iron tubes, excepting the com-mingler,
this being simply a barometric condenser in which the exhaust
steam is condensed by the injection water from the return
main, the mixture being drawn directly into the pumps.
The objection to the tube transmission is the lime, mud
and oil deposit on the tube surfaces, thus reducing the rate
of transmission and requiring frequent cleaning. The ob-
jections to the com-minglers are, first, that the pump must
draw hot water from the condenser and second, that a cer-
tain amount of tlie oil passes into the heating line. With
perfected apparatus for removing the oil, the com-mingler
will no doubt supersede, to a large degree, the tube re-
heaters in hot water heating.
DISTRICT HEATING ^ll
In the steam system the proposition is very much simpli-
fied. The exhaust steam passes through one or more oil
separating devices and is then piped directly to the header
leading to tlie outgoing main. Occasionally a connection is
made from this line to a condenser, such that the steam,
when not used in the heating system, may be run directly
to the condenser. These pipe lines, of course, are all prop-
erly valved so that the current of steam may easily be de-
flected one way or the other. In addition to this exhaust
steam supply, live steam is provided from the boiler and
enters the header through a pressure reducing valve. In
any case when the exhaust steam is insufficient the supply
may be kept constant by automatic regulation on the reduc-
ing valve.
In selecting between hot water and steam systems the
preference of the engineer is very largely the controlling
factor. The preference of the engineer, however, should be
formed from facts and conditions surrounding the plant, and
should not come from mere prejudice. The following points
are some of the important ones to be considered:
First cost of plant installed. — This is very much in favor of
the steam system in all features of the power plant equip-
ment, the relative costs of the conduit and the outside work
being very much the same in the two systems.
Cost of operation. — This is in favor of the hot water sys-
tem because of the fact that the steam from the engines
may be condensed at or below atmospheric pressure, while
the exhausts from the engines in the steam systems must
be carried from five to fifteen pounds gage, which naturally
throws a heavy back pressure upon the engine piston.
Pressure in circulating mains. — This is in favor of the steam
system. The pressure in any steam radiator will be only
a few pounds above atmosphere, while in a hot water sys-
tem, connected to high buildings, the pressure on the first
floor radiators near the level of the mains becomes very
excessive. The elevation of the highest raddator in the
circuit, therefore, is one of the determining factors.
Regulation. — It is easier to regulate the hot water system
without the use of the automatic thermostatic control, since
the temperature of the water is maintajined according to a
schedule, which fits all degrees of outside temperature.
212 HEATING AND VENTILATION
WSien automatic control is applied, this advantage is not so
marked.
Returning the water to the power plant. — In most steam plants
the water of condensation is passed through indirect heaters,
to remove as much of the remaining heat as possible and
ds then run to the sewer. This procedure incurs a consider-
a/ble loss, especially in cold weather when the feed water
at the power plant is heated from low temperatures. This
point is in favor of the hot water system.
Estimating charges for heat. — This is in favor of the steam
system since, by meter measurement, a company is able to
apportion the charges intelligently. The flat rate charged
for water heating and for some steam heating is in many
cases a decided loss to the company.
138. Conduits: — In installing conduits for either hot
water or steam systems the, selection should be made after
determining, first, its efllciency as a heat insulator; second,
its initial cost; third, its durability. Other points that must
be accounted for as being very essential are: the supporting,
anchoring, grading and draining of the mains; provision for
expansion and contraction of the mains; arrangements for
taking off service lines at points where there is little move-
ment of the mains; and the draining of the conduit.
Some conduits may be installed at very little cost and
yet may be very expensive propositions, because of their in-
ability to protect from heat losses; while, on the other liand,
some of the most expensive installations save their first
cost in a couple of years' service. Many different kinds of
insulating materials are used in conduit work such as mag-
nesia, asbestos, hair felt, wool felt, mineral wool and air cell.
Each of these materials has certain advantages and under
certain conditions would be preferred. It is not the real
purpose here to discuss the merits of the various insulators,
because the quality of the workmanship in the conduit en-
ters into the final result so largely. The different ways that
pipes may be supported and insulated in outside service will
be given, with general suggestions only. Fig. 107 shows a
few of the many methods in common use. A very simple
conduit is shown at A. This is built up of wood sections
fitted end to end, then covered with tarred paper to prevent
surface water leaking in and bound with straps. The pipe
either is a loose fit to the bore and rests upon the inner sur-
DISTRICT HEATING 213
face, or is supported on metal stools, driven into the wood or
merely resting upon it. These stools hold the pipe concen-
tric with the inner bore of the log. With much move^ment
of the pipe endwise, from expansion and contraction, these
stools should not be used unless they are loose and have a
wide surface contact with the wood. A metal lining with
the pipe resting directly upon it is considered good. The
conduit is laid to a good straight run in a gravel bed and
usually over a small tile drain to carry off the surface water,
excepting as this drain is not necessary in sections where
there is good gravel drainage. The insulation in A is only
fair. The air space around the pipe, however, is to be com-
mended. B is an improvement over A and is built up of
boards notched at the edges to fit together. The materials
used, from the outside to the center, are noted on the sketch
beginning with the top and reading down. This covering is
in general use and gives good satisfaction from every stand-
point. C shows a good insulation and supports the pipe
upon rollers at the center of a line of halved, vitrified tile.
The lower half of the tile should be graded and the pipe then
run upon the rollers, after which it may be covered with
some prepared covering and the remaining space next the
tile filled with asbestos, mineral wool or other like material.
D shows the same adapted to cellar work. Occasionally two
pipes are run side by side, main and return, in which case
large halved tiles may be used as in E, having large metal
supports curved on the lower face to fit the tile. If these
supports are not desired the same kind of straight tiles may
be used with a tee tile inserted every 8 to 12 feet having the
bell looking down as in F. In this bell is built a concrete
setting with iron supports for the pipes which run on rollers,
over a rod. These rollers are sometimes pieces of pipes cut
and reamed, but are better if they are cast with a curvature
to fit the pipes to be supported. This form of conduit, when
drained to good gravel, gives first-class service. G, H and /
show box conduits with two or more thicknesses of % inch
boards nailed together for the sides, top and bottom. The
bottom of the conduit is first laid and the pipe is run. The
sides are then set in place and the insulating material put
in, after which the top is set and the whole filled in. / shows
the best form of box, since with the air spaces this is a
very good insulator. All wood boxes are very temporary,
hence, brick and concrete are usually preferred. Z is a
HEATING AND VENTILATION
-J-GRAVEL -
^PUMP LOG ,_^
STOOLS -J-^
PIPE
DRAIN
A
jGRAVEL
r^ABPHALTUM
WOOD
COR PAPER
ASBESTOS
TIN LINING
MIN WOOL-
PIPE
ROLLER
WOOD
TILE
MIN. WOOL-
SECTIONAL
COVERING
PIPE
ROLLER
msffi^imm
GRAVEL
TILE
MIN WOOL
PIPE
PIPE 5UPP
CONCRETE
DRAIN
Fig. 107a.
DISTRICT HEATING
215
STONE
BRICK
MIN WOOL
WOOD :^ F-^,.
NSULATION ^^
PIPE
ROLLER
GRAVEL —
DRAIN
v/<f(J,<(f(/f/^. " '.^/.{(<'<<.' [i^^^ '".'/i^^/'Jr ' '' ''^*^'%
■GRAVEL
-WOOD
Fig. 107b.
216 HEATING AND VENTILATION
conduit with 8 inch brick walls covered with flat stones or
halved glazed tiles cemented to place to protect from sur-
face leakage. The bottom of the conduit has supports built
in every 8 to 12 feet, and between these points the conduit
drains to the gravel. The usual rod and roller here serve
as pipe supports. The pipe is covered with sectional cover-
ing and the rest of the space may or may not be filled with
wool or chips, as desired. L shows the sectional covering
omitted and the entire conduit filled with mineral wool, hair
felt or asbestos, and ashes. M has the supporting rod built
into the sides of the conduit and has the bottom of the con-
duit bricked across and cemented to carry the leaks and
drainage to some distant point, y shows a concrete bot-
tom with brick sides, having the pipe supported upon cast
iron standards. The latest conduit has concrete slabs for
bottom and sides and has a reinforced concrete slab top.
This comes as near being permanent as any, is reasonable
in price, and when the interior is filled with good non-con-
ducting material, or when the pipe is covered with a good
sectional covering, it gives fairly high efficiency.
All conduits should be run as nearly level as possible
to a^void the formation of air and water pockets in the main.
Any unusual elevation in any part of the main may require
an air vent being placed at the uppermost point of the curve,
otherwise air may collect in such quantities as to retard cir-
culation. All low points in the steam lines must be drained
to traps.
The heat lost from conduits is an item of considerable im-
portance. A good quality of materials and insulation will
probably reduce this loss as low as 20 to 25 per cent, of
the amount lost from the bare pipe. To show the method of
analysis and to obtain an estimate of the average conduit
losses, the following application will be made to a supposed
two-pipe hot water system. The loss of heat in B. t. u. per
lineal foot from any pipe per hour may be taken from the
formula
He = KCA (f — t') (65)
where K = rate of transmission for uncovered pipes, C = 100
per cent. — efficiency of the insulation, A = area of pipe sur-
face per lineal foot of pipe, i = average temperature in the
DISTRICT HEATING
217
inside of the pipe and t' = average temperature on the out-
side of the conduit.
Application. — Having- given a system of conduit pipes
(two pipes in one conduit) with sizes and lengths as stated
in the first and second columns of Table XXVI, what is the
probable heat loss in B. t. u. per hour on a winter day and
what is the radiation equivalent in a hot water system car-
rying water at an average temperature of 170 degrees?
TABLE XXVI.
Pipe size
inches
Total lineal
feet of main
and return
Surface per
foot of length
A
B. t. u. per hr.
per lineal foot
He
Equivalent
no. of sq.ft.
of H.W. Ead.
2
5000
.62
48.8
1435
3
2000
.91
71.6
842
4
3000
1.06
83.4
1472
6
3000
1.73
137.1
2420
8
2000
2.26
177.9
2093
10
2000
2.83
221.9
2611
. 12
2000
3.33
262.0
3082
14
1000
4.00
314.8
1852
Totals. B. t. u. lost per hour 2687100
15807
U K = 2.25, = 100 — 75 = 25 per cent., t = 175 and
f = 35, we have for a 2 inch pipe. He = 2.25 X .25 X .62 X 140
= 48.8, which for 5000 lineal feet = 244000 B. t. u., and for
the entire system 2687100 B. t. u. If each square foot of hot
water radiation gives off 170 B. t. u. per hour then the
radiation equivalent for the 2 inch pipe is 244000 -h 170 =
1453 square feet. Similarly work out for each pipe size and
obtain the values given in the last column of the table. This
conduit loss is sufficient to heat 15807 square feet of radia-
tion in the district. In terms of the coal pile it approxi-
mates 350 pounds per hour. Now assuming the 14 inch
main to supply the entire district at a velocity of 6 feet per
second we have approximately 162000 square feet of H. W.
surface on the line. From this the line loss is 15807 -^ 162000
= 9.1 per cent. It should be remembered that the above as-
sumes the plant working under a heavy load when the per
cent, of line loss is a minimum. This loss remains fairly
218 HEATING AND VENTILATION
constamt while the heat utilized in the district fluctuates
greatly. In mild weather, therefore, the per cent, of line
loss to the total heat transmitted is much greater.
139. Layout of Street Plains and Conduits: — ^No definite
information can be given concerning the layout of street
mains, because the requirements of each district would call
for independent consideration. The following general sug-
gestions, however, can be noted as applying to any hot
water or steam system:
Streets to 6e used. — Avoid the principal streets in the city,
especially those that are paved; alleys are preferred because
of the minimum cost of installation and repairs.
Cutting of the mains. — Do not cut the main trunk line for
branches more often than is necessary. Provide occasional
by-pass lines between the main branches at the most Im-
portant points in the system* so that, if repairs are being
made on any one line, the circulation beyond that point may
be handled through the by-pass. Such by-pass lines should
be valved and used only in case of emergency.
Offsets and expansion joints. — Offsets in the lines hinder
the free movement of the water and add friction head to the
pumps; hence, in water systems, the number should be re-
duced to a minimum. Long radius bends at the corners re-
duce this friction. Offsets are especially valuable to take
up the expansion and contraction of the piping without the
aid of expansion joints. This is illustrated in Fig. 108, where
anchors are placed at A, and the gradual bending of the
pipes at each corner makes the necessary allowance. The
expansion in wrought iron is about .00008 inch per foot per
degree rise in temperature; hence in a hot water main the
linear expansion between 0° and 212° is .017 inch per foot of
length or 1.7 inches for each 100 feet of straight pipe. In
hot water heating systems, however, the temperature of this
pipe would never be less than 50°, which would cause an
expansion from hot to cold of only .013 inch per foot, or
1.3 inches for each 100 feet of straight pipe. In a steam
main the temperature may vary anywhere from 50* to 300*.
making a linear expansion of .02 inch per foot of length or 2
Inches for each 100 feet of straight pipe. As here shown V.)o.
DISTRICT HEATING
219
Fig. 108.
movement from, the anchor
at A toward B may be ab-
sorbed by the swinging of the
pipe about O. B.B. should
therefore be as long as possi-
ble, say one full block, to
avoid unduly straining the
pipe at the joints. Allowing a
maximum movement of 6
inches for each expansion joint, the anchors would be spaced
500 and 300 feet center to center respectively, for hot water
and steam mains. These figures would seldom be exceeded,
and in some cases Wiould be reduced, the spacing depending
upon the type of expansion joint used. Ordinarily, 400 feet
spacing would be recommended for hot water and 300 feet
for steam. If the city layout meets this value fairly well,
then the expansion joints and anchors may be made to
alternate with each other, one each to every city block.
A few of the expansion joints in common use are shown
in I ig. 109. A is the old slip and packed joint. This joint
causes very little trouble except that it needs repacking
frequently. It is very effective when properly cared for.
The slip joint should have bronze bearings on both the
outside of the plug and the lining of the sleeve. The ends
of the plug and sleeve may be screwed for small pipes,
or flanged for large ones. B shows an improved type of
slip joint, having a roller bearing upon a plate in the
bottom of the conduit, and plugs bearing against metal
plates along the sides of the conduit to keep it in line. C
and D show other slip joints very similar to A and B. C
has one ball and socket end to adjust the joint to slight
changes in the run of the pipe, and D has two packings
enclosing the plug to give it rigidity. The drainage in
each case is taken off at the bottom of the casting, E has
two large flexible disks fastened to the ends of the pipe and
separated from each other by an annular ring casting.
These disks are frequently corrugated, are usually of cop-
per and are very large in diameter so that the pipe has con-
siderable movement without endangering the metal in the
disks. F has a corrugated copper tube fastened at the ends
to the pipe flanges. This is protected from excessive inter-
nal pressure by a straight tube having a sliding fit to the
inside of the flanges, thus allowing for end movement. O is
220
HEATING AND VENTILATION
^1 .r
E U
,^
-^
u^^^ai^
3
yvitw """'
C
Fig. 109.
DISTRICT HEATING
221
very similar to E. It has, however, only one copper disk.
This disk is enclosed in a cast iron casement, one side of
which is lopen to the atmosphere, the other side having the
same pressure as within the pipe. H is very similar to E,
having two copper diaphragms to take up the movement.
These diaphragms flex over rings with curved edges and
are thus protected somewhat against failure. / shows a
copper U tube which is sometimes used. This is set in a
horizontal position and the expansion and contraction is
absorbed by bending the loop. In all these joints those
which depend upon the bending of the metal require little
attention except where complete rupture occurs. In old
plants, however, the rupturing of these diaphragms is of
frequent occurrence. The packed joint requires attention
for packing several times in the year, but very seldom
causes trouble other than this.
Anchors. — In any long run of pipe, where the expansion
and contraction of the pipe causes it to shift its position
very much, it is necessary to anchor the pipe at intervals so
as to compel the movement toward certain desired points.
The anchor is sometimes combined with the expansion joint,
in which case the conduit work is simplified. See Fig. 110.
COMBineo AncKoi
tl «1 PAW SI ON JOIHT
Fig. 110.
222
HEATING AND VENTILATION
Service pipes to residences are taken off at or near the
anchors. All condensation drains In steam mains are like-
wise taken off at such points.
Valves. — All valves on water systems should be straight-
way gate valves. Valves on steam systems should be gate
valves on lines carrying condensation, and renewable seat
globe valves on the steam lines. Valves should be placed on
the main trunk at the power plant, on all the principal
branch mains as they leave the main trunk, on all by-pass
lines, on all the service mains to the houses, and at such
important points along the mains as will enable certain
portions of the heating district to be shut off for repairs
without cutting out the entire district.
Manholes. — Manholes are placed at important points along
the line to enclose expansion joints and valves. These man-
holes are built of brick or concrete and covered with Iron
plates, flag stones, slate of reinforced concrete slabs. Care
must be exercised to drain these points well and to have the
covering strong enough to sustain the superimposed loads.
140. Typical Design, for Consideration: — In discussing
district heating, each important part of the design work will
be made as general as possible and will be closed by an
Fig. 111.
DISTRICT HEATING
223
application to the following concrete example which refers
to a certain portion of an imaginary city, Fig. Ill, as avail-
able territory. A city water supply and lighting plant is
located as shown, with lighting and power units aggregat-
img 475 K. W., city water supply pumps aggregating 3000000
gallons maximum capacity, and smaller units requiring ap-
proximately 15 per cent, of the amount of steam used by
the larger lighting units, all as suggested in general instruc-
tions in the problem pamphlet. It is desired to re-design this
plant and to add a district heating system to it; the same to
have all the latest methods of operation and to be of such a
size as to be economically handled. Fig. 118 shows the essen-
tial details of the finished plant.
141. Electrical Output and Exhaust Steam Available for
Heating Purposes from the Po^ver Units: — In the operation
of such a plant, one of the principal assets is the amount of
exhaust steam available for heating purposes. The amount
may be found for any time of the day or night by construct-
ing a power chart as in Fig. 112, and a steam consumption
chart as in Fig. 113. Referring to Fig. 112, the values here
500
400
300,
f5
2009
JOO
1 1 1 1 1 1
PsnKw UNIT
l5nKW UNIT-
m
"MAX TOTAL Kw"
— ^
"
■-
—
—
-•
■-
-
--
—
—
-
POWF
i_iMT5 IN KW
--
--
—
—
—
...
...
—
...
—
—
—
—
—
—
—
—
—
Q «
2 3 4
AM
5 6 7 6
9 iO II 12 1
M
HOURS
234 561 69 10 1
PM
Fig. 112.
12
eiven are assumed, for illustration, to be thase recorded at
the switchboard of the typical plant on a day when heavy
service is required. The curves show that the 75 K. W. unit
runs from 12 P. M. to 7 A. M. and from 6 P. M. to 12 P. M.
with an output of 25 K. W. It also runs from 7 A. M. to 10 A.
224
HEATING AND VENTILATION
M. and from 4 P. M. to 6 P. M. under full load. The 150 K. W.
unit runs from 4 A. M. to 7 A. M. with an output of 100 K. W.
and then increases to 125 K. W. for the entire time until 6 P. M.
when it is shut down. The 250 K. W. unit is started up at 7
A. M. and runs until 6 P. M. under full load, when the load
drops off to 150 K. W. and continues until 10 P. M. when the
unit is shut down, leaving only the 75 K. W. unit running. The
heavy solid line shows all the power curves superimposed
one upon the other. Having given the K. W. output, the gen-
eral formula for determining the horse-power of the engines
is
K. TT. X 1000
/. II. P. = — (66)
'746 X JR X E'
where E and E' are the efficiencies of tlie generator and en-
gine respectively. If we assume the efficiency of the gener-
ator to be 90 per cent., and that of the engine to be 92 per
cent., then formula 66 becomes
7. n. p. =
K. TT. X 1000
746 X .90 X .92
= approx. 1.62 K. TF. (67)
Assuming that the 250 K. TT. unit consumes 24 pounds, the
150 K. W. unit 32 pounds, and the 75 K. W. unit 32 pounds of
steam per /. H. P. hour respectively, when running under
24 a
22 I
P>
on
?{\\
pn
20S
■
?fl
Oflf
2Q
38&
Iflfi,
m
.6-
—
—
—
16 ^
isfinn
—
—
14 '^
12°
,Y
TAM nnN.s
JMPTIDN
lOi
1 nr
T!\
NIP UNITS
eg
—
—
J4
il2.
—
—
—
—
—
=
i!2J
7IP
)
—
—
69
—
—
-fai
—
—
—
—
—
—
—
—
—
4 ^
??
—
149
Q-
—
—
—
—
—
1
—
1-
—
.s^-
—
—
—
—
—
—
— '
—
—
^
—
—
—
12 I 2 3 4 5 6 7
AM
9 10 )l 12 I 2 3 4 5 6 7 8 9 10 II 12
M PM
HOURS
I'ijr. 113.
DISTRICT HEATING
226
normal loads, we have the total steam consumed in the three
units at any time shown by the lower curve in Fig. 113.
The upper curve shows the 15 per cent, added allowance for
smaller units not included in the above list. The values
assumed for efficiencies and the values for steam consump-
tion are reasonable, and may be used if a more exact
figure is not to be had.
It will be seen that the maximum steam consumption in
the generating- units in the power plant is 23100 pounds per
hour and the minimum is 1490 pounds per hour. These two
amounts, then, together with the exhaust steam from the
circulating pumps on the heating system, if a hot water
system is installed, and that from the pumps in the city
water supply, wiill determine .the capacity of the exhaust
steam heaters on the hot water supply and the capacity of
the boilers or economizers to be used as heaters when the
exhaust steam is deficient.
142. Amount of Heat Available for Heating Purposes
in Exliaust Steam, Compared witli That in Saturated Steam
at tlie Pressure of the Exhaust: — To study the effect of ex-
haust steam upon heating problems and to determine, if
possible, the theoretical amount of heat given off wiith
the exhaust steam under various conditions of use, let us
naake several applications: first, to a simple high speed
non-condensing engine using saturated steam; second, to
a compound Corliss non-condensing engine usiing saturated
steam; third, to the first application when superheated
steam is used instead of saturated steam; and fourth, to a
horizontal reciprocating steam pump. Assume the follow-
ing safe conditions. Case one — boiler pressure 100 pounds
gage; pressure of steam entering cylinder 97 pounds gage;
quality of steam at cylinder 98 per cent.; steam consump-
tion 34 pounds per indicated horse-ipower hour; one per
cent, loss in radiation from cylinder; and exhaust pressure
2 pounds gage. Case two — boiler pressure 125 pounds gage;
pressure at high pressure cylinder 122 pounds gage; quality
of steam entering high pressure cylinder 98 per cent.;
steam consumption 22 pounds per indicated horse-power
hour; 2 per cent, loss in radiation from cylinders and re-
ceiver pipe, and exhaust pressure 2 pounds gage. Case
three — same as case one with superheated steam at 150 de-
grees of superheat. Case four — as stated later.
226 HEATING AND VENTILATION
The number of B. t. u. exhausted with the steam, In
any case, is the total heat in the steam at admission, minus
the heat radiated from the cylinder, minus tlie heat ab-
sorbed in actual work in the cylinder.
High speed engine. Case one. — Let r = heat of vaporiza-
tion per pound of steam at the stated pressure, x =■ quality
of the steam at cut-off, q = heat of the liquid in the
steam per pound of steam, and Ws = pounds of steam per
indicated horse-power hour. P^rom this the total number
of B. t. u. entering the cylinder per horse-power hour is
Total B. t u. = Ws ixr + q) (68)
From Peabody's steam tables r = 881, x = .98 and q = 307;
then if Ws = 34, initial B. t. u. = 34 (.98 X 881 + 307) =
39792.92. Deducting the heat radiated from the cylinder
we have 39792,92 X .99 = 39395 B. t. u. per horse-power
left to do work. The B. t. u. absorbed in mechanical work
(useful work + friction) in the cylinder per horse-power
hour is (33000 X 60) -r- 778 = 2545 B. t. u. Subtracting
this work loss we have 39395 — 2545 = 36850 B. t. u. given
up to the exhaust per horse-power hour. Comparing this
value with the total heat in the same weight of saturated
steam at 2 pounds gage, we have 100 X 36850 -=- (34 X
1152.8) = 94 per cent.
Compound Corliss engine. Case two. — With the same terms
as above let r = 867.4, x = .98, q = 324.4, and Ws = 22,
then the initial B. t. u. = 22 (.98 X 867.4 + 324.4) = 25837.9.
Less 2 per cent, radiation loss = 25837.9 X .98 = 25321.14
B. t. u. The loss absorbed in doing mechanical work in the
cylinder per horse-power is, as before, 2545 B. it. u. Sub-
tracting this we have 25321.14 — 2545 = 22776.14 B. t. u.
given up to the exhaust per horse-power hour. Comparing
as before with saturated steam at 2 pounds gage, we have
100 X 22776.14 ^ (22 X 1152.8) = 90 per cent.
Case three. — Now suppose superheated steam be used In
the first application, all other conditions being the same,
the steam having 150 degrees of superheat, what difference
will this make in the result? The total heat entering the
cylinder now is the total heat of the saturated steam at
the initial pressure plus the heat given to it in the super-
heater. Let Cp = specific heat of superheated steam and
DISTRICT HEATING
227
td = the degrees of superheat, then the total heat of the
superheated steam is
Total B. t. u. (sup.) = Ws (xr + q + Cpta) (69)
This for one horse-power of steam (34 pounds), if the
specific heat of superheated steam is .54, will be 34 X .99
X (1188 + .54 X 150) = 42714.5 B. t. u. and the heat turned
into the exhaust will be 42714.5 — 2545 = 40169.5 B. t. u.
Comparing- this with the heat in saturated steam at 2
pounds gage, we have 100 X 40169.5 -i- (34 X 1152.8) = 102
per cent.
Case four. — Pump exhausts are sometimes led into the
Bupply and used for heating purposes along with the engine
exhausts. If such conditions be found, what is the heating
value of such steam? Assume the live steam to enter the
steam cylinder of the pump under the same pressure and
quality as recorded for the high speed engine. The steam
is cut off at about % of the stroke and expands ito the end
of the stroke. With this small expansion the absolute
pressure at the end of the stroke will be approximately
% X 112 = 98 pounds, and if enough heat is absorbed from
the cylinder wall to bring the steam up to saturation at
the release pressure, we will have a total heat above 32
degrees, in the exhaust steam per pound of steam at 98
pounds absolute, of 1185.6 B. t. u. Comparing this with a
pound of saturated steam at 2 pounds gage, we have
100 X 1185.6 -^ 1152.8 = 103 per cent. Under the con-
ditions such as here stated with a high release pressure,
a small expansion of steam in the cylinder and dry steam
at the end of the stroke, it is possible to suddenly drop the
pressure from pump release to a low pressure, say 2 pounds
gage, and have all the steam brought to a state approach-
ing superheat. It is not likely, however, that the steam
is dry at the end of the stroke in any pump exhaust, be-
cause the heat lost in radiation and in doing work in the
slow moving pump would be such as to have a considerable
amount of entrained water with the steam, thus lowering
the quality of the steam. These above conditions are ex-
treme and are not obtained in practice.
From cases one and two it would appear that the
greatest amount of heat that can be expected from engine
exhausts, for use in heating systems at or near the pres-
sure of the atmosphere, is 90 to 94 per cent, of that of
228
HEATING AND VENTILATION
saturated steam at the same pressure. The percentage will,
in most cases, drop much below this value. All things con-
sidered, exhaust steam having 80 to 85 per cent, of the value of
saturated steam at the same pressure is probably the safest rating tchen
ealculating the amount of radiation which can be supplied by the
engines. In many cases no doubt this could be exceeded, but
it is always best to take a safe value. On the other hand,
ichen figuring the amount of condenser tube surface or reheater tube
surface to condense the steam, it would be best to take exhaust steam
at 100 per cent, quality, since this would be working toward
the side of safety.
In plants where the exhaust steam is used for heating
purposes and where the amount supplied by direct acting
steam pumps is large compared with that supplied by the
power units, it is poss«ible to have the quality of the ex-
hausts anywhere between ,800 and 1000 B. t. u. per pound
of exhaust. It should be understood that saturated steam
at any stated pressure always has the isame number of
B. t. u. in it, no matter whether it is taken directly from
the boiler, or from the engine exhaust. A pound of the
mixture of steam and entrained water, taken from engine
exhausts, should not be considered as a pound of steam.
If we are speaking of a pound of exhaust steam without
the entrained water as compared with a pound of saturated
steam at the same pressure, they are the same, but a pound
of engine exhaust or mixture is a different thing.
POWtR HOi»«t
Fig. 114.
DISTRICT HEATING
229
HOT WATER SYSTEMS.
143. Pour General Classifications of hot water heating
may be found in current work, two applying to the conduit
piping system and two to the power plant piping system.
The first, known as the one-pipe complete circuit system, is shown
in Fig. 114. It will be noticed that the water leaves the
power plant and miakes a complete circuit of the district,
as A, B, C, D, E, F, G, through a single pipe of uniform
diameter. From this main are taken branch naains and
leads to the various houses, as a, 6, c and d, e, each one
returning to the principal main after having made its own
minor circuit. The second is known as the two-pipe high
pressure system, in which two main pipes of like diameter
laid side by side in the same conduit, radiate from the
power plant to the farthest point on the line reducing
in size at certain points to suit the capacity of that part
of the district served. This system is represented by Fig.
115. In the one-pipe system the circulation in the various
residences is maintained, in part, by what is known as the
shunt system^ and in part, by the natural gravity circula-
tion. The circulation in the two-pipe system is main-
tained by a high differential pressure between the main
and the return at the same point of the conduit. The force
producing movement of the water in the shunt system is,
therefore, very much less than in the two-pipe system. As a
consequence, the one-pipe system has a lower velocity of the
n
u
-r
&
a
Rower Hou&t
230 HEATING AND VENTILATION
water in the houses and larger service pipes than the two-
pipe system.
In many cases it is desired to connect central heating
mains to the low pressure hot water systems in private
plants. Such connections may easily be made with either
one of the two systems by installing some minor pieces
of apparatus for controlling the supply.
The third and fourth classifications, the open and closed
systems, have about the same meaning as wlien applied to
gravity work in isolated plants. The first is open to the
atmosphere at some point along the circulating system, usu-
ally at the expansion tank which is placed on the return
line just before the circulating pumps. The closed system
presupposes some form of regulation for controlling exces-
sive or deficient pressures without the aid of an expansion
tank. In such cas'cs pumps with automatic control may be
used for taking care of the* reserve supply of water. In the
open system the exhaust steam may be injected directly into
the return circulating water bj^ the use of an open heater
or a com-mingler. The open heater and com-mingler cannot
be used on the pressure side of the pumps. Surface con-
densers or reheaters, heating boilers and economizers may
be used on either open or closed systems.
' 144. Amount of AVater Xeeded per Honr as a Heatlngr
Medium:— All calculations must necessarily begin with the
heat lost at the residence. Referring to the standard room
mentioned in Art. 80, we find the heat loss to be 14000 B. t. u.
per hour, requiring 84 square feet of hot water heating sur-
face to heat the room. Let the circulating water have the
following temperatures: leaving the power plant 180°, enter-
ing the radiator 177°, leaving the radiator 157°, and entering
the power plant 155°. According to tliese figures, which may
be considered fair average values, the water gives off to the
radiator 20 B. t. u. per pound or 166.6 B. t. u. per gallon, thus
requiring 14000 -^ 166.6 = 84 gallons of water per hour to
maintain the room at a temperature of 70°. From this a
safe estimate may be given for design, i. e., each square foot of
hot water radiation in the city mil require approximately one gallon
of water per hour, which in a plant operating under liiigh effi-
ciency may be reduced to 6 pounds per square foot per hour.
It is very certain that some plants are designed to supply
less than one gallon, but In such cases it requires a higher
temperature of the circulating water and allows little chance
DISTRICT HEATING
231
for future expansion of the plant. A drop of 20 degrees,
i. e., 20 B, t. u. heat loss per pound of water passing through
the radiator, is probably the most satisfactory basis. All
things considered, the above italicised statement will satisfy
every condition. (See Art. 173). Having the total number
of square feet of radiation in the district, the total amount
of water circulated through the mains per hour can be
obtained, after which the size of the pumps in the power
plant may be estimated.
145. Radiation in the District: — The amount of radia-
tion that may be installed in the district is problematical. In
an average residence or business district the following fig-
ures may easily be realized: Msiness square, 9000 square feet;
residence square, ^500 square feet. In certain locations these fig-
ures may be exceeded and in others they may be reduced.
Where the needs of the district are thoroughly understood a
more careful estimate can easily be made. It is always well
to make the first estimate a safe one and any possible in-
crease above this figure could be taken care of as in Art.
144. Referring to Fig. Ill, an estimate of the amount of
radiation that may be expected in this typical case, if we
assume ten business squares and twenty-one residence
squares, is 184500 square feet. This will call for the circu-
lation of 184500 gallons of water per hour.
146. Future Increase in Radiation: — From the tempera-
tures given in Art. 144, it will be seen that each pound of
water takes on 25 B. t. u. at the power plant and that there
is a possible increase of 212 — 180 = 32 B. t. u. per pound that
may be given to it, thus increasing the capacity of the system
approximately 125 per cent. It would not be safe to count
on such an increase in the average plant because of a defec-
tive layout in the piping system or because of a low efll-
ciency in some of the pumps or other apparatus in the
plant. If, however, a plant is installed according to the
above figures, the capacity may be quite materially increased
by increasing the temperature of th-e outgoing water at th«
plant to 212°.
147. Tlie Pressure of the Water in the Mains: — The ele-
vation above the plant at which a central station can supply
radiation is limited. Water at 180° will weigh 60.55 pounds
per cubic foot, and the pressure caused by an elevation of 1
foot is .42 pound per square inch. From this the static pres-
232 HEATING AND VENTILATION
sure at the power plant, due to a hydraulic head of 100 feet.
Is 42 pounds per square inch. This value should not be ex-
ceeded, and generally, because of the influence it has on the
machines and pipes toward producing leaks or complete
ruptures, a less head than this is desirable. A static pres-
sure of 42 pounds may be expected to produce, in a well de-
signed plant, an outflow pressure of 65 to 75 pounds per
square inch and a return pressure of 15 to 20 pounds per
square inch, when working under fairly heavy service. In
any case where the mains are too small to supply the radia-
tion in the system properly, we may expect the value given
for the outflow to increase and that for the return to de-
crease. A safe set of conditions to follow is: head, in feet,
60; static pressure, in pounds per square inch, 25; outgoing
pressure at the pumps, in pounds per square inch, 50; return
pressure at the pumps, in pounds per square inch, 5.
This differential pressure .of 45 pounds is caused by the
friction losses in the piping system, pumps and heaters.
Long pipe systems, as these are called, have much greater
friction losses in the long runs of piping than in the ells,
tees, valves, etc., hence, the friction head of the pipes is all
that is usually considered. Where the minor losses are
thought to be large, they may be accounted for by adding
to the pipe loss a certain percentage of itself, say 10 to 20
per cent. Pump power is figured from the differential pressure.
The maximum and minimum pressures in the system are
due to two causes; first, the static head, and second, the
frictional resistances. These extremes of pressure are ap-
proximately — static head plus (or minus) one-half the frictional
resistances. To obtain the frictional resistances, Chezy's for-
mula, 70, is recommended. See Merriman's "A Treatise
on Hydraulics," Arts. 86 and 100, and Church's "Mechanics
of Engineering," Art. 519.
4(t>l r*
hf = X — (70)
d 2«7
where hf = feet of head lost in friction, <f> = friction factor
(synonymous with coefficient of friction". For clean cast
iron pipes with a velocity of 5 to 6 feet per second this
has been found to vary from .0065 to .0048 for diameters
between 3 and 15 inches respectively. .005 is suggested as
a safe average value to use), I = length of pipe in feet,
V = velocity of water in feet per second, d = diameter
of pipe In feet and 2g — 64.4.
I
DISTRICT HEATING
233
Application. — In Fig. 115, let It be desired to find the
differential pressure at the pumps due to the friction losses
in the line A, B, C, D, E. The lengths of the various parts
are: power plant to A, 200 feet; A to B, 500 feet; B to C,
1500 feet; G to D, 1500 feet; and D to E, 500 feet. Assume,
for illustration, that the total radiation in square feet
beyond each of these points is: power plant, 125000; A, 85000;
B, 50000; C, 28000; and D, 12000. This requires 125000, 85000,
50000, 28000 and 12000 gallons of water per hour, or 4.74,
3.27, 1.75, 1 and .44 cubic feet of water per second, respec-
tively, passing these points. Now, if the velocities be
roughly taken at 6 and 5 feet per second, (pipes near the
power plant may be given somewhat higher velocities than
those at some distance from the plant), the pipes will be 12,
10, 8, 6 and 4 inches diameter. In applying the formula to
one part of the line we show the method employed for each.
Take that part from the power plant to A. With v = 6
ht
4 X .005 X 200 X 36
64.4 X 1
2.2 feot.
It should be noted here that formula 70 refers to pipes
where all the water that enters at one end passes out the other.
This is not true in heating mains where a part of the water
is drawn off at intermediate points. On the other hand,
Merriman, Art. 99, explains that a water service main, where
the water is all taken off from intermediate tappings and where
the velocity at the far end is zero, causes only one-third of the
friction given by the above formula. The case under consid-
eration falls somewhere between these two extremes, the part
next the power plant approaching the former and the last
part of the line exactly meeting the conditions of the latter.
Assuming the mean of 'these two conditions, which is
probably very close to the actual, gives two-thirds of 'that
found by the formula. Now since this is a double main
system, i. e., main and return of the same size, the friction
head for the two lines becomes 2.94 feet, from the power
plant to A. In a similar way the other parts may be tried
and the results from the entire line assembled in convenient
form as in Table XXVII.
234
HEATING AND VENTILATION
TABLE XXVIL
Distance between points
Radiation supplied
Volume of water passing
point in cu. ft. per sec...
Velocity f. p. s
Area of pipe sq. ft
Diam. of pipe in ft
hf by (73) for flow main....
hf (taking % value)
hf (% val. flow and return)
P. p.
to A.
AtoB
BtoO
CtoD
200
500
1500
1500
125000
85000
50000
28000
4.74
3.27
1.75
1.
6
6
5
5
.79
.545
.35
.20
1
.83
.66
.5
2.2
6.7
17.4
23.3
1.47
4.47
11.6
15.5
2.94
8.94
23.2
31.0
DtoE
503
12000
.44
5
.087
.33
11.7
7.8
15.6
From the last line of the table we obtain the total
friction head for both mains, not including ells, tees, valves,
etc., to be 81.6 feet. This, is equivalent to 34.3 pounds per
square dnch. Now if we allow about 20 per cent, of all the
line losses to cover the minor losses we have approximately
40 pounds differential pressure, which is a reasonable value.
148. Velocity of the Water in the Mains and the Dia-
meter of the Plains: — The district is first chosen and the
layout of the conduit system is made. This is done inde-
pendently of the sizes of the pipes. When this layout is
finally completed, the pipe sizes are roughly calculated for
all the important p'Oints in the system, and are tabulated
in connection with the friction losses for these parts, as
in Art. 147. When this is done, formula 71, which is rec-
ommended to be used in connection with formula 70, may be
applied and the theoretical diameters found. (The approxi-
mate diameters and the friction heads need not be calcu-
lated in formula 70 for use in formula 71, providing some
estimate may be made for the value of hf, for the various
lengths of pipe. If desired, hf may be assumed without any
reference to the diameter, but this is a rather tedious pro-
cess. For good discussion of this point see Church's Hy-
draulic Motors, Arts. 121-124 b.)
d = .629
[
X
<t>lQ' -\%
hf
(71)
where d, hf, <p and I are the same as in formula 70, ami Q =
cubic feet of water passing through the pipe per second.
This formula differs from those given in the references
stated, in that the term % is inserted as a mvau value be-
DISTRICT HEATING 235
tween the two extreme conditions, as stated in Art, 147.
Application. — Let it be desired to find the diameter for the
single main between the power plant and A, Art. 147, with
hf = 1.47
[
, 2 X.005 X 200 X (4.74)2 "J^s
d = .629 I I = 1 ft. = 12 in.
3 X 1.47 -^
Applying- to the entire line with hf as given in next to last
line of Table XXVII, gives power plant to A, d = 12 inches;
A to B, d = 10 inches; B to C, d = S inches; C to D, d = 6
inches; and D to E, d = 4: inches.
In some cases, when close estimating is not required,
It is satisfactory to assume a velocity of the water and find
the diameter without considering the friction loss. In many
cases, however, this would soon prove a positive loss to the
company. With a low velocity, the first cost would be large
and the operating cost would be low. On the other hand,
if the velocity were high, the first cost would be small and
the operating cost and depreciation would be large. As an
illustration of how the friction head increases in a pipe of
this kind with increased velocity, refer to the run of mains
between B and C. Assuming a velocity of 10 feet per
second, which in this case would be very high, the friction
head, hf, for the single main, becomes 62 and the theoretical
diameter is 5.5, say 6 inches. The friction head, as will be
seen, is 5,4 times the corresponding value when the velocity
was 5 feet per second. Since the pump must work contin-
ually against this head, it would incur a financial loss that
would soon exceed the extra cost of installing larger pipes.
It is found in plants that are in first class operation that
the velocities range from 5 to 7 feet per second.
The calculations in Arts, 147 and 148 are very much
simplified by the use of the chart shown in the Appendix.
In planning a system of this kind, find the friction head
on the pumps and the diameters of the pipes for various
velocities, say 4, 6, 8 and 10 feet per second. Estimate the
probable first cost and the depreciation of the conduit sys-
tem for each velocity, and balance these figures with the
operating cost for a period of, say five years, to see which is
the most economical velocity to use in figuring the system.
149. Service Connections are usually installed from 30
to 36 inches below the surface of the ground, and are in-
sulated in some form of box conduit which compares favor-
236 HEATING AND VENTILATION
ably with that of the main conduit. Service branches are
IM, 1% and 2 inch wrought iron pipe. Tliese are usually
carried to the building- from the conduit at the expense of
the consumer. Such branch conduits are not drained by
tile drains. See Art. 176.
150. Total Steam Available and B. t. u. Liberated per
Hour for Heating the Circulating ^Vate^: — The amount of
steam available for heating the circulating water is that
given off by the generating units, plus that from the cir-
culating pumps, plus that from the city water supply pumps
if there be any, plus that from the auxiliary steam units
in the plant, i. e., small pumps, engines, etc. In the typical
application this amounts to 23100 + 12720 + 8680 = 44500
pounds per hour.
This steam, of course, is not equal to good dry steam in
heating value because of the work it has done in the engine
and pump cylinders, but a good estimate of its value may
be approximated. In addition to the terms used in for-
mula 68, let g' =■ heat in the returning condensation per
pound; then the heat available for heating purposes per
pound of exhaust steam is
B. t. u. = xr + q — q' (72)
It is probably safe to consider the quality of the steam as
85 per cent, of that of good dry steam at tlae same pressure.
Since the pressure of the exhaust from a non-condensing
engine, as it enters the heater, is near that of the atmos-
phere, and since the returning condensation is at a tempera-
ture of about 180°, the total amount of heat given off from
a pound of exhaust steam to the circulating water is
B. t. u. = .85 X 969.7 + 180.3 — (180.3 — 32) = 856, say 850.
If Wi be the pounds of exhaust steam available, the total
number of B. t. u. given off from the exhaust steam per hour is
Total B. t u. = 850 W* (73)
Applying this to the typical power plant gives 850 X
44500 = 37825000 B. t. u. per hour. This amount Is probably
a maximum under the conditions of lighting units as stated,
and would be true for only 5 hours out of 24. At other
times the exhausc steam drops off from the lighting units
and this deficiency must be made good by heating the circu-
lating water directly from the coal, by passing tlie water
through heating boilers or by passing it through economiz-
DISTRICT HEATING 237
ers whe're it is heated by the waste heat from the stack
gases.
151. Amount of Hot Water Radiation in the District
that can be Supplied by One Pound of Bxhaust Steam on a
Zero Day: — In Art. 144, each pound of water takes on 25
B. t. u. in passing- through the reheaters at the power plant,
and gives off at least 20 B. t. u. in passing through the
radiator. The number of pounds of water heated per pound
of steam per hour is, Ww = (Total B. t. u. available per
pound of exhaust steam per hour) -r- 25, and the total radia-
tion that can be supplied is
Total B. t u. available per lb. of exhaust steam per hr.
Ru, = (74)
8.33 X 25
which for average practice reduces to
850
Rv> = == 4 square feet approx. (75)
208
Applying formula 74 for the five hour period when the
exhaust steam is maximum gives Rw = 37825000 -r- 208 =
181851 square feet. It is not safe to figure on the peak load
conditions. It is better to assume that for half the time,
35000 pounds of steam are available and will heat 35000
X 4 = 140000 square feet of radiation.
152. The Amount of Circulating Water Passed through
the Heater Necessary to Condense One Pound of Exhaust
Steam is
Total B. t. u. available per lb. of exhaust steam per hr.
Tfw = (76)
25
With the value given above for the exhaust steam this
becomes, for 100 and 85 per cent, respectively,
(77)
Ww
=
1000
=
40 pounds
25
Ww
850
34 pounds
25
(78)
153. Amount of Hot Water Radiation in the District
that can be Heated by One Horse-Po\%er of Exhaust Steam
from a Non-Condensing Engine on a Zero Day:^
iJic = 4 X (pounds of steam per H. P. hour) (79)
238 HEATING AND VENTILATION
This reduces for the various types of engines, as follows:
Simple high speed 4 X 34 = 136 square feet.
medium " 4 X 30 = 120
Corliss 4 X 26 = 104
Compound high " 4 X 26 = 104
" medium" 4 X 25 = 100
" Corliss 4 X 22 = 88
154. Amount of Radiation that can be Supplied by Bx-
hauMt Steam in Formulas 74 and 75 at any other Temper-
ature of the AV'ater, tu-, than that Stated, with the Room
Temperature, t', Remaining: the Same: — The amount of heat
passing through one square foot of the radiator to the room
is in proportion to tw — f. In formulas 74 and 75, tw — t' =
100, Now if tw be increased x degrees, so that tw — t' =
(100 + x) then each square foot of radiation in the building
100 + X
will give off times more heat than before and
100
each pound of exhaust steam will supply only
4 X 100
Rw = square feet (80)
100 + x
This for an increase of 30 degrees, which is probably a max-
imum, is
4
Rw = = 3 square feet (81)
1.3
Compared with formula 75, formula 80 shows, with a high
temperature of the water entering the radiator, that less
radiation is necessary to heat any one room and that each
square foot of surface becomes more nearly the value of an
equal amount of steam heating surface. Calculations for
radiation, however, are seldom made from high tempera-
tures of the water, and this article should be considered an
exceptional case.
155. ExhauHt Steam Condenser (Reheater), for Reheat-
ing the Circulating >Vater: — In the layout • of any plant
the reheaters should be located close to the circulating
pumps on the high pressure side. They are usually of
the surface condenser type, Fig. 116, and may or may not be
installed in duplicate. Of the two types shown in the fig-
ure, the water tube type is probably the more com,mon. The
same principles hold for each in design. In ordinary heaters
for feed water service, wrought iron tubes of 1% to 2 Inches
DISTRICT HEATING
239
STC,
WATER
M.
3z:
y
y
V
_ 11 ll*
WATELR STUM DRIP
WATLR-TUDt TYPE
Ns
WTEP
Q
u^
frtf
B^
Fig-. 116.
WATLR STLAM
DRIP
STLAM-TUBE TYPE
diameter are generally used, but for condenser work and
where a rapid heat transmission is desired, brass or copper
tubes are used, having diameters of % to 1 inch. In heating
the circulating water for district service, the Teheater is
doing very much the same work as if used on the condens-
ing system for engines or turbines. The chief difference is
in the pressures carried on the steam side, the reheater con-
densing the steam near atmospheric pressure and the con-
denser carrying about .9 of a perfect vacuum. In either case
it should be piped on the water side for water inlet and out-
let, while the steam side should be connected to the exhaust
line from the engines and pumps, and should have proper
drip connection to draw the water of condensation off to a
condenser pump. This condenser pump usually delivers the
water of condensation to a storage tank for use as boiler
feed, or for use in making up the supply in the heating sys-
tem.
In determining the details of the condenser the following
important points should be investigated: the amount of
heating surface in the tubes, the size of the water inlet and
outlet, the size of the pipe for the steam connection, the size
of the pipe for the water of condensation and the length
and cross section of the heater.
156. Amount of Heating Surface in the Reheater Tubes t
— The general formula for calculating the heating surface in
the tubes of a reheater (assuming all heating surface on
tubes only), is
Total B. t. u. given up by the exhaust steam per hr.
Rt = ■ (82)
K (Temp. diff. between inside and outside of tubes)
The maximum heat given off from one pound of exhaust
steam In condensing at atmospheric pressure is 1000 B. t. u.,
the average temperature difference is approximately 47
degrees, and K may be taken 427 B. t. u. per degree dlf-
240 HEATING AND VENTILATION
ference per hour. In determining K, it is not an easy mat-
ter to obtain a value tiiat will be true for average practice.
Carpenter's H. & V. B, Art. 47 quotes the above figure for
tests upon clean tubes, and volumes of water less than
1000 pounds per square foot of heating surface per hour.
It is found, however, that the average heater or condenser
tube with its lime and mud deposit will reduce the efficiency
as low as 40 to 50 per cent, of the maximum transmission.
Assume this value to be 45 per cent.; then if Ws is the
number of pounds available exhaust steam, formula 82
becomes
1000 Wm 1000 W, 1000 W, W,
Rt = = = = (83)
K iU—tw) 427X.45X47 9031 9.1
In "Steam Engine Design," by Whitham, page 283, the
following formula is given for surface condensers used on
shipboard:
W L
8 =
cK (Ti — t)
where 8 = tube surface, W = total pounds of exhaust steam
to be condensed per hour, L = latent heat of saturated steam
at a temperature Ti, K = theoretical transmission of B. t. u.
per hour through one square foot of surface per degree dif-
ference of temperature = 556.8 for brass, c = efficiency of
the condensing surface = .323 (quoted from Isherwood). Ti =
temperature of saturated steam in the condensers, and * =
average temperature of the circulating water.
With L = 969.7, c = .323, K = 556.8 and Ti — t = 47, we
may state the formula in terms of our text as
969.7 Ws 969.7 W, T7,
Rt = = = • (84)
.323X556.8X47 8446 8.7
In Sutcliffe "Steam Power and Mill Work," page 512. the
author states that condenser tubes in good condition and set
in the ordinary way have a condensing power equivalent to
13000 B. t. u. per square foot per hour, when the condensing
water is supplied at 60 degrees and rises to 95 degrees at dis-
charge, although the author gives his opinion that a trans-
mission of 10000 B. t. u. per square foot per hour is all that
should be expected. This checks closely with formula 83,
which gives the rate of transmission 9031 B. t. u. per squarf
foot per hour.
DISTRICT HEATING
241
The following empirical formula for the amount of heat-
ing surface in a heater is sometimes used:
Rt = .0944 Ws (85)
where the terms are the same as before.
Application. — Let the total amount of exhaust s-team avail-
able for heating the circulating water be 35000 pounds per
hour, the pressure of the steam in the condenser be atmos-
pheric and the water of condensation be returned at 180";
also, let the circulating water enter at 155° and be heated to
180°. These values are good average conditions. The as-
sumption that the pressure within the condenser is atmos-
pheric might not be fulfilled in every case, but can be ap-
proached very closely. From these assumptions find the
square feet of surface in the tubes.
Formula 83, Rt =
Formula 84, Rt =
35000
9.1
35000
8.7
= 3846 sq. ft.
= 4023 sq. ft.
.Formula 85, Rt = 35000 X .0944 = 3304 sq. ft.
1000 X35000
iSutclifCe
Rt =
10000
= 3500 sq. ft.
If 3846 square feet be the accepted value it will call for
three heaters having 1282 square feet of tube surface each.
157. Amount of Reheater Tube Surface per Engrine
Horse-Poifver : — Let ws be the pounds of steam used per
/. H. P. of the engine; then from formula 83
Ws
Bt (per /. H. P.) = (86)
9.1
This reduces for the various types of engines as follows:
Simple high speed 34 -r- 9.1 = 3.74 square feet
'• medium " 30 -r- 9.1 = 3.30
" Corliss 26
Compound high
" medium
" Corliss
25
9.1 = 2.86
26 -i- 9.1 = 2.86
9.1 = 2.75
22 -T- 9.1 = 2.42
158. Amount of Hot Water Radiation in the District
that can be Supplied by One Square Foot of Reheater Tube
Surface: — If the transmission through one square foot of
tube surface be K iU — tw) = 9031 B. t. u. per hour and the
242 HEATING AND VENTILATION
amount of heat needed per square foot of radiation per
hour = 8.33 X 25 = 208, as given in formula 74, then
9031
Rw (per sq. ft. of tube surface) = = 43.4 sq. ft. (87)
208
159. Some Important Reheater Details: — Inlet and outlet
pipes. — Having three heaters in the plant, it seems rea-
sonable that each heater should be prepared for at least one.
third of the water credited to the exhaust steam. From
Art. 151 this is 140000 -h 3 = 46667 gallons = 10800000 cubic
inches per hour. The velocity of the water entering and
leaving the heater may vary a great deal, but good values
for calculations may be taken between 5 and 7 feet per
second. Assuming the first value given, we have the area
of the pipe = 10800000 -=- (5 X 12 X 3600) = 50 square inches,
and the diameter 8 inches.
The size of the reheater shell. — Concerning the velocity
of the water in the reheater itself, there may be differences
of opinion; 100 feet per minute will be a good value to use
unless this value makes the length of the tube too great for
its diameter. If this is the case the tube will bend from
expansion and from its own weight. At this velocity the
free cross sectional area of the tubes, assuming the water
to pass through the tubes as in Fig. 116, will be 150 square
inches. If the tubes be taken % inch outside diameter,
with a thickness of 17 B. W. G., and arranged as usual in
such work, it will require about 475 tubes and a shell diam-
eter of approximately 30 inches. If the inner surface of the
tube be taken as a measurement of the heating surface and
the total surface be 1282 square feet, the length of the re-
heater tubes will be approximately 16 feet.
The ratio of the length of the tube to the diameter is,
in this case, 256, about twice as much as the maximum ratio
used by some manufacturers. It will be better, therefore,
to increase the number of tubes and decrease the length.
With a velocity of the water at 50 feet per minute, the
values will be approximately as follows: free cross sec-
tional area of the tubes, 300 square inches; number of tubes,
950; diameter of shell, 40 inches; length of tubes, 8 feet.
These values check fairly well and could be used.
The size of exhaust steam eonnection. — To calculate this, use
the formula
144 Q,
A = (88)
DISTRICT HEATING
243
where Q* = volume of steam in cubic feet per minute, T =
velocity in feet per minute, and A = area of pipe in square
inches. When applied to the reheater using 35000 pounds
of steam per hour, at 26 cubic feet per pound and at a veloc-
ity through the exhaust pipe of 6000 feet per minute, it gives
A =
144 X 35000 X 26
= 360 sq. in = 22 in. dia.
60 X 6000
Try also, from Carpenter's H. & V. B., page 284
d = V ■
1.23 (89)
Allowing 30 pounds of steam per H. P. hour for non-condens-
ing engines we ihave 35000 -^- 30 = 1166 horse-power; then
applying the above we obtain (Z = 16 inches. Comparing
the two formulas, 88 and 89, the first will probably admit of
a more general application. The velocity 6000 for exhaust
steam may be increased to 8000 for very large pipes and
should be reduced to 4000 for small pipes. In the above
applications a 20 inch pipe will sufliice.
The return pipe for condensation. — The diameter of the pipe
leading to the condenser pump will naturally be taken from
the catalog size of the pump installed. This pump would
be selected from capacities as guaranteed by the respective
manufacturers and should easily be capable of handling the
amount of water that is condensed per hour.
The value of a high pressure steam connection. — If desired,
the reheater may also be provided with a high pressure
steam connection, to be used when the exhaust steam is not
sufficient. This steam is then used through a pressure-re-
ducing valve which admits the steam at pressures varying
from atmospheric to 5 pounds gage. There is some question
concerning the advisability of doing this. Some prefer to
install a high pressure steam heater, as in Art. 160, to be
used independently of the exhaust steam heaters. This
removes all possibility of having excessive back pressure
on the engine piston, as is sometimes the case where high
pressure steam is admitted with the exhaust steam.
It has been the experience of some who have operated
such plants that where more heat is needed than can be
supplied by the exhaust steam, it is better to resort to heat-
ing boilers and economizers, than to use high pressure steam
for heating.
244
HEATING AND VENTILATION
160. Hleh Pressure Steam Heater: — When this heater Is
used it Is located above the boiler so th<at all the condensa-
tion freely draios back to the boilers by gravity as in Fig.
117. In calculating the tube surface, use formula 82 with
the full value of the steam and the steam temperatures
changed to suit the increased pressure. Such a heater as
this gives good results.
Fig. 117.
161. Circulating Pumps: — Two type& of pumps are In
general use: centrifugal and reciprocating. Each type is
somewhat limited in its operation. The centrifugal pump
has difficulty in operating against high heads and the recip-
rocating pump is very noisy when running at a high piston
speed. Since each type is in successful operation in many
plants, no comparisons will be made between them further
than to say that the former, being operated by a steam en-
gine, may be run more economically than the latter because
of the possibilities of using the steam expansively. It will
DISTRICT HEATING 245
be noted, however, that this same steam is to be used in the
exhaust steam, heaters for warming' the circulating- water
and hence there would be little, if any, direct loss from this
source in the use of the reciprocating pump.
Having given the maximum amount of water to be
circulated per hour, consult trade catalogs and select the
number of pumps and the size of each pump to be installed.
The sizes of the pumps oan easily be determined when the
number of them has been decided upon. This latter point
is one upon which a difference of opinion will probably be
found. No exact rule can be applied. In a plant of, say
not more than 150000 square feet of radiation (150000 gal-
lons of water per hour, or 3 million gallons for twenty-four
hours), some designers would put in three pumps, each
having 1.5 million gallons capacity; in which case one pump
could be cut out for repairs and the other two would be
able to care for the service temporarily. Other designers
would use four pumps at about one million gallons each.
The fewer the pumps installed, in any case, the greater
should be the capacity of each. The following values will
be found fairly satisfactory:
1 Pump. Cap. = (1 to 1.25) times max. requirem't of system
2 Pumps. " (each) = .75
3 Pumps. " " = .5
4 Pumps. " " = .3
Having given the capacity of each pump in gallons of
water per minute, the size, the horse-power and the steam
consumption of each pump can be calculated. In obtaining
the size of the pump it will be necessary to know the speed,
V, of the piston in feet per minute, the strokes, N, per minute
and the per cent, of slip, s (100 per cent. — S, where 8 = hy-
draulic efficiency). The speed varies between 100, for small
pumps, and 75, for large pumps. The strokes vary between
200, for small pumps, and 40, for large pumps, and the slip
varies between 5 and 40 per cent., depending upon the fit of
the piston and. the valves. In pumps that have been in serv-
ice for some time the slip will probably average 20 per cent.
The cross sectional area of the water cylinder in square
Inches is
cubic inches pumped per minute
W. C. A. (90>
>8 X F X 12
246 HEATING AND VENTILATION
from which we may obtain the diameter of the water cyl-
inder.
The steam cylinder area is usually figured as a certain
ratio to that of the water cylinder area, as
S. C. A. = (1.5 to 2.5) X TT. C. A. (91)
from which we may obtain the diameter of the steam cylin-
der.
The length of the stroke, L, in inches, may be obtained
from the speed and the number of strokes such that
12 y
L = (92)
N
All direct acting steam pumps are designated by diam-
eter of steam cylinder X diameter of water cylinder X length
of stroke, as
14" X12" X 18"
Duplex pumps have twice the capacity of single pumps
having the same sized cylinders.
To find the indicated horse-power, I. n. P., of the pumps,
reduce the pressure head, p, in pounds per square inch, to
pressure head in feet, 7i; multiply this by the pounds of
water, W, pumped per minute and divide the product by
33000 times the mechanical efflciency, E.
W h
/. E. P. = (93)
33000 E
To reduce from pressure head in pounds to pressure
head in feet, divide the pressure head in pounds by weight
of a column of water one square inch in area and one foot
nigh. The general equation for this is
144 p
h =
where to = the weight of a cubic foot of water at the given
temperature and p = differential pressure in pounds per
square inch.
In pump service of this kind the pressure head, p.
against which the pump is acting, is not the result of the
static head of water in the system but is due to the inertia
of the water and to the resistance to the flow of water
DISTRICT HEATING 247
through the piping system and the heaters. This frictional
resistance may be calculated as shown in Art. 147. Read
this part of the worlc over carefully.
For an illustration of combined pressure head, p, and
friction head, fif, see Art. 164 on boiler feed pumps. Having
found the /. H. P. of any pump, multiply it by the steam con-
sumption per /. H. P. hour and the result will be the steam
consumption of the pump. This exhaust steam will be con-
sidered a part of the general supply when figuring the size
of the exhaust steam heaters in the system.
The mechanical efficiency, E, of- piston pumps depends
upon the condition of the valves and upon the speed, and
varies from 90 per cent, in new pumps, to 50 per cent, in
pumps that are badly worn. A fair average would be 70
per cent.
The steam consumption for reciprocating, simple and
duplex non-condensing pumps would approximate 100 to
200 pounds of steam per /. H. P. hour — the greater values re-
ferring to the slower speeds.
162. Centrifugal Pumps: — Centrifugal pumps are of
two classifications, the Volute and the Turbine. The prin-
ciples upon which each operate are very similar. The ro-
tating impeller, or rotor, with curved blades draws the
water in at the center of the pump and delivers it from the
circumference. The rotor is enclosed by a cast iron case-
ment which is shaped more or less to fit the curvature of
the edges of the blades on the rotor. Centrifugal pumps
are used 'where large volumes of water are required at low
heads. They are used in city water supply systems, in cen-
tral station heating systems, in condenser iservice, in irri-
gation work and in many other places where the pressure
head operated against is not excessive. The efficiency of
the average centrifugal pump is from 65 to 80 per cent.,
75 per cent, being not uncommon. In places where such
pumps are used the head is usually below 75 feet, although
some types, when direct connected to high speed motors,
are capable of operating against heads of several hundred
feet.
(Some of the advantages of centrifugal pumps over hor-
izontal ireciprocating pumps are: low first cost, simplicity,
few moving parts, compactness, uniform flow and pressure
of water, freedom from shock, possibilities of direct connec-
.
248 HEATING AND VENTILATION
tion to high speed motors and the ability to handle dirty
water without injuring the pump.
One of the advantages of piston pumps over centrifugal
pumps is the fact that they are more positive in their
operation and work against higher heads.
Centrifugal pumps, when connected to engine and tur-
bine drives, benefit by the expansion of the steam and are
much more economical than the direct acting piston pump,
which takes steam at full pressure for nearly the entire
stroke. The amount of steam used in the pumps in central
station work, however, is not a serious factor, since all of
the heat in the steam that is not used in propelling the
water through the mains is used in -the heaters to increase
the temperature of the water.
The sphere of usefulness of the centrifugal pump in
central station heating is incre-asing. The direct acting
piston pump, when operating at fairly high speeds, causes
hammering and pounding in ithe transmission lines, and
these noises are sometimes conveyed to the residences and
become annoying to the occupants. This feature is not so
noticeable in the operation of the centrifugal pump.
Application. — In Art. 145 assume the capacity of the plant,
10 business squares and 21 residence squares, to require
184500 gallons of water per hour; the same to be pumped
against a pressure head, Art. 147, of 50 — 5 pounds, by
horizontal, direct acting piston pumps. Assume also the
s-team consumption of 'the pumps to be 100 pounds per /. H. P.
hour and the average temperature of the water at the
pumps to be (180 + 155) -=- 2 = 167.5 degrees. Apply for-
mula 93, where h = calculated total friction head for the
longest line in the system (this is designated by hf in Art.
147), or where p = total difference between the incoming
and the outgoing pressures. With the weight of a cubic
foot of water at 167.5 degrees = 60.87 pounds and with
p = 45, we have h = 106.5 feet, and the indicated horse-power
of the pumps, assuming 65 per cent, mechanical efficiency, is
184500 X 8.33 X 106.5
/. H. P. = = 127.2
33000 X .65 X 60
From this the steam consumption will probably be 12720
pounds per hour.
If centrifugal pumps were selected, the horse-power
would be calculated from the same formula, but the steam
DISTRICT HEATING 249
consumption would probably be 30 to 40 pounds of steam
per horse-power hour because of the expansive working of
the steam.
163. City W«ter Supply Pumps; — Horizontal, direct act-
ing duplex pumps for use on city water supply service are
the same as those used to circulate the water in heating
systems; hence, the foregoing descriptions apply here. The
/. H. P. of the city water supply pumps would be calculated
by use of formula 93. If the pumps lifted the water from
the wells, as would probably be ithe case, the suction pres-
sure would be negative and would be added to the force
pressure.
Application. — ^Assume the pressure in the fresh water
mains 60 pounds and the suction pressure 10 pounds;
therefore, p = 60 — ( — 10) ■= 70 pounds, and with the water
at 65 degrees, h — 144 X 70 -f- 62.5 = 161 feet. These pumps
are each rated at 1.5 million gallons in 24 hours, and deliver
62500 X 8.33 = 520833 pounds of water per hour, when run-
ning at full capacity. Assuming each pump to deliver 75 per
cent, of the full requirement of the sys/tem, .the total amount
of water pumped per hour for the city water supply would
approximate 520833 -H .75 = 694444 pounds, and the total
average horse-power used in pumping the water would be
694444 X 161
I. E. P. = = 86.8
60 X 33000 X.65
With 100 pounds of steam per horse-power hour, this would
amount to 8680 pounds of steam available per hour for use
in heating the circulating water.
164. Boiler Peed Pumps: — Horizontal pumps for high
pressure boiler feeding are selected in a similar way to the
circulating pumps for the city water supply. Such units
are called auxiliary steam units and, because the steam re-
quired is small, they are sometimes piped to a feed water
heater for heating the boiler feed. The velocity 'Of the water
through the suction pipe is about 200 feet per minute and
in the delivery pipe about 300 feet per minute. The piston
speed, the strokes per minute and the slip would be very
much the same as stated under circulating pumps. Such
pumps should have a pumping capacity about itwice as great
as the actual boiler requirements, and in small plants where
only one pump is needed, the installation should be in
250 HEATING AND VENTILATION
duplicate. The sizes of the cylinders and the efficiencies are
about as stated for the larger circulating pumps.
In determining the horse-power of a boiler feed pump,
four resistances must be overcome; i. e., pressure head, p.
or boiler pressure; suction head, h$; delivery head, hd; and
the friction head, hf. The first three values are usually
given. The friction head includes the resistances in all pip-
ing, ells and valves from the supply to the boiler. The fric-
tion in the piping may be taken from Table 37, Appendix, or
it may be worked out by formula 70. The friction in the ells
and valves is more difficult to determine and is usually stated
in equivalent length of straight pipe of the same diameter.
A rough rule used by some in such cases is as follows:
"to the length of the given pipe, add 60 times the nominal
diamete-r of the pipe for each ell, and 90 times the diameter
for each globe valve," then find the friction head as stated
above. A straight flow gate or water valve could safely be
•taken as an ell. For simplicity of calculation, all of the
above resistances may be reduced to an equivalent head,
such that
144 p
he = + hd + ht -{- hf (94)
where io = weight of one cubic foot of water at the suc-
tion tempeirature, w may be obtained from Table 8, Ap-
pendix, and hf may be taken from Table 37. The horse-power
by formula 93 then becomes, if TF = pounds of water pumped
per minute,
W X he
I. H. P. = (95)
33000 -B
Application. — Let p = 125 pounds gage, w = 62.5, ftd = 8
feet, h$ = 20 feet, horizontal run of pipe from supply to
pump = 20 feet, horizontal run of pipe from pump to boiler
= 30 feet; also, let the pump supply 89000 pounds of water
per hour to the boiler. This is twice the capacity of the
boiler plant. With this amount of water at the usual veloc-
ity it will give a suction pipe of 4.5 inches diameter, and a
flow pipe of 4 inches diameter. Let there be two ells and
one gate valve on .the suction pipe, and three ells, one globe
valve and one check valve on the delivery pipe. We then
have an equivalent of 107 feet of suction pipe, and lf^8 feet
of delivery pipe. Referring to Table 37, hf is approxi-
mately 7 feet, and the total head is
DISTRICT HEATING 251
144 X 125
^« = [- 8 + 20 + 7 = 323 feet.
62.5
In most boiler feed pumps it is considered unnecessary
to determine hf so carefully. A very satisfactory way is to
obtain the total head pumped against, exclusive of the
friction head, and add to lit 5 to 15 per cent,, depending
upon the complications in the circuit. Substituting th«
above in formula 95, we obtain
89000 X 323
/. U. P. = = 22.3
60 X 33000 X .65
Work out the value of hf by formula 70 and see how
nearly it checks with the above..
165. Boilers: — A number of boilers will necess^arily be
installed in a plant of th'«* kind, and a good arrangement is
to have them so piped with water and steam headers that
any number of the boilers may be used for steaming pur-
poses and the rest as water heaters. They should also be so
arranged that any of the boilers may be thrown out of
service for cleaning or repairs and still carry on the work
of the plant. By doing this the boiler plant becomes very
flexible and each boiler is an independent unit. Any good
water tube boiler would serve the purpose, both as a steam-
ing and as a heating boiler. Where the boilers are used as
heaters, the water should enteT at the bottom and come out
at the top. Where the water enters at the top and comes
out at the bottom, the excessive heating of the front row of
tubes retards the circulation of the water by ithis heat, and
produces a rapid circulation through the rear tubes where the
heat is the least. This rapid circulation in the rear tubes is
not a detriment, but it is less needed there than in the front
ones. It would be decidedly better if the rapid circulation were
in the front row, causing the heat from the fire to be carried
off more readily, and by this means giving less danger of
burning the tubes. In the latter case the forced circulation
from the pumps will be aided by the natural circulation
from the heat of the fire, and the life of all the tubes then
becomes more uniform. Fig. 118 shows a typical header
arrangement.
Boilers are usually classified as fire tube and water tube.
Fire tuhe hoiUrs are usually of the multitubula.r type, having
the flue gases passing through the tubes and water sur^
252 HEATING AND VENTILATION
rounding them. Water tube boilers have the water passing-
through the tubes and the flue gases surrounding tliem.
The heating surface of a boiler is composed of those boiler
plates having the heated flue gases on one side and the water
on the other. A boiler horse-poiccr may be taken as follows:
Centennial Rating.
One B. H. P. = 30 pounds of water evaporated from feed
water at 100° F. to steam at 70 pounds gage pressure.
A. S. M. E. Rating.
One B. H. P. = 34.5 pounds of water evaporated from
and at 212' F.
In laying out a boiler plant some good approximations
for the essential details are:
One B. H. P. = 11.5 square feet of heating surface
(multitubular type).
One B. H. P. = 10 square feet of heating surface
(water tube type).
One B. H. P. = .33 square foot of grate surface
(small plant, say one boiler).
One B. H. P. = .25 square foot of grate surface
(medium sized plant, say 500 H. P.).
One B. H, P. = .20 square foot of grate surface
(large plants).
Pounds of water evaporated per square foot of heating
surface per hour = 3 (approx, value).
166. Square Feet of Hot AVater Radiation that can be
Supplied on a Zero Day by One Boiler Horse-Po^ver vrhen the
Boiler is Used as a Heater: — Assuming that the coal us^ed in
the plant has a heating value of 13000 B. t. u. per pound,
and that the efficiency of the boiler is 60 per cent., each
pound of coal will transmit to the water 7800 B. t. u. Since
each pound of water takes up 25 B. t, u. on its passage
through the heating boiler, one pound of coal will heat 312
pounds, or 37.5 gallons of water. This is equivalent to
supplying heat, under extreme conditions of heat loss, to
37.5 square feet of radiation for one hour. One boiler horse-
power, according to Art. 165, is equivalent to the expendi-
ture of 969.7 X 34.5 = 33455 B. t. u. Now since each pound
of coal transfers to the water 7800 B. t. u., one boiler horse-
power will require 33455 4- 7800 = 4.28 poumls of coal. If,
then, the burning of one pound of coal will supply 37.5
square feet of hot water radiation for one hour, one boiler
DISTRICT HEATING 253
horse-power will supply 4.28 X 37.5 = 160 square feet for one
hour, and a 100 H. P. boiler will supply 16000 square feet
of water radiation in the district for the same time. These
fig-ures have reference to boilers under good working con-
ditions and probably give average results.
167. Square Feet of Hot AVater Radiation in the District
that can be Supplied on a Zero Day by an E^conoinizer Lo-
cated in the Stack Gases bet^^een the Boilers and the Chim-
ney; — In order to make this estimate it is necessary first to
know the horse-power of the boilers, the amount of coal
burned per hour, the pounds of gases passing through the
furnace per hour and the heat given off from 'these gases
to the circulating water through the 'tubes.
Application. — Let C = pounds of coal burned per hour =
boiler ho-rse-power X pounds of coal per boiler horse-power
hour, Wa = pounds of air passed through the furnace per
pound of fuel burned, s ^= specific heat of the gases, U = tem-
perature of gases leaving boiler, ts = temperature of gases
leaving economizer, tw = temperature of water entering
economizer and tf = temiperature of w^ater leaving the econo-
mizer. Then, if 8.33 pounds of water will supply one square
foot of radiation for one hour we have
SX (GXWa+C) X(tb — ts)
Rm> = (96)
8.33 X (tf — tw)
Prom a previous statement, 44500 pounds of steam per
hour are generated in the steam boiler plant at a pressure
of 125 pounds gage. To find the boiler horse-power let the
total heat of the steam, above 32° at 125 pounds gage, be
1191.8 B. t. u., and let the temperature of the incoming feed
water to the boilers be 60 degrees. (In mos't cases the feed
water will be at a higher temiperature, but s'ince it will occa-
sionally be as low as 60 'degrees, this value will be a fair
one.) The heat put into a pound of steam under these con-
ditions is 1191.8 — (60 — 32) = 1163.8 B. t. u., and in 44500
pounds it will be 51789100 B. t. u. Since one horse-ipower of
boiler service is equivalent to 33455 B. t. u., we will need
51789100 -^ 33455 = 1548 boiler horse-power. This horse-
power will take oare of all the engines and puimps im the
plant. If the coa'l used contains 13000 B. t. u. per pound
and the boilers have 60 per cent. efl[iciency, then 7800 B. t. u.
Will be given to the water per pound of fuel burned, and
254 HEATING AND VENTILATION
the amount of coal burned per hour will be 51789100 -;- 7800
= 6640 pounds. This gives 6640 -H 1548 = 4,3 pounds of fuel
per boiler horse-power hour, and 6.7 pounds of water evap-
orated per pound of fuel. If the flue gases have 12 per cent.
OO2, there are used acco^rding to expenimental data, about
21 pounds of air or 22 pounds of the gases of combustion,
per pound of fuel burned. This is equivalent to 6640 X 22
= 146080 pounds of flue gases total. Suppose now tliat these
gases leave the furnace for the chimney at a temperature
of 550 degrees F., that the economizer drops the tempera-
ture of the gases down to 350 degrees (a condition which is
very reasonable) and that the specific heat of the gases is
about .22, we have 146080 X .22 X (550 — 350) = 6427520
B. t. u. given off from the gases per hour in passing through
the economizer (see numerator in formula 96). This heat
is taken up by the circulating water in passing through the
economizer toward the outgoing main. Now if the water,
as it returns from the circulating system, enters the econo-
mizer at 155 degrees, and leaves at 180 degrees, we will have
6427520 -^ (180 — 155) = 257100 pounds of water heated per
hour. This is equivalent to supplying 257100 -^ 8.33 = 30864
square feet of radiation per hour when the plant is running
at its peak load. Taking the "pounds of steam per hour" in
the above as the only variable quantity, we are fairly safe
in saying that the heat in the chimney gases from one horse-
power of steaming, boiler service will supply, through an
economizer, 30864 -¥■ 1548 = 20 square feet of radiation in the
district. In plants where only 7 pounds of water are allowed
to each square foot of radiation per hour, this becomes 23.8
square feet of radiation instead.
168. Square Feet of Kcononilzer Surface Required to
Heat the Circulating Water In Art. l«7:.^Let A' = the coeffi-
cient of heat transmission through clean cast iron tubes and
E = the efficiency of the tube surface when in average serv-
ice, also let the terms for the temperatures of the gases
and the circulating water be as given in Art. 167, then
Heat trans, per hour from gases to water
Re = (97)
rib + ts tf + tw
)
This formula assumes that the rate of heat flow through
the tubes l.s the same at all points. As a matter of fact this
rate changes slightly as the water becomes heated, but
DISTRICT HEATING 255
the error is not worth mentioning in such a formula, where
the efficiency of the surface may be anything from 100 per
cent. In new tubes, to as low as 30 or 40 per cent, for old
ones.
Applicatiox, — Let K =^ 1 and E = A, then
6427520
Re = = 8125 sq. ft.
/ 550 + 350 180 + 155 \
,X.4X( ^— )
With 12 square feet of surface per tube this gives 677 tubes.
169. Square Feet of Economizer Surface to Install -when
the Economizer is to be Used to Heat the Feed Water for
the Steaming Boilers: — If 30 pounds of feed water are fed
to the boiler per ihorse-power hour, and it K = 7, E = .4,
tb = 550, U = 350, tf = 250, and tw = 90 (about the lowest
temperature at which water should enter the economizer),
then the square feet of surface per horse-power is
30 X (250 — 90)
Re = = 6.1 sq. ft.
/ 550 + 350 250 + 90 \
7 X .4 X ( )
V 2 2 /
170. Total Capacity of the Boiler Plant and the Xumber
of Boilers Installed: — The following discussion on the size
of the boiler plant is purely for illustrative purposes and
is intended to show how such problems may be analyzed.
In most cases the exhaust steam, and the economizer, if used,
wil'l fall far short of supplying the total radiation in the
district, especially when the electrical output is light and
the weather is cold. Suppose it be desired to install extra
boilers to be used as heaters for the radiatlion not 'supplied
from these two sources. To determine the amount of ex-
tra boilers, find 'the amount of radiation to be supplied by
the exhaust steam and the economizer and subtract this
from the total radiation. The difference musit be supplied
by boilers used as heaters. It is probably not safe to esti-
mate too closely on the amount of exhaust steam given to
the heating system. The maximum amount of 44500 pounds
per hour was obtained, in this case, by pumping one gal-
lon of water per hour for each square foot of radiation and
by pumping city water, in addition ta that obtained from
the engines. In heating, a less amount of water than this
miay be circulated even on the coldest day. This is possi-
ble, first, because water may be carried at a higher tern-
256 HEATING AND VENTILATION
perature than that stated, and second, because there may
be less loss of heat in the conduit, thus giving more heat per
giallon of water to the radiation. Again, in estimating for
a city water supply, the demands are not very constant and
are difficult to estimate. In this one design it was "thought
that 44500 pounds per hour was a very liberal allowance
and could be dropped to 35000 pounds (140000 square feet
of radiation), when estimating the amount of radiation
supplied by the exhaust steam.
By Fig. 113 it will be seen that the minimum load on the
steaming boilers carries through six hours out of the entire
twenty-four and that the exhaust steam at this time drops
to 22890 pounds per hour, supplying 91560 square feet of
radiation. This minimum load is 51 per cent, of the max-
imum, and 66 per cent, of the amount taken as an average,
i. e., 35000. The work done by the economizer is fairly con-
stant, since the amount of economizer surface lost by the
steaming boilers under minimum load would be made up
by the additional heating boilers thrown into service. On
the basis of 35000 pounds per hour, the exhaust steam and the
stack gases together would heat 170960 square feet and
there would be left 13540 square feet (184500 — 20 X 1548
— 4 X 35000), to be heated by additional boilers. Under
minimum load this would be approximately 122500, leaving
62000 square feet to be heated by additional boilers. If one
boiler horse-power supplies 160 square feet of radiation,
then it would require 84 and 387 boiler horse-power re-
spectively to supply the deficiency and the total horse-power
needed in each case would be 1632 and 1935. A more satis-
factory analysis, however, is the following which is worked
on the basis of 44500 pounds per hour.
Let Wi = total number of pounds of steam used In the
plant per hour = approximate number of pounds of exliaust
steam available for heating the circulating water per hour;
We = equivalent number of pounds of steam evaporated from
and at 212°; \ = total heat, above 32°, in one pound of dry
steam at the boiler pressure; q' = total heat, above 32°, in
one pound of feed water entering the boiler; then, if the
latent heat of steam at atmiospheric pressure = 969.7 B. t. u.,
we have
TF. (\ — (t)
We = (98)
969.7
DISTRICT HEATING
257
and the corresponding boiler horse-power needed as steam-
ing boilers will be
We
Bs. H. p. = (99)
34.5
Next, the radiation in the district that can be supplied
by the exhaust steam is Rw = 4 Ws, and the amount sup-
plied by the economizer is Re = 20 X B. H. P. From which
we may obtain the capacity of the heating boilers, as
Bw. H. P. =
Total Radiation — 4 TF*
20 B. H. P.
160
(100)
The total boiler horse-power of the plant is, therefore, the
sum of Bs. H. P. and Bw. U. P. To obtain formula 100 for any
specific case one must consider the maximum and minimum
comdlitions of the steaming boiler plant. Let Ws (max) =
miaximum exhaust staam, and Ws (min) = minimum exhaust
steam. Then for the two following conditions we have,
Case 1, where the steaming and heating toilers are independent of
each other, the total boiler horse-power installed = Bs. H. P.
+ [total radiation — 4 TF* (min) — 20 X 5. H. P. in use] -r-
160. Also, Case 2, where a part or all of the steaming boilers are
piped for both steaming and water service, the total boiler horse-
power installed = Bs. E. P. + [total radiation — 4 Ws (max)
— 20 X B. H. P. in use] ^ 160. It will be noticed that ithe last
term representing the economizer iservioe is simply stated
as boiler horse-power and no distinction is made between
steaming or heating service. This term is difficult ito esti-
mate to an exact figure because it should be the total horse-
power in use at any one time, both steamdng and heating,
and this can only be obtained by approximation. It makes
no difference wbat service the boiler may be used for, the
work of the economizer is practically the same. Probably
the most satisfactory way is to substitute the value of
Bs. H. P. for B. H. P. in the economizer and get the approxi-
mate total horse-power, then if this approximate total horse-
power (differs very much from that actually needed, other
trials may be made and new values for the total horse-power
obtained until the equation is satisfied.
268 HEATING AND VENTILATION
Application. — Let TT. = pounds of exhaust sleam, X =
1191.8 (125 pounds ga.go pressure), and q' = 28 (feed water
at 60""); then when W. = 44500
. We = 53400
Bm. H. p. = 1548
184500 — 4 X _- ..
Bw. n. p. Case 1 = = 387
184500 -
- 4 X
22890 -
— 20
X
1548
160
184500 -
- 4 X
44500 -
- 20
X
1548
Bw. II. P. Case 2 = = —153
160
This shows that there is an excess of waste heat in Case 2,
making a total boiler horse-power, Case 1, = 1935 and Case
2, = 1548. Investigating Case 1 to see what error was intro-
duced by using 1548 in the economizer, we find approximately
800 horse-power of steam boilers in use, and the total horse-
power to be 1187, which is about 360 horse-power on the
unsafe side. Substitute again and check results. Case 2 Is
reasonably close. In any case 'the most economical size of
boiler plant to install in a plant requiring both steaming and
heating boilers is one where at least a part, if not all, of the
boilers are piped so as to be easily changed from one system
to the other. By such an arrangement the capacity may be
made the smallest possible. After obtaining the theoretical
size of the plant, it would be well to allow a small margin
in excess so that one or two boilers may be thrown out of
commission for repairs and cleaning without interfering
with the working of the plant. Case 2 seems to be the better
arrangement. Assuming 1800 total boiler horse-power we
might very well put in six 300 H. P. boilers arranged in three
batteries.
171. Cost of Heatlne from a Central Station (Direct
FIrlngr): — It will be of interest in d his connection to estimate
approximately the cost in supplying heat by direct firing to
one square foot of hot water radiation per year from the
average central station. In doing this make the boiler as-
sumptions to be the same as Art. 166. Take ooal at 13000
B. t. u. per pound, 2000 pounds per ton, and a boiler effi-
ciency of 60 per cent. Water enters the boiler at 155 degrees
from the returns, and is delivered to the mains at 180 de-
grees'. From the value of the ooal as stated, we have
15600000 B. t. u. per ton given off to the water. This is
DISTRICT HEATING
259
POWER PLANT LAYOUT.
Fig. 118,
260 HEATING AND VENTILATION
equivalent to heating 624000 pounds, or 74910 gallons, of
water. If one ton of coal costs $2.00 at the plant, we have
200 -f- 74910 = .0027 cents
This represents the amount paid to reheat one gallon of
w^ater, or to supply one square fO'Ot of heating surface one
hjour at an outside temperature of zero degrees. Take the
average temperature for the seven cold months at 32 de-
grees. This is the average for the co'ldest year in the twenty
years preceding 1910, as recorded at the U. S. Exp. Station,
I^aFayette, Indiana. We then bave an average difference
between the Inside and the outside temperatures in any
residence of 70 — 32 = 38. This makes the formula for
the heat loss, Art. 28, reduce to 38 -f- 70 = .54 of its former
value. Now, if It takes one gallon of water per square foot
of radiation per hour under maximum conditions, we have
for the seven months .54 X- 7 X 30 X 24 = 2722 gallons of
water needed for each square foot of radiation per each
heating year. This is equivalent to 2722 X .0027 = 7.35 cents
per square Coot of radiation for the heating year of seven
months.
When the plant Is working under the best conditions
this figure can be reduced. It can be done with boilers
of a higher efficiency than that stated, or by using a cheaper
coal, both of which are possible in many cases.
172. Cost of Heating: from a Central Station. Summary
of Tests: — The following tests were conducted upon the
Merchants Heating and Lighting Plant, LaFayette. In-d. ; one
in 1906 and the votlher In 1908. The plant was changed slight-
ly between the two tests and 'the radIatIo<n carried upon the
lines was much increased, although in all essential features
the plant was the .same. The circulating water was heated
by exhaust steam heaters and by heating boilers.
The plant had the following important pieces of appara-
tus employed in generating or absorbing the heat supply:
BOILERS (Steaming aind Heating).
Ttvo 125 n. P. Stirling boilens. Total heating surface
2524 sq. ft.
Three 250 U. P. Stirling boilers. Total heating surface
7572 sq. ft.
Pressure on steam boilers (gage), 150 lbs.
Pressure on heating boilers (approx.), 60 lbs.
i
DISTRICT HEATING
261
ENGINES.
One 450 H. P. Hamilton Corliss comp. engine, direct con-
nected to a 300 K. W. Western Electric 72-pole alternating
current generator 120 R. P. M. This engine carried the load
of the plant when it was above 50 K. W., which was generally
from 5:30 A. M. to 11:30 P. M. When this unit was run, direct
current was obtained by passing the alternating current
through a motor generator set.
One 125 H. P. Westinghouse comp. engine, belted to one
75 K. W. 3-phase alternating and two direct current genera-
tors, and run at 312 R. P. M. This unit was generally run
between 11:30 P. M. .and 5:30 A. M.
One 250 H. P. Westinghouse comp. engine, belt connected
to a 200 K. W. generator and two smaller machines.
PUMPS.
One centrifugal, two-stage pump, Dayton Hydraulic Co.,
direct connected to a Bate>s vertical high speed engine at 300
R. P. M.
Two Smitih-Vaile horizontal recip. duplex pumps 14 in.
X 12 in. X 18 in. Each of the three pumps connected to the
return main in such a way as to be able to use any combina-
tion at any one time to circulate the water. The centrifugal
pump had been in service only one season. It had a capacity
about equal to the two reciprocating pumps and under the
heaviest service this pump .and one of the duplex pumps
were run in parallel.
One Smith-Vaile horizontal reciprocating tank pump
6 in. X 4 in. X 6 in. to lift the water of condensation from
the exhaust heater to the tank.
One Smith-Vaile horizontal reciprocating make-up pump
6 in. X 4 in. X 6 in. to replace the water that was lost from
the system.
Two National horizontal reciprocating boiler feed pumps.
One 9^/^ in. Westinghouse air pump, to keep up the sup-
ply of air through the conduits to the regulator system in
the heated buildings.
One Deane vertical deep well pump, to deliver fresh
water to the .supply tank.
One Baragwanath exhaust steam heater or condenser,
having 1000 sq. ft. of heating surface.
262
HEATING AND VENTILATION
PARTIAL SUMMARY OF RESULTS.
1906 1908
1. Square feet of radiation 118000 150000
2. Temperature of circulating water in
degrees F., flow main 158.36 164.4
3. Temperature of circulating water in
degrees F., return main 139.9 139.6
4. Temperature of circulating water in
degrees F., after leaving heater 145.6 147.
5. Temperature of outside air in de-
grees F 32.6 37.5
6. Temperature of stack gases in de-
grees F., steaming boiler 566.8
7. Temperature of stack gases in de-
grees F., heating boiler. 562. 656.
8. Draft in stacks (all botilers averaged)
in inches of water .689 .595
9. Heating value of coal in B. t. u.
per pound 12800 11565
10. B. t. u. delivered to steaming boiler
per hour by ooal 18187000 25833000
11. B. t. u. delivered to heating boilers
per hour by coal 19226000 27917000
12. B. t. u. delivered to circulating water
by heating boilers per hour 11800000 15405000
13. B. t. u. to be charged to heating boil-
ers (Item 12 — Item 15) 7650000 6934000
14. B. t. u. delivered to circulating water
by exhaust steam from the gener-
ating engines per hour 3600000 6602000
15. B. t. u. thrown away during test
from pump exhausts and available
for heating circulating water 4150000 8471000
16. B. t. u. available for heating circu-
lating water from all exhaust steam
as in normal runming (Item 14 +
Item 15) 7750000 15073000
17. Total B. t. u. given to circulating
water per hour (Item 13 + Item 16) . .15400000 22007000
18. Gallons of water pumped per hour
[Item 17 -7- (8.33 X Items 2— 3)] 100000 lOSOOO
DISTRICT HEATING
263
19. Gallons of waiter pumped per square
foot of radiation per hour (Item 18
-=- Item 1) .85 .70
20. Efficiency of heating boilers (Item
12 -^ Item 11) approx .60 .55
21. Value of the coal in cents per ton of
2000 pounds at the plant 200. 175.
22. Average electrical horse-power 68 141
'Note. — The above values are averages and were taken
for each entire test. The B. t. u. values were considered
satisfactory when approximated to the nearest thousand.
173. Regulation: — The regulation of the heat within the
residences is best controlled from the power plant. In most
heating plants a schedule is posted at the power house whica
tells the engineer the necessatry temperature of the circu-
lating wtater to keep the interior of the residences at 70
degrees with any given outside temperature. The Merchants
Heating and Lighting Company mentioned above use the
following schedule:
Atmosphere Water Atmosphere Water
.60 deg. 120 deg. 10 deg. 190 deg.
50 " 140 " " 200 "
40 " 150 " — 10 " 210 "
30 " 160 " — 20 " 220 "
20 " 180 "
In addition, read the article by Mr. G. E. Chapman, pub-
lished in the Heating and Ventilating Magazine, August
1912, page 23, in which he describes the methods used in
regulating the Oak Park, 111. plant.
In some heating plants the regulation is by means of air
carried fro.m the compressor at the power hoXise through a
main running parallel with the water mains in the conduits
and branching to each building where it is used under a
pressure of 15 pounds to operate thermostats, which in turn
control the water inlets to 'the radiators. A closer regula-
tion 'is obtained in the latter system than in the former, but
i* iis needless to say that the 'thermiostats require careful
adjustments and frequent inspections.
Diaphragms or chokes having dlifferent sized orifices may
be placed on the return main from each building to X'egulate
the supply. Those buildings nearest to the power plant
have the advantage of a greater differential pressure than
264 KEATING AND VENTILATION
those farther away, hence should have smaller diaphragms.
By increasing the resistance in the return line from any
building the water circulates more slowly and has time to
give off more heat to the rooms. With a high temperature
of the water and a careful adjustment of the diaphragms
it is possible to have the amount of water circulated per
square foot of radiation reduced much below one gallon per
square foot per hour.
STEAM SYSTEMS.
174. Heating by steam from a central station, compared
"With hot water heating, is a very simple process. The power
plant equipment is composed of a few inexpensive parts, the
operation of which is very simple and easily explained.
These parts have but few points that require rational de-
sign. Because of the simplicity and the similarity to the
preceding discussion on Hot water systems, the work on
steam systems will be very brief. All questions referring
to the construction of the conduit, the supporting of the
pipes, the provision fo-r contraction and expansion, the drain-
6ng of the pipes and conduits, are common to both hot
w^ater and steam systems and are discussed in Arts. 138 and
139. A large part of the work referring directly to district
hot water heating applies with almost equal force to steam
heating. This part of the work, therefore, will deal with
such parts of the power plant equipment as differ from
those of the hot water system.
Steam heating may be classified under two general
heads, high pressure and low pressure. A very small part
of the heating in this country is now done by what may be
strictly called higih pressure service, i. e., where radiators or
ooils are under pressures from 30 to 60 pounds gage, and
this small amount is gradually decreasing. Ordinarily,
steam is generated at high pressure at the boiler, 60 pounds
to 150 pounds gage, and reduced for line service to pressures
varying from to 30 pounds s&.ge, with a still further re-
duction at the building to pressures varying from to 10
pounds gage, for use in radiators and ooils. Where exhaust
steam is used in the main, the pressure is ntot permitted to
go higher than 10 pounds gage, because of the back pres-
sure on the engine piston. Where exhaust steam i-s not
used, the pressures may go as high as 30 pounds gage, thus
allowing for a greater pressure drop in the line and a corre-
DISTRICT HEATING
265
spending reduction in pipe sizes. Yacuum returns may be ap-
plied to central station work the same as to isolated plants.
The principles involved in the power plant end of a
steam heating system may be represented by Fig. 119. It
will be seen that the exhaust steam from the engines or tur-
bines has four possible outlets. Pasising through the oil
separator, which removes a large part of the entrained oil,
part of the exhaust steam is turned into the heater for use in
heating the boiler feed water. The rest of the steam passes
on into the heating system. If there be more exhaust steam
than Is necessary to supply the heating system, the balance
may go to the atmosphere through the back pressure valve.
W.hen the heating system is not in use, as would be the case
in the four warm mionths of the year, the exhaust isteam may
be passed into the condenser.
I BYPASS AROUND METATCR
BACKPRESSURE VALVE
TO HEATER AND
BACK DRES5 VALVE V
EPaRATOR
TOHEATINO
SY3TEM
"TOCONDENSCR
■TO SEWER
STEAM TRAP
LIVE 3TEAM
FROM BOILERS
Fig. 119.
It is very evident, from what has been said before, that
it Wiould not be economical to condense the steam in a
condenser as long as there is a posisibiMty of using it in the
heating system. The increased gain in efficiency, when con-
densing the exhaust steam under va-cuum, is very i&mall com-
pared to the gain when this same steam is used fo'r heating
purposes. It wiould be also very poor economy to use any
live steam for heating when there were any exhaust steam
wasted. When the anaount of exhaust is-team is inisufficient,
live &team is admiitted through a pressure reducing \Talve.
175. Drop in Pressure and the Diameter of the Mains:—
The flow of s'team in a pipe follows the sfoane general law as
i
266 HEATING AND VENTILATION
the flow of water. Tlie loss of head may be represented
by the well known formula
hf = (101)
gd
w'here hf = loss of head In feet, <p = coefflaient of friction,
f = veloci'ty in feet per second, I = length of pipe in feet.
d = diameteo" of the pipe in feet and g = 32.2. Substitute,
Jif = 144 p -i- D, w'here p = drop in pressure in pounds and
D = density of the steam, and find
p = (102)
lAigd
The coefficient of friction is found to v^ary wfith the velocity
of the steam and with the diameter of the pipe. Prof. Unwin
found that for velocities of 100 feet per second (good prac-
tice for transmiission lines), it could be expressed as follows,
where c is a constant to be found by experiment,
<t> = c ( 1 + )
\ 10 d /
which, when substituted in formula 102, gives
Iv^Dc / 3
-(^+ — )
d \ 10 d /
(103)
12 g
Let W = pounds of steam passing per minute and di = diam-
eter of pipe in inches, then
1 / 3.6 \ W-lc
P = ( 1+ ) (104)
20.663 \ di / di^D
From this formula we may obtain any one of the three terms,
W, di or p, if the other two are known. Table 36, Appendix,
was compiled from formula 104 with c = .0027. For discus-
sion, see Trans. A. S. M. E., Vol. XX, page 342, by Prof. R. C.
Carpenter. Also Encyclopedia Britannica, Vol. XII, page 491.
See also, Kent, page 670, and Carpenter's H. & V. B., page 51.
It will be seen that Table 36 is compiled upon the basis
of one pound pressure drop, at an average pressure of 100
pounds absolute in the pipe. Since In any case the drop
in pressure is proportional to the square of the pounds of
eteam delivered per minute (other terms remaining con-
stant), the amount delivered at any other pressure drop
than that given (one pound) would be found by multiplying
I
DISTRICT HEATING 26'/
the amount g-iven in the table by the isquare root of the
desired pressure drop in pounds. Als-o, since the weight of
steam moved at the same velocity, under any other absolute
pressure, is approximiately proportional to the absolute pres-
sures (other terms remaining' constant), we have the
amount of steam moved under the given pressure, found by
multiplying the amount given "in the table by the square
root of ithe ratio of the absolute pressures. To illustrate the
use of the table — suppose the pressure drop in a 1000 foot
run of 6 linch pipe is 8 ounces, when the average pressure
within the pipe is 10 pounds gage. The am'Ount of steam
carried per minute is 93.7 X V.S -f- V^OO -^ 25 = 33 pounds.
Or, if the drop is 4 pounds, at an average inside pressure of
50 pounds gage, the amount carried would be 150 pounds
per minute. Conversely — find the diameter of a pipe, 1000
feet long, to carry 150 pounds of steam per minute, at an
average pressure of 50 pounds gage and a pressure drop of
8 ounces.
150 ilOO
W (table) = X - = 264 pounds
V:5 \ 66
which, according to the table, gives a 9 inch pipe.
176. Drippingr the Condensation from the Mains: — The
condensation of the steam, which takes place In the con-
duit mains, should be dripped to the sewer or the return
at certain 'specified points, through some form of steam
trap. These traps sihould be kept in first clas.s condition.
They should be Inspected every seven or ten days. No pipe
should be drilled and tapped for this water drip. The only
satisfactory way is to cut the pipe and insert a tee with
the branch Looking downward and leading to the trap. The
sizes of 'the traps and the distances between them can only
be determined when the pounds of condensation per running
foot of pipe can be estimated.
177. Adaptation to Private Plants: — Distnict steam
beating systems miay be adapted to private hot water plants
by the use 'Of a "transformer." This in principle i'S a hot
water tube heater which takes 'the place 'Of the hot water
heater of the system. It may also be adapted to warm air
systems by putting the steam through indirect coils and
taking the air supply from over 'the coils.
.
268 HEATING AND VENTILATION
178. General Application of the Typical Deslgrm — The
following brief applications are meant to be suggestive of
the method only, and the discussions of the various points
are omitted.
Square feet of radiation in the district. —
Rs = 184500 X 170 -> 255 = 123000 square feet.
Amount of heat needed in the district to supply the radiation for
one hour in zero weather. —
Total heat per hour = 123000 X 255 = 31365000 B. t. u.
Amount of heat necessary at the power plant to supply the radia-
tion for one hour in zero weather. — Assuming 15 per cent, heat
loss in the conduit (this is silightly less than that allowed for
the hot water two-pipe system, 20 per cent.), we have
31365000 -T- .85 = 36900000 B. t. u. per hour.
Total exhaust steam available for heating purposes. —
Ws (max.) = (23100 + 8680) X 1.15 = 36547 pounds per hour.
W$ (m-in.) = ( 1490 + 8680) X 1.15 = 11696 pounds per hour.
Total B. t. u. available from exhaust steam per hour for heating.—
Let 'the average pressure in the line be 5 pounds gage and
let the water of condensation leave the indirect coils in the
residences at 140 degrees. We then have from one pound of
exhaust steam, by formula 72,
B. t. u. = .85 X 960 + 195.6 — (140 — 32) = 903.7
Assuming this to be 900 B, t. u. per pound, the total available
heat from the exhaust steam for use in the heating system
is, maximum total = 32892300 B. t. u. and the minimum total,
= 10526400 B. t. u.
Square feet of steam radiation that can he supplied by one pound
of exhaust steam at 5 pounds gage. —
R3 = 900 -7- (255 -e- .85) = 3.
Total B. t. u. to be supplied by live steam, —
B. t. u. (max. load) = 36900000 — 32892300 = 4007700 B. t. u.
B. t. u. (min. load) = 36900000 — 10526400 = 26373600 B. t. u.
Total pounds of live steam necessary to supplement the exhaust
steam. — Let the steam be generated in the boiler at 125
pounds gage. With feed water a»t 60 degrees
Max. load = 4007700 -f- 1163.8 = 3444 pounds.
Min. load = 26373600 -=- 1163.8 = 22661 pounds.
DISTRICT HEATING
269
Boiler horse-power needed for tlie steam power units. — As in
Arts. 167 and 170,
Bt. H. P. (max.) = 36547 X 1.2 4- 34.5 — 1271.
B*. H. P. (min.) = 11696 X 1.2 -r- 34.5 = 407.
Total boiler horse-power needed in the plant. — 'Maxinium load.
B. H. P. (total) = 1271 + (3444 X 1.2 4- 34.5) = 1391.
It will be noticed that this total horse-power is 157
hoTse-power less than the corresponding Case 2 in Art. 170.
This is accounted for by the fact that no steam is used up in
work dn the circulating pumps, also that the conditions of
S'team generation and circulation are slightly different. 1500
boiler horse-power would probably be installed in this case.
Size of conduit mains. — Let it be required to find the
diameters of the main system in Fig. 115 at the important
points shown. Art. 147 gives the length of the mains in each
part. Allow .3 pound of steam far each square foot 'Of steam
radiation per hour ('this will no doubt be .sufficient to supply
the radiation and conduit losses). Try first, that part of the
line between the power plant and A, with an average steam
pressure in the lines of about 5 pounds gage and a drop In
pressure of 1^ ounces per each 100 feet of run (approxi-
mately 5 pounds per mile). 25200 pounds per hrour gives
W = 420. The length of "this part of the line is 200 feet and
the drop is 3 ounces, or .19 pound.
W (table) =
420
X
2158 pounds
V.19
which gives a 15 inch pipe.
Following out the same reasoning for all parts of the
line, we have
TABLE XXVIII.
|P P to A I A to B I B to C I C to D | D to E
Distance between points
Radiation supplied, sq. ft
Pressure-drop in pounds ^p
Diameter of pipe in inches, by table..
200
500
1500
1500
84000
57000
34000
19000
.19
.47
1.4
1.4
15
13
11
9
500
8000
.47
S
In general practice, these values would probably be
taken 16, 14, 12, 10 and 6 inches respectively. Ijook up
Table 36, Appendix, and check the above figures.
270 HEATING AND VENTILATION
REFERENCES.
References on nistrlot Heating:.
Technical Books.
Allen, Notes on Heating and Yentilation, p. 131.
Gifford, Ventral Station Heating.
Technical Periodicals.
Engineering News. Comparison of Costs of Forced-Circula-
tion Hot Water and Vacuum -St earn Central Heating Plants,
J. T. Maguire, Dec. 23, 1909. p. 692. Design of Central Hot-
Water System with Forced-Circulation, J. T. Maguire, Sept.
2, 1909, p. 247. Engineering Revieic. Determining Depreciation
of Underground Heating Pipes, W. A. Knight, Jan. 1910,
p. 85. Some Remarks on District Steam Heating, W. J. Kline,
April 1910, p. 61. Toledo Yaryan System, A. C. Rogers, May
1910, p. 58. Some of the Factors that Affect the Cost of
Generating and Distributing Steam for Heating, C. R. Bishop,
Aug. 1910, p. 56. Central Station Heating Plant at Craw-
fordsville, Ind., B. T. Gifford, Dec. 1909, p. 42. Wilkesbarre
Heat, Light and Motor Co., A Live Steam Heating Plant,
J. A. WUiite, July 1908. p. 32. The Heating and Ventilating
Magazine. Schott Systems of Central Station Heating, J. C.
Hornung, Nov. 1908, p. 19. Data on Central Heating Sta-
tions, Nov. 1909, p. 7. Cost of Heat from Central Plants,
March 1909, p. 31. Steam Heating in Connection w^ith Cen-
tral Stations, Paul Mueller, Oct. 1909, p. 24; Nov. 1909, p. 1.
A Modern Central Hot WTater Heating Station, W. A. Wolls,
July 1910, p. 15. Central Station Heating. F. H. Stevens, June
1910, p. 5. The Profitable Operation of a Central Heat-
ing Station without the Assistance of Electrical or Other
Industries, Byron T. Gifford, Aug. 1910. Central Station
Heating, Byron T. Gifford, Apr. 1911. Central Power and
Heating Plant for a Group of School Buildings, May 1910.
Domestic Engineering. Report of Second Annual Conven-
tion of the National District Heating Association at
Toledo. O., June 1, 1910. Vol. 51, No. 11, June 11. 1910, p. 255.
The Metal Worker. Central District Steam Heating from
Hill Top. Jan. 15, 1910, p. 78. Central Heating at Crawfords-
ville, Ind., July 30, 1910, p. 135. Data of 77 Central Station
Heating Plants, Sept. 4, 1909, p. 48. Hot Water Heating.
Teupitz, Germany, Sept. 25, 1909, p. 45. High Pressure
Steam Distribution, Munich, Germany, Oct. 2, 1909. p. 48.
Central Plant Solely for Residence Oct. 16, 1909, p. 50.
Two Types of Central Heating Plant Compared, Apr. 9, 1910.
Central Heating at Crawfordsville, Indiana, July 30, 1910.
The Engineering Record. District Heatdng, July 15, 1905. Econ-
omies Obtainable by Various Uses of Steam in a Combined
Power and Heating Plant, Feb. 18, 1905. A Study for a
Central Power and Heating Plant at Washington, Feb. 11,
1905. Utilization of Vapor of Steam Heating Returns, Oct.
22, 1904. A Central Heating. Lighting and Ice-Making Sta-
tion, Gulfport, Miss., Feb. 27, 1904. Purdue Unlversltv Cen-
tral Heating and Power Station, Jan. 30. 1904. A Central
Hot-Water Heating Plant in the Boston Navy Yard, July
16, 1904. Power. Combined Central Heating and Electric
Plants, Edwin D. Dreyfus, Aug. 20. 1912.
I
CHAPTER XIV.
TEMPERATURE CONTROL. IN HEATING SYSTEMS.
179. From tests that have been conducted on heating
systems, it has been shown that there is less loss of heat
from buildings supplied by automatic temperature contTol,
than from buildings where there is no such control. A uni-
form temperature within the building is desirable from all
points of view. Where heating systems are operated, even
under the best conditions, without such control, the effi-
ciency of the system would be increased by its application.
No definite statement can be made for the amount lOf heat
saved, but it is safe to say that it is between 5 and 20 per
cent. A building uniformly heated during the entire time,
requires less heat than if a certain part or all of the build-
ing were occasionally allowed to cool off. When a building
falls below normal temperature it requires an extra amount
of heat to bring it up to normal, and when the inside tem-
perature rises above the normal, it is usually lowered by
opening windows and doors to enable the heat to leave rap-
idly. High inside temperatures also cause a correspondingly
'increased radiation loss. Fluctuations of temperature, there-
fore, are not only undesirable for the occupants, but they
are very expensive as well.
180. Principles of the System: — Temperature control may
be divided into two general classifications, — small plants
and large plants. The control for small plants, i. e., such plants
as contain very few heating unitSj is accomplished by regu-
lating the drafts by special dampeo-s at the combustion
chamber. This method controls merely the process of com-
bustion and has no especial connection with individual reg-
isters or radiators, it being assumed that a rise or fall of
temperature in one room is followed by a corresponding
effect in all the other rooms. This method assumes that all
the heating units are very accurately proportioned to the
respective rooms. The dampers are operated thr>ough a sys-
tem of levers, which system in turn is controlled by a ther-
mostat. Fig. 120 shows a typical application of such regu-
272
HEATING AND VENTILATION
Figr. 120.
latlon. This may be ap-
plied to any system of
heat. In addition to the
thenmostaitic control
from the room to the
damper, as has just been
mentioned, closed hot
water, steam and vapor
systems should have
^ ^ regulation from the
^ — CM pressure within the
boiler to the draft. Oc-
casionally in the mjorn-
i n g- the pressure In
either system may be-
come excessive before
the house is heated
enough for the thermo-
stat to act. With such
additional -regulation no hot water heater or steam boiler
would be forced to a dangerous pressure. Fig. 121 shows a
thermostat manufactured by the Andrews Heating Co., Min-
neapolis. The complete regulator has in addi-
tion to this, two cells of open circuit baittery
and a motor box, all of which illustrate very
well the thermostatic damper control.
The thermostat operates by a differential
expansion of the Iwo different metals com-
posing the spring at the top. Any change In
temperature causes one of the metals to ex-
pand or contract more rapidly than the other
and gives a vibrating movement to the project-
ing arm. This is connected with the batteries
and with the motor in such a way that when
the pointer closes the contact with either one
of the contact rosts, a pair of magnets in the
^\=^ ^ motor causes a crank crm to rotate through
V ^^ 180 degrees. A flexible connection between this
Fig 121 crank and the damper causes the d-amper to
open or close. A change in temperature In
the opposite direction makes contact with the other post
end reverses the movement of the crank and damper. The
fnovemejit of the arm between the contacts is very isniall thua
TEMPERATURE CONTROL
273
making" the thermostat very sensitive. No work is required
of the battery except that necessary to release the motor.
Occasionally it is desira-
able to connect email heat-
ing plants having- only one
thermostat in control, to a
central station system. Fig.
122 showis how the supply
of heat may be controlled
by the above method.
Fig. 123 shows the Syl-
phon Damper Regulator
made by The American
Radiator Co., and applies
to steam pressure control.
The longitudinal expansion
of a corrugated brass or
copper cylinder operates
the damper through a sys-
tem of levers. The longitu-
dinal movement of the cyl-
inder is small and hence
the bending of the metal
in the walls of the cylinder
is very slight. This small
movement is multiplied
Fig. 122.
Fiff. 123.
274
HEATING AND VENTILATION
Ihrough the system of levers to the full amount necessary
to operate the damper. A similar device is made by the
same company for application to hot water heaters.
Temperature control in large plants, L e., thofie plants having
a large number of heating units, is much more complicated.
In furnace systems this is very much the same as described
under small plants, 'with additional dampers placed in the
air lines. The following discussions, therefore, will apply
to hot water and steam systems, and will be additional to the
control at the heater and boiler as discussed under small
plants. Fig. 124 shows a typical layout of euch a ej-stem.
Compressed air at 15 pounds per square inch gage is main-
tained in cylinder, S», which is loca<ted in some convenient
Fig. 125.
Fig. 124. ' ^3^
place for the attendant. This air is car-
ried to the thermostat, Tk, on one of the
protected walls in the room. Here it
I>asses through a controlling valve and
is then led to the regulating valve on the
(radiator. Thts air acts on the top of a
rubber diaphragm as shown in Fig. 125
to close the valve and to cut off the sup-
ply. When the room cools off, the con-
trolling valve at Tk cuts off the supply
and opens the air line to the radiator.
This removes the air pressure above the
TEMPERATURE CONTROL 275
diaphragm and permits the stem of the valve to lift. On the
opening of the valve the steam or water again enters the
radiator and the cycle is completed.
Fig. 96 shows the application of the thermostatic control
to the blower work. This shows the thermostat B and the
mixing dampers, located at the plenum chamber, in the
single duct system. The same general arrangement could
be applied to the double duct system, with the dampers in
the wall at the base of the vertical duct leading to the
room.
181. Some of the Important Points in the Installation:-—
Each radiator has its own regulating valve. All rooms
having three radiators or less are provided with one thermo-
stat. Large room'S having four or more radiators have two or
mo-re thermostats with not more than three radiators to the
thermostat. Where other motive power is not available fo.r
the 'air supply, a hydraulic compressor is used. This com-
pres-sor automatically rmaintainis the air pressure at 15
pounds gage in the steel supply tank. The main air trunk
lines 'are galvanized iTon, % and Vz inch in diameter, and
are tested under a pressure of 25 pounds gage. All branch
pipes are % and % inch galvanized iron. All fittings on
the Vs inch pipes are usually brass. Wthere flexible connec-
tions are made, this is sometimes done by armoured lead
piping. Thermiostats are usually pirovided with metallic
covers, and are finished to correspond with the hardware of
the respective rooms. Each thermostat is provided with a
thermometer and a scale for making adjustments. Each
radiator is provided with a union diaphragm valve having
a specially prepared rubber diaphragm with felt protection.
This valve replaces the ordinary radiator valve. One of
these valves iis used on the end of each hot water radiator,
one on each one-pipe steam radiator and two on each two-
pipe low pressure steam radiator. This last condi'tion does
not hold for two-pipe steam radiators with mechanical
vacuum returns, 'in which case patented specialties are
applied by the vacuum company. In such cases the s-upply
to the radiator only is controlled. In any first class system
of control, the temperature of the room may easily be kept
within a maximum fluctuation of three degrees.
182. Some Special Designs of Apparatus: — All teniipera-
ture control work is solicited by specialty companies, each
having a patented system. In the essential features these
.
•76
HEATING AND VENTILATION
systems all agree with the foregoing general statements.
The chief difference is in the principle upon which the ther-
mostat, Th, operates.
INTERMEDIATE
POSITIVE
T
Fig. 126.
Fig. 126 shows section-s through the intermediate and
positive thermostats manufsuotured by the Jiohnson Service
Company, Milwaukee. The interior workings of the ther-
mostats are as folLowis: Intermediate. — Air enters at A from
the supply tank, passes into chamber B and escapes at port
C. If thermostatic strip T expands inward to close C, the
air pressure collects in B and presses down port valve F,
thus opening port E, letting a.ir through into F and out at G
to close the damper. When T expand® outward, pressure at
B is relieved and F is forced back by <a spring, closing E.
Air in F reacts against the diaphragm and escapes through
hollow valve V at H, permitting the damper to open. Posi-
tive. — ^Air enters at A, passe<s into ch-amber B and escapes
at C. If thermostatic strip T expands inward to close G, air
pressure collects in B, forces out the knuckle joint K and
TEMPERATURE CONTROL 277
operates the three-way valve T, thus shutting port E and
opening port F, letting air escape and radiator valve open:
When T expands outward, pressure at B is relieved, knuckle
joint K returns, pulling V outward, thus shutting port F,
opening E, letting air escape through O and shutting off
radiator valve.
The real thermostat is the spring T. This is composed
of steel and brass strips brazed together. Because of a
higher coefficient of expansion in the brass than in the
s-teel, a change in the room temperature causes the spring
to move toward or away from the seat C. T is adjustable
for any desired room temperature. The intermediate ther-
mostat is used on indirect heating where mixing dampers
are employed and where an intermediate position of the
valve is necessary. The positive therm'Osta,t is used on
direct radiators and coils where a full open or full closed
movement of the valve is desired.
Fig. 127 shows a section through the pattern K thermo-
stat, manufactured by the Powers Regulator Co., Chicago.
This thermostat consists of a frame carrying two. corrugated
disks, brazed together at the circumference and containing a
volatile liquid having a boiling point at about 50- degrees F.
At a temperature of about 70 degrees, the vapor within
the disks has a pressure of about 6 pounds to the square
inch. This pressure varies with every change of tempera-
ture and produces variations in the total thickness at the
center of the disks.
The compressed air enters at H and passes into chamber
"N through the controlling valve J, which is normally held to
its seat by a coil spring under cap P. Within the flange M
is located an escape valve L upon w.hich the point of the
supply valve J rests. Valve L tends to remain open when
permitted by reason of the spring underneath the cap. WThen
the temperature rises sufficiently to cause the disks to in-
crease in thickness and miove the flange M, the firrst action
is to seat the escape valve L, its spring being weaker than
that above J. If the expansive motion is continued after
valve L is seated, the valve J is then lifted from its seat
and compressed air flows into the chamber N. As the
air accumulates in chamber N, it exerts a pressure upon the
elastic diaphragm K in opposition to the expansive force of
the disk. So, whenever there is sufficient pressure in N to
balance the power exerted by the disks, the valve J returns
278
HEATING AND VENTILATION
Fig. 127.
to its seat and no more air is permitted to pass through.
If the temperature falls, the pressure within the disks be-
comes less, the disks draw together and the over-balancing
air pressure in N reverses the movement of the flange M and
permifcs the escape valve L under the influence of its spring
to rise from its seat, whereupon a portion of the air in N
is discharged until the pressure in N becomes equal to the
dinainished pressure from the disks. Thus the pressure of
the air in N is maintained always in direct proportion to the
expansive power (temperature) of the disks. Port / con-
nects with chamber N and leads to the diaphragm valve.
This thermostatic valve controls the regulator valve by
a graduated moveiment and is used on the dampers for
blower work. Another farm with maximum movement only
is designed for steam systems.
Fig. 128 shows the positive and graduated thermostats
as manufactured by the National Regulator Company, Chi-
cago. The thermostatic element In these thermostats Is the
vulcanized rubber tube .4, which changes its length with the
varying room temperatures and causes the valve O to open
or close the port O, thus controlling the supply of air to
TEMPERATURE CONTROL.
279
POSITIVE
INTERMEDIATE
Fig. 128.
and from the radiator valve or the regulating damper. In
the positive thermostat air enters the tube from the supply
through the filter and restricted passage P. From the in-
teriotr of the tube the air leaves through the middle orifice
and enters the pipe leading to the radiator valve. If the
room 'temperature is above the nominal, port G closes and the
air pressure collects in the tube, thus creating a pressure
in the line leading to the radiator valve and closing it. If
the room temperature falls below the normal, port G opens,
air is exhausted from the tube to "the atmosphere, the pres-
sure on the radiator valve is released and the valve opens.
The intermediate thermostat differs from the positive ther-
mostat in having but one air line. Room temperatures
below the normal contract tube A, open port G, and exhaust
the air to the atmosphere. With this release in pressure in
the pipe at P the regulating damper is turned to admit
more warm air into the room. W.ith the room temperature
above the normal, tube A expands, port G closes, pressure in
pipe P increases and the regulating damper is turned so as
to admit a lower temperature of air in the room. By means
of this a graduated movement of the damper is obtained.
REFERENCES.
References on Temperature Control.
Metal Worker. Temperature Control in House Heating,
Jan. 7, 1911.
CHAPTER XV.
ELECTRICAL HEATING.
In the present state of the heating business it seems
ajlmost unnecessary to discuss electrical heating-, in any
serious way, in connection with steam power plants. The
re«asons will be seen in the following brief discussion.
Electrical heating oan appeal to the public only from the
standpoint of convenience, since a comparison of economies
between steam, hot water or warm air heating on one hand,
and electrical heating on the 'other, is wholly against the
l-atter. Its application to the processes of heating will find
its greatest economy in connection with water power plants
where the combustion of fuel is eliminate>d from the prop-
osition. This discussion will not bear in any way upon the
water power generator.
183. Equations Employed in Electrical Heating: Deslgrn :—
1 H. P. = 746 watts.
1 H. P. = 33000 ft. lbs. per min. = 1980000 ft. lbs. per hr.
1 B. t. u. = 778 ft. lbs.
1 H. P. hr. = 1980000 ^ 778 = 2545 B. t. u. per h«r.
1 H. P. hr. = 746 watt hrs. = 2545 B. t. u. per hr.
tt watt hT. = 3.412 B. t. u. per hr.
1 watt hr. = 3.412 4- 170 = .02 sq. ft. of hot water rad.
1 watt hr. = 3.412 -^ 255 = .0134 sq. ft. of steam rad.
1 kilo-watt hr. = 20.1 sq. ft. of hot water rad. (105)
1 kilo-watt hr. = 13.4 sq. ft. of steam rad. (106)
1S4. Comparison bet^veen Electrical Heating: and Hot
Water and Steam Heating: — The loss in transmitting elec-
tricity from the generators through the switchboard to the
radiators may be small or large, depending upon the condi-
tions of wiring, the current transmitted and the pressure on
the line. In all probability it would equal or exceed the
transmission losses In hot water or steam lines. Assuming
these lasses to be the same, a fair comparison may be made
In the cost of heating by the various methods. The operat-
ing efficiency of an electric heater is 100 per cent., since all
ELECTRICAL HEATING 281
the current that is passed into the heater is dissipated in
the form of heat and no other losses are experienced. This
is not true of steam systems where the water of condensa-
tion is thrown away at fairly high temperatures. Where
electricity or steam is generated and distributed all in the
same building, there is no line loss to be accounted for,
since all of thiT heat goes to heating the building and counts
as additional radiation.
Equations 105 and 106 show the theoretical relation
existing between electrical heating and hot water and steam
heating compared at the power plant. The following dis-
cussion is based, therefore, upon the assumption that 1
kilo-watt hour, in an electric radiator, will give off the same
amount of heat as 20.1 and 13.4 square feet of hot water and
steam radiation respectively. With coal having 13000 B. t. u.
per pound and a furnace efficiency of 60 per cent., it will
require 3412 -i- V800 = .44 pound of coal per hour. If coal
costs $2.00 per ton of 2000 pounds, there will be an actual
fuel expense of .044 cent. On the other hand, assuming the
combined mechanical efficiency of an engine or turbo-gener-
ator set to be i*0 per cent., the heat from the steam that is
turned into electrical energy per hour is 1000 -h .90 = 1111
watts, for each kilo-watt delivered. Now if this unit has
15 per cent, thermal efficiency, we have the initial heat in
the steam equivalent to 1111 -=- .15 = 7400 watt hours. From
this obtain 7400 X 3.412 = 25249 B. t. u. per hour; or, 25249
-^ 7800 = 3.2 pounds of coal per hour. This, at the same
rate as shown above, would be worth .32 cent. Comparing,
the electrical generation actually costs 7.2 times as much as
the other. This comparison has dealt with the fuel costs at
the plant and has not taken into account the depreciation,
labor costs, etc., the object being to show relative efficien-
cies only.
Another way of looking at this subject is as follows.
A fairly large turbo-generator set (say 500 K. W.) will
deliver 1 kilo-watt hour to the switchboard on 20 pounds
of steam. With 10 per cent, additional steam for auxiliary
units, this amounts to 22 pounds of steam per kilo-watt hour
at the switchboard. One pound of steam generated in a
plant of this kind with the above efficiencies and value of
coal, also with a steam pressure of 150 pounds and a good
feed water heater, will give to each pound of steam approxi-
mately 1000 B. t. u. This makes 22000 B. t. u. or 2.8 pounds
282 HEATING AND VENTILATION
of coal required to each kilo-watt output. This Is about 10
per cent, less than the above figures.
The ratio of 7 to 1, as shown in the above efficiencies,
does not seem to hold good in the selling price to the con-
sumer. In round numbers, district steam and hot water
heating systems supply 25000 B, t. u. to the consumer for
one cent. The cost for electrical energy to the consumer is
between 6 and 7 cents per kilo-watt. This gives 3412 -i- 6.5
= 525 B. t. u. for one cent. Comparing with the above, gives
a ratio of 48 to 1.
185. The Probable Future of Electrical Heatingr; — Be-
cause of the low efficiency of electrical heating as compared
to other methods of heating, it is very probable that it will
not replace the other methods except in so far as the con-
veniences of the user is the principal thing sought for, and
the expense of operating a minor consideration. In some
forms of domestic service, however, electrical heating is
sure to find considerable usefulness. The temperatures of
low pressure steam and hot water, together with the incon-
venience of use, are such as to eliminate them from many
of the household economies. They will probably continue
to be used for house heating, water heating and laundry
work. For occupations that require temperatures above 250
degrees, such as broiling, frying, ironing, etc., the electrical
supply will be in demand.
Heating by electricity on a large scale is being planned
in Stavanger, Norway. 25000 horse-power can be developed
by water power. This will be turned into electrical energy
and sold at $7.00 per horse-power year.
REFERENCES.
References on Electrlcnl Heating:.
Technical Periodicals.
The Heating and Tcntiloting Magazine. Electrical Heating
and Steam Heating, Feb. 1907, p. 28. Electric Heating,
W. S. Hadaway, Jr., Nov. 1908, p. 28; Dec. 1908, p. 26. The
Electrical World. Vol, 52, pages 450, 903. 1112 and 1358. and
Vol. 53, pages 5, 274 and 921. The Metal Worker. Electrical
Heating at Biltmore, N. C, March 7, 1908, p. 37. Electric
Heating with Fan Blast in Paris, Aug. 29. 1908. p. 55. Cool-
ing and Electric Heating on Ship Board. Sept. 15. 1906; Sept.
22. 1906; Oct. 6. 1906; Nov. 21. 1908. Unit Cost Limit of Elec-
tric Heating, Dec. 26. 1908, p. 43. Cost of Electric and Gas
Cooking, Aug. 29, 1909, p. 50. Electric Heating and Steam
Train in l^'rance. Nov. 27. 1909, p. 37. Railway Age Gazette. New
Electric Boiler. June 20. 1910, p. 1680. Cannicr'8 Magazine.
Electric Heaters, H. M. Phillips, Dec. 1909.
CHAPTER XVI.
.
REFRIGERATION.
DESCRIPTION OF SYSTEMS AND APPARATUS.
186. General Divisions of the Subject: — The rapidly in-
creasing' demand for the cold storage of food products, the
production of artificial ice and the cooling of buildings have
developed for the heating engineer a broad and inviting-
field, namely, refrigeration. A municipal electric or pump-
ing station with a district heating plant to utilize the ex-
haust steam in winter and a refrigeration plant to utilize
the same in summer furnishes a unique opportunity for
economic engineering. One application of the above princi-
ple where a 10-ton ice plant of the absorption type was so
operated in a town of 3500 population and earned a dividend
of 13 per cent, on the investment, is proof, if any is needed,
that the field is an intensely practical one.
As in heating systems there must be sources of heat,
circulating mediums, distributing systems and delivering
systems whereby the carriers give up their heat at the
proper places in the circuits, so in 'refrigerating- systems
there must be sources of minus heat or of heat abstraction,
circulating mediums, distributing systems and receiving sys-
tems whereby the carriers take up heat at the proper places
in the circuits from articles or rooms that are being cooled.
The carriers (circulating mediums), and the receiving and
transmitting of the heat to and from them present no special
difficulties or great diversity of practice, but in the methods
of producing and maintaining the sources of minus heat
there are considerable differences and numerous methods.
187. Refrigerating Systems may be divided into two
groups, those producing cold by more or less chemical action
between ingredients upon mixing, called chemical systems, and
those producing cold by the evaporation of a liquified gas
or the expansion of a compressed gas, called mechanical sys-
tems. Chemical systems are used only occasionally in com-
mercial work, but are frequently found in small sized plants
for domestic purposes. Low first cost and convenience of
handling are the principal advantages. This division in-
cludes the simple melting of ice and the mixing of ice and
2S4
HEATING AND VENTILATION
salt for temperatures as low as to — 5 degrees. The latter
is much used in domestic processes for the production of
table ices, etc. Other ingredients used in the mixtures with
the corresponding temperature drops which may be ex-
pected are given in Table 53, Appendix. The chemical
method of producing cold is occasionally used to maintain
low temperatures in storage rooms while repairs are being
made upon the regular machinery. The chemical methods
of cooling are so simple in principle that they will not be
discussed further in this work. Mechanical systems include
all the practical methods of commercial refrigeration. These
are, the vacuum system, the cold air system, the compression system
and the absorption system.
I
188. Vacuum System: — This system was formerly of
some importance but of late years has given place to other
and more efficient methods. Fig. 129 shows a vacuum sys-
tem in diagram. If a spray of water
or brine is injected into a chamber
that contains pans of sulphuric acid
and is kept at a partial vacuum of
one or two ounces, the acid absorbs
the water vapor from the spray, thus
assisting in maintaining the vacuum
and lowering the temperature of the
remainder of the spray. The vapor-
ization of the part that is absorbed
by the acid requires heat. This
heat is taken from the liquid of the
spray that is not absorbed, conse-
quently the temperature of the re-
maining liquid is lowered. In a
system of this kind a temperature
of 32 degrees may easily be ob-
tained. The water or brine after
cooling is then circulated through
the coils of the cold storage room
where it takes up the heat of tlie rooms and contents and
returns to the vacuum chamber to be ag«.in partially evapo-
rated and cooled.
189. Cold Air System: — The cold air system is used prin-
cipally on ship board. Fig. 130 shows diagrammatically the
parts and the operation of the system. The cycle has four
w
3
Fig. 129.
REFRIGERATION
285
Fig. 130.
parts, compression In one of the cylinders of the compressor,
cooling in the air cooler by giving off heat to the cold water
thus removing the heat of compression, expansion in the sec-
ond cylinder of the compressor thus cooling the air, and
refrigeration in the cold storage room where the heat lost dur-
ing expansion is regained from the articles in cold-storage.
Cold air machines work at low efficiencies because of the
necessarily large cylinders and their attendant losses due
to clearance, heating of the compression cylinder, snow in
the expansion cylinder and friction. The system has much
to recommend it, however, since it is extremely simple, occu-
pies a very small space compared with other systems and
uses no costly gases, chemicals or supplies.
190. The Compression and the Absorption Systems have
in common this fact — both use a refrigerant, i. e., a liquid hav-
ing a comparatively low boiling point. Perhaps the most
common refrigerant is anhydrous ammonia, which boils, at
atmospheric pressure, at 28.5 degrees below zero and in
doing so absorbs as latent heat 573 B. t. u. Table 54, Ap-
pendix, gives further properties. Other refrigerants used
to a lesser extent are sulphur dioxide, SO2, which boils at
— 14 degrees under atmospheric pressure with a latent heat
286 HEATING AND VENTILATION
of 162 B. t. u. and carbon dioxide, COo, which boils at — 30
deg-rees under a pressure of 182 pounds per square inch
absolute with a- latent heat of 140 B. t. u. A comparison of
the temperatures and pressures of four common refriger-
ants is given in Table 59, Appendix. Pictet's fluid is a mix-
ture of 97 per cent, sulphur dioxide and 3 per cent, carbon
dioxide.
A choice of a universal refrigerant can scarcely be made
because of the varying conditions of individual plants. The
principal difficulty with the use of sulphur dioxide is the
fact that any water uniting with it by leakage immediately
produces sulphurous acid with its corroding action upon all
the iron surfaces of the system. This same objection holds
also for Pictet's fluid. The objections to the use of carbon
dioxide are, first, its comparatively low latent heat, and
second, the high pressure to which all parts of the apparatus
and piping are subjected. -Pressures of from 300 to 900
pounds per square inch are very common. Perhaps the worst
charge that can be made against ammonia as a refrigerant
is that it is highly poisonous and corrodes metals, particu-
larly copper and copper alloys. However, the high latent
heat of ammonia, together with the fact that its pressure
range is neither so high as with oairbon dioxide, nor so low
as with sulphur dioxide, are perhaps the chief reasons for
the very general preference for ammonia as the comxnercial
refrigerant in compression systems; while its great afl^nity
for and .solubility in water, are what make the absorption
system a possibility.
101. Compression System: — Compression machines may
work well with the use of any one of the four refrigerants of
Table 59, df the proper pressures and temperatures are ob-
served and maintained. The common refrigerant for thl«
type is, however, anhydrous ammonia, for reasons given
above. Fig. 131 shows a diagrannmatic sketch of the com-
pression system. To follow the closed cycle of the ammonia,
start with a charge being compressed in the cylinder of the
compressor. From this it is conveyed by pipe to the con-
denser which, being cooled by water, abstracts the latent
heat of the refrigerant and condenses it to a liquid. From
the condenser the liquid refrigerant is convoyed to the ex-
pansion valve through which it expands into the evaporator
or brine cooler. In changing from a liquid to a gas in the
evaporator it absorbs from the brine an amount of heat
REFRIGERATION
287
REFRIGERATOR
ROOn AT 50
COOLING WATER UOUIO AHnONIA [xFANSION VftLVE LIQUID AnnONlA
Fig. 131.
WAPn BRINE
equivalent to the heat of vaporization of the ammonia.
Upon leaving the evaporator the refrigerant is again ready
for the cylinder of the compressor, thus completing the
cycle.
If the refrigerant is ammonia, the compressor is com-
monly of the vertical type, direct connected to a horizontal
Corliss engine as shown in Fig. 132. This type of com-
TEN TON AMMONIA COMPRESSOR
Fig. 132.
UNIVERSITY OF NEBRASKA
pressor combines the high efficiency of the Corliss engine
with the vertical type of compressor which is probably the
best type for reliable service of valves and pistons. The
vertical compressor is usually single acting with water
jacketed cylinders. Horizontal compressors are usually
double acting, as shown in Fig. 133, where the prime movei-
288
HEATING AND VENTILATION
Fig. 133.
Is a direct connected electric motor. Poppet valves in this
type are placed at an angle of 30 degrees to 45 degrees with
the center line of the cylinder, a construction made neces-
sary by space restrictions on the cylinder heads. Compres-
sors for other refrigerants are commonly of these same
xypes, the main difference being that compressors tor carbon
dioxide systems are nearly always two-stage to produce
high compressions. The intermediate cooler pressures range
from 300 to 600 pounds per square inch. Horizontal steam
OnO
Flgr. 134.
REFRIGERATION
289
cylinders in tandem with the compressor cylinders are com-
mon for the carbon dioxide systems and the compressor cyl-
inders are usually single acting-.
192. Condensers for Compression Systems are classi-
fied under four heads, atmospheric condensers, concentric
tube condensers, enclosed condensers and submerged conden-
sers. An elevation of an atmospheric condenser is shown in
Fig. 134. As illustrated it consists of vertical rows of pipes
so connected by return bends as to make the hot refrigerant
pass through each pipe beginning at the top, while the cold
water main at the top of the row furnishes a spray of water
which trickles over the outside of the pipes. The gas on
the inside of the pipes is thus cooled by the extraction of
the quantity of heat that is used in raising the temperature
of the water and evaporating a part of it. The complete con-
denser may consist of any required number of these vertical
rows, placed side by side, each row properly connected to
the hot gas header and to the liquid header.
An elevation of one section of a concentric tube condenser la
shown in Fig. 135, The arrows show the paths of the gas
and water. As in the atmospheric type the gas enters at the
top and the liquid is drawn off below. In its descent It
Fig. 135
<.'9U
HEATING AND VENTILATION
passes through the annular space between the two concen-
tric pipes and is cooled by the atmosphere on the outside of
the larger pipes and by the water circulating through the
inner pipes. This condenser has the advantage over the sim-
ple atmospheric condenser in that the water may be made to
have an upward course through the apparatus, thus bring-
ing the coldest water in contact with the pipes carrying the
liquid rather than with the pipes carrying the hot gas.
Since the efficiency of the plant as a whole is very largely
dependent upon the temperature of the liquid at the expan-
sion valve this matter of the "counter flow" of the cooling
water is an important one. For the medium sized and large
compression systems this form of condenser is used almost
without exception. ^
The enclosed condenser. Fig. 136, is very similar to the sur-
face coil condenser in steam engine
plants. It consists of a cylindrical
chamber with a number of concen-
tric pipe spirals connecting a hot
water header at the top with a cold
water header at the bottom of the
cylinder. The pipes of the spirals
are provided with stuffing boxes
where they pierce the upper and
lower heads of the cylinder. With
this condenser a counter flow of
the water is used, the cold water en-
tering the bottom of the coils and
flowing upward, so that the liquid re-
frigerant at the bottom of the cylin-
der is very near the temperature of
the incoming water. ^
A submerged condenser, as the name
implies, contemplates a rather large
body of water below the surface of
which there is submerged a coil for
circulating the hot refrigerant. Fig.
137 shows a section of such a con-
denser. The hot gas enters at the
top fitting of the coil and loaves at
lower flitting. Cold water is constantly flowing in at the bot-
tom of the tank and leaving by ithe overflow at the top, being
heated as it rises. The form of the coil is usually spiraL
Fig. 136.
REFRIGERATION
291
although this condenser may be built with coils of the re-
turn bend type when larger surface is required. Only the
smaller compression plants use the enclosed or the sub-
merged type of condenser.
VWLR
Fig. 137.
In general, condensers may be considered vital factors
in the economy of compression plants. They must be reliable
in service and economical in operation, and must be so de-
signed and proportioned that they will deliver liquid re-
frigerant within five degrees of the temperature of the in-
coming cooling water. A condenser should present all
joints, particularly those holding the refrigerant, to plain
view for easy inspection and repair. Since it is the func-
tion of the condenser to dissipate the heat of the refrigerant
gas, it is not uncommon to install it upon the roof or out-
side the building in some cool place. This is especially true
where the atmospheric or the concentric tube' types are
used. In such positions the heat radiated by the condenser
is not given back to the rooms and piping systems. In addi-
tion, the cooling action of the atmosphere assists in making
the system more efficient.
292
HEATING AND VENTILATION
103. Evaporators for compression systems may be con-
sidered as condensers, reversed in action but very similar
in form. If the refrigerating effect is accomplished by the
brine cooling system an evaporator of some type will be
necessary, but if the refrigeration is accomplished by circu-
lating the expanding refrigerant itself, no evaporator is re-
quired. Evaporators, or brine coolers, may be classified
according to tlie method of construction, as shell coolers and
concentric tube coolers.
The shell cooler takes various forms. One is shown by
Fig. 136, being in effect an enclosed condenser with brine
instead of cold water circulating in the coils. The heat of
the brine is transferred to the cool liquid refirigerant, caus-
ing the refrigerant to evaporate and take from the brine
an amount of heat equal to the latent heat of the refriger-
ant. The proper height to which the liquid refrigerant
should be allowed to rise in the evaporator is a very much
disputed point, some old and experienced operators claim-
ing greatest efficiency when about one-third of the cooling
surface is covered with liquid refrigerant leaving two-
thirds to be covered with gaseous refrigerant. Others claim
that the entire surface should be covered or "flooded" with
liquid refrigerant. These points of view give rise to
the two terms dry systems and flooded systems. Of late years
the flooded systems are gaining somewhat in favor, a sepa-
rator being installed between the evaporator and the com-
pressor to prevent any liquid being drawn into the com-
pressor cylinder. This separator drains any liquid which
Fig. 138.
REFRIGERATION 293
may collect therein, back into the evaporator. In the flooded
system the brine cooler more commonly takes the form
shown in Fig-. 138, where at the end A D of the brine tank
ABCD is shown the flooded cooler E. This cooler consists
of a boiler shell filled with tubes, the brine circulating
through the inside of the tubes while the interior of the
large shell is nearly or quite filled with liquid refrigerant.
Concentric tube brine coolers are made of piping very similar
in principle to that shown in Fig. 135, with the exception
that instead of two concentric pipes, three are more com-
monly employed. The brine circulates through the inner-
most of the three and through the outermost, while the
annular space between the smallest pipe and the middle
pipe is traversed by the liquid refrigerant. In this way
the annular space filled with refrigerant has brine on both
sides and the cooling of the brine is very rapid. The numer-
ous joints in this cooler present a constant source of trouble.
Salt brine will usually freeze in the inner pipe, so that cal-
cium chloride brine must be used.
A choice of evaporators or coolers depends mainly upon
whether the plant is to run continuously or intermittently.
When run continuously only a small amount of brine is
required and this, when cooled quickly and circulated
quickly, would call for a concentric tube cooler. When run
intermittently a much larger body of brine is desirable so
as to remain cool longer during the night hours when the
plant is not operating. For this condition a shell type
cooler would probably be preferred.
In addition to the condensers and evaporators that were
described in detail, there are to be found on the well equip-
ped compression system the following pieces of apparatus
which will be mentioned and described only briefly. An oil
separator is commonly found in the line connecting the con-
denser with the compressor. This is simply a large cast
iron cylinder with baffle plates to separate the oil from the
ammonia. Since the oil is heavier than the ammonia it set-
tles to the bottom and may be drawn off. An ammonia scale
strainer is often found just before the compressor intake.
Small purge valves are located at all high points in the
system for the purpose of exhausting the foul gases or the
air which may collect in the system. Such a purge con-
nection is shown on the right end of the upper coil In
Fig. 134.
294
HEATING AND VENTILATION
104. Pipes, Valves and Flttinsa for compressor refrig-er-
ant piping are considerably different from the standard types.
If the refrigerant is ammonia, no brass enters into the de-
sign of any part of the piping or auxiliaries traversed by the
ammonia. The operating principles of all valves are the
same as standard ones but they are made heavier and en-
tirely of iron, or iron and aluminum. The common threaded
joint used on all standard fittings is replaced in ammonia
systems by the bolted and packed joint. It is not within the
scope of this work to go into these details further than to
Fig. 139. Fig. 140.
give a section of an ammonia expansion valve, Fig. 139, and
a section of a typical ammonia joint, Fig. 140.
195. Ab.sorptioii System: — As stated in Art. 190, the
great affinity of ammonia gas for water and its solubility
therein, are what make the absorption system a possibility
and give it the name as well. At atmospheric pressure and
50 degrees temperature one volume of water will absorb
about 900 volumes of ammonia gas. At atmospheric pres-
sure and 100 degrees temperature one volume of water
will absorb only about one-half as much gas, or 450 vol-
umes. If then, one volume of water is saturated at 50 de-
grees with ammonia gas and heated to 100 degrees there
will be liberated about 450 volumes of ammonia gas. Hence
It is evident that a strea/m of water may be used as a con*
veyor of ammonia gas from one place or condition to an-
other, &ay from a condition of low temperature and pres-
sure where the absorbing stream of water would be cool, tv
REFRIGERATION
295
a condition of high temperature and pressure, where the
g-as would be liberated by simply heating the water. It will
be noticed that the gas has been transferred as a liquid
without a compressor or any compressive action, by pump-
ing a stream of water of approximately one-four hundred
and fiftieth of the volume of the gas transferred. This, in
the abstract, is the method employed in the absorption
system to convey the ammonia gas from the relatively low
temperature and pressure of the evaporator to the high
temperature and pressure at the entrance of the condenser.
The absorption system, when closely compared in prin-
ciples of operation to the compression system, differs only
in one respect, namely, the absorption system replaces the
gas compressor by the strong and weak liquo>r cycle. As
^s>^o«;:«;'^*«j,
'■'QUOR cyclC
Fis:. 141.
shown in Fig. 141, both sys-
tems have arrangements of
condenser, expansion valve
and evaporator that are iden-
tical, hence the part of the
cycle through these need not
be considered. The problem
of completing the cycle from
evaporator t o condenser,
however, is solved quite dif-
ferently in the two systems.
In the compression system
(upper diagram) the evapo-
rator delivers the expanded
gas to the compres-
sor, from which,
under high pres-
sure and tempera,
ture, it is delivered
to the condenser
and the cycle is
completed. In the
absorption system
(lower diagram)
the evaporator de-
livers the expanded
gas to an absorber,
in which the gas
comes in contact
with a spray of so-
called weak liquor,
296 HEATING AND VENTILATION
consisting- of water containing about 15 to 20 per
cent, of aniiydrous ammonia. Tlie weak liquor absorbs
the ammonia gas through which the liquor is sprayed and col-
lects in the upper part of the absorber as strong liquor, contain-
ing about twice as much anhydrous ammonia as the weak
liquor, or 30 to 35 per cent. From here it is pumped through the
exchanger (which will be ignored for the present) into the
generator at a pressure of about 170 pounds per square inch
gage. In the generator boat is supplied by steam coils im-
mersed in the strong liquor. As this liquor is heated it
gives up about half of the contained ammonia gas which
rises and passes from the generator to the condenser, thus
completing the ammonia or primary cycle, while the weak
liquor flows from the bottom of the generator through the
exchanger and pressure reducing valve back to the ab-
sorber, thus completing the secondary or liquor cycle.
In general then, the absorption system uses two cycles,
that of the ammonia and that of the liquor, the paths of the
two cycles being coincident from the absorber to the gen-
erator. The liquor pump serves to keep both cycles in mo-
tion. The pump creates the pressure for both cycles and
the expansion valve and the reducing valve reduce the
pressure respectively for the ammonia cycle and the liquor
cycle. The exchanger does not mix or alter the condition of
the two streams of liquor passing through it, for its only
function is to bring these two streams close enough that
the heat of the iccuk liquor from the generator may be trans-
ferred to the strong liquor going to the generator. Stated in
other words, the exchanger heats the strong liquor by cool-
ing the weak liquor, thus effecting a saving of heat which
would otherwise be lost, since the weak liquor must be
cooled before it is ready to properly absorb the gas in the
absorber.
196. An Elevation of nn Absorption System with the
elements piped according to what is considered best prac-
tice is shown in Fig. 142. Starting at the expansion valve,
the ammonia (liquid, gas or gas in solution) passes in order
through these pieces of apparatus: the evaporator, the ab-
sorber, the liquor pump, the chamber of the exchanger or the
coil of the rectifier, the generator, the chamber of the recti-
fier and the condenser back to the expansion valve. At the
same time the liquor used to absorb the gas travels In ordrr
through these pieces: the absorber, the liquor pump, tlie
REFRIGERATION
297
COLD enwE TO refrkwor
fVO*
aXUQ WATER
TO ABSORGER
Fig. 142.
chamber of the exchanger or the coil of the rectifier, the
generator, the pressure reducing valve and the coil of the
exchanger back to the absorber. The method of pipe connec-
tions shown is a very common one although some varia-
tion may be found, especially in the continued use of cool-
ing water in consecutive pieces of apparatus. As shown,
the cooling water is first used in the condenser. This will
be found so in all plants. From the condenser the cooling
water may next be taken to the absorber, as shown in the
sketch, or it may be used in the rectifier coil instead of the
strong liquor. In recent years the practice of by-passing
a certain amount of the cool, strong liquor from the pump
through the rectifier is gaining in favor. Fig. 142 shows
a plant having bent coil construction. Plants are also built
having straight pipe construction, where all coil surfaces
shown are replaxied by straight pipes, the condenser being
usually of the concentric tube atmospheric type and the
evaporator being also of the concentric tube brine cooler
type, as mentioned under compression systems. Both types
of absorption plants are found in use.
298
HEATING AND VENTILATION
107. Generators are classified as horizontal and verti-
cal. Fig, 143 shows a horizontal type generator, with the
Fig. 143.
analyzer and exchanger, and Fig. 144 shows the vertical
type, also with the analyzer. The horizontal type may have
one or more horiontal cylinders equipped with steam coals.
The analyzer, which may be considered as an enlarged dome
of the generator, is used to condense the water vapor which
rises from the surface of the liquid in the generator. To
do this the analyzer has a series of horizontal baffle plates
through which the incoming cool, strong liquor trickles
downward while the heated mixture of ammonia gas and
water vapor passes upward through interstices. In this
way the strong liquor gradually cools the ascending water
vapor and condenses much of it on the surfaces of the
baffle plates,
108. Rectifiers are arrangements of cooling surface
designed to thoroughly dry the gas just before It passes
into the condenser. This is accomplished by presenting
to the hot product of the generator just enough cooling sur-
face to condense the water vapor without condensing any of
REFRIGERATION
299
^
Fig. 144.
the ammonia gas. Rectifiers are
very similar in general design to
the various types of condensers,
there being atmospheric, concen-
tric tube, enclosed and submerged
rectifiers just as thare are these
same type of condensers, each de-
scribed under the head of con-
densers for compression systems.
Rectifiers may save heat by the
arrangement sihown in Fig. 142,
where the iheat abstracted from the
water vapor is given to the cool,
strong liquor before entering the
generator. As shown, the strong
liquor may be divided, part pa.ss-
ing through the rectifier and part
through the exchanger, or the
strong liquor may all go through
the exchanger first and then
through the rectifier. Where
strong liquor is so used, the recti-
fier is always of the enclosed
type. Rectifiers using water as
the cooling medium are often
called dehydrators, the term rec-
tifier being more properly used
when the cooling medium is the
strong liquor.
199. Condensers for absorption
~" systems do not differ in design
from those used for compression
systems. The same types are used,
and in 'the same manner, the sur-
face being somewhat less due to
the precooling effect of the recti-
fiers or dehydrators. As a gen-
eral statement, it is claimed that
from 20 to 25 per cent less surface
is required in the condenser for an
absorption machine than is re-
quired in one for a compression
machine.
300
HEATING AND VENTILATION
LOXR
I oooocx^S VtxxxxxdI
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..v^t^l =^00000 I
5CCH r^oocxx)'^
200. Absorbers may be classified as dry absorbers, wet
absorbers, atmospheric absorbers, concentric tube absorb-
ers and horizontal and vertical tubular absorbers. In the
dry absorber, the top section of which is shown in Fig. 145.
the weak liquor enters at the
middle of the top header and
is sprayed upon a spray pan,
from which it drips downward
over the coils. The gas enters
as shown, part being delivered
above the spray plate, so as to
come into contact with the
spray and the larger part being
taken downward through the
central pipe to a point near the
bottom of the absorber, from
Pig. 145. which point it flows upward
against the descending weak liquor by which it is absorbed.
As the gas is dissolved by the weak liquor the heat of ab-
sorption is given off, and taken up by the cooling water in
the coils. The result is a strong liquor which collects in
the absorber ready to be delivered to the pump.
The wet absorber, on the contrary, has practically the
whole body filled with weak liquor and the ammonia gas
enters near the bottom, bubbling up through the weak
liquor thus saturating it. Various baffle plates with fine
perforations break up the gas into small bubbles thus aid-
ing in presenting a large surface of gas to the liquor
which, as it becomes saturated and lighter, rises to the top
of the body of the absorber and is ready to be drawn off by
the pump. Instead of spiral cooling coils, this type is often
made with straight cooling tubes inserted between two tube
sheets, boiler fashion. This straight tube construction is
much simpler and cheaper, and much more easily cleaned
than the spiral type. It is favored by some on this account,
especially where the cooling water has a tendency to form
scale.
Atmospheric absorbers resemble atmospheric condensers of
the single tube type. The ammonia gas and weak liquor en-
ter the bottom through a fitting commonly called a mixer,
and the two fiow upward through the inside of the pipe
while the cooling water is in contact with the outside thus
taking up the heat of absorption generated within the pipes.
REFRIGERATION 301
Concentric tube absorbers are very similar in design to con-
centric tube condensers, the cooling water passing through
the central tube and the weak liquor and expanded gas en-
tering at the bottom of the annular space and circulating to
the top, absorption taking place on the way. Because of the
small capacity of the last two mentioned absorbers, it Is
necessary to use with them an aqua ammonia receiver be-
tween the absorber and the ammonia pump, to act as a
reservoir for storing a reserve supply of the strong liquor.
Horizontal and vertical tubular absorbers are those in which
the cooling surface is composed of straight, horizontal or
vertical tubes inserted between tube sheets, the cooling
water flowing inside the tubes and the absorption taking
place within the drum or body of the absorber.
201. Bxchangrers may be of two types, the shell type
or the concentric tube type. The shell type, as the name im-
plies, is composed of a main body or shell through which
circulates the strong liquor to be heated and within this
shell is a coil or other arrangement of heating pipes through
which the hot, weak liquor flows. Fig. 142 shows the ele-
mentary arrangement of such an exchanger. Concentric
tube exchangers are used on large plants. They are similar
in every way to the concentric tube condensers shown in
Fig. 135, with the exception that larger pipes are needed
for the exchangers. The cold, strong liquor is usually car-
ried through the pipes and the hot, weak liquor through the
annular space. The great advantage of this type of ex-
changer is the same as that of the concentric tube con-
denser, namely, the counter flow of the two streams. With
this arrangement the total transfer of heat is a maximum,
for which reason this type of exchanger is generally pre-
ferred.
202. Coolers for the weak liquor are often found In
plants. This piece of apparatus is not indicated in Fig, 142.
It is usually installed as the lower three coils of the atmos-
pheric condenser, and hence is simply a small condenser
used to further cool the weak liquor just before its entrance
into the absorber. With a counter flow, concentric tube ex-
changer a weak liquor cooler is seldom found necessary.
203. The Pump used in absorption systems to raise the
pressure of the strong aqua ammonia may be steam driven,
electric driven or belt driven, as best suits the particular
plant conditions. The power required by this piece of appa
302 HEATING AND VENTILATION
ratus is about one horse power per 20 to 25 tons of refriger-
ation capacity.
204. Compression Systems and Absorption Systems Com-
pared: — A comparison drawn between the compression sys-
tem and the absorption system brings out the following
facts. The compression system depends fundamentally upon
the transferring of heat energy into mechanical energy and
vice versa, with the attendant heavy losses. The absorption
system merely transfers heat from one liquid to another.
This is a process which is attended by only moderate losses. ■
The compression systeim is comparatively simple, Its pro-
cesses readily understood and its machinery easily kept in
good running order. The absorption system is complicated
with a greater number of parts, its processes are often not
thoroughly understood by those in charge and its machinery
is likely to become inefficient because heat transferring sur-
faces are allowed to become dirty. For these reasons the
attendance necessary upon an absorption plant must be of a
higher order than that necessary for a compression plant.
205. Circulating Systems: — The refrigerating effect pro-
duced by either one of the two systems may be delivered to
the place of application in two ways. The first is the brine
circulation method wherein a brine cooler is used through
which the brine flows causing the evaporation of the liquid
refrigerant and the cooling of the brine. This cold brine is
then circulated through pipes to the place where refrigera-
tion is desired. Fig. 138 shows an evaporator placed in one
end of a large brine tank. The refrigerating effect is car-
ried to the cans of water by the circulation of this body of
brine through the evaporator and out past the cans, the cir-
culation through the channels shown being maintained by
the pump. Brine, commonly used for such work, is made by
dissolving calcium chloride in water. A 20 per cent, solu-
tion is generally used. Salt brine is used to some extent
but it has many disadvantages compared with calcium brine.
The second method is the direct circulation method wherein the
liquid refrigerant is conveyed to the place to be cooled, is
passed through an expansion valve and then circulated
through coils in the space to be refrigerated, changing into
gaseous form as fast as it can absorb enough heat. If
ammonia is the refrigerant the direct circulation is not often
favored because of its highly penetrative nature and odor,
even a leak so small as to escape detection being sufficient
REFRIGERATION
303
to fill the refrigerated space with the odor, which 'many
food stuffs will absorb.
206. There are Three Methods Employed for Maintain-
ing; r<ow Temperatures in storage and other rooms. The
first is by direct radiation where the pipes are placed within
the room and the refrigerant is circulated through them.
This is the oldest, simplest and cheapest system to install.
In this the proper location and arrangement of the pipes are
essential to the most efficient operation. Since the tempera-
ture to be maintained in a storage room depends upon the
products to be kept in the room, it may be necessary to have
a considerable range of temperature. It is desirable to have
the pipes arranged as coils in two or three sets, each being
valved so that the amount of refrigerant being circulated
may be increased or decreased as the temperature of the
stored product may require.
The pipes should be set out from the wall several inches
to give free air circulation and keep the frost that collects
on them from coming into contact with the wall. The coils
should be so placed that the temperature of all parts of the
room may be kept as nearly uniform as possible. Some
products keep as well in still air as when it is in motion, but
others, such as fruits, eggs, cheese, etc. are better pre-
served when the air is circulated. Circulation may be ef-
fected in a room piped for direct radiation by putting aprons
over the coils as shown in Fig. 146. These aprons consist of
12 inch boards D nailed to
studding E and the whole
fastened to the coils, the
studding serving to keep the
boards from coming into
contact with the pipe coils.
A false ceiling F is placed a
few inches below the ceiling
of the room so that the
warm air flows towards the
pipes and over them, drop-
ping to the floor and passing
out under the lower edge of
the apron into the room.
Wherever direct radiation is
used drip pans should be
placed directly underneath the coils in order to catch and
drain off the water when the coils are cut out and the frost
wyyyyy y'/^^/^yy//^/y/yy// /y////M
Fig. 14 6.
304
HEATING AND VENTILATION
melts. This water should be drained into a receptacle that
can be easily emptied when filled.
The second method of room cooling is by indirect radiation.
Let Fig. 147 represent a section of a storage building. The
essential parts of the cooling system are,
a bunker room AC, in the top part of the
building, containing the cooling coils
B, a series of ducts on either side of the
building, so arranged that the air after
passing over the cooling coils, drops
downward. These ducts are provided
with dampers for admitting as much of
the cold air to the rooms as is desired.
On becoming warmed this air is crowded
out on the opposite side of the room into
the ducts K and rises to the bunker-
room where it is again cooled by passing
over the coils. By the use of the damp-
ers the cold air may be cut off froni any
room or admitted in large quantities
thus making it an easy matter to main-
tain the temperature at any point de-
sired. The ducts leading the air from
the rooms should be 25 per cent, larger
than the ones leading to the roams and
the latter should have about three square
inches cross-section per square foot of
floor area in rooms having a ten foot
ceiling.
The third method is by means of a
plenum system of air circulation. Fig. 148. The arrangements
are quite similar to those of the plenum system for heating,
^ except that the heating coils
are replaced by the refrigerat-
ing coils. The air required for
ventilation is blown over the
coil surface, erected in a coil
or bunker room, over which,
oftentimes, cold water is
sprayed. This not only washes
the air but tends to lower its
temperature. If ammonia is
used as a refrigerant, brine is
Circulated In the coils, but if
Fig. 147.
= — t^ZS^""
Fig. 148.
REFRIGERATION 805
carbon dioxide Is used direct expansion Is employed, thus
dispensing with the use of brine. The principal advantage
of the plenum system of cooling is that a positive circulation
of air may be maintained in any room even though the
bunker room be placed on the first floor or in the baseonent
of the building. This is the system used in large buildings
that are cooled during the summer as well as heated dur-
ing winter, in factories where changes of temperature seri-
ously affect the product, as in chocolate factories, in fur
storage rooms, in drying the air before it is blown into blast
furnaces and in the solution of many other important eco-
nomic problems.
207. Influence of the Dew Point: — In cooling a building
by means of a plenum refrigerating system, great trouble
is experienced with the formation of ice on the coils. For
example, suppose such a cooling system on a hot summer
day is taking in air at 90 degrees temperature and 85 per
cent, humidity. If this air is cooled only ten degrees (see
chart, page 29), it will have reached its dew point and as
the cooling continues will deposit frost and ice on the coils
from the liberated moiisture, the air meantime remaining at
the saturation point and being so delivered to the rooms. The
undesirable feature of delivering saturated air to the rooms
may be avoided by cooling only part, say half of the air
stream, considerably lower than the final temperature de-
sired, and then mixing it with the other half, which is
drier, before delivering it to the rooms. The troublesome
coating of ice and frost on the pipes may be avoided by
combining the cooling system with the air washing system
and using a brine spray instead of water for washing the
air during cooling. The brine, which freezes at a very low
temperature compared with water, plays over the cooling
coils, and cleans both coils and air. The brine should pref-
erably be a chloride brine. A modification of this method of
avoiding ice and frost is to provide pans above the coils
and fill them with lumps of calcium chloride. The pans
have perforations so arranged that as the strong chloride
solution forms (due to the deliquescence of the salt) it
trickles down oyer the pipes and holds the freezing point
of any collecting moisture far below the temperature of the
coils. ;A sketch of this arrangement is shown in Fig. 149,
which has the disadvantage of the clumsy handling of the
calcium chloride. Plants operating only during the day, as for
306
HEATING AND VENTILATION
ORlOC OF OILOUM
FIgr. 149.
Instance, auditoriums, commerce chambers, etc, often have
no equipment for preventing the accumulation of frost and
ice, it being allowed to form during the short period of use
and to melt during the period of rest.
208. Pipe Line Refrigeration: — In a number of the
larger cities refrigeration is furnished to such places as
cold storage rooms, restaurants, hotels, auditoriums, etc.,
by a conduit system or central station system. The length
of the mains in the various cities where used, ranges from
a few hundred feet to twenty miles and the circulating
medium employed is either liquid ammonia or brine. In the
ammonia system two pipes are used, one carrying the liquid
ammonia to the place desired and the other returning it
after expansion to the central station. When brine is u?ed
It is good practice to circulate it at froml2 to 15 degrees P.
Occasionally the conduits carry three parallel pipes, two of
which are for circulating the brine and the third is for
emergency cases. The line should be divided into sections,
with valves and by-passes so arranged that a defective sec-
tion could be repaired without interfering with the other
parts. All valves should be readily accessible and all high
points In the system should be equipped with purge valves.
REFRIGERATION
307
The service pipes should be two inches in diameter and
well insulated.
Either the ammonia absorption or compression system
may be used for cooling the brine but according to Mr. Jos.
H. Hart, the latter, making use of direct expansion, is the
most efficient and the one most commonly installed. The
loss by radiation to the pipes in the conduits is not great but
numerous mechanical difficulties are yet to be overcome. It
would seem desirable to make the pipe-line system of cool-
ing general for residence use but as yet it has not been
found economical to cool build-
ings using less than the
equivalent of 500 pounds of re-
frigeration in 24 hours. Al-
8*^^*«BMs| though not an efficient method,
<?=*' it seems probable that cold air
refrigeration by using balanced
expansion may supersede the
other systems.
209. As a Final Application
of refrigeration we may men-
tion the cooling of the drinking
water supply in large office
buildings, hotels, etc. Usually
this is simply a small part of
the work of a large refrigerat-
ing plant. Fig. 150 gives a dia-
grammatic elevation of such an
WMmMMmmmm . arrangement.
Fig. 150.
CHAPTER XVII.
REUETRIGKRATION CALCULATIONS.
210. Unit Measurement of Refrigreration: — Since the
first efforts toward refrigeration employed the simple pro-
cess of melting ice by the abstraction of heat from nearby
articles, it is not surprising to find the accepted standard
unit for expres-sing refrigeration capacities referred to the
refrigerating effect of a known quantity of ice. In fact,
since the latent heat of fusion of ice is a constant, this
furnishes an excellent (basis for estimating refrigeration.
The generally accepted unit of measure Is the ton of refrigera-
tion, which may be defined as the amount of heat (B. t. u.) which
one ton of 2000 pounds of ice at S2 degrees, toill absorb in melting to
tcater at S2 degrees. Since the latent iheat o^ ice is 144 B, t. u.
per pound, one ton of Tefrigeration is equal to 288000 B. t. u.
Just as a pumiping plant is rated at a certain number of
millions of gallons, meaning millions of gallons in twenty-
fo-ur hours, so a refrigeration plant is rated in so many
tons of refrigeration, meaning so many tons in twenty-four
hours. Hence one ton of refrigeration capacity for one day
is equivalent to 12000 B. t. u. pe-r hour, this value being the
unit of refrigerating capacity, sometimes referred to as tonnage
capacity, or refrigerating effect, and usually designated by T.
211. Calculation of Required Capacity: — To estimate
closely the tonnage capacity of a refrigerating plant for
any certain store space requires specific attention to supply-
ing the folQowing losses:
(a) The radiated and conducted heat entering the
room. This may be divided into that due to the walls and
that due to the windows and sky-lights.
(lb) The heat entering iby the renewal of the air, or
ventilation of the enclosed space. This may be divided Into
heat given off by the air and iheat given off due to the
latent iheat of the moisture.
(c) The heat entering by the opening of doors.'
•(d) The heat from the men at work, lights, chemical
fermentation processes, etc.
(e) The heat abstracted from material In cold storage.
Refrigeration losses due to entrance of radiated and con-
ducted heat may be calculated by formulas 10, 11 and 12,
REFRIGERATION
309
Chapter III, if the proper transmission constants are in-
serted. To obtain these constants for various types of in-
sulation use Tables IV and XXIX.
TABLE XXIX.
Heat Transmission of Standard Types of Dry Insulation.
Material
Mill
1"
2"
3"
4"
5"
6"
7"
8"
10"
12"
14"
16"
18"
20"
22"
24"
shavings, Type (a)
thickness
K
.1330
.1090
.0920
.0800
.0710
.0630
.0570
.0520
.0440
.0390
.0340
.0308
.0279
.0255
.0235
.0218
Material
Hair Felt, Type (a)
1" thickness
M". Vz", Vi", Type (c)
Sheet Cork, Type (d)
4" with 1" air space
5" with V air space
3", Type (b)
1", Type (a)
Granulated Cork
4", Type (a)
Mineral Wool
2%", Type (b)
1", Type (b)
Air Spaces
8", Type (a)
K
.138
.105
.050
.037
.087
.137
.071
.151
.192
.112
^TAR FVXPER
SHAVING 5
TAR f^PtlR^
/^^ORK^
In general any space to be kept at or below zero degrees
should have insulation allowing no greater transmission
than .04, and for spaces to be kept at from degrees to 30
310 HEATING AND VENTILATION
degrees no greater transmission should be allowed than .06,
while for temperatures above 30 degrees a transmission as
great as .1 is allowable. In any case, however, it should be
remembered that the heat loss, and therefore the expense of
operation, is directly proportional to this factor and the
beat possible insulation, consistent with available building
funds, is the one to use, the ceiling and floor being as care-
fully insulated as the walls. Window construction should
be tight, non-opening, and at least double.
The refrigeration loss due to ventilation may be considered
under two heads, i. e., the cooling of the air from the
higher to the lower temperature, and the cooling, condens-
ing and freezing of the moisture in the air. In this par-
ticular, air cooling cannot be considered exactly the re-
verse of air warming. In air warming the vapor present
absorbs heat but this vapor has so little heat capacity com-
pared with that of the air tha.t no noteworthy error is intro-
duced by ignoring the vapor. However, in air cooling the
dew point is almost invariai)ly reached and passed, so that
considerable moisture is changed from the vapor to tlie
liquid with a liberation of its heat of vaporization. This is
considerable and cannot be ignored without serious error.
If, further, conditions are such that this moisture is frozen,
its latent heat of freezing must also be accounted for.
These two items are relatively so large that to cool air
through a given range of temperature may involve several
times the heat transfer required to warm the same air
through the same range of temperature.
Application. — Assume outside air 95 degrees, relative
humidity 85 per cent., temperature of air upon leaving cool-
ing coils 30 degrees and temperature of coil surface 10 de-
grees. If 180000 cubic feet of air per hour are drawn in
from the atmosphere, the refrigerating capacity of the coils
may be obtained as follows. To cool the air from 95 degrees
to 30 degrees will require (formula 9),
180000 X (95 — 30)
= 212700 B. t. u.
55
At 95 degrees and 85 per cent, humidity one cubic foot of
air contains, (Table 10. Appendix,) .85 X 17.124 = 14.555
grains of moisture. At 30 degrees and saturation one cubic
REFRIGERATION. 311
foot of air contains, (Table 10), 1.935 grains. Hence there
180000 (14.555 — 1.935)
would be deposited upon the coils
7000
324.5 pounds of moisture per hour. Now there would be
absorbed from each pound of this moisture
32 B. t. u. to cool from 95 to 32 degrees.
1073 B. t. u. to change to liquid form.
144 B. t. u. to freeze (if allowed to freeze on coils).
11 B. t» u. to cool from 32 to 10 degrees.
1260 B. t. u. total.
Hence the coils would have to absorb from the moisture
alone, 1260 X 324.5 = 408870 B. t. u. per hour, or for both
moisture and air, 212700 + 408870 = 621600 B. t. u. per hour.
This indicates, for the ventilation proposed, a tonnage capac-
ity of 621600 -r- 12000 = 51.8 tons of refrigeration needed at
the bunker room coils; The above provides that the air is
rejected at the interior temperature, 30 degrees. Modern
plants, however, would pre-cool the incoming air before it
reached the bunker room by having part of its heat ab-
sorbed by the outgoing 30 degree air, which would reduce
the estimate somewhat below 51.8 tons.
In considering the refrigeration loss due to the opening of
doors no rational method of calculation is applicable, but if
the nature of the cold storage service is such that doors are
frequently opened, as high as 25 per cent, may be allowed.
Generally this is taken from 10 to 15 per cent.
The refrigeration loss due to persons, lights, etc., may be
estimated as suggested in Art. 31. If the cooling air is
recirculated, the cooling and freezing of the moisture given
off by each person should be taken into account, especially
if the number is large. For this purpose it is safe to assume
a maximum of 500 grains of moisture given off per person
per hour when such persons are not engaged in active phy-
sical exercise.
212. Calculations for Square Feet of Cooling: Coil: — This
problem presents greater uncertainty in its solution than
does the design of a heating coil surface because of the lack
of experimental data and because of the variable insulat-
ing effect of ice and frost accumulations, if allowed to form.
Professor Hanz Lorenz in "Modern Refrigerating Machin-
ery," page 349, quotes 4 B. t. u. per square foot per hour per
312 HEATING AND VENTILATION
degree difference between the average temperatures on the
Inside and outside of the coils, as a safe designing value
when the air speed is 1000 feet per minute over the coils.
This is for plants in continuous operation, as abattoirs, cold
stores and in places where no provision is made against ice
formation. For clean pipe surface in the plenum air cooling
plant of the New York Stock Exchange Building the heat
transmission is approximately 430 B. t. u. per square foot
per hour with air over coils at 1000 feet per minute. Under
the average temperatures there used, this corresponds to a
transmission per degree difference per square foo.t per hour
of approximately 7 B. t. u. These two values. 4 and 7, may
be taken as about the minimum and maximum transmission
constants for plenum cooling coil installations.
For direct cooling coils, where the pipe surface is sim-
ply exposed to the air of the room to be cooled. Lorenz
recommends a transmission allowance of not over 30 B. t. u.
per square foot per hour, for in such Installations the re-
moval of ice and frost is seldom contemplated. For an aver-
age room temperature of 30 degrees and average brine tem-
perature of 10 degrees, this would correspond to 30 ^ 20 =
1.5 B. t. u. transmitted per square foot per hour per degree
difference.
Application 1. — How many lineal feet of 1% inch direct
refrigerating coils would be required to keep a cold stor-
age room at 30 degrees if the refrigeration loss 4s 80000
B. t. u. per hour total and the temperatures of the brine en-
tering and leaving the coils are 10 degrees and 20 degrees
respectively? Average brine temperature = 15 degrees. Al-
lowing a transmission constant of 1.5, formula 30 becomes,
H
Rr = = — .0445 H
1.5 (15 — 30)
For this problem we have .0445 X 80000 = 3500 square feet,
or 3500 X 2.3 = 8050 lineal feet of 1^ inch pipe,
vApplicatiox 2.— The cooling of 180000 cubic feet of air per
hour in Art. 211 required the extraction of 621600 B. t. u. per
hour. Determine the plenum cooling surface required, if
brine enters at degrees and leaves at 20 degrees.
Average brine temperature = 10 degrees. Assuming
that there is provision for 1 eeping coils clear of ice. and
REFRIGERATION 313
hence a transmission constant of 7 B. t. u. Is allowable,
formula 42 gives
621600
Rr = = — 1691 square feet of surface.
/ 95 + 30 \
The negative sign indicates a flow of heat in the direc-
tion opposite to the flow in heating installations, for which
the formula was primarily designed.
213. Genera] Application: — Considering the school build-
ing and the table of calculated results on pages 202 to 205
what amount of cooling coil surface would be required to
keep the temperature of all rooms of this building at 73
degrees on a day when the outside air temperature is 95
degrees and the relative humidity 85 per cent.?
Data Table XXV gives the total heat loss of the three
floors of this building as 1483250 B. t. u. per hour on a zero
day when the rooms are kept at 70 degrees. Now this same
building under the summer conditions would have delivered
to it heat due to a temperature difference of 95 degrees — 73
degrees = 22 degrees. Hence the total refrigeration loss dur-
22
ing the summer day would be approximately X 1483250 =
70
466000 B. t. u. per hour, which amount of heat would be used
to warm the incoming air from some temperature up to 73
degrees. Suppose the ventilation requirement of the build-
ing is 2000000 cubic feet per hour. Since it requires ^^^^ of
a B. t u. to warm one cubic foot of air one degree, [2000000
(73 — <)] -^ 55 = 466000, or t = 60.2, say 60 degrees. (See
Arts. 36 and 38 and observe that the second term of the right
hand member of formula 17 becomes a negative term).
While .the air is traversing the ducts between the coils
and the rooms, allow a rise in temperature of 5 degrees.
The coiLs would then be required to deliver 2000000 cubic
feet of air per hour at 55 degrees when supplied wILth air at
90 degrees and 85 per cent, humidity. To cool this amount
of air through the given range would require the absorption
of (formula 9), [2000000 X (95 — 55)] ^ 55 = 1454500 B. t. u.
At 95 degrees and 85 per cent, humidity, 1 cubic foot of air
contains (Table 10), .85 X 17.124 = 14.555 grains of moisture.
At 55 degrees and saturation point, 1 cubic foot of air con-
tains (Table 10), 4.849 grains of moisture. Hence, neglecting
314 HEATING AND VENTILATION
change In air volume, there would be deposited on the colls
approximately [2000000 (14.555 — 4.849)] -^ 7000 = 2775
pounds of moisture per hour.
Now, if an average brine temperature of 10 degrees is
used and provision is made for keeping the coils clear of ice,
the condensation will leave at some temperature above 10
degrees, say 20 degrees, and there will be absorbed from
each pound of this moisture approximately
20 B. t. u. to cool from 95 to 55 degrees.
1061 B. t. u. to change to liquid form at 55 degrees.
35 B. t. u. to cool the water from 55 to 20 degrees.
1116 B. t. u. total.
Hence the coils would have to absorb from moisture alone,
2775 X 1116 = 3096900 B. t. u., or from both moisture and air
a total of 1454500 + 3096900 = 4551400 B. t. u. per hour. At
an allowed rate of transmission of 7 B. t. u. there would be
required to cool this building a total of approximately 9100
square feet of coil surface, under the conditions of ventila-
tion as assumed.
It should be noted that whereas only 3000 square feet
of plenum surface were sufficient to heat the building ac-
cording to Application 2, Art. 115, it requires fully three
times this amount of surface in cooling coils to cool the
building under the assumed conditions. Upon inspection It
is seen that the greatest work of the cooling coils is the
condensation and cooling of the moisture.
The relative humidity within the cooled rooms would be
approximately 55 per cent., for the content per cubic foot of
incoming air is 4.849 grains, and the capacity of the air
when heated to 73 degrees is 8.782 grains showing a relative
4.849
humidity, after heating, of = 55 per cent. This would
8.782
be raised somewhat by the persons present.
214. Ice Making: Capacity. Calculation: — Neglecting
losses, the ice making capacity of a refrigerating plant for
a certain refrigeration tonnage may be expressed
144 T
J =. (1T)7)
(t — 32) + 144 + -5 (32 — fi)
in which / = tons of ice produced per 24 hours, T = refrlg-
REFRIGERATION 315
eration tonnage or rating of plant, t = initial temperature of
water and <i = final temperature of ice, usually 12 to 18
degrees.
• Application. — What should be the ice making capacity of
a plant having a tonnage rating of 100, if * = 70 degrees and
h = 16 degrees? Take losses at 35 per cent.
.65 X 144 X 100
I = = 49.3 tons in 24 hours.
(70 — 32) +144 + .5 (32 — 16)
215. Gallon Degree Calculation: — For use in plants pro-
ducing ice by brine circulation a unit called the gallon degree
is sometimes used. It represents a change of one degree
temperature in 1 gallon of brine in one minute of time.
It is not a fixed unit representing a constant num-
ber of B. t. u., since the brine strength, and therefore its
specific heat, may vary. The value in B. t. u. per minute, of
a gallon degree for any plant may be obtained by multiply-
ing the specific gravity of the brine by its specific heat and
by 8.35, the weight of one gallon of water, or as a formula
may be stated
D = 8.35 gh (108)
where D = B. t. u. per minute equal to one gallon degree,
g = specific gravity of brine and h = specific heat of brine.
The number of gallon degrees per ton of refrigerating capacity may
be found by dividing 200 by D, since one ton of refrigerating
capacity is equal to 200 B. t. u. per minute, then
200 24
Dt = = for all practical purposes. (109)
8.35 gh gh
The refrigerating capacity of a given brine circulation may be
obtained by dividing the product of the gallons circulated
and the rise in brine temperature by the value Dt. Stated
as a formula this is
0(t2 — ts) ghGCts — ts)
T = = (110)
Dt 24
where T = tonnage capacity, O = gallons of brine circu-
lated per minute and (tz — ts) = rise of brine temperature.
216. Refrig^erating: Capacity of Brine Cooled System: —
To calculate the capacity but two things are required, the
amount of brine circulated, and the rise in temperature of
the brine. From these the capacity may be obtained by
the formula
<{16 HEATING AND VENTILATION
W h (t2 — is)
T = (111)
12000
where T = tonnage capacity, W = weight of brine circulated.
in pounds, h = specific heat of brine and (?2 — 's) = rise in
temperature of brine.
217. Cost of Ice Making and Refrigeration: — The cost of
ice manufacture is affected principally by the following
items: price and kind of fuel. Icind of water, cost of labor,
regularity of operation, method of estimating costs, etc.
It is found in practice to range anywhere from $0.50 to
$2.50 per ton. The items making up the cost of ice manu-
facture are: fuel for power, labor at the plant, water, am-
monia and minor supplies, maintenance of the plant, inter-
est and taxes, and administration. Mr. J, E. Siebel in his
"Compend of Mechanical Refrigeration and Engineering"
gives an itemized account of the daily operating expense of
a 100-ton plant with which he was connected, the plant
operating 24 hours per day.
Chief engineer $ 5.00
Assistant engineers 6.00
Firemen 4.00
Helpers 5.00
Ice pullers 9.00
Expenses 12.00
Coal at $1.10 per ton 18.00
Delivery (wholesale) 50c per ton 50.00
Repairs, etc 3.00
Insurance, taxes, etc 6.00
Interest on capital 20.55
Total for 100 tons of ice $138.55
The length of time that the ice i? permitted to freeze
is a factor affecting the cost of production. The following
figures are given for a 10-ton plant:
Ten tons Ten tons
In 12 hours in 24 hours
Engineer $2.50 $ 5.00
Fireman . 1.50 3.00
Tankmen, helpers . . 1.50 3.00
Coal 3.00 3.00
Repairs, supplies, etc. 1.50 1.50
Total for 10 tons $10.00 $15.50
REFRIGERATION
317
Mr. A. P. Criswell, in "Ice and Refrigeration," gives the
following approximate costs for the production of can ice
per ton with coal at $2.50 per ton and with a simple distill-
ing system. The figures are for the plant operating at full
capacity and do not include cost of administration.
Capacity of plant Cost per ton
10 tons $1.58
20 " 1.48
30 " 1.42
40 " 1.38
50 " 1.36
70 " 1.34
100 " l.?4
120 " 1.30
Mr. Karl Wegemann states that a certain moderate sized
plant of the absorption system produced ice for a number
of years at an average cost of $0.85 per ton after allowing
for melting and breakage. This included all charges ex-
cept for interest, insurance and administration.
The following figures taken from the books of another
plant show clea,rly the effect of demand upon the cost of
manufacture.
Month Cost per ton
January $3.50
February 3.70
March 2.80
April 2.17
May 1.75
June 1.19
July 1.02
August 1.02
September 1.03
October 1.26
N9vember 2.10
December 2.94
318 HEATING AND VENTILATION
REFERENCES.
References on Refrigeration.
Technical Books.
A. J. Wallis-Taylor, Pocket-Book of Refrigeration. John
Wemyss Anderson, Refrigeration. James Alfred Ewing, Mechan-
ical Refrigeration. J. E. Siebel, Compend of Mechanical Refriger-
ation. International Library of Technology, pp. 643-966. I. C. S.
Pamphlets, 1238 A, 1238 B, 1238 C. 1240, 1241. 1242, 1243,
1246 A, 1246 B, 1247 and 1250. American School of Corre-
spondence; Refrigeration, Dickerman & Boyer; Refrigeration, Mil-
ton W. Arrowwood.
Technical Periodicals.
Ice and Refrigeration. The Ice Factory of the Future, Vic-
tor H. Becker, Jan. 1910. Cell Box System for Making- Raw
Water Ice, A. C. Bishop. Dep. 1909. The Flooded System, H.
Rassbach, Jan. 1910. Baker Chocolate Cooling Plant. Aug.
1910. The Working Fluid in Refrigeration, H. J. Maclntyre,
Nov. 1910. Sulphur Dioxide as Refrigerating Agent, W. S,
Douglas, Oct. 1911. Dry Blast Refrigeration, Nov. 1912.
Power, Artificial Systems of Refrigeration, C. P. Wood, May
3, 1910. Mechanical Refrigeration, F. E. Matthews, Aug. 9,
1910. Elements of Compression System, F. E. Matthews,
Sept. 6, 1910. Can and Plate Systems of Making Ice, F. E.
Matthews, Mar. 14, 1911. Cold Storage of Furs and Fabrics,
E. F. Tweedy, Feb. 20, 1912. Ammonia Absorption Refrig-
eration System, Fred Ophuls. Apr. 23, 1912. Cent-ral Refrig-
erating Plant at Atlanta. Georgia. May 7, 1912. Pre-Cooling
Plant of Southern Pacific Railway, LeRoy W. Allison, June
4. 1912. Cooling Air of Buildings by Mechanical Refrigera-
tion, E. F. Tweedy, Nov. 28. 1911. Electrical World. Ice Mak-
ing from Exhaust Steam, Apr. 7, 1910.
CHAPTER XVIII.
PLANS AND SPECIFICATIONS FOR HEATING SYSTEMS.
218. In Planning^ for and Exeoutlng Engineering Con-
tracts, the responsibilities assumed by the various interested
parties should be thoroughly studied. The following outline
shows the relationship between these parties and the order
of the responsibility.
^ /Engineer.
Owner I „ .
I Superintendent and Inspector.
or /
--, , \ General contractor, Subcontractors, Foremen and
Purchaser I
I Workmen.
The engineer, the superintendent and the general con-
tractor occupy positions of like responsibility with relation
to the purchaser. The first two work for the interest of the
purchaser to obtain the best possible results for the least
money, and the last endeavors to fulfill the contract to the
satisfaction of the superintendent, at the least possible ex-
pense to himself. These points of view are quite different
and sometimes are antagonistic, but both are right and just.
Of the three parties, the engineer has the greatest respon-
sibility. It is his duty to draw up the plans and to write
the specifications in such a way that every point is niade
clear and that no question of dispute may arise between the
superintendent and the contractor. His plans should detail
every part of the design with full notes. His specifications
should explain all points that are difficult to delineate on the
plans. They should give the purchaser's views covering all
preferences, and should definitely state where and what ma-
terials may be substituted. Where any point is not definitely
settled and left to the judgment of the contractor, he may
be expected to interpret this point in his favor and use the
cheapest material that in his judgment will give good re-
sults. This opinion may differ from that held by the pur-
chaser. All parts should be made so plain that no two opin-
ions could be had on any important point. The engineer
should also be careful that the plans and specifications agree
in every part. The inspector is the superintendent's repre-
sentative on the grounds and is supposed to inspect and
pass upon all materials delivered on the grounds, and the
320 HEATING AND VENTILATION
quality of workmanship In installing-. For such Information
see Byrne's "Inspector's Pocket-Book." The general con-
tractor usually sublets parts of the contract to subcon-
tractors who work through the foreman and workmen to
finish the work upon the same basis as the general con-
tractor.
The following brief set of specifications are not con-
sidered complete but are merely inserted to sugg'est how
such work is done.
Typical Speoifientlons.
Title Page: —
SPECIFICATIONS
for the
MATERIALS AND WORKMANSHIP
Recruired to Install
(Type of system)
HEATING AND VENTILATING SYSTEM
in the
(Building)
(Location)
by
(Name of designer)
IxDEX Page: —
(To be compiled after the specifications are written.)
General Remarks to Contractor. — In the following specifi-
cations, all -references to the Owner or Purchaser will mean
or any person or persons delegated by
to serve as the representative. The Super-
intendent of Buildings will be the purchaser's representative at
all times, unless otherwise definitely stated. The contractor
will, therefore, refer all doubtful questions or misunder-
TYPICAL SPECIFICATIONS S21
standings, if any, to the superintendent, whose decision wlli
be final. In case of any doubt concerning the meaning of
any part of the plans or specifications, the contractor shall
obtain definite interpretation from the superintendent be-
fore proceeding with the work.
These specifications with the accompanying plans and
details (sheets .... to .... inclusive) cover the purchase of
all the materials as specified later (the same materials to
be new in every case), and the installation of the same in a
first class manner within the above named building, located
at . (street) .... (city) .... (state).
It will be understood that the successful bidder, herein-
after called the contractor, shall work in conformity with
these plans and specifications and shall, to the best of his
ability, carry out their true intent and meaning. He shall
purchase and erect all materials and apparatus required to
m-ake the above system complete in all its parts, supplying
only such quality of materials and workmanship as will har-
monize with a first class system and develop satisfactory
results when working under the heaviest service to which
such plants are subjected.
The contractor shall lay out his own work and be re-
sponsible for its fitting to place. He shall keep a competent
foreman on the grounds and shall properly protect his work
at all times, making good any damage that may come to it,
or to the building, or to the work of other contractors from
any source whatsoever, which may be chargeable to himself
or to his employees in the course of their operations.
Any defects in materials or workmanship, other than
as stated under — (state exceptions if any) — ^that may develop
within one year, shall be made good by the contractor upon
written notification from the purchaser without additional
cost to the purchaser.
The contractor shall, wherever it is found necessary,
make all excavations and back-fill to the satisfaction of the
superintendent.
The contractor shall be responsible for all cuttings of
wood work, brick work or cement work, found necessary
in fitting his materials to place, either within or without the
building; the cutting to be done to the satisfaction of the
superintendent. The contractor shall be required to connect
and supply water and gas for building purposes, and shall
322 HEATING AND VENTILATION
assume all responsibility for the same.
The contractor shall be required to protect the purchaser
from damage suits, originating from personal injuries re-
ceived during the progress of the work; also, from actions
at law because of the use of patented articles furnished by
the contractor; also, from any lien or liens arising because
of any materials or labor furnished.
The purchaser reserves the right to reject any or all
bids.
No changes in these plans and specifications will be
allowed except upon written agreement signed by both the
contractor and the purchaser's representative.
System. — Specify the system of heating in a general way;
high pressure, low pressure or vacuum; direct, direct-indi-
rect or indirect radiation; basement or attic mains; one
or two-pipe connections to radiators. If ventilation is
provided, state the movement of the air and the general
arrangement of fans, coils or other heating surfaces. Single
or double duct air lines, etc.
Boilers. — ^Specify type, number, size and capacity, steam,
pressure, approximate horse-power, heating surface, grate
surface and kind of coal to be used. Locate on plan and ele-
vation. Explain method of setting, portable or brick.
Specify also, flue connection, heating and water pipe con-
nections, kind of grate, thermometers, gages, automatic
damper connection, firing tools and conditions of final tests.
Conduits and Conduit Mains. — (In this it is assumed that the
boilers are not within the building). In addition to the lay-
out, give sections of the conduit on plans sliowing method
of construction, supporting and insulating pipes, and drain-
age of pipes and conduits. Specify quality and size of mate-
rials, pitch and drainage of pipes and all other points not
specially provided for in the plans.
Anchors. — Locate and draw on plans and specify for the
installation regarding quality of materials.
Expansion Joints or Take-ups. — Locate and draw on plans.
Select type of joint and specify for amount of safe take-up
and for quality of material.
Mains and Returns. — Trace the steam from the point where
It enters the main, through all the special fittings of the
system. Show where the condensation is dripped
to the returns tlirough traps or separating devices. Specify
TYPICAL. SPECIFICATIONS 323
amount and direction of pitch, kind of fittings (flanged or
screwed, cast iron or malleable iron), kind of corners (long
or short), method of taking up expansion and contraction.
Trace returns and specify dry or wet.
Branches to Risers. — Take branches from top of mains by
tees, short nipples and ells, and enter the bottom of the
risers by sufficient inclination to give good drainage.
Risers. — Locate risers according to plan. They shall be
straight and plumb and shall conform to the sizes given on
the plans. No riser shall overlap the casing around win-
dows. State how branches are to be taken off leading to
radiators, relative to the ceiling or floor.
Radiator Connections. — 'Specify, one-pipe or two-pipe, num-
ber and kind of valves, sizes of connections and hand or
automatic control. All connections shall allow for good
drainage and expansion. Distinguish between wall radiator
and floor radiator connections. If automatic control is used,
hand valves at the radiators are usually omitted.
Radiators. — Specify floor or wall radiators, with type,
height, number of columns and number of sections. If other
radiators are substituted for the ones that are referred to
as acceptable, they must be of equal amount of surface and
acceptable to the superintendent. Specify brackets for wall
radiators, also, air valves for all radiators, stating type
and location on the radiator. Require all radiators to be
cleaned with water or steam at the factory and plugged at
inlet and outlet for shipment.
Piping. — Define quality, weight and material in all mains,
branches and risers. All sizes above one and one-half inch
are usually lap welded. Piping should be stood on end and
pounded to remove all scale before going into the system.
All pipes 1 inch and smaller should be reamed out full size
after cutting.
Fittings. — Specify quality of fittings, whether light, stand-
ard or heavy, malleable or cast iron. Fittings with imper-
fect threads should be rejected.
Valves. — Specify type (globe, gate or check), whether
flanged or screwed, rough or smooth body, cast iron or
brass, and give pressure to be carried. All valves should
be located on the plans.
Expansion Tank. — Specify capacity of tank in gallons, kind
324 HEATING AND VENTILATION
of tank (square or round, wood or steel), method of connect-
ing up with fittings and valves, and locate defini-tely on plan
and elevation. Connect also to fresh water supply and to
overflow.
Hangers and Ceiling Plates. — Wall radiators and horizontal
runs of pipe shall be supported on suitable expansion hang-
ers or wall supports that will permit of absolute freedom of
expansion. Supports shall be placed .... feet centers. Pipe
holes in concrete floors shall be thimbled. Holes through
wooden walls and floors shall have suitable air space around
the pipe, and all openings shall be covered with ornamental
floor, ceiling or wall plates.
Traps. — Specify type, size, capacity and location. State
whether flanged or screwed fittings are used and whether
by-pass connection will be pu)t in. Refer to plans.
Pressure Regulating Talve. — Specify type, size and location,
also maximum and minimum steam pressure, with guaran-
tee to operate under slight change of pressure. State if
by-pass should be used and explain with plans.
Separators. — Specify type (horizontal or vertical), also
size and location.
Automatic Control. — The contractor will be held responsible
for ithe installation of all thermostats, regulator valves, air
compressor, piping and fittings required to equip all rooms
and halls with an automatic .... temperature control sys-
tem. Specify approximate location and number of thermo-
stats with the desired finish. Specify in a general way, reg-
ulator valves on radiaitors, quality of pipe, maximum test
pressure for pipe, power for air supply (hydraulic, pneu-
matic, etc.), and supply tank. All materials in the tem-
perature control system shall be guaranteed first class by
the manufacturer through the contractor, and the system
shall be guaranteed to give perfect control for a period of
(two) years.
Fans. — Specify for direct connected or belt driven, right
or left hand, capacity, size, housing, direction of discharge,
horse-power, R. P. M. and pressure. State in a general way
the requirements of the fan wheel, steel plate housing, shaft,
bearings and the method of lubrication.
Engine. — Specify type, horse-power, steam pressure, ap-
proximate cut-off, speed and kind of control.
TYPICAL SPECIFICATIONS 325
Electric Motors. — Specify type, horse-power, voltage, cycles,
phases and R. P. M.
Indirect Heating Surface. — 'Specify the kind of surface to
be put in and then state the total number of square feet
of surface, with the width, height and depth of the heater.
Staite definitely how the heaters will be assembled, giving
free height of heater above the floor. Describe damper con-
trol, steam piping to and from heater, housing around heater,
connection from cold air inlet to heater and connection from
heater to fan. See plans. The contractor will usually follow
installation instructions given by the manufacturers for the
erection of the heater and engine, consequently the speci-
fications should bear heavily only upon those points which
may be varied to suit any condition. All valves, piping and
fittings in this work should be controlled by the general
specifications referring to these parts.
Foundations. — Specify materials and sizes.
Air Ducts, Stacks and Galvanized Iron Work. — The drawings
should give the layout of all the air lines, giving connections
between the air lines and the fan, and the air lines and the
registers. Where these air lines are below the floor, the
conduit construction should be carefully noted. All gal-
vanized iron work should be shown on the plans and the
quality and weight should be specified. Air lines should
have long raaius turns at the corners.
Registers. — Specify height above floor, nominal size of
register, naethod of fitting in wall, the finish of the regis-
ter and whether fitted with shutters or not.
Protection and Covering. — Specify kind and quality of pip6
covering and the finish of the surface of the covering. State
the amount of space between heating pipes and unprotected
woodwork. Distinguish between pipes that are to be covered
and those that are to be painted. All radiators and piping
not covered should be painted with two coats of .... bronze
or other finish acceptable to the superintendent.
Completion. — Require all rubbish removed from the build-
ing and immediate grounds and deposited at a definite place.
APPENDIX
L
GENERAL TABLES.
HEATING AND VENTILATION.
Tables in body of text are numbered in Roman
numerals, those in the Appendixes are numbered in
Arabic numerals.
All tables that are not considered general are credited
and added by permission of the authors.
327
TABLE 1.
Squares, Cubet*, Square RootM, Cube RootM, Circles.
No.
Square
Cube
Sq.
root
Cube
root
Circle
Diam.
Circumf
Area
.1
.010
.001
.316
.464
.314
.00785
.2
.040
.008
.447
.585
.628
.03146
.3
.090
.027
.548
.669
.942
.07069
.4
.160
.064
.633
.737
1.257
.12566
.5
.250
.125
.707
.794
1.570
.19635
.6
.360
.216
.775
.843
1.885
.28274
.7
.490
.343
.837
.888
2.200
.38485
.8
.640
.512
.894
.928
2.513
.50266
.9
.810
.729
.949
.965
2.830
.63620
1.0
1.000
1.000
1.000
1.000
3.1416
.7854
1.1
1.210
1.331
1.0488
1.0323
3.456
.9503
1.2
1.440
1.730
1.0955
1.0627
3.770
1.1310
1.3
1.690
2.197
1.1402
1.0914
4.084
1.3273
1.4
1.960
2.744
1.1832
1.1187
4.398
1.5394
1.5
2.250
3.375
1.2247
1.1447
4.712
1.7672
1.6
2.560
4.096
1.2649
1.1696
5.027
2.0106
1.7
2.890
4.913
1.3038
1.1935
5.341
2.2698
1.8
3.240
5.a32
1.3416
1.2164
5.655
2.5447
1.9
3.610
6.859
1.3784
1.2386
5.969
2.8353
2.0
4.000
8.000
1.4142
1.2599
6.283
3.1416
2.1
4.410
9.261
1.4491
1.2806
6.597
3.4636
2.2
4.840
10.648
1.4832
1.3006
6.912
3.8013
2.3
5.290
12.167
1.5166
1.3200
7.226
4.1548
2.4
5.760
18.824
1.5492
1.3389
7.540
4.5239
2.5
6.250
15.625
1.5811
1.3572
7.854
4.9087
2.6
6.760
17.576
1.6125
1.3751
8.168
5.3093
2.7
7.290
19.683
1.6432
1.3925
8.482
5.7256
2.8
7.840
21.952
1.6733
1.4095
8.797
6.1575
2.9
8.410
24.389
1.7029
1.4260
9.111
6.6052
3.0
9.000
27.000
1.7321
1.4422
9.425
7.0688
3.1
9.610
29.791
1 . 7607
1.4581
9.739
7.5477
3.2
10.240
32.768
1.7889
1.47;J6
10.053
8.0J25
3.3
10.890
35.937
1.8166
1.4888
10.367
8.5530
3.4
11.560
39.304
1.8439
1.5037
10.681
9.0792
3.5
12.250
42.875
1.8708
1.5183
10.996
9.6211
3.6
12.960
46.6J6
1.8974
1.5326
11.310
10.179
3.7
13.690
50.653
1.9235
1.5467
11.624
10.752
3.8
14.440
54.872
1.9494
1.5605
11.9.'«
11.341
3.9
15.210
59.319
1.9748
1.5741
12.252
11.946
4.0
16.000
64.000
2.0000
1.5870
12.566
12.566
4.1
10.810
68.921
2.0249
1.6005
12.881
13.20.?
4.2
17.640
74.088
2.0494
1.6134
13.195
13.854
4.3
18.490
79.. '507
2.0736
1.6261
13.559
14.522
4.4
19.360
85.184
2.0976
1.6386
13.823
15.205
328
Olrnle
No,
Square
Oube
Sq.
root
Oube
root
Diam.
Oircumf
Area
4.5
20.250
91.125
2.1213
1.6510
14.137
15.904
4.6
21.160
97.336
2.1448
1.6631
14.451
16.619
4.7
22.090
103.823
2.1680
1.6751
14.765
17.349
4.8
23.040
110.592
2.1909
1.6869
15.080
18.096
4.9
24.010
117.649
2.2136
1.6985
15.394
18.859
5.0
25.000
125.000
2.2361
1.7100
15.708
19.635
5.1
26.010
132.651
2.2583
1.7213
16.022
20.428
5.2
27.040
140.608
2.2804
1.7325
16.336
21.237
5.3
28.090
148.877
2.3022
1.7435
16.650
22.062
5.4
29.160
157.464
2.3238
1.7544
16.965
22.902
5.5
30.250
166.375
2.3452
1.7652
17.279
23.758
5.6
31.360
175.616
2.3664
1.7760
17.593
24.630
5.7
32.490
185.193
2.3875
1.7863
17.907
25.518
5.8
33.640
195.112
2.4083
1.7967
18.221
26.421
5.9
34.810
205.379
2.4290
1.8070
18.536
27.340
6.0
36.000
216.000
2.4495
1.8171
18.850
28.274
6.1
37.210
226.981
2.4698
1.8272
19.164
29.225
6.2
38.440
238.328
2.4900
1.8371
19.478
30.191
6.3
39.690
250.047
2.5100
1.8469
19.792
31.173
6.4
40.960
262.144
2.5298
1.8566
20.106
32.170
6.5
42.250
274.625
2.5495
1.8663
20.420
33.183
6.6
43.560
287.496
2.5691
1.8758
20.735
34.212
6.7
44.890
300.763
2.5884
1.8852
21.049
35.257
6.8
46.240
314.432
2.6077
1.8945
21.363
36.317
6.9
47.610
328.509
2.6268
1.9038
21.677
37.393
7.0
49.000
343.000
2.6458
1.9129
21.991
38.485
7.1
50.410
357.911
2.6646
1.9220
22.305
39.592
7.2
51.840
373.248
2.6833
1.9310
22.619
40.715
7.3
53.290
389.017
2.7019
1.9399
22.934
41.854
7.4
54.760
405.224
2.7203
1.9487
23.248
43.008
7.5
56.250
421.875
2.7386
1.9574
23.562
44.179
7.6
57.760
438.976
2.7568
1.9661
23.876
45.365
7.7
59.290
456.5.33
2.7749
1.9747
24.190
46.566
7.8
60.840
474.552
2.7929
1.9832
24.504
47.784
7.9
62.410
493.039
2.8107
1.9916
24.819
49.017
8.0
64.000
512.000
2.8284
2.0000
25.133
50.266
8.1
65.610
531.441
2.8461
2.0083
25.447
51.530
8.2
67.240
551.468
2.8636
2.0165
25.761
52.810
8.3
68.890
571.787
2.8810
2.0247
26.075
54.106
8.4
70.560
592.704
2.8983
2.0328
26.389
65.418
8.5
72.250
614.125
2.9155
2.0408
26.704
56.745
8.6
73.960
636.056
2.9326
2.0488
27.018
58.088
8.7
75.690
658.503
2.9496
2.0567
27.332
59.447
8.8
77.440
681.473
2.9665
2.0646
27.646
60.821
8.9
79.210
704.969
2.9833
2.0724
27.960
62.211
329
Circle
No.
Square
Cube
Sq.
root
Cube
root
Diam.
Oircumf
Area
9.0
81.000
729.000
3.0000
2.0801
28.274
63.617
9.1
82.810
753.571
3.0166
2.0678
28.588
65.039
9.2
84.640
778.688
3.0332
2.0954
28.903
66.476
9.3
86.490
804.357
3.0496
2.1029
29.217
67.929
9.4
88.360
830.584
3.0659
2.1105
29.531
69.398
9.5
90.250
857.375
3.0822
2.1179
29.845
70.882
9.6
92.160
884.736
3.0984
2.1253
30.159
72.382
9.7
94.090
912.673
3.1145
2.1327
30.473
73.898
9.8
96.040
941.192
3.1305
2.1400
30.788
75.430
9.9
98.010
970.299
3.1464
2.1472
31.102
76.977
10
100.000
1000.000
3.1623
2.1544
31.416
78.540
11
121.000
1331.000
3.3166
2.2239
34.558
95.033
12
144.000
1728.000
3.4641
2.2894
37.699
113.097
13
169.000
2197.000
3.6056
2.3513
40.841
132.732
14
196.000
2744.000
3.7417
2.4101
43.982
153.938 .
15
225.000
3375.000
3.8730
2.4662
47.124
176.715
16
256.000
4096,000
4.0000
2.5198
50.265
201.062
17
289.000
4913.000
4.1231
2.5713
53.407
226.980
18
324.000
5832.000
4.2426
2.6207
56.549
254.469
19
361.000
6859.000
4.3589
2.6684
59.690
283.529
20
400.000
8000.000
4.4721
2.7144
62.832
314.159
21
441.000
9261.000
4.5826
2.7589
65.793
346.361
22
484.000
10648.000
4.6904
2.8021
69.115
380.133
23
529.000
12167.000
4.7958
2.8439
72.257
415.476
24
576.000
13824.000
4.8990
2.8845
75.398
452.389
25
625.000
15625.000
5.0000
2.9241
78.540
490.874
26
676.000
17576.000
5.0990
2.9625
81.681
580.929
27
729.000
19683.000
5.1962
3.0000
84.823
572 . 555
28
784.000
21952.000
5.2915
3.0366
87.965
615.752
29
841.000
24389.000
5.3852
3.0723
91.106
660.520
30
900.000
27000.000
5.477ti
3.1072
94.248
706.858
31
961.000
29791.000
5.5678
3.1414
97.389
754.768
32
1024.000
32768.000
5.6569
3.1748
100.531
804.248
33
1089.000
35937.000
5.7446
3.2075
103.673
851.299
34
1156.000
39304.000
5.8310
3.2396
106.841
907.920
35
1225.000
42875.000
5.9161
3.2710
109.956
962.113
36
1296.000
46656.000
6.0000
3.3019
113.097
1017.88
37
1369.000
50653.000
6.0827
3.3.3-22
116.239
1075.21
38
1444.000
54872.000
6.1644
3.3620
119.381
1134.11
39
1521.000
59319.000
6.2450
3.3912
122.522
1194.59
40
1600.000
64000.000
6.3246
3.4200
125.66
1256.64
41
1681.000
68921.000
6.4031
3.4482
128.81
1320.25
42
1764.000
74088.000
6.4807
3.4760
131.95
1385.44
43
1849.000
79507.000
6.5574
3.5034
135.09
1452.20
44
1936.000
85184.000
6.6333
3.5303
138.23
1520.53
330
No.
Diam.
Square
Cube
Sq.
root
Cube
root
Circle
Circumf
Area
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
2025.000
2116.000
2209.000
2304.000
2401.000
2500.000
2601.000
2704.000
2809.000
2916.000
3025.000
3136.000
3249.000
3364.000
3481.000
3600.000
3721.000
3844.000
3969.000
4096.000
4225.000
4356.000
4489.000
4624.000
4761.000
4900.000
5041.000
5184.000
5329.000
5476.000
5625.000
5776.000
5929.000
6084.000
6241.000
6400.000
6561.000
6724.000
6889.000
7056.000
7225.000
7396.000
7569.000
7744.000
7921.000
91125.000
97336.000
103823.000
110592.000
117649.000
125000.000
132651.000
140608.000
148877.000
157464.000
166375.000
175616.000
185193.000
195112.000
205379.000
216000.000
226981.000
238328.000
250047.000
262144.000
274625.000
287496.000
300763.000
314432.000
328509.000
343000.000
357911.000
373248.000
389017.000
405224.000
421875.000
438976.000
456533.000
474552.000
493039.000
512000.000
531441.000
551368.000
571787.000
592704.000
614125.000
636056.000
658503.000
681472.000
704969.000
6.7082
3.5569
6.7823
3.5830
6.8557
3.6088
6.9282
3.6342
7.0000
3.6593
7.0711
3.6840
7.1414
3.7084
7.2111
3.7325
7.2801
3.7563
7.3485
3.7798
7.4162
3.8030
7.4833
3.8259
7.5498
3.8485
7. '6158
3.8709
7.6811
3.8930
7.7460
3.9149
7.8102
3.9365
7.8740
3.9579
7.9373
3.9791
8.0000
4.0000
8.0623
4.0207
8.1240
4.0412
8.1854
4.0615
8.2462
4.0617
8.3066
4.1016
8.3666
4.1213
8.4261
4.1408
8.4853
4.1602
8.5440
4.1793
8.6023
4.1983
8.6603
4.2172
8.7178
4.2358
8.7750
4.2543
8.8.318
4.2727
8.8882
4.2908
8.9443
4.3089
9.0000
4.3267
9.0554
4.3445
9.1104
4.3621
9.1652
4.3795
9.2195
4.S9C,
9.2736
4.4140
9.3274
4.4310
9.3808
4.4480
9.4340
4.4647
141.37
144.51
147.65
150.80
153.94
157.08
160.22
163.. 36
166.50
169.65
172.79
175.93
179.07
182.21
185.35
188.50
191.64
194.78
197.92
201.06
204.20
207.34
210.49
213.63
216.77
219.91
223.05
226.19
229.34
232.48
235.62
238.76
241.90
245.04
248.19
251.33
254.47
257.61
260.75
263.89
267.04
270.18
273.32
276.46
279.60
1590.43
1661.90
1734.94
1809.56
1885.74
1963.50
2042.82
2123.72
2206.18
2290.22
2375.83
2463.01
2551.76
2642.08
2733.97
2827.43
2922.47
3019.07
3117.25
3216.99
3318.31
3421.19
3525.65
3631.68
3739.28
3848.45
3959.19
4071.50
4185.39
4300.84
4417.86
4536.46
4656.63
4778.36
4901.67
5026.55
5153.00
5281.02
5410.61
5541.77
5674.50
5808.80
5944.68
6082.12
6221.14
331
No.
Square
Cube
Sq.
root
Cube
root
Circle
Diam.
Oircumf
Area
90
8100.000
729000.000
9.4868
4.4814
282.74
6361.73
91
8281.000
753571.000
9.5394
4.4979
285.88
6503.88
92
8464.000
778688.000
9.5917
4.5144
289.03
6647.61
93
8649.000
804357.000
9.6437
4.5307
292.17
6792.91
94
8836.000
830584,000
9.6954
4.5468
295.81
6939.78
95
9025.000
857375.000
9.7468
4.5629
298.45
7088.22
96
9216.000
884736.000
9.7980
4.5789
301.59
7238.23
97
9409.000
912673.000
9.8489
4.5947
304.73
7389.81
98
9604.000
941 192. (KX)
9.8995
4.6104
307.88
7542.96
99
9801.000
970299.000
9.9499
4.6261
311.02
7697.69
100
10000.000
1000000.000
10.0000
4.6416
314.16
7853.98
105
11025.000
1157625.000
10.2470
4.7177
329.87
865J.01
110
12100.000
1331000.000
10.4881
4.7914
345.58
9503.32
115
13225.000
1520875.000
10.7238
4.8629
361.28
10386.89
120
14400.000
1728000.000
10.9545
4.9324
376.99
11309.73
125
15625.000
1953125. OOP
11.1803
5.0000
392.70
12271.85
130
16900.000
2197000.000
11.4018
5.0658
408.41
13273.23
135
18225.000
2460375.000
11.6190
5.1299
424.12
14313.88
140
19600.000
2744000.000
11 .8322
5.1925
439.82
15393.80
145
21025.000
3048625.000
12,0416
5,2536
455.53
16513.00
150
22500.000
3375000.000
12.2474
5.3133
471.24
17671.46
155
24025.000
3723875.000
12.4499
5.3717
486.95
18869.19
160
2:)600.000
4096000.000
12.6491
5.4288
502.65
20106.19
165
27225.000
4492125.000
12.8452
5.4848
518.36
21382.46
170
28900.000
4913000.000
13.0384
5.5397
534.07
22698.01
175
30625.000
5359375.000
13.2288
5.5934
549.78
24052.82
180
32400.000
58:52000.000
13.4164
5.6462
565.49
25446. 9^
185
34225.000
6331625.000
13.6015
5.6980
581.19
26880.25
190
36100.000
6859000.000
13.7840
5.7489
596.90
28352.87
195
38025.000
7414875.000
13.9642
5.7989
612.61
29864.77
200
40000.000
8000000.000
14.1421
5.8480
628.32
31415.93
205
42025.000
8615125.000
14 3178
5.8964
644.03
3.3006..%
210
44100.000
9261000.000
14.4914
5.9439
659.73
34636.06
215
46225.000
9938375.000
14.6629
5.9907
675.44
36305.03
220
48400.000
10648000.000
14.8324
6.0368
691.15
38013.27
225
50625.000
11390625.000
15.0000
6.0822
706.86
39760.78
230
52iK)0.00O
12167000.000
15.1658
6.1269
722.57
41547.56
235
55225.000
12977875.000
15.3297
6.1710
738.27
43.373.61
240
57600.000
13824000.000
15.4919
6.2145
75:^.98
452;«.93
245
60025.000
14706125.000
15.6525
6.2573
769.69
47143.52
250
62500.000
1562.5000.000
15.8114
6.2996
785.40
49087.39
255
65025.000
16.581.375.000
15.9687
6.3413
801.11
511)70.52
260
67600.000
17576000.000
16.1245
6.;i825
816.81
53092.92
265
70225.000
18^)09625. 0(X)
16.2788
6.4232
832.52
55154.59
270
72900.000
19683000.000
16.4317
6.4633
848.23
57255.53-
?32
*
Circlft
No.
Square
Cube
■ Sq.
root
Cube
root
Diam.
Circuml 1
Area
275
75625.000
20796875.000
16.5831
6.5030
863.94
59395.74
280
78400.000
21952000.000
16.7332
6.5421
879.65
61575.22
285
81225.000
23149125.000
16.8819
0.5808
895.35
63793.97
290
84100.000
24389000.000
17.0294
6.6191
911.06
66051.99
295
87025.000
25672375.000
17.1756
6.6569
926.77
68349.28
300
90000.000
27000000.000
17.3205
6.6943
942.48
70685.83
305
93025.000
28372625.000
17.4642
6.7313
958.19
73061.66
310
96100.000
29791000.000
17.6068
6.7679
973.89
75476.76
315
99225.000
31255875.000
17.7482
6.8041
989.60
77931.13
320
102400.000
32768000.000
17.8885
6.8399
1005.31
80424.77
325
105625.000
34328125.000
18.0278
6.8753
1021.02
82957.68
330
108900.000
35937000.000
18.1659
6.9104
1036.73
85529.86
335
112225.000
37595375.000
18.3030
6.9451
1052.43
88141.31
340
115600.000
39304000.000
18.4391
6.9795
1068.14
90792.03
345
119025.000
41063625.000
18.5742
7.0136
1083.85
93482.02
350
122500.000
42875000.000
18.7083
7.0473
1099.56
96211.28
355
126025.000
44738875.000
18.8414
7.0807
1115.27
98979.80
360
129600.000
46656000.000
18.9737
7.1138
1130.97
101787.60
365
133225,000
48627125.000
19.1050
7.1466
1146.68
104634.67
370
136900.000
50653000.000
19.2354
7.1791
1162.39
107521.01
375
140625.000
52734375.000
19.3649
7.2112
1178.10
110446.62
380
144400.000
54872000.000
19.4936
7.2432
1193.81
113411.49
385
148225.000
57066625.000
19.6214
7.2748
1209.51
116415.64
390
152100.000
59319000.000
19.7484
7.3061
1225.22
119459.06
395
156025. 000
61629875.000
19.8746
7.3372
1240.93
122541.75
400
160000.000
64000000.000
20.0000
7.3681
1256.64
125663.71
405
164025.000
66430125.000
20.1246
7.3986
1272.35
128824.93
410
168100.000
68921000.000
20.2485
7.4290
1288.05
132025.43
415
172225.000
71473375.000
20.3715
7.4590
1303.76
135265.20
420
176400.000
74088000.000
20.4939
7.4889
1319.47
138544.24
425
180625.000
76765625.000
20.6155
7.5185
1335.18
141862.54
430
184900.000
79507000.000
20.7364
7.5478
1350.88
145220.12
435
189225.000
82312875.000
20.8567
7.5770
1366.59
148616.97
440
193600.000
85184000.000
20.9762
7.6059
1382.30
152053.08
445
198025.000
88121125.000
21.0950
7.6346
1398.01
155528.47
450
202500.000
91125000.000
21.2132
7.6631
1413.72
159043.13
455
207025.000
94196375.000
21.3307
7.6914
1429.42
162597.05
460
211600.000
97336000.000
21.4476
7.7194
1445.13
166190.25
465
216225.000
100544625.000
21.5639
7.7473
1460.84
169822.72
470
220900.000
103823000.000
21.6795
7.7750
1476.55
173494.45
475
225625.000
107171875.000
21.7945
7.8025
1492.26
177205.46
480
230400.000
110592000.000
21.9089
7.8297
1507.96
180955.74
485
235225.000
114084125.000
22.0227
7.8568
1523.67
184745.28
490
240100.000
117649000.000
22.1359
7.8837
1539.38
188574.10
495
245025.000
121287375.000
22.2486
7.9105
1555.09
192442.18
500
250000.000
125000000.000
22.3607
7.9370
1570.80
196349.54
333
TABLE 2.
Trigronometrle Fnnctlons.
Angle,
degrees
Sine
Tangent
Angle,
degrees
Sine
Tangent
0.0
0.00000
0.00000
90.0
47.5
0.73728
1.0913
42.5
2.5
0. 04302
0.04362
87.5
50.0
0.76604
1.1917
40.0
5.0
0.0S716
0.08749
85.0
52.5
0.79335
1.3032
37.5
7.5
0.13053
0.13165
82.5
55.0
0.81915
1.4281
35.0
10.0
0.17365
0.17633
80.0
57.5
0.84339
1.5697
32.5
12.5
0.21644
0.22169
77.5
60.0
0.86603
1.7321
30.0
15.0
0.25882
0.26795
75.0
62.5
0.88701
1.9210
27.5
17.5
0.30071
0.31530
72.5
65.0
0.90631
2.1445
25.0
20.0
0.34202
0.36397
70.0
67.5
0.92388
2.4142
22.5
22.5
0.38263
0.41421
67.5
70.0
0.93969
2.7474
20.0
• 25.0
0.42262
0.46631
6o.O
72.5
0.95372
3.1716
17.5
27.5
0.46175
0.52057
62.5
75.0
0.96593
3.7321
15.0
30.0
0.50000
0.57735
60.0
77.5
0.97630
4.5107
12.5
32.5
0.53730
0.63707
57.5
80.0
0.9&481
5.6713
10.0
35.0
0.57358
0.70021
55.0
SS.5
0.99144
7.5958
7.5
37.5
0.60876
0.76733
52.5
85.0
0.99619
11.430
5.0
40.0
0.64279
0.83910
50.0
87.0
0.99863
19.081
3.0
42.5
0.67559
0.91633
. 47.5
88.5
0.99966
38.188
1.5
45.0
0.70711
1.0000
45.0
90.0
1.0000
Infinite
0.0
Cosine
Cotan-
Angle,
Cosine
Cotan-
Angle,
gent
degrees
gent
degrees
TABLE 3.
Eqnlvalents of Compound I'nlts.
f 27.71 in. of water at 62" F.
I 2.0355 in. of mercury at 32" P.
1 lb. per sq. In. =-! 2.M16 in. of mercury at 62° F.
2.3090 ft. of water at 62" F.
L
1784.
ft. of air at 32° F.
1 oz. per sq. in.
1 in. of water at 62
— 10.1276 in. of mercury at 62° F.
(0.
i2° F. =-^5.
lo.
732 in. of water at 62° F.
0.03609 lb. or .5574 oz. per s. in.
196 lbs, per sq. ft.
0736 in. of mercury at 62° F.
1 in. of water at 32° F. =j''-2021 lbs. per sq. ft.
/ 0.036125 lb. per sq. in.
( 0.491 lb. or 7.86 oz. per sq. In.
= < 1.132 ft. of Mater at 62° F.
( 13.58 in. of water at 62° F.
1 In. of mercury at 62° F.
1 ft. of air nt .32° F = j 0.0005606 lb. per sq. in.
I 0.015534 in. of water at 62° P.
334
TABLE 4.
Properties of Saturated Steam.*
Absolute
Tempera-
Heat
Heat of the
Total
press're lbs.
ture
of the
vaporiza-
heat
per sq. In.
deg. F.
liquid
tion
above 32®
1
101.84
69.8
1034.7
1104.5
2
126.15
94.2
1021.9
1116.1
3
141.52
109.6
1012.2
1121.8
4
153.00
121.0
1005.5
1126.5
5
162.26
130.3
1000.0
1130.3
6
170.07
138.1
995.5
1133.6
7
176.84
144.9
991.4
1136.3
8
182.86
150.9
987.8
1138.7
9
188.27
156.4
984.5
1140.9
10
193.21
161.3
981.4
1142.7
11
197.74
165.9
978.6
1144.5
12
201.95
170.1
976.0
1146.1
13
205.87
174.1
973.6
1147.7
14
209.55
177.8
971.2
1149.0
14.7
212.00
180.3
969.7
1150.0
is
213.03
181.3
969.1
1150.4
16
216.31
184.6
967.0
1151.6
17
219.43
187.8
965.0
1152.8
18
222.40
190.8
963.1
1153.9
19
225.24
193.7
961.2
1154.9
20
227.95
196.4
959.4
1155.8
21
230.56
199.1
957.7
1156,8
22
233.07
201.6
956.0
1157.6
23
235.50
204.1
954.4
1158.5
24
237.82
206.4
952.9
1159.3
25
240.07
208.7
951.4
1160.1
26
242.26
210.9
949.9
1160.8
27
244.36
213.0
948.5
1161.5
28
246.41
215.1
947.1
1162.2
29
248.41
217.2
945.8
1163.0
SO
250.34
219.1
944.4
1163.5
31
252.22
221.0
943.1
1164.1
32
254.05
222.9
941.8
1164.7
S3
255.84
224.7
940.6
1165.3
34
257.59
226.5
939.4
1165.9
35
259.29
228.2
938.2
1166.4
36
260.96
229.9
937.1
1167.0
37
262.58
231.6
935.9
1167.5
38
264.17
233.2
934.8
1168.0
39
265.73
234.8
933.7
1168.5
40
267.26
236.4
932.6
1169.0
41
268.76
237.9
931.6
1169.5
42
270.23
239.4
930.6
1170.0
43
271.66
240.8
929.5
1170.3
44
273.07
242.3
928.5
1170.8
♦Condensed from Peabody's Steam Tables. 1911 Edition.
335
Absolute
pressure lbs.
per sq. In.
Tempera-
ture
deg. F.
Heat
of the
liquid
Heat of the
vaporiza-
tion
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
274.46
275.82
277.16
278.47
279.76
281.03
282.28
283.52
284.74
285.93
287.09
288.25
289.40
290.53
291.64
292.74
293.82
294.88
295.93
296.97
298.00
299.02
300.02
301.01
301,99
302.96
303.91
304.86
305.79
306.72
307.64
308.54
309.44
310.33
311.21
312.08
312.94
313.79
314.63
315.47
316.30
317.12
317.93
318.73
319.53
.320.32
321.10
.321.88
.322.65
323.41
Total
heat
nbove82°
243.7
245.1
246.4
247.8
249.1
250.4
251.7
253.0
254.2
255.4
256.6
257.8
259.0
260.1
261.3
262.4
263.5
264.6
265.7
. 266.7
267.8
268.8
269.8
270.9
271.9
272.9
273.8
274.8
275.8
276.7
277.7
278.6
279.5
280.4
281.3
282.2
283.1
283.9
284.8
285.7
286.5
287.4
288.2
289.0
289.9
290.7
291.5
292.3
293.1
293.9
927.5
926.6
925.6
924.7
923.8
922.8
921.9
921.0
920.1
919.3
918.4
917.6
916.7
915.9
915.1
914.3
913.5
912.7
911.9
911.1
910.4
909.6
908.9
908.1
907.4
906.6
905.9
905.2
904.5
903.8
903.1
902.4
901.8
901.1
900.4
899.8
899.1
898.5
897.8
897.2
1171.2
1171.7
1172.0
1172.5
1172.9
1173.2
1173.6
1174.0
1174.3
1174.7
1175.0
1175.4
1175.7
1176.0
1176.4
1176.7
1177. C
1177.3
1177.6
1177.8
1178.2
1178.4
1178.7
1179.0
1179.3
1179.5
1179.7
1180.0
1180.3
1180.5
1180.8
1181.0
1181.3
1181.5
1181.7
1182.0
1182.2
1182.4
1182 6
1182.9
896.6
1183.1
895.9
1183.3
895.3
1183.5
8<)4.7
1183.7
894.1
1184.0
893.5
1184.2
892.9
1184.4
892.3
1184.6
891.7
1184.8
891.1
1185.0
336
Absolute
Tempera-
Heat
Heat of the
Total
press're lbs.
ture
of the
vaporiza-
heat
per sq. in.
deg. F.
liquid
tion
Above 32*
95
324.16
294.6
890.5
1185.1
96
324.91
295.4
889.9
1185.3
97
325.66
296.2
889.3
1185.5
98
326.40
296.9
888.7
1185,6
99
327.13
297,7
888,2
1185.9
100
327.86
298.5
887,6
1186.1
101
328.58
299,2
887.0
1186,2
102
329.30
299.9
886.5
1186.4
103
330.01
300.6
885.9
1186.5
101
330.72
301,4
885,3
1186,7
105
331.42
302.1
884.8
1186,9
106
332.11
302.8
884.3
1187.1
107
332.79
303.5
883.7
1187.2
108
333.48
304.2
883.2
1187.4
109
334.16
304,9
882.6
1187. 5
110
334.83
305,6
882.1
1187,7
111
335.50
306,3
881,6
1187,9
112
336.17
307.0
881,0
1188.0
113
336.83
307.7
880.5
1188.2
114
337.48
308,3
880.0
1188.3
115
338.14
309.0
879.5
1188.5
116
338.78
309.7
879,0
1188,7
117
339.42
310,3
878,5
1188,8
118
340.06
311.0
878.0
1189,0
119
340.69
311,7
877,4
1189.1
120
341.31
312.3
876,9
1189.2
121
341.94
312.9
876.4
1189,3
122
342.56
313.6
875.9
1189.5
123
343.18
314.2
875.4
1189.6
124
343.79
314,8
875.0
1189.8
125
344.39
315,5
874.5
1190,0
126
345.00
316.1
874,0
1190,1
127
345.60
316.7
873,5
1190.2
128
346.20
317.3
873.0
119C.3
129
346.79
317,9
872,6
1190,5
130
347.38
318.6
872.1
1190,7
131
347,96
319.2
871,6
1190,8
132
348.55
319.8
871,1
1190,9
133
349.13
320.4
870,7
1191,1
134
349.70
320.9
870.2
1191,1
135
350.27
321.5
869.8
1191.3
136
350.84
322,1
869.3
1191,4
137
351.41
822,7
868.8
1191.5
138
351,98
323,3
868,3
1191,6
139
352,54
323,9
867.9
1191,8
140
353.09
324.4
867.4
1191,8
141
353.65
325.0
867.0
1192,0
142
354.20
325,6
866.5
1192.1
143
354.75
326.2
866.1
1192.3
144
355.29
326.7
865.8
1192.3
337
TABLE 5.
Naperian Logarithms.
e = 2.7182818
Log e = 0.4342945 = M.
1.0
0.0000
4.1
1.4110
7.2 1
1.9741
1.1
0.0953
4.2
1.4351
7.3
1.9879
1.2
0.1823
4.3
1.4586
7.4
2.0015
1.3
0.2624
4.4
1.4816
7.5
2.0149
1.4
0.3365
4.5
1.5041
7.6
2.0281
1.5
0.4055
4.6
1.5261
7.7
^.0412
1.6
0.4700
4.7
1 .5476
7.8
2.0541
1.7
0.5306
4.8
1.5686
7.9
2.0669
1.8
0.5878
4.9
1.5S92
8.0
2.0794
1.9
0.6419
6.0
1.6094
8.1
2.0919
2.0
0.6931
6.1
1.6292
8.2
2.1041
2.1
0.7419
5.2
1.6487
8.3
2.1163
2.2
0.7885
5.3
1.6677
8.4
2.1282
2.3
0.8329
5.4
1.6864
8.5
2.1401
2.4
0.8755
5.5
1 .7047
8.6
2.1518
2.5
0.9163
5.6
1.7228
8.7
2.163.'*
1.6
0.9555
5.7
1.7405
8.8
2.1748
2.7
0.9933
5.8
1.7579
8.9
2.1861
2.8
1.0296
6.9
1.7750
9.0
2.1972
2.9
1.0647
6.0
1.7918
9.1
2.2083
3.0
1.0966
6.L
1.8083
9.2
2.2192
3.1
1.1312
6.2
1 .8245
9.3
2.2300
S.2
1.1632
6.3
1.8405
9.4
2.2407
8.3
1.1939
6.4
1.8563
9.5
2.2513
6.4
1.2238
6.5
1.8718
9.6
2.2618
8.5
1.2528
6.6
1.8871
9.7
2.2721
3.6
1.2809
6.7
1.9021
9.8
2.2824
3.7
1.3083
6.8
1.9169
9.9
2.2926
3.8
1.3350
6.9
1.9315
10.0
2.3026
3.9
1.3610
7.0
1.9459
4.0
1.3863
7.1
1.9601
TABLE 6.
Water Conversion Factors.*
U. S. gallons X
8.33
= pounds.
U. S. gallons X
0.13368
= cubic feet.
U. S. gallons X 231.00000
= cubic Inches.
U. S. gallons X
8.78
= liters.
Cubic Inches of water (89.1°) X
0.036024
= pounds.
Cubic inches of water (39.1°) X
0.004329
= U. S. gallons.
Cubic inches of water (»).1°} X
0.576:384
= ounces.
Cubic feet of water (39.1°) X
62.425
= pounds.
Cubic feet of water (39.1°) X
7.48
= U. S. gallons.
Cubic feet of water (39.1°) X
0.028
= tons.
Pounds of water X
27.72
= cubic inches.
Pounds of water X
0.01602
= cubic feet.
Pounds of water X
0.12
= U. S. gallons.
'American Machinist Hand Book.
338
TABLE 7.
Volnme and Weisbt of Dry Air at Different Temperatnrea.*
Under a constant atmospheric pressure of 29.92 inches of
mercury, the volume at 32° F. being 1. ^
Temp,
deg. F.
Volume
Weight
per cu. ft.
Temp,
deg. F.
Volume
Weight
per cu. ft.
.935
.0864
50O
1.954
.0413
12
.960
.0842
552
2.056
.0385
23
.980
.0824
60O
2.150
.0376
32
1.000
.0807
650
2.2S0
.0357
42
1.020
.0791
700
2.362
.0338
52
1.041
.077S
750
2.465
.0328
62
1.061
.0761
800
2.566
.0315
72
1.082
.0747
850
2.668
.0303
82
1.102
.0733
900
2.770
.0292
82
1.122
.0720
950
2.871
.0281
102
1.143
.0707
lOOO
2.974
.0268
112
1.163
.0694
llOO
3.177
.0254
122
1.184
.0682
1200
3.381
.0239
132
1.204
.0671
1300
3.584
.0225
142
1.224
.0659
1400
3.788
.0213
152
1.245
.0649
1500
3.993
.0202
162
1.265
.0638
1600
4.196
.0192
172
1.285
.0628
1700
4.402
.0183
182
1.306
.0618
1800
4.605
.0175
192
1.326
.0609
1900
4.808
.0168
202
1.347
.0600
2000
5.012
.0161
212
1.367
.0591
2100
5.217
.0155
2S0
1.404
.0575
220O
6.420
.0149
250
1.444
.0559
230O
5.625
.0142
275
1.495
.0540
2400
5.827
.0138
300
1.546
.0522
2500
6.032
.0133
325
1.597
.0506
2600
6.236
.0130
350
1.648
.0490
270O
6.440
.0125
875
1.689
.0477
2800
6.644
.0121
400
1.750
.0461
2900
6.847
.0118
450
1.852
.0436
3000
7.051
.0114
"Suplee's M. E. Reference Book.
239
TABLE 8.
Welgrht of Pure Water per Cubic Foot at Varlons
Temperatures.*
Temp.
Weight
B. t. u.
Temp.
Weight
B. t. u.
deg.
lbs. per
per pound
deg.
lbs. per
per pound
P.
cu. ft.
above 32
P.
cu. ft.
above 32
32
62.42
0.00
77
62.26
45.04
33
62.42
1.01
78
62.25
46.04
34
62.42
2.02
79
62.24
47.04
35
62.42
3.02
80
62.23
48.03
36
62.42
4.03
81
62.22
49.03
37
62.42
5.04
82
62.21
50.03
38
62.42
6.04
83
62.20
51.02
39
62.42
7.05
84
62.19
52.02
40
62.42
8.05
85
62.18
53.02
41
62.42
9.05
86
62.17
54.01
42
62.42
10.06
87
62.16
55.01
43
62.42
11.06
88
62.15
56.01
44
62.42
12.06
89
62.14
57.00
45
62.42
13.07
90
62.13
58.00
46
62.42
14.07.
91
62.12
59.00
47
62.42
15.07
92
62.11
60.00
4S
62.41
16.07
93
62.10
60.99
49
62.41
17.08
94
62.09
61.99
60
62.41
18.08
95
62.08
62.99
51
62.41
19.08
96
62.07
63.98
62
62.40
20.08
97
62.06
64.98
53
62.40
21.08
98
62.05
65.98
54
62.40
22.08
99
62.03
66.97
55
62.39
23.08
100
62.02
67.97
56
62.39
24.08
101
62.01
68.97
57
62.39
25.08
102
62.00
69.96
58
62.38
26.08
103
61.99
70.96
59
62.38
27.06
104
61.97
71.96
60
62.37
28.08
105
61.96
72.95
61
62.37
29.08
106
61.95
73.95
62
62.36
30.08
107
61.93
74.95
63
62.36
31.07
108
61.92
75.95
64
62.35
32.07
109
61.91
76.94
65
62.34
33.07
110
61.89
77.94
66
62.34
34.07
111
61.88
78.94
67
62.33
35.07
112
61.86
79.93
68
62.33
36.07
113
61.85
80.93
69
62.32
37.06
114
61.83
81.93
70
62.31
38.06
115
61.82
82.92
71
62.31
39.06
116
61.80
83.92
72
62.30
40.05
117
61.78
84.92
73
62.29
41.05
118
61.77
85.92
74
62.28
42.05
119
61.75
86.91
75
62.28
43.05
120
61.74
87.91
76
62.27
44.04
121
61.72
88.91
•Kent's M. E. Pocket-Book. 8th Edition.
340
Temp.
Weight
B. t. u.
Temp.
Weight
B. t. u.
deg.
lbs. per
per pound
deg.
lbs. per
per pound
P.
cu. ft.
above 32
F.
cu. ft.
above 32
122
61.70
89.91
167
60.83
134.86
123
61.68
90.90
168
60.81
135.86
124
61.67
91.90
169
60.79
136.86
125
61.65
92.90
170
60.77
137.87
126
61.63
93.90
171
60.75
138.87
127
61.61
94.89
172
60.73
139.87
128
61.60
95.89
173
60.70
140.87
129
61.58
96.89
174
60.68
141.87
130
61.56
97.89
175
60.66
142.87
131
61.54
98.89
176
60.64
143.87
132
61.52
99.88
177
60.62
144.88
133
61.51
100.88
178
60.59
145.88
134
61.49
101.88
179
60.57
146.88
135
61.47
102.88
180
60.55
147.88
136
61.45
103.88
181
60.53
148.88
137
61.43
104.87
182
60.50
149.89
138
61.41
105.87
183
60.48
150.89
139
61.39
106.87
184
60.46
151.89
140
61.37
107.87
185
60.44
152.89
141
61.36
108.87
186
60.41
153.89
142
61.34
109.87
187
60.39
154.90
143
61.32
110.87
188
60.37
155.90
144
61.30
111.87
189
60.34
156.90
145
61.28
112.86
190
60.32
157.91
146
61.26
113.86
191
60.29
158.91
147
61.24
114.86
192
60.27
159.91
148
61.22
115.86
193
60.25
160.91
149
61.20
116.86
194
60.22
161.92
150
61.18
117.86
195
60.20
162.92
151
61.16
118.86
196
60.17
163.92
152
61.14
119.86
197
60.15
164.93
153
61.12
120.86
198
60.12
165.93
154
61.10
121.86
199
60.10
166.94
155
61.08
122.86
200
60.07
167.94
156
61.06
. 123.86
201
60.05
168.94
157
61,04
124.86
202
60.02
169.95
158
61.02
125.86
203
60.00
170.95
159
61.00
126.86
204
59.97
171.96
160
60.98
127.86
205
59.95
172.96
161
60.96
128.86
206
59.92
173.97
162
60.94
129.86
207
59.89
174.97
163
60.92
130.86
208
59.87
175.98
164
60.90
131.86
209
59.84
176.98
165
60.87
132.86
210
59.82
177.99
166
60.85
133.86
211
59.79
178.99
212
59.76
180.
341
TABLE 9.
Boillni? Point of Water at DlfTerent Helgrhtn of Vacuum.
Heipht of
Height of
Temp.
mercury m
Temp.
mercury in
F.
vacuum tube
F.
vacuum tube
in inches
in inches
212.0
0.00
175.8
16.00
210.3
1.00
172.6
17.00
208.5
2.00
169.0
18.00
206.8
3.00
165.3
19.00
204.8
4.00
161.2
20.00
202.9
5.00
156.7
21.00
200.9
6,00
151.9
22.00
199.0
7.00
146.5
23.00
196.7
8.00
140.3
24.00
194.5
9.00
133.3
25.00
192.2
10.00
124.9
26.00
189.7
11.00
114.4
27.00
187.3
12.00
108.4
28.00
184.6
13.00
102.0
29.00
181.3
14.00
98.0
29.92
178.9
15.00
TABLE 10.
Welgrht of Water with Air per Cubic Foot at Different
Temperatures and at Saturation.
^
|5h
Ph
1^'
^
f^
6.
a
a
Eh
4^
be .9
'S ca
^ So
d
a
d
a
4J
j3 to
tuD.a
^ Si
d
a
O)
Eh
4J
be .9
'S 03
d
a
Eh
4J
.5? .9
u S3
^ Si
—20
0.i66
2
0.529
24
1.483
46
3.539
68
7.480
90
14.790
—19
0.174
3
0.554
25
1.551
47
3.667
69
7.726
91
15.234
—18
0.184
4
0.582
26
1.623
48
3.800
70
7.980
92
15.689
—17
0.196
5
0.610
27
1.697
49
3.936
71
8.240
93
16.155
—16
0.207
6
0.639
28
1.773
50
4.076
72
8.508
94
16.634
—15
0.218
7
0.671
29
1.853
51
4.222
73
8.782
95
17.124
—14
0.231
8
0.704
30
1.935
52
4.372
74
9.066
96
17.626
—13
0.243
9
0.7.39
31
2.022
53
4.526
75
9.356
97
18.142
—12
0.257
10
0.776
32
2.113
54
4.685
76
9.655
98
18.671
—11
0.270
11
0.816
33
2.194
55
4.849
77
9.962
99
19.212
-10
0.285
12
0.856
34
2.279
56
5.016
78
10.277
100
19.766
— 9
0.300
13
0.898
35
2.366
57
5.191
79
10.601
101
2().3;15
— 8
0.316
14
0.941
36
2.457
58
5.370
80
10.934
102
21.017
— 7
0.332
15
0.986
37
2.550
59
5.5.')5
81
11.275
103
21.514
— 6
0.350
16
1.032
38
2.646
60
5.745
82
11.626
104
22.125
— 5
0.370
17
1.080
39
2.746
61
5.941
83
11.987
105
22.750
— 4
0.389
18
1.128
40
2.849
62
6.142
84
12.356
106
23.3i)2
— 3
0.411
19
1.181
41
2.955
63
6.349
85
12.736
107
24.048
— 2
0.434
20
1.235
42
3.064
64
6.563
86
13.127
108
24.720
— 1
0.457
21
1.294
43
3.177
65
6.782
87
13.526
109
25.408
0.481
22
1.355
44
3.294
66
7.009
88
13.937
110
26.112
1
0.505
23
1.418
45
3.414
67
7.241
89
14.369
31:
sain^Bjaduia^ Jjv
ilO^OCOl^t^OOOOOiOSi
s ^
-c
s I
i-l T-H r-l (M (M <N C<l (>]
(M (M (N (M (M CO CO
( in Oi (M ■>* 1^ Oi r^ ■
) I— I T— I (M O-l c; 03 CO
• r-^ <^J \.M^ i^ U'J t^^ X"*
4 e<l (M (M CO CO CO CO
iooinOcot-0(M-^coooo
-^ -ngMtMe-jcococoeoco-^
(i:^C0t^(MiO0ii-i-*<O00O(Mi
i-(T-H(M(M(MCoeocoeoM<-^-
COOtDOlOOilMlOOOOCN-^lOt^OOOi
— li-H03<NC<lCOCOCO-^-!><-^M<T)<-»!H-»!t<
CDC001COOOIMlCl^O(M-<*l01--OiQr-l
I— ii-te<ie<icococo-'j<-^-^Tj<-^-^ttioio
(M O CD
<MC0C0COCO-^-t<-*-»J<-^lfil
^_^ S^_; 1—1 \t^ \.^ ^j' A'- ^j \,N| -^ S4^ l.^» WJ ^--' ?"n VJ
rHr-lfM<MCOCOCOCO-^-t<-*-»J<-^lfilOir5
CD ^ O CO ^H lO 00
oco^iooOi-i'*t^oiO<M-»*<mcpj
(MI>]COCOCO-^-^-^-^tOlOlO>niOI
i-lOCO'*<Oi-<*<00'-l-*l>Oii-HCO-*COJ:^QO
i-Hi— t(M(McocoTtiTti-rti-«^iOLOLOLnioin
CDCO(M00COt~i— l-<+lt~Gii— ICOlOt^l
rH iMOjcoeo-^-^-^-^mtomio '
l>CD-*iOLnO-*l:^Ocoint^ooOi
i-(c<icoco-*i-*-*iiomioiftiocD<
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OOOit^-^OJ-^OO^'^CDOOCM-rtilO
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rH(MCOCO-tl^lOtOlOCOCOCDCDCDCD
Si
ir- Oi O 00 -* O
CO O I
I O i-H (M CO •
1 CD!-- 1^ r^ J
• r-l:^ t^ i;~ J
) t^ 00 Ol O T— I I
• t- 1^ t- 00 00 I
1 CD 1^ r^ t^ J
IOCDCDCOCDX^1_ _ _ _ _ _ ,
O ooooSSooocooSSSoooooOoS
sain^Bjaduia:} jiy
OOCO'^-«tilO»r5COCOJ>l>0000030><
343
TABLE 12.
Properties of Air ^vlth MolHture under Pressure of One
Atmosphere.*
Oi O
"S
J:
Mixtures of air sa
with vapor
turated
S2
•a
4^
+J 1-1
c
a bo
•" OS
c to
a
«at--
Weight of cubic
^
^
"S
oj o o
foot of the
rs
c
■M
u
a
rzXi
^i
mixture.
O
03
•53
£
(V
■<->
x:
OS
D
■♦J
OS
t-i
<u
a
-t-> 0)
o o
(H U
O 0)
W O
*-' j;^ 05
4-1 H
P.
■M O
o a
■•J *^
x: u
s: —
is OJ
i-i
83 4-1
u
0)
■*-»
a
«M
o
o
"3 O
C
C >
.2^
<!£
to
^
^t^
03
cs a
^5
•S a
0-3
Kc3
— 3
S O X
OCes
5§
1
2
3
4
5
6
7
8
9
«
10
11 12
.935
.0864
0.044
29.877
.0863
.000079
.086379
.00092
1092.40
48.5
12
.960
.0842
0.074
29.849
.084(1
.00013(1
.084130
.00115
646.10
50.1
22
.980
.0824
0.118
29.803
.0821
.000202
.082302
.00245
406.40
51.1
32
1.000
.0807
0.181
29.740
.0802
.000304
.080504
.00379
263.81
3289'
52.0
42
1.020
.0791
.0267
29.654
.0784
.000440
.078840
.00561
178.18
2252.0
53.2
52
1.041
.0766
0.388
29.533
.0766
.000627
.077227
.00819
122.17
1595.0
54.0
60
1.057
.0764
0.522
29.399
.0751
.(XX)830
.075252
.01251
92.27
1227.0
55.0
62
1.061
.0761
0.556
29.365
.0747
.000881
.075581
.01179
84.79
1135.0
55.2
70
1.078
.0750
0.754
29.182
.0731
.001153
.073509
.01780
64.59
882.0
56.2
72
1.082
.0747
0.785
29.136
.0727
.001221
.073921
.01680
59.54
819.0
56.3
82
1.102
.0733
1.092
28.829
.0706
.001667
.072267
.02361
42.35
600.0
57.2
92
1.122
.0720
1.501
28.420
.0684
.002250
.070717
.03289
30.40
444.0
58.4
100
1.139
.0710
1.929
27.992
.0664
.002848
.069261
.04495
23.66
356.0
59.1
102
1.143
.0707
2.036
27.885
.0639
.002997
.068897
.04547
21.98
334.0
59.5
112
1.163
.0694
2.731
27.190
.0631
.003946
.067042
.06253
15.99
253.0
60.6
122
1.184
.0682
3.621
26.300
.0599
.005142
.065046
.08584
11.65
194.0
61.7
132
1.204
.0671
4.752
25.169
.0564
.006639
.063039
.11771
8.49
151.0
62.5
142
1.224
.0660
6.165
23.756
.0524
.008473
.060873
.16170
6.18
118.0
63.7
152
1.245
.0649
7.930
21.991
.0477
.010716
.058416
.22465
4.45
93.3
64.7
162
1.265
.0638
10,099
19.822
.0423
.013415
.055715
.31713
3.15
74.5
65.8
172
1.285
.0628
12.758
17.163
.0360
.016682
.052682
.46338
2.16
59.2
66.9
182
1.306
.0618
15.960
13.961
.0288
.020536
.049336
.71300
1.402
48.6
68.0
192
1.326
.0609
19.828
10.093
.0205
.025142
.045642
1.22643
.815
39.8
69.0
202
1.347
.0600
24.450
5.471
.0109
.030545
.041445
2.80230
In-
finite
.357
32.7
70.0
212
1.367
.0591
29.921
0.000
.0000
.036820
.036820
.000
27.1
71.1
'Carpenter's H. & V. B. and Sturtevant's Mech. Draft.
344
TABLE IS
De^v-Polnts of Air According to Its Hygrometrlc State.*
Relative
moisture
90%
80%
70%
60%
50%
c.
F.
0.
F.
C.
F.
C.
F.
C.
F.
0.
F.
32.0
— 1.5
29.3
— 3.0
26.6
— 4.9
23.2
— 6.5
20.3
— 9.2
15.4
2
35.6
0.9
33.6
— 0.9
30.4
— 2.5
27.5
— 4.8
23.4
— 7.1
19.2
4
39.2
2.4
36.3
0.9
33.6
— 0.9
30.4
— 2.9
26.8
— 5.3
22.5
6
42.8
4.5
40.1
2.9
37.2
0.9
33.6
-1.3
29.7
— 3.7
25.3
8
46.4
6.4
43.5
4.5
40.1
2.7
36.9
0.6
33.1
— 1.9
28.6
10
50.0
8.5
47.3
6.8
44.2
4.5
40.1
2.5
36.5
0.0
32.0
12
53.6
10.5
50.9
8.5
47.3
6.8
44.2
4.3
39.7
2.0
35.6
14
57.2
12.3
54.1
10.5
50.9
8.5
47.3
6.2
43.2
3.7
38.7
16
60.8
14.4
57.9
12.6
54.7
10.5
50.9
8.3
46.9
5.6
42.1
18
64.4
16.5
61.7
14.6
58.3
12.4
54.3
10.0
50.0
7.4
45.3
20
68.0
18.3
64.9
16.5
61.7
14.4
57.9
11.9
53.4
9.2
48.6
22
71.6
20.3
68.5
18.4
65.1
16.3
61.3
13.7
56.7
11.6
52.8
24
75.2
22.2
72.1
20.5
68.9
18.4
65.1
15.6
60.0
13.0
55.4
26
78.8
24.4
75.9
22.2
72.1
20.1
68.2
17.6
63.6
14.7
58.5
28
82.4
26.3
79.3
24.2
75.6
22.0
71.6
19.5
67.1
17.5
63.5
30
86.0
28.3
82.9
26.3
79.3
23.9
75.0
21.5
70.7
18.3
64.9
♦Bulletin 21, Int. Ass'n of Eefrig.
Psychrometric Charts Recent Tests.
In recent years a highly technical study of humidity
and its control has been made by Mr. Willis H. Carrier. Fig.
A shows, merely for the sake of comparison, how closely his
results checked the earlier
values obtained by the Gov-
ernment Weather Bureau. The
following charts. Figs. B and
C, summarize the results of
Mr. Carrier's experiments.
Fig. C is a part of Fig. B
drawn to a larger scale.
eo
700
eoS
c
50
30|
20
"^,
^^
.
^^
L
^^
55;^
""■
=::^
n a
s y
7
»=. ., =8
e
S 3
a
ORv Bulb
Fig. A.
As one illustration of the use of the chart, refer to Fig
C with air at 40 degrees and 40 per cent, humidity. If this
air be heated to 100 degrees without addition of moisture
it will be seen by interpolation that the humidity dTaps
to about 8 per cent. If the same be heated to 100 degrees
and enough moisture be added to keep the relative humid-
ity at 40 per cent., then the absolute humidity changes from
15 grains to 120 grains per pound of air. These figures
may be reduced to grains per cubic foot by dividing by the
volume per pound as given in the second column and will
be found to check closely with those given by Fig. 7 and
Table 9. Almost any 0(ther points relating to changes in
volume, humidity and contained heat may be easily worked
out by these curves. 045
348
i
?
3
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■^
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ryr'/ A
A 1 l\L >
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7
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■\ M
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i[
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^y\
;9
1
s^
"4
I
\
^
A
\
\
kj<
ojxti
/"=
«pi*
U,=J^
KOlX
jeoiB
S
•
^\\
\
1
p>itt(
W
jn/a
M'
^
-*>^
?/"
f^
4UOD
BpJi
VOM
r*^
P/»
w7
,1
I *^
4\
\
&
XflJC
VWI4
tmpOi
tax,
» sa
iopi
jitX
P9I
S5
U
1^
fl/fi
w^
.
c\
\
1
«2
o
5
VI ■»
a^
T
,1
:«
s
5^
d
•=
?
^
§
^
<e
M
^
»■*
vij
aOBt,
J
"9
1
s
s
^
^
■.Sj
Fl
.^.
B
^
«
§
'^
^
s
^
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o
>>
w
^ "y
bo
347
TABLE 14.
Fnel Value of American Coals.*
Coal
Name or locality
ARKANSAS.
Spadra, Johnson Co
Coal Hill, Johnson Co
Huntington Co.
Lignite
COLORADO.
Lignite
Lignite, slack
ILLINOIS.
Big' Muddy, Jackson Co
Colchester, Slack
Gillespie, Macoupin Co
Mercer Co,
INDIANA.
Block
Cannel
IOWA.
Good cheer
KENTUCKY.
Caking-
Cannel
Lignite
MISSOURI.
Bevler Mines
NEW MEXICO.
Coal
OHIO.
Briar Hill, Mahoning Co...
Hocking Valley
PENNSYLVANIA.
Anthracite
Anthracite, pea
Pittsburgh (average)
Youghiogheney
TEXAS.
Fort Worth —
Lignite
WEST VIRGINIA.
Pocahontas
New River
Fuel value per pound
of coal.
14,420
9,215
13,5G0
8,500
14,020
13,097
14,391
15,198
9,326
13,714
13,414
14,199
12,300
12,96-2
14.200
11,812
11,756
11,781
9,035
9.739
13,123
8,702
9.890
11,756
13,104
12,936
9,450
14,273
g
OicD ed
03.0
>^
ft)
- Pf^
03
-: si 0(>3
14.90
12.22
12.17
9.54
14.04
8.80
12.19
9.35
10.00
13.58
14.50
13.56
9.01
14.89
16.78
9.65
10.24
12.17
14.20
13.90
14.70
12.73
13.46
13.39
9.78
13.41
14.71
14.70
*Sturtevant's "Mechanical Draft.'
848
^
TABLE 15.
Capacities of Chimneys.*
10
12
15
18
Steam
Hot water
B. t. u. __.
Steam
Hot water
B. t. u. ...
Steam
Hot water
B. t. u. ...
Steam
Hot water
B. t. u. ...
Steam
Hot water
B. t. u. ...
Steam
Hot water
B. t. u. ...
Steam
Hot water
B. t. u. ...
Steam
Hot water
B. t. u. _..
Maximum sq. ft. of cast iron radiating
surface and B, t. u. for a flue of the
given diameter and height
bo
2
x:
J3
X3
X3
bo
bo
bo
bO
xi
fl
fl
Xi
4J
■w
■M
4i
■M
•M
•♦H
50
Oi
■*
lH
CO
■*
fO
00
XI
bo
146
243
36500
175
291
43750
204
340
51000
233
388
58250
262
437
65500
228
379
57000
273
455
68250
319
531
79750
364
607
91000
410
683
102500
327
544
81750
392
653
98000
457
762
114250
523
871
130750
568
980
147000
445
742
111250
534
890
133500
623
1038
155750
712
1187
178000
801
1335
200250
582
969
145500
698
1163
174500
814
1357
203500
930
1551
232500
1047
1745
261750
909
1514
227250
1090
1817
272500
1272
2120
318000
1454
2423
363500
1636
2726
409000
1537
2561
384250
1844
3073
461000
2151
3586
537750
2458
4098
614500
2766
4610
691500
2327
3878
581750
2792
4653
698000
3257
5429
814250
3722
6204
930500
4188
6980
1047000
291
485
72750
455
758
113750
653
1083
163250
890
1483
222500
1163
1938
290750
1817
3028
454250
3073
5122
768250
4653
7755
1163250
Radiation is calculated at 250 B. t. u. steam, 150 B. t. u. water.
*The Model Boiler Manual.
349
TABLE 16.
Equalization of Smoke FlueH — Commercial Slsea.*
Inside
Brick flue
Rectangular
Outside
diameter
not lined
lined flue
Iron
lined flue
well built
outside of tile
stack
6
8%x8%
8
7
8%x8%
7X7
9
8
81^x8%
8\4x8i^
10
9
81/^x13
8V^xl3
11
10
314x13
8V^xl3
12
13
13x13
13x13
14
15
13x17
13x18
17
18
17x21^
18x18
20
Round flue tile lining is listed by its inside measurement.
Rectangular lining by outside measurement.
TABLE 17.
Dimensions of Registers.*
Nominal
Effective
Size of
opening.
Inches
area cf
opening,
square
area of
opening,
square
Tin box size,
inches
Extreme
dimensions of
register face,
inches
inches
Inches
ex 10
60
40
61*8 X lOA
7U X IIU
9K X 11^
8x10
80
68
8H X 10^8
8x12
96
64
8H X 12y%
9K X 18K
8x15
120
80
8H X 15H
9K X 1611
lOJ^ X 18Ji
9x12
108
72
9li X 12]J
9x14
126
84
9iJ X 14 i
lOj/8 X 15;^
10x12
120
80
lOi, X 12 4
III8 X 1318
10x14
140
98
105, xl4ii
1118x1511
1118 X 17Ji
10x16
160
107
lOii X im
UH X 15^
12x15
180
120
14A X 17
12x19
228
152
12K X 195i
14A X 21
14x22
808
205
14^8 X 22^8
16^4 X 24^
15x25
875
250
15^8 X 25 X
17^ X 275^
16x20
820
218
UJi X 20%
18A X 22A
16x24
884
256
16^8 x24X
18.^ X 26A
22^ X 22H
20x20
400
267
20i8 x20 8
20i8 X 24 g
20x24
480
820
22^ X 26 >i
20x26
520
847
20} 8 X 26i8
22^ X 28^
21x29
609
408
21i8x2918
23H X31H
27x27
729
486
27i8x2718
2^m X 29H
27x88
1026
684
27}8x3818
29 H X 40-H
30x80
900
600
8015x8018
32 H X 82H
Dimensions of different makes of registers vary slightly,
are for Tuttle & Bailey manufacture,
•The Model Boiler Manual.
The aboy«
350
TABLE 18.
Capacities of Warm Air Furnaces of Ordinary Construction In
Cubic Feet of Space Heated.*
Divided space
Fire-pot
Undivided space
+10°
0°
-10°
Diam.
Area
+10°
0°
—IQP
12000
10000
8000
18 in.
1.8 sq. ft.
17000
14000
12000
14000
12000
10000
20 "
2.2
22000
17000
14000
17000
14000
12000
22 "
2.6
26000
22000
17000
22000
18000
14000
24 '•
3.1
80000
26000
22000
26000
22000
18000
26 "
3.7 '•
85000
80000
26000
80000
26000
22000
28 "
4.8
40000
35000
30000
35000
80000
26000
80 "
4.9
50000
40000
85000
TABLE 19.
Capacities of Hot-Air Pipes and Regristers.t
Q
fl t-i
«W -4-) "H
d
a
.M
.S 0)
o xni;
o
o
w
^^
4J
2
83 S3
o
•M
•3°
CJ 4)
m
. 'O
«
O
J
02
Equiv
round
pipe.
Equiv
squar
pipe.
Cubic
space
floor
lieat.
6x8
6 in.
4x8
400
450
500 ,
8x8
7 "
4x10
450
500
560
8x10
8 "
4x10
500
850
880
8x12
8 "
4x11
800
1000
1050
9x12
9 "
4x12
1050
1250
1320
9X14
9 "
4x14
1050
1350
1450
10X12
10 "
4x14
1500
1650
1800
10x14
10 "
6x10
1800
2000
2200
10x16
10 "
6x10
1800
200O
2200
12x14
12 "
6x12
2200
230O
2500
12x15
12 "
6x12
2250
2300
2500
12x17
12 "
6x14
2S0O
2600
2800
12x19
12 "
6x14
2300
2600
2800
14x18
14 "
6x16
280O
3000
3200
14x20
14 "
6x16
2900
30OO
3200
14x22
14 "
8x16
3000
3200
3400
16X20
IS "
8x18
3600
4000
4250
16X24
16 "
8x18
370O
4000
4250
20X24
18 "
10x20
48ot?
5400
5750
20x26
20 "
10x24
6000
7000
7450
•Federal Furnace League Handbook.
tKidder's Arch, and B'ld'rs. Pocket-Book.
351
TABLE 20.
Air Henting: Capacity of Warm Air Furnaces.*
Fire-pot
Casing
Total
cross sec.
area of
heat
pipes
No.
and size of heat pipes that
may be supplied
Diam.
Area
Diam.
18 in.
1.8 sq. ft.
30"-32''
20 "
2.2 "
Si'-se"
22 "
2.6 "
36"-40"
24 "
3.1 "
40"-44"
26 "
3.7 "
44"-50"
28 "
4.3 "
48"-56"
30 "
4.9 "
52"-60"
180 sq. in.
280
360
470
565
650
730
3-9' or 4-8*
2-10* and 2-9' or 3-9' and 2-8^
3-l(r and 2-9' or 4-9' and 2-8*
3-10*. 1-9' and 2-8' or 2-10" and 5-8'
5-10" and 3-9" or 3-10*, 4-9' and 2-8*
2-12', 3-10* and 3-9" or 5-10", 3-9' and 2-8"
3-12", 3-10" and 3-9' or 5-10", 5-9" and 1-8*
TABLE 21.
Sectional Area (Square InchcN) of Vertical Hot Air Flues,
Natural Dralt, Indirect Systeni.t
Outside temperature 50° F. Flue temperature 90° F.
Sq. ft.
STEAM
WATER
cast iron
-o
XI
•a
J3
radiation
4i >.
1^
4^ >.
"2 >»
.t o
■so
o o
.h c
^ °
J= O
o o
f^li
X UQ
E-* 00
^ to
PMtS
Km
^1^
f^^
to 50
100
75
63
60
75
63
60
60
50 " 75
150
113
94
80
113
94
80
80
75 " 100
200
150
125
100
150
125
100
100
100 " 125
250
188
156
125
188
156
125
125
125 " 150
300
225
188
150
225
188
150
150
150 " 175
350
263
219
175
263
219
175
175
175 " 200
400
300
250
200
300
250
200
200
200 " 225
450
338
281
225
3.S8
281
225
225
225 " 250
500
375
313
250
375
313
250
250
250 " 275
550
413
344
275
413
344
275
275
275 " 300
600
450
375
300
450
375
300
300
300 " 325
650
488
406
325
488
406
325
325
325 " 350
700
525
4:«
350
525
438
350
350
350 " 375
750
563
409
375
563
469
375
375
375 •' 400
800
600
500
400
600
500
400
400
Velocity
feet per sec.
2V^
i'^
5\4
6^/^
1%
2%
4
4
Effective area
of register.
1.00
1.50
1.83
2.17
1.00
1.00
1.33
1.33
Factor for
•Federal Furnace League Handbook.
tThe Model Holler Manual.
352
TABLE 22.
Sheet Metal Dimensions and Welgrhts.
Approximate
Wt. per sq
. ft. in lbs.
Decimal
Iron
Steel
U. S. gage
gage
millimeters
480 lbs. per
cu. ft.
489.6 lbs. per
cu. ft.
numbers
0.002
0.05
0.08
0.082
0.004
0.10
0.16
0.163
0.006
0.15
0.24
0.245
38-39
0.008
0.20
0.32
0.326
34-35
0.010
0.25
0.40
0.408
32
0.012
0.30
0.48
0.490
30-31
0.014
0.36
0.56
0.571
29
0.016
0.41
0.64
0.653
27-28
0.018
0.46
0.72
0.734
26-27
0.020
0.51
0.80
0.816
25-26
0.022
0.56
0.88
0.898
25
0.025
0.64
1.00
1.020
24
0.028
0.71
1.12
1.142
23
0.032
.0.81
1.28
1.306
21-22
0.036
0.91
1.44
1.469
20-21
0.040
1.02
1.60
1.632
19-20
0.045
1.14
1.80
1.836
18-19
0.050
1.27
2.00
2.040
18
0.055
1.40
2.20
2.244
17
0.060
1.52
2.40
2.448
16-17
0.065
1.65
2.60
2.652
15-16
0.070
1.78
2.80
2.856
15
0.075
1.90
3.00
3.060
14-15
0.080
2.03
3.20
3.264
13-14
0.085
2.16
3.40
3.468
13-14
0.090
2.28
3.60
3.672
13-14
0.095
2.41
3.80
3.876
12-13
0.100
2.54
4.00
4.080
12-13
0.110
2.79
4.40
4.488
12
0.125
3.18
5.00
5.100
11
0.135
3.43
5.40
6.508
10-11
0.150
3.81
6.00
6.120
9-10
0.165
4.19
6.60
6.732
8-9
0.180
4.57
7.20
7.344
7-S
0.200
5.08
8.00
8.160
6-7
0.220
5.59
8.80
8.976
4-5
0.240
6.10
9.60
9.792
3-4
0.250
6.35
10.00
10.200
3
For weights of galvanized iron, multiply weight, black, by: —
No. 28 No. 26 No. 24 No. 22 No. 20 No. 18 No. 16
1.25
1.21
1.16
1.13
1.11
1.07
353
TABLE 23.
T\>l8:ht of Round Galvanized Iron Pipe and Elbown of the
Proper Gases for HeatlnsT and Ventilating \%'ork.
Gage and
weight per
sq. ft.
•M
O
Circumf.
of pipe
in inches
Weight per
running
foot
♦I fa. 1
Gage and
weight per
sq. ft.
O
.So.
Circumf.
of pipe
in inches
1
a .
Weight per
running
foot
3
9.43
7.1
0.7
0.4
36
113.10
1017.9
17.2
124.4
4
12.57
12.6
1.1
0.9
37
116.24
1075.2
17.8
131.4
No. 28
5
15,71
19.6
1.2
1.2
38
119.38
1134.1
18.2
139.4
0.78
6
18.85
28.3
1.4
1.7
39
122.52
1194.6
18.7
146.0
7
21.99
38.5
1.7
2.3
40
125.66
1256.6
19.1
152.9
8
25.13
50.3
1.9
2.9
No. 20
41
128.81
1320.6
19.6
160.7
1.66
42
43
44
131.95
135.09
138.23
1385.4
1452.2
1520.5
20.1
20.6
21.0
168.6
176.7
185.0
9
10
28.27
31.42
63.6
78.5
2.4
2.7
4.3
5.3
No. 26
11
34.56
95.0
2.9
6.4
45
141.37
1590.4
21.5
193.4
0.91
12
13
14
37.70
40.84
43.98
113.1
132.7
153.9
3.2
3.4
3.7
7.6
8.9
10.4
46
144.51
1661.9
22.0
202.2
47
147.65
1734.9
29.2
274.3
15
47.12
176.7
4.5
13.5
48
150.80
1809.6
29.8
286.6
16
50.27
201.1
4.7
15.1
49
153.94
1885.7
30.4
298.8
No. 25
17
53.41
227.0
5.0
17.0
50
157.08
1963.5
31.0
309.9
1.03
18
56.55
254.5
5.3
19.1
51
160.22
2042.8
31.6
322.5
19
59.69
283.5
5.6
21.4
No. 18
52
163.36
2123.7
32.2
335.1
20
62.83
314.2
6.0
23.9
2.16
53
54
55
166.50 2206.2
169.65 2290.2
172.79 2375.8
33.0
:^3.6
34.4
349.7
463.4
377.2
21
65.97
346.4
7.0
29.6
56
175.93 2463.0
34.9
390.7
22
69.12
380.1
7.3
32.3
57
179.0712551.8
35.6
405.1
No. 24
23
72.26
415.5
7.7
35.6
58
182.21 2642.1
36.1
418.8
1.16
24
75.40
452.4
8.0
38.6
59
l85.35'-2734.0
36.7
433.1
25
78.54
490.9
8.3
41.7
60
188.50 2827.4
37.4
448.6
26
81.68
530.9
8.7
45.1
27
84.82
572.6
10.9
59.1
28
87.97
615.7
11.4
64.2
61
191.64 2922.5
46.7
569.7
29
91.11
660.5
11.8
68.6
62
194.78
3019.1
47.5
589.0
No. 22
30
94.25
706.0
12.2
73.4
63
197.92
3117.3
48.3
608.6
1.41
31
97.39
754.8
12^6
78.3 '
No. 16
64
201.06
3217.0
49.1
628.5
32
100.53
804.3
13.0
83.4
2.66
66
207.34
3421.2
50.5
666.6
33
103.67
855.3
13.5
88.9
68
213.63
3631.7
52.1
708.6
34
106.84
907.9
13.9
94.3
70
219.91
3848.5
53.6
750.4
35
100.96
962.1
14.3
99.9
72
226.19
4071.5
55.1
793.4
354
^
TABLE 24.
Specific Heats, Coefficients of E^xpansion, Coefficients of Trans-
mission, and Fusing^-Points of Solids, Liquids or Gases.*
SUBSTANCE
a) as
a o
ccx:
o
a a
.*§ M
<t-i oi
o|
OS
o a
C CO
a
0,
a <u
<u
S a?
Antimony
0.0508
0.0951
0.0324
0.1138
0.1937
0.1298
0.0314
0.0324
0.0570
0.0562
0.1165
0.1175
0"0956
0.0939
0.5040
0.2026
0.2410
0.1970
0.1887
1.0000
0.0333
0.7000
.00000602
.00000955
.00001060
.00000895
.00000478
.00000618
.00001580
.00000530
.00001060
.00001500
.00000600
.00000689
.00000003
.00001633
.00001043
.00000375
.00006413
.00007860
.00002313
.00012530
.00008806
.00003333
.00015151
.00022
.00404
7o6o89""
.0000008
.000659
.00045
'ooeio"
.00084
.00062
.00034
'06170"
.00142
.000024
T000602'
.00203
Toooooi"
.00011
.000002
815
Copper _ _
1949
Gold _ -
1947
Wrouglit iron
Glass __ __
2975
1832
Cast iron __ . _
2192
Lead
621
Platinum __
3152
Silver
Tin ..
1751
446
Steel (soft)
2507
Steel (hard)
Nickel steel 36%
Zinc
2507
'787
Brass
1859
Ice _ _ _ _
32
Sulphur
Charcoal __
Aluminum
1213
Phosphorus
Water _
Mercury
Alcohol (absolute )—
Con-
stant
pres-
sure
Con-
stant
volume
Coefficient
of cubical ex-
pansion at 1
atmos.
Air
Oxygen
Hydrogen
Nitrogen
Superheated steam _
Carbonic acid
0.23751
0.21751
3.40900
0.24380
0.4805
0.2170
0.16847
0.15507
2.41226
0.17273
0.346
0.1535
.003671
.003674
.003669
.003668
.003726
.0000015
.0000012
.0000012
.0000012
100060122
*Kent and Suplee.
355
r
TABLE 25.
Precmnre, In OunoeH, per Sqtinre Inch, Correspondlngr to
VarlouH Heads of Water, In Inches.*
Decimal parts of an inch
Head
in
.0
.1
.2
.3
.4
.5
.6
.7
.8
.9
inches
.06
.12
.17
.23
.29
.35
.40
.46
.52
1
.58
.63
.69
.75
.81
.87
.93
.98
1.04
1.09
2
1.16
1.21
1.27
1.33
1.39
1.44
1.50
1.56
1.62
1.67
3
1.73
1.79
1.85
1.91
1.96
2.02
2.08
2.14
2.19
2.25
4
2.31
2.37
2.42
2.48
2.54
2.60
2.66
2.72
2.77
2.83
5
2.89
2.94
3.00
3.06
3.12
3.18
3.24
3.29
3.35
3.41
6
3.47
3.52
3.58
3.64
3.70
3.75
3.81
3.87
3.92
3.98
7
4.04
4.10
4.16
4.22
4.28
4.33
4.39
4.45
4.50
4.56
8
4.62
4.67
4.73
4.79
4.85
4.91
4.97
5.03
5.08
5.14
9
5.20
5.26
5.31
5.37
5.42
5.48
5.54
5.60
5.66
5.72
TABLE 26.
Height of Water Column, In Inches, Corresponding? to Prea<
sures, in Ounces, per Square Inch.*
Decimal parts of an ounce
Pressure
in ounces
per square
.0
.1
.2
.3
.4
.5
.6
.7
.8
.9
inch
.17
.35
.52
.69
.87
1.04
1.21
1.38
1.56
1
1.73
1.90
2.08
2.25
2.42
2.60
2.77
2.94
3.11
3.29
2
3.46
3.63
3.81
3.98
4.15
4.33
4.50
4.67
4.84
5.01
3
5.19
5.36
5.54
5.71
5.88
6.06
6.23
6.40
6.57
6.75
4
6.92
7.09
7.27
7.44
7.61
7.79
7.96
8.13
8.30
8.48
5
8.65
8.82
9.00
9.17
9.34
9.52
9.69
9.86
10.03
10.21
6
10.38
10.55
10.73
10.90
11.07
11.26
11.43
11.60
11.77
11.95
7
12.11
12.28
12.46
12.63
12.80
12.97
13.15
13.32
13.49
13.67
8
13.84
14.01
14.19
14.36
14.53
14.71
14.88
15.05
15.22
15.40
9
15.57
15.74
15.92
16.09
16.26
16.45
16.62
16.76
16.96
17.14
•Suplee's M. E. Reference Book.
35S
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357
TABLE 28.
Expansion of Wrought-Iron Pipe on the Application of Heat.*
Temp, air
M'hen
Increase in
length in inches
per 100 feet
pipe
when heated to
is fitted
Deg. F.
160
180
200
212
220
228
240
274
1.28
1.44
1.60
1.70
1.76
1.82
1.92
2.19
32
1.02
1.18
1.34
1.44
1.50
1.57
1.66
1.94
50
,88
1.04
1.20
1.30
1.36
1.42
1.52
1.79
70
.72
.88
1.04
1.14
1.20
1.26
1.36
1.63
TABLE 29.
Tapping; Llsi of Direct Radiators.!
STEAM.
ONE-PIPE WORK.
TWO-PIPE WORK.
Radiator area
square feet
Tapping diam-
eter—inches
Radiator area
square feet
Tapping diam-
eter—inches
0— 24
. 24—60
60 — 100
100 and above
1
2
— 48
48 — 96
96 and above
1 X %
1^x1
l^^xl^
WATER.
Tapped for supply and return.
Radiator area
square feet
• Tapping diameter
inches
— 40
40 — 72
72 and above.
1
•Holland Heating Manual.
jAmerican Radiator Co.
358
i^.
TABLE 30.
Pipe Equalization.
(See also Table 19)
This table shows the relation of the
combined area of small round warm
air ducts or pipes to the area of one
large main duct.
The bold figures at the top of the
column represent the diameters of
the small pipes or ducts; those in
the left-hand vertical columns
aire the diameters of the main
pipes. The small figures show
the number of small pipes that
each main duct will supply.
Example.— To supply sixteen
10-inch pipes: Refer to column
having 10 at top; follow
down to small figure 16,
thence left on the hori-
zontal line of the bold-
face figure in the !
outside column, and
we find that one
80-inch main will
supply air for
the sixteen
10 - inch
pipes.
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359
TABLE 31.
Capacities of Hot Water Risers In Square Feet of Direct
Rndiation.*
Drop in temperature 20".
D. of
riser
inches
First
floor
Second
floor
Third
floor
Fourth
floor
Fifth
floor
Sixth
floor
%
12
22
38
66
140
240
350
510
700
17
33
56
92
196
328
490
705
980
21
40
70
112
238
400
595
860
1190
24
48
80
132
280
470
700
1010
1280
1
IVi
88
145
310
515
770
1110
1540
IV^
2
'iVz
3
3V^
4
850
1215
1660
A small pipe should never be run to a great height where It
only supplies one radiator. It is better to have limits for pipes
as follows:
D. in inches:
Height in feet:
20
1
30
1^
45
1%
60
2
80
(Reduce size by
floors.)
TABLE 32.
Capacities of Pipes In Square Feet of Direct Steam Radlatlon.f
i
i
g^
i
■M
O
g
to
O
<t-i
o
&
ti)
SaS
•Cm
CO
J2
S as
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e a w
S '- aJ
to
X2
n
£
qS.S
fi £i.S
04
i«
qS.s
Q£^.a
L.*?
1
1
36
60
5
31^
3720
6200
IV*
1
72
120
6
314
6000
10000"
1^^
ly*
120
200
7
4
9000
15000
2
iMs
280
480
8
4
12800
21600
21^
2
528
880
9
4^
178CX)
30000
3
21^
900
1500
10
5
23200
39000
ZVz
21/^
1320
2200
12
6
37000
62000
4
3
1920
3200 1
14
7
54000
92C00
4V^
3
2760
4600 1
16
8
76000
130000
•International Correspondence School.
fKent's M. E. Pockct-liook.
360
iH
TABLE 33.
Capacities of Hot Water Pipes in Square Feet of Direct
Radiation.'"
Indi-
rect
Direct radiation.
Diameter
radi-
Height of coil above bottom of boiler, in
ft.
of pipes,
inches
ation
10
20
30
40
50
70
100
sq. ft.
sq. ft.
sq. ft.
sq. ft.
sq. ft.
sq. ft.
sq. ft.
sq. ft.
%
49
50
52
53
55
57
61
68
1
87
89
92
95
98
101
108
121
114
136
140
144
149
153
158
169
189
11/2
196
202
209
214
222
228
243
271
2
349
359
370
380
393
405
433
483
21/2
546
561
577
595
613
633
678
755
3
785
807
835
856
888
912
974
1086
31/2
1069
1099
1132
1166
1202
1241
1327
1480
4
1395
1436
1478
1520
1571
1621
1733
1933
41/2
1767
1817
1871
1927
1988
2052
2193
2445
5
2185
2244
2309
2376
2454
2531
2713
3019
6
3140
3228
3341
3424
3552
3648
3897
4344
7
4276
4396
4528
4664
4808
4964
5308
. 5920
8
5580
5744
5912
6080
6284
6484
6932
7735
9
7068
7268
7484
7708
7952
8208
8774
9780
10
8740
8976
9236
9516
9816
10124
10852
12076
11
10559
10860
11180
11519
11879
12262
13108
14620
12
12560
12912
13364
13696
14208
14592
15588
17376
13
14748
15169
15615
16090
16591
17126
18307
20420
14
17104
17584
18109
18656
19232
19856
21232
23680
15
19634
20195
20789
21419
22089
22801
24373
27168
16
22320
22978
23643
24320
25136
25936
27728
30928
TABLE 34.
Capacities of Hot "Water Mains in Square Feet of Direct
Radiation.t
Total estimated length
of circuit
D. of
mams
100
200
300
400
500
600
700
800
900
1000
1
20
l^A
35
20
11^
56
40
25
2
116
85
70
50
2^
220
150
120
100
90
3
345
240
200
170
150
140
125
110
100
90
3%
500
340
280
245
225
205
190
175
162
150
4
700
485
390
340
310
280
260
240
230
220
41^
925
640
535
460
410
375
345
325
300
295
5
1200
830
700
600
540
490
450
420
400
380
6
1900
1325
1100
950
850
775
700
650
620
600
7
2000
1600
1400
1250
1140
1050
975
925
875
8
1970
1720
1550
1440
1350
1800
1250
9
190O
1800
1700
1620
•Kent's M. E. Pocket-Book.
tlnternational Correspondence School.
361
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364
L
TABLE 38.
Comparative Sizes of Steam Mains and Returns for Gravity
and Vacuum Systems.
Size of
Size of return
Size of
Size of return
supply
supply
pipe
Gravity
Vacuum
pipe
Gravity
Vacuum
%
%
^
4
2%
IVa
1
%
-"k
41/2
2y2
IV^
m
1
^k
5
3
2
1^/2
11/4
%
6
SVa
21/2
2
11/2
%
8
41/2
3%
2%
2
1
10
6
4
3
2
IV4
12
6
4%
3^
21/2
IV4
14
7
5
Note.— For short runs of piping where the friction is not a serious
matter the above table will work out satisfactorily. These sizes are
only approximate and should be used with caution.
TABLE 39.
Elxpansion Tanks — Dimensions and Capacities.*
Size in inches
Capacity gallons
Sq. ft, of radiation
9x20
5V^
150
10x20
8
250
12x20
10
350
12x24
12
450
12x30
15
550
12x36
18
650
14x30
20
700
14x36
24
850
16x30
26
900
16x36
33
1250
16x48
42
1750
18x60
66
2750
20x60
82
4500
22x60
100
600O
24x60
122
7500
•The Model Boiler Manual.
885
TABL3 40.
SUen of Flansred Fltttngrs.
AU flttinss
an
d
^
f/9
t^rEd - ' -
* 1 I
vl
fl
anges
fi'-
M
a
es
*5
?
tsfi
a
,2
1
r
tc4
so
90°
elbow
45»
elbow
Long
turn
elbow
Tee
Cross
Lateral
c
,
c
o
o
DO
4^
00
i?
t4
0^
00
tn
a
0.
0.
0.
rp
0.
rp
ON
0.
•w a
1, «
s
5
Eh
2;
s
OS
Q
Si
eg
<«-i
II
^5
C cj
6^
4
9
J8
8
7%
%
6%
4
10
6%
13
12
3
6
11
1
8
9%
%
8
5
13-
8
16
141A
3%
8
13^
1%
8
11%
%
9
6
16
9
18
17%
4%
10
16
i.-'e
12
141/4
%
11
7
20
11
22
20V,
5
12
19
IV4
12
17
%
12
7%
22
12
24
24%
5%
14
21
1%
14
18%
1
14
7%
24
14
28
27
a
16
23%
^•>
16
2114
1
15
8
28
15
30
30
fiH
'20
27%
IfA
20
25
1%
18 •
9%
32
18
36
35
8
24
32
1%
20
29%
1%
22
11
36
22
44
40%
9
TABLE 41.
Dimensions of Ells and Tees for W^ongrht Iron Pipe.
^ ^M^l
_
t- L
ff
••^,
~ \ /
- •[>
*-. — -
Size
%
H
1-
l-H
l-'A
2-
2-M
8-
8-H
4-
4-4
5-
6-
E
^8
%
l-Ks
1-^
i-.".
i-H
2-
2->^
2-X
8-^
8-^8
4-
i-H
i-H
6-^
R
^8
%
l-.^e
1-54
1-J4
1-H
2-/8
2-K
8-^8
8-H
4-
4-/8
i-h
D
1-
1-/8
1-Ji
l-^
l-%
2-H
2-%
S-%
4-
4-f^8
5-^
5-%
6-H
6-%
l-h
l-A
1-H
2-
2-H
2-Ji
4-
4-H
6-
«-x
7-^
i«
6
1 8
H
Ji
h
1-
1-
1-H
1-^
l-5i
1-H
l->i
2-y*
2-H
8-/8
8-X
4-
4-K
5 X
6-^
7-^
8-
8-\
9-H
11-
H
l-H
i-H
i-A
i-?i
2-
2-96
2-?i
8-H
8-H
4-
6-«
366
k^
TABLE 42.
Loss of Pressure In Pipes 100 Feet Long: tn Ounces per
Square Inch when Delivering Air at the Velocities Given.
^•1
Diameter of pipe in inches
Velo
in f
per
1
2
8
4
6
8
10
12
14
16
18
300
400
600
800
1000
1200
1500
1800
2400
0.100
0.178
0.400
0.711
1.111
1.600
2.500
3.600
6.400
0.050
0.088
0.200
0.356
0.556
O.80O
1.250
1.800
3.200
0.033
0.059
0.133
0.237
0.370
0.533
0.833
1.200
2.133
0.025
0.044
0.100
0.178
0.278
0.400
0.625
0.900
1.60O
0.017
0.030
0.067
0.119
0.185
0.267
0.417
0.600
1.067
0.012
0.022
0.050
0.089
0.139
0.200
0.312
0.450
0.800
0.010
0.018
0.040
0.071
0.111
0.160
0.250
0.360
0.640
0.008
0.015
0.033
0.059
0.092
0.133
0.208
0.300
0.533
0.007
0.013
0.029
0.051
0.079
0.114
0.179
0.257
0.457
0.006
0.011
0.025
0.044
0.069
0.100
0.156
0.225
0.400
0.006
0.010
0.022
0.040
0.062
0.089
0.139
0.200
0.356
20
24
28
32
36
40
44
48
52
56
60
300
400
600
800
1000
1200
1500
1800
2400
0.005
0.009
0.020
0.036
0.056
0.080
0.125
0.180
0.320
0.004
0.007
0.017
0.029
0.046
0.067
0.104
0.167
0.313
0.004
0.006
0.014
0.025
0.040
0.057
0.089
0.129
0.239
0.003
0.006
0.012
0.022
0.035
0.050
0.078
0.112
0.200
0.003
0.005
0.011
0.020
0.031
0.044
0.069
0.100
0.178
0.002
0.004
0.010
0.018
0.028
0.040
0.062
0.090
0.160
0.002
0.004
0.009
0.016
0.025
0.036
0.057
0.082
0.145
0.002
0.004
0.008
0.015
0.023
0.033
0.052
0.075
0.133
0.002
0.003
0.008
0.014
0.021
0.031
0.048
0.069
0.123
0.002
0.003
0.007
0.013
0.020
0.029
0.045
0.064
0.119
0.002
0.003
0.007
0.012
0.019
0.027
0.042
0.060
0.107
Diagrams for Pipe Sizes and Friction Heads.
To illustrate the use of the two following diagrams, ap-
ply to the pipe line, B, C, Art. 147. First, let I = 1500 feet,
d = 8 inches and v = 5 feet per second. Trace along the
velocity line until it intersects the diameter line, then fol-
low the ordinate to the top of the page and find the friction
head, 13 feet for 1000 foot run or 19.5 feet for the 1500 foot
run. Second, let Q = 1.75 cubic feet per second and d = S
inches. Trace to the left along the horizontal line represent-
ing the volume of 1.75 cubic feet until it Intersects the
diameter line, then read up and find the same friction head
as before. Third, let the allowable friction head for 1500
feet of main be 19 feet, when Q = 1.75 cubic feet per second
or when v = 5 feet per second. Reverse the process given
above and find an 8 inch pipe.
367
■aj^op39 dJj l3sj piwnp tJi [ &] JjbavHP^/cr
m
OQooooOO ooo omo >or\joco «Din^ cooi
O 7WPiit>i''— •" ___________
in ^J O CD
6 6
368
m ^„
<D * «^raM
~o^co.? ^«S.cj!2»S
<" « «Mr^». (O'rt't '^ ~<^'^ -" O O O OOO OOO
369
TABLE 43.
Temperatures for Testing: Direct Steam Radiation Plants.*
n
Test
condi-
Steam
Tem-
pera-
Steam i
pressure intended for
zero
weather
>
tion
ture
lb.
1 lb.
2 lb.
3 lb.
4 lb.
5 lb.
6 lb.
7 lb.
8 lb.
9 lb.
10 lb.
o
10
in.
192.0
63.3
62.3
m
9
194.5
64.2
63.2
62.3
a
8
197.0
65.0
64.0
63.0
62.2
7
199.0
65.6
64.7
63.7
62.8
62.0
"H
6
201.0
66.3
65.3
64.3
63.4
62.6
62.0
5
203.0
67.0
66.0
65.0
64.0
63.3
62.6
61.9
a
4
205.0
67.6
66.6
65.6
64.7
as. 9
63.2
62.5
61.7
,
3
207.0
68.3
67.2
66.2
65.3
64.5
63.8
63.1
62.3
61.7
en
2
208.5
68.8
67.7
66.7
65.7
65.0
64.2
63.6
62.8
62.0
61.5
1
210.5
69.4
68.3
67.5
66.4
6'). 6
64.8
64.2
63.3
62.6
62.1
61. fl
lb.
212.0
70.0
68.8
67.8
66.9
66.1
65.3
64.6
63.8
63.1
62.6
62.0
a
1
215.5
71.2
70.0
69.0
68.0
67.2
66.3
65.8
65.0
frl.2
63.7
63.0
00
2
218.7
72.1
71.0
70.0
69.2
68.2
67.3
66.7
65.9
65.1
64.5
64.0
£i
3
221.7
72.0
71.0
70.0
69.2
68.3
67.6
66.7
66.0
65.4
64.8
.
4
224.5
71.8
70.8
70.0
69.2
68.4
67.5
66.7
66.2
65.7
s
00
5
227.2
71.7
70.8
70.0
69.2
68.3
67.6
67.0
66.3
6
229.8
71.7
70.8
70.0
69.2
68.4
67.7
67.2
»
7
232.4
71.7
70.8
70.0
69.2
68.6
68.0
a
8
234.9
71.7
70.8
70.0
69.3
68.7
a>
9
237.3
71.5
70.5
70.0
69.3
10
239.4
71.3
70.7
70.0
Factors
".670
.675
.678
.684
.688
.692
.694
.698
.702
.705
.707
The temperatures inthis table are for a plant designed for 0° and 70'.
Example. — It is desired to test a plant designed for 5 pounds gage
pressure on a day when the outside temperature is 22 degrees. What
should be the temperature in the rooms with steam at 3 pounds gage
pressure? It will be noted in the vertical column marked 5 pounds, that
opposite the 3 pound pressure 68.3 degrees may be expected on a zero
day. As the temperature was 22 degrees above we must add 22 times
.692, or 15.2 degrees, thus making a total of 83.5 degrees, the tempera-
ture which should exist indoors.
t.
*W. W. Macon.
^•/o
8i
n
e
fl
es
o
ae
fl
©
s
s
"S
a
9ft
OS 00 o
<M C» CO CO
bo
C
a;
.c
;^
4)
S
s
(V
-t->
02
a
:^
;f3
00 CO
■^ T-l
88
88
00 o
(N to i^ eo CO
■* lO •* o
t^ 00 o i-H
&q 00
w in o
CO 00 C^ rH
o
00 00 <0 >-( CO _
CO I 1-1 Cv)
i« T CO (M
c^ t^ in 'i in
(M CO •^ *? in m
<>4 c^,-^cg
CO in ©
00 00 c^ 00
in in o
oco '*'9 in
e!i r-t
o CO ■<*<'9 in
<N ell i-i
88
<M 00 O
oooooo'cj
88
(M 05
88
05 Ml
88
1> rH
;f3
CO t^
O 00
CO CO ■»}( CO
t> © o
(M . . .
<M t» M t~
in CO ©
00 CO ©
in t- CO Ttt
■«*< CO ©
CO • • •
o> t^ CO 00
I t-KtH
I c c
I ! i
i ! i
I ' •
I g (-1
I a <u
to CO tn (/2 »J
QJ q^ ^ Q^ QJ
x: J3 J5 x: J3
o u u u u
a a a a a
I I
J X «
>< o o
a>
CS CS
03 C3
a c;'t)
•4-1 <t-l 3 <(-l
■g O O*-" o
jr S 0-' N S
^_, t- O) o
"gas
;^ *s <t-m-i
+i 4J to
O)
a>
« .2 c3 .ii
C S3 cr «
371
TABLE 45.
Percentage of Heat Transmitted by Various Plpe-Coverlngrs.
From Tests Made at Sibley College, Cornell I'niverslty,
and at Michigan L'niversity.*
Relative amount
Kind of covering of heat
transmitted
Naked pipe 100.
Two layers asbestos paper, 1 in, hair felt, and canvas
cover 15.2
Two layers asbestos paper, 1 in. hair felt, canvas
cover wrapped with manilla paper 15.
Two layers asbestos paper, 1 in. hair felt 17.
Hair felt sectional covering, asbestos lined 18.6
One thickness asbestos board 59.4
Four thicknesses asbestos paper 50.3
Two layers asbestos paper^ 77.7
Wool felt, asbestos lined 23.1
Wool felt with air spaces, asbestos lined 19.7
Wool felt, plaster paris lined 25.9
Asibestos molded, mixed with plaster paris 31.8
Asbestos felted, pure long fibre 20.1
Asbestos and sponge 18.8
Asbestos and wool felt 20.8
Magnesia, molded, applied in plastic conditnon 22.4
Magnesia, sectional 18.8
Mineral wool, sectional 19.3
Rock wool, fibrous 20.3
Rock wool, felted 20.9
Fossil meal, molded, % inch thick 29.7
Pipe painted with black asphaltum 105.5
Pipe painted with light drab lead paint 108.7
Glossy white paint 95.0
•Carpenter's H. and V. B.
Note. — These tests agree remarkably well with a series
made by Prof. M. E. Cooley of Michigan University, and also
with some made by G. M. Brill, Syracuse, N. Y., and reported
in Transactions of the American Society of Mechanical En-
gineers, vol. XVI.
%T%
TABLE 46.
Factors of Evaporation.
Gage
1
.3
10
20.
SO
50
100
125
135
150
175
pressure
Feed
water
Factors of evaporation
212
1.0003
1.0103
1.0169
1.0218
1.0290 1.0396
1.0431
1.0443
1.0460
1.0481
200
1.0127
1.0227
1.0293
1.0343
1.0414
1.0520
1.0555
1.0567
1.0584
1.0608
185
1.0282
1.0382
1.0448
1.0498
1.0569
1.0675
1.0710
1.0722
1.0739
1.0763
170
1.0437
1.0537
1.0603
1.0653
1.0724
1.0830
1.0865
1.0877
1.0894
1.0917
155
1.0592
1.0692
1.0758
1.0807
1.0878
1.0985
1.1020
1.1032
1.1048
1.1072
140
1.0715
1.0846
1.0912
1.0962
1.1033
1.1139
1.1174
1 1186
1.1203
1.1227
125
1.0901
1.1001
1.1067
1.1116
1.1187
1.1293
1.1328
1 1341
1 1357
1.1381
110
1.1055
1.1155
1.1221
1.1270
1.1341
1.1447
1.1482
1 1495
1 1511
1.1535
95
1.1209
1.1309
1.1.375
1.1424
1.1495
1.1602
1.1637
1.1649
1 . 1665
1.1689
80
1,1363
1.1463
1.1529
1.1578
1.1650
1.1756
1.1791
1.1803
1.1820
1.1843
65
1.1517
1.1617
1.1683
1.1733
1.1804
1.1910
1.1945
1.1957
1.1974
1.1997
50
1.1672
1.1772
1.1838
1.1887
1.1958
1.2064
1.2099
1.2112
1.2128
1.2152
35
1.1827
1.1927
1.1993 1.2042 1.2113
1.2219
1.2255
1.2267
1.2283
1.2307
TABLE 47.
Per Cent, of Total Heat of Steam Saved per Degrree Increase
of Feed W^ater.
Initial
Gage pressure
in boiler, lbs. per sq. in.
temp,
of feed
20
40
60
80
ICO
120
140
160
180
32
.0872
.0861
.0855
.0851
.0847
.0844
.0841
.0839
.0837
.0835
40
.0878
.0867
.0861
.0856
.0853
.0850
.0847
.0845
.0843
.0839
50
.0886
.0875
.0868
.0864
.0860
.0857
.0854
.0852
.0850
.0846
60
.0894
.0883
.0876
.0872
.0867
.0864
.0862
.0859
.0856
.0853
70
.0902
.0890
.0884
.0879
.0875
.0872
.0869
.0867
.0864
.0860
80
.0910
.0898
.0891
.0887
.0883
.0879
.0877
.0874
.0872
.0868
100
.0927
.0915
.0908
.0903
.0899
.0895
.0892
.0890
.0887
.0883
120
.0945
.0932
.0925
.0919
.0915
.0911
.09:18
.0906
.0903
.0899
140
.0963
.0950
.0943
.0937
.0932
.0929
.0925
.0923
.0920
.0916
160
.0982
.0968
.0961
.0955
.0950
.0946
.0943
.0940
.0937
.0933
180
.1002
.0988
.0981
.0973
.0969
.0965
.0961
.0958
.0955
.0951
200
.1022
.1008
.0999
.0993
.0988
.0984
.0980
.0977
.0974
.0969
220
.1029
.1019
.1013
.1008
.1004
.1000
.0997
.0994
.0989
.240
.1050
.1041
.1034
.1029
.1024
.1020
.1017
.1014
.1009
Example.— Boiler pressure 120 lbs. gage, initial temperature of feed
water 60 deg., heated to 210 deg. Then increase in temperature 150,
times tabular figure, .0862, equals 12.93 per cent, saving.
373
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374
...^^
TABLE 49.
Steatn Consuiuption of Various Types of Non-Condensing
Engines.* (Approximate).
Pounds per indicated horse-power hour.
i-s
■ en
en
OD
m
tn
Simple thr(
tling 100 It
at throttle
Simple aut
matic 100 1
initial
Simple Cor
100 lbs.
initial
Simple f oui
valve 100
lbs. initial
Compound
four valve
and Corlis
100 lbs.
initial
Compound
four valve
and Corlis
125 lbs.
initial
Compound
four valve
and Corlisi
150 lbs.
initial
10
52
20
50
40.0
30
49
39.0
40
48
38.0
50
48
38.0
34.5
35.0
60
47
36.0
32.5
33.0
70
47
35.0
31.5
32.0
80
46
34.0
30.5
31.0
90
45
33.0
29.5
30.0
100
45
32.0
28.5
29.0
150
44
31.5
28.0
28.5
22.5-23
21.5-22
21-21.5
200
43
30.5
27.0
27.5
22-22.5
21-21.5
90.5-21
250
43
30.0
26.5
27.0
22-22.5
21-21.5
20-20.5
300
42
29.0
25.5
26.0
22-22.5
20.5-21
20-20.5
400
41
28.5
25.0
25.5
21.5-22
20-20.5
19.5-20
500
41
28.5
25.0
25.5
20-21.5
19.5-20
10-19.5
The foregoing table was compiled principally from the records of a
large number of actual tests of engines of various makes, under reason-
ably favorable conditions. It is based upon the actual weight of eoT
densed exhaust steam.
*Atlas Engine Works Catalog.
879
^
TABLE 50.
Speedn, Capacltlen and HorNe-Powern of "Green" Steel Plate
FnnM at Varying Pressures.*
s-s
.26 in.
.87 in.
1.3 in.
1.7 in.
2.2 in.|2.6 in.
3.02 in.
3.46 in.
4.33 in.
« a
Pressures
5l
V* oz.
^^ oz.
% oz.
1 oz.
1^ oz V/ii oz
1% oz.
2 oz.
2V^ oz.
CU. FT.
2249
3176
3891
4498
5029
5513
5956
6372
7135
30
R. P. M.
S.SO
466
571
660
738
809
874
9;?5
1047
H. P.
.286
.811
1.491
2.298
3.213
4.227
5.311
6.515
9.120
CU. FT.
3239
4581
5605
6477
7242
7937
8584
9173
10268
36
R. P. M.
275
389
476
550
615
674
729
779
872
H. P.
.413
1.170
2.148
3.311
4.625
6.086
7.681
9.375
13.125
CU. FT.
4398
6214
7617
8815
9864
10799
11679
124&3
13981
42
R. P. M.
23.")
332
407
471
527
577
624
667
747
H. P.
.557
1.576
2.898
5.473
6.300
8.287
10.450
12.750
17.825
CU. FT.
5750
8123
9937
11500
12867
14123
15240
16301
18282
48
R. P. M.
206,
291
356
412
461
506
546
584
655
H. P.
.733
2.076
3.810
5.880
8.223
10.832
13.636
16.670
23.370
CU. FT.
7602
10758
13167
15203
17030
18650
20145
21558
24174
54
R. P. M.
183
259
317
366
410
449
485
519
582
H. P.
.970
2.750
5.047
7.767
10.880
14.300
18.017
21.992
30.896
CU. FT.
9715
13718
16780
19429
21725
23786
25728
27495
3079-2
60
R. P. M.
165
233
2S5
330
369
404
437
467
523
H. P.
1.241
3.506
6.433
9.932
13.882
18.230
22.996
28.077
39.355
Cr. FT.
12078
17071
20855
24156
26975
29551
32047
34221
38247
66
R. P. M.
150
212
259
300
335
367
398
425
475
H. P.
1.542
4.361
7.996
12.352
17.238
22.666
28.675
35.123
48.895
CU. FT.
15608
21942
26918
31103
34835
38115
41169
44109
49312
72
R. P. M.
1,38
194
238
275
308
337
364
390
436
H. P.
1.983
5.601
10.322
15.881
22.252
29.223
36.808
45.043
62.783
CU. FT.
20192
28405
34907
40383
45174
49452
53387
57152
63996
84
R. P. M.
118
166
204
236
264
289
312
334
374
H. P.
2.. 581
7.262
13.387
20.650
28.875
37.931
47.775
58.450
81.812
CU. FT.
23008
32614
39762
46016
51601
56515
60983
65227
73045
96
R. P. M.
103
146
178
206
231
253
273
292
327
H. P.
2.941
8.337
15.261
23.531
32.982
43.348
54.511
66.707
93.380
CU. FT.
29260
41027
50568
58519
65198
71559
77284
82690
92549
108
R. P. M.
92
129
159
184
205
225
243
260
291
H. P.
3.737
10.488
19.397
30.060
41.666
54.871
69.163
84.556
118.291
CU. FT.
36209
51042
62384
71982
80270
88559
95539
102063
114298
120
R. P. M.
83
117
143
165
184
203
219
234
262
H. P.
4.628
13.050
23.925
36.807
51.307
67.928
85.495
104.401
146.116
CU. FT.
43560
61565
75504
87120
97575
106868
115580
123711
138231
132
R. P. M.
75
106
130
150
168
184
199
213
238
H. P.
5.568
15.730
28.957
44.550
62.370
82.096
103.430
126.521
176.715
CU. FT.
52026
73138
89726
103298
116116
127426
137228
147030
164372
>44
R. P. M.
69
97
119
137
154
169
182
195
218
H. P.
6.65
18.700
34.411
52.822
74.221
97.741
1?" 802
150.3">
♦
210.133
Manufacturer's Note.— The horse-power required to drive a fan will
vary according to the manner of application. The horse-powers given
above are 25 per cent, greater than would be required under ideal con-
ditions.
k
TABLE 51.
Speeds, Capacities and Horse-Powers of "A. B. C.*' Steel
Plate Fans at Varying Pressures.*
t4
<a 3
o
Q is
Static
press.
V2''
1"
IVz"
2"
2V2''
3*
Si/^"
4"
.29
oz.
.58
oz.
.87
oz.
1.16
OZ.
1.44
OZ.
1.73
OZ.
2.02
OZ.
2.31
OZ.
50
30
C. F. M.
R. P. M.
B. H. P.
3840
471
.88
5425
665
2.48
6640
816
4.55
7650
945
7.00
8595
1060
9.81
9400
1150
12.85
10110
1250
16.20
10810
1330
19.75
60
36
C. F. M.
R. P. M.
B. H. P.
5475
893
1.25
7740
555
3.53
9460
681
6.49
10900
786
9.94
12250
880
14.00
13400
961
18.35
14410
1040
23.10
15420
1110
28.10
70
42
C. F. M.
R. P. M.
B. H. P.
7100
336
1.62
10020
475
4.58
12280
583
8.35
14150
675
12.93
17200
590
15.71
15900
755
18.19
17400
825
23.80
18700
890
29.90
20010
950
36.60
80
48
C. P. M.
R. P. M.
B. H. P.
8640
294
1.97
12200
416
5.57
14950
511
10.20
19350
660
22.10
21150
722
28.90
22800
780
36.50
29000
693
46.40
24350
832
44.50
90
54
C. F. M.
R. P. M.
B. H. P.
11000
262
2.52
15540
370
7.08
19000
454
13.00
21900
525
20.00
24600
587
28.10
26950
641
36.85
31000
740
56.50
100
60
C. F. M.
R. P. M.
B. H. P.
14050
236
3.21
19850
333
9.05
24300
409
16.65
28000
473
25.60
31450
529
35.95
34400
578
47.10
37000
625
59.10
39600
665
72.30
110
66
C. F. M.
R. P. M.
B. H. P.
16600
214
3.80
2350O
303
10.75
28800
371
19.70
33100
430
30.25
37200
480
42.50
40700
525
55.60
43800
568
70.00
46900
605
85.60
120
72
C. F. M.
R. P. M.
B. H. P.
20300
196
4.64
28700
278
13.10
3510O
340
24.00
40500
394
37.00
45500
440
52.00
49700
481
68.00
53500 57300
520 555
85.50104.50
140
84
C. F. M.
R. P. M.
B. H. P.
27400
168
6.25
38700
238
17.75
47400
292
32.40
54500
337
49.80
61300
378
70.00
67000
413
91.70
72200
445
115.20
77250
475
140.9
' 160
96
C. F. M.
R. P. M.
B. H. P.
34500
147
7.88
48900
208
22.30
59800
256
41.00
68900
296
62.90
77300
331
88.40
84500
362
115.5
91000
390
145.4
97500
416
178.0
180
108
C. F. M.
R. P. M.
B. H. P.
42600
131
9.75
60300
185
27.55
73800
227
50.50
85000
262
77.60
95500
293
109.0
104300
320
143.0
112500
346
180.0
120003
369
219.0
200
120
C. F. M.
R. P. M.
B. H. P.
51600
118
11.8
73000
166
33.30
89400
204
61.20
103000
236
93.50
115700
264
132.1
126500
289
173.0
136100
312
217.50
145800
332
266.0
220
132
C. F. M.
R. P. M.
B. H. P.
61400
107
14.0
8680O
151
39.60
106000
185
72.50
122200
214
111.50
137400
240
157.0
150200
262
206.0
162000
283
259.0
173000
302
316.0
240
144
C. F. M.
R. P. M.
B. H. P.
72000
98
16.5
101800
139
46.50
124500
170
85.00
143500
197
131.00
161000
220
184.0
176000
241
241.0
189500
260
303.0
203000
377
370.5
Manufacturer's Note.— Any of the above fans, when running at the
speed and pressure indicated, will deh'ver the volume of air and require
no more power than given in the table.
Allowances must be made for the inefficiency of the motive power
and for transmission losses between motive power and the fan.
*Condensed from the A. B. C. Co. Catalog.
377
TABLE 52.
Speeds, Capacities and Horne-PoTvers of <<Slrocco** Fans at
Varying Pressures.*
u
Pressures
in.
1
in.
in.
in.
2
in.
2V6
In.
3
in.
3%
in.
4
in.
a -
.43
oz.
.58
oz.
.72
oz.
.87
oz.
1.16
oz.
1.44
oz.
1.73
oz.
2.02
oz.
2.31
oz.
4
24
C. F. M.
R. P. M.
B. H. P.
4260
391
.879
4920
453
1.348
5500
505
1.89
6020
554
2.475
6945
640
3.8
7770
714
5.32
8520
783
7.00
9200
846
8,825
9840
905
10.77
5
30
C. F. M.
R. P. M.
B. H. P.
6650
313
1.37
7690
362
2.105
8600
403
2.96
9416
443
3.868
10870
512
5.95
12150
571
8.315
13320
625
10.94
14380
676
13.80
15380
724
16.85
6
36
C. F. M.
R. P. M.
B. H. P.
9580
260
1.975
11060
302
3.03
12350
336
4.25
13540
369
5.563
15630
427
8.56
17470
477
11.96
19150
523
15.72
206S0
565
19.85
22150
604
24.23
7
42
C. F. M.
R. P. M.
B. H. P.
13050
223
2.69
15070
259
4.126
16800
288
5.78
18425
316
7.565
21260
366
11.66
23800
408
16.28
26100
447
21.43
28200
483
27.06
30140
517
33
I
*» 48
C. F. M.
R. P. M.
B. H. P.
17000
196
3.51
19700
226
5.39
22000
252
•7.58
24100
277
9.9
27820
320
15.22
31100
358
21.30
34080
392
28.0
36800
424
35.3
39370
453
43.15
9
54
C. F. M.
R. P. M.
B. H. P.
21500
174
4.43
24860
201
6.81
27800
224
9.57
30440
246
12.52
35140
285
19.23
39300
317
26.94
43100
348
35.38
46600 49803
376 402
44.70 54.5
10
60
C. F. M.
R. P. M.
B. H. P.
26500
156
5.46
30750
181
8.42
34300
202
11.8
37650
222
15.47
43400
256
23.77
48570
286
33.23
53220
313
43.72
57500
338
55.2
61500
362
67.4
1
66
C. F. M.
R. P. M.
B. H. P.
32200
142
6.65
37200
165
10.18
41500
184
14.3
45530
202
18.72
52550
233
28.77
58830
260
40.24
64450
285
52.9
69630
308
66.85
74400
329
81.5
12
C. F. M.
72 R. P. M.
B. H. P.
38300
130
7.9
44240
151
12.11
49400
168
17
54180
185
22.25
62500
214
34.2
69900
238
47.85
76600
261
63
82800
282
79.5
885f)0
302
97
13
78
C. F. M.
R. P. M.
B. H. P.
45000
120
9.28
52000
140
14.22
58100
155
20
63600
171
26.16
735(X)
197
40.22
82100
220
56.2
90000
241
74
97300
261
93.35
104000
279
113.9
14
84
C. F. M.
R. P. M.
B. H. P.
52100
112
10.75
60200
130
16.49
67300
144
23.2
73700
158
30.3
85000
183
46.6
95000
204
65
104200,112700
224 24-2
85.61 108
12041X)
259
132
15
90
C. F. M.
R. P. M.
B. H. P.
59900
104
12.34
69230
121
18.93
77500
135
26.6
84700
148
34.8
97800
171
53.55
109200
191
74.9
119800129600
209 226
98.5 124.2
138500
242
151.7
16
96
C. F. M.
R. P. M.
B. H. P.
67950
98
13.98
78430
114
21.5
81800
126
30.2
96140
139
39.6
114300
160
63
124500
178
85.7
136000
196
112
147000
211
142
157300
226
173
'Condensed from A. B. C. Co. Catalog.
378
APPENDIX II
References used Chiefly in Refrigeration
and Ice Production
379
TABLE 53.
Freezing; Mixtures.*
Names and proportions of ingredients
in parts
Reduction of
temp. deg. F.
Prom To
Total
Reduc-
tion of
temp,
deg. P.
Snow or pounded ice 2; sodium chloride 1
Snow 5; sodium chloricle 2; ammonium chloride 1
Snow 12; sodium chloride 5; ammonium nitrate 5
Snow 8; calcium chloride 5
Snow 2; sodium chloride 1
Snow 3; dilute sulphuric acid 2
Snow 3; hydrochloric acid 5
Snow 7; dilute nitric acid 4
Snow 3; potassium 4
Ammonium chloride 5; potassium nitrate 5;
water 16
Ammonium nitrate 1; water 1
Ammonium chloride 5; potassium nitrate 5;
sodium sulphate 8; water 16
Sodium sulphate 5; dil. sulphuric acid 4
Sodium nitrate 3; dil. nitric acid 2
Ammonium nitrate 1; sodium carbonate 1;
water 1 •_._
Sodium sulphate 6; ammonium chloride 4;
potassium nitrate 2; dil. nitric acid 4
Sodium phosphate 9; dil. nitric acid 4
Sodium sulphate 6; ammonium nitrate 5;
dil. nitric acid 4
-t-32
+32
+32
+32
+32
+50
+50
+50
+ 50
+50
+50
+ 50
+50
+50
— 5
—12
—25
—10
— 5
—23
—27
—30
—51
— 3
—10
—12
—14
55
59
62
83
46
46
46
47
53
57
60
62
64
TABLE 54.
Properties of Saturated Ammonla.t
Pressure
Vol. of
Vol. of
Wt. of
Temp.
absolute
Heat of
.vapor
liquid
vapor
deg. P.
lbs. per
vaporization
per lb.
per lb.
lbs. per
sq. m.
cu. ft. i
cu. ft.
cu. ft.
—40
10.69
579.67
24.38
.0234
.0411
—35
12.31
576.69
21.21
.0236 .
.0471
—30
14.13
573.69
18.67
.0237
.0535
—25
16.17
570.68
16.42
.0238
.0609
—20
18.45
567.67
14.48
.0240
.0690
—15
20.99
564.64
12.81
.0242
.0775
—10
23.77
561.61
11.36
.0243
.0880
— 5
27.57
558.56
9.89
.0244
.1011
±
30.37
555.50
9.14
.0246
.1094
+ 5
34.17
552.43
8.04
.0247
.1243
+10
38.55
549.35
7.20
.0249
.1381
+20
47.95
543.15
5.82
.0252
.1721
+30
59.41
536.92
4.73
.0254
.2111
+40
73.00
5.30.63
3.88
.0257
.2577
+50
88.96
524.30
3.21
.02()01
.3115
+60
107.60
517.93
2.67
.()2(i5
.3745
+70
129.21
511.52
2.24
.02(18
.4664
+80
154.11
• 504.66
1.89
.0272
.5291
+90
182.80
498.11
1.61
.0274
.6211
+ 100
215.14
491.50
1.36
.0279
.7353
'Taylcr. Pocket IJook of Refrigeration,
t Wood— Thermodynamics, Heat Motors and Refrigerating Machines.
380
TABL.E 55.
Solubility of Ammonia in Water at DlflEerent Temperature*
and Pressures. (Sims).*
1 rb. of water (also unit volume) absorbs the following
quantities of ammonia.
Absolute
32°
F.
68° F.
104°
F.
212°
F.
pressure
in lbs.
per
sq. in.
Lbs.
Vols.
Lbs.
Vols.
Lbs.
Vols.
Grms.
Vols.
14.67
0.899
1180
0.518
683
0.338
443
0.074
97
15.44
0.937
1231
0.535
703
0.349
458
0.078
102
16.41
0.980
1287
0.556
730
0.363
476
0.083
109
17.37
1.029
1351
0.574
754
0.378
496
0.088
115
18.34
1.077
1414
0.594
781
0.391
513
0.092
120
19.30
1.126
1478
0.613
805
0.404
531
0.096
126
20.27
1.177
1546
0.632
830
0.414
543
0.101
132
21.23
1.236
1615
0.651
855
0.425
558
0.106
139
22.19
1.283
1685
0.669
878
0.434
570
0.110
140
23.16
1.336
1754
0.685
894
0.445
584
0.115
151
24.13
1.388
1823
0.704
924
0.454
596
0.120
157
25.09
1.442
1894
0.722
948
0.463
609
0.125
164
26.06
1.496
1965
0.741
973
0.472
619
0.130
170
27.02
1.549
2034
0.761
999
0.479
629
0.135
177
27.99
1.603
2105
0.780
1023
0.486
638
28.95
1.656
2175
0.801
1052
0.493
647
30.88
1.758
2309
0.842
1106
0.511
671
32.81
1.861
2444
0.881
1157
0.530
696
34.74
1.966
2582
0.919
1207
0.547
718
36.67
2.070
2718
0.955
1254
0.565
742
TABLE 56.
Strengrtli of Ammonia Liquor.*
Degrees
Specific
Percent- .
Degrees
Specific
Percent-
Baume
gravity
age
Baume
gravity
age
10
1.0000
0.0
20
0.9333
17.4
11
0.9929
1.8
21
0.9271
19.4
12
0.9859
3.3
22
0.9210
21.4
13
0.9790
5.0
23
0.9150
23.4
14
0.9722
6.7
24
0.9090
25.3
15
0.9655
8.4
25
0.9032
27.7
16
0.9589
10.0
26(a)
0.8974
30.1
17
0.9523
11.9
27
0.8917
32.5
18
0.9459
13.7
28
0.8860
35.2
19
0.9396
15.5
29
0.8805
Note. — Sp. gr. of pure anhydrous ammonia = .623
(a) Known to the trade as *'29i^ per cent."
*Tayler. Pocket-Book of Refrigeration.
381
TABLE 57.
Properties of Saturated Sulphur Dioxide. (Ledonx).*
Temp, of
Absolute
pressure
Total heat
Latent heat
Heat of
liquid
from
32 deg. P.
Density ol
ebullition
lbs. per
from
ol vapor-
vapor
deg. F.
sq. in.
P -T- 144
32 deg. P.
ization
wt. per
cu. ft.
—22
5.56
157.43
176.99
—19.56
.076
—13
7.23
158.64
174.95
—16.30
.097
— 4
9.27
159.84
172.89
—13.05
.123
5
11.76
161.03
170.82
— 9.79
.153
14
14.74
162.20
168.73
— 6.53
.190
23
18.31
163.36
166.63
— 3.27
.232
32
22.53
164.51
164.51
0.00
.282
41
27.48
165.65
162.38
3.27
.340
50
33.25
166.78
160.23
6.55
.407
59
39.93
167.90
158.07
9.83
.483
68
47.61
168.99
155.89
13.11
.570
77
56.39
170.09
153.70
16.39
.669
86
66.36
171.17
151.49
19.69
.780
95
77.64
172.24
149.26
22.98
.906
104
90.31
173.30
147.02
26.28
1.046
TABLE 58.
Properties of Saturated Carbon Dioxlde.f
Temp, of
Absolute
Total heat
Latent heat
Heat of
Density of
ebullition
pressure
from
of vapor-
liquid from
vapor or
deg. F.
in lbs.
per sq. in.
32 deg. P.
ization
32 deg. P.
wt. per
cu. ft.
—22
210
98.35
136.15
-37.80
2.321
—13
249
99.14
131.65
—32.51
2.750
— 4
292
99.88
126.79
—26.91
3.265
5
342
100.58
121.50
—20.92
8.853
14
396
101.21
115.70
—14.49
4.535
23
457
101.81
109.37
— 7. .56
5.331
32
525
102.. 35
102.. 35
0.00
6.265
41
599
102.84
94.52
8.32
7.374
50
680
103.24
85.64
17.60
8.708
59
768
103.59
75.37
28.22
10.356
68
864
103.84
62.98
40.86
12.480
77
968
103.95
46.89
57.06
15.475
86
1080
103.72
19.28
84.44
21.519
•Kent's M. E. Pocket-Rook.
n. C. S. Pamphlet 1238 B.
3S9.
^
TABLE 59.
Pressures and Boiling: Points of Liquids Available for Use
in Refrig:eratingr Macliincs.i'
Temperature
Pressure
of vapor
of ebullition
Pounds per square inch absolute
deg, F.
Sulphur
dioxide
Ammonia
Carbon
dioxide
Pictet
fluid
—40
10.22
—31
13.23
—22
5.56
16.95
—13
7.23
21.51
251.6
— 4
9.27
27.04
292.9
13.5
5
11.76
33.67
340.1
16.2
14
14.75
41.58
393.4
19.3
23
18.31
50.91
453.4
22.9
32
22.53
61.85
520.4
26.9
41
27.48
74.55
594.8
31.2
50
33.26
89.21
676.9
36.2
59
39.93
105.99
766.9
41.7
68
47.62
125.08
864.9
48.1
77
56.39
146.64
971.1
55.6
86
66.37
170.83
1085.6
64.1
95
77.64
197.83
1207.9
73.2
104
90.32
227.76
1338.2
82.9
TABLE 60.
Table of Calcium Brine Solution.f
Deg.
Baume
Per cent,
calcium
Lbs. per
Specific
Specific
Freezing
point
deg. F.
Amm.
60 deg.
F.
by
weight
cu. ft.
solution
gravity
heat
gage
pressure
0.000
0.0
1.000
1.000
32.00
47.31
2
1.886
2.5
1.014
.988
30.33
45.14
4
3.772
5.0
1.028
.972
28.58
43.00
6
5.658
7.5
1.043
.955
27.05
41.17
8
7.544
10.0
1.058
.936
25.52
39.35
10
9.430
12.5
1.074
.911
22.80
36.30
12
11.316
15.0
1.090
.890
19.70
32.93
14
13.202
17.5
1.107
.878
16.61
29.63
16
15.088
20.0
1.124
.866
13.67
27.04
18
16.974
22.5
1.142
.854
10.00
23.85
20
18.860
25.0
1.160
.844
4.60
19.43
22
20.746
27.5
1.179
.834
— 1.40
14.70
24
22.632
30.0
1.198
.817
— 8.60
9.96
26
24.518
32.5
1.218
.799
—17.10
5.22
28
26.404
35.0
1.239
.778
—27.00
.65
30
28.290
37.5
1.261
.757
—39.20
8.5" vac.
32
30.176
40.0
1.283
—54.40
15" vac.
34
32.062
42.5
1.306
—39.20
4* vac.
•Kent's M. E. Pocket-Book.
tAm. Sch. of Cor. Dickerman-Boyer.
383
TABLE 61.
Table of Salt Brine Solution.*
(Sodium chloride).
Degrees
Salom-
eter at
60 deg. F.
Percent,
by wt.
of salt
Pounds
of salt
percu. ft.
Specific
gravity
Specific
heat
Freezing
point
deg. P.
Amm.
gage
pressure
0.00
0.000
1.0000
1.000
32.0
47.32
5
1.25
0.785
1.0090
.990
30.3
45.10
10
2.50
1.586
1.0181
.980
28.6
43.03
15
3.75
2.401
1.0271
.970
26.9
41.00
20
5.00
3.239
1.0362
.960
25.2
38.96
25
6.25
4.099
1.0455
.943
23.6
37.19
30
7.50
4.967
1.0547
.926
22.0
35.44
35
8.75
5.834
1.0640
.909
20.4
33.69
40
10.00
6.709
1.0733
.892
18.7
. 31.93
45
11.25
7.622
1.0828
.883
17.1
:0.33
50
12.50
8.542
1.0923
.874
15.5
28.73
55
13.75
9.462
1.1018
.864
13.9
27.24
60
15.00
10.389
1.1114
.855
12.2
25.76
65
16.25
11.384
1.1213
.848
10.7
24.46
70
17.50
12. ,387
1.1312
.842
9.2
23.16
75
18.75
13.396 .
1.1411
.835
7.7
21.82
80
20.00
14.421
1.1511
.829
6.1
20.43
85
21.25
15.461
1.1614
.818
4.6
19.16
90
22.50
16.508
1.1717
.806
3.1
18.20
95
23.75
17.555
1.1820
.795
1.6
16.88
100
25.00
18.610
1.1923
.783
0.0
15.67
TABLE 62.
Horse-Pover Required to Produce One Ton of Refrigeration.!
Condenser pressure and temperature.
P
103
115
127
139
153
168
184
200
218
T
65
70
75
80
85
90
95
100
105
—20°
1.0584
1.1304
1.2051
1.2832
1.3611
1.4427
1.5251
1.6090
1.6910
—15
.9972
1.0G94
1.1450
1.2221
1.3001
1.4101
1.4609
1.5458
1.6300
S 9
—10
.9026
.9777
1.0453
1.1183
1.1926
1.2602
1.3471
1.4352
1.50^3
£13
— 5
.8184
.8833
.95:^7
1.0230
1.0935
1.1679
1.2437
1.3209
1.3961
a 16
.7352
.8008
.8648
.9328
1.0019
1.0718
1.1467
1.2194
1.2.547
»H 20
5
.6665
.7312
.7946
.8593
.9278
.9978
1.0656
1.1381
1.2121
S 24
10
.5915
.6629
.7257
.7894
.8545
.9205
.9911
1.0595
1.1294
* 28
15
.5410
.5998
.6641
.7276
.7924
.8553
.9224
.9943
1.0603
£33
•C 39
20
.4745
.5340
.5923
.6716
.7148
.7796
.8420
.9031
.9736
25
.4103
.4659
.5227
.58(M
.5992
.7022
.7667
.8289
.8922
"S 45
30
.3509
.40.56
.4612
.5178
.5755
.6353
.6944
.7590
.8172
« 51
35
.3005
.3546
.4101
.4666
.5214
.5804
.6398
.7009
.7629
Note.— The above figures are purely theoretical.
50 per cent, must be added.
♦Am. Sch. of Cor. DIckerman-Boyer.
tDe La Vergne Catalog.
Ib practice about
38 4
TABLE 63.
Cubic Feet of Ammonia Ga.s per Minute to Produce One Ton
of Refrigeration per Day.*
Condenser pressure and temperature.
Press.
103
115
127
1.39
153
168
185
200
218
c
a
Press.
Temp.
65°
70°
75°
80°
85°
90°
95°
100°
luJ^
4
—20°
5.84
5.90
5.96
6.03
6.06
6.16
6.23
6.30
6. '3
a. a
6
—15°
5.35
5.40
5.46
5.52
5.58
5.64
5.70
5.77
5. "3
9
—10°
4.66
4.73
4.76
4.81
4.86
4.91
4.97
5.05
5.C3
ft.''
13
— 5°
4.09
4.12
4.17
4.21
4.25
4.30
4.35
4.40
4.44
u Sf
16
0°
3.59
3.63
3.66
3.70
3.74
3.78
3.83
3.87
3.91
o ^
03 0,;
20
5°
3.20
3.24
3.27
3.30
3.34
3.38
3.41
3.45
3.49
24
10°
2.87
2.90
2.93
2.96
2.99
3.02
3.06
3.09
3.12
fe^
28
15°
2.59
2.61
2.65
2.68
2.71
2.73
2.76
2.80
2.82
bp
33
20°
2.. 31
2.34
2.36
2.38
2.41
2.44
2.46
2.49
2.51
<*-(
39
25°
2.06
2.08
2.10
2.12
2.15
2.17
2.20
2.22
2.24
K
4.5
30°
1.85
1.87
1.89
1.91
1.93
1.95
1.97
2.00
2.01
51
35°
1.70
1.72
1.74
1.76
1.77
1.79
1.81
1.83
1.85
TAELE 64.
Table of Refrigerating Capacitles.1
Size of buildine
Number of
CU. ft. per
ton of refrigera-
tion
at temperatures given
Dimen-
sion'! nf
Con-
tents
cu. ft.
Sur-
face
in sq.
ft.
Ratio
cu. ft.
to sq.
ft.
Temperatures
building
0'
8^
16°
24^
32°
40°
48°
5x4x5
100
130
1.3
900
1100
1300
1500
1700
1900
2100
8x10x10
800
520
.65
1800
2200
2600
3000
3400
3800
4200
25x40x10
10000
3300
.33
3600
4400
5200
6000
6700
7600
8400
20x50x20
20000
4800
.24
4860
5940
7020
8100
9180
10260
11340
40x50x20
40000
7600
.19
6300
7700
9100
10500
11900
13300
14700
60x50x20
60000
10400
.17
6840
8360
9880
1140O
12920
14440
15960
80x50x20
80000
13200
.165
7200
8800
10700
12000
13600
15200
168O0
100x50x20
100000
16000
.16
7200
880O
10400
12000
13600
15200
16800
100x100x20
200000
28000
.14
8100
990O
11700
13000
15300
17100
18900
100x100x40
400000
36000
.09
13050
15950
18850
21750
24650
27550
30450
100x100x60
600000
4400O
.073
16200
1980O
23400
27000
30600
34200
37800
100x100x80
800000
52000
.065
18000
22000
26000
30000
34000
38000
4200T
100x100x100
1000000
60000
.06
19350
23650
27950
32250
36550
40850
45150
*Featherstone Foundry and Machine Co. Catalog.
tTayler. P. B. of R.
3S;
it
:3
S
m
e
h
A
Co;
>>-^ '-»
oa S 4»
o «
2'5 w
K S «
3J « t.
— .rr cc
o-
^ <u
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o
OS
a
o o
S j^ - >>
OS 1^ o
o "^ >»
O V
§ St; as 5 5
w 25 ?5 e<3 S
ox c; "M 00
8 S
(M <M C'l G<1 CO
8 8
;5^
8 3 S
8 8 S 8 S 8 8
s
3
8
S
S
8
8
s
8
1^
^
OC
Ci
(M
00
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s
CK
::
:
-
-
:
3
3
-
M ?1 2^1 CO M to CO
8
8
8
g
g
:5
8
8
8
0-5
■^■i
CO
Ti<
'ti
^
Ci
Ci
4J
55
:
z
3
3
3
3
3
:
C-l
<>>
»I
<M
^5
a
^
CC
^
8 8 =
8 8 8 8
-t< O L-J ITS «0 O O 1-1 T-I
EC -5
Si. J
IS
o d
c o
^ o
ns6
Table 66.
Temperatures to Which Ammonia Gas Is Raised by
Compression.'*'
Tempera-
Absolute
Absolute suction pressure
ture of
condensing
suction
pressure
20
25
30
35
40
45
deg. F.
90
199
165
138
116
98
83
110
232
196
166
145
126
109
130.
261
222
193
169
150
132
150
285
246
216
191
171
153
160
296
257
226
202
181
163
5 deg. F.
90
266
172
145
123
104
89
110
239
203
174
151
132
115
130
268
230
200
176
156
139
150
293
254
223
198
178
160
160
305
265
234
209
188
170
10 deg. F.
90
213
178
151
129
110
96
110
247
210
181
158
139
122
130
275
237
207
183
163
145
150
301
262
231
205
185
167
160
313
273
241
216
195
176
15 deg. F.
90
221
185
158
135
117
101
110
254
217
188
164
145
128
130
283
245
214
191
170
152
150
309
269
238
213
192
173
160
321
281
249
223
202
183
20 deg. F.
90
228
192
164
141
123
106
110
262
224
195
171
150
134
130
291
252
222
197
176
158
150
317
277
245
220
198
180
160
329
288
256
230
209
190
25 deg. F.
90
235
199
171
148
129
111
110
269
230
200
178
155
140
130
299
259
229
204
183
165
150
325
284
253
227
205
187
160
338
296
264
237
216
197
30 deg. F.
90
242
206
177
154
134
118
110
277
239
208
184
164
147
130
307
267
236
211
190
171
150
334
292
260
234
•212
193
160
346
304
271
245
223
203
35 deg. F.
90
249
213
182
160
141
124
110
286
246
215
191
170
153
130
315
274
243
217
196
178
150
341
300
268
241
219
200
160
354
312
279
252
230
210
^Tayler. P. B. of R.
387
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r-l
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in
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(N
f-l
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t>.
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1
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d
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s s
t:
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IJAB
IS
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)(IS
388
TABLE 68.
Time Required to Freeze Ice in Cells or Cans, (a) (Slebert).*
Thickness in inches
Temp.
deg. F.
1
2
3
4
5
6
7
8
9
10
11
12
10
0.32
1.28
2.86
5.10
8.00
11.5
15.6
20.4
25.8
31.8
38.5
45.8
12
0.35
1.40
3.15
5.60
8.75
12.6
17.3
22.4
28.4
35.0
42.3
53.4
14
0.39
1.56
3.50
6.22
9.70
14.0
19.0
25.0
31.5
39.0
47.0
56.0
16
0.44
1.75
3.94
7.00
11.00
15.8
21.5
28.0
35.5
43.7
53.0
63.0
18
0.50
2.00
4.50
8.00
12.50
18.0
24.5
32.0
40.5
50.0
60.5
72.0
20
0.58
2..S2
5.25
9.30
14.60
21.0
28.5
37.3
47.2
58.8
70.5
84.0
22
0.70
9.80
6.30
11.20
17.50
25.2
34.3
44.8
56.7
70.0
84.7
If 0.0
24
0.88
3.50
7.86
14.00
21.00
31.5
42.8
56.0
71.0
87.5
106.0
126.0
(a) Time required from one wall, for plate ice, two times the above values.
TABLE 69.
Standard Sizes of Ice Cans.f
Size of
Size of
Size of
Inside
Outside
Size of
cake, in
top,
bottom.
depth.
depth.
band.
pounds
inches
inches
inches
inches
inches
50
8x8
71^x71/^
31
32
y4xiV2
100
8x16
71/4x15^
31
32
1/4x11/2
200
111/2x221/2
101/2x211/2
31
32
1/4x2
300
111/2x221/2
101/2x211/2
44
45
y4x2
400
111/2x221/2
101/2x211/2
57
58
^X2
TABLE 70.
Cold Storage Temperatures for Various Articles.*
Article
Temp.
deg,
F.
32-36
34
40-45
32-40
36-40
40
32-38
34
40
32-34
32-33
40
30-40
45-50
35
34-36
35
39
55
33-35
55
25-30
35
Article
Fruits ._
Temp.
deg.
F.
26-55
35-40
35
35
25-32
25-28
15-28
36-38
30-35
33-40
45
34-45
36-40
35
34
25-28
32
35
40
35
35
34-40
Article
Temp.
deg.
F.
Apples
Asparagus
Bananas
Beans (dried) ..
Berries (fresh)..
Buckwheat
flour .-
Oranges
Oysters
Oysters (in
tubs)
Oysters (in
shells)
Peaches
Pears
Peas (dried) ...
Pork _
Potatoes
Poultry
(frozen)
Poultry (to
freeze)
Sugar, etc.
Syrup
45-50
Fruits (dried)..
Fruits (canned)
Furs (un-
dressed)
Furs (dressed) _
Game (frozen)..
Game (to
freeze)
Grapes
Hams
33-35
25
33
45-55
Butter
34-36
Cabbage
Cantaloupes _..
Celery
40
34
36-40
Cheese _ -
Hops
Chocolate
Honey
28-30
Cider
Lard
Claret
Lemons
Meat (canned) __
Meat (fresh)
Meat (frozen) _.
Milk
18-22
Corn (dried)
Cranberries _ _
40-45
35
Cream
Tobacco
Tomatoes
Vegetables
Watermelons _.
Wheat flour ...
Wines
35
Cucumbers
36
Dates
Nuts
34-40
Eggs
Oat meal
Oil
34
Figs _ _
40
Fish (fresh) _._
Oleomargarine _
Onions
40-45
Fish (dried) _..
Woollens, etc...
25-32
♦Tayler. P. B. of R.
tAs adopted by the Ice Machine Builders' Association of the U. S.
389
r
1
APPENDIX III
391
T( «ta of House Heating: Boilers.
The following extract from a series of tes-ts on a Num-
ber S-48-.7 Ideal Sectional Boiler from the reports of the
American Radiator Company's Institute of Thermal Re-
search, Buffalo, New York, will be of interest.
Size of grate. 48x64*/^ in. Grate area 21.6 sq. ft.
Heating surface— total 3u0.0 sq. ft.
Hard Hard
0— Fuel used in tests Coal Coal
1— No. of boiler _ S-48-7 S-48-7
2— Duration of test hours 8:00 7:00
4— Fuel burned during test, lbs _ 1360.00 1344.00
5— Fuel per hour, lbs. _-_ 170.00 192.00
6— Fuel per sq. ft. grate per hour, lbs 7.90 8.95
7— Stack temperature, degrees Fahrenheit 750.00 725.00
8 — Evaporation per sq. ft. of heating surface
per hour, lbs. 4.97 5.60 6.24
9— Evaporative power available — lbs. of water
per lb. of coal _ __ 8.80 8.75 8.77
10— Boiler-power (evaporation per hour)— lbs.
(item 5 X item 9) 1496.00 1680.00 1562.00
11— Capacity— sq. ft. (item 10 4- 0.22) 6800.00 7640.00 7100.00
12— Capacity— sq. ft. (item 10 -=- 0.25) 5980.00 6720.00 6250.00
Catalog rating _ ._.570O sq. ft.
Hard
Coal
S-48-7
8:00
1434. CO
178.20
8.35
600.00
The accompanying figure shiows the combustion chart
as developed for this same boiler. The tests were run to
find the evaporative power and ca-
pacity with varying amounts of
coal burned per hour. Coal was
fired at regular intervals and the
steam pressure was maintained at
two pounds gage on the radiation.
Line 11 gives the capacity In
square feet of radiation including
m'alns and risers, at the rate of
.22 pound of steam per square
foot per hour. Line 12 gives the
capacity at .25 pound of steam per
square foot per hour. In average
service about one-third of these
quantities of coal would be burned. The catalog rating Is
based upon burning 167.5 pounds of coal per hour and an
evaporation of 8.5 pounds of water per pound of coal (rates
of combustion and evaporation that seem jus>tlfiable). As
A
1600
K 1500
O 1400
5 '303
^«200
2 noo
"» tooo
■J;
° 800
O 7C^
eoo
BOO
X
9
y
^
'Bails
italogu
Rating
/
/
iC
y
/
/
5-48-
7
^
)
\
/
r
/
HARD
100 125 150 175 2
COAL BURNED PER HOUR (POU^
DS]
392
will be seen from lines 5 and 9 the actual amount of coal
burned and the actual evaporation in each test exceed this
figure. Multiplying 167.5 by the assumed evaporative rate
of 8.5 and dividing by .25 = 5700 square feet. Comparing
with column 2, line 5 times line 9 divided by .25 gives 6720
square feet, which is above the catalog rating. Test number
two compared with test number one shows that by in-
creasing the amount of coal from 170 pounds to 192 pounds
per hour increases the boiler capacity 740 square feet.
SVi
Data Required for Elstimatlng: Plain Hot Water or Steam
Plants.
Name © =
of =1.
room 2 =
Size of «
room -S 6C ,
e
X
e
X
Radiators
Steam or water
u
C X
- -S i
^ S C X
? tl 1 1
t, I- — "Z zz
X ,
, Kemarr?:
CoW floor,
ceiling, etc.
"si
•Mil
1 1 !
J
1 1
..................... .
1 1 i
1 1
JJ...'.
_ _,
— »
.,^_
""1
r
'J
1
...
1 1
___
1
—
—
._
1
"1
Date 191._-
Owner of buHding .\adress
Architect .\ddress
Kind of building Location
Nearest freight station
Temperature in living rooms Kind of fuel used
Height of cellar Size of smoke flue x in.
Items to Estimate on.
Boiler and fotmdatioo
Smoke pipe and damper
Thermometers and pressure and safety gages
Draft regulation
Firing tools
Filling and blow-off connection
Pipe and fittings
Sq. ft. of radiation
Cut-off valves and radiator valves
Air valves
Radiator wall shields
Temperature control
Humidifying apparatus
Floor and ceiling plates
Hangers
Expansion tank
Cold air ducts, stack boxes and registers
Pipe covering
Bronzing
Labor of installation
Freight and cartage
Percent, of profit
Total tid
Submitted by
394
INDEX
Absolute pressure, 12
temperature, 12
Absorbers, 300
Absorption system of refrigeration,
294
and compression system compared,
302
system condensers for, 299
system, elevation of, 296
system pumps for, 301
Accelerated systems hot water, 95
Adaptation of district steam to pri-
vate plants, 267
Advantages of vacuum systems, 142
Air, amount to burn carbon, 35
circulation furnace system, 53
circulation within room, 76
composition, 16
duct, fresh, 59
exhausted, actual from nozzle, 188
exhausted per hour plenum system,
170
h. p. in moving, 192
h. p. in moving, table, 186
humidity of, 25
leakage, heat loss by, 43
moisture required by, 30
needed plenum system, 172
per person, table, 24
required as heat carrier, 54
temperature at register, 56
valves, 112
velocities of in convection, 31
velocities, measurement of, 32
velocities, plenum system, table,
172, 184
required, ventilating purposes, 21
washing and humidifying, 167
Ammonia for one-ton refrig., 385
solubility in water, 381
strength of liquor, '381
Anchors, types of, 221
Anemometer, 32
Appendix
table 1 squares, cubes, etc., 328
table 2 trigonometric functions,
334
table 3 equivalents of units, 834
table 4 properties of steam, 335
table 5 Naperian logarithms, 338
table 6 water conversion factors,
338
table 7 volume and wt. of dry air,
339
table 8 weight of pure water, 340
table 9 boiling points of water,
842
table 10 weight of water in air, 342
table 11 relative humidities, 343
table 12 properties of air, 344
table 13 dew points of air, 345
table 14 iuel values Am. coals, 34>'
table 15 cap. of chimneys, 349
table 16 equalization of smoke
flues, 350
table 17 dimensions of reg., 850
tables 18, 20 cap. of fur., 351, 352
table 19 cap. pipes and reg., 851
table 21 area vertical flues, 352
table 22 sheet metal dim., 358
table 23 weight of G. I. pipe, 354
table 24 sp. ht., etc., of substances.
855
tables 25, 26 water pressures, 856
table 27 wrought iron pipes, 357
table 28 expansion of pipes, 358
table 29 tapping list of rad., 358
table 30 pipe equalization, 359
table 31 cap. hot water risers, 360
table 32 cap. steam pipes, 860
table 83 cap. hot water pipes, 861
table 34 cap. hot water mains, 861
tables 35, 36 sizes of steam mains.
362, 863
table 37 friction in pipes, 364
table 38 grav. and vac. returns, 365
table 39 expansion tanks, 365
table 40 sizes of flanged fittings,
366
table 41 pipe fittings, 366
table 42 friction in air pipes, 367
table 43 temp, for testing steam
plants, 370
table 44 spec, for boilers, 371
table 45 heat trans, through pipe
covering, 872
table 46 factors of evap., 373
table 47 heat in feed water, 373
table 48 sizes of Vento heater, 874
table 49 steam used by engines, 375
tables 50, 51, 52 speeds, cap. and
h. p. of various fans, 376,
378
table 53 freezing mixtures, 380
table 54 properties of ammonia,
880
table 55 sol. of ammonia in water,
881
table 56 strength of ammonia
hquor, 881
table 57 prop, of sulphur dioxide.
882
table 58 prop, of carbon dioxide,
382
table 59 boiling pts. of Hquids, 383
table 60 calcium brine sol., 388
table 61 salt brine sol., 384
table 62 horse-power for refrig., 384
;-95
S96
INDEX
table 63 ammonia for one-ton
refrig., 385
table 64 refrigeration caps., 385
table 65 cost of ice making, 386
table 66 temperature of ammonia,
387
table 67 hydrometer scales, 388
table 68 time to freeze ice, 389
table 69 sizes of ice cans, 389
table 70 temp, for cold storage, 389
Application of formula in furnace
heating, 62
of plenum system, 200
Area of ducts, plenum system, 172
of chimney determination of, 35
of grate, 59
Arrangement of Vento heaters, 161
of coils, plenum system, 160
Automatic vacuum system, 149
valves, 149
Basement plans plenum system, 203
Belvac thermoflers, 148
Blowers and fans, speeds of, table,
197
work. Carpenter's rules, 194
Boilers, 251
feed pumps, 249
capacity and number of, 255
radiation supplied by, 252
plant capacity of, 255
steam, 108
tests of, 392
Boihng point of water, table, 342
Boiling points of liquids, 383
Brine cooling system, cap. of, 315
British thermal unit, 10
B. t. u. lost in plenum system, 176
Building materials, conductivities of,
40
Calcium brine solution, 383
Calculating chimney areas, 35
heat loss, 45-46
Calorie, 10
Carbon amount of air to burn, 35
dioxide, 18
dioxide per cent., table, 19
dioxide tests for, ]9
Carpenter's practical rules, 194
Cast radiators, 103
surfaces, plenum system, 161
Centrifugal pumps, 247
Check valve, HI
Chimney area, determination of, 35
Chimneys, 36
capacity of, table, 349
Circulating system for refrigerating,
302
duct in furnace design, 72
water to condense steam, 237
Classification of radiators, 104
Coal, fuel values of, table, 348
Coils, arrangement of in pipe heater,
180
arrangement of Vento in stacks,
182
heat transmission through, 174
heat transmission through Vento,
table, 177
sq. ft. for cooling, 311
surface, plenum system, 173
temp, leaving Vento, table, 180
Cold air system of refrigeration. 284
Combination systems, 110
heaters, 70
Comparison of furnace and other
systems, 51
Composition of air, 16
Compression and absorption system
compared, 302
systems, condensers for, 289
system t)f refrigeration, 280
Condensation, dripping from mains,
267
return to boilers, 133
Condenser, concentric tube. 289
enclosed, 290
for compression systems, 289
submerged, 290
for exhaust steam, 238
heating surface in, 239
Conduction, 14
of building material, table of, 40
Conduits, district heating, 2i2
Convection, 15
Conversion factors for water, 338
Coolers for weak liquor, 301
Cost of heating from central sta-
tion, 258
of ice making, 316, 386
Data for estimate, 394
Data, table for plenum system, 202
Design, hot water and steam, 114
Determination of pipe sizes, 121
Dew point, influence of on refrigera-
tion, 305
Dew points of air, 34.';
Direct radiation, tapping list, table,
358
Dirt strainer, Webster, 147
District heating
adaptation to private plants, 267
amount of radiation supplied by
one horse-power exhaust steam,
237
amount of radiation supplied. 2.^7
amount of radiation supplied by
reheater, 241
application to typical design, 268
boiler feed pumps, 249
boilers, 251
by steam, 264
capacity of boiler plant, 255
centrifugal pumps, 247
circulating pumps, 244
city water supply, 249
classification, 229
condensation from mains. 267
INDEX
397
jonduits, 212
eost of heating, 258
eost, summary of tests, 260
design for consideration, 222
gripping condensation from mains,
267
diameter of mains, 265
sconomizer, 253
exhaust steam available, 223
future increase, 231
general application of design, 268
heat available in exhaust steam,
225
heating by steam, 264
heating surface in reheater, 239
high pressure steam heater, 244
hot water systems, 229
important reheater details, 242
layout for conduit mains, 218
power plant layout, 259
pressure drop in mains, 231, 265
radiation in district, 231
radiation supplied by 1 h. p. of ex.
St., 237
radiation supplied by economizer,
253
radiation supplied per boiler h. p.,
252
references on district heating, 270
regulation, 263
reheater details, 242
reheater for circulating water, 238
reheater tube surface, 241
scope of work, 209
service connections, 235
steam available for heating, 236
systems classified, 229
typical design, 222
velocity of water in mains, 234
water per hour, as heating medium,
230
water to condense one pound of
steam, 237
Division of coils, plenum sys., 162
Ducts, furnace, cold air, 59
plenum system, 165-166
recirculating, 72
Economizers, 253
radiation supplied by, 253
surface, 255
Efficiency of plenum coils, table, 175
Electrical heating, 279
formulas used in, 279
future of, 282
references, 282
Electric pumps, 137
Engine, size of, 197
Equivalents of units, 334
Evaporators for refrig., 292
Exchangers, 301
Exhaust steam available in district
plants, 223
Exhaust steam condenser, 238
Expansion joints, 218
tanks, 113, 365
Exposure heat losses, table, 43
Factors of evaporation, 373
Factor table, velocity and vol., 188
Fans and blowers, 155
drives, 195
housings, 157
power of engine for, 197
size of parts, 195
speed of, 196
Fire places, stoves, etc., 153
Fittings, steam and hot water, IIO,
366
Floor plans for furnace heating,
64-66
Floor plans for plenum sys., 203-205
FormiUas, empirical for radiation,
117
Freezing mixtures, 380
Fresh air duct, 59-71
Fresh air entrance to bldgs., 159
Friction diagrams, 368, 369
in pipes, 364
of air in pipes, 367
Fuel values of Am. coals, table, 348
Furnace,
air circulation within room, 76
foundations, 71
heating, 51
location, 71
selection, 67
Furnace system, air circulation, 53
air required as heat carrier, 54
circulating duct in, 72
design of, 62
essentials of, 52
fan in, 77
fresh air duct in, 71
grate area in, 59
gross register area in, 57
heat stacks, sizes of, 57
heating surface in, 61
leader pipes in, 59, 73
net vent register in, 56
plans for, 64
points •■" be calculated in, 53
registers, temperatures in, 56
stacks or risers in, 74
three methods of installation, 55
vent stacks, 76
Gage pressure, 12
Gallon degree calculation, 315
Gate valve. 111
Generators, 298
Globe valve, 111
Grate area, boilers and heaters, 123
Grate area for furnaces, 59
Greenhouse heating, 118
Gross register area, 51
Hammer, water, 1.S3
398
INDEX
Heat given off by persons, lights,
etc., 49
latent, 13
measurement of, 10
mechanical equivalent of, 13
stacks, sizes of, 57, 74
Heaters, hot water, 108
Heating, district, cost of, 258
Heating surface in coils, plenum sys-
tem, 159
Heating sur., in economizer, 254
in furnace system, 61
in reheater, 239
per h. p. in reheater, 241
Heat loss, 43, 44, 45, 46
calculation of, 45
calculation for refrig., 308
chart, 81
combined, 47
for a 10 room house, table, 63
High pressure heater, 244
High pressure steam trap, 134
Horse-power, in moving air, 192
of engine for fan, 197
required to move air in plenum sys-
tem, 193
Hot air pipes, cap. of, table, 351
water heaters, 106
water pipes, capacity of, table, 361
water radiators, 106
water risers, cap. of, table, 360
water system, 85
water used in indirect coils in ple-
num system, 183
Hot water and steam heating,
accelerated systems, 95
calculation of rad. sur. for, 114
classifications, 87
connection to radiators, 124
determination of pipe sizes, 121
diagrams for, 91
empirical formula for, 117
expansion tank for, 113
for district heating, 229
fittings, no
grate area for heaters, 123
greenhouse radiation, 118
layout, 128
location of radiators for, 124
parts of, 85
pitch of mains for, 124
principles of design of, 114
second classification of, 88
suggestions for operating, 137
temperature, table, 120
Humidity of the air, 25
Humidities, relative, table, 343
Hydrometric scales, 388
Hygrodeik, 27
Hygrometer, 26
Hygrometric chart, 29
Ice making,
capacity, calculation, 314
costs of, 316
Indirect radiators, 88
Insulation of steam pipes, 131. 309
'K' values for pipe colls, table, 174
'K' values for Vento coils, 177
Latent heat, 13
Layout for furnace system, 64
for hot water heating plant, 128
for plenum system, 16:5
of power plant, 259
main and riser, 131
stea-m mains and conduits, 218
Leader pipes, 58
Location of furnaces, 71
of radiators, 124
Low pressure steam traps, 133
Main and riser layout, 131
Mains, cap. of hot water, table, 361
condensation, dripping from, 267
diameter of, 234
pitch of, 124
pressure drop and diam. of, 265
velocity of water in, 234
Manholes, 222
Measurement of air velocities. 32
of heat, 10
of high temperatures, 11
Mechanical equivalent of heat, 13
Mechanical vacuum steam lug. sys..
advantages of, 142
automatic pump for, 144
automatic system, 149
Dunham system, 150
Paul system, 150
principal features of, 143
Van Auken, 148
Webster system, 145
Mechanical warm air heating and
ventilating sys., 153, 169, 184
blowers and fans for, 155
definitions of terms, 169
elements of, 153
exhaust, 154
heat loss and cu. ft. air exhausted,
170
theoretical considerations for, 169
variations in design of, 154
Mills system (attic main), 90, 93
Modulation valve for Webster sys
tern, 147
Moisture, addition of, to air, 30
with air, 25
Naperian logarithms, table, 338
Nitrogen, 17
'n,' values of, 47
Operation of furnaces, 78
of hot water heaters and steam
boilers, 137
suggestions for, 137
Outside temp, for design, 79
Oxygen, 17
INDEX
399
149
of
Packless valves, 112
Paul sys. of mech. vac. heating, 150
typical piping connections for, 150
Pipe coil radiators, 104
capacity of, in sq. ft. of steam
radiation, 360
equalization, table of, 359
for refrigeration, 294
line refrigeration, 306
sizes, determination of, 121
Pipe, leader, 58
Piping connection around heater and
engine, 200
connections for auto. vac. sys.
connections for Paul sys., 151
for heating sys. definitions, 86
system for automatic control
Webster system, 147
Pitot tubes, 33
Plans and speci. for htg. sys., 318
typical specifications, 319
Plenum system, actual amount of
air exhausted in, 188
air needed cu. ft. per hour in, 172
air velocity , table, 186
air velocity theoretical in, 184
air washing and humidifying, 167
amount of steam condensed, 183
application of to school bldgs., 200
approximate rules for, 178
approximate sizes of fan wheels,
table, 195
arrangement of coils in pipe heat-
ers, 180
arrangement of sees, and stacks in
Vento heaters, 182
basement plans for, 203
blower fans, actual h. p. to move
air, 193
Carpenter's rules for, 194
cast surface for, 161
coil surface in, 173
cross sectional area ducts, regis-
ters, etc., 172
data, table, 202
division of coil surface in, 162
double ducts in, 166
dry steam needed in excess of exh.
from engine, 183
efficiency and air temp., table, 175
factors for change of velocity and
volume, table, 188
fan drives for, 195
final air temperature in, 179
floor plans for, 203-205
heating surface in coils of, 173
heating surfaces, 159
h. D. of engine for fan for, 192
h. p. to move air, table, 186
'K,' values of, 174
layout, 163, 164
piping connections around heater
and engine, 200
pressure and velocity, results of
tests of, 189
single duct in, 165
speed of blower fans, table, 197
speed of fans for, 196
temp, of air at register in, 171
temp, of air leaving coils, 180
total B. t. u. transmitted per hr.,
table, 176
use of hot water in indirect coils,
183
values of 'c,' 176
values of 'K,' 174
velocity of air escaping to atmos
phere, table, 187
work done in moving air, 192
Power plant layout, 259
Pressed steel radiators, 103
Pressure, absolute, 12
and velocity, results of tests, 189
gage, 12
in ounces per sq. in., table, 356
water in mains, 231
Principal features of mechanical vac-
uum heating system, 143
Properties of air, table, 344
of ammonia, table, 380
of carbon dioxide, table, 382
of steam, table, 335
of sulphur dioxide, table, 382
Psychometric chart, 345
Pumps, boiler feed, 249
centrifugal, 247
circulating, 244
city water supply, 249
electric, 137
for absorption system, 301
for mech. vac. steam heating, 144
Radiation, 14
amount of, one sq. ft. reheater
tube surface will supply, 241
amt. supplied by economizer, 253
amt. supplied by one h. p., 252
hot water, 106
one lb. exh. steam will supply, 237
supplied by 1 h. p. exh. steam, 237
sur. to heat circulating water, 254
surface to heat feed water, 255
Radiators, amt. of surface on, 108
cast, 103
classification of, 104
columns of, 104
direct, 87
direct-indirect, 87
height of, 106
indirect, 88
location and connection of, 124
pipe coil, 104
pressed steel, 103
sizes, etc., lor ten room house
table, 127
sizes, table of, 108
steam, 106
surface calculation for, 114
sur. effect on trans, of heat, 107
I tapping list. 358
400
INDEX
Recirculating duct, 72
Rectifiers, 298
References,
district heating, 270
electrical heating, 282
furnace heating, 84
heat loss, 50
hot water and steam heating, 139
plenum heating, 206
vacuum heating, 152
ventilation and air supply, 38
refrigeration, 318
Refrigeration,
absorbers, 300
absorption and compression sys-
tems compared, 302
absorption system, 294
absorption system, elevation of,
296
capacity of brine cooled system,
315
capacities, table, 385
circulating system, 302
classification of systems, 283
coils, sq. ft. cooling, 311
cold air system, 284
compression system, 286
condenser, 289
coolers for weak liquor, 301
costs of ice making, 316
evaporators, 292
exchangers, 301
gallon degree calculation, 315
general application, 313
generators, 298
horsepower for, 384
heat loss, 308
ice making cap. calculation, 314
influence of dew point, 305
methods of maintaining low temp.,
303
pipe line, 306
pipes, valves and fittings, 294
pump for absorption system, 301
rectifiers, 298
vacuum system, 284
Register, area of, 56
dimensions of, table, 350
ducts, area of, 172
sizes, net heat, 56
temperature, 56
Regulation, district heating, 261
Sylphon damper, 273
Room temperature, standard, 47
Salt brine solution, 384
Service connections, 235
Sheet metal dimensions, 353
Single duct, plenum system, 165
Sizes of fan wheels, approximate,
table, 195
Sizes of ice cans, 389
Smoke flues, equalization of, 350
Specifications for plans, 319
for boilers, 371
Specific heat, 13
heats, etc., of substances, 355
Speeds of blower fans, 196
Squares, cubes, etc., table, 328
Stacks and risers, 74
Standard room temperature, 47
Steam and hot water fittings, 110
available for heating circulating
water, 237
boilers, 108
condensed per sq. ft. of heating
sur. per hour, plenum sys., 183
dry, needed in excess of engine ex
haust, 183
heater, high pressure, 244
heating, district, 264
loop, 135
mains, diameter of, 265, 362
pipe fittings, 366
pipe insulation, 131
radiators, 106
traps, high pressure, 134
used by engines, 375
Steam system, 85
amt. condensed in plenum sys., 183
classification, 87
diagrams for, 91
parts of, 85
second classification of. 88
Street mains and conduits, layout,
218
Suggestions for operating furnaces.
78
hot water heaters and boilers, 13T
Sylphon damper regulator, 273
Table 1 determination of COj, 21
Tables II, III volume of air per per-
son, 23, 24
Table IV conductivities of materials,
40
Table V exposure losses, 44
Table VI values of t', 48
Table VII values of to, 49
Table VIII heat given off by per
sons, lights, etc., 49
Table IX application to 10 room
res., 63
Table X size and sur. of rads.. 108
Table XI temp, of water in mains,
120
Table XII summary, h. w. htg., 127
Table XIII vel. in plenum sys., 172
Tables XIV-XVII efficiencies, of colls,
175, 177
Tables XVIII-XIX temp, of air on
leaving coils, 179, 180
Tables XX-XXII air pressure and
velocity, 186, 188
Table XXni sizes of fans, 195
Table XXIV speeds of fans, 197
Table XXV data for plenum sys., 202
Table XXVr heat loss from pipes. 217
Table XXVII pressure of water in
mains. 234
INDEX
401
Table XXVIII cal. of conduit mains,
269
Table XXIX transmission through
insulation, 309
Table 1 squares, cubes, etc., 328
Table 2 trigonometric functions, 334
Table 3 equivalents of units, 334
Table 4 properties of steam, 335
Table 5 Naperian logarithms, 338
Table 6 water conversion factors,
338
Table 7 vol. and wt. of dry air, 339
Table 8 weight of pure water, 340
Table 9 boiling points of water, 342
Table 10 wt, of water and air, 342
Table 11 relative humidities, 343
Table 12 properties of air, 344
Table 13 dew points of air, 345
Table 14 fuel value of Am. coals, 348
Table 15 capacities of chimneys, 349
Table 16 equalization of smoke
flues, 350
Table 17 dimensions of registers, 350
Tables 18, 20 cap. of fur., 351, 352
Table 19 cap. of pipes and reg., 351
Table 21 area of vertical flues, 352
Table 22 sheet metal dimensions, 353
Table 23 weight of G. I. pipe, 354
Table 24 sp. ht., etc., of substances,
355
Tables 25, 26 water pressures, 356
Table 27 wrought iron pipes, 357
Table 28 expansion of pipes, 358
Table 29 tapping list of rad., 358
Table 30 pipe equalization, 359
Table 31 cap. of hot water risers, 360
Table 32 cap. of steam pipes, 860
Table 33 cap. of hot water pipes, 361
Table 34 cap. of hot water mains, 361
Tables 35, 36 sizes of steam mains, 362
Table 37 friction in pipes, 364
Table 38 grav, and vac. returns, 365
Table 39 expansion tanks, 365
Table 40 sizes of flanged fittings, 366
Table 41 dimensions of pipe fittings,
366
Table 42 friction in air pipes, 367
Table 43 temp, for testing plants,
370
Table 44 spec, for boilers, 371
Table 45 heat trans, through pipe
covering, 372
Table 46 factors of evaporation, 373
Table 47 heat in feed water, 373
Table 48 sizes of Vento heaters, 374
Table 49 steam used by engines, 375
Tables 50, 51, 52 speeds, cap., h. p.
of various fans, 376-378
Table 53 freezing mixtures, 380
Table 54 properties of ammonia, 380
Table 55 sol. of ammonia in water,
381
Table 56 strength of ammonia
liquor, 381
Table 57 properties of sulphur diox
ide, 382
Table 58 properties of carbon diox-
ide, 382
Table 59 boiling points of liquids, 383
Table 60 calcium brine solution, 383
Table 61 salt brine solution, 384
Table 62 horse-power for refrig., 3S4
Table 63 ammonia for one-ton re-
frig., 385
Table 64 refrigeration caps., 385
Table 65 cost of ice making, 386
Table 66 temperature of ammonia,
387
Table 67 hydrometer scales, 388
Table 68 time to freeze ice, 389
Table 69 sizes of ice cans, 389
Table 70 temp, for cold storage, 38'J
Tanks, expansion, 113, 365
Temperature absolute, 12
best for design, 79
chart, 81
Temp, control in heating sys., 271
Andrews system, 272
important points in, 275
in large plants, 274
Johnson system, 276
National system, 278
Powers system, 277
principle of system, 271
special designs of, 275
Sylphon damper control, 273
thermostat, 272
of air entering plenum system, 17 1
of air in greenhouses, table, 120
of air leaving coils in plenum sys
tem, 179
of ammonia, 387
for cold storage, 389
for testing plants, 370
measurement of high, 11
methods of obtaining low, 303
room standard, 47
Thermofiers, Belvac, 148
Thermostat, 272
thermostatic valve, 146
Time to freeze ice, 389
Traps, high pressure steam, 134
low pressure steam, 133
Trigonorqetric functions, 334
Under-feed furnaces, 69
Use of hot water in indirect coils, 183
Vacuum systems, 99
and gravity returns, 365
of refrigeration, 284
Values of 'c,' 176
of 'k,' 177
of 'n,' 47
of 't,' 48, 49
Valves, air, 112
automatic vacuum, 149
modulation valve, 147
4o:
INDEX
thermostatic, 146
types of, 111
Velocity of air by application heat,
31
of air escaping to atmosphere, 187
Vent registers (net), 57
stacks, 58
Ventilation heat loss, 44
air required per person, 21
Vento coils, values of 'k' for, 177
Vento heater sizes, 374
Vertical hot air flues, table, 352
Volume and wt. of dry air, table, 339
Warm air fur., cap. of, table, 351
air heating cap., 352
Washing and humidifying of air, 167
Water, conversion factors, table, 33fc
hammer, 133
needed per hour in dist. htg., 230
pressure in mains, 231
pressure, table of, 234
seal motor, Webster, 145
weight of column corresponding to
air pressure in ozs., S56
weight of pure, table, 340
weight of water and air, table, 342
Webster system of vac. heating, 145
Weight of pure water, 340
Weight of G. I. pipe, 354
of water and air, table, 342
Work done in moving air, 192
Wrought iron and steel pipes, table,
357
expansion of, table, 358
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