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.

i i « I" 1 lilL r \ i = 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 it ftti 1— I i^ si -d fit. s o 0X3 « a u o o « Bo ft o ft o o Xi o m P ft o ft ^ O 4) I-H fta ?1 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 6 B a o C5 ^ 8 6 en O g -J o g g o o o O S b en o s \v \kJ 1 ,111 -/NAr^StP o CO s o ^^ >n4 s^ K^. .>i V - PBflTOTi 1 ,) V^, s i^^i^ft IT v.-^ L,U. ,.. orXdz cqitotai y ^V?^^!^ iv »^ ^^)X^ it ^ 'Vfs. A\ ?4 1 " r- V t2 s> V ^'- N, ^^, uj -STQ^^o: :<^^^ % f 32OTEj.0WT0"~P<, h^^. r ^ ^ -? ^ 1 \^^ s; ^'^ ■o m ?" V ^ -- "^ r N 33 C / ^( \ \ 3! V \: i. \ N dir J^ . _ fir- . s-^i \ \ Sll^ BELOW TO \ \ \ r" t 3 - n 7 ,11 ^ k S^ ) T3 \ N 1 ^ :s ^3 33 > - ' \ \ ^ = - > o \ _ _ , "-JSretLOw- U' rui/l >'" / t= 1 1 ,/ 1 / / 1 / , y I . -. J _ _ / ^ •15'BEiilWl ■a^XTQTAL 0- / / / \ 1 / / { y; ^ / / / y' / V /'' \ ^ / > / H Lj l^ -U -d. k,^ / \ }4 UtLO^ "l )(k\ ,> 1 V 1 ; ^b /^ /* \.. t5> 4?^' Pv(;'^' ,,-' r^ AXy" 1/ ■oi 10- ■ ,/ b'^ / 'A 5J dOlJLLUW /i 7 ^ ^ ■" /. / i/ \ ^^ ^ y 1 / ^ i_ _ _j L \A cJ J L i J 1 _ PI o m I PI 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 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: — 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.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/ 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, = 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 lQ' -\% hf (71) where d, hf,

= == 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 >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 radIatIos 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,

= 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 locaasses 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 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 ^ooooo^ ^pooooo I ..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] (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<-^M]COCOCO-^-^-^-^tOlOlO>niOI i-lOCO'*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-(cl>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 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^ 1 1 'I / ■-N ^ 1 K/l hJn //y/i/ /" "N "k ^H ■P (7 /M 7 Wi / > ft*, \ ^' ^m W/V m, H ^-^ \ \ NY N Urn /m / ' "v. \ •o^ n / W r \ H ^ Y Q] Vy / , \ \ \ ^ ■^ 4v,v/A/^ r \ \ . /m mm 1 \ ^ ;^\ y s TmNmn ILJjMJ ■ \ k ■^ \ ^(/X/ yjmm '>} \, N, \ 1 V mm rt ' s^ \\ // rIv\Nri 'ij ^ \ I •4 ^ 1 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 •= ? ^ § ^ > 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 -rHlf3QLn©OOOOl ■rt00r-l OCC(M-«*05(MOO^OlOC<00.a5-^r-i05i>»'»iteoc. Ttl cq r-( I^ r-l ooooinirtoot-icot^mt^oiooi^o-'^'oot^'-iooosooooo lOt^coioco-^cot^-^-^-^r^-^-^meo-^i^c^ioo-*!— iC5t^mcocOrtte<5e^cJ(M(MC*02c«3ir:oo Oi— ii-HCOLOoo-^Ocor^csoo l^C0r-llrtC0C0i-l00t^C^COi-l«O'«J< 1-1 i-c rH 1-1 (>J (M 3q ooooo ■!^ooi-i-* i-ir-ii-(i-(r-i(Mi>)(Mcoeoc<5' (M t- O O C5 ' irHOC0-^Ol.0->*3(MCOe0 05C<5eoeO30'i<<©(MOOCOr-l^ _. ___ 5OOOOC5C1000CJ'*lO«Ot^OO iHr-lr-lCq0je«5C<5'»»<-»»Oi-IC. 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. Q i-H iH ©» CO -* «5 «0 00 •^ rHrHi-liHlH pHl-t'"' 09 .. ..... ..* Ci|pH,_l ,_|r-(iHi-li-l rHiH<>^ CM r-I r-I r-i r-i r-I iH r-J I-H W W ^^ in iH«eo-*i^ i>ooOi-|eo "^cooo *^ p4p.5rHr-HT-H i- Ci r-^ «^i-5 r-^I-^^-^^HI-^ rHcic^ioclcvJ cicico pjiHoi CO \ei <£> cci Oi i-ieo-e»iot-o tO«D0O *^ iHi-li-liHi-H i-((?i(MWW eoeOCOCO-^ •'^■^Tjl 0»r-l e4-*«O00oM ^"r-lr-( rHiHi-IC*C4 WcicoeOCO «iO->*-*Tj(lA ICtOtO j^04eOiC COOlrH-^O OSiHiAOOiH iO00C4mrH lAos-* »~rHi-Hi-i 1-i r-i a ot a * -^ -^ m va (£> tt>«ol> SJiOlAt- OC4-*air-l -^OrHMft^ i-Ht>0-*r-l COOJ«D r-tHiHrHi-t CX> r-{ eOCDOOeJlO OeoOOWt- pHlrtrHtO-* 05MO l-HrHl-HrHC* C4C*©ieOC0 TjIrii-dHldlO COc6l>l>o6 OOoi . -^OOlfi^SiC COrH-^OOCii t-THt^C tHOiOtHO i-Ii-HC* •— ' iHi-ti-lr-t rHi-liH(MC4 C4C0C0eo-<*< •>* «t-rH«oeo t-r-ioooo oeoOr-i(i4 coeo-* i-Hr-iiHr-ll-li-H i-HOjWOiC* COeOTHMfU^ mtOCOt-OO 00O5 <0 iH u^ O b- -* 05 lO 00 iH OS O r-t (M CO ■* CO O 00 • • • J • i-H i-H iH iH i-H rH ?-( r-t cjciwcoco ^-^irtino e£> t~ 00 Oi Oi ■* *~'-'r-l'~' Ciciwco ^ffi'OQO . eo oj ■* oi lo cv8t>c;8OOOOOl eoNOoOiO rHeieo-*© t-eo3irHM m©© .• •••I-H l-Hi-ti-lrHr-l l-liHi-HC ® l> b- 00 •*coo«eo "^iflit-osp e»Mifti>o s^eot- ••iHr-li-( l-lrHrHiHN Cvi(Mc4(NC0 COMCO 00 Oi O CO •* «D t- Oi r-l 5^ '^ 50 O (?» u:> t> Q M m 04 i-Hi-lrHiHr-l i-tfrj(?5(>5c* COCOCOCO^ •>ai'«H-«*i ^ CO (D OS to 00 *" r-l rH iH C4 CvJ eo t- o lo o «D rH iH e t^ l-lrHci coeo'-^iftO U>rH00OlCOOs i-Hfi^c^eo -^iftcooooj eo N eo t- O O 1 iH w' CO ■* VO b^ oi ' N 00 eo O b; eo CO ■>*< ift o C4 OS t^ iC •* -.^ Mf lo eo b- i> «o t- 00 OS in CO l> 00 OS OS CJ C) iJ4 ■* • • I-H rH iH t> OS I eo eo eo ■* •* i?5 1 _^oo ooiHb-coos oicooscot- eot^coOs© r-'i-''>00t: QDi-iOstht-h oq rv^ Si g> C» ^ lHiHMCQO»COCOTtl>OOOSOlN6i-*lOtt500flSr-H5J-»tl rHei-<» © CO t- CO CO CO •* ■* ■* - COeo«C4CO MOQtffiC^ dOOOSiOM IftOpOeOCO Of-lO • iHWeo-'l'Ln b-0005jiO OOOCOb-r-l MfCsCOOS-* ot-oi 5 l-lr-r-ll-(C5c Wi-ieot-co «oi>in*in inomoo inaoocoo «r-(^inin inin va .r-lCOin OOOlOO-^r-l OQrHCOi^ ^OS{~0Qb- OOlQC^Oi? ciC0O-*K i-HfOint^t COCO IQ t-l r-lCSl CO -^inCOt-OO Oi-HCOiof- OSOjlOOOO • t a « a) it U 03 ■** fcH iti m 4* m «> P. o » «M +3 4> O 03 ft C! O §^ > •l^A 0«0»«»OQQQt-QQOOOOQQ x>iau3 lo SSS§S5?S5SSS^8feS|gg dojp •zo •dojp •zo r-(i-ISS!MSO-^«DX— l-^t- 0» ■<*< 06 ui ■* CO Oi 3 «D QO P lO 06 t-— I w o w « I— I — ( » -v » •U^p-BJ •W'bs •do.ip •zo •dcip ^2^-^ •zo cq3 x: 2 s- •^jfN5« NEJ Ntl NE« ^;L,^5^a^80w*'<»<»o«it-xo»os^'*' w 0) -o § S H 03 - lO i-l r-l (N 00 •* t- rtOO^OSOQOX i-H I— l(M « Tp t» t-!M^t-0(M>-ie050'?^'-i -H i-l(N CO lO 00 • • . • S^ 00 lO CO 0<» 1^3 to CCOOOOiCOt-i-Hi— I5qc0-*»00 i-H s^ o*i5^O':0Q0b» lO --H Oi 00 05 •«*• o lOeCCO'OIN-H'-liN(MJO'*Ot- 1-1 (M CO Tji <0 O I— ( ^C0b»i-H0<)a0iO«O5<|lO»Tf<«O «500(N5^Ttirt^ b-®«oQoor-(r-(aqeO'*iot-QO i-H (M CO <5 <0 i-H 1-1 (Dfloioeeoioooocoot-oo-* 00 O O X i-t O U3 Oi»i— (?D«DU:ir-t(NCO-^?O00O5 l-H (M<»QOS— I I— I to ot-oo-*iio OS ■<*< i-l F-l «DO(N0001^0«0 1— I i-l 0)U3 . • • t- OS CO 1—1 1—1 OS "—I OS-*t-tTj''^» COiOt-OWfM f-( i-H I— I I-l 1—1 (M i-lC0i-t0S<0'*Q0O«0«ot«oooso>-HiMco w Eh 1^ 8 ooeo-«*<(Ni-< > 5D Id O U5 O OS ua I > (>) OS Q o -^ ©^ u5 e > t- 00 O 1— : CO »0 OS I coo -^ ^ ^ . , . _ _ «ot-os) CO lO O d CO t- 5.b-OSTj5t-05<— iCO«O00i— iTft-iOlO 1— ii-i^i-idqiNtMCO'* COCO^^^OOOSOlO t-lOOOlO^OSi— I© lOs^Qiao^i— it-ift CO«D03^00S-*CO«0 1— lrH^SG)lOQpOS00Q0lC 50t-^HC0OiO-Oi-<(MOSCOQO I— I lO O O ^^ OS CO "^ o t-s05Q0'-i saqouT TjUC^Dt-OOOSOC^-* 1— ii— ii— ii— irHi— la^s^^ci 36:? 03 d si li 0) 0) +f +» 3 • S fl 4^ ys Bi "^ Jr. Cm d S ^ ^ ^ eo •♦* H "E ^ ° M iJ Is. jg oi k» ,fi d tf H •a ii!^ it 55 •*» bo «M ^ fl e 8 5 »i9 B d o w o I?; GO to 10 CO CM >— I a0"— 1 00 5^1 00 -^ 3 ^ G 1 CO ■«»< «D X » ■-> pBaq JO 6SOT §?< )00li5 0«0«i , J 35 t- t- -^ S-J cc I© t« f-^ a>— » ■* lOt- jad i^aaj OTqno (N03 tO«Ot^O» loaj III p^aq JO ssot; r-^0<» •* «00 ^ a^nuTtu .lad ^aaj ojqno (^aaj uT p^aq JO SBOT^ l-HrHi-IN « X 3^ ft S^ X »< ■o^i lox -H S^ 0OU3 « t-0» 05 lOO t--H ■v —^ •»»• 1— ( i-H :r ■-( •-^5^-'J<«X • 5<»X ■'•'QeOCI ^ ^^ CO t-uSOOtOt- «iooo — oc t-?pooo« •<»< Q ■-< t- 1- ; fHCO lOt-O ■ X 5^ o ^ lO o: S^ < CO M ■* O»Oib-i-l06 „ ® -"T-XX rico riOOioXfNO > XT »*- «V ^"-^ ^ i-(i-iN(>)( oioxs^eo— * ■— I ■^ 50 o •^ OS >axxt-t- ' 1-H 10 » 7t t~- i-H r-H 1-1 a^ m -H -<»< 'J- S^ «C t- 'O a<) ■<>< t- i-H UJ o — l-Hl-li-lS^ I ■<»< X ?< l» *< 3 1— I i-M t— 1 1— ( '^ ■«»«•<* CO b-0<10 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 ^„ 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 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 rH ;f3 CO t^ O 00 CO CO ■»}( CO t> © o (M . . . t^ CO 00 I t-KtH I c c I ! i i ! i I ' • I g (-1 I a < o o a> CS CS 03 C3 a c;'t) •4-1 « .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 ^ T3 e at I e X fl e -a 2 •a adid q9nt-dno ni ^uaiBAinba )dd^ djenbs n{ dOBds JIB 53X eoBjjus ani^Ben JO )dd} ajBnbs "adjd qoa{-auo )3d} iBdni[ ui ^udiBAinb^ UI aoBds JIB 59NJ dOBjjns Sn;:^Bdq jo )3dj dJBnbs adid qoui-auo '%33l iBanji uj ^uaiBAinbj ;aaj"ajBnbs ni dOBds JIB 5a>c dOBjjns Sn!)Bdi{ JO laaj ajBnbg 9did qoai-auo ^aaj iBauii u{ luaiBAinba ^aaj ^Birbs" n{ dOBds JIB lax r- r- (M C<5 'J' LI « i^ 00 o c ^ o) ^ ^ — — <>) e-1 N oooooocooco »>^ 00 tt o — M M -^ o «' r^ i^ as S — (N M -r ir^ «; 1- 00 o e o c c c c oc" a d -^ (m" c^" xi^ c; C j .— ®t-OOOSO — 1- C^ CO •<»• l- co^-oo 050 — '"■''""' oe c o o c; o o o o © o o c c o c c N 00 •* o o r-l04 -^ IS 1- •M00'>»'O50!M0C-«»' CJCCM-^u-r-ooccvicoi.'iSoo ^C«>•v■^ r-5 IS !M C C: J~ CJ ■^ 1^ c; c^ iS u; 12 L3 ® ;o •^ S ■^ — OO l-l ^ -^ i-T o I- « c; c; o — «'^-»'>« 3 c " « 1^ «QQ SQ O 4) o « n lOtocot^XCiCso — (>4coco-*iacc:£t^Xj "St, o3^ £ 08 « = = ?;-S 'x: 03 S o3i: 3 - *» c - jaTJ Q S O 2 ® bfl ,— « , gj o '-^ »-■ a to T3 ■? 03 C ^ boS c-« o fcic a « „ ■<-> U QQ r< '^ » a o*j cj >-— -^ « c .^ a g O 83 3 5 « k^ .-3 u t: » « •5 « a:S . 1 5 0.6-^ « c-^S • *; .'^ - G ffl c; ♦J s O 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 >-^ '-» oa S 4» o « 2'5 w K S « 3J « t. — .rr cc o- ^ > OS 1^ o o "^ >» O V § St; as 5 5 w 25 ?5 e<3 S ox c; "M 00 8 S (M > »I • 1 1 1 H«. r-l d 00 rH '^ (M in "^ ] •>«< 8 ?5 o s g i-t t-H d 1 1 1 1- r-l d rH •-: (M 1^ in 1 1 o> ^ in "s~ in (N f-l ■^ 1 I-^ CO t>. r-^ # lO as cq lO CO 1 eo CO d es rH rH rH d CO (M OJ CO ! 1 ^. CO s s t: 5r rH CO T-i s 1 1 CO rH d "i m ' r-l >* o O I-H 00 ^ o 8 S IS s^ la in d ■H< ■M 18 rH ■^ 00 to ■Xt •>*< O) IM in CO ~j -v T-i rH « 1^ fi r-l (N eo OJ 1^ CO rH •^ o 4) O ?S CO d CO •

  • x: 00 •a 3 o- 15 in t-i e n 1 in a ca M a> ■4J o rH + O W 3 « n 3 3 S] pq on V bo Sn in i-i o ■»-> a 8 a CO 'CM in 2 rH ^^ M • 1 to "3 t 1 8 1 o rH d in 1 IM r-< t. 1 a ca x: bo c ■h (h s rH 1 1 8 r- 1 OS 1 t C a rH a x: n 2 3 a it ' t C a rH 1 o ^1 Ho O) en 6o i4 «* s^ bo CO CO 1 _3 3 03 «^ fi-H CO £ (O 3 Cii o09) oS'SI ■a o b(i Ol Ol ^ 2 bo <5 ossv 'lua MO •s -n 1^ o 00 as ^ IJAB IS OBiOi )(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 L_ //• •^•• y-^/ •v.. ^\r-.'. M :l s^a ■TRF^