Document 6RY82ebejMjr36Zr4rpq8K9Lo

American Society of Heating and Ventilating Engineers Guide, 1931 which usually is much higher than the relative humidity occurring at the maximum temperature. Any statement of weather condition which gives a wet-bulb temperature higher than 80 deg. in the United States is questionable. WIND MOVEMENT The effect of wind on the heating requirements of any building should be given consideration under two heads: 1. Wind movement increases the heat transmission of walls, glass, and roof, affecting poor walls to a much greater extent than good walls. 2. Wind movement materially increases the infiltration (inleakage) of cold air through the cracks around doors and windows, and even through the building materials them selves, if such materials are at all porous. It is entirely possible that a building may require more heat on a windy day with a moderately low outside temperature than on a quiet day with a much lower outside temperature. It will, therefore, be evident that the wind movement in any locality must be given careful consideration in computing the probable heating requirements of a building, and for the purposes of calculation, not less than the average wind movement in any locality during December, January and February should always be pro vided for in computing (1) the heat transmission of a building, and (2) the heat required to take care of the infiltration of outside air. The first condition is readily taken care of, as explained in Chapter 3, by using a surface coefficient f0 for the outside wall surface, which is based on the proper wind velocity. In case specific data are lacking for any given locality, it is sufficiently accurate to use an average wind velocity of approximately 15 mph which is the velocity upon which the heat transmission coefficient tables in Chapter 3, are based. In a similar manner, the heat allowance for infiltration through cracks and walls (Tables 1 and 2, Chapter 4) must be based on the proper wind velocity for a given locality, although not necessarily the average wind velocity, as explained on p. 75, Chapter 4. Wind movement involves both direction and velocity, and hence after transmission and infiltration losses have been computed, using coefficients which allow for the proper velocity, a further allowance must be made for the direction of the prevailing wind in any given locality. This shall be done by adding 15 per cent to the wall and glass transmission losses and the infiltration Josses on the sides of the building exposed to the prevailing winds. Those walls which lie in the two adjacent sides of the building most nearly facing the prevailing wind are to be considered in making this correction. (See Fig. 8, Chapter 4). This is not necessarily the same as adding 15 per cent to the total heat loss of a room on the exposed sides of the building. HEAT SOURCES Heat Available from Sources other than Heating Plant The heat supplied by persons, lights, motors and machinery should always be ascertained in the case of theaters, assembly halls, and in dustrial plants, but allowances for such heat sources must be made only 88 Chapter 5--Heat Loss Calculations Table 4. Heat Given Up by Persons and Lights Persons: Man at rest-----Man at work-- 400 B.t.u. per hr. 500 B.t.u. per hr. Lights: Electric lamps, B.t.u. per hr. equals watts per lamp X number of lamps X 3.415 Gas lighting: 1 cu. ft. producer gas--.... -......... --------- -----------------------------1 cu. ft. illuminating gas----------------------------------------------------1 cu. ft. natural gas...... ................------ ---------------------------------- A WelSBACH BURNER AVERAGES 3 CU. FT. OF GAS PER BOUR AND A FISH TAIL. BURNER 5 CU. FT. PER HOUR. .. 150 B.t.u. .. 700 B.t.u. ..1,000 B.t.u. Table 5 Heat Emitted by Persons per Hour at Different Room TEMPERATUREsa H = Heat emitted by man at rest per hour. HI = Heat emitted by man at light labor per hour. Ha = Heat emitted by man at average labor per hour. Hh = Heat emitted by man at hard labor per hour. ,, /Foot-Pounds per hour\ . 1co D t , HE = Heat Energy = (---------------?78 -----------) = 84 B-t-u- 168 Btu- and 252 B.t.u. respectively for light, average and hard labor. / = Room Temperature. H = 13.2 (98.6 -- /) t X HE Heat due labor = - t V" HE HI, Ha, or Hh = 13.2 (98.6 -- t) + Rook Temp. Deo. FtHR. 30 40 50 60 68.. 70 75 80 85 90 Rest 905 773 642 509 404 378 312 246 180 114 Heat Emitted bt Man* B.t.d. per Hour at 84 ' 168 B.Lu. 252 B.tu. Light Average Hard Labor . Labor Labor 931 954 981 807 838 874 684 723 768 559 606 660 461 518 575 436 491 554 375 438 501 313 375 447 251 322 394 189 259 342 Condition Required' Excess and Shortage IN HEAT TCmumtaw Increasing Humidity. Heavy Clothing for Reduction or Preven- tion of Radiation. Normal Condition. Decreasing Humidity. Air Currents for Producing Evaporation of Perspiration. For children use one-half of table values. after careful consideration of all local conditions. In many cases, these heat sources should not be allowed to affect the size of the installation at all, although they may have a marked effect on the operation and con trol of the system later. In general, it is safe to say that where audiences are involved, the heating installation must have sufficient capacity to bring the building up to the stipulated inside temperature before the audience arrives. In industrial plants, quite a different condition exists, and heat sources, if they are always available during the period of human 89 ( /