Document Ed1N0NkYyM4M4X3ap0qNVOVGN

HEATINC VENTILATING AIR CONDITIONING GUIDE 1944 Fig. 1. Design T emperature Zone M ap ' f ' . ' r 134 ............... ' S CHAPTER 6. HEATING LOAD temperature may be calculated in the usual manner by means of Equa tion 4, allowing the full value of the roof. The error resulting from this assumption will generally be considerably less than if the roof were neglected (as is sometimes the practice) and the attic temperature as sumed to be the same as the outside temperature. TEMPERATURES IN UNHEATED SPACES The heat loss from heated rooms into unheated rooms or spaces must be based on the estimated or assumed temperature in such, unheated spaces. This temperature will generally range between the inside and outside temperatures, depending on the relative areas of the surfaces adjacent to the heated room and exposed to the outside. If the respective surface areas adjacent to the heated room and exposed to the outside are approximately the same-, and if the coefficients of transmission are approximately equal, the temperature in the unheated space may be assumed to be the mean of the inside and outside design temperatures. If, however, the surface areas and coefficients are unequal, the tempera ture in the unheated space should be estimated by means of Equation 5. t{A\U\ 4- AtUt 4- AjUt 4- etc.) Ip Q4af7a 4- AbUb 4- AcUc 4- etc.) /u = A\U\ 4- AtUt AtUi T etc. 4- AaUa 4* AbUb 4- AcUc 4- etc. (5) where <u = temperature in unheated space, degrees Fahrenheit. t -- inside design temperature of heated room, degrees Fahrenheit. t0 = outside design temperature, degrees Fahrenheit. At, At, At, etc. = areas of surface of unheated space adjacent to heated space, square feet. Aa, Ab, Ac, etc. = areas of surface of unheated space exposed to outside, square feet. Ui, Ut, Ut, etc. = coefficients of transmission of surfaces of At, At, At, etc. Ua, Ub, f/c, etc. = coefficients of transmission of surfaces A&, Ab, Ac, etc. Example'4. Calculate the temperature in an unheated space adjacent to a heated room having surface areas (j4i, At, and At) in contact therewith of 100, 120 and 140 sq ft and coefficients (Ut, Ut, and Vi) of 0.15, 0.20 and 0.25 respectively. The surface areas of the unheated space exposed to the outside (Aa and A b) are respectively 100 and 140 sq ft and the corresponding coefficients are 0.10 and 0.30. The sixth surface is on the ground and is neglected in this example/ Assume t = 70 and t0 = --10. - Solution. Substituting in Equation 5: 70[(100 X0.15)4-(120 X 0.20)4-(140 X0.25)]4--10[(100 X0.10)4-(140XO-30)1 tu = (100 X 0.15) 4- (120 X 0.20) 4- (140 X 0.25) 4- (100 X 0.10) 4- (140 X 0.30) In -- 4660 126 = 37 F. The temperature in unheated spaces having large glass areas and with two or more surfaces exposed to the outside (such as sleeping porches and sun parlors), are generally assumed to be the same as the outside tem perature. GROUND TEMPERATURES Ground temperatures to be assumed for estimating basement heat losses will usually differ in the case of basement walls and floors, the 135