Document wZRjgv3M2jg3m9gxa9kg8MKB

Heating Ventilating Air Conditioning Guide 1939 Fig. 3. Plan Diagram of Clothing Store Solution: The normal heat transmission through various surfaces shown in load calculations are determined by application of Formula 1. It is quite obvious from the shape and exposure of this store that the maximum sun load will exist on the west wall. Since the west wall has a large glass area with a negligible time lag, the peak load may be expected at 4:00 p.m. at which time, from Table 4, I = 211. I for the south side at 4:00 p.m. is 8. Because of the small amount of solar radiation transmitted through the south glass, it can be neglected and the total heat gain taken as that due to normal transmission. Assuming time lag in roof and walls to be 2 hours, the corresponding values for / for south and west walls and roof will be those shown in Table 4 for 2:00 p.m. They are respectively 77, 143 and 258. A time lag of 1 hour was assumed for the west door amounting to / = 192. By substituting these values in equations 2 and 3 the solar heat load is determined. To determine the heat gain from the outside air it is necessary first to determine the volume of the outside air to be introduced. Since the show windows are sealed |o as not to permit infiltration and since there are only three doors in this store throughswhich infiltration can take place, it is obvious that infiltration of air will be a negligible qUan-> tity. The volume of the store is 21,600 cu ft. Good practice indicates that in a store of this character there should be a minimum of from 1 to 1H outside air changes per hour. On a basis of 1J4 air changes the volume of outside air to be introduced would be 32,400 cfh. By reference to Chapter 3 it will be noted that the minimum ventilation require ments are 10 cfm per person. On this basis the ventilation requirements would be 30,000 cfh. Since this will produce approximately 1H outside air changes per hour, 30,000 cfh will be considered in this application. To determine load imposed by occupants it will be found from Table 4, Chapter 3 that the average person standing at rest will dissipate 225 Btu sensible heat and 206 Btu latent heat per hour. Normal Transmission Load: Sobtacb S Glass S Wall W Wall W Door Roof Floor N Partition Total Dimensions 2(2 ft 6 in. x 7 ft) + 2(10 ft x 6 ft) (30 ft x 12 ft)-155 (60 ft x 12 ft)-321 3 ft x 7 ft 60 ft x 30 ft 26 ft x 54 ft 30 ft x 12 ft Abba so n 155 205 399 21 1800 1404 360 v"' 1.13 0.33 0.33 0.51 0.26 0.34 0.34 Temp. Dip?. Deg F 15 15 15 15 15 5 8 Btu peb Houb 2.627 1,015 1.975 161 7,0202.387 979 16,164 Cooling Load 3(14 ft x 6 ft) 4(8 ft x 6 ft) Arba SQ FT 205 300 21 399 1800 P 0.078 0.118 0.078 0.062 a 0.7 0.7 0.7 0.9 / 77 211 192 143 258 Shade Factob 0.28 Btu peb Houb 862 17,724 333 3,113 25,914 47,946 Outside Air Heat Gain: Sensible heat, Hs = 0.24 X 60 do Q (to -- f) (Formula 4). QDe=ns5it0y oXf a1i0r a=t 9550F0 dcfrmy-.bulb and 75 F wet-bulb for a barometric pressure of 29.92 in. is 0.07105 lb per cubic foot (Table 4, Chapter 1). Dew-point of outdoor air is 66 F (psychrometric chart). Partial pressure of vapor is 0.64378 in. Hg. (Pressure of saturated vapor at 66 F, (Table 6, Chapter 1). W = 0.622 (3-^7) = 0.622 = 00137 lb water vapor per pound dry air (Formula 5 a. Chapter 1). --;--1-- = = 0.986 lb dry air per pound outside air. 1 plus 0.0137 do = 0.07105 X 0.986 = 0.0699 lb dry air per cubic foot outside air. H, = 60 X 500 X 0.0699 X 0.24 (95-80) = 7549 Btu per hour. Total heat, H -- 60 do Q (ho -- h) (Formula 5). ho = 38.46 Btu per pound dry air at 75 F wet-bulb (Table 6, Chapter 1). h - 31.51 Btu per pound dry air at 67 F wet-bulb (Table 6, Chapter 1). H = 60 X 0.0699 X 500 (38.46 - 31.51) = 14,574 Btu per hour. Latent heat gain from outside air = 14,574 -- 7549 = 7025 Btu per hour. People-Heat Gain: 50 X 225 = 11,250 Btu per hour, sensible heat. 50 X 206 = 10,300 Btu per hour, latent heat. Light Heat Gain: Summary: Component op Load Normal Transmission Load............... ............. ........... .....................................-- Btu peb Houb Sensible 16,164 47,946 7,549 11,250 14,335 97.244 Latent 7,025 10.300 17,325 Total Load: 97,244 + 17,325 = 114,569 Btu per hour.