Document MJL0x5OYvGZdq6XxGpZGnJvDL

American Society of Heating and Ventilating Engineers Guide, 1934 different from those in factories, since there must be a considerable volume of air circulated in order to provide ventilation and cooling. COOLINC LOAD The cooling load may be divided into the following parts: 1. Transmission of heat through walls, roof, glass, etc., with allowances for sunexposed surfaces and heat capacity. 2. Transmission of solar radiation through glass and absorption by interior furnishings. 3. Heat and moisture from infiltration and from outside air introduced. 4. Heat and moisture from occupants and heat from lights, machinery and other sources. Transmission With No Sun Effect The transmission load for surfaces not exposed to the sun is calculated in a manner similar to that described in Chapter 7, by means of the following formula: where Ht = AU (to -0 . (1) Ht = heat transmitted through the material of the wall, glass, roof, or floor in Btu per hour. A = net inside area of wall, glass, roof, or floor in square feet, t = inside temperature, degrees Fahrenheit, to -- outside temperature, degrees Fahrenheit. u = coefficient of transmission of wall, floor, roof, or glass in Btu per hour per square foot per degree Fahrenheit difference in temperature. (Tables 8 to 18, Chapter 5). Temperatures The maximum cooling load in summer may be calculated for an outside dry-bulb temperature not to exceed 95 F and a wet-bulb temperature not to exceed 80 F. . While higher outside dry-bulb temperatures are frequently observed they are either of short duration or accompanied by low relative humidities. Weather Bureau reports are frequently mis- . leading in this respect as they report the maximum temperature for the day with the relative humidity which occurs during a different period and 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 F in the United States is question able. p Summer dry-bulb and wet-bulb temperatures for various cities are given in Table 1. It will be noted that the wet-bulb temperatures are not the maximums but the design temperatures which should be used in airconditioning calculations. The maximum outside wet-bulb temperatures as given in Weather Bureau reports usually occur only from 1 per cent ,to 4 per cent of the time, and they are therefore of such short duration that it is not practical to design a cooling system covering this range. Sun Effect Solar radiation is an important factor in the mechanism of heat flow into buildings. Research conducted at the A.S.H.V.E. Research Labora- 116 Chapter 8--The Cooling Load Table 1. Average Maximum Design Dry-Bulb Temperatures, Design Wet-Bulb Temperatures, Wind Velocities, and Wind Directions for June, July, August, and September State Cm Average Maximum Design Dbt-Bulb Design Wet-Bulb Summed Won) Velocitt MPH Prevailing Summer Wind Direction " Ala..... Birmingham__ Mobile_______ Ariz......... Ark........ Calif------ Phoenix_____ Little Rock:___ Los Angeles__ San Francisco.. Colo........ Conn...... D. c.-- Fla.......... Denver....... ...... New Haven..... Washington..... Jacksonville__ Tampa____ __ Ga.. Atlanta_______ Savannah........ Idaho........... Ill........-....... Boise.. Chicago--.... --....... Peoria....... -.......... Ind-----Iowa-- Ky........ La........ Maine- Md----Mass-- Mich Indianapolis......... Des Moines-------Louisville.............. New Orleans.-----Portland............... Baltimore............. Boston........ -....... Detroit- MinnZ:::::::: Mmneapoiis.. Mmii9sos..,--------.-.--.-.-.--.-.--.- Vicksbur_gMo____ ___ Kansas City........... ....... St. Louis......................... Mont--........ Helena...................... Nebr........ Lincoln Nev....... --- Reno........... ................... N. J-......... Trenton .................... N. Y............ Albany. ................ - | Buffalo-......................... New York.... ................ N. M............ Santa Fe. N. C--....... Asheville. Wilmington...... - N. D...... --... Bismarck____ __ Ohio.--........ Cleveland........... Cincinnati--...... 93 94 110 95 88 85 90 88 93 94 94 91 95 95 88 91 90 92 94 94 85 93 88 88 84 95 92 93 87 93 93 93 90 83 91 87 87 93 88 87 93 Okla____ ... LOfkiulaahiluomiuaa CityVII.;______.................. , 96 Portland..........................:. 83 Pa..._............ Philadelphia-- Pittsburgh----- RT <; r Greenville........ Tenn............. Chattanooga-- Memphis--.... 1 93 91 85 94 93 94 93 77 78 77 77 70 68 64 74 76 78 79 75 79 65 73 75 73 74 75 79 71 76 73 72 72 78 75 76 63 74 64 75 74 72 75 63 72 79 69 72 75 76 65 76 73 73 80 76 76 -- 77 5.2 8.6 6.0 7.0 6.0 11.0 6.8 7.3 6.2 8.7 7.0 7.3 7.8 5.8 10.2 8.2 9.0 6.6 8.0 7.0 7.3 6.9 9.2 10.3 8.4 6.2 9.5 9.4 7.3 9.3 7.4 10.0 7.1 12.2 12.9 6.5 5.6 7.8 8.8 9.9 6.6 10.1 6.6 9.7 9.0 10.0 9.9 6.8 6.5 7.5 S SW W NE SW SW S S S SW E NW SW NW NE S SW SW SW SW s SW SW SW SE SW s SW SW .s w SW S SW SW SE ' SE SW NW s SW S NW SW NW NW SW NE SW SW 117