Document JJVg4ykNMxwg08EnoMqzXNN7X

256 CHAPTER IS .''-1948 Guide- Design Conditions. This temperature is the maximum hourly outdoor temperature which has been equalled or exceeded 234 per cent of the totals hours of June, July, August and September for the period of record, ire this case the 5 year period 1935-1939, and should not be confused with the period of record given in Column 4 which applies only to highest tempera ture ever recorded. Since all of these data-are based on airport records they are not necessairily applicable to cities. The data given in Columns 7 and 8 were obtained from local A.S.H.V.E. Chapter Secretaries and represent the design temperatures in local use. Where such information was not available it was taken from a publication of the A.C.R.M.A. 1 and from'various other sources. The Technical Advisory Committee on Weather Design Conditions has suggested that wet-bulb design be taken as that wet-bulb temperature which has been equalled or exceeded 5 per cent of the hours during months of the period of record. While not available for the 1948 edition of The Guide due to the tremendous task of compiling these data it is hoped that they will be available for sonie stations for future editions. The wind velocity to be used in design should be that .wind velocity which accompanies the design temperatures in each instance and since these data are not available the average summer wind velocities are reprinted from The. Guide 1947. It is pointed out that this is not necessarily the velocity which coincides with the design, temperatures but it may be of some service to the designer. Ventilation Rate The introduction of outside air is necessary for proper ventilation of conditioned spaces. Chapter 12 suggests minimum outdoor-air require ments for representative applications; but it is'td be emphasized that minimum requirements are not necessarily adequate requirements for all psychological attitudes and physiological responses. .' Local'codes and ordinances frequently specify ventilation requirements for public places and for industrial installations. ' 1 Recommended and minimum ventilation rates for the most common applications are summarized in Table 4. For further general applications, a basis of estimating the cfm per person may be taken as: .1. People not srooking_------------ !!__ _ "2. People smoking._______ __________ 7-A Recommendedt 40 Recommended , 5 Minimum 25 Minimum The cooling load necessitated-by the introduction of outside air for ventilation is determined once the indoor and outdoor design conditions are fixed. Calculations will be discussed subsequently: INSTANTANEOUS HEAT LOAD The total cooling load is frequently divided for convenience into two components; sensible heat and latent heat. While this subdivision is not imperative, past practice has found it convenient. A gain of sensible heat is considered to occur when there is a direct addition of heat to the enclosure -by any one or all of the mechanisms of conduction, convection, and radiation. A gain of latent heat is considered to occurwhen there is an addition ofwater vapor to the air of the enclosure. For example, when the humidity in an enclosure is increased by water vapor emitted by human occupants, or by water vapor resulting from a process such as cooking, the heat required to vaporize the water does not Cooling -toad Tabee 3. 'Summer Climatic Conditions4 Col. 5 Col. 6 Highest Temp; lEvEB., Recordbd*1 Design }RT-BULB yj[4b.mCp:-.2oHn% Basis* op op Col. 7 . C Design D >ry-Bulb We Temp m Tb Common C< Use1 F Coc.9 Average Summer Wind Velocity* Mph . 105 107 . .103 .. 103 . -104 107 ' .: 103" .. 93 .. 107 ' 18 ' 117 112 v ' 107 103120 " . m. 107 d . 110 : 107 .. 113 * : 94 92 ;__ ` __ 99 107 102 95 ___ L. 97 104 ! 95 > 95 - - - : . 95 __ 95 ' -- - .'90 . -- 105 __ . 105 ' 100 __ 110 * 9S....... S ---- ' 95 --. 105 d 1U: 113 ' 85 115" 111 109 . 102 i 115 112- 7 112 J. 114 7 108 D 110 94 104- . 103 80 __ , . ___ 101 ___ __ ---- V 90 v 105 _-- - 90 85 ... 100 '. .-- --- V too 1 85 - 7 v 106 7 101 6 106 9 116 7 105 79 _ . _103 85 91 .-- 95 7 104 6 6 105 1 8 104 7 104 ,0d 101 7 98; 7 : 101 . 7 ' 94" : 17 106 ; 9 106 7 102 93 ___ __u95 j_ 8_8 _84 92 __ **95 95 95 ---- --. . 95 -- 95 -- 17 104 17 ' 105 47 100 47 95 94 -- __ __ ' ~--. 47 ' 96 47 100 89 - -- 47 103 47 105 -- -- 40 98 46d 98 39 98 39 102 46 106 47 105 ' 47 105 ' 47 102 >45d 105' U7 105 -- 90 93 -- _. __ __ 93 . -- -- 95 -- - --- 739 112 747 109 739 - 104 739 100 944d 117 947 105' 947 103 __ 95 94 88 . ___- .__ 92 -- -- -- -- 947 106 -- 946 -- 939 ' 107 947 . 106 ,__ . 92 94 -- 96 78 ; 78 78 "65 - "76 *72 -.70 V 11 -r 76 >78.". "70 65-: 70- lo 65 70 72 "685 65.; 70 65 65 65-'' "*75 ' ~75 '^78. Ho 78*78 ` r*79`778 ' '."78' *76 76 ~n *65 . 65 . . 65 76 5.2 , 5J. 12.0 !o 7.9 (Co i!o io &9 61 71 ST 7.0 81 71 5S 10.0