Document G5G3wLmVR6N5b7d9rVVgrQQMV

196 CHAPTER 13 1960 Guide Table 12 .... Instantaneous Rates of Heat Gain Due to Transmitted Direct and Diffuse or Sky Solar Radiation by a Single Sheet of Unshaded Common Window Glass For dear AtawipfwrH and 10 Deg Oadteation, North lAagttd I) Note: For total wMbmmi hoot gain, odd Am tvbti to A* Tabi* IS ralkm latitude Sun Ttau AM -- i hutautmieovi Hoot Gaia to Btu per (fa-) Uq ft} sN NE E SE SW W NW Horiz. 30 Deg north Deg north 50 Deg north 6 a.m. 6 p.m. 5 4 10 2 5 a.m. 7. p.m. 6 75 4 93 5 a.m. 7 pan. 5 93 * Itolka iodiset* ahadod (lasa. f PM --* 25 98 108 52 66 23 155 190 110 10 to 16 148 205 136 14 IS IS IS 106 180 136 21 16 16 16 195 17 54 128 116 34 17 16 18 20 59 78 45 19 18 18 19 19 35 49 35 19 19 276 3 7 620 26 116 131 67 76 16 149 195 124 It 10 u 129 205 156 18 It It 12 137 16 16 79 180 162 31 127 148 42 14 69 16 14 17 18 58 113 90 23 17 17 17 . 19 64 98 64 19 17 259 20 54 54 20 S 25 128 149 81 87 It 139 197 136 It 10 19 107 202 171 32 It IS It 129 14 54 176 183 72 14 14 16 18 124 174 110 16 16 16 16 57 143 136 42 16 16 16 18 96 144 96 18 16 234 swH NW W S SE E NE Hertz. Sun Time 5 a.m. 7 8 9 10 n 12 1 p.m. 3 4 5 6 7 Table 13 .... Instantaneous Rates of Heat Gain by Convection and Radiation from a Single Sheet of Unshaded Common Window Glass For Clear Ahaotpburut and 10 Deg Daduwtfoo* North (Aogint I) For 30, 40, SO Dag North IcfBude For 80 F Indoor Temperature Note; For total mdontsaaov* boot gain, odd there values to the Toth 13 oataoi Dry-fcsb F Deg 74 74 75 77 80 83 87 90 93 94 95 94 93 91 87 85 83 Indenfatecu* Neat Gam m file per (hr) (q ft) N I NE I E S S sw w -6 -6 -6 -6 -4 -5 -6 -0 -2 -5 -5 1 -3 4 00 3 8 12 15 4 8 12 15 6 10 12 15 11 13 16 53 10 9 14 13 17 17 3 8 12 17 16 16 16 16 18 19 19 17 16 15 13 17 16 15 13 17 16 15 13 17 16 15 13 19 17 15 13 21 20 18 14 21 20 19 15 8 88 8 888 66 33 66 33 6 3 66 33 NW --6 -6 -5 0 3 8 12 15 17 19 19 18 15 8 6 3 Horiz. -6 -5 -3 0 3 8 13 16 20 21 21 19 17 13 8 6 3 Cooling Load 197 Table 14____Application Factor to Apply to Table. 12, 13 and 15 to Obtain Instantaneoa, Rotes of Heot Coin for Various Types of Single Rat Glass and Combinations of Two Sheets of Rot Glass Spaced at yj In. Nonad Incidence Tranoaittance Feeler to Apply to Table 12 Factor to Apply to Tebit 13 Single common window Single regular plate Single heat absorbing plate Double common window Double regular plate ' Heat absorbing plate outdoor*) Regular plate indoors / 0.87 0.77 0.41 0.76 0.60 0.35 1.00 0.87 0.46* U.85 0.66* 0.37* 1.0(X)* + 0.0(K)d 1.0(X) + 0.25(F) 1.0(20 + 1.00(F) O.ecz) + 0.19(F) 0.6(X) + 0.55(F) 0.6(X) + 0.75(F) Common window c**a H thick. Ptatc class K in. thick, b For hotter precision, increase factors 10 percent whan pare b in the shade. 1 T values are Table IS raluea. side surface conductance for convection / as given by Equa tion 3, and an equivalent surface conductance for radiation fri as given by Equation 4. Inside surfaces seen by the glass are assrimad to radiate as a black body at room air tempera ture. Sh - 0.27 {lti - !<)' (3) where t,i -- temperature of inside surface of glass, Fahrenheit. ti -- temperature of indoor air, Fahrenheit. A more complete treatment of the problem is given in an ASHBAE research paper.*1 Design Tables for Flat Glass Tables 12 and 13 give design values of instantaneous rates of beat gun for single unshaded common vnndoxo glassJor* solar declination of 18 deg. This corresponds to a nominal August 1 day. The tables are based upon the solar intensity values for a clear atmosphere as given in Table 4. Table 12 values represent the first bracketed term of Equation 2a; therefore, the values are dependent only upon values of I and r. Table 13 values represent the second term of Equation 2a, and are based upon a 80 F indoor temperature and a dry-bulb temperature cycle, with a 95 F maximum as tabu lated. The total heat gain ts the sum of the Table 12 and Table 13 values. In preparing Table 13, convection and radiation heat exchange were combined, and a combined surface con ductance of 4.0 used. Corrections to be applied for other design temperatures are given' in Table 24 in a later section Effect of Deviation from Design Conditions. Tables 12 and 13 may be used for other types of glass with good accuracy, by using the factors given in Table 14. Table 12 values are multiplied by the appropriate factor given in Table 14 to obtain heat gain due to transmitted solar radia tion. For glasses having a transmittance for normally in cident radiation differing from the table values, factors may be found by linear interpolation. To obtain instantaneous rates of heat gain by convection and radiation, two steps are required. First, Table 13 values are multiplied by the ap propriate coefficient of X listed in Table 14. Second, Table 15 values are multiplied by the appropriate coefficient of Y listed in Table 14, and added to the first value. All convection and radiation gain values for double glws were computed for a yi-in. air space. No great error b involved in cooling load estimates if these are used for double glass with other air spaces. Example 8: Find the total instantaneous heat gain through a single sheet of regular plate glass in a southwest wall at 2 p.m. sun time and 40-deg north latitude on August 1. The maximum dry-bulb temperature for design is 98 F; the atmos phere is clear. The indoor temperature is 80 F. Solution: From Table 12 the heat gain due to transmitted radiation is 148 Btn per (hr) (sq ft) fbr common window glass; from Table 14, the factor for regular plate glass is 0.87. Tha coefficient of X in Table 14 is 1.0, while X is found from Table 13 for common window glass for the same hour, orientation and latitude. The coefficient of Y in Table 14 is 0.25, while the F value is found from Table 15 for a southwest wall at 2:00 p.m. and 40-deg north latitude. The correction for design dry-bulb temperature Is found from Table 24 to be 1.0 Btu per (hr) (sq ft) per degree difference from 95 F design temper ature. The total instantaneous heat gain is, from Equation 2a, q - 0.87 X 148 + 1-0 X 19 + 0.25 X 27 + 1.0 (98 - 95) -- 157.5 Btu per (hr) (sq ft). Design Tables for Rolled Figured Glass Tables 16 and 17 give design values of instantaneous rates of heat gain for a number of common patterns of single ver tical sheets of rolled figured glass. The tables are for a solar declination of 18 deg, which corresponds to a nominal August 1 day, and are based upon the solar intensity values for a clear atmosphere as given in Table 4. The values are given in terms of corrections to apply to Tables 12 and 13. The heat gain due to transmitted solar radiation is found by multiplying the Table 12 values by the approximate per centages given in Table 17. To obtain instantaneous rates of heat gain by convection and radiation, Table 15 values are multiplied by the appropriate value of F from Table 16 and then added to the corresponding Table 13 values. The total instantaneous beat gain b the sum of the gain due to transmitted solar radiation and the gain by convection and radiation. The values given in Tables 16 and 17 are based upon an ASHBAE research paper* to which the reader is directed for additional data. The values in Tables 16 and 17 may be used with fair precision for other patterns of similar transmittance and surface characteristics. For example, the data for ham mered glass may be used for glass having shallow, closely spaced ribs or for glass having small, closely spaced circular indentations. Because some patterns have distinct orienta tion properties, no attempt has been made to give values for nonvertical glass. Design Tables for Glass Block Walls Table 18 describes the glass block patterns discussed in following text. Table 19 gives design values for instantaneous heat gain due to transmitted direct and diffuse solar radiation