Document 4anOg37J9LjawepvaoqaVo83p

186 CHAPTER 13 1959 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 Gear Maoiphmr** and 18 Deg DedinofJon, North (Aogosf I) Note; For total insfanfaneou* heat gain, add Hwn values to the Table 13 value* loMt 30 Deg north 40 Deg north , 50 Deg north AM - 1 6 a.m. 7 8 9 6 p.m. 5 4 3 10 2 11 1 12 . 5 ajn. 6 7 8 7 p.m. 6 5 4 93 10 2 11 1 12 5 a.m. 6 7 8 7 pjn. 6 5 4 93 10 2 11 1 12 fotfonteneous Hoot Gain in Btu per (hr) l*q ft) N NE SE S SW W NW Horiz. 25 98 108 52 23 155 190 110 16 148 205 136 16* 106 180 136 s5 10 10 n 18 21 IS 17 54 128 116 34 17 18 20 59 78 45 19 18 18 19 35 49 35 3 7 6 2 00 28 116 131 67 76 16 149 195 . 124 11 to 14 129 205 156 18 18 IS 79 180 162 42 H 16 31 127 148 69 16 17 18 58 113 90 23 17 17 19 64 98 64 20 54 54 20 3 8 25 128 149 81 87 18 139 197 136 18 10 18 107 202 171 32 18 14 54 176 183 72 14 IS 18 124 174 110 16 16 16 57 143 136 42 16 16 18 96 144 96 6 10 18 . IS 16 18 19 5 10 18 IS 16 18 19 00 66 10 10 18 12 14 14 16 16 17 17 19 17 88 77 10 . 10 18 18 14 14 IS IS 16 16 18 16 17 71 137 195 241 267 276 1 25 77 137 ` 188 229 252 259 6 34 80 129 173 206 227 234 * Italia isdksis T PM -> EN NW W $w S SE KE Horiz. sr_ 5 a.m. 6 7' 8 9 10 11 12 2 3 5 6 7 8 9 Table 13 .... Instantaneous Rates of Heat Qain by Convection and Radiation from a Single Sheet of Unshaded Common Window Glass For dear Atmosphere* and ?8 Deg Declination, North (August I) For 30, 40, 50 Deg North latitude For 80 F Indoor Temperature Note; For total aufanfanooa* heat gam, add fheee value* to 8m Fable 12 value* Irutantoneon Hoof Gain in Bfu pot (far) (*q ft) Ory-Bulb F Dog N NE E SE S SW w 74 -6 -6 -6 -6 -6 -6 -6 74 -5 -4 -4 -5 -5 -6 -6 75 -5 -2 -2 -3 -5 -5 -5 77 -3 0 1 0 -2 -3 -3 80 0 2 4 3 1 0 0 83 3 4 6 6 5 3 3 87 8 8 10 11 10 9 8 go 12 12 12 13 14 13 12 93 15 15 15 16 17 17 17 94 16 16 16 16 18 19 19 95 17 17 17 17 19 21 21 94 16 16 16 16 17 20 20 93 15 15 15 15 15 18 19 91 13 13 13 13 13 14 15 87 8 8 8 8 8 8 8 85 6 6 6 6 6 6 6 83 . 3 3 3 3 3 3 3 NW . -6 -6 -5 -3 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 187 Table 14 .., Application Factors to'Apply to Tables 12,13 and 15 to Obtain Instantaneous Rates of Heat Gam for Various Types of Single Flat.Glass-and Combinations of Two Sheets of Hat Glass Spaced at. ^ In. Glass* . Normal Incidence Frastsmittonce Facfor fo Apply to Fable 12 Facfor fo Apply fo Fable 13 Single common window Siagle regular plate Single heat absorbing plate Double common window Double regular plate Heat absorbing plate outdoors! Regular plate indoors / 0:87 0.77. 0.41 0.76 0.60 0.35 1.00 0.87 0.46b 0.85 0.66b 0.37b 1.0m* + o.o(F}< 1.0(A) + 0.25(F) 1.0(A) + 1.00(F) 0.6(A) + 0.10(F) 0.6(A) + 0.55(F) 0.6(A) + 0.75(F) * Commoo window ctae H in- thick. PUte (tees U in. thick. b Far better preewoa, iscreaee factors 10 percent when (face is in the ' X nlocs ere Tibb 13 valnea. * Y valttee srs Table IS valve. fide surface conductance lor convection fd as given by Equa tion 3, and an equivalent surface conductance for radiation Sri as given by Equation 4. Inside surfaces seen by the glass are assumed to radiate as a black body at room air tempera ture. / - 0.27 ((,,- - l.) " (3) where. Ifi temperature of inside surface of glass, Fahrenheit. t{ = temperature of indoor air, Fahrenheit. A more complete treatment of the problem is given in an ASHAE research paper.11 Design Tables for Fiat Glass Tables 12 and 13 give design values of instantaneous rates of heat gain for single unshaded common window glass for a solar declination of IS 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. Tal-le 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 imurimum as tabu lated. The total heat gain is 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 ductance1 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.Table141 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 glass were computed for a ^4-io. air space. No great error is 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 ts 148 Btu per (hr) (sq ft) for common window glass; from Table 14, the factor for regular plate glass is 0.87. The 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 Y 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, 9 - 0.87 X 148 + 1.0 X 19 + 0.25 X 27 + 1.0 (98 - 95) -- 157A 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 Y from Table 16 and then added to the corresponding Table 13 values.- The total instantaneous heat gain is 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 ASHAE research paper11 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-roered 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 orients-