Document jBQLQML5Gva4LxM5NQJKe325k

140 Chapter 7 1945 Guide west walls overlap each other-due-to scattered-sky radiation-on- the-west _wall during the forenoon and on the east wall during the afternoon. This phase relationship has an important bearing on the cooling load. Failure to consider the periodic character of heat flow resulting from diurnal movement of the sun and the lag due to heat capacity of the structure, which determine the timing and magnitude of the heat wave flowing through the wall, may result in a large error in load calculations. ^The values of solar intensity appearing in Fig. 1 must not be confused with the actual heat transmission through the wall for much of the solar radiation impinging against the outer surface fails to pass through the wall. Instead it is delivered to the outside air by reflection, radiation, convection and conduction. A mathematical solution for the determina tion of solar heat transmission has been developed but the equations Fig. 1. Solar Intensity Normal to Sun on Horizontal Surface and on Walls for August 1 at 40 Deg North Latitude involved are too complex for practical application2. A method embodying an approximate determination of the maximum contribution to the cooling load due to heat transfer from the inside surface of a wall exposed to solar radiation has been developed3. The heat flow in summer through various types of roofs and walls has been measured by the A.S.H.V.E. Laboratory. The curves in Fig. 2, give the heat flow through the inside surface of roofs4 with details of the construction of the roofs tested. The conditions for which these results are given are: solar radiation for 40 deg north latitude on August 1 c , 'A-fResearch Report No. 923--Heat Transmission as Influenced by Heat Capacity and Solar Radiation, by F. C. Houghten, J. L. Blackshaw, E. M. Pugh and Paul McDermott (A.S.H.V.E. Transactions, Vol. 38, 1932, p. 231). Effect of Heat Storage and Variation in Outdoor Temperature and Solar Intensity on Heat Transfer Through Walls, by J. S. Alford, J. E. Ryan and-F. O. Urban (A.S.H V E Transactions, Vol. 45, 1939, p. 369). Periodic Heat Flow in Building Walls Determined by Electrical Analogy Method, by Victor Paschkis (A.S.H.V.E. Transactions, Vol. 48,1942, p. 75). Summer Comfort hactore as Influenced by the Thermal Properties of Building Materials, by C. O. Mackey and L. T. Wright Jr. (A.S.H.V.E. Transactions, Vol. 49, 1943, p. 148). `Periodic Heat Flow--Homogeneous Walls or Roofs, by C. O. Mackey and L. T. Wright, Jr. (A.S.H.V.E. Journal Section, Heating, Piping and Air Conditioning. September. 1944, P. 546). `A.S.H.V.E. Research Report No. 1157--Summer Cooling Load as Affected by Heat Gain Through Dry, Sprinkled and Water Covered Roofs, by F. C. Houghten, H. T. Olson and Carl Gutberlet (A.S.H.V.E. Transactions, Vol. 46, 1940, p. 231). Cooling Load 141 Table 2. Solar Radiation (Directplus-Sky) Impinging Against--Walls-Having Several Orientations: and a Horizontal Surface For 80 Deg North Latitude on August 1 Sun Time Northeast Intensity op Solar Radiation, Btu per Sq Ft per Hour East Southeast South Southwest West Northwest Horizontal Surface, 6:20 6:00 7:00 8:00 9:00 10:00 11:00 12:00 IKK) 2:00 3:00 4:00 5:00 6 K)0 .6:40 0 37 119 153 130 86 35 26 25.5 23.5 21 17 11 4.5 0. 00 47 23 145 91 . 207 149 194 158 152 143 94 26 25.5 85 65 25.5 23.5 21 17 23.5 21 17 11 11 . 4.5 - 4.5 00 0 4.5 11 17 35 63 80 85 80 63 . 35 17 11 4.5 0 0 4.5 11 17 21 23.5 25.5 65 85 143 158 149 91 .23 0 0 4.5 11 17 21 23.5 25.5 26 94 152 ' 194 207 145 47 0 0 4.5 11 0 ii 64 17 21 23.5 147 213 262 25.5 290 26 300 35 . 290 86 262 130 213 153 147 119 64 37 11 00 Table 3. Solar Radiation (Direct plus Sky) Impinging Against Walls Having Several Orientations and a Horizontal Surface 'For 85 Deg North Latitude on August 1 & Intensity of Solar Radiation, Btu per Sq Ft per Hour Sun Time Northeast East Southeast South Southwest West Northwest Horizontal Surface 5:07 6:00 7:00 8:00 9:00 10:00 ll'KM 12:00 1:00 2:00 3:00 4:00 5:00 6:00 6:53 0 43 121 147 120 71 28 26 25.5 23.5 21 17 11 4.5 0 0 49 151 207 194 152 94 26 25.5. 23.5 21 17 11 . 4.5 0 0 27 97 155 169 156 129 84 . 25.5 23.5 21 )7 11 4.5 0 0 4.5 11 25 49 83 103 109 103 83 49 25 11 4.5 0 0 4.5 11 17 21 23.5 25.5 84 129 156 169 155 97 27 0 0 4.5 11 17 21 23.5 25.5 26 94 152 194 207 151 49 0 0 4.5 11 17 21 23.5 25.5 26 28 71 120 . 147 121 43 0 0 13 72 151 213 245 288 298 288 245 213 151 72 13 0.