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j'j S; i i ! I 196 CHAPTER 9 1955 Guide Wind Velocity Correction for t/-Values Tables 7 to 9, and 15 to 19, present values of U for walls and other surr-7.-i''V faces based on an outside wind velocity of 15 mph. Table 21 shows com parative values of V for other wind velocities. * Example S: Find the coefficient of transmission XJ of a frame, wall consisting o! wood siding, ff-in. insulation board sheathing, 2 x 4-id. studs, gypsum lath and t? piaster, and with 2-in. blanket insulation between studs, for 25 mph wind velocity. Solution: From Table 7, Wall No. 40, with no insulation between studs has a value-'"of V = 0.19. From Table 6, Col. B, this wall with 2-in. insulation added has a value i`r of U = 0.084. Entering Table 21 in the 15 mph column, interpolate between 0.080 *" and 0.090 in 15 mph column and proceed horizontally to the 25 mph column where the U-value is found by interpolation to be 0.085. T,,,, 21. 17 FOB 0 TO 30 MPH Wind Velocities U fob 15 mph1 0.050 0.060 0.070 0.060 0.090 0.100 0.110 Q.130 0.150 0.170 0.190 0.210 0.230 0.250 0.270 0.290 0.310 0.330 0.350 0.370 0.390 0.410 0.430 0.450 0.500 0.700 0.800 0.900 1.000 1.100 1.200 1.300 0I 0.049 0.059 0.068 0.078 0.087 0.096 0.105 0.123 0.141 0.158 0.175 0.192 0.209 0.226 0.241 0.257 0.273 0.288 0.303 0.318 0.333 0.347 0.362 0.376 0.410 0.474 0.535 0.592 0.645 0.695 0.742 0.786 Q.828 5 0.050 0.059 0.069 0.079 0.089 0.099 0.108 0.127 0.147 0.166 0.184 0-203 0.222 0.241 0.259 0.278 0.296 0.314 0.332 0.350 0.368 0.385 0.403 0.420 0.464 0.548 0.631 0.711 0.789 0.865 0.939 1.010 1.080 10 0.050 0.060 0.070 0.080 0.090 0.100 0.109 0.129 0.149 0.169 0.188 0.208 0.227 0.247 0.266 0.286 0.305 0.324 0.344 0.363 0.382 0.402 0.421 0.439 0.487 0.581 0.675 0.766 0.858 0.949 1.039 1.129 1.217 20 0.050 0.060 0.070 0.100 0.110 0.131 0.151 0.171 0.191 0.212 0.232 0.252 0.273 0.293 0.313 0.333 0.354 0.375 0.395 0.416 0.436 0.457 0.509 0.612 0.716 0.821 0.927 1.034 1.142 1.250 1.359 25 0.050 0.060 0.070 0.101 0.111 0.131 0.151 0.172 0.192 0.213 0.233 0.253 0.274 0.295 0.315 0.336 0.357 0.378 0.399 0.420 0.441 0.462 0.514 0.620 0.728 0.836 0.946 1.058 1.170 1.285 1.400 U in first column is from previous tables or ss calculated tor IS mph wind velocity. 30 u.wv 0.060 0.070 0.080 0.091 0.101 0.111 0.131 0.183 0.173 0.193 0.213 0.234 0.384 0.378 - 0.317 0.338 0.389 0.380 - 0.401 0.423 0.444 0.468 0.818 0.626 0.738 0.847 0.980 1.078 it _ . 1.193 1.318 1.430 CALCULATING SURFACE TEMPERATURES % In many heating and cooling load calculations it is necessary to deter' mine the inside surface temperature or the temperature of the surfaces within the structure. As the resistance of any path of heat flow is esj Dressed in Fahrenheit degrees per (Btu) (hour) (square foot), the rej Heat Transmission Coefficients of Building Materials 197 sistances through any two paths of heat flow would be proportion^ to the temperature drop through these paths, and can be expressed as follows: where ft _ (ti - (,) Rt= (ti - t.) (6) ft <= the resistance from the inside air to any point in the structure at which the. temperature is to be determined. ft = the overall resistance of the wall from inside air to outside air. t; = inside air temperature. (, = temperature to be determined. . io = outside air temperature. Example 4: Determine the inside surface temperature for a wall having an overall coefficient of heat transmission U = 0.25, inside air temperature 70 F, outside air temperature --20 F. Solution: Then, by Equation 6 R, = I//, = 1/1.65 = 0.606 R, = 1/U = 1/0.25 = 4.00 0,606 70 - L 4.00 " 70 - (-20) (, = 56.4 F The same procedure can be used for determining the temperature at any point within the structure. A chart for determining inside wall surface temperature is given in Fig. 12 of Chapter 24, Panel Heating. REFERENCES 1 Standard Method of Test for Thermal Conductivity by Means of the Guarded Hot Plate, sponsored by A.S.H.V.E., A.S.T.M., A.S.R.E., and N.R.C., and approved as a Tentative Code by A.S.H.V.E. and A.S.T.M. in 1942 (A.S.T.M. designation C-177-45, Approved 1945). 'Heat Transmission Through Building Materials, by F. B. Rowley and A. B. Algren (University of Minnesota, Engineering Experiment Station Bulletin, No. 8, p. 11). 'Thermal Properties of Soils, by Miles S. Kersten (University of Minnesota, Eninneertng Experiment Station Bulletin No. 28, June 1949). ,,^?ia^ation and Convection from Surfaces in Various Positions, by G. B. Wilkes and C. M. F. Peterson (A.S.H.V.E. Transactions, Vol. 44, 1938, p. 513). Radiation Corrections for Basic Constants Used in the Design of All Types of eating Systems, by B. F. Raber and F. W. Hutchinson (A.S.H.V.E. Transactions, V>- 51. 1945, p. 213). ^ H-V.E. Research Report No. 869--Surface Conductances as Affected by _ , \etecRy, Temperature and Character of Surface, by F. B. Rowley, A. B. Algren 0 J- L. Blackshaw (A.S.H.V.E. Transactions, Vol. 36, 1930, p. 444). R ,p'0tie^ Convection Heat Transfer from Flat Surfaces, by G. V. Parmelee and 4 ri Huebscher (A.S.H.V.E. Research Bulletin No. 3, p. 40; also published in '&.H.V.E. Transactions, Vol. 53, 1947, p. 276). r,,, A SjH.V.E. Research Report No. 1399--Heat Flow through Unshaded Glass: Tp.P Cata for Load Calculations, by G. V. Parmelee and W. W. Aubele (A.S.H.V.E. B4NS4cnoNs, Vol. 56,1950, p. 371). aQ(j j^e Therjjjjj insulating Value of Airspaces, by H. E. Robinson, F. J. Powlitch 1954 it o"HI (Housing and Home Finance Agency, Housing Research Paper No. SB, > u- S. Government Printing Office).