Document K1j8vMGjNDrrGpOg16KD0n6N

134 CHAPTER 9 I960 Guide Heat transmission coefficients for wood doors, with and without glass storm doors are given in Table 20. WIND VELOCITY EFFECT ON U VALUES Tables 5 through 8, 13-A, 14-A, L5, parts of Table 10, and Table 20 show values of U for winter calculations, for an out door wind velocity of 15 mph. Tables I3-B and 14-B show values of U for summer calculations and an outdoor wind velocity of 7.5 mph. Tables 11, 12, and 15 show values of U for both winter and summer. Tables 9 through 12 are for in door U values and are based upon still air. All roof coefficient tables also take into account the direction of heat flow. Care must be exercised in selecting the table which applies to the design conditions. Table 21 shows comparative values of U tor other wind velocities. When this table is used for mmmgr - Table 20 .... Coefficients of Transmission (U) of Solid Wood Doors Caeffldeflh OT9 expressed in Bte per (hoar) (square foot) (Fahrenheit deS*e diSerene* a teaperehtre between tho air oa (ho two sides), and are bond span as outside wind velocity of 15 mph. Noams! Tfticlcxien Acted rudeness u> 0* Witt Gfats laches Inches Exposed Door Storm Ooor* 1 'X, 0 64 0.37 IX IK* 0.55 0.34 m IK* 0.49 0.32 IX m 0.48 0.31 2m 2M 2X 3 2H 0.43 0.36 0.31 0.28 0.26 0.23 * Competed tain* t - 1.10 far wood, ft - 1.45,/, - *.0, sad 1.03 toeirspeoe. vslgnof 0.85 m7 be wad to ia*lt expoeed doon coalmining thin wood ptanb <r oaefa pane* at clus, sad 0.89 to the sum with gins storm door*. SO pmeat glass sad thia wood panels. U values, it is necessary to enter the table at 7.5 mph which can be interpolated between 5 and 10 mph. Any value taken from this table should be rounded to two significant figures. Example 8: Find the coefficient of transmission V of a frame wall consisting of stucco, 2^2-ic. insulation board sheathing, 2 x 4-in. studs, gypsum lath and plaster, and with 2-in. blanket insulation between studs, for 25 mph wind velocity. Solution: From Table 5, this wall, F37, with no insulation between studs has a value of V - 0.22. From Table 16, Part A, Col. 4, this wall with 2-in. insulation added has a value of O " 0.084. Entering Table 21 in the 15 mph column, interpolate between 0.080 and 0.000 in 15 mph column and proceed hori zontally to the 25 mph column where the U value is found by interpolation to be 01185. Table 21 .... Conversion Table for Wall Coefficient U for Various Wind Velocities U for IS mph* 0 U for 0 to 30 mph Wind Velocities 5 10 20 25 30 0.050 0.060 0.070 0.080 0.090 0.049 0.059 0.068 0.078 0.087 0.050 0.059 0.069 0.079 0.089 0.050 0.060 0.070 0.080 0.090 0.050 0.060 0.070 0.080 0.090 0.050 0.060 0.070 0.080 0.091 0.050 0.060 0.070 0.080 0.09L 0.100 0.110 0.130 0.150 0.170 0.096 0.105 0.123 0.141 0.158 0.099 0.108 0.127 0.147 0.166 0.100 0.109 0.129 0.149 0.169 0.100 0.110 0.131 0.151 0.171 0.101 0.111 0.131 0.151 0.172 0.101 0.111 0.131 0.152 0.172 0.190 0.210 0.230 0.250 0.270 0.175 0.192 0.209 0.226 0.241 0.184 0.203 0.222 0.241 0.250 0.188 0.208 0.227 0.247 0.266 0.191 0.212 0.232 0.252 0.273 0.192 0.213 0.233 0.253 0.274 0.193 0.213 0.234 0.254 0.275 0.290 0.310 0.330 0.350 0.370 0.257 0.273 0.288 0.303 0.318 0.278 0.296 0.314 0.332 0.350 0.286 0.305 0.324 0.344 0.363 0.293 0.313 0.333 0.354 0.375 0.295 0.315 0.336 0.357 0.378 0.296 0.317 0.338 0.359 0.380 0.390 0.410 0.430 0.450 0.500 0.333 0.347 0.362 0.376 0.410 0.368 0.385 0.403 0.420 0.464 0.382 0.402 0.421 0.439 0.487 0.395 0.416 0.436 0.457 0.509 0.399 0.420 0.441 0.462 0.514 0.401 0.422 0.444 0.465 0.518 0.600 0.700 0.800 0.900 1.000 0.474 0.535 0.592 0.645 0.695 0.548 0.631 0.711 0.789 0.865 0.581 0.675 0.766 0.858 0.949 0.612 0.716 0.821 0.927 1.034 0.620 0.728 0.836 0.946 1.058 0.626 0.736 0.847 0.960 1.075 1.100 1.200 1.300 0.742 0.786 0.828 0.939 1.010 1.080 1.039 1.129 1.217 1.142 1.250 1.359 1.170 1.285 1.400 1.192 1.318 1.430 * It in fiat adman fa from pnvfaw tsUes ar m wkelsted to 15 mph wind velocity. CALCULATING SURFACE TEMPERATURES In many heating and cooling load calculations it is neces sary to determine the inside surface temperature or the tem perature of the surfaces within the structure. As the resistance of any path of heat flow is expressed in Fahrenheit degrees per (Btu)/(hbur) (square foot)*, the resistances through any two paths of heat flow would be proportional to the tempera ture drop through these paths, and can be expressed as fol lows: Be iU - Q R* " (ti - ti) (7) where R\ *> the resistance from the indoor air to any point in the structure at which the temperature is to be deter mined. R* *= the overall resistance of the wall from indoor air to outdoor air. U " indoor air temperature. , * temperature to be determined. t, ~ outdoor air temperature. Example 9: Determine the inside surface temperature for a wall having an overall coefficient of beat transmission U ** Heat Transmission Coefficients of Building Materials 135 0 25 indoor air temperature 70 F, and outdoor air temperature -20 F. Solution: R 1/Si - 1/1.46 - 0.684 R, ~ i/V - 1/0.25 - 4.00 Then, by Equation 7 0-684 70 - /, 4-00 " 70 - (-20) I, 54.6 F Example 10: Determine the temperature of the bottom of a 4-in. insulated concrete roof slab to which has been glued ii-ia. acoustical tile (C 0.81) as the interior finish. The roof-ceiling overall coefficient of heat transmission V is 0.14 for heat flow up. The indoor air temperature is assumed to be 70 F and the outdoor air temperature --20 F. Solution: 111 1 R, ft + C " 1A3 + 084 180 R* - V 0.14 7.14 Then, by Equation 7 1-80 70 -- t, 7.14 " 70 - (-20) t, - 47.3 F The concrete surface temperature is of interest since refer ence to a psychrometric chart or table will show that moisture condensation could occur on this surface under the above conditions (47.3 F) if the relative humidity in the room ex ceeds 44 percent. Additional roof insulation should be-con sidered above the slab to avoid condensation at this point if higher relative humidities in the room are anticipated. The same procedure can be used for determining the tem perature it any point within the structure. A chart for determining inside wall surface temperature is given in Fig. 13 of Chapter 30, Parrel Heating. REFERENCES * Standard Method o} Testfor Thermal Conductivity by Means of the Guarded Hot Plate, sponsored by ASHVE, ASTM, ASRE, and NRC, and approved as a tentative code by ASHVE and ASTM in 1942 (ASTM designation C-177-45, Approved, 1945). * F. B. Rowley and A. B. Algren: Heat Transmission Through Building Materials (University of Minnesota, Engineering Ex periment Station Bulletin No. 8, p. 11). * M. S, Kerston: Thermal Properties of Soils (University of Minnesota, Engineering Experiment Station Bulletin No. 28, June 1949). 4 G. B. WUkes andC. M. F. Peterson: Radiation and convec tion from surfaces in various positions (ASHVE Transacactions, Vol.' 44. 1938, p. 513). * B. F. Raber and F. W. Hutchinson: Radiation corrections for basic constants used in the design of all types of heating systems (ASHVE Transactions, Vol. 51, 1945, p. 213). * F, B. Rowley, A. B. Algren, and J. L. Blackshaw: ASHVE Research Report No. 869--Surface conductances ss affected by air velocity, temperature and character of surface (ASHVE Transactions, Vol. 36, 1930, p. 444). T G. V. Parmelee and R. G. Huebscher: Forced Convection Heat Transfer from Flat Surfaces (ASHVE Research Bul letin No. 3, p. 40, also published in ASHVE Transactions. Vol. 53, 1947, p. 245). G. V. Parmelee and W. W. Aubele; ASHVE Research Report No. 1399--Heat flow through unshaded glass: Design data for load calculations (ASHVE Transactions, Vol. 56, 1950, p. 371). * H. E. Robinson, F. J. Powliteh,and R.8. Dill:The Thermal Insulating Value of Airspaces (Housing and Home Finance Agency, Housing Research Paper No. 32, U. S. Government Printing Office, 1954). * G. B. Wilkes, F. G. Hechler, and E. R. Queer: Thermal test coefficients of aluminum insulation for buildings (ASHAE Transactions, Vol. 46, 1940, p. 109). 11F. A. Joy: Improving attie space insulating values (ASHAE Transactions, Vol. 64,1958, p. 251). ** F. C. Houghton, S. I. Tsimuty, Carl Gutberiet, and C. J. Brown: ASHVE Research Repost No. 1213--Heat loss through basement walls and floors (ASHVE Transactions, Vol. 48, 1942, p. 369). 11 R. S. Dill, W. C. Robinson, and H. E. Robinson: Measure ments of Heat Losses from Slob Floors (National Bureau of Standards, Building Materials and Structures Report BMS 103). 4 G. V. Parmelee: Heat Transmission through Glass (ASHVE Research Bulletin No. 1, July 1947). BIBLIOGRAPHY ASHVE Research Reports: No. 852--F. B. Rowley, A. B. Algren. and J. L, Blackahaw: Effects of air velocities on surface coefficients (ASHVE Trans actions, Vol. 36, 1930, p. 123). No. 895--F.C. Houghton and Paul McDermott: Wind veloci ties gradients near a surface and their effect on film conduct ance (ASHVE Transactions, Vol. 37, 1931, p. 301). No. 914--F. B. Rowley and W. A. Eekley; Surface coefficients to affected by direction of wind (ASHVE Transactions, Vol. 38, 1932, p. 33). No. 915--F. C. Houghton and Carl Gutberiet: Conductivity of concrete (ASHVE Transactions, Vol. 38, 1932, p. 47). No. 964--F. B. Rowley: The heat conductivity of wood at climatic temperature differences (ASHVE Transactions, Vol. 39, 1933, p. 329). No. 966--F. B. Rowley: Insulating value of bright metallic surfaces (ASHVE Transactions, Vol. 40, 1934, p. 413). No. 1026--F. B. Rowley, A. B. Algren, and Clifford Carlson: Thermal properties of concrete construction (ASHVE Trans actions, Vol. 42, 1936, p. 33). No. 1048--F. B. Rowley, A. B. Algren, and Robert Lander: Thermal properties of concrete construction (ASHVE Trans actions, Vol. 43, 1937, p. 33). No. 1351--G. V. Parmelee and W. W. Aubele:Overall coeffi cients for flat glass determined under natural weather condi tions (ASHVE Transactions, Vol. 55, 1949, p. 39). G. B. Wilkes and C. M. F. Peterson: Radiation and convec tion across air spaces in frame construction (ASHVE Trans actions, Vol. 43, 1937, p. 351). L. W. Schad: Insulating effect of successive air space bounded by bright metallic surfaces (ASHVE Transactions, Vol. 37, 1931, p. 285). J. D. MacLean: Thermal conductivity of wood (ASHVE Transactions, Vol. 47, 1941, p. 323). G. B. Wilkes and C. 0- Wood: The specific heat of thermal insulating materials (ASHVE Transactions, Vol. 48, 1942, p. 493). D. B. Anderson: Heat loss studies in four identical buildings to determine the effect of insulation (ASHVE Transactions, Vol. 48, 1942, p. 471).