Question

The Weather Channel reports that it is a hot, muggy day with an air temperature of 90°F, a 10 mph breeze out of the southwest, and bright sunshine with a solar insolation of 400 W/m^2. Consider the wall of a metal building over which the prevailing wind blows. The length of the wall in the wind direction is 10 m, and the emissivity is 0.93. Assume that all the solar irradiation is absorbed, that the surroundings are at Tsur = 85°F, and that flow is fully turbulent over the wall. Estimate the average wall temperature.

Answer 1

given To = 90F = 190-32) = 32.22 C = 305.22 k TABLE A-15 Properties of air at 1 atm pressure Specific Density Heat T, °C p, kg/m3 Cp, J/kg.K 30 1.164 1007 35 1.145 1007 32.22 Temp. Thermal Conductivity k, W/m.K 0.02588 0.02625 Thermal Diffusivity a, m/s 2.208 x 10-5 2.277 x 10-5 Dynamic Viscosity u, kg/m.s 1.872 x 10-5 1.895 x 10-5 Kinematic Viscosity v, m/s 1.608 x 10-5 1.655 x 10-5 Prandt Number Pr 0.7282 0.7268 Using interpolation 32.22-30 35-30 k-0.02588 0,02625-0.02588 i 32.22-30 -v-1.608x10S I 35-30 C1.655 - 1.608) -1.608) X05 k=0,02604 W/mK i v=1, 6289 xlos me Pr-0.7282 32.22-30 35-30 d. 7268 0,7282 ... Pr- 0,7276 → Air velocity = 10 mph . = 10 xo khtok m/s V = 4,4704 m/s

от LED — 2,26 удо (-305. 2) + 1 до око – – 4 22L2С ДЪDD - O9316.6 хто х 10 = 0 122 42T - За 426 дооо - 04 3:15. умо бо за 22 .. 22 62 Т - Д2 . o16 – 5 з хіо то х ат - ал. 2 т. – мальо - solving Using EESI

- O X EESEES Commercial: File Edit Search Options Calculate Tables Plots Windows Help -08 00 OBO OPLO Examples EEx Equations Window 5.2731e-7*T^4+122.62“T-41426.076=0 FEy Formatted Equations 5.2731 x 10-7. T + 122.62 - T - 41426.076 = 0 Eey Solution Main Unit Settings: [kj]/[C]/[kPa]/[kg]/[degrees] T = 302 No unit problems were detected. Calculation time = 0 sec.

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