150 W/m² 27°C 12 a = 8=08 air and surroundings, 40°C h=8W/m²K
The interior surface of a 25 cm thick wall has a temperature of 27 \deg C as shown in the figure. The outer surface is exposed to a solar radiation of 150 W/m^2 and exchanges heat by radiation and convection with the surroundings and the air that are at the same temperature of 40 \deg C. The coefficient of heat transfer by convection is 8 W/m^2* K, consider both the absorptivity (\alpha ) and emissivity (\epsi equal to 0.8. Assuming transfer of 1D heat and at steady state, determine the surface temperature outside and the heat flow by conduction in the wall in three conditions different: a) If the wall is made of brick (k=0.72 W/m*K) b) If the wall is made of wood (k=0.17 W/m*K) c) If the wall is made of rigid foam (polyurethane) (k=0.026 W/m*KMake a diagram of the corresponding thermal resistance circuit and a diagram of the variation of temperatures from the interior wall to the air abroad.
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