
Natural Convection Heat Transfer 317
12.11 The roof of a house is 8 m long by 5 m wide and is made of 20 cm
thick brick with thermal conductivity of 0.7 W/m°C. This house is
air conditioned such that the inside of the house is kept at 15°C at all
times. The outside air temperature is 45°C and wind at 36 km/h is
blowing along the 8 m long side of the roof.
a. Determine the rate of heat gain from the roof of this house.
Neglect any radiation heat transfer rate.
b. What are the temperatures at the interior and exterior sides of this
roof?
c. If the emissivity of the roof is 0.7, calculate the interior and exte-
rior radiation ...