Heat transfer course A large pool of stagnant air at 27 degr

A large pool of stagnant air at 27 degree C is next to a cold wall kept at T_s = -13 degree C The wall is 4.0 meters tall and 8.0 meters wide. What is the rate of heat transfer from the air to the wall by free convection? What would your answer be if the height and width of the wall were swapped (H = 8.0 m and W = 4 0 m)?

Solution

q = h_c A dT

for stagnant air h_c = 10.45 W/m²K

A = 4*8 = 32 m²

dT = 27-(-13) = 40

q = 10.45*32*40 = 13376 W

The answer will remain the same when height and width are swapped because area will remain same.