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Homework Statement
The black roof of a building has an emissivity of 0.9 and an absorbtivity of 0.8 for solar radiation. The sun beats down at midday with an intensity of 300 BTU / hr ft2.
a) If the temperature of the air and the surroundings is 68 °F, if the wind velocity is negligible, and if no heat penetrates the roof, what is the equilibrium temperature of the roof ? For the rate of conduction / convection use q/A = 0.38 (T) 1.25, where T is the temperature drop between the roof and air in degrees F.
b) What fraction of the heat from the roof is lost to radiation.
Homework Equations
The Attempt at a Solution
For this problem, assume the effective sky temperature on that day is -10F. also, the "rate of conduction / convection" just means the overall rate of conduction + convection away from the roof.
I am wondering if I approached this correctly. I used wolframalpha to solve the equation.