IF POSSIBLE CAN YOU STATE THE ASSUMPTIONS....PS I ALWAYS RATE (100%) A flat plat
ID: 1854972 • Letter: I
Question
IF POSSIBLE CAN YOU STATE THE ASSUMPTIONS....PS I ALWAYS RATE (100%)
A flat plate solar collector, 6 ft by 12 ft, is mounted on the roof of a house. The outer surface of the collector is at 110degreeF and its emissivity is 0.9. The outside air is at 70degreeF and the sky has an effective temperature for radiation of 45degreeF. The collector transfers heat by natural convection to the air with a heat transfer coefficient of 3.2 Btu/h.ft2.degreeF and also transfers heat by radiation to the sky. Calculate the total heat loss from the solar collector.Explanation / Answer
enrgy lost due to convection = hAT = 3.2 x 1 x [110-70]= 128 Btu/m^2
energy lost due to radiation = eA[T1^4 - T2^4] = 0.9 x 1 x {[43.3333+273]^4 - [7.2222+273]^4}
= 3.4625 x 10^9 Btu/m^2
add the two for the total heat loss
that is = 3.4625 x 10^9 Btu/m^2