A 1.5-m² black surface at 120°C is losing heat to the surrounding air at 30°C by convection with a convection heat transfer coefficient of 18 W/m².°C, and by radiation to the surrounding surfaces at 10°C. The total rate of heat loss from the surface is

Question

Quizplus · Accepted Answer

Solved by EES Software. Solutions can be verified by copying-and-pasting the following lines on a blank EES screen. 
sigma=5.67E-8 "W/m^2.K^4"
eps=1
A=1.5 "m^2"
h_conv=18 "W/m^2.C"
Ts=120 "C"
Tf=30 "C"
Tsurr=10 "C"
Q_conv=h_conv*A*(Ts-Tf) "W"
Q_rad=eps*sigma*A*((Ts+273)^4-(Tsurr+273)^4) "W"
Q_total=Q_conv+Q_rad "W"
"Some Wrong Solutions with Common Mistakes:"
W1_Ql=Q_conv "Ignoring radiation"
W2_Q=Q_rad "ignoring convection"
W3_Q=Q_conv+eps*sigma*A*(Ts^4-Tsurr^4) "Using C in radiation calculations"
W4_Q=Q_total/A "not using area"

A 15-M2 Black Surface at 120°C Is Losing Heat to the the Surrounding

A 15-M² Black Surface at 120°C Is Losing Heat to the the Surrounding