The brick wall (k=0.80 W/m°C) of a building has 4.0 m X 10.0m dimensions and 15cm thick. How much heat in joules flows through the wall in 12-hour period when the average inside and outside temperatures are 20°C and 50°C?
q=k•A•ΔT/Δx=0.8•4•10•(50-30)/0.15 =4267 W
Q=qt=4267•12•3600=7.86•10¹¹ J