A layer of refractory material (k=1.5 kcal/h.m.C) 50 mm thick is located between two steel sheets (k = 50 kcal/h.mC) 6.3 mm thick. the faces of the refractory layer adjacent to the plates are rough so that only 35% of the area total is in contact with the steel. The empty spaces are occupied by air (k=0.013 kcal/h.m.C) and the average roughness thickness of 0.8 mm. whereas the temperatures of the outer surfaces of the steel plate are 450 C and 90 C. calculate the rate of heat that settles in the composite wall. NOTE: In roughness, the air is still (only consider the conduction).

refractory steel TH roughness T2 48,4 6.3