Do not solve 15.17. It is provided to reference for problem 15.18.

15.18 If in Problem 15.17, the lower surface of the plate is exposed to air with a convective heat-transfer coefficient of 3 Btu/h ft F, what steady-state temperature will be reached a. if radiant emission from the plate is neglected? b. if radiant emission from the top surface of the plate is accounted for? Additionally, answer this question based on your calculations for this problem: In most of the problems we will solve this semester, we will assume that radiation is negligible. Calculate the fraction of the heat transfer rate that is due to radiation. Based on this calculation, can we expect that this will generally be a good assumption? 15.17 The solar radiation incident on a steel plate 2 ft square is 400 Btu/h. The plate is 1.4 in thick and lying horizontally on an insulating surface, its upper surface being exposed to air at 90 F. If the convective heat-transfer coefficient between the top surface and the surrounding air is 4 Btu/h ft F, what will be the steady-state temperature of the plate