The inside dimensions of a refrigerator are 50 cm 50 cm base and 100 cm height. This chamber is to be maintained at 7°C. The walls of the refrigerator are constructed of two mild steel sheets 3 mm thick with 5 cm of glass wool insulation between them. If the average heat transfer co-efficient at the inner and outer surfaces are 10 and 12.5 kcal/ m2 hr°C respectively, estimate the rate at which heat must be removed from the interior to maintain the surrounding outside temperature at 28°C. What will be the temperature at the surface of the wall? The thermal conductivities for mild steel and glass wool are 40 and 0.04 kcal/ m-hr-°C respectively.