Calculate the rate of heat loss through the vertical walls of a boiler furnace 4m by 3m by 3m high.
The walls are constructed from an inner firebrick wall 25cm thick of thermal conductivity 0.4 W/ m K, a layer of ceramic blanket insulation of thermal conductivity 0.2 W/ m K, 8cm thick and a steel protective layer of thermal conductivity 54 W/ m K 2mm thick.
The inside temperature of the firebrick layer was measured at 600 C and the temperature of the outside of the insulation at 60C. What is the temperature drop across the steel layer?