Use thermal resistances to calculate the rate of heat loss (in kW) through the vertical wall of a boiler furnace of area 12 m². The wall is made of an inner firebrick wall 25 cm thick (k = 0.45 W/m.K), a layer of blanket ceramic insulation 10 cm thick (k = 0.25 W/m.K) and a steel protective layer, 5mm thick (k = 55 W/m.K). The inside temperature of the firebrick layer was 500 deg Celsius and the temperature on the outer wall was 50 deg Celsius.

Find Thermal resistance through outer wall (K/W) 

Find Thermal resistance through insulation (K/W) 

Find Thermal resistance through inner wall (K/W) 

Find Rate of heat loss (kW)