1. The problem statement, all variables and given/known data A furnace is constructed with 0.5 m of fire brick, 0.15 m of insulating brick and 0.25 m of ordinary building brick. The inside surface-temperature is 1530K and the outside surface temperature is 525K. The thermal conductivities of the fire, insulating and building bricks are 1.4, 0.21, and 0.7 W/m-K, respectively. Calculate the following per square meter area: (a) Total resistance of the wall in K/W (b) Rate of heat flow in W (c) The temperatures at the junctions of the bricks. 2. Relevant equations Q/T = kAΔT / L 3. The attempt at a solution (a) Total resistance of the wall in K/W: answer 1.43 K/W (b) Rate of heat flow in W: answer 703.5 W (c) The temperatures at the junctions of the bricks. (Temperature drop over firebrick+insulating brick)/(Total temperature drop) = (0.3571+0.7143/1.43) Temperature drop over firebrick+insulating brick: (1530K-525K) ⋅ (0.3571+0.7143/1.43) = 752.9769 K Hence the temperature at the (firebrick & insulating)-ordinary brick interface = (1530K - 752.9769 K) = 777.0231 K The correct answer according to the answer sheet is 778 K, there might be a slight difference but I want to make sure that my computation is right?