The wall of a furnace is made up of three layers of thicknesses 250 mm, 100 mm and 150 mm with thermal conductivities of 1.65, k and 9.2 W/m.K, respectively. The inside is exposed to gases at 1250oC with a convection coefficient of 25 W/m2.K and the inside surface is at 1100oC. The outside surface is exposed to air at 25 oC with a convection coefficient of 12 W/m2.K.
Determine:
a. The unknown thermal conductivity, k
b. The overall thermal resistance
c. All surface temperatures