Sample problem A furnace wall is of three layers, first layer of insulation brick of 12 cm thickness of conductivity 0.6 W/m-K. The face is exposed to gases at 870°C with a convection coefficient of 110 W/m²-K. This layer is backed by a 10 cm layer of firebrick of conductivity 0.8 W/m-K. There is a contact resistance between the layers of 2.6 x 10-4 m²-°C/W. The third layer is the plate backing of 10 mm thickness of conductivity 49 W/m-K. The contact resistance between the second and third layers is 1.5 x 10-4 m²-°C/W. The plate is exposed to air at 30°C with a convection coefficient of 15 W/ m²-K. Determine the heat flow and the surface temperatures. Sample problem Given: h, 110 W/m²K 870°C Q 870°C k₁ K₂ k₂ h₂ = 15 W/m²K 0.01 0.12 m 0.1 m m 30°C 30°C