Hot combustion gases of a furnace are separated from the ambient air and its surroundings, which are at 25 C, by a brick wall that is 0.15m thick. The brick has a thermal conductivity of 1.2 W/mK and a surface emissivity of 0.8. Under steady state conditions an outer surface temperature of 100 C is measured. Free convection heat transfer to the air adjoining the surface is characterized by a convection coefficient of H=20W/m^2K.
Find the brick inner surface temperature.