12. Consider a wall built up of concrete and thermal insulation. The outdoor temperature is T0 = — 170C, and the temperature inside is Tj = 20oC. The wall is subdivided into three ele¬

ments. The thermal conductivity for concrete is kc = 1.7 W/m/°C, and that of the insulator is kj = 0.04 W/m/°C. Convection heat transfer is occurring at both surfaces with convection coef¬

ficients of ho = 14W/m2/0C and /?,¦ = 5.5 W/m2/0C Calculate the temperature distribution of the wall. Also, calculate the amount of heat flow through the outdoor surface.