A cold storage wall (3 m 6 m) is constructed of 15 cm thick concrete (ther- Example 4.8 mal conductivity 1.37 W/[m °C]). Insulation must be provided to maintain a heat transfer rate through the wall at or below 500 W ( Fig. E4.8 ). If the thermal conductivity of the insulation is 0.04 W/(m °C), compute the required thickness of the insulation. The outside surface temperature of the wall is 38°C, and the inside wall temperature is 5°C.