A cold-storage room is maintained at -18°C. The internal dimensions of the room are 5 m x 5 m x 3 m high. Each wall consists of an inner layer of 2.5-cm-thick wood with 7-cm-thick insulation and a 1 cm brick layer on the outside. The thermal conductivities of respective materials are wood (0.104 W/mK), glass fiber (0.04 W/mK), and brick 0.69 W/mK. The convective heat-transfer coefficient for wood to still air is 2.5 W/m K, and from moving air to brick is 4 W/mK. The outside ambient temperature, is 25 °C. Determine:
(a) The overall heat transfer coefficient.
(b) The temperature of the exposed surfaces.
(c) The temperatures of the interfaces.