On a cold winter day, the outer surface of a 0.2-m-thick concrete wall of a warehouse is exposed to a temperature of –5°C, while the inner surface is kept at 20°C. The thermal conductivity of the concrete is 1.2 W/(m K). Determine the heat loss through the wall, which is 10-m long and 3-m high.

Question

GIVEN

10 m long, 3 m high, and 0.2 m thick concrete wall

Thermal conductivity of the concrete (k) = 1.2 W/(m K)

Temperature of the inner surface (Ti) = 20°C

Temperature of the outer surface (To) = –5°C

FIND

The heat loss through the wall (qk)

ASSUMPTIONS

One dimensional heat flow

The system has reached steady state

SKETCH

Answer 1

The rate of heat loss through the wall is given;