Conduction: A concrete wall of a cold storage room measures 3.0 m high, 5.0 m wide, and 20 cm thick. The inside wall is to be covered by a layer of wood in order to reduce the rate of heat flow through the wall by 90 percent. The inner surface of the wooden wall is maintained at -10°C and the outer surface of the concrete wall is at 20°C. The thermal conductivities of concrete and wood are 0.80 W/m ? K (concrete) and 0.040 W/m ? K (wood). What is the temperature difference across the layer of wood?
A. 24 C°
B. 25 C°
C. 26 C°
D. 27 C°
E. 28 C°
Answer: D
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