A cold-storage room wall is to be lined with a layer of cork insulation
PHYSICS · Subjective · A Level · Physics · Further mechanics and thermal physics · Further mechanics and thermal physics
Problem
A cold-storage room wall is to be lined with a layer of cork insulation.
The inside surface of the wall is maintained at −5 °C and the outside surface at 25 °C. The wall area to be insulated is 15 m².
To ensure economical operation, the heat entering the room through this wall must not exceed 270 W.
The thermal conductivity of cork is 0.040 W·m⁻¹·K⁻¹.
(a) Write the relation connecting the rate of heat flow with the relevant physical quantities for steady conduction through a plane slab.
(b) Calculate the minimum thickness of cork that must be provided so that the heat flow limit is not breached.
(c) If, due to construction constraints, only half of the thickness calculated in part (b) can be used, determine the new rate of heat flow into the room and comment on whether it satisfies the design requirement.