Physics

Problem

The ceiling of a cold storage room has an area of

4.0\,\text{m}^2

. The temperature difference between the inner and outer surfaces is expected to remain about

25\,\text{K}

. The heat gain through the ceiling must not exceed

80\,\text{W}

. Three insulating boards are available: Board A:

k = 0.040\,\text{W m}^{-1}\,\text{K}^{-1}

Board B:

k = 0.060\,\text{W m}^{-1}\,\text{K}^{-1}

Board C:

k = 0.080\,\text{W m}^{-1}\,\text{K}^{-1}

a. (i) For each board, calculate the maximum permissible thickness that will satisfy the heat-gain limit. b. (ii) Which board allows the thinnest ceiling? State its required thickness.

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