A refrigerator door has a height and width of H = 1 m and W = 0.65 m, respectively, and is situated in a large room for which the air and walls are at T∞ = Tsur = 25°C. The door consists of a layer of polystyrene insulation (k = 0.03 W/m ∙ K) sandwiched between thin sheets of steel (s = 0.6) and polypropylene. Under normal operating conditions, the inner surface of the door is maintained at a fixed temperature of Ts,i = 5°C.

(a) Estimate the heat gain through the door for the worst case condition corresponding to no insulation (L = 0).

(b) Compute and plot the heat gain and the outer surface temperature Ts. v as a function of insulation thickness for 0

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Air, T Refrigerator compartment Polypropylene surface, Surroundings, Tur Steel surface, Insulation,-