### Refrigeration Truck White Paper

The roof of a refrigerated truck compartment is of composite construction, consisting of a layer of foamed urethane insulation (t_{2} = 50 mm, k_{i} = 0.026 W/m ∙ K sandwiched between aluminum alloy panels (11 = 5 mm, kp = 180 W/m ∙ K). The length and width of the roof are L = 10 m and W = 3.5 m, respectively, and the temperature of the inner surface is T_{s,i} = – 10°C. Consider conditions for which the truck is moving at a speed of V= 105 km/h, the air temperature is T_{∞} = 32°C, and the solar irradiation is G_{s} = 750 W/m^{2}. Turbulent flow mil) be assumed over the entire length of the roof.

(a) For equivalent values of the solar absorptivity and the emissivity of the outer surface (as = 8 = 0.5), estimate the average temperature T_{s,o} of the outer surface. What is the corresponding heat load imposed on the refrigeration system? (b) A special finish (*a*_{s} = 0.15, ε = 0.8) may be applied to the outer surface. What effect would such an application have on the surface temperature and the heat load? (c) If, with *a*_{s} = ε = 0.5, the roof is not insulated (12 = 0), what are the corresponding values of the surface temperature and the heat load? ** SOLUTION:**