1. In space ships, heat rejection to the surroundings is by radiation. A radiator in a space ship has an absorptivity αλ of 0.1 for 0 < λ < 2.5 µm, and 0.95 for λ > 2.5 µm. The surface is maintained at 600 K. What is the net heat flux from the surface when solar irradiation on the surface is 900 W/m2 ? Assume a sky temperature of 0 K, that the surface is diffuse and that the incident solar radiation is normal to the surface.

Acommercial grade cubical freezer, 4 m on a side, has a composite wall consisting of an exterior sheet of 5.0-mm thick plain carbon steel (kst= 60.5 w/m k), an intermediate layer of 100-mm thick polyurethane insulation (kins 0.02 w/m k), and an inner sheet of 5.0- mm thick aluminium alloy (kal polyurethane insulation and both metallic sheets are each characterized by a thermal contact resistance of r 2.5 x 104 m2 k/w. (a) what is the steady-state cooling load that must be maintained by the refrigerator under conditions for which the outer and inner surface temperatures are 25°c and -5°c, respectively? (b) for power saving purpose, which wall material should be increased/reduced in. thickness in order to reduce 50% of the cooling load found in part (a)? redesign the thickness of the proposed material. 177 w/m-k). adhesive interfaces between the q=575.93 w