To enhance heat transfer from a silicon chip, a copper pin fin is brazed to the surface of the chip. The pin length and diameter are L = 12 mm and D = 2 mm, respectively, and atmospheric air at V = 10 m/s and T[infinity] = 300 K is in cross flow over the pin. The surface of the chip, and hence the base of the pin, are maintained at a temperature of Tb = 350 K. (a) Assuming the chip to have a negligible effect on flow over the pin, what is the average convection coefficient for the surface of the pin? (b) Neglecting radiation and assuming the convection coefficient at the pin tip to equal that calculated in part (a), determine the pin heat transfer rate. (c) Plot the effect of increasing velocity (10 ≤ V ≤ 40 m/s) and on the total rate of heat transfer from the chip. (d) Calculate the drag force of the cylinder.

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