Air at 2.5 bar, 400 K is extracted from a main jet enginecompressor for cabin cooling. The extracted air enters a heatexchanger where it is cooled at constant pressure to 325 Kthrough heat transfer with the ambient. It then expandsadiabatically to 1.0 bar through a turbine and is dischargedinto the cabin. The turbine has an isentropic efficiency of80%. If the mass flow rate of the air is 2.0 kg/s, determine(a) the power developed by the turbine, in kW.(b) the rate of heat transfer from the air to the ambient, in kW.

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