Apiston-cylinder device initially refrigerant-134a at 100 kpa and 20°c. heat is now trans- ferred to the refrigerant from a source at 150°c, and the pis- ton which is resting on a set of stops, starts moving when the pressure inside reaches 120 kpa. heat transfer continues unti the temperature reaches 80°c. assuming the surroundings to be at 25°c and 100 kpa, determine (a) the work done, (b) the 8 heat transfer, (c) the exergy destroyed, and (d) the second-law efficiency of this process.

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