) A diffuser takes in 2.5 kg s−1 of air at 52 ◦C and 12 bar through an inlet of 4 cm. It discharges through an outlet of 12 cm diameter at 10 bar and 152 ◦C. The diffuser is heated. Determine inlet and outlet velocities, the change in enthalpy that occurs, and the heat gain. Assume air is an ideal gas. [155 m s−1 , 27.0 m s−1 , −11.5 kJ kg−1 ]

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