Describe with the help of a neat diagram the working of a vapor-compression refrigeration plant. Sketch the corresponding temperature-entropy and pressure-enthalpy diagrams indicating the directions of the various processes. Establish the expressions for the coefficients of performance when the plant is operated as a refrigerator and as a heat pump. How do superheating of the vapor at the entrance to the compressor and sub-cooling of the liquid at the entrance of the throttle valve as also the frictional losses in the compressor affect the performance of the machine? Indicate these effects on the T-s and the p-h diagrams.