Gas contained in a piston-cylinder assembly undergoes a polytropic process for which the relation between pressure and volume is given by p∀ n = constant. the initial volume is 0.04 m3 and the initial pressure is 2 bar. the final volume of the gas is 0.1 m3 , for each of the following cases, determine the final pressure [bar] and the work for the process [kj]. show integration for each case. a. n = 0, b. n = 1, c. n = 1.4.

Air is to be cooled in the evaporator section of a refrigerator by passing it over a bank of 0.8-cm-outer-diameter and 0.4-m-long tubes inside which the refrigerant is evaporating at -20°c. air approaches the tube bank in the normal direction at 0°c and 1 atm with a mean velocity of 4 m/s. the tubes are arranged in-line with longitudinal and transverse pitches of sl- st 1.5 cm. there are 30 rows in the flow direction with 15 tubes in each row. determine (a) the refrigeration capacity of this system and (b) pressure drop across the tube bank. evaluate the air properties at an assumed mean temperature of -5°c and 1 atm. is this a good assumption?