An ideal gas initially occupying 0.020 m3 at 1.0 MPa is quasistatically expanded inside a piston-cylinder device at a constant pressure until its volume doubles. Next the expansion is continued at constant volume till the pressure reaches half of the initial pressure. Finally it is brought back to the initial state in a polytropic process with exponent n=1.6 a. Draw the processes on a P-v diagram and calculate the total work.
b. Calculate the total heat transfered, what is the difference between the initial and final temperature?

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?