Moran and Shapiro, Problem 3.23 and 3.39, modified. Two kg of Refrigerant 134a undergoes a polytropic process (p×Vn = constant) in a piston-cylinder assembly from an initial state of saturated vapor at 2 bar to a final state of 12 bar, 80 C. Determine the work for the process. Also, determine the heat transfer that must occur, in kJ. Hint: You will have to determine the polytropic exponent n. Repeat your calculations if the final state is, instead, 12 bar and saturated vapor. The polytropic exponent n will be different, of course

Heat is added to a piston-cylinder device filled with 2 kg of air to raise its temperature 400 c from an initial temperature of t1 27 cand pressure of pi 1 mpa. the process is isobaric process. find a)-the final pressure p2 b)-the heat transfer to the air.

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?

The higher the astm grain size number, the finer the gran is. a)-true b)-false