A rigid tank contains an ideal gas at 40 C that is being stirred by a paddle wheel. The paddle wheel does 200 kJ of work on the ideal gas. It is observed that the temperature of the ideal gas remains constant during this process as a result of heat transfer between the system and the surroundings at 30 C. Determine the entropy change of the ideal gas. An: 0 2) An insulated piston-cylinder device contains 0.05 m3 of saturated R-134a vapor at 0.8 MPa. The refrigerant is now allowed to expand in a reversible manner until the pressure drops to 0.4 MPa. Determine (a) the final temperature in the cylinder, (b) the work done by the refrigerant. Ans: (a) 8.91 C and (b) 27.09 kJ 3) R-134a enters an adiabatic compressor as saturated vapor at 160 kPa at a rate of 2 m3/min and is compressed to a pressure of 900 kPa. Determine the minimum power that must be supplied to the compressor.
