Apiston-cylinder device initially contains 1.39 l of air at 100 kpa and 25°c. the air is now compressed to a final state of 725 kpa and 150°c. the useful work input is 1.57 kj assuming the surroundings are at 100 kpa and 25°c, determine (a) the exergy of the air at the initial and the final states, x2=0.3090979kj (b) the minimum work that must be supplied to accomplish this compression process, kj wmin 0.309097 and (c) the second-law efficiency of this process η =119.687766

A2-m rigid tank initially contains saturated water vapor at 100 kpa. the tank is connected to a supply line through a valve. steam is flowing in the supply line at 600 kpa and 300 c. the valve is opened, and steam is allowed to enter the tank until the pressure in the tank reaches the line pressure, at which point the valve is closed. a thermometer placed in the tank indicates that the temperature at the final state is 200°c. determine (a) the mass of steam that has entered the tank (b) the amount of heat transfer.