Question

A 0.2 m3 piston-cylinder initially contains 400 K air. A heavy frictionless piston maintains a pressure of 500 kPa abs. Then, a weakness in the cylinder wall blows out and creates a hole. Air escapes through the hole until the piston drops far enough to cover the hole. At that point, the volume is half the initial volume. During this process, 75 kJ of heat is transferred to the 100 kPa, 300 K surroundings. Using Cp = 1.005 kJ/kg-K and Cv = 0.718 kJ/kg-K, find (a) final temperature - K, (b) mass leaving the cylinder - kg, (c) work - kJ, (d) total entropy change - kJ/K. Assume the enthalpy of the exiting air is that of air at the average of the initial and final temperatures.

Answer 1