A pistoncylinder assembly contains saturated water vapor at

A piston-cylinder assembly contains saturated water vapor at T = 200 C. The O surrounding air is at 35 C. Heat transfer occurs from the system until the cylinder O contains saturated liquid water at T = 200 C. Can this process be modeled as a reversible O process? an internally reversible process? Explain the reasons behind your answers.

Solution

Entropy change for reversible process is zero.

whereas in this case entropy change can be obtained from steam tables. Corresponding to staurated temperature of 200 C, S_g - S_f will be the entropy change, which is positive. Hence, not a reversible process.