A well-insulated rigid tank contains 3 kg of saturated liquid-vapor mixture of water at 200 kPa. Initially, three-quarters of the mass is in the liquid phase. An electric resistance heater placed in the tank is now turned on and kept on until all the liquid in the tank is vaporized. Determine the entropy change of the steam during this process. Answer: 11.1 kJ/K

Heat in the amount of 100 kJ is transferred directly from a hot reservoir at 1200 K to a cold reservoir at 600 K. Calculate the entropy change of the two reservoirs and determine if the increase of entropy principle is satisfied.

During the isothermal heat addition process of a Carnot cycle, 900 kJ of heat is added to the working fluid from a source at 400$^\circ{}$C. Determine (a) the entropy change of the working fluid, (b) the entropy change of the source, and (c) the total entropy change for this process.

A well-insulated, rigid tank contains 1.5 kg of Refrigerant 134A, initially a two-phase liquid–vapor mixture with a quality of 60$\%$ and a temperature of $0^{\circ} \mathrm{C}$. An electrical resistor transfers energy to the contents of the tank at a rate of 2 kW until the tank contains only saturated vapor. For the refrigerant, locate the initial and final states on a $T-v$ diagram and determine the time it takes, in s, for the process.

Refrigerant-134a enters the coils of the evaporator of a refrigeration system as a saturated liquid-vapor mixture at a pressure of 140 kPa- The refrigerant absorbs 180 kJ of heat from the cooled space, which is maintained at -10$^\circ{}$C, and leaves as saturated vapor at the same pressure. Determine (a) the entropy change of the refrigerant, (b) the entropy change of the cooled space, and (c) the total entropy change for this process.

An insulated piston-cylinder device contains 0.05 m^3 of saturated refrigerant-134a vapor at 0.8-MPa pressure. 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 and (b) the work done by the refrigerant.