The figure shows a Refrigerant-22 vapor-compression refrigeration system with mechanical subcooling. A counterflow heat exchanger subcools a portion of the refrigerant leaving the condenser below the ambient temperature as follows: Saturated liquid exits the condenser at 180 psi. A portion of the flow exiting the condenser is diverted through an expansion valve and passes through the counterflow heat exchanger with no pressure drop, leaving as saturated vapor at 20 °F. The diverted flow is then compressed isentropically to 180 psi and reenters the condenser. The remainder of the flow exiting the condenser passes through the other side of the heat exchanger and exits at 40 °F, 180 psi. The evaporator has a capacity of Qin tons and produces – 20 °F saturated vapor at its exit. In the main compressor, the refrigerant is compressed isentropically to 180 psi.

Problem from Fundamentals of Engineering Thermodynamics, 5th Ed. by Michael J. Moran and Howard N. Shapiro. John Wiley & Sons, Inc. 2004.