A vapor-compression refrigeration system is conventional except that a countercurrent heat exchanger is installed to subcool the liquid from the condenser by heat exchange with the vapor stream from the evaporator. The minimum temperature difference for heat transfer is 10 F. Tetrafluoroethane is the refrigerant evaporating at 20 F and condensing at 80 F. The heat load on the evaporator is 2000 BTU/s. If the compressor efficiency is 75%, what is the power requirement? How does this result compare with the power required by the compressor if the system operates without a heat exchanger? How do the refrigerant circulation rates compare for the two cases?