In a vapor-compression refrigeration cycle, R-134a exits the evaporator as saturated vapor at 20lbf/in2. The refrigerant enters the condenser at 160 lbf/in2 and 140?F, and then exits as a saturated liquid at the same pressure. There is no significant heat transfer between the compressor and its surroundings, and the refrigerant passes through the evaporator with a negligible change in pressure. If the refrigerant capacity is five tons, determine:
a) The mass flow rate of refrigerant, in lbm/min
b) The power input to the compressor in Btu/min
c) The coefficient of performance
d) The isentropic compressor efficiency