1. If the minimum and maximum allowed refrigerant pressures are 1 and 10 bar, respectively, which of the following can be used as the working fluid in a vapor-compression refrigeration system that maintains a cold region at 08C, while discharging energy by heat transfer to the surrounding air at 308C: Refrigerant 22, Refrigerant 134a, ammonia, propane?
2. Consider the following vapor-compression refrigeration cycle used to maintain a cold region at temperature TC when the ambient temperature is 80°F: Saturated vapor enters the compressor at 15°F below TC, and the compressor operates adiabatically with an isentropic efficiency of 80%. Saturated liquid exits the condenser at 958F. There are no pressure
(a) Refrigerant 134a.
(b) propane.
(c) Refrigerant 22.
(d) ammonia.
The refrigerating efficiency is defined as the ratio of the cycle coefficient of performance to the coefficient of performance of a Carnot refrigeration cycle operating between thermal reservoirs at the ambient temperature and the temperature of the cold region.