Consider a two-stage compression refrigeration system operating between the pressure limits of 1.2 MPa and 0.08 MPa. The working fluid is R-12. The refrigerant leaves the condenser as saturated liquid with a mass flow rate of 1 kg/s and is throttled to a flash chamber operating at 0.4 MPa. Part of the refrigerant evaporates during this flashing process, and this vapor is mixed with the refrigerant leaving the low-pressure compressor. The mixture is then compressed to the condenser pressure by the high-pressure compressor. The liquid in the flash chamber is throttled to the evaporator pressure, and it cools the refrigerated space as it vaporizes in the evaporator. Assuming the refrigerant leaves the evaporator as saturated vapor and both compressors are isentropic, determine
(a) The fraction of the refrigerant that evaporates as it is throttled to the flash chamber,
(b) The amount of heat removed from the refrigerated space,
(c) The net compressor work and
(d) The coefficient of performance.