Question 16 - A Two-Stage Refrigeration Cycle with a Flash
Chamber
18
MEE 4042 Refrigeration Machines
2022-2023, Spring
Consider a two-stage compression refrigeration system operating between the
pressure limits of 0.8 and 0.14 MPa. The working fluid is refrigerant-134a.The
refrigerant leaves the condenser as a saturated liquid and is throttled to a flash
chamber operating at 0.32 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 cools the refrigerated space as it vaporizes in the evaporator. Assuming
the refrigerant leaves the evaporator as a saturated vapor and both compressors are
isentropic, determine
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 and the compressor work
per unit mass of refrigerant flowing through the condenser, and
(c) the coefficient of performance.