A two-stage refrigerating system is operating between the pressure limits of 8 bar and 1.4 bar. The working fluid is R134a. The refrigerant leaves the condenser as a saturated liquid and is throttled to a flash chamber operating at 3.2 bar. The part of the refrigerant evaporates during the flashing process and this vapour 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 evaporates in the evaporator. Assuming the refrigerant leaves the evaporator as a saturated vapour and both compressions 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 and the compressor work per unit mass of refrigerant flowing through the condenser, and (c) the coefficient of performance.
A two-stage refrigerating system is operating between the pressure limits of 8 bar and 1.4 bar.
The working fluid is R134a. The refrigerant leaves the condenser as a saturated liquid and is
throttled to a flash chamber operating at 3.2 bar. The part of the refrigerant evaporates during
the flashing process and this vapour 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 evaporates in the evaporator. Assuming the refrigerant leaves the
evaporator as a saturated vapour and both compressions 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 and the compressor work per unit
mass of refrigerant flowing through the condenser, and
(c) the coefficient of performance.
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