A two stage refrigeration cycle is shown in fig. B. The working fluid is refrigerant 134a. The interchanger is a heat exchanger where the heat absorbed by the refrigerant in the higher-temperature cycle 2 serves to condense the refrigerant in the lower-temperature cycle 1. The refrigerant in cycle 1/2 leaves the interchanger as saturated liquid/vapor. The corresponding temperatures of saturation are 5.12 ℉ / 0 ℉. The saturation temperature in the evaporator is -40 ℉. The pressure in the condenser is 60 psia. The compressor in cycle 1 operates isentropically. The compressor in cycle 2 has an isentropic efficiency of 80%. (a) Sketch the cycle in a T-s diagram and determine the enthalpy at each point of the cycle. (b) Calculate the ratio of the mass flow rates of the refrigerant in the two cycles. (c) Calculate the coefficient of performance of this refrigeration cycle.
A two stage refrigeration cycle is shown in fig. B. The working fluid is refrigerant 134a. The interchanger is a heat exchanger where the heat absorbed by the refrigerant in the higher-temperature cycle 2 serves to condense the refrigerant in the lower-temperature cycle 1. The refrigerant in cycle 1/2 leaves the interchanger as saturated liquid/vapor. The corresponding temperatures of saturation are 5.12 ℉ / 0 ℉. The saturation temperature in the evaporator is -40 ℉. The pressure in the condenser is 60 psia. The compressor in cycle 1 operates isentropically. The compressor in cycle 2 has an isentropic efficiency of 80%.
(a) Sketch the cycle in a T-s diagram and determine the enthalpy at each point of the cycle.
(b) Calculate the ratio of the mass flow rates of the refrigerant in the two cycles.
(c) Calculate the coefficient of performance of this refrigeration cycle.
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