A refrigeration system like the one shown in the figure, in cascade uses R-22 refrigerant in the low temperature part of the system (B) and 134a refrigerant in the high temperature circuit (A). The R-22 refrigerant circuit operates between 1.1 and 5 bar. The enthalpies of the saturated vapor that leaves the evaporator at -39 ºC, of the superheated vapor that leaves the isentropic compressor at 29 ºC, and of the liquid that enters the throttling device at 0 ºC are 267.37; 304.16 and 78.47 respectively. The ideal cycle of the refrigerant circuit 134a operates between -12 ° C and 9 bar. The cooling capacity of the low temperature evaporator is 5 Ton. The COP of the cascade system is 2.13. Determine: a) the mass flows, in Kg / hr, in the two circuits. b) the input power in both compressors, in Kw c) Also determine the COP of a cycle with a single circuit using refrigerant 134a between -40 ºC and 9 bar.
A refrigeration system like the one shown in the figure, in cascade uses R-22 refrigerant in the low temperature part of the system (B) and 134a refrigerant in the high temperature circuit (A). The R-22 refrigerant circuit operates between 1.1 and 5 bar.
The enthalpies of the saturated vapor that leaves the evaporator at -39 ºC, of the superheated vapor that leaves the isentropic compressor at 29 ºC, and of the liquid that enters the throttling device at 0 ºC are 267.37; 304.16 and 78.47 respectively.
The ideal cycle of the refrigerant circuit 134a operates between -12 ° C and 9 bar. The cooling capacity of the low temperature evaporator is 5 Ton. The COP of the cascade system is 2.13.
Determine:
a) the mass flows, in Kg / hr, in the two circuits.
b) the input power in both compressors, in Kw
c) Also determine the COP of a cycle with a single circuit using refrigerant 134a between -40 ºC and 9 bar.
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