Finite Time Thermodynamics of Cascaded Refrigeration and Heat Pump Cycles

Abstract

The conventional vapour compression refrigeration systems cannot be effectively used for low-temperature applications because the power consumed by the compressor is largely increased, and hence for low-temperature applicatireservoir and cycle-I working fluid, cycon, a cng the analysis of refrigeration/heat pump cyascaded refrigeration system is used. For finding the optimum performance of cascaded systems, we are applying Lagrangian multiplier method in which power input to the system is minimized at given cooling/heating load condition. This optimization method has been made for single stage irreversible airconditioning/heat pump system in earlier Chap. 7. Now similar analysis is being extended for cascaded (double stage) refrigeration/heat pump system, and a comparison of cascaded and single stage refrigeration/heat pump systems is being made in this chapter. The performance of a cascaded endoreversible/irreversible Carnot refrigeration/heat pump cycle is somewhat different from that of a single stage one, because there are changes in the irreversible losses when endoreversible/irreversible refrigeration/heat pump cycles are combined. For reversible refrigeration/heat pump cycles, irreversible loss does not exist, and so there is no change of such loss when reversible cycles are combined.