Heat-transfer effect on the performance of a magnetic Ericsson refrigerator

The irreversibilities resulting from the finite-rate heat transfer between the working substance and the external heat reservoirs and the regenerative losses in regenerative processes are considered in the cycle model of a magnetic Ericsson refrigerator. The fundamental optimum relations between the cooling rate and the coefficient of performance and between the power input and the coefficient of performance are derived, based on a class of heat-transfer laws and the Curie law. The general characteristic curves of the cycle are presented. The effect of the different forms of the regenerative time and heat-transfer laws on the performance of the cycle is discussed in detail. The results obtained here will be useful to further understand the general optimum performance of real magnetic Ericsson refrigerators.