Comparative study on the series, parallel and cascade cycles of a multi-mode room temperature magnetic refrigeration system

Abstract

Abstract Magnetic refrigeration has been investigated as an appropriate alternative for vapor-compression refrigeration to reduce the greenhouse effect. However, the commercialization process of MR is obstructed by the inadequate cooling condition. In this paper, a multi-mode MR system with series, parallel and cascade cycle modes is constructed. The optimal utilization factors, internal cycle mechanisms and refrigeration characteristics of three modes are compared. The magnetocaloric material used is 277.4 g of gadolinium, and two NbFeB permanent magnets are assembled to provide a maximum magnetic field intensity of 1.5 T. The results show that different modes affect the MR system performance. The series mode increases the temperature span by increasing the length of the regeneration zone. The parallel mode improves the cooling power owing to the simultaneous output of double regenerators. The novel cascade cycle constructs the higher- and lower- temperature regeneration stages, which are effectively utilized to provide a large temperature span and suitable cooling power. The obtained no-load temperature spans are 5.66 K, 4.16 K and 7.35 K in the series, parallel and cascade cycles, respectively, and the corresponding maximum specific cooling powers are 29.02, 39.47 and 34.79 W/kg. Compared with the parallel mode, the cycle characteristics of the series and cascade modes receive a greater degree of investigation. The series mode shows a larger potential for large-temperature-span output system, and the cascade cycle is most likely to meet both the temperature span and cooling power output requirements simultaneously. The results provide some guidelines for the design of magnetic refrigeration prototypes.