Numerical simulation of a fully solid-state micro-unit regeneration magnetic refrigerator with micro Peltier elements

As an alternative to the vapor-compression technology, magnetic refrigeration has been an active area of research in recent years. A serious obstacle faced by existing magnetic refrigeration prototypes is the use of a heat-transfer fluid, which may result in high irreversible losses, large pressure drops and complex fluid circuits. Solid-state magnetic refrigeration has been investigated as a potential solution. For our previously proposed solid-state micro-unit regeneration magnetic refrigerator, the special three-dimensional structure design allows the heat to be regenerated at a small temperature difference. It is note-worthy that a three-dimensional numerical simulation is necessary for analysing the internal heat transfer characteristic and revealing the operation parameters matching rule of micro-unit regeneration cycle. Therefore, in this work a three-dimensional solid-state magnetic refrigerator based on micro-unit regeneration cycle and Peltier elements is modelled in detail. Multiple micro Peltier (9506-063-022M) modules are coupled with a system to enhance the heat regeneration between the magnetocaloric material lattices. The reliability of the model, in parts and in whole, is verified by experimental data. The heat transfer process and performance characteristics are carefully compared and discussed for several configurations, including the system with/without Peltier elements, two types of lattice heat-transfer structures, different Peltier's input voltages, and different required times for rotation per lattice. The results show that a larger temperature span and higher frequency are obtained when coupled with Peltier elements. Meanwhile, the parallel-plate heat transfer structure of the magnetocaloric material lattice further improves the performance of the system. The optimal system performance is simultaneously determined by the input voltage and rotating speed. Using gadolinium as a magnetocaloric material and in the case of a 0.7 T applied magnetic field, a maximum temperature span of 32 K, an optimal coefficient of performance of 5.45, and a maximum specific cooling power of 252.5 W/kg can be achieved in such a fully solid-state micro-unit regeneration magnetic refrigeration system. The simulation results can serve as guidelines for solid-state magnetic refrigerator design and optimisation.

Automated summary

This study investigates a three-dimensional solid-state magnetic refrigerator based on micro-unit regeneration cycle and Peltier elements, and verifies the reliability of the model with experimental data. The comparison of heat transfer processes and performance characteristics under different configurations reveals that coupling with Peltier elements increases temperature span and frequency, while the parallel-plate heat transfer structure of the magnetocaloric material lattice enhances system performance.