60∼80 K 温区主动磁回热器性能影响因子的数值模拟研究

In this paper, based on the multi-stage active magnetic refrigeration process from liquid nitrogen temperature to liquid hydrogen temperature, a two-dimensional transient active magnetic regenerator model in the temperature range of 60∼80 K has been built by means of COMSOL Multiphysics 5.5. And the simulation optimization research of ideal and real magnetocaloric materials was carried out. First, based on the ideal magnetocaloric material with magnetic entropy change of 5.4 J•kg^-1•K^-1, the effects of various factors in the regenerator on the performance of magnetic refrigeration were compared and analyzed, including the particle diameter of the magnetocaloric material, the regenerator aspect ratio, and filling quality of magnetocaloric material. The simulation results showed that the cooling power of the active magnetic regenerator decreased with the increase of the particle diameter of the magnetocaloric material (0.2∼0.7 mm). Furthermore, as the mass flow rate of helium increased (2∼18 g•s^-1), the optimal particle diameter of the active magnetic regenerator decreased; With the increase of regenerator aspect ratio, the cooling power gradually increased, and a greater COP was achieved when the regenerator aspect ratio was 5; The relationship between the maximum cooling power of the active magnetic regenerator and the filling quality of magnetocaloric material increases linearly. Then, based on the optimized geometric parameters (particle diameter was 0.4 mm and aspect ratio was 5), the performance of the active magnetic regenerator filled with real magnetocaloric materials DyFeSi was studied. When the mass flow rate was 4.5 g•s^-1, the active magnetic regenerator obtained the maximum cooling power of 1.5 W, and the corresponding second thermodynamic efficiency was 28.67%. Although it was difficult for a kind of real magnetocaloric material to obtain better cooling power and cooling efficiency in the temperature range of 60∼80 K, the research carried out in this paper has important reference value and guiding significance for the multi-layer structure design of high-temperature stage active magnetic regenerator.