Theoretical comparison of the operation efficiency of two types of magnetic refrigerators working bodies for natural gas liquefaction

The paper compared two different geometries of heat exchangers — working bodies for cryogenic magnetic refrigerators: a stacked plate and a packed bed heat exchanger. Using the similarity theory and unsteady heat flow equations, an operation performance of the heat exchangers based on gadolinium and its R-Gd solid solutions using water and methane as heat transfer media was simulated. It was found that due to the improved dynamics of the heat flux, the spherical packed bed heat exchanger provides a higher heat transfer rate in comparison with a plate regenerator. However, in the case of using water as heat transfer media stacked plate heat exchangers with a plate thickness of 100 mkm exceed the performance of a packed bed heat exchanger by 50% due to a lower porosity and, as a consequence, a larger amount of the magnetocaloric material. In the case of methane, an order of magnitude gain in refrigeration performance is due to the increased speed of the heat-transfer media in the heat exchanger, which makes it possible to efficiently remove all the generated heat from the working body.