Impact of the initial field on the thermodynamic performance of room-temperature magnetic refrigeration cycle

The thermodynamic cycle performance of Gadolinium (Gd) and Gd0.87Dy0.13 used as the working substance in regeneration magnetic Brayton and Ericsson refrigeration cycles are investigated under different external magnetic field conditions. Based on the experimental iso-field heat capacities of Gd with different magnetic fields, the effects of magnetic field change on thermodynamic performances including the magnetic entropy change, cooling quantity, non-perfect regeneration, net cooling quantity, and coefficient of performance (COP) are analyzed and discussed. The present work shows the possibility of reducing the regenerative losses and thereby improving the net cooling quantity for a given field change by selecting optimal initial and final magnetic field values. The similar analysis and calculation of the related thermodynamic performances are further applied to the magnetic material Gd0.87Dy0.13 which exhibits better net cooling quantities when compared to Gd at low temperature.