Thermodynamic modeling of magnetic hysteresis in AMRR cycles
Abstract Current models of Active Magnetic Regenerative Refrigeration (AMRR) cycles are not able to capture the effect of magnetic hysteresis and are therefore strictly limited to second order magnetic transition (SOMT) materials. The discovery of the giant magnetocaloric effect (GMCE) in first order magnetic transition (FOMT) materials has generated substantial interest. FOMTs yield large adiabatic temperature changes but also exhibit significant magnetic hysteresis. This work quantifies the effects of magnetic hysteresis. Thermodynamically, hysteresis is treated as a source of entropy generation that is proportional to the area swept by the hysteresis loop experienced locally by the material during one refrigeration cycle. The 1-D numerical model presented by Engelbrecht (2008) is modified to include magnetic hysteresis. Hysteresis losses are shown to be directly proportional to regenerator volume. Therefore, at large refrigeration capacity to volume ratios, AMRR beds using layered FOMT materials significantly outperform the same cycle using layered SOMT refrigerants.