Effect of thermal cut-off frequency on the maximum efficiency of electro-permanent-magnet magnetocaloric cooling

Abstract Magnetocaloric cooling is a refrigerant-free alternative to vapor-compression systems, but rotating-magnet demonstrators are typically limited to about 15 Hz. Prior electro-permanent-magnet (EPM) studies demonstrated efficient high-frequency field sources, but did not determine whether this field-source advantage remains at cooler-system level when the magnetocaloric material, useful cooling power, Carnot work, hysteresis losses, cycle losses, electromagnetic losses, and finite heat extraction are evaluated in one coefficient of performance (COP) framework. This purely simulation-based study addresses that gap for a LaFeSi-based magnetocaloric device by coupling a 2D COMSOL electromagnetic model with post-processing for the first-order thermal low-pass response of the magnetocaloric elements. This avoids full coupled thermo-fluid simulation while retaining the thermal cut-off frequency that limits heat extraction. The model yields losses and useful cooling energy across 1–50 Hz for a field change of at least about 1 T, and the relative COP is evaluated for cut-off frequencies from 4 to 40 Hz while varying sample length and winding area. The maximum relative COP reaches 53.22% at 40 Hz cut-off with a 177.85 cm {}² winding area as a model-based upper-bound estimate, and efficiencies above 50% are achieved at 16 Hz system frequency. Efficiency first increases with frequency, then an optimal operating point emerges; beyond that point the thermal time constant limits heat transfer and the COP declines. These results show that EPM magnetocaloric systems can reach efficiencies comparable to conventional heat pumps only when the magnetic field source and magnetocaloric heat-extraction limits are optimized together.