Performance study of dual-layer active magnetic regenerators with different filling ratios in the room temperature magnetic refrigerator

Magnetic refrigeration technology is a solid-state cooling technology based on the magnetocaloric effect and possesses significant potential to replace vapor compression cooling technology. However, current magnetic refrigeration systems remain less competitive compared to vapor compression systems in terms of both cooling power density and energy efficiency. Employing a layered regenerator with magnetocaloric materials of different Curie temperatures is one of the promising strategies to improve the performance of magnetic refrigeration systems. Four regenerators composed of a packed bed of 0.36 mm - 0.60 mm Gd and Gd₉₄Er₆ spheres were constructed in this paper. The filling ratios were 1:0, 8:2, 6:4, and 4:6 (Gd: Gd₉₄Er₆) respectively. Based on the previous magnetic refrigerator, the performance of four regenerators was evaluated for different operating conditions, which based on the temperature span with zero thermal load, cooling capacity, magnet power consumption, and COP. Experimental results indicate that the regenerator with a filling ratio of 6:4 exhibited optimal temperature span performance under all tested conditions. When operated at 1 Hz frequency, 0.6 utilization factor, and 30 °C hot-side temperature, it achieved a maximum temperature span of 22.7 K with zero thermal load. The magnet power consumption decreases as the filling ratio of Gd₉₄Er₆ increases. In consideration of COP values, single-layer Gd regenerator and those with filling ratios of 8:2 and 6:4 perform similarly at a 5 K temperature span, but the regenerator with a 6:4 filling ratio outperforms at spans over 15 K.