A numerical study on the unsteady heat transfer in active regenerator with multi-layer refrigerants of rotary magnetic refrigerator near room temperature

Abstract As the temperature span(△T) of a refrigerator with an active magnetic regenerator(AMR) of single magneto-caloric material is limited, in the current investigation, the multi-layer AMR consisting of Gd and Gd 0.73 Tb 0.27 is studied to improve the refrigeration performance at a larger △T with the numerical method, where the experimental magneto-caloric properties are adopted for a better precision. Effects of Gd 0.73 Tb 0.27 content (φ) and fluid flowrate (q V ) on refrigeration capacity (q ref,V ) and coefficient of performance (COP), together with those of hot and cold reservoir temperatures (T c and T h ), are investigated. Besides, temperature contours of fluid and solid matrix are presented for discussions. The present study demonstrates that compared with AMR of pure Gd, the multi-layer AMR improves the q ref,V and COP by ～167% and 57% at △T = 28K, respectively. Moreover, it is observed that q ref,V of multi-layer AMR has a convex variation tendency with φ, and the maximum at T c of 268K equals 874.7 kW/m 3 . As a contrast, COP has two peaks, and the optimal φ is almost independent of T c , while it decreases with a rising T h . In addition, current investigation indicates that q ref,V takes a lager value at a larger q V , while a smaller q V facilitates a good COP.