Improving magnetic refrigerator performances by enhancing convection heat transfer with staggered twin-wedged elements

The room-temperature magnetic refrigerator with the magneto-caloric materials of long Gd plates was simulated in our previous investigation. In the present work, the Gd materials are processed into the twin-wedged shape to improve refrigerator performances. The numerical simulation with the Fluent is performed for the novel refrigerator and the performance comparison between the refrigerators with long Gd plates and twin-wedged elements is conducted. Besides, the influences of longitudinal element pitch (s), cycling period (τ) and relative fluid displacement (φ) on refrigerator behaviors are studied. Moreover, the velocity vector and temperature contours are presented to understand the operation principle of refrigerator. In addition, the thermo-hydraulic performances of twin-wedged elements are predicted for discussing the enhancement of refrigeration performances. The numerical results indicate that the proposed elements could effectively enhance the convective heat transfer rate under weak laminar flow conditions and thus notably improve the specific refrigeration capacity (qV,ref), maximal refrigeration temperature span and Coefficient of Performance of refrigerators. Besides, the above three performances are found to vary convexly with the increment of τ or φ and the maximal qV,ref of 284.9 kW/m3 is obtained at the condition of smallest s(=1 mm) and τ(=0.25 s) together with moderate φ(=0.2) for all present cases.