Comparative study on packing arrangement of irregular gadolinium inside active magnetic regenerators in a magnetic refrigeration system

In this study, we investigate two types of active magnetic regenerators (AMRs) including non-aligned and aligned particles of irregular gadolinium and verify their effect on the performance of a magnetic refrigeration system. The aligned AMRs were packed with irregular particles under the external magnetic field to line them up, while the non-aligned AMRs without the magnetic field during their preparation. According to the X-ray computed tomography, the particles were observed to be arranged in parallel to the flow direction in the aligned AMRs whereas they were randomly located in the non-aligned ones. The pressure drop by the aligned AMRs was 18.8 % smaller than that by the non-aligned ones when heat transfer fluid flowed, which was deionized water with 3 vol % of anti-corrosive additive. Moreover, the friction factor for the aligned AMRs was 35.9 % smaller than that for the non-aligned ones on average, which was even 20.5 % lower than the ones with spheres estimated by the Carman correlation. Meanwhile, the coefficient of performance of the aligned AMRs was improved by 37.3 %, 27.3 %, and 10.5 % in 0.56, 0.71, and 1.00 Hz of the nominal operating frequencies in the system with 4.5 K of the temperature span. This enhancement was mainly attributed to the power consumption by the pump which declined by 8.9 %, 16.4 %, and 9.4 % on average at each nominal operating frequency by using the aligned AMRs.

Automated summary

This study investigates the effect of non-aligned and aligned irregular gadolinium particles on the performance of a magnetic refrigeration system. X-ray computed tomography reveals that the aligned particles are arranged in parallel to the flow direction, while the non-aligned particles are randomly located. The aligned particles result in a smaller pressure drop and friction factor compared to the non-aligned ones. Furthermore, the coefficient of performance of the aligned particles is significantly improved at different operating frequencies.