Improved cooling capacity of a magnetic refrigeration system using milled gadolinium chips

This study confirmed that material milling can enhance the cooling capacity of a magnetic refrigeration system while maintaining the existing system configuration. The system exploited active magnetic regenerators filled with gadolinium chips, and the experimental results were compared when using milled and non-milled chips. The non-milled case was called a base case, and the milled cases were separated into two types to distinguish the effect of increased mass of material as the porosity decreased after milling: One was a 24.8 % greater mass case, and the other was the same mass case as the base case. The milled case with a larger mass achieved the highest temperature span under no-load conditions at all operating temperatures due to the extra mass. When the charged amounts were the same, the temperature spans were similar regardless of the particle shape. Under load conditions, the cooling capacity was also significantly boosted by 28.6 % to 2.25 W in the milled case with a greater mass, compared to the base case. Notably, the coefficient of performance remained similar thanks to the reduced friction factor, mitigating the rise in power consumption. A 30.4 % higher sphericity played a key role in alleviating the friction factor after milling.