Looking for Energy Losses of a Rotary Permanent Magnet Magnetic Refrigerator to Optimize Its Performances

Abstract

In this paper, an extensive study on the energy losses of a magnetic refrigerator prototype developed at University of Salerno, named ‘8MAG’, is carried out with the aim to improve the performance of such a system. The design details of ‘8MAG’ evidences both mechanical and thermal losses, which are mainly attributed to the eddy currents generation into the support of the regenerators (magnetocaloric wheel) and the parasitic heat load of the rotary valve. The latter component is fundamental since it imparts the direction of the heat transfer fluid distribution through the regenerators and it serves as a drive shaft for the magnetic assembly. The energy losses concerning eddy currents and parasitic heat load are evaluated by two uncoupled models, which are validated by experimental data obtained with different operating conditions. Then, the achievable coefficient of performance (COP) improvements of ‘8MAG’ are estimated, showing that reducing eddy currents generation (by changing the material of the magnetocaloric wheel) and the parasitic heat load (enhancing the insulation of the rotary valve) can lead to increase the COP from 2.5 to 2.8 (+12.0%) and 3.0 (+20%), respectively, and to 3.3 (+32%), combining both improvements, with an hot source temperature of 22 °C and 2 K of temperature span.

Giant Low-Field Magnetocaloric Effect in the Superlattice Antiferromagnetic ErFe2Si2 Compound

“…It should be noted that the magnetic entropy change under low-field variation, for example 0–1 T, has a greater reference significance for practical applications. On one hand, the maximum magnetic field used in magnetic refrigerators is usually no more than 1.5 T. − On the other hand, though it is true that the applied magnetic field at low temperatures may be quite large based on superconductors, the magnetic refrigerant materials with a large low-field MCE are still important because they can lower the cost. Although the (−Δ S M ) max of ErFe 2 Si 2 is smaller than those of HoCuSi, HoCuAl, and GdCoC 2 under a field change of 0–5 T, ErFe 2 Si 2 shows a larger (−Δ S M ) max than these compounds under a field change of 0–1 T. It means that ErFe 2 Si 2 exhibits a giant low-field MCE.…”

Investigation on the regenerative Brayton refrigeration cycle performances using novel Mn-Fe-P-Si composite material with thermal hysteresis as the working medium

“…Huang et al (2019) developed a rotary active magnetic regeneration refrigerator prototype for studying the performance of different magnetocaloric materials in a realistic practical environment. Maiorino et al (2019) analyzed the optimal working performance of magnetic refrigerators. Kamran et al (2020) used performance evaluation method to estimate the developments of active magnetic regenerative refrigerators.…”