Review and comparison of magnet designs for magnetic refrigeration

Abstract

One of the key issues in magnetic refrigeration is generating the magnetic field that the magnetocaloric material must be subjected to. The magnet constitutes a major part of the expense of a complete magnetic refrigeration system and a large effort should therefore be invested in improving the magnet design. A detailed analysis of the efficiency of different published permanent magnet designs used in magnetic refrigeration applications is presented in this paper. Each design is analyzed based on the generated magnetic flux density, the volume of the region where this flux is generated and the amount of magnet material used. This is done by characterizing each design by a figure of merit magnet design efficiency parameter, Λ cool . The designs are then compared and the best design found. Finally recommendations for designing the ideal magnet design are presented based on the analysis of the reviewed designs.

Optimally Segmented Permanent Magnet Structures

“…We apply a constraint on the total volume of magnet material, which is equal to 5 times the volume of the high field region. This ratio is comparable to other published designs of magnetic refrigeration devices [24].…”

Design and Fabrication of 2-T Rotating Halbach Magnet for Magnetic Refrigerator

“…These refrigeration processes are very similar those that occur in a conventional refrigeration by cyclic compression and expansion of a gas [2]. The entropy change of numerous magnetocaloric materials scales as a power law with an exponent that generallỹ 2/3 [3][4][5]. As a source of the magnetic field for the magnetic refrigerator, permanent magnets are preferred because they do not require power to generate a magnetic field, so and only mechanical energy is required to move the magnet or the active material [5,6].…”

The influence of demagnetizing effects on the performance of active magnetic regenerators

“…The values are chosen partly from a practical aspect (such as realistic limits to magnetic field gaps in permanent magnets 15 and plate dimensions 16 ) and partly from a theoretical aspect where relevant temperature spans, AMR operating frequencies and thermal utilization are considered.…”