Ideal magnetocaloric effect for active magnetic regenerators

The active magnetic regenerator (AMR) uses a magnetic solid as a thermal storage medium and as a working material in a refrigeration cycle. Thermodynamically coupled to a heat transfer fluid, the regenerator produces a cooling effect and generates a temperature gradient across the AMR. The coupling...

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Bibliographic Details
Published in:Journal of applied physics 2003-02, Vol.93 (3), p.1672-1676
Main Authors: Rowe, A. M., Barclay, J. A.
Format: Article
Language:English
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Summary:The active magnetic regenerator (AMR) uses a magnetic solid as a thermal storage medium and as a working material in a refrigeration cycle. Thermodynamically coupled to a heat transfer fluid, the regenerator produces a cooling effect and generates a temperature gradient across the AMR. The coupling between the heat transfer fluid and the magnetic refrigerant is a key aspect governing the operating characteristics of an AMR. To increase our understanding of AMR thermodynamics, we examine the entropy balance in an idealized active magnetic regenerator. A relation for the entropy generation in an AMR with varying fluid capacity ratios is derived. Subsequently, an expression describing the ideal magnetocaloric effect (MCE) as a function of temperature is developed for the case of zero entropy generation. Finally, the link between ideal MCE and refrigerant symmetry is discussed showing that an ideal reverse Brayton-type magnetic cycle cannot be achieved using materials undergoing a second-order magnetic phase transition.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.1536016