Design and optimization of a magnet for magnetocaloric refrigeration.

The magnetic field source is the most expensive element of a magnetic refrigeration device. The design of an efficient magnet with high and low field regions, using reduced volumes of permanent magnets, is of paramount importance for the practical application of this new technology. A two-pole rotary magnet formed by sectors of oriented hard magnets and soft iron pieces is optimized in angular width and magnetization direction of each sector. A quadratic approximation is used for the optimization of the defining angles. This procedure provides the parameters that result in extreme values of a given functional F, defined as an efficiency variable of the working device. The procedure also gives the correlation between parameters and the relative importance of the deviations with respect to their mathematical optimal values. An optimized magnet has also been built, and the resulting calculated fields are compared with experimental measurements in the real system. Published under license by AIP Publishing.