The influence of the solid thermal conductivity on active magnetic regenerators

The influence of the thermal conductivity of the regenerator solid on the performance of a flat plate active magnetic regenerator (AMR) is investigated using an established numerical AMR model. The cooling power at different (fixed) temperature spans is used as a measure of the performance for a range of thermal conductivities, operating frequencies, a long and short regenerator, and finally a regenerator with a low and a high number of transfer units (NTU). In this way the performance is mapped out and the impact of the thermal conductivity of the solid is probed. Modelling shows that under certain operating conditions, the AMR cycle is sensitive to the solid conductivity. It is found that as the operating frequency is increased it is not only sufficient to have a high NTU regenerator but the regenerator performance will also benefit from increased thermal conductivity in the solid. It is also found that a longer regenerator is generally better performing than a shorter one under the otherwise exact same conditions. This suggests that the thermal conductivity of candidate magnetocaloric materials should be considered when selecting them for use in a device.