Assessment of demagnetization phenomena in the performance of an active magnetic regenerator

The primary objective of this paper is to quantify the impact of the internal magnetic field and reversibility of the magnetocaloric effect on the numerical evaluation of the thermal performance of a parallel-plate active magnetic regenerator. To this end, direct measurements of the adiabatic temperature change of commercial-grade gadolinium samples were carried out for an applied field change of 1.65 ± 0.03 T (for both magnetization and demagnetization) and temperatures between 283 and 303 K. The tests were carried out in a specially constructed apparatus and the results were in good agreement with the literature. The data were incorporated into a mathematical model for solving the fluid flow and conjugated heat transfer in the parallel-plate regenerator. It was found that if demagnetization phenomena (i.e., the demagnetization factor and the reversibility of the magnetocaloric effect) are not take properly into account, the thermal performance of the regenerator can be severely over-predicted.

► Experimental device for direct measurements of adiabatic temperature change (magnetocaloric).
► Evaluation of demagnetization phenomena (internal field and reversibility) in Gd samples.
► Incorporation of experimental data into a model for conjugate heat transfer in parallel-plate AMR.
► Demagnetization factor represents a true performance loss and should be kept as low as possible.
► Reversibility should be considered in modeling to avoid over-prediction of cooling capacity.