Computational Investigation of Unsteady Conjugated Heat Transfer in Microchannel Active Magnetic Regenerator

Materials such as Gd and LaFeCoSi alloy show significant entropy or temperature change during magnetisation and demagnetisation in a varying magnetic field. This is referred to as the magnetocaloric effect (MCE) on which room temperature magnetic refrigeration operation is based. An active magnetic regenerator (AMR), made of magnetocaloric material (MCM), is one of the key components of a room temperature magnetic refrigerator/heat pump. The working fluid, normally water, oscillates in the AMR and therefore the heat transfer in the AMR is essentially transient. The AMR in the present work is a microchannel heat exchanger made of Gd MCM. The paper describes a computational model of the transient conjugated conductive heat transfer in MCM microchannel wall and convective heat transfer in fluid flow in channels. The model is solved using Ansys Fluent. The temperature span, transient variation of Nu and effect of the ratio of channel spacing to diameter (porosity) are examined. Heat transfer enhancement and AMR dimension optimisation are presented.