Design trade-offs for an active magnetic regenerator device

Abstract

Magnetic Refrigeration (MR) is a technology based on the Magnetocaloric Effect (MCE), a property by which Magnetocaloric Materials (MCM) change their temperature in response to changes in magnetic field. MR has the potential to achieve efficiencies comparable to those of vapor compression systems. However, there are still some design challenges related to the development of novel Active Magnetic Regenerator (AMR) prototypes. In this work, a previously developed AMR model is integrated with an analytical model for a Magnetic Circuit (MCI) based on nested Halbach cylinders (to generate the magnetic field) and with a model to determine the power consumption of the valve system (which modulates the fluid flow through the regenerators). The models are explored to find critical values of the AMR dimensions that maximize the cooling capacity or the coefficient of performance, based on different design trade-offs. For the regenerator height, larger values yield higher refrigerant mass but require larger air gaps, resulting in lower levels of the magnetic field. For the regenerator width, considering a fixed magnetocaloric material mass, distributing it among several narrow regenerators results in higher valve power consumption, while using few wider beds minimizes demagnetizing losses. Designer maps that combine these variations are then presented, allowing engineers to select appropriate regenerator dimensions based on target requirements for the cooling capacity and coefficient of performance.