The influence of the magnetic field on the performance of an active magnetic regenerator (AMR)

TL;DR

This study investigates how the magnetic field profile affects the performance of magnetocaloric refrigeration devices using active magnetic regeneration, revealing key dependencies on magnetic field timing, strength, and profile shape.

Contribution

It provides a numerical analysis of the impact of magnetic field variations on AMR performance, highlighting the weak dependence on ramp rate and the independence of magnet design from regenerator geometry.

Findings

A 10% magnetic field profile misalignment reduces cooling capacity by 20-40%.

Increasing magnetic field strength from 1 T to 1.5 T boosts cooling capacity by 30-50%.

Performance effects are similar across different regenerator geometries.

Abstract

The influence of the time variation of the magnetic field, termed the magnetic field profile, on the performance of a magnetocaloric refrigeration device using the active magnetic regeneration (AMR) cycle is studied for a number of process parameters for both a parallel plate and packed bed regenerator using a numerical model. The cooling curve of the AMR is shown to be almost linear far from the Curie temperature of the magnetocaloric material. It is shown that a magnetic field profile that is 10% of the cycle time out of sync with the flow profile leads to a drop in both the maximum temperature span and the maximum cooling capacity of 20-40\% for both parallel plate and packed bed regenerators. The maximum cooling capacity is shown to depend very weakly on the ramp rate of the magnetic field. Reducing the temporal width of the high field portion of the magnetic field profile by 10% leads to a drop in maximum temperature span and maximum cooling capacity of 5-20%. An increase of the magnetic field from 1 T to 1.5 T increases the maximum cooling capacity by 30-50% but the maximum temperature span by only 20-30%. Finally, it was seen that the influence of changing the magnetic field was more or less the same for the different regenerator geometries and operating parameters studied here. This means that the design of the magnet can be done independently of the regenerator geometry.