A lumped-element magnetic refrigerator model

Abstract

This work presents a dynamic lumped parameter model to predict the transient and steady-state cabinet temperature, energy consumption and efficiency parameters of a small capacity magnetic refrigerator equipped with a retrofitted thermally insulated wine cooler cabinet. The model is divided into independent, experimentally validated sub-models for the active magnetic regenerator (AMR), magnetic and hydraulic circuits, heat exchanger/fan assemblies and refrigerated cabinet. Primary inputs to the model are the geometric features and component dimensions, frequency and speed of power sources (hydraulic pump, axial fans and induction motor), and composition and properties of magnetic materials. Special emphasis is put on the lumped AMR model, which accurately predicts the performance of first- and second-order materials in single- and multi-layer configurations in terms of the cooling capacity, heat rejection rate and magnetic work. The model predicts the experimental steady-state cabinet temperature of a compact magnetic wine cooler prototype to within 1.5 oC, while estimating the coefficient of performance with a mean error of 6.5%. The time response of the magnetic wine cooler during a temperature pull-down test is also correctly reproduced by the model, enabling its use in the design of future magnetic heat pumping systems.