Numerical analysis on the performance of a kW class magnetic refrigerator

We have constructed a room-temperature magnetic refrigerator, which was designed to provide kW class of cooling capacity at the temperature span of zero. The system uses two sets of ring Halbach-array magnetic circuit with a peak field of 1.5 Tesla, which are sandwiching a disk shaped active magnetic regenerator bed (AMR bed). The disk type AMR bed is divided into 12 sections. Each section is packed with sphere gadolinium (Gd) or Gd alloys (Gd-Y) compounds. Total amount of the magnetocaloric materials packed into one disk type AMR bed is 3.6 kg. The magnets rotate up to 40 rpm. The flow rate of the heat transfer fluid is up to 25 liter per minute. It is demonstrated that the cooling capacity is 1.4 kW at the temperature span of zero, and the maximum temperature span is 21 K under the no heat load condition using Gd and Gd-Y compound. In order to analyze the thermal characteristics of the kW class refrigerator, one-dimensional numerical simulations have been carried out. The simulations use experimentally obtained and predicted magnetocaloric properties of magnetocaloric materials. The one-dimensional simulations can describe the experimental results even in the actual condition of two-dimensional AMR bed shape. It is confirmed from experiment and numerical analysis that layered AMR bed which is packed with multiple materials gives larger maximum temperature span than that which is packed with a single material.