Experimental and numerical results of a high frequency rotating active magnetic refrigerator

Abstract

Experimental results for a recently developed prototype magnetic refrigeration device at The Technical University of Denmark (DTU) were obtained and compared with numerical simulation results. A continuously rotating active magnetic regenerator (AMR) using 2.8 kg packed sphere regenerators of commercial grade gadolinium (Gd) was employed. With operating frequencies up to 10 Hz and volumetric flow rates up to 600 L/h, the prototype has shown high performance and the results are consistent with predictions from numerical modelling. Magnetocaloric properties of the Gd spheres were obtained experimentally and implemented in a one-dimensional numerical AMR model that includes also the parasitic losses from the prototype. The temperature span for a thermal load of 200 W as a function of frequency was measured and modelled. Moreover, the temperature span dependence on the cooling capacity as a function of cycle frequency was determined. It was found that thermal losses increase as the frequency increases. Therefore, a detailed study of these parasitic losses was carried out experimentally and numerically.

Development and experimental results from a 1 kW prototype AMR

“…Thus mapping out the parameter space will allow better knowledge of the optimal operating parameters for a desired output. More detailed studies of parameter variations are given in Engelbrecht et al (2012) and Lozano et al (2012a and2012b). An important tool for the study of AMR devices is numerical modelling as discussed in Nielsen et al (2011).…”

A comparison between experimental and 2D numerical results of a packed-bed active magnetic regenerator

“…Furthermore (Fig.9), the simulation results, in accordance with the experimental results and with the results declared by other researchers [12,42], show that for each hot side temperature an optimal cycle frequency occurs. As noticed by Lozano et al [43] this phenomenon happens because at lower frequencies there is a large influence of the longitudinal thermal conduction and the regenerator utilization becomes too high seen that at lower frequencies the temperature span increases with increasing frequency until a certain optimum frequency from which the irreversible losses become significant and the heat transfer is affected, so the regenerator is not capable to maintain a high temperature span.…”

Overview of Existing Magnetocaloric Prototype Devices

“…In 2014, additional studies on the performance of the described prototype were presented by Lozano et al [65]. They studied the impact of high operating frequencies up to 10 Hz and volumetric flow rates up to 600 l h −1 .…”

“…However, through personal correspondence with Professor Dr. Oliver Gutfleisch from TU Darmstadt, 10 Hokakaido Ins., Table 7 Lozano et al [64,65] Not built yet, predictions only the authors of this book have obtained the design of a 3D model of the first rotary magnetic prototype. It is planned to be built towards the end of 2014.…”