A dimensionless numerical analysis for the optimization of an active magnetic regenerative refrigerant cycle

Abstract

SUMMARY Refrigeration by an active magnetic regenerative system (AMR) is potentially more attractive, as compared to conventional techniques. Indeed, devices based upon an AMR cycle are more efficient, compact, environment‐friendly and can operate over a broad range of temperatures. In this paper, attention is focused to the near room‐temperature range. On the other hand, however, the AMR cycle poses a variety of complex problems, in terms of fluid dynamics, heat transfer and magnetic field. In order to identify the optimal operational parameters, the design and optimization of a magnetic refrigeration system can be supported by modelling. In this paper, a dimensionless approach was adopted to simulate an AMR cycle following a Brayton regenerative cycle. In the simulation, the temperature range that has been explored is 260 – 280 K and 275 – 295 K. The heat transfer mediums are, respectively, water–glycol mixture (50% by weight) and pure water. The Gd0.8Dy0.2 alloy and pure Gd have been chosen as constituent material for the regenerator of the AMR cycle. With this model, the influence of the different parameters on cycle efficiency has been analysed. In particular, the study has been focused on the influence of the secondary fluid properties, magnetic material particle diameter, fluid blow time, secondary fluid mass flow rate, regenerator geometry and effect of axial thermal conduction. The model enables to find optimal dimensionless numbers in order to maximize the cycle performances. The results can be extended to widely different situations and therefore can be easily employed for the design and the optimization of new experimental prototypes. Copyright © 2012 John Wiley & Sons, Ltd.

Entropy Generation Minimization Analysis of Active Magnetic Regenerators

“…More recently, Aprea et al (2013) carried out a detailed optimization analysis of a packed-bed AMR based on the second-law efficiency. They investigated the influence of the fluid properties, particle diameter, fluid blow time, mass flow rate, regenerator geometry and effect of axial thermal conduction.…”

Enhancing the temperature span of thermal switch-based solid state magnetic refrigerators with field sweeping

“…So far, rotary‐based magnetic refrigerators have been the most cited designs for magnetocaloric systems, with several investigations looking for the most suited parameters that results on the best performance . Although the related prototypes already show the features required for practical applications, issues remain that make them still not competitive from a commercial point of view .…”

“…2,3 The main differences are the use of a magnetocaloric material (MCM) as the working substance instead of a gas, the use of a quasi-adiabatic magnetization process to increase the temperature of the MCM instead of the compression of the gas, and the use of a quasi-adiabatic demagnetization process to reduce the temperature of the MCM instead of the expansion of the gas. [4][5][6][7] So far, rotary-based magnetic refrigerators have been the most cited designs for magnetocaloric systems, [8][9][10][11][12] with several investigations looking for the most suited parameters that results on the best performance. 13,14 Although the related prototypes already show the features required for practical applications, issues remain that make them still not competitive from a commercial point of view.…”

A comparison between electrocaloric and magnetocaloric materials for solid state refrigeration

“…In this paper is presented a collection of test performed on MMs and EMs, with a 2D model of AMR/AER [15][16][17][18][19][20][21][22][23] regenerator, in the same operating conditions and room temperature range, to make a comparison between magnetic and electrocaloric refrigeration.…”