Abstract
Most of previous researches about active magnetic regenerators (AMR) didn’t pay much attention to the effects of conduction heat transfer between the hot end and the cold end through the magnetocaloric material in AMR on the efficiency of cooling. For an increase in efficiency, the work here investigates this point with an introduction of adiabatic segments inserted into the magnetocaloric material to prevent the heat conduction through it. The length, number and positon of adiabatic segments under various system parameters are analyzed numerically to improve the cooling performance of AMR. A simplified 1-D transient model of AMR is adopted and solved by COMSOL Multiphysics. The AMR model is a reciprocating type with Gd plates as magnetocaloric material and water as working fluid. The maximum magnetic field is 1 T. The numerical simulation is done under the conditions of constant porosity and constant thickness of Gd plates. The results show that the adiabatic segments can improve the cooling performance of AMR. For most cases, longer and more segments lead to a better performance. In addition, the position of segments in the middle region between the cold end and the center of Gd plates usually provides a higher cooling power. Further, the adiabatic segments will be more effective for high temperature difference and long operating period. The parameters such as the temperature difference, the period and the number of Gd plates will interact with one another and have coupling effects on the AMR performance. The two conditions (constant porosity and constant thickness) have similar results except that the trend of the cooling power versus the number of Gd plates is different due to the total Gd mass of the latter one increasing with the number of Gd plates. Under the constant-thickness condition, a better AMR performance is achieved for the magnitude of utilization factor around 1-1.6 by adjusting the mass flow rate.