Numerical evaluation of heat transfer characteristics and effectiveness of miniature Stirling cryocooler’s regenerator: A multi-part computational study

Miniature Stirling cryocoolers with refrigeration capacities from 0.25 W to 2 W and cooling temperatures between 50 K and 150 K have made their way to the defense, aerospace, and medical industries. The regenerator is an essential part and its performance has significant effects on the miniature cryocooler. In this study, firstly, the non-ideal effects of matrix material longitudinal heat conduction and temperature-dependent properties of both the matrix material and working fluid on regenerator performance are numerically analyzed using the parallel flow model. The findings show that non-ideal longitudinal conduction relatively increases in-efficiency by 137 % maximum, If combining the effects of the matrix material and the working fluid thermophysical properties, the in-efficiency will further increase by 30 % and 5 %, respectively. The regenerator’s performance is primarily affected by longitudinal conduction and matrix material properties. Secondly, the 2D porous structure of regenerator simulation under cyclic flow is performed using CFD-assisted methodology, and the studies show that compared to constant material properties, the in-efficiency and temperature swings of the regenerator for temperature-dependent properties are 298 % and 185 % higher, respectively. Additionally, the effect of matrix material temperature swing is found non-negligible with the mass flow rate increasing. Finally, the effect of the cold tip heat load is investigated and found that it has instantaneous effects on the regenerator temperature profile and its efficiency, thus influencing the regenerator’s capability to transfer heat efficiently. This multi-part computational study can offer useful analyses and guides to improve the regenerator design for high-performance micro Stirling cryocoolers.