Thermal-hydraulic behavior and influence of carryover losses in oscillating-flow regenerators

Thermal regenerators that use a liquid as the heat transfer fluid are encountered in active-caloric (e.g., magnetocaloric, electrocaloric, elastocaloric) coolers/heat pumps and other applications. In this study, we present a mathematical model, its numerical implementation and comparisons with an extensive experimental database on the thermal performance of packed bed regenerators composed of stainless steel spheres [1]. The regenerator model consists of the one-dimensional Brinkman-Forchheimer equation to describe the fluid flow in the porous matrix and coupled energy equations to determine the temperatures in the fluid and solid phases. A mathematical model for the so-called carryover (leakage) losses provoked by the dead (void) volumes on each side of the regenerator was implemented to improve the thermal effectiveness prediction. A good agreement between the mathematical model and the experimental data was observed, enabling an accurate quantification of thermal-hydraulic losses. The mathematical model and its results can be extended to and incorporated into performance analyses of active magnetic regenerators.