Computational Modeling of a Segmented-Involute-Foil Regenerator for Stirling Engines

A microfabricated, segmented-involute-foil regenerator was numerically investigated using the Fluent commercial software under both steady- and oscillatory-flow conditions and using two- and three-dimensional numerical simulations. Steady-state simulations were performed for Re = 50-2000. The oscillatory-flow conditions were performed for Re max = 50 and Re ω = 0.229, with the hot end at 310 K and the cold end at 293 K. For the steady-state three-dimensional simulation, both the local friction factor and the local mean Nusselt numbers started to depart from the two-dimensional simulation values upon entering the second layer. At the entrance of every layer, the forced reorientation of the flow results in small rises of both the friction factor and the mean Nusselt number, with subsequent decrease as the flow settles into the new layer. As for the oscillatory-flow simulations, the two-dimensional model was used to study the effects of changing 1) the oscillation amplitude and frequency, 2) the thermal contact resistance between layers, and 3) the solid material. The effects of these parameters on the total regenerator heat loss (convection and conduction) were documented and are expected to be a useful tool for further development of Stirling engine regenerators.