Influence of misalignment and spacing on the pressure drop through wire mesh Stirling engine regenerators

Abstract

In order to obtain high Stirling engine efficiencies, pressure losses in the regenerator must be minimized. In this study, numerical methods are used to determine the influence of misalignment and spacing on the pressure drop through stainless steel wire mesh regenerators. Microscope images were taken to discover the average wire misalignment found in wire mesh regenerators, and it was found that regardless of the intended stacking arrangement, the average misalignment was 44%–49%. A 3-dimensional CFD model was validated against previous empirical results, and used to determine the effect of wire mesh misalignment on the pressure drop for steady flow through a regenerator. A new friction factor correlation equation was developed to include the effect of wire misalignment in the form of tortuosity. It was found that if a perfectly aligned regenerator was manufactured, Stirling engine designers could expect a 38%–45% decrease in pressure losses. The numerical model was also used to determine the influence of axial spacing on the pressure drop, and it was found to be dependent on the misalignment, with pressure loss reductions only being realized in highly misaligned cases. As a result of this study, Stirling engine designers can confidently disregard alignment and spacing when assembling wire mesh regenerators, and can more accurately calculate the expected pressure losses.