Constructal design of a circular micro-channel Stirling regenerator based on exergy destruction minimization

Abstract

Regenerator is a key component in Stirling engines, and its characteristics have a significant influence on engine performance. Herein, subjected to the global constraints of the fixed total volume and porosity, constructal design of a circular micro-channel regenerator was conducted to achieve its optimal structures. The total exergy destruction rate in the irreversible regenerative process, which includes three types of individual exergy destruction contributions caused by the heat transfer with a finite temperature difference, flow resistance, and axial heat conduction of the solid matrix, was adopted as the optimization objective. The optimal channel diameter was obtained, and the effects of the regenerator inner radius, total volume of regenerators, regenerator porosity, engine speed, piston phase angle, hot part temperature, charge pressure, and thermal conductivity ratio due to the segmentation of regenerators on the optimization results were analyzed. The results show that the total exergy destruction rate offers a minimum at a relatively low channel diameter of around 0.5 mm under the given parameter values. All the parameters studied have an obvious effect on the minimum total exergy destruction rate, and the regenerator inner radius, total volume and porosity of regenerators, and engine speed also have an evident influence on the optimal structure of the regenerator. These indicate that the regenerator performance can be further improved by selecting appropriate global geometric parameter values of regenerators and operating parameter values of engines. The findings of this study can provide some guidelines for the optimal design of micro-channel regenerators and the performance improvement of Stirling engines.