CFD Study of Heat Transfer in Stirling Engine Regenerator

Abstract A three dimensional rhombic-drive beta-type Stirling engine is computationally studied with the utilization of ANSYS Fluent software. Research is mainly focused on the characteristics of heat transfer between the working fluid and the regenerator matrix. The regenerator is divided in several sections. The variation of gas and matrix temperature, as well as heat transfer during one cycle of the engine are presented and discussed. The fluctuation of fluid temperature is higher than that of the matrix, while fluid and matrix temperatures in each section are almost equal at the respective instances of flow reversal. Moreover, Nusselt number increases with Reynolds number by a linear trend. The derived correlation for Nusselt number is representative of the total engine cycle. Working gas and metal matrix temperature profile is linear in the biggest part of the regenerator, while at the regenerator ends it is approximated by a 2nd order polynomial equation. The spatial and temporal variation of temperature, as well as the heat transferred between gas and matrix is well approximated by derived equations that incorporate time and length as independent variables and can calculate the value of the studied quantities at a given time instance and a location in the regenerator. These findings can be used as input in a simple analytical model for the specific engine and improve the model outcomes.