Numerical analysis of the flow pathlines in thermo-acoustic couples

Thermo-acoustic systems use a high amplitude sound-wave for refrigeration or electricity generation without the drawbacks of expensive construction, adverse environmental impact or high maintenance cost. The effective conversion of energy occurs within the “stack” considered as the heart of the system. The time-averaged rate of heat transfer across the edges of the stack is a good indicator of an effective performance. Hence, studying the effect of the geometry of the stack edges together with their locations is useful. Furthermore, current manufacturing practices make it possible to develop diverse stack edges, resulting in an improved efficiency of the heat transfer. For effective modelling of the heat transfer rate, a second-order, double-precision discretization of state variables and a laminar viscous model was used. A numerical model was developed using the commercial code FLUENT. The evolution of the flow vortices at different drive ratio was analyzed. Two edges shapes were considered namely rectangular and rounded edges. Using numerical analysis, this study has pointed out that stack edge profiles has a significant effect on the overall performance of thermo-acoustic systems. Rounding the stack edge profile appears to be beneficial for the system performance. This study points out the link between the non-linearity observed in thermo-acoustic systems, the flow streaming and the mean vorticity at the stack edges.