Numerical Investigation of Flow and Heat Transfer in a Dimpled Channel among Transitional Reynolds Numbers

The SST turbulent model coupled with Gamma-Theta transition model was adopted in the investigation of the flow and heat transfer characteristics of a rectangular channel with arrays of dimples among transitional Reynolds number. The results show that the velocity gets plumper along streamwise direction which indicates that the flow is transited from laminar flow to turbulent flow, which is also confirmed by the turbulence intermittency distribution. The dual vortex inside the dimple becomes asymmetrical when Reynolds number increases. The averaged Nusselt number decreases monotonously in the streamwise direction when the flow is under laminar condition while it increases monotonously when the flow is under turbulent condition. The heat transfer is enhanced by the dimple when the flow is turbulent and it increases with the dimple depth. However, the heat transfer is worsened by the dimple when the flow is laminar. The friction factor increases when the dimple depth increases. The overall thermal performance increases with Reynolds number. The dimple arrays with depth ratio equal to 0.2 show the best overall thermal performance.