A Study of Heat Transfer Augmentation in a Rectangular Channel with Dimples Applied to One Wall

Abstract

This study is an investigation of the heat transfer augmentation through the fullydeveloped portion of a narrow rectangular duct (AR=2) characterized by the application of dimples to the bottom wall of the channel. The geometries are studied at channel Reynolds numbers of 20000, 30000, and 40000. The purpose is to understand the contribution of dimple geometries in the formation of flow structures that improve the advection of heat away from the channel walls. Experimental data reported includes the local and Nusselt number augmentation of the channel walls and the overall friction augmentation throughout the length of the duct. The large dimple feature was found to promote significant intensification of convective heat transfer, as high as eighty percent, at a Reynolds number of 30000. Furthermore, the double dimple surface feature was found to promote heat transfer augmentation comparable to the large dimple feature, accompanied by the pressure loss penalty of the modest small dimple. By contributing to a clearer understanding of the effects produced by these geometries, the development of more effective channel-cooling designs can be achieved.