Heat Transfer in a Rectangular Channel with Dimples Applied to One Wall

This study is an investigation of the heat transfer augmentation through the fully developed portion of a narrow rectangular duct (aspect ratio = 2) characterized by the application of dimples to the bottom wall of the channel. The geometries are studied at channel Reynolds numbers of 20,000, 30,000, and 40,000. 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 include local heat transfer coefficient distributions, channel-averaged Nusselt number augmentation, and 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 80%) at a Reynolds number of 30,000. Furthermore, the double-dimple surface feature was found to promote heat transfer augmentation comparable with 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.