Heat transfer of turbulent flow over surfaces with spherical dimples and teardrop dimples

A comparative experimental and numerical study was conducted to investigate the heat transfer of turbulent flow in channels with one dimpled wall with arrays of spherical dimples and teardrop dimples, and the dimples have the same depth with depth-to-diameter ratio of 0.2. The heat transfer and flow structure characteristics in the two dimpled channels have been obtained and compared with each other for the Reynolds numbers of 8500-60,000. The study showed that the globally averaged heat transfer enhancement of the spherical dimple channel can be 1.5-1.7 times the fully developed flow in a smooth duct with the friction factor of 1.2-2.0 times the smooth duct flow. Compared to the spherical dimples, the teardrop dimples have distinctively higher heat transfer performance by about 18.0% with increased pressure loss by 35-15% as the Reynolds number increases. Furthermore, the numerical computations showed that the standard k-omega turbulence model can reasonably well predict the heat transfer and pressure loss in the dimpled channels, which indicated different heat transfer and turbulent flow patterns in the spherical and teardrop dimples, and revealed the underlying mechanisms for heat transfer enhancement for the spherical and teardrop dimples. (C) 2014 Elsevier Inc. All rights reserved.