Effect of surface curvature on heat transfer and hydrodynamics within a single hemispherical dimple

Turbulent heat transfer and hydrodynamics have been studied in concavely and convexly curved dimples with Reynolds numbers ranging from 1.3 X 10(5) to 3.1 X 10(5). The large-scale single hemispherical dimple 50 min in diameter and 25 min in depth was arranged on the smooth concave or convex wall of a curved rectangular-shaped passage. The fluid flow and heat transfer measurements, and surface streamline observations were performed within the flow curvature parameter delta**/R ranged from 0.002 to 0.007. The tornado-like oscillating vortex bursting periodically out of the dimple was registered in the experiments with a curved dimple. This vortex structure is similar to that earlier observed in a flat dimple. The surface curvature considerably influences the dimple heat transfer rate in both cases. It enhances heat transfer in a concave dimple and reduces it in a convex one; however, the more remarkable effect occurred in a concavely curved dimple. The correction factors describing the effect of curvature on average heat transfer in a curved dimple have been obtained as a result of experimental study.