Manipulation of Turbulent Flow for Drag Reduction and Heat Transfer Enhancement

Abstract

With recent advancement and globalization of economy, the demand for energy continues to increase rapidly, resulting in severe energy crisis in the world. To solve this problem, energy-efficiency process/device with reduced energy wastage is essential. In order to achieve these goals, flow manipulation technologies to reduce drag and to enhance thermal efficiency in turbulent flow were investigated numerically. It was shown that the corrugated surface can reduce drag by 7%-10% in turbulent channel flow. Then, the heat transfer and flow in a channel with asymmetric dimples or protrusions on single wall were examined. It was found that skewing of the deepest point of dimple to the downstream side is a feasible way to enhance heat transfer with fairly similar pressure loss. In addition, protrusions with larger height induced higher heat transfer and friction, and when h/D>=15% asymmetric Nusselt number distribution rises up due to asymmetric flow pattern.