A Fundamental Study of Heat Transfer Enhancement by Controlling the Internal Structure of Turbulent Flows

Abstract

In the enhancement of turbulent heat transfer, the intensification of the fluctuating velocity normal to the heat transfer surface is crucial. On the basis of this fact, the present study has newly suggested an effective method for heat transfer enhancement by selectively intensifying a specific component of the fluctuating energy, i. e. by controlling the internal structure of turbulent flows. In the experiments, a distorting duct was used to stretch the spanwise vortices, and measurements for three components of the fluctuating energy and Reynolds shear stress were made with a hot-wire anemometer. It is p. roved that the normal component of the fluctuating energy is intensified selectively by vortex stretching, and that, associated with this intensification, the production of turbulent heat flux increases. Consequently, the heat transfer rates measured in the distorting duct are found to be 40 % higher than those in conventional two-dimensional channel flows.