Turbulent Heat Transfer in a Channel with Injection : In the Region around the Starting Point of Injection

Abstract

Heat transfer experiments were carried out for a turbulent channel flow with fluid injection through one channel wall. An infrared-radiation thermometer was used for the measurement of wall temperature. Special attention was paid to the region close to the starting point of injection, where laminarization of the flow was observed in previous studies. Measurements were made at seven streamwise positions and the channel Reynolds number changed in four steps for various injection rates. It is demonstrated that all the obtained results can be correlated well if the reduction rate of Stanton number, St/St₀, is plotted against the injection parameter B_h. The developed correlation is found to be close to the relationship established for a flat plate turbulent boundary layer. This suggests that neither the pressure gradient necessary for internal flow nor the flow laminarization seriously affect the reduction rate of the heat transfer coefficient due to fluid injection.