Heat transfer enhancement in gas turbine U-shaped channel with rib tabulators under rotational effect

In this paper, flow and heat transfer characteristics are presented for U-shaped channel with 90 deg ribs that is as internal cooling passage of turbine blades. The influence of the U-shaped turning bend and rotation on the flow and heat transfer in the channel was investigated in three cases. In the present model, the 90 deg parallel ribs are placed on rotating trailing surfaces. The Reynolds number is fixed at 12500 and the corresponding rotation number varies from 0.2-1. The rib height to hydraulic diameter ratio is 0.096 and the rib pitch-to-height ratio is 10. Stationary case and several rotating cases were investigated. Analysis of the numerical results leads to the following conclusions: Periodic distributions of flow and heat transfer coefficient are observed in all of the cases. Obvious secondary flow and heat transfer enhancement are observed in the turning bend area and the heat transfer rate in the second pass is significantly higher than those in the first pass. For the rotational cases, the effect of rotation on the heat transfer enhancement is complicated according to different rotating surfaces and pass number. The average Nusselt number ratio of the whole channel is increased significantly due to the effect of rotation. (c) 2014 Published by Elsevier Ltd.