Effects of novel turning vanes on pressure loss and tip-wall heat transfer in an idealized U-bend channel

Abstract

In this paper, the pressure loss and tip-wall heat transfer are presented in an idealized U-bend channel with novel turning vanes. The cross-sectional area variation, flow separation, mainstream and secondary flow, pressure distribution in different turning vane(s) channels are studied. Moreover, the mechanism of heat transfer enhancement is analyzed by studying the distribution of parameters. Computational fluid dynamics technology is used for solving the steady RANS equations. Results revealed that the double-layer turning vanes channel overcomes the unfavorable factors such as flow separation, recirculation and impingement in the bend region, reducing the pressure loss in the channel by 70%. The double-layer, dome shaped turning vanes channel is a novel cooling structure based on the double-layer turning vanes. The upper wall of the upper layer turning vane is improved into a three dimensional domed structure similar to the hemispherical shell. By main flow and secondary flow acceleration and the special flow pattern caused by the surface of the dome-shaped turning vane, the pressure distribution is more uniform and more coolant flows attached to the tip wall at high velocity. The tip-wall heat transfer performance is improved by 21.77%, and Performance Evaluation Criteria increased by 71.64%. The traditional internal cooling channel guiding devices only play a single role in reducing pressure loss or improving heat transfer. While the double-layer, dome-shaped turning vanes combine can not only improve the heat transfer but also reduce the pressure loss.