Effects of turning vane on flow control and heat transfer in ribbed two-pass channel with varied rib patterns

Faced with the escalating cooling requirements of turbine blades, two-pass channels with ribs on the internal surfaces have been extensively employed to enhance internal wall heat transfer. Considering the potential to mitigate flow separation and pressure losses generated by channel curvature, in this study, a computational fluid dynamics approach based on the realizable k-epsilon turbulence model is employed to explore the effects of turning vane introduction on the flow and heat transfer characteristics of two-pass channels with varying rib configurations. The rib configurations are identified as NN, NP, PP and PN. "N" denotes the ribs rotated 45 degrees clockwise relative to the flow direction, while "P" denotes the ribs rotated 45 degrees counterclockwise. The results indicate that the introduction of turning vanes improves the flow uniformity in the downstream channel of the two-pass channel with N-patterned upstream ribs, enhancing inter-rib heat transfer in the downstream channel. It also strengthens the heat transfer performance at the bend region of the two-pass channel with P-patterned upstream ribs. Furthermore, the introduction of turning vanes results in a decrease in friction loss factor for two-pass channels with various rib arrangements at varying levels of Reynolds numbers. The reduction is more pronounced in the two-pass channel featuring N-patterned upstream ribs, with a maximum decrease of 18.6 %. In contrast, the decrease is only 5.2 % in the PP-patterned rib channel. Additionally, the thermal performance factor of NP-patterned and NN-patterned rib channels increases by 8.5 % and 8.7 % respectively after the insertion of turning vanes. However, the enhancement is limited in the PP-patterned and PN-patterned rib channels.