The effect of a hub turning vane on turbulent flow and heat transfer in a four-pass channel at high rotation numbers

This paper investigates effects of rotation and a turning vane on flow field and heat transfer of a 4-pass smooth channel through CFD (Computational Fluid Dynamics) simulations. An 180° hub U-bend connecting the middle two passages (AR = 2:1) is the focus of the study. Reynolds number varies from 10,000 to 40,000 and rotation number changes from 0 to 0.4. In stationary conditions, effect of the turning vane is to reduce recirculation and non-uniformity of mainstream. In addition, pressure drop and secondary flow kinetic energy (SKE) are largely reduced by the turning vane. Heat transfer deterioration due to flow separation and recirculation is suppressed by the turning vane in Hub Turn. In rotating conditions, size of recirculation is reduced and uniformity of mainstream is increased comparing to stationary case. Velocity distribution and heat transfer exhibit different profiles on LE and TE considering the flow direction due to Coriolis. Effects of turning vane to suppress recirculation and to reduce pressure drop are not obvious. In Hub Turn and downstream 3rd pass, heat transfer enhancement due to turning vane is very weak.