Heat transfer in rotating multi-pass rectangular ribbed channel with and without a turning vane

This paper experimentally investigates the effect of turning vane on hub region heat transfer in a multi-pass rectangular channel with rib-roughed wall at high rotation numbers. The experimental data were taken in the second and the third passages (Aspect Ratio=2:1) connected by 180o U-bend. The flow was radial inward in the second passage and was radial outward after the 180o U-bend in the third passage. The squareedged ribs with P/e=8, e/D_h=0.1, and α=45o were applied on the leading and trailing surfaces of the second and third passages. Results showed that rotation increases heat transfer on the leading surface but decreases it on the trailing surface in the second passage. In the third passage, rotation decreases heat transfer on the leading surface but increases it on the trailing surface. Without a turning vane, rotation reduces heat transfer on the trailing surface and increases it on the leading surface in the hub 180o turn region. After adding a half-circle-shaped turning vane, heat transfer coefficients do not change in the second passage before-turn while they are different in the turn region and after-turn region in the third passage. Regional heat transfer coefficients and channel loss coefficients are correlated with rotation numbers for multi-pass rectangular ribbed channel with and without a turning vane.