Heat Transfer in Rotating Multipass Rectangular Ribbed Channel With and Without a Turning Vane

This paper experimentally investigates the effect of a turning vane in hub region on heat transfer in a multipass 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 an 180 deg U-bend. The flow was radial inward in the second passage and was radial outward after the 180 deg U-bend in the third passage. The square-edged ribs with P/e = 8, e/D_h = 0.1, and α = 45 deg were applied on the leading and trailing surfaces of the second and the 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 180 deg 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 are correlated with rotation numbers for multipass rectangular ribbed channel with and without a turning vane.