Heat Transfer in a Rotating, Blade-Shaped, Two-Pass Cooling Channel with Various 45 Deg Rib Turbulators and a Tip Turning Vane

This work experimentally studied a rotating, blade-shaped, two-pass cooling channel with various 45-deg rib turbulators and a tip-turning vane. The first passage of the cooling channel has an aspect ratio (AR) = 4:1 with the coolant moving radially outward. After a 180-deg blade-shaped tip turn, the coolant flows radially inward into the second passage with an AR = 2:1. The first and second passages are oriented at 50 deg and 105 deg from the rotation direction, respectively. In the tip-turn portion, a tip-turning vane with an oval cross section connects the mid-lines of the two passes. Two orientations of 45 deg angled ribs were considered in this work: unusual and criss-cross. The ribs have a profiled cross section and were placed in-line (P/e = 10, e/H = 0.16) on the leading and trailing surfaces of the channel. Five inlet Reynolds numbers (10,000–45,000) and five rotational speeds (0−400 rpm) were considered in this study, with a maximum rotation number of Ro = 0.38 achieved in the first pass. The results showed that the effect of the turning vane on heat transfer and pressure loss for the 45-deg unusual rib case was insignificant. The overall heat transfer for the criss-cross rib case was slightly increased by the turning vane. For pressure loss, the turning vane provided approximately an 8% reduction in the 45-deg criss-cross rib case, which was the highest in the rib cases. The 45-deg criss-cross ribs presented the highest thermal performance with the turning vane.