Heat Transfer in a Rotating, Two-Pass, Variable Aspect Ratio Cooling Channel With Profiled V-Shaped Ribs

The thermal performance of two V-type rib configurations is measured in a rotating, two-pass cooling channel. The coolant travels radially outward in the rectangular first pass (aspect ratio (AR—channel width:height) = 4:1) and radially inward in the second pass (AR = 2:1). Both the passages are oriented 90 deg to the direction of rotation. The leading surface (LS) and trailing surface (TS) of the channel are roughened with V-type ribs. The first V-shaped configuration has a narrow gap at the apex of the V. The configuration is modified by off-setting one leg of the V to create a staggered discrete, V-shaped configuration. The ribs are oriented 45 deg relative to the streamwise coolant direction. The heat transfer enhancement and frictional losses are measured with varying Reynolds and rotation numbers. The Reynolds number varies from 10,000 to 45,000 in the AR = 4:1 first pass; this corresponds to 16,000 to 73,500 in the AR = 2:1 second pass. The maximum rotation numbers are 0.39 and 0.16 in the first and second passes, respectively. The heat transfer enhancement on both the leading and trailing surfaces of the first pass of the 45 deg V-shaped channel is slightly reduced with rotation. In the second pass, the heat transfer increases on the leading surface, while it decreases on the trailing surface. The 45 deg staggered, discrete V-shaped ribs provide increased heat transfer and thermal performance compared to the traditional V-shaped and standard, 45 deg angled rib turbulators.