Internal Cooling in 4:1 AR Passages at High Rotation Numbers

Abstract

Heat transfer and pressure drop measurements are reported for a rotating 4:1 aspect ratio (AR, (the ratio of the width of leading/trailing wall to the height of sidewalls) smooth coolant passage for Reynolds number in the range of 10,000–150,000, rotation number in the range of 0–0.6, and density ratios between 0.1–0.2. The measurements are performed for both 90° and 45° orientations of the coolant passage relative to the rotational axis. These measurements are done in a rotating heat transfer rig utilizing segmented foil heated elements and thermocouples, with slip rings providing the interface between the stationary and rotating frames. Results indicate that beyond specific Ro values (different values for the inlet and outlet passages) the expected trends of heat transfer enhancement on the destabilized surface and degradation on the stabilized surface are reversed. The inlet leading surface shows enhancement with Ro only at low Re, and shows degradation at high Re. Increasing density ratio enhances the heat transfer on all walls. Orientation of the coolant passage relative to the rotational axis has an important effect, with the 45° orientation reducing the heat transfer on the destabilized surface and enhancing it on the stabilized surface.