Detailed Heat Transfer Measurements Inside Rotating Ribbed Channels Using the Transient Liquid Crystal Technique

Abstract

The effects of the Coriolis force and centrifugal buoyancy are well known in rotating internal serpentine coolant channels in turbine blades. As channel flow in rotation is highly complex, detailed knowledge of the heat transfer over a surface will greatly enhance the blade designer’s ability to predict hot spots so coolant may be distributed effectively. The present study uses a novel transient liquid crystal technique to measure heat transfer on a rotating two-pass channel surface with chilled inlet air. The present study examines the differences in heat transfer distributions of three channel types in rotation: smooth wall, 90° ribs, and W-shaped ribs. The two channels in the test section model radially inward and outward flow. To account for centrifugal buoyancy, cold air is passed through a room temperature test section. This ensures that buoyancy is acting in a similar direction to real turbine blades. Three parameters were controlled in the testing: inlet coolant-to-wall density ratio, channel Reynolds number, and Rotation number. Results were compared to previous studies with similar test conditions. The present study shows that the W-shaped ribs enhance heat transfer in all cases (stationary and rotating) approximately 2–3 times better than the 90° ribs. The W-shaped ribbed channel is least affected by rotation due to the complex nature of the flow generated by the geometry.

Effect of Rotation on Detailed Heat Transfer Distribution for Various Rib Geometries in Developing Channel Flow

“…The results from this experimental method have been compared by Lamont et al [14] for heat transfer in rotating two-pass channels. They compared their results for smooth channels with other studies to validate the experimental results against published results.…”

“…This study focuses on the entrance region of a channel and compares heat transfer differences between an unribbed and ribbed channel. Detailed heat transfer distributions are measured with and without rotation using a transient liquid crystal technique developed for rotating channel rigs [14]. This technique is the first method to obtain detailed heat transfer distributions inside rotating channels during a short duration transient experiment.…”