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

Abstract

Coolant flow in rotating internal serpentine channels is highly complex due to the effects of the Coriolis force and centrifugal buoyancy. Detailed knowledge of the heat transfer over a surface will greatly enhance the blade designers’ 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 on channel surfaces with smooth walls, 90 deg rib and W-shaped rib turbulated walls. The test section is made up of two passes to model radially inward and outward flows. 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. The inlet coolant-to-wall density ratio is fixed at 0.08, Re = 16,000, and Ro = 0.08. The present study shows that the W-shaped ribs enhance heat transfer in all cases (stationary and rotating) approximately 1.75 times more than the 90 deg ribs. The W-shaped rib channel is least affected by rotation, which may be due to the complex nature of the secondary flow generated by the geometry. A higher pressure drop is associated with the W-shaped ribs than the 90 deg ribs, however, the overall thermal-hydraulic performance of the W-shaped ribs still exceeds that set by the 90 deg ribs.

A Review of Heat Transfer and Pressure Loss Characteristics Through Convective Cooling Method for Gas Turbine Thermal Management

“…The overall performances for broken ribs are higher compared with the continuous ribs in two-pass cooling channels. Lamont et al (2012) [11] examined the differences in heat transfer distributions on channel surfaces with smooth walls, 90 0 rib and W-shaped rib in rotating channel. The inlet coolant-to-wall density ratio was fixed at 0.08, Reynolds number was 16,000, and Rotation number was 0.08.…”

Validation of the Transient Liquid Crystal Thermography Technique for Heat Transfer Measurements on a Rotating Cooling Passage

“…In the open literature, few contributions make use of the transient LCT approach implementing a fluid cold temperature step to investigate about rotating cooling channels. Among these, the most significant and numerous contributions come from Ekkad et al Starting from the first work reported in 2012, a number of different channel configurations have been investigated with the attention on the effects of ribs geometry [15], channel orientation [16,17], and multi-pass configuration with optimized layouts to minimize the Coriolis effect [18,19]. A rig capable to reach extremely high rotational speeds has been designed and commissioned at the University of Stuttgart in Germany [20], but at the moment, only preliminary data have been published.…”