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research-article

Heat Transfer in A Rotating Two-Pass Rectangular Channel Featuring A Converging Tip Turn With Various 45 Deg Rib Coverage Designs

[+] Author and Article Information
Andrew F Chen

Dept. of Mechanical Engineering 3123 TAMU College Station, TX 77843-3123 mrandrewchen@outlook.com

Chao-Cheng Shiau

3123 TAMU College Station, TX 77843 joeshiau@tamu.edu

Je-Chin Han

Department of Mechanical Engineering 3123 TAMU College Station, TX 77843-3123 jc-han@tamu.edu

Robert Krewinkel

Steinbrinkstrasse 1 Oberhausen, D-46145 Germany robert.krewinkel@man.eu

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the Journal of Thermal Science and Engineering Applications. Manuscript received December 9, 2018; final manuscript received March 31, 2019; published online xx xx, xxxx. Assoc. Editor: Steve Q. Cai.

ASME doi:10.1115/1.4043471 History: Received December 09, 2018; Accepted April 01, 2019

Abstract

Varying aspect ratio channels are found in modern gas turbine airfoils for internal cooling purposes. Corresponding experimental data are needed in understanding and assisting the design of advanced cooling systems. The present study features a two-pass rectangular channel with an aspect ratio AR = 4:1 in the first pass with radial outward flow and an AR = 2:1 in the second pass with radial inward flow after a 180 deg tip turn. Effects of rib coverage near the tip region are investigated using profiled 45 deg ribs (P/e = 10, e/Dh ≈ 0.11, parallel and in-line) with three different configurations: less coverage, medium coverage and full coverage. The Reynolds number (Re) ranges from 10,000 to 70,000 in the first passage. The highest rotation number achieved was Ro = 0.39 in the first passage and 0.16 in the second passage. Heat transfer coefficients on the internal surfaces were obtained by the regionally averaged copper plate method. The results showed that the rotation effects on both heat transfer and pressure loss coefficient are reduced with an increased rib coverage in the tip turn region. Different rib coverage upstream of the tip turn significantly change the heat transfer in the turn portion. Heat transfer reduction (up to -27%) on the tip wall was seen at lower Ro. Dependence on the Reynolds number can be seen for this particular design. The combined geometric, rib coverage, and rotation effects should be taken into consideration in the internal cooling design.

Copyright © 2019 by ASME
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