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RESEARCH PAPERS

# An Experimental and Numerical Study of Heat Transfer and Pressure Loss in a Rectangular Channel With V-Shaped Ribs

[+] Author and Article Information
Michael Maurer, Jens von Wolfersdorf

Institute of Aerospace Thermodynamics, University of Stuttgart, Stuttgart, D-70569 Germanyitlr@itlr.uni-stuttgart.de

Michael Gritsch

ALSTOM (Switzerland) Ltd., Technology Center TTC-TT, Birr, CH-5242 Switzerlandmichael.gritsch@power.alstom.com

J. Turbomach 129(4), 800-808 (Aug 09, 2006) (9 pages) doi:10.1115/1.2720507 History: Received July 26, 2006; Revised August 09, 2006

## Abstract

An experimental and numerical study was conducted to determine the thermal performance of V-shaped ribs in a rectangular channel with an aspect ratio of 2:1. Local heat transfer coefficients were measured using the steady state thermochromic liquid crystal technique. Periodic pressure losses were obtained with pressure taps along the smooth channel sidewall. Reynolds numbers from 95,000 to 500,000 were investigated with V-shaped ribs located on one side or on both sides of the test channel. The rib height-to-hydraulic diameter ratios $(e∕Dh)$ were 0.0625 and 0.02, and the rib pitch-to-height ratio $(P∕e)$ was 10. In addition, all test cases were investigated numerically. The commercial software FLUENT™ was used with a two-layer $k-ε$ turbulence model. Numerically and experimentally obtained data were compared. It was determined that the heat transfer enhancement based on the heat transfer of a smooth wall levels off for Reynolds numbers over 200,000. The introduction of a second ribbed sidewall slightly increased the heat transfer enhancement whereas the pressure penalty was approximately doubled. Diminishing the rib height at high Reynolds numbers had the disadvantage of a slightly decreased heat transfer enhancement, but benefits in a significantly reduced pressure loss. At high Reynolds numbers small-scale ribs in a one-sided ribbed channel were shown to have the best thermal performance.

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## Figures

Figure 1

Principle mass flow in a combustor with (a) film cooling and with (b) convective cooling

Figure 2

Schematic of test rig

Figure 3

Sketch of the bottom wall rear part of the test channel

Figure 4

Typical TLC color distribution during measurement

Figure 5

Mesh volume for one-sided and two-sided ribbed segments

Figure 6

Flow structures (top) in the axial direction and (bottom) close to the bottom wall

Figure 7

Velocity profile of test case 1 at Re=130,000

Figure 8

Slices of velocity profiles of test case 1 at Re=130,000

Figure 15

Comparison between experimentally and numerically obtained local heat transfer ratio for Re∼130K and Re∼500K

Figure 14

Experimental local heat transfer ratios

Figure 13

Thermal performance

Figure 12

Area averaged Nusselt number ratios

Figure 11

Friction factor ratios f∕f0 for investigated cases

Figure 10

Slices of velocity profiles of test case 2 at Re=130,000

Figure 9

Velocity profile of test case 2 at Re=130,000

## Errata

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