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Research Papers

Heat Transfer and Pressure Loss in Rectangular One-Side-Ribbed Channels With Different Aspect Ratios

[+] Author and Article Information
Jens von Wolfersdorf

Institute of Aerospace Thermodynamics,
Universität Stuttgart,
Stuttgart, D-70569, Germany
e-mail: itlr@itlr.uni-stuttgart.de

Uwe Ruedel

ALSTOM Power Systems Turbomachines Group,
Brown Boveri Strasse 7,
Baden, CH-5401, Switzerland
e-mail: uwe.ruedel@power.alstom.com

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received May 1, 2011; final manuscript received July 23, 2011; published online March 25, 2013. Editor: David Wisler.

J. Turbomach 135(3), 031004 (Mar 25, 2013) (9 pages) Paper No: TURBO-11-1071; doi: 10.1115/1.4006871 History: Received May 01, 2011; Revised July 23, 2011

An investigation was conducted to assess the thermal performance of W-shaped, 2W-shaped and 4W-shaped ribs in a rectangular channel. The aspect ratios (W/H) were 2:1, 4:1, and 8:1. The ribs were located on one channel wall. The rib height (e) was kept constant with a rib height-to-hydraulic diameter ratio (e/Dh) of 0.02, 0.03, and 0.06. The rib pitch-to-height ratio (P/e) was 10. The Reynolds numbers investigated (Re > 90 000) are typical for combustor liner cooling configurations of gas turbines. Local heat transfer coefficients using the transient thermochromic liquid crystal technique and overall pressure losses were measured. The rib configurations were investigated numerically to visualize the flow pattern in the channel and to support the understanding of the experimental data. The results show that the highest heat transfer enhancement is obtained by rib configurations with a rib section-to-channel height ratio (Wr/H) of 1:1. W-shaped ribs achieve the highest heat transfer enhancement levels in channels with an aspect ratio of 2:1, 2W-shaped ribs in channels with an aspect ratio of 4:1 and 4W-shaped ribs in channels with an aspect ratio of 8:1. Furthermore, the pressure loss increases with increasing complexity of the rib geometry and blockage ratio.

Copyright © 2013 by ASME
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References

Figures

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Fig. 1

Schematic of test rig [3]

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Fig. 2

Schematic of air flow with (a) closed valve and (b) open valve

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Fig. 3

Channel with implemented modules

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Fig. 4

Temperature step in the test section

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Fig. 5

Investigated rib configurations

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Fig. 6

Computational mean velocity and secondary flow distributions at Re∼250 K

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Fig. 7

Flow field close to the ribbed wall with W-shaped, 2W-shaped, and 4W-shaped ribs, (a) top view, (b) sectional side view, Re∼250 K

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Fig. 8

Friction factor ratios f/f0

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Fig. 9

Heat transfer enhancement on the ribbed wall including the rib surface

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Fig. 10

Heat transfer enhancement on the channel sidewall

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Fig. 11

Heat transfer enhancement on the channel top wall

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Fig. 12

Thermal performance of all test cases

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Fig. 13

Nu/Nu0 distribution on the ribbed wall

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Fig. 14

Nu/Nu0 distribution on the sidewall

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Fig. 15

Nu/Nu0 distribution on the top wall

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Fig. 16

Nu/Nu0 distribution on the ribs at Re∼130 K

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Fig. 17

Heat transfer distribution on the ribbed wall at Re∼130 K

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Fig. 18

Heat transfer distribution on the sidewall at Re∼130 K

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Fig. 19

Heat transfer distribution on the top wall at Re∼130 K

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