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Research Papers

Heat-Transfer Characteristics of a Non-Rotating Two-Pass Rectangular Duct With Various Guide Vanes in the Tip Turn Region

[+] Author and Article Information
Dong Myeong Lee, Jun Su Park, Dong Hyun Lee, Sanghoon Lee

Department of Mechanical Engineering,  Yonsei University, Seoul 120-749, Korea

Beom Soo Kim

Korea Electric Power Research Institute, Daejeon 305-380, Korea

Hyung Hee Cho

Department of Mechanical Engineering,  Yonsei University, Seoul 120-749, Koreahhcho@yonsei.ac.kr

J. Turbomach 134(5), 051039 (Jun 05, 2012) (10 pages) doi:10.1115/1.4004860 History: Received July 12, 2011; Revised August 05, 2011; Published June 05, 2012; Online June 05, 2012

The present study investigated convective heat transfer inside a two-pass rectangular duct with guide vanes in the turning region. The objective was to determine the effect of the guide vanes on blade-tip cooling. The duct had a hydraulic diameter (Dh ) of 26.67 mm and an aspect ratio (AR) of 5. The duct inlet width was 80 mm, and the distance between the tip of the divider and the tip wall of the duct was also 80 mm. Various guide vane configurations were used in the turning region. The Reynolds number (Re), based on the hydraulic diameter, was held constant at 10,000. The naphthalene sublimation technique was used to determine the detailed local heat-transfer coefficients, using the heat-and mass-transfer analogy. The results indicate that guide vanes in the turning region enhance heat transfer in the blade-tip region. The guide vane on the second-pass side of the turning region had higher heat transfer than the guide vane on the first-pass side. Strong secondary flow enhanced heat transfer in the blade-tip region. Dean vortices induced by the guide vanes pushed the high-momentum core flow toward the tip wall, and heat transfer was increased in the turning region, but decreased in the second passage. Consequently, a guide vane on the second-pass side of the turning region generates high-heat-transfer rates on the tip surface, and can also increase the thermal performance factor in a two-pass duct.

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Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Schematic views of experimental apparatus [19]

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Figure 2

Composition of test channel

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Figure 3

Photographs of test plates

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Figure 4

Test channel for various guide vanes. (a) No guide vane (baseline), (b) two-pass inner guide vane (2PIV), (c) one-pass inner guide vane (1PIV), (d) U-bend inner guide vane (UBIV), (e) two-pass outer guide vane (2POV), and (f) two-pass both guide vane (2PBV).

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Figure 5

The coordinate system. (a) Tip surface, and (b) duct surface.

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Figure 6

Expected secondary flow patterns in the two-pass duct [13]. (a) Conceptual secondary flow structures, and (b) secondary flows for different locations.

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Figure 7

Velocity contours on the duct for various guide vanes. (at z/Dh  = 0.12). (a) Baseline, (b) 2PIV, and (c) 2PBV.

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Figure 8

Vorticity contours in the duct. (a) Baseline, (b) 2PIV, and (c) 2PBV.

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Figure 9

Heat/mass transfer distribution on the duct and tip surfaces for various guide vanes. (a) Baseline, (b) 2PIV, (c) 1PIV, (d) UBIV, (e) 2POV, and (f) 2PBV.

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Figure 10

Pitch-wise averaged Sherwood number on the duct surface for various guide vanes

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Figure 11

Local Sherwood number at the third pitch on the duct surface for various guide vanes (at x/Dh  = 4.59)

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Figure 12

Span-wise averaged Sherwood number on the tip surface for various guide vanes

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Figure 13

Friction factor ratios for various guide vanes

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Figure 14

Thermal performance factors for various guide vanes

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