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Research Papers

Time-Resolved Heat Transfer Measurements on the Tip Wall of a Ribbed Channel Using a Novel Heat Flux Sensor—Part II: Heat Transfer Results

[+] Author and Article Information
Sean Jenkins

Institute of Aerospace Thermodynamics, University of Stuttgart, Pfaffenwaldring 31, 70569 Stuttgart, Germanysean.jenkins@itlr.uni-stuttgart.de

Jens von Wolfersdorf, Bernhard Weigand

Institute of Aerospace Thermodynamics, University of Stuttgart, Pfaffenwaldring 31, 70569 Stuttgart, Germany

Tim Roediger, Helmut Knauss, Ewald Kraemer

Institute of Aerodynamics and Gas Dynamics, University of Stuttgart, Pfaffenwaldring 21, 70569 Stuttgart, Germany

J. Turbomach 130(1), 011019 (Jan 28, 2008) (9 pages) doi:10.1115/1.2472417 History: Received July 24, 2006; Revised September 26, 2006; Published January 28, 2008

Measurements using a novel heat flux sensor were performed in an internal ribbed channel representing the internal cooling passages of a gas turbine blade. These measurements allowed for the characterization of heat transfer turbulence levels and unsteadiness not previously available for internal cooling channels. In the study of heat transfer, often the fluctuations can be equally as important as the mean values for understanding the heat loads in a system. In this study, comparisons are made between the time-averaged values obtained using this sensor and detailed surface measurements using the transient thermal liquid crystal technique. The time-averaged heat flux sensor and transient TLC results showed very good agreement, validating both methods. Time-resolved measurements were also corroborated with hot film measurements at the wall at the location of the sensor to better clarify the influence of unsteadiness in the velocity field at the wall on fluctuations in the heat flux. These measurements resulted in turbulence intensities of the velocity and heat flux of 20%. The velocity and heat flux integral length scales were about 60% and 35% of the channel width, respectively, resulting in a turbulent Prandtl number of 1.7 at the wall.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic top view and cross section of the test channel with 60deg ribs

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Figure 2

Diagram of test rig

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Figure 3

Centerline temperature profiles for positions upstream of the bend

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Figure 4

Schematic cross section of the ALTP heat flux sensor module

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Figure 8

Nusselt number for Site 1 normalized by the Dittus-Boelter equation and the relation given in Eq. 16

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Figure 9

Variation in the Nusselt number with Reynolds number for Sites 1 and 2 in log-log scale

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Figure 10

Heat flux and velocity time signals at Site 1 for Re=100,000

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Figure 11

Power spectral density of velocity versus frequency using a hot-film probe at Site 1

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Figure 12

Power spectral density of heat flux versus frequency using the ALTP heat flux sensor at Site 1

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Figure 13

Power spectral density of heat flux versus frequency using the ALTP heat flux sensor comparing Sites 1 and 2 at Re=100,000

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Figure 7

Variation in the Nusselt number with Reynolds number for Site 1 of the heat flux sensor

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Figure 6

Distribution of Nusselt number on the tip wall at Re=50,000 (a), 100,000, (b), 150,000 (c), and 200,000 (d)

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Figure 5

Distribution of Nusselt number on the tip wall at Re=100,000 (with schematic of secondary flows)

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