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Research Papers: Experimental Techniques

Heat Transfer Experiments in a Confined Jet Impingement Configuration Using Transient Techniques

[+] Author and Article Information
Florian Hoefler1

Nils Dietrich, Jens Wolfersdorf

 Institute of Aerospace Thermodynamics (ITLR), Universitaet Stuttgart, Pfaffenwaldring 31, D-70569 Stuttgart, Germany

1

Corresponding author.

J. Heat Transfer 133(9), 091601 (Jul 07, 2011) (9 pages) doi:10.1115/1.4003827 History: Received September 08, 2010; Revised March 10, 2011; Published July 07, 2011; Online July 07, 2011

A confined jet impingement configuration has been investigated in which the matter of interest is the convective heat transfer from the air flow to the passage walls. The geometry is similar to gas turbine blade cooling applications. The setup is distinct from usual cooling passages by the fact that no crossflow and no bulk flow directions are present. The flow exhausts through two staggered rows of holes opposing the impingement wall. Hence, a complex 3-D vortex system arises, which entails a complex heat transfer situation. The transient thermochromic liquid crystal (TLC) method was used in previous studies to measure the heat transfer on the passage walls. Due to the nature of these experiments, the fluid as well as the wall temperature vary with location and time. As a prerequisite of the transient TLC technique, the heat transfer coefficient is assumed to be constant over the transient experiment. Therefore, it is the scope of this article to qualify this assumption and to validate the results at discrete locations. For this purpose, fast response surface thermocouples and heat flux sensors were applied, in order to gain information on the temporal evolution of the wall heat fluxes. The linear relation between heat flux and temperature difference could be verified for all measurement sites. This validates the assumption of a constant heat transfer coefficient. Nusselt number evaluations from independent techniques show a good agreement, considering the respective uncertainty ranges. For all investigated sites, the Nusselt numbers range within ±9% of the values gained from the TLC measurement.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 5

Passage fluid temperature measurement locations

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Figure 6

Surface thermocouples measurements sites on wall C

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Figure 7

Schematic of cross section of the ALTP sensor module

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Figure 8

Fluid temperature evolution during transient experiment

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Figure 9

Dimensionless passage fluid temperature evolution during transient experiment

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Figure 10

Wall and jet total temperatures for two different temperature steps

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Figure 11

Wall heat flux versus temperature difference for two different temperature steps

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Figure 12

Wall heat flux versus temperatures at sites 1–4, surface TC and sensor data

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Figure 13

Nusselt numbers versus dimensionless wall temperature at sites 1–4

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Figure 4

Nusselt number distribution from TLC experiments at Re = 45,000

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Figure 3

Schematic of the test section geometry

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Figure 2

Schematic of the experimental facility

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Figure 1

Schematic of an impingement cooled midchord passage of a turbine blade

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