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Research Papers

Transient Thermal Field Measurements in a High Aspect Ratio Channel Related to Transient Thermochromic Liquid Crystal Experiments

[+] Author and Article Information
Sean C. Jenkins

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

Igor V. Shevchuk, Jens von Wolfersdorf, Bernhard Weigand

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

J. Turbomach 134(3), 031002 (Jul 14, 2011) (10 pages) doi:10.1115/1.3106028 History: Received October 15, 2008; Revised November 24, 2008; Published July 14, 2011; Online July 14, 2011

Measurements of transient fluid temperature distributions were made in a high aspect ratio (4:1) internally ribbed two-pass channel relating to the measurement of heat transfer using the transient thermochromic liquid crystal (TLC) technique. The temperature field was measured at several positions leading up to and around the 180 deg bend in a two-passage channel to account for variations in the bulk temperature used as a reference for the transient TLC technique. The results showed that the normalized distribution of the temperature field was time invariant, an important result for the validation of heat transfer results using the transient TLC method. The normalized fluid temperature field was shown to be independent of the inlet temperature step and relatively independent of channel Reynolds number. Fluid temperature distributions were shown to be consistent over the length of the inlet channel; however, temperature field measurements made downstream of the bend exhibited a strong asymmetry. Finally, local temperature distributions were used to adjust the reference temperature used in calculating heat transfer coefficient distributions and to show the behavior of heat transfer due to 180 deg bends.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

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

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Figure 2

Diagram of test rig

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Figure 3

Schematic of procedure to build single time point temperature distributions from consecutive identical experiments

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Figure 4

Fluid temperature difference, ΔT, at Position 2 (11.7Dh upstream of the bend) at time t=5 s

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Figure 5

Comparison between normalized temperature distributions for temperature jumps of ΔT=28.9 K (LoT) and 41.5 K (HiT) measured at the inlet of the channel for Re=100,000

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Figure 6

Comparison between normalized temperature distributions for Reynolds numbers of Re=100,000 and 50,000

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Figure 7

Time invariance of temperature fields for Position 2, Re=100,000 at time points t=1, 2, 5, 10, and 15 s

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Figure 8

Comparisons between temperature fields computed by FLUENT ™ for a periodic rib segment and measurements at Position 2 for t=2.5 s

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Figure 9

Axial velocity distribution from CFD computation with streamtraces superimposed indicating secondary flows

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Figure 10

Comparison between centerline, area-weighted mean, and computed bulk average temperature time histories for Positions 2 and 3

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Figure 11

Inlet channel fluid temperature distributions for Positions 2 and 3 at t=5 s

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Figure 12

Outlet channel fluid temperature distributions for Positions 3.3, 4, and 5 at t=5 s

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Figure 13

Variation in mean temperature with axial position from the inlet at −11.7Dh to the outlet at +11.7Dh at time points of t=2.5, 5, and 10 s

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Figure 14

Comparison between measured and predicted mean temperature variations from the inlet at −11.7Dh to the outlet at +11.7Dh at a time point of t=5 s

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Figure 15

Measured mean time histories and predicted time histories for Positions 2, 3, 4, and 5

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Figure 16

Variation in height averaged normalized Nusselt number with axial position for the unribbed outer side wall

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Figure 17

Rib segment averaged Nusselt number for the smooth unribbed side wall and for the ribbed top wall

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