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Research Papers

Confined, Milliscale Unsteady Laminar Impinging Slot Jets: Effects of Slot Width on Surface Stagnation Point Nusselt Numbers

[+] Author and Article Information
Dae Hee Lee

Department of Mechanical
and Automotive Engineering,
High Safety Vehicle Core
Technology Research Center,
Inje University, 607 Obang-dong, Gimhae,
Gyeongnam 621-749, Korea

Jong Ryeol Bae

Department of Mechanical Engineering,
Graduate School,
Inje University,
607 Obang-dong, Gimhae,
Gyeongnam 621-749, Korea

Mira Ryu

BK21 Advanced Vehicle Core Parts
Research Group,
Inje University,
607 Obang-dong, Gimhae,
Gyeongnam 621-749, Korea

Phil Ligrani

Oliver L. Parks Endowed Chair,
Professor and Director of Graduate Programs,
Department of Aerospace and
Mechanical Engineering,
Parks College of Engineering,
Aviation, and Technology,
Saint Louis University,
3450 Lindell Boulevard,
McDonnell Douglas Hall Room 1033A,
St. Louis, MO 63103
e-mail: pligrani@slu.edu

1Corresponding author.

Contributed by the Electronic and Photonic Packaging Division of ASME for publication in the Journal of Electronic Packaging. Manuscript received July 19, 2011; final manuscript received May 31, 2012; published online September 4, 2012. Editor: Bahgat Sammakia.

J. Electron. Packag 134(4), 041004 (Sep 04, 2012) (11 pages) doi:10.1115/1.4007317 History: Received July 19, 2011; Revised May 31, 2012

The effects of slot width for confined, laminar impinging slot jets of millimeter-scale are considered, including experimental measurements of spatially resolved distributions of local Nusselt numbers measured on a constant heat flux surface. The effects of Reynolds number, nozzle-to-plate distance, and dimensional slot width on the local Nusselt number are investigated for slot nozzle width B values of 0.5 mm, 1.0 mm, and 1.5 mm. Reynolds numbers Re range from 120 to 200, nozzle-to-plate distances H/B vary from 0.75 to 12.5, and the nozzle aspect ratio y/B is 50. Observed are different stagnation point Nusselt number Nuo variations with Re, H/B, and B, where the onset of unsteadiness, and the intermittent flapping motion of the jet column are both associated with important variations to local, stagnation region Nusselt numbers Nuo, as experimental configuration and condition change. The variations of these stagnation-point Nusselt numbers associated with these two modes of unsteadiness are characterized by correlations which provide the dependence upon Reynolds number and normalized nozzle-to-plate distance ratio, H/B, for different dimensional values of B. Also presented are stagnation region Nusselt number variations, for steady, impingement jets at values of H/B less than 4.6–7.8. These are characterized by three separate regimes of behavior, each of which shows significantly different Nuo dependence upon Re, H/B, and B.

Copyright © 2012 by ASME
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References

Figures

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Fig. 2

Arrangement of the slot nozzle and flow channel, including the coordinate system

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Fig. 1

Experimental apparatus employed for the investigation

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Fig. 3

Comparison of the lateral variation of local Nusselt number from different investigations for H/B of 5 and 6, and for Re of 120 and 125

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Fig. 4

Lateral variation of local Nusselt numbers for Re = 160 with a nozzle width B of 1.0 mm

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Fig. 5

Variation of stagnation point, local Nusselt numbers with H/B for a Reynolds number of 120 for nozzle widths B of 0.5 mm, 1.0 mm, and 1.5 mm

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Fig. 6

Variation of stagnation point, local Nusselt numbers with H/B for a Reynolds number of 140 for nozzle widths B of 0.5 mm, 1.0 mm, and 1.5 mm

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Fig. 7

Variation of stagnation point, local Nusselt numbers with H/B for a Reynolds number of 160 for nozzle widths B of 0.5 mm, 1.0 mm, and 1.5 mm

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Fig. 8

Variation of stagnation point, local Nusselt numbers with H/B for a Reynolds number of 180 for nozzle widths B of 0.5 mm, 1.0 mm, and 1.5 mm

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Fig. 9

Variation of stagnation point, local Nusselt numbers with H/B for a Reynolds number of 200 for nozzle widths B of 0.5 mm, 1.0 mm, and 1.5 mm

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Fig. 10

Variation of stagnation point, local Nusselt numbers with Reynolds number Re and nozzle slot width B for H/B = 2.0

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Fig. 11

Variation of stagnation point, local Nusselt numbers with Reynolds number Re and nozzle slot width B for H/B = 5.0

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Fig. 12

Variation of stagnation point, local Nusselt numbers with H/B for Reynolds numbers from 120 to 200 for a nozzle width B of 0.5 mm

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Fig. 13

Variation of stagnation point, local Nusselt numbers with H/B for Reynolds numbers from 120 to 200 for a nozzle width B of 1.0 mm. Symbols are defined in Fig. 12.

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Fig. 14

Variation of stagnation point, local Nusselt numbers with H/B for Reynolds numbers from 120 to 200 for a nozzle width B of 1.5 mm. Symbols are defined in Fig. 12.

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Fig. 15

Variation of stagnation point, local Nusselt numbers with Reynolds number (for different H/B values) for nozzle slot widths B of 0.5 mm, 1.0 mm, and 1.5 mm for the experimental conditions which correspond to the onset of unsteadiness of the jet column within the impingement channel

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Fig. 16

Variation of stagnation point, local Nusselt numbers with Reynolds number (for different H/B values) for nozzle slot widths B of 0.5 mm, 1.0 mm, and 1.5 mm for the experimental conditions which correspond to intermittent oscillating motion of the jet column within the impingement channel

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Fig. 17

Experimental domain map showing the experimental conditions for different types of unsteady jet behavior in H/B and Reynolds number coordinates. Symbols are defined in Fig. 9.

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