Research Papers: Jets, Wakes, and Impingement Cooling

An Experimental and Computational Heat Transfer Study of Pulsating Jets

[+] Author and Article Information
Yogen Utturkar, Mehmet Arik

 Thermal Systems Laboratory, General Electric Global Research, Niskayuna, NY 12309

Charles E. Seeley

 Lifing Technologies Laboratory, General Electric Global Research, Niskayuna, NY 12309

Mustafa Gursoy

 Pro Solutions USA, Inc., 1223 Peoples Avenue, Troy, NY 12180

LeCroy wave runner 6100.

J. Heat Transfer 130(6), 062201 (Apr 23, 2008) (10 pages) doi:10.1115/1.2891158 History: Received December 19, 2006; Revised June 25, 2007; Published April 23, 2008

Synthetic jets are meso or microscale fluidic devices, which operate on the “zero-net-mass-flux” principle. However, they impart a positive net momentum flux to the external environment and are able to produce the cooling effect of a fan sans its ducting, reliability issues, and oversized dimensions. The rate of heat removal from the thermal source is expected to depend on the location, orientation, strength, and shape of the jet. In the current study, we investigate the impact of jet location and orientation on the cooling performance via time-dependent numerical simulations and verify the same with experimental results. We firstly present the experimental study along with the findings. Secondly, we present the numerical models/results, which are compared with the experiments to gain the confidence in the computational methodology. Finally, a sensitivity evaluation has been performed by altering the position and alignment of the jet with respect to the heated surface. Two prime orientations of the jet have been considered, namely, perpendicular and cross jet impingement on the heater. It is found that if jet is placed at an optimum location in either impingement or cross flow position, it can provide similar enhancements.

Copyright © 2008 by American Society of Mechanical Engineers
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Figure 1

Experimental setup

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Figure 2

Typical IR image showing heater temperature distribution. (a) Natural convection, 1.56W heater power (maximum temperature=71.2°C). (b) Synthetic jet at 50Vrms and 4500Hz perpendicularly impinging on the heater center from a distance of 10mm at 1.56W heater power (maximum temperature=43.5°C).

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Figure 3

(a) illustration of hotwire location near the jet exit. (b) Typical velocity response tapped by the hotwire (50Vrms and 4500Hz).

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Figure 4

Variation of peak jet exit velocity with driving voltage amplitude

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Figure 5

Effect of driving frequency on heat transfer enhancement and peak jet exit velocity

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Figure 6

Experimental setup for power consumption measurements

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Figure 7

Synthetic power consumption with driving voltage

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Figure 8

Synthetic jet power consumption with frequency

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Figure 9

Schematic of a 2D synthetic jet model

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Figure 10

Effect of driving voltage on heat transfer enhancement

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Figure 11

Effect of axial distance on heat transfer enhancement

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Figure 12

Time-dependent velocity magnitude extracted from the computational domain at the hotwire location

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Figure 13

Variation of temperature rise and heat transfer enhancement along the heater surface

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Figure 14

Normalized vorticity and temperature rise at the beginning of the expulsion phase of the jet

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Figure 15

Time-averaged streamlines and synthetic jet velocity field

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Figure 16

Schematic of computational domain in the cross flow alignment

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Figure 17

Temperature variation on the heater surface for the two flow alignments

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Figure 18

Synthetic jet mode shapes. The squishy and Helmholtz modes are the dominant modes at lower frequencies. The bending mode occurs at higher frequencies. This mode simultaneously compresses and expands the volume of enclosed air, resulting in minimal flow.

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Figure 19

Flow versus frequency. The flow increases with frequency up to the first resident point.




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