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Research Papers

Heat and Mass Transfer Caused by a Laminar Channel Flow Equipped With a Synthetic Jet Array

[+] Author and Article Information
Zdeněk Trávníček1

 Institute of Thermomechanics AS CR, v. v. i., Dolejškova 5, Prague 182 00, Czech Republictr@it.cas.cz

Petra Dančová

 Technical University of Liberec, Studentská 2, Liberec 461 17, Czech Republic; Institute of Thermomechanics AS CR, v. v. i., Dolejškova 5, Prague 182 00, Czech Republicpetra.dancova@tul.cz

Jozef Kordík

 Institute of Thermomechanics AS CR, v. v. i., Dolejškova 5, Prague 182 00, Czech Republickordik@it.cas.cz

Tomáš Vít

 Technical University of Liberec, Studentská 2, Liberec 461 17, Czech Republic; Institute of Thermomechanics AS CR, v. v. i., Dolejškova 5, Prague 182 00, Czech Republictomas.vit@tul.cz

Miroslav Pavelka

 Institute of Thermomechanics AS CR, v. v. i., Dolejškova 5, Prague 182 00, Czech Republicpavelka@it.cas.cz

1

Corresponding author.

J. Thermal Sci. Eng. Appl 2(4), 041006 (Feb 08, 2011) (8 pages) doi:10.1115/1.4003428 History: Received September 14, 2010; Revised January 02, 2011; Published February 08, 2011

Low Reynolds number laminar channel flow is used in various heat/mass transfer applications such as cooling and mixing. A low Reynolds number implies a low intensity of heat/mass transfer processes since they rely only on the gradient diffusion. To enhance these processes, an active flow control by means of synthetic (zero-net-mass-flux) jets is proposed. The present study is experimental, in which a Reynolds number range of 200–500 is investigated. Measurement has been performed mainly in air as the working fluid by means of hot-wire anemometry and the naphthalene sublimation technique. Particle image velocimetry (PIV) experiments in water are also discussed. The experiments have been performed in macroscale at the channel cross sections (20×100)mm and (40×200)mm in air and water, respectively. The results show that the low Reynolds number channel flow can be influenced by an array of synthetic jets. The effect of synthetic jets on the heat transfer enhancement is quantified. The stagnation Nusselt number is enhanced by 10–30 times in comparison with the nonactuated channel flow. The results indicate that the present arrangement can be a useful tool for heat transfer enhancement in various applications, e.g., cooling and mixing.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Diagram of the present configuration for air as the working fluid: (a) top view showing array of four orifices of SJ actuators and (b) side view

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Figure 2

Frequency characteristic of the SJ actuator (air as the working fluid)

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Figure 3

Measurement of diaphragm deflection

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Figure 4

CTA measurement of the centerline velocity in the actuator orifice: phase averaged velocity

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Figure 5

Phase averaged PIV experiment in water: two central SJs in plane III during the actuating cycle for t/T=0, 0.25, 0.5, and 0.75

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Figure 6

Velocity magnitude profiles of SJs at the beginning of the actuation cycle t/T=0 in plane III

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Figure 7

Phase averaged velocity magnitude profiles of SJs at y/H=0.5, during the actuation cycle, in plane III

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Figure 8

Local heat/mass transfer distribution along the channel wall without SJs

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Figure 9

Local heat/mass transfer distribution on the exposed channel wall at ReC=250

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Figure 10

Local heat transfer coefficient along plane II of the channel wall: channel flow under SJs influence

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Figure 11

Stagnation Nusselt number, and comparison with data by Valiorgue (22)

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