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Research Papers: Forced Convection

Electrohydrodynamic Microfabricated Ionic Wind Pumps for Thermal Management Applications

[+] Author and Article Information
Andojo Ongkodjojo Ong

Mem. ASME
Department of Electrical Engineering
and Computer Science,
Case Western Reserve University,
Cleveland, OH 44106
e-mail: axo50@case.edu

Alexis R. Abramson

Mem. ASME
Department of Mechanical
and Aerospace Engineering,
Case Western Reserve University,
Cleveland, OH 44106
e-mail: ara9@case.edu

Norman C. Tien

Department of Electrical Engineering
and Computer Science,
Case Western Reserve University,
Cleveland, OH 44106
e-mail: nctien@hku.hk

1Corresponding author.

2Present address: Commonwealth Scientific and Industrial Research Organization (CSIRO), Computational Informatics, Hobart, Tasmania 7001, Australia.

3Present address: Faculty of Engineering, University of Hong Kong.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received February 18, 2013; final manuscript received January 29, 2014; published online March 11, 2014. Assoc. Editor: Ali Khounsary.

J. Heat Transfer 136(6), 061703 (Mar 11, 2014) (11 pages) Paper No: HT-13-1088; doi: 10.1115/1.4026807 History: Received February 18, 2013; Revised January 29, 2014

This work demonstrates an innovative microfabricated air-cooling technology that employs an electrohydrodynamic (EHD) corona discharge (i.e., ionic wind pump) for electronics cooling applications. A single, microfabricated ionic wind pump element consists of two parallel collecting electrodes between which a single emitting tip is positioned. A grid structure on the collector electrodes can enhance the overall heat-transfer coefficient and facilitate an IC compatible batch process. The optimized devices studied exhibit an overall device area of 5.4 mm × 3.6 mm, an emitter-to-collector gap of ∼0.5 mm, and an emitter curvature radius of ∼12.5 μm. The manufacturing process developed for the device uses glass wafers, a single mask-based photolithography process, and a low-cost copper-based electroplating process. Various design configurations were explored and modeled computationally to investigate their influence on the cooling phenomenon. The single devices provide a high heat-transfer coefficient of up to ∼3200 W/m2 K and a coefficient of performance (COP) of up to ∼47. The COP was obtained by dividing the heat removal enhancement, ΔQ by the power consumed by the ionic wind pump device. A maximum applied voltage of 1.9 kV, which is equivalent to approximately 38 mW of power input, is required for operation, which is significantly lower than the power required for the previously reported devices. Furthermore, the microfabricated single device exhibits a flexible and small form factor, no noise generation, high efficiency, large heat removal over a small dimension and at low power, and high reliability (no moving parts); these are characteristics required by the semiconductor industry for next generation thermal management solutions.

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References

Figures

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Fig. 3

Image of a single microfabricated ionic wind pump device [4]. When a threshold high voltage is applied between the emitter tip and the collector electrodes, the corona discharge results in a visible purple haze around the emitter (inset).

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Fig. 2

Design schematic of the mask plot used to microfabricate a single ionic wind pump element, and schematic of the single ionic wind pump device consisting of an emitter and two parallel collector plates (inset)

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Fig. 1

Schematic of the EHD ionic wind pump with a positive corona discharge; the resulting flow pattern with air jet impingement is clearly shown. The ion stream is being generated by the ionic wind pump, where a dc high voltage (HV) is applied between the emitting electrode and the collecting electrodes. The ionic wind pump also shows the ionizing zone and accelerating zone. For this work, the collector electrodes are gridded, which facilitates a batch fabrication process.

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Fig. 8

I–V curves for the microfabricated ionic wind pump devices employing positive coronas

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Fig. 9

Experimental results of (a) temperature drop (ΔTdrop), (b) heat-transfer coefficient (hon), and (c) COP resulting from operation of the single ionic wind pump device as a function of electrical power consumption of the ionic wind pump device

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Fig. 4

Computational simulation results of the ionic wind pump device configuration (top view) for (a) the nongridded, solid collector electrode with the ionic wind “off” (left) and “on” (right); and (b) the gridded collector electrode with a hole size of 400 μm with the ionic wind “off” (left) and “on” (right). The emitter is located at the midpoint of the length of the left boundary on all images.

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Fig. 5

Computational simulations of the ionic wind pump device (top view) demonstrating different temperature distributions and velocity flow fields for the different emitter positions. (a) Emitter location is located at one-quarter of the length of the left boundary (design II). (b) Emitter location is located at one-eighth of the length of the left boundary (design III). The size of the emitter is exaggerated in the figure for emphasis.

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Fig. 6

Computational simulations of the ionic wind pump device (top view), demonstrating the different temperature distributions and velocity flow fields of the device with the smallest gap and for (a) the ionic wind “off” and (b) the ionic wind “on”. For simplicity, nongridded collector electrodes were used for this comparison. The emitter is located in the middle of the length of the left boundary.

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Fig. 7

Schematic diagram of the measurement setup used to thermally characterize the ionic wind pump devices. Also shown are the source of energy input from the heater and the outputs of heat to ambient.

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