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Research Papers

Design and Evaluation of a MEMS-Based Stirling Microcooler

[+] Author and Article Information
Dongzhi Guo, Alan J. H. McGaughey

Department of Mechanical Engineering,
Carnegie Mellon University,
Pittsburgh, PA 15213-3890

Jinsheng Gao, Gary K. Fedder

Department of Electrical and Computer
Engineering,
Carnegie Mellon University,
Pittsburgh, PA 15213-3890

Matthew Moran

Isotherm Technologies LLC,
Medina, OH 44256-6431

Shi-Chune Yao

Department of Mechanical Engineering,
Carnegie Mellon University,
Pittsburgh, PA 15213-3890
e-mail: scyao@cmu.edu

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the Journal of Heat Transfer. Manuscript received March 31, 2012; final manuscript received August 30, 2012; published online September 23, 2013. Assoc. Editor: Sujoy Kumar Saha.

J. Heat Transfer 135(11), 111003 (Sep 23, 2013) (7 pages) Paper No: HT-12-1144; doi: 10.1115/1.4024596 History: Received March 31, 2012; Revised August 30, 2012

A new Stirling microrefrigeration system composed of arrays of silicon MEMS cooling elements has been designed and evaluated. The cooling elements are to be fabricated in a stacked array on a silicon wafer. A regenerator is placed between the compression (hot side) and expansion (cold side) diaphragms, which are driven electrostatically. Air at a pressure of 2 bar is the working fluid and is sealed in the system. Under operating conditions, the hot and cold diaphragms oscillate sinusoidally and out of phase such that heat is extracted to the expansion space and released from the compression space. Parametric study of the design shows the effects of phase lag between the hot space and cold space, swept volume ratio between the hot space and cold space, and dead volume ratio on the cooling power. Losses due to regenerator nonidealities are estimated and the effects of the operating frequency and the regenerator porosity on the cooler performance are explored. The optimal porosity for the best system coefficient of performance (COP) is identified.

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References

Figures

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Fig. 1

Stirling microcooler alternatives in cross section: (a) The Moran concept [8,9-8,9] uses silicon diaphragms with vertical electrostatic comb drives to move the working gas through a regenerator vertically (i.e., perpendicular to the plane of the silicon wafer). (b) The current in-plane microscale implementation positions the regenerator flow channel parallel to the wafer plane connecting the compression and expansion chambers, allowing for thermal isolation.

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Fig. 2

Solid-model view of the Stirling microcooler elements. (a) A single element is 5 mm-long, 2.5 mm-wide, has a thickness of 150 μm, and is fabricated on a silicon wafer. (b) The assembled structure has five parts: the diaphragm layer in the middle, the top and bottom chamber substrates, and two sealing PDMS layers.

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Fig. 3

Vision of the arrayed Stirling microcooler. A 2 × 2 cm2 cooling area is made by first arraying eight elements along their width and then stacking 114 of these 1 × 8 arrays.

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Fig. 4

The ideal Stirling refrigeration cycle includes four processes: isothermal compression (1–2), regenerative cooling (2–3), isothermal expansion (3–4), and regenerative heating (4–1)

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Fig. 5

Sinusoidal volume variation of the cold side, hot side, and the total system volume in the Stirling cycle. The numerical labels are similar to those in Fig. 4.

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Fig. 6

Geometric parameters for a microcooler element. The dead volume, VD, includes the regenerator volume, Vr, and the non swept volume between the regenerator and the chambers, Vns. VC and VH are the swept volume in the cold and hot chambers.

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Fig. 7

Dimensionless heat extraction as a function of swept volume ratio for different non swept volume ratios. The lead phase angle of the cold side to the hot side is 90 deg.

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Fig. 8

Dimensionless heat extraction as a function of lead phase angle for different swept volume ratios. The non swept volume ratio χVns is 0.4.

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Fig. 9

System sketch of the single Stirling microcooler element and the energy balance in each chamber. Tg,C and Tg,H are the gas temperature in the cold and hot chambers. The heat source temperature is TC and the heat sink temperature is TH.

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Fig. 10

System COP as a function of regenerator porosity at different operating frequencies. The swept volume ratio is unity for the two chambers and the phase lag of the volume variations between the cold and hot sides is 90 deg.

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Fig. 11

System cooling capacity as a function of the operating frequency at different porosities. The swept volume ratio is unity for the two chambers and the phase lag of the volume variations between the cold and hot sides is 90 deg.

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