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Research Papers: Electronic Cooling

Enhanced Flow Boiling Over Open Microchannels With Uniform and Tapered Gap Manifolds

[+] Author and Article Information
Satish G. Kandlikar

Fellow ASME
e-mail: sgkeme@rit.edu

Valentina Mejia

Mechanical Engineering Department,
Rochester Institute of Technology,
Rochester, NY 14623

1Corresponding author.

Manuscript received October 4, 2012; final manuscript received January 15, 2013; published online May 16, 2013. Assoc. Editor: Leslie Phinney.

J. Heat Transfer 135(6), 061401 (May 16, 2013) (9 pages) Paper No: HT-12-1537; doi: 10.1115/1.4023574 History: Received October 04, 2012; Revised January 15, 2013

Flow boiling in microchannels has been extensively studied in the past decade. Instabilities, low critical heat flux (CHF) values, and low heat transfer coefficients have been identified as the major shortcomings preventing its implementation in practical high heat flux removal systems. A novel open microchannel design with uniform and tapered manifolds (OMM) is presented to provide stable and highly enhanced heat transfer performance. The effects of the gap height and flow rate on the heat transfer performance have been experimentally studied with water. The critical heat fluxes (CHFs) and heat transfer coefficients obtained with the OMM are significantly higher than the values reported by previous researchers for flow boiling with water in microchannels. A record heat flux of 506 W/cm2 with a wall superheat of 26.2 °C was obtained for a gap size of 0.127 mm. The CHF was not reached due to heater power limitation in the current design. A maximum effective heat transfer coefficient of 290,000 W/m2 °C was obtained at an intermediate heat flux of 319 W/cm2 with a gap of 0.254 mm at 225 mL/min. The flow boiling heat transfer was found to be insensitive to flow rates between 40–333 mL/min and gap sizes between 0.127–1.016 mm, indicating the dominance of nucleate boiling. The OMM geometry is promising to provide exceptional performance that is particularly attractive in meeting the challenges of high heat flux removal in electronics cooling applications.

Copyright © 2013 by ASME
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References

Figures

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Fig. 1

Comparison of enhanced pool boiling performance reported in the literature

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Fig. 2

Schematic of the open microchannels with tapered manifolds for stable enhanced flow boiling

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Fig. 3

Schematic of the test section and the heater assembly

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Fig. 4

Schematic of the 3 mm thick copper microchannel chip with a 217 μm wide, 162 μm deep, and 160 μm fin width in the central 10 mm × 10 mm region (left image), and a 2 mm wide × 2 mm deep groove on the underside (right image)

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Fig. 5

Pressure drop fluctuations over a 20 sec period at different heat fluxes for uniform (UM) and tapered (TM) manifolds, S = 0.127 mm and V = 80 mL/min

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Fig. 6

Successive images taken at 8 ms time intervals for unstable flow boiling on a plain chip surface with the uniform manifold V = 103 mL/min and S = 1.524 mm

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Fig. 7

Successive images taken at a 3 ms time interval for stable flow boiling on a plain chip surface with the tapered manifold V = 74 mL/min and S = 1.524 mm

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Fig. 8

Comparison of boiling performance for the tapered (TM) and uniform (UM) manifold blocks with V = 225 mL/min, V = 40 mL/min, and S = 0.127 mm

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Fig. 9

Effect of the manifold depth on the boiling performance for the tapered manifold block, the microchannel test chip with V = 40 and 225 mL/min and S = 0.127 and 0.254 mm

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Fig. 10

Comparison of boiling performance for the microchannel and plain chips with the uniform manifold block with V = 333 and 225 mL/min and S = 0.254 mm

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Fig. 11

Dry surfaces (outlined regions are shown inside the bubble region) of a plain (left image), and the microchannel test chip (right image) under a bubble

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Fig. 12

Effect of the manifold depth on the boiling performance with the uniform manifold block and the microchannel test chip with V = 333 mL/min and S = 0.127 mm, 0.254, 0.508, 1.016, and 1.524 mm

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Fig. 13

Effect of the manifold depth on the pressure drop with the uniform manifold block and the microchannel test chip with V = 225 mL/min for S = 0.127 and 0.508 mm

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Fig. 14

Effect of the flow rate on the boiling curves with the uniform manifold block and the microchannel test chip with V = 333, 225, 152, 80, and 40 mL/min and S = 0.127 mm

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Fig. 15

Effect of the flow rate on the boiling curves with the uniform manifold block and the microchannel test chip with V = 333, 225, and 152 mL/min and S = 0.254 mm

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Fig. 16

Effect of the flow rate on the boiling curves with the uniform manifold block and the microchannel test chip with V = 333, 225 and 152 mL/min and S = 1.524 mm

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Fig. 17

A heat transfer coefficient versus heat flux comparison between pool boiling and flow boiling with the uniform manifold block, the microchannel test chip, and V = 152 mL/min and S = 0.127 mm

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