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Research Papers: Evaporation, Boiling, and Condensation

Enhanced Flow Boiling Using Radial Open Microchannels With Manifold and Offset Strip Fins

[+] Author and Article Information
Alyssa Recinella

Mechanical Engineering Department,
Rochester Institute of Technology,
76 Lomb Memorial Dr.,
Rochester, NY 14623
e-mail: anr6832@rit.edu

Satish G. Kandlikar

Fellow ASME
Mechanical Engineering Department,
Rochester Institute of Technology,
76 Lomb Memorial Dr.,
Rochester, NY 14623;
Microsystems Engineering Department,
Rochester Institute of Technology,
76 Lomb Memorial Dr.,
Rochester, NY 14623
e-mail: sgkeme@rit.edu

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received January 12, 2017; final manuscript received July 4, 2017; published online September 26, 2017. Assoc. Editor: Guihua Tang.

J. Heat Transfer 140(2), 021502 (Sep 26, 2017) (9 pages) Paper No: HT-17-1018; doi: 10.1115/1.4037644 History: Received January 12, 2017; Revised July 04, 2017

The increasing demand for designing effective cooling solutions in high power density electronic components has resulted in exploring advanced thermal management strategies. Over the past decade, phase-change cooling has received widespread recognition due to its ability to dissipate large heat fluxes while maintaining low temperature differences. In this paper, a radial flow boiling configuration through a central inlet was studied. This configuration is particularly suited for chip cooling application. Two heat transfer surfaces with (a) radial microchannels, and (b) offset strip fins were fabricated and their flow boiling performance with distilled water was obtained. Furthermore, the effect of the liquid flow rate on the boiling performance and enhancement mechanisms was also investigated in this study. At a flow rate of 240 mL/min, a maximum heat flux of 369 W/cm2 at a wall superheat of 49 °C and a pressure drop of 59 kPa was achieved with the radial microchannels, while the offset strip fins achieved a maximum heat flux of 618 W/cm2 at a wall superheat of 20 °C. Increasing the flow rate to 320 mL/min resulted in a heat flux of 897 W/cm2 demonstrating the potential of using a radial configuration for enhancing the boiling performance. The increase in flow cross-sectional area was shown to be responsible for the reduced pressure drop when compared to straight microchannel configurations. The high-speed imaging incorporated in each test provided valuable insight and understanding into the flow patterns and underlying mechanism in these geometries. With the ease of implementation, highly stable flow, and further optimization possibilities with different microchannel and taper configurations, the radial geometry is expected to provide significant performance enhancement well beyond a critical heat flux (CHF) of 1 kW/cm2.

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References

Figures

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Fig. 1

Flow loop used for experimentation

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Fig. 2

Copper components used for experimentation: (a) copper heater, (b) radial microchannels, and (c) offset strip fins

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Fig. 3

(a) Polysulfone manifold with one central inlet and four outlets and either side of the test surface, (b) manifold cross section of closed microchannels, and (c) open microchannels

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Fig. 4

Heat transfer performance for radial and offset strip fingeometries in an open configuration at flow rates of 120mL/min and 240 mL/min

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Fig. 5

Pressure drop performance for radial and offset strip fingeometries in an open configuration at flow rates of 120mL/min and 240 mL/min

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Fig. 6

Heat transfer performance for radial microchannels and offset strip fins with closed and open configurations for a flow rate of 240 mL/min

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Fig. 7

Pressure drop performance for radial microchannels and offset strip fins with closed and open configurations for a flow rate of 240 mL/min

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Fig. 8

Heat transfer performance for the offset strip fin geometry with an open manifold configuration using flow rates 120mL/min, 240 mL/min, and 320 mL/min

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Fig. 9

Pressure drop performance for the offset strip fin geometry with an open manifold configuration using flow rates 120mL/min, 240 mL/min, and 320 mL/min

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Fig. 10

Heat transfer performance for the offset strip fin geometry with an open manifold configuration using two separate gaps of 127 μm and 250 μm and flow rates of 120 mL/min and 240 mL/min

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Fig. 11

Pressure drop performance for the offset strip fin geometry with an open manifold configuration using two separate gaps of 127 μm and 250 μm and differing flow rates 120 mL/min and 240 mL/min

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Fig. 12

Radial microchannels in a closed configuration tested at 120 mL/min; (a) vapor blockages observed in left side of chip. A large vapor bubble is observed sitting in several channels. (b) The vapor moves upstream throughout the channels to exit through the bottom left outlet.

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Fig. 13

Offset strip fins in a closed configuration tested at 120 mL/min; (a) and (b) vapor freely moves throughout system to exit through outlet in bottom right corner and (c) and (d) coalesced vapor bubble broken up by strip fins, individual bubble streams are created

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Fig. 14

High-speed imaging of flow through offset strip fins ina closed configuration at (a) a flow rate of 240 mL/min and q″ = 174 W/cm2 and (b) a flow rate of 320 mL/min and q″ = 160 W/cm2

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Fig. 15

Radial microchannels at a flow rate of 240 mL/min (a) in a closed configuration, vapor blockages, and flow channeling can be seen, while (b) an open configuration creates a more developed, bubbly flow

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