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RESEARCH PAPERS: Micro/Nanoscale Heat Transfer

Stabilization of Flow Boiling in Microchannels Using Pressure Drop Elements and Fabricated Nucleation Sites

[+] Author and Article Information
Satish G. Kandlikar1

Thermal Analysis and Microfluidics Laboratory, Mechanical Engineering Department, Rochester Institute of Technology, Rochester, New York, 14623sgkeme@rit.edu

Wai Keat Kuan

Thermal Analysis and Microfluidics Laboratory, Mechanical Engineering Department, Rochester Institute of Technology, Rochester, New York, 14623wxk0320@rit.edu

Daniel A. Willistein

Thermal Analysis and Microfluidics Laboratory, Mechanical Engineering Department, Rochester Institute of Technology, Rochester, New York, 14623daw7820@rit.edu

John Borrelli

Thermal Analysis and Microfluidics Laboratory, Mechanical Engineering Department, Rochester Institute of Technology, Rochester, New York, 14623jxb9224@rit.edu

1

Corresponding author.

J. Heat Transfer 128(4), 389-396 (Dec 02, 2005) (8 pages) doi:10.1115/1.2165208 History: Received April 04, 2005; Revised December 02, 2005

The flow boiling process suffers from severe instabilities induced due to nucleation of vapor bubbles in a superheated liquid environment in a minichannel or a microchannel. In an effort to improve the flow boiling stability, several modifications are introduced and experiments are performed on 1054×197μm parallel rectangular microchannels (hydraulic diameter of 332μm) with water as the working fluid. The cavity sizes and local liquid and wall conditions required at the onset of nucleation are analyzed. The effects of an inlet pressure restrictor and fabricated nucleation sites are evaluated as a means of stabilizing the flow boiling process and avoiding the backflow phenomenon. The results are compared with the unrestricted flow configurations in smooth channels.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 8

Test section details

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Figure 9

Cross section views of inlet restriction details

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Figure 10

Flow reversal in 51% area pressure drop manifold with no artificial nucleation sites. Successive frames from (a) to (f) taken at 1.67ms time interval illustrating partially stabilized flow in a single channel from a set of six parallel horizontal microchannels. G=120kg∕m2s, q″=308kW∕m2, Ts=113°C.

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Figure 11

Laser drilled holes on microchannel surface. Cavity in image (a) has an average diameter of 8μm and cavity in image (b) has an average diameter of 22μm.

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Figure 12

Unstable flow with 51% area pressure drop elements and fabricated nucleation sites. Successive frames from (a) to (e) taken at 1.17ms time interval illustrating normal flow reversal in a single channel from a set of six parallel horizontal microchannels. G=120kg∕m2s, q″=298kW∕m2, Ts=112.4°C.

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Figure 13

Stable flow with 4% area pressure drop elements and fabricated nucleation sites. Successive frames from (a) to (f) taken at 11.7ms time intervals illustrating extremely stabilized flow in a single channel from a set of six parallel horizontal microchannels. G=120kg∕m2s, q″=298kW∕m2, Ts=111.5°C.

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Figure 14

Comparison of transient pressure drop data across microchannels and pressure drop elements

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Figure 1

Location of the stagnation point over a nucleating bubble, Kandlikar (18)

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Figure 2

Comparison of experimental data with different nucleation criteria (representing the lowest wall superheat at which a cavity will nucleate), Kandlikar (18)

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Figure 3

Range of active cavities given by Eq. 2 for a given wall superheat, saturated water in 1054×197μm channel, G=120kg∕m2s; q″=300kW∕m2

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Figure 6

Local wall and liquid temperatures corresponding to onset of nucleation over a given cavity radius, water in 1054×50μm channel, G=120kg∕m2s; q″=300kW∕m2

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Figure 7

Water supply loop and test section

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Figure 4

Local wall superheat and liquid subcooling corresponding to onset of nucleation over a given cavity radius, Eqs. 3,4, water in 1054×197μm channel, G=120kg∕m2s; q″=300kW∕m2

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Figure 5

Local wall and liquid temperatures corresponding to onset of nucleation over a given cavity radius, replotted data from Fig. 4, water in 1054×197μm channel, G=120kg∕m2s; q″=300kW∕m2

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