Research Papers: Micro/Nanoscale Heat Transfer

Critical Heat Flux of Water at Subatmospheric Pressures in Microchannels

[+] Author and Article Information
C.-J. Kuo

Department of Mechanical, Aerospace, and Nuclear Engineering,  Rensselaer Polytechnic Institute, Troy, NY 12180

Y. Peles1

Department of Mechanical, Aerospace, and Nuclear Engineering,  Rensselaer Polytechnic Institute, Troy, NY 12180pelesy@rpi.edu


Corresponding author.

J. Heat Transfer 130(7), 072403 (May 20, 2008) (7 pages) doi:10.1115/1.2909077 History: Received April 09, 2007; Revised July 31, 2007; Published May 20, 2008

Critical heat flux conditions for water at subatmospheric pressures in an array of silicon-based, 227μm hydraulic diameter, rectangular microchannels were experimentally studied. Experiments were conducted at exit pressures from 0.1atmto1atm, mass fluxes from 86kgm2sto303kgm2s, and an effective heat flux up to 444Wcm2. The annular flow pattern revealed during flow visualization and the high exit qualities at CHF conditions suggest dryout to be the CHF mechanism. An analysis, based on the experimental results and known CHF characteristics, on the dependency of the critical heat flux on various variables was performed. It was found that the boiling number at the CHF condition was approximately a constant.

Copyright © 2008 by American Society of Mechanical Engineers
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Figure 1

The ratio of the highest measured CHF to the maximum heat flux from the kinetic theory, qCHF″∕qmkv″, as a function of dimensionless exit pressure, pe∕pc

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Figure 2

(a) A CAD model of the microdevice; (b) geometry of the inlet orifice configuration (all units in μm)

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Figure 5

(a) The exit mass quality at CHF conditions as a function of mass flux; (b) CHF as a function of mass quality

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Figure 6

CHF as a function of mass flux

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Figure 3

Experiment setup

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Figure 4

Characteristic flow boiling morphologies

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Figure 7

The boiling number at CHF conditions as a function of liquid-to-vapor density ratio, ρl∕ρv



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