Research Papers

Flow Boiling of Coolant (HFE-7000) Inside Structured and Plain Wall 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 131(12), 121011 (Oct 15, 2009) (9 pages) doi:10.1115/1.3220674 History: Received November 13, 2008; Revised May 19, 2009; Published October 15, 2009

Flow boiling was experimentally studied using coolant HFE-7000 for two types of parallel microchannels: a plain-wall microchannel and a microchannel with structured reentrant cavities on the side walls. Flow morphologies, boiling inceptions, heat transfer coefficients, and critical heat fluxes were obtained and studied for mass fluxes ranging from G=164kg/m2s to G=3025kg/m2s and mass qualities (energy definition) ranging from x=0.25 to x=1. Comparisons of the performance of the enhanced and plain-wall microchannels were carried out. It was found that reentrant cavities were effective in reducing the superheat at the onset of nucleate boiling and increasing the heat transfer coefficient. However, they did not seem to increase the critical heat flux.

Copyright © 2009 by American Society of Mechanical Engineers
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Figure 1

(a) A SEM image of the reentrant cavities, (b) a CAD model of the heater and the thermistors on the backside of the microdevice, and (c) a CAD model of a single thermistor

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Figure 2

Experiment setup

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Figure 3

Flow morphologies: (a) bubbly flow for G=1615 kg/m2 s, qeff″=65.8 W/cm2, and x=−0.08; (b) oscillating single-phase liquid/single bubble/slug tail for G=303 kg/m2 s, qeff″=11.9 W/cm2, and x=−0.08; (c) churn flow for G=303 kg/m2 s, qeff″=34.4 W/cm2, and x=0.23; (d) wispy annular flow for G=303 kg/m2 s, qeff″=38.9 W/cm2, and x=0.28; (e) inverted annular flow for G=303 kg/m2 s, qeff″=53.0 W/cm2, and x=0.75.

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Figure 4

Flow map for G=154–3025 kg/m2 s

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Figure 5

Effective heat flux at ONB for different mass fluxes

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Figure 6

Heat transfer coefficient as a function of channel heat flux for different mass fluxes

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Figure 7

(a) qCHF″, (b) BoCHF, and (c) xe,CHF as a function of mass flux

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Figure 8

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



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