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Research Papers: Micro/Nanoscale Heat Transfer

Flow Boiling Instabilities in Microchannels and Means for Mitigation by Reentrant Cavities

[+] 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

1

Corresponding author.

J. Heat Transfer 130(7), 072402 (May 16, 2008) (10 pages) doi:10.1115/1.2908431 History: Received March 08, 2007; Revised July 06, 2007; Published May 16, 2008

The ability of reentrant cavities to suppress flow boiling oscillations and instabilities in microchannels was experimentally studied. Suppression mechanisms were proposed and discussed with respect to various instability modes previously identified in microchannels. It was found that structured surfaces formed inside channel walls can assist mitigating the rapid bubble growth instability, which dominates many systems utilizing flow boiling in microchannels. This, in turn, delayed the parallel channel instability and the critical heat flux (CHF) condition. Experiments were conducted using three types of 200×253μm2 parallel microchannel devices: with reentrant cavity surface, with interconnected reentrant cavity surface, and with plain surface. The onset of nucleate boiling, CHF condition, and local temperature measurements were obtained and compared in order to study and identify flow boiling instability.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Range of active cavity size as a function of wall superheat for flow boiling of water for the current microchannels based on Hsu’s criteria (23)

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Figure 2

Pressure drop–mass flux curve for a uniformly heated channel (7)

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Figure 3

CAD models of (a) the heater and the thermistors on the back side of the microdevice, and (b) a single thermistor

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Figure 4

(a) Experimental setup and (b) microdevice package

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Figure 5

Substrate temperature as a function of effective heat flux for (a) Device 1NR, (b) Device 2IR, and (c) Device 3PW

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Figure 6

Substrate temperature, Ts, as a function of effective heat flux for the three microchannel devices

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Figure 7

Substrate temperature as a function of effective heat flux for G=303kg∕m2s. (a) Device 1NR and (b) Device 3PW.

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Figure 8

Effective heat flux at (a) ONB, (b) OFO, and (c) CHF for different mass fluxes and different types of microdevices

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Figure 9

(a) T2 as a function of effective heat flux for G=303kg∕m2s, and (b) Transient T2 for G=303kg∕m2s and qeff″=123W∕cm2

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Figure 10

(a) Transient local temperature for Device 1NR for G=303kg∕m2s, qeff″=142W∕cm2; (b) comparison of transient T2 for different heat fluxes for G=303kg∕m2s (Device 1NR)

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Figure 11

Boiling stages in unstable boiling flow for G=303kg∕m2s, qeff″=142W∕cm2 (Device 1NR): (a) bubble nucleation (Stage A), (b) vapor filling/dryout (Stage B), and (c) post-dryout/upstream flooding (Stage C)

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