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MICRO/NANOSCALE HEAT TRANSFER—PART II

Experimental Study of Flow Critical Heat Flux in Alumina-Water, Zinc-Oxide-Water, and Diamond-Water Nanofluids

[+] Author and Article Information
Sung Joong Kim, Tom McKrell, Lin-Wen Hu

 Massachusetts Institute of Technology (MIT), 77 Massachusetts Avenue, Cambridge, MA 02139-4307

Jacopo Buongiorno

 Massachusetts Institute of Technology (MIT), 77 Massachusetts Avenue, Cambridge, MA 02139-4307jacopo@mit.edu

J. Heat Transfer 131(4), 043204 (Feb 13, 2009) (7 pages) doi:10.1115/1.3072924 History: Received April 14, 2008; Revised July 31, 2008; Published February 13, 2009

It is shown that addition of alumina, zinc-oxide, and diamond particles can enhance the critical heat flux (CHF) limit of water in flow boiling. The particles used here were in the nanometer range (<100nm) and at low concentration (0.1vol%). The CHF tests were conducted at 0.1 MPa and at three different mass fluxes (1500kg/m2s, 2000kg/m2s, and 2500kg/m2s). The thermal conditions at CHF were subcooled. The maximum CHF enhancement was 53%, 53%, and 38% for alumina, zinc oxide, and diamond, respectively, always obtained at the highest mass flux. A postmortem analysis of the boiling surface reveals that its morphology is altered by deposition of the particles during boiling. Additionally, the wettability of the surface is substantially increased, which seems to correlate well with the observed CHF enhancement.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of the flow loop

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Figure 2

The test-section schematic (a) and photo (b)

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Figure 3

Axial distribution of the heat flux at different power levels. Location 1 corresponds to the test-section exit and location 10 to the test-section entrance.

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Figure 4

Percentage difference between measured and predicted local Nusselt number. Location 1 corresponds to the test-section exit. The large discrepancy after the entrance (locations 11–12) is due to the thermal entrance effect, which is not accounted for in the Gnielinski correlation.

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Figure 5

Heat loss in the test section as a function of the heat flux

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Figure 6

Wall temperature and heat flux history in a typical CHF run

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Figure 7

Measured CHF values for water at atmospheric pressure

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Figure 8

Measured CHF values for alumina/water nanofluids at atmospheric pressure

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Figure 9

Measured CHF values for zinc-oxide/water and diamond/water nanofluids at atmospheric pressure

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Figure 10

Schematic of test coupons cut with EDM technique

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Figure 11

SEM pictures of stainless steel test heaters (a) as-received, and after being boiled in (b) pure water, (c) 0.001 vol %Al2O3, (d) 0.01 vol %Al2O3, and (e) 0.1 vol %Al2O3. (f) EDS clearly shows the presence of alumina on a surface boiled in alumina nanofluid.

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Figure 12

Contact angle of water sessile droplets for test section (a) as-purchased, (b) boiled in water (at G=2500 kg/m2 s), (c) boiled in 0.001 vol % alumina nanofluid (G=2500 kg/m2 s), (d) boiled in 0.01 vol % alumina nanofluid (G=2500 kg/m2 s), and (e) boiled in 0.1 vol % alumina nanofluid (G=2500 kg/m2 s)

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