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Research Papers: Micro/Nanoscale Heat Transfer

Nano-Alumina Accommodation Coefficient Measurement Using Time-Resolved Laser-Induced Incandescence

[+] Author and Article Information
David Allen

Department of Mechanical Engineering,
University of Illinois Urbana—Champaign,
Champaign, IL 61801
e-mail: djallen2@illinois.edu

Herman Krier, Nick Glumac

Department of Mechanical Engineering,
University of Illinois Urbana—Champaign,
Champaign, IL 61801

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received October 1, 2014; final manuscript received May 15, 2016; published online July 19, 2016. Assoc. Editor: Robert D. Tzou.

J. Heat Transfer 138(11), 112401 (Jul 19, 2016) (8 pages) Paper No: HT-14-1651; doi: 10.1115/1.4033642 History: Received October 01, 2014; Revised May 15, 2016

It has recently been suggested that the accommodation coefficient of nano-aluminum/alumina particles may be significantly smaller than previously assumed. This result has significant implications on the heat transfer and performance of the nanoparticles in combustion environments. Currently, the accommodation coefficient has been deduced only after assuming a combustion model for the nano-aluminum particle and changing the accommodation coefficient to fit experimental temperature data. Direct measurement is needed in order to decouple the accommodation coefficient from the assumed combustion mechanism. Time-resolved laser-induced incandescence (TiRe-LII) measurements were performed to measure the accommodation coefficient of nano-alumina particles in various gaseous environments. The accommodation coefficient was found to be 0.03, 0.07, and 0.15 in helium, nitrogen, and argon, respectively, at 300 K and 2 atm in each environment. These values represent upper limits for the accommodation coefficient as it is expected to decrease with increasing ambient temperature. The values are similar to what has been seen for other metallic nanoparticles and significantly smaller than values used in soot measurements. The results will allow for additional modeling of the accommodation coefficient extended to other environments and support previous measurements of high combustion temperatures during nano-aluminum combustion.

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References

Figures

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Fig. 1

Heat transfer rates for 50 nm alumina nanoparticles in N2 at 2 atm and 300 K assuming α = 0.05

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Fig. 2

Top view of the experimental setup. The experimental chamber is shown as if the top was not present to show particles.

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Fig. 3

Histogram of the nano-alumina particle size from the measured SEM analysis

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Fig. 4

SEM image of the nano-alumina particles using a Hitachi S4700 Microscope

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Fig. 5

Detected LII signal at 705 nm after single laser pulse with and without particle injection. Tests were run with the test chamber under vacuum pressure and pressurized to 2 atm with argon prior to injection.

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Fig. 6

Comparison of nanoparticle LII effective temperature at 1.06 atm and 2.08 atm nm in helium

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Fig. 7

Modeled transient temperature profile for various particle sizes with an accommodation coefficient of 0.1 and the resulting effective temperature modeled using particle size distribution shown in Fig. 3

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Fig. 8

Accommodation coefficient fit to the measured transient temperature profile for nano-alumina particles dispersed in nitrogen (N2) at 300 K and 2 atm. The two lines show upper and lower limits on the fit to an accommodation coefficient.

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Fig. 9

Accommodation coefficient fit to the measured transient temperature profile for nano-alumina particles dispersed in argon (Ar) at 300 K and 2 atm

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Fig. 10

Accommodation coefficient fit to the measured transient temperature profile for nano-alumina particles dispersed in helium (He) at 300 K and 2 atm

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Fig. 11

Accommodation coefficient dependence on ambient gas temperature. (Reproduced with permission from Goodman and Wachman [30]. Copyright 1976 by Academic Press.)

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