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Effects of gas species on pressure dependence of thermophoretic velocity

Razali, Mohd Azahari and Mori, Masayuki and Suzuki, Masataro and Masuda, Wataru (2012) Effects of gas species on pressure dependence of thermophoretic velocity. Journal of Aerosol Science, 54. ISSN 0021-8502

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Abstract

Microgravity experiments are conducted to measure the thermophoretic velocity, and effects of gas species are investigated. Particles adopted are PMMA spheres of 2.91 μm in mean diameter, and atmospheric gases chosen are pure gases of argon, nitrogen, and carbon dioxide. The temperature gradient is set at 10 K/mm, and the pressure is set at several conditions in the range from 20 kPa to 100 kPa. Terminal velocities of particles suspended in a gas are individually measured during 0.25 s of the microgravity condition, which is achieved by a free-fall. The accuracy of the measurement is attained by accumulating data from repeated trials. Obtained experimental results are compared with theoretical predictions; a notable discrepancy is found for carbon dioxide, while the results for other two gases are consistent with predictions. Some attempts are made to fix the discrepancy: first by modifying constants and second by modifying two empirical coefficients in the theory.

Item Type: Article
Uncontrolled Keywords: microgravity experiment; thermophoretic velocity; tangential momentum accommodation coefficient; thermal accommodation coefficient
Subjects: T Technology > TA Engineering (General). Civil engineering (General) > TA349-359 Mechanics of engineering. Applied mechanics
Divisions: Faculty of Mechanical and Manufacturing Engineering > Department of Plant and Automotive Engineering
Depositing User: Normajihan Abd. Rahman
Date Deposited: 27 May 2015 07:30
Last Modified: 27 May 2015 07:30
URI: http://eprints.uthm.edu.my/id/eprint/6931
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