Measurement of the thermophoretic force by electrodynamic levitation: Microspheres in air

doi:10.1016/0021-8502(95)00047-G

Journal of Aerosol Science

Volume 26, Issue 7, October 1995, Pages 1063-1083

https://doi.org/10.1016/0021-8502(95)00047-G Get rights and content

Abstract

The thermophoretic force on single microspheres has been measured over a wide range of Knudsen numbers and particle thermal conductivities for solid and liquid spheres in air. The microspheres were dioctyl phthalate (DOP) droplets, metallic nickel, polystyrene latex (PSL), and glass. This covers a thermal conductivity ratio (gas to particle) range of 2 × 10⁻⁴−0.17. In a companion paper, results are reported for monatomic (helium) and polyatomic gases (carbon dioxide and air) to examine the effects of gas properties. The measurements were accomplished by levitating the particle between heated and cooled plates mounted in a vacuum chamber. Light-scattering phase functions were used to determine the size of all materials except the nickel spheres, and for the highly absorbing metallic spheres the size was obtained by measuring the marginal stability limit of the particle. The apparatus developed for the research and the experimental techniques are discussed, and the experimental results in the Knudsen number range 0.05–20 are compared with previously proposed theories. For particle Knudsen numbers greater than about 10, the effects of the temperature jumps (thermal slip) at the heated and cooled plates become significant. The data in the transition regime overlap Loyalka's (1992, J. Aerosol Sci. 23, 291–300) solution of the linearized Boltzmann equation for hard-sphere molecules, and the data in the slip regime agree with Brock's (1962, J. Colloid Sci. 17, 768–780) theory. The effects of particle thermal conductivity are shown to be nearly negligible in the Knudsen regime, for the data for particles having greatly different thermal conductivities overlap.

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Citation Excerpt :
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Regular paperMeasurement of the thermophoretic force by electrodynamic levitation: Microspheres in air

Abstract

J. Aerosol Sci.

J. Colloid Sci.

J. Colloid Sci.

J. Aerosol Sci.

J. Colloid Sci.

J. Colloid Interface Sci.

J. Aerosol Sci.

J. Colloid Sci.

J. Aerosol Sci.

Part. Part. Systems Charact.

J. Fluid Mech.

Z. Naturforsch

Phys. Fluids

A model of collision processes in gases

Phys. Rev.

Absorption and Scattering of Light by Small Particles

Electrodynamic balance stability characteristics and application to the study of aerocolloidal particles

Langmuir

Light-scattering and aerodynamic size measurements for homogeneous and inhomogeneous microspheres

Langmuir

The double-ring electrodynamic balance for microparticle characterization

Rev. Sci. Instrum.

Thermal force on a sphere

J. them. Phys.

Dokl. Akad. Nauk SSSR (Phys. Chem.)

The theory of thermophoresis and diffusiophoresis of aerosol particles and their experimental testing

Thirteen-moment theory of the thermal force on a spherical particle

Phys. Fluids

Zur Theorie des Radiometers

Z. Physik

Über das Wärmeleitvermögen, die spezifische Wärme and die innere Reibung der Gase

Physik Z.

Regular paper
Measurement of the thermophoretic force by electrodynamic levitation: Microspheres in air