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Thermophoresis in sols.

University of British Columbia

Experiments were conducted on the motion of micron-size, spherical latex particles in stagnant liquids due to applied temperature gradients. The phenomenon, called thermophoresis, has previously been reported for gases but not for liquids. Dilute suspensions of particles in water or n-hexane were trapped between two horizontal, parallel disks. The top disk was heated whereas the lower one was cooled, thus creating a temperature gradient in the liquid. The particle motion was measured by observing light reflected from the spheres with a low power microscope. The particle thermophoretic velocity, vth, was found to be a function of temperature gradient, ▽T, absolute temperature, TK, particle thermal conductivity, kp , fluid thermal conductivity, kf, viscosity, μ, and density, ρ: [ Formula omitted ] This equation was tested in the ranges 284 °K <_ TK <_ 343 °K and 7,000 °K m ̄¹ <_ ▽T <_ 30.J.00.0. °K m ̄¹ . No dependence, on particle diameter was noted. Thermophoresis in liquids is a weak effect and impractical for liquid-particle separation. It may, however, be important in engineering situations where large temperature gradients occur.

Text

2011-04-12

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http://hdl.handle.net/2429/33556

Chemical and Biological Engineering

University of British Columbia

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