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# Experimental study of the thermophoretic force and evaporation rates for single microparticles in the Knudsen regime

 dc.contributor.author Li, Wanguang, 1968- en_US dc.date.accessioned 2009-10-07T00:34:45Z dc.date.available 2009-10-07T00:34:45Z dc.date.issued 1995 en_US dc.identifier.other b36222999 en_US dc.identifier.other 35656289 en_US dc.identifier.other Thesis 44202 en_US dc.identifier.uri http://hdl.handle.net/1773/9929 dc.description Thesis (Ph. D.)--University of Washington, 1995 en_US dc.description.abstract Elastic and inelastic light scattering techniques were used to explore the processes of Knudsen evaporation, thermophoresis and gas/droplet reaction related to single microparticles. The reaction between single titanium ethoxide (TTE) droplets with water vapor was investigated. It was found that the fast surface reaction led to the formation of a coated microsphere consisting of a TiO$\sb2$ shell and an unreacted core.The thermophoretic force was measured over a wide range of Knudsen number (Kn = $\lambda$/a) for dioctyl phthalate (DOP) droplets and microspheres of polystyrene latex (PSL), glass and nickel in air, helium and carbon dioxide. The data in the transition regime were used to examine existing theories for the thermophoretic force. It was found that the numerical solutions of Loyalka (1992) and the theory of Brock (1962) are in good agreement with measurements in air and carbon dioxide. The results in helium were found to be somewhat higher than most theoretical solutions for monatomic gasses.The effects of the thermal properties of the gases and particles on the thermophoretic force were also investigated. It was found that the force strongly depends on the thermal conductivity of gas and weakly on the thermal conductivity of particle. The effects of surface charge on force were studied in this research for the first time. Negatively-charged particles receive a larger force than those positively-charged.Knudsen evaporation measurements were made for single dioctyl phthalate droplets in air in the temperature regime 263-302 K. The evaporation rates near room temperature (297.7K) were used to evaluate the theories of Loyalka et al. (1989), Fuchs and Sutugin (1970) and Sitarski and Nowakowski (1979). The agreement between the measurements and the solutions of Loyalka et al. (1989) and Fuchs and Sutugin (1970) was good for all values of Kn, but the solution of Sitarski and Nowakowski (1979) did not agree with the experiments at large Kn. en_US dc.format.extent xxi, 237 p. en_US dc.language.iso en_US en_US dc.rights.uri en_US dc.subject.other Theses--Chemical engineering en_US dc.title Experimental study of the thermophoretic force and evaporation rates for single microparticles in the Knudsen regime en_US dc.type Thesis en_US
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