Analytical analysis of anisotropic thermophoresis of a charged spheroidal colloid in aqueous media for extremely thin EDL cases |
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| Authors: | Yi Zhou Changxing Zhu Kun Bian Mingyuan Yang Chun Yang |
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| Institution: | 1. Key Laboratory of High Performance Ship Technology, Ministry of Education, School of Energy and Power Engineering, Wuhan University of Technology, Wuhan, P. R. China;2. School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore |
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| Abstract: | Thermophoresis of charged spheroids has been widely applied in biology and medical science. In this work, we report an analysis of the anisotropic thermophoresis of diluted spheroidal colloids in aqueous media for extremely thin EDL cases. Under the boundary layer approximation, we formulate the thermophoretic velocity, the thermophoretic force, and the thermodiffusion coefficient of a randomly dispersed spheroid. The parametric studies show that under the aforementioned conditions, the thermophoresis is anisotropic and its thermodiffusion coefficient should be considered as a vector, D T. The thermodiffusion coefficient values and directions of D T are strongly related to the aspect ratio and the angle θ between the externally applied temperature gradient and the particle's axis of revolution: The increasing aspect ratio enlarges the thermodiffusion coefficient value DT of prolate (oblate) spheroids to a constant value when θ < 60° (θ > 45°), and it reduces DT of prolate (oblate) spheroids to a constant value when θ > 60° (θ < 45°). The thermodiffusion coefficient direction of both prolate and oblate spheroids deviates slightly from ??T∞ for a small aspect ratio, and such deviation becomes serious for a large aspect ratio. |
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| Keywords: | Anisotropic thermophoresis Randomly dispersed spheroid Thermodiffusion coefficient Thin EDL cases |
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