Effects of Thermodiffusion and Nanoparticles on Convective Instabilities in Binary Nanofluids

Author： Kim Jake Choi Chang Kang Yong Kim Moo

ISSN： 1091-7640

Source： Microscale Thermophysical Engineering, Vol.10, Iss.1, 2006-04, pp. : 29-39

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Abstract

In this article, the effects of thermodiffusion of nanoparticles and solute in binary nanofluids and nanoparticles on the convective instabilities of a binary nanofluid is theoretically investigated. Thermodiffusion implies that mass diffusion is induced by thermal gradient, which is the so-called Soret effect. In order to analyze the convective instabilities of a binary nanofluid, a new stability criterion is obtained based on the linear stability theory and new factors g and f are proposed. The results show that the Soret effect of solute makes the binary nanofluids unstable significantly and the convective motion in a binary nanofluid sets in easily as the ratio of Soret coefficient of nanofluid to that of binary basefluid δ 4 increases for δ 4 > − 1 . It is also found that with an increase of the volume fraction of nanoparticles, the nanofluid becomes stable, but at or near &psgr; bf = − 0.3 the state of nanofluid changes from stable to unstable. The results from the addition factor analysis show that an asymptotic point of &psgr; bf where the maximum value of g diverges infinitely exists in the range of − 1.2