Abstract: Fick’s law of diffusion is only valid for the description of an ideal binary diffusion without external force, while Maxwell-Stefan (MS) equation can be applied to multicomponent mass transfer under the influence of external field. The physical meaning of MS equation was clearly explained, and the generalized expression of MS equation was rewritten to a form which is simpler and easier for use. The expressions of the external forces which could be used in the equation were given. Fick’s law of diffusion is the special form of MS equation to the mass diffusion in ideal binary fluid without external force. The application results of MS equation to the centrifugal separation and the electrolyte diffusion are consistent with that of traditional descriptions, but more comprehensive. In this paper, application of MS equation to electric conduction leading to Ohm’s law was carried out, which provides a new method to get diffusivity through the measurement of conductivity. The characteristic of mass transfer in spherical particles enhanced by electric field was investigated with MS equation, and this investigation showed that MS equation could effectively describe the mass transfer enhanced by external field. MS equation provides an effective theoretical method to study the mass transfer enhanced by external fields.

Key words: Maxwell-Stefan equation, multicomponent mass transfer, mass transfer enhanced by external field

摘要： Fick扩散定律只能用于没有外场作用下的二组分扩散过程，Maxwell-Stefan（MS）方程适用于外场作用下多组分系统中的质量传递过程。阐述了MS方程的物理意义，并由此将外场作用下普遍化MS方程的表达式改写为清晰且易于使用的形式。给出了在MS方程中常用的外场作用力的数学形式。Fick扩散定律是MS方程在没有外场作用下对二元理想流体扩散的应用；MS方程对离心分离和电解质扩散等过程的描述比传统的描述方法更全面。利用MS方程导出了欧姆定律，利用该结论可以通过测量电导率计算带电粒子的扩散系数。利用MS方程研究了电场作用下球形颗粒中的扩散过程，结果表明，该方程可以对电场强化质量传递过程给出有效描述。MS方程为外场作用下的质量传递过程提供了一种有效的理论研究方法。

关键词: Maxwell-Stefan方程, 多组分质量传递, 外场强化传质