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arXiv 0907.1982cond-mat.soft
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非平衡平方梯度模型中两相混合物吉布斯表面的传递系数

Transfer coefficients for the Gibbs surface in a two-phase mixture in the non-equilibrium square gradient model

K. S. Glavatskiy, D. Bedeaux

摘要:

本文计算了混合物蒸发和冷凝的传递系数。我们使用连续的配置文件的各种热力学量通过接口,在我们以前的作品中使用平方梯度模型。此外,我们还引入了吉布斯曲面,得到了曲面的超熵产生。根据传统的非平衡热力学方法,我们引入了表面传递系数,我们能够从连续的解决方案确定。这些系数的知识对于许多涉及通过表面的传输的工业应用是重要的,例如蒸馏。在我们的方法中,在液相和气相中的局部折射率的值是根据实验值选择的。在界面区域,这些折射率存在小的峰。三个振幅控制这些峰值的大小。这些振幅的可能值被发现通过匹配的对角传递系数的值由动力学理论预测。利用这些振幅,我们发现交叉电阻率的值比动力学理论的值高1-2个数量级。动力学理论和分子动力学模拟的结果都支持在界面区域的局部折射率的小峰的存在。平方梯度法给出了一种独立的方法来确定表面的传递系数。结果表明,动力学理论低估了实际流体中的界面传递系数。

英文摘要:

In this paper we calculate the transfer coefficients for evaporation and condensation of mixtures. We use the continuous profiles of various thermodynamic quantities through the interface, obtained in our previous works using the square gradient model. Furthermore we introduce the Gibbs surface and obtain the excess entropy production for a surface. Following the traditional non-equilibrium thermodynamic approach we introduce the surface transfer coefficients which we are able to determine from the continuous solution. The knowledge of these coefficients is important for many industrial applications which involve transport through a surface, such as for instance distillation. In our approach the values of the local resistivities in the liquid and the vapor phases are chosen on the basis of experimental values. In the interfacial region there are small peaks in these resistivities. Three amplitudes control the magnitude of these peaks. Possible values of these amplitudes are found by matching the diagonal transfer coefficients to values predicted by kinetic theory. Using these amplitudes we find that the value of the cross resistivities is 1-2 orders of magnitude higher then the one from kinetic theory. The results of both kinetic theory and molecular dynamics simulations support the existence of small peaks in the local resistivities in the interfacial region. The square gradient approach gives an independent way to determine the transfer coefficients for surfaces. The results indicate that kinetic theory underestimates the interfacial transfer coefficients in real fluids.

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