科研之友
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摘要
A new method, namely the 'common intersection method', is presented for predicting the liquid-vapor interfacial surface thickness. The method is based solely upon the characteristic of an intersection point on the isotherms of the density pro. le versus density. By using a physical analysis of the interfacial region, we obtain a new general integral expression for the liquid vapor interfacial thickness as a function of temperature. This integral expression is related to the width of the coexistence curve (defined as the difference between saturated liquid and vapor densities) and the mean density of a saturated liquid and its equilibrium vapor. However, knowledge of just the saturated liquid and vapor densities at a given temperature is sufficient for predicting reasonably well the temperature derivative of the interfacial width. In order to obtain the numerical values for the interfacial thickness as a function of temperature, its value at an arbitrary temperature, such as the triple point, must be known. The surface thickness at the triple point has been obtained from the inversion of the experimental data for surface tension by using the SAFT-DFT approach. The interfacial thickness at a given temperature is found to decrease with the chain length and may be scaled as a power law upon approaching the critical point with a critical exponent. Moreover, from the SAFT-DFT approach, the calculated surface thickness for n-alkanes is used to obtain the corresponding surface tension. Finally, our theoretical results are compared with experimental data. It is found that the present method predicts the surface thickness and its corresponding surface tension at various temperatures most satisfactorily.
- 出版日期2009-5
