高压下长链分子的自扩散系数研究

摘要

The self-diffusion coefficients are required in many engineering calculations involving mass transfer. In this work, an expression for the self-diffusion coefficient of a Lennard-Jones chain fluid is proposed by combining the self-diffusion coefficient equation for a Lennard-Jones fluid with the molecular dynamics simulation data for a hard-sphere chain fluid. The real long chain molecules such as alkanes and silicone oils are modeled as chains of freely tangent Lennard-Jones segments. The obtained equation has been applied to the calculations of the self-diffusion coefficients for the long chain alkanes and the liquid silicone oils in the pressure range from 0.1MPa to 600MPa. The average absolute deviations for these systems are within 10%. The calculated results are superior to that of the rough Lennard-Jones model. These results show that the Lennard-Jones chain model given in this work can be successfully used to calculate the self-diffusion coefficients for long chain molecules over wide ranges of temperature and pressure.%在Lennard-Jones流体自扩散系数方程的基础上，结合链状硬球流体自扩散系数的分子模拟数据，提出了链状Lennard-Jones流体的自扩散系数方程。将所提出的方程应用于计算长链烷烃和硅油在0.1~600MPa下的自扩散系数，其平均相对偏差在10%以内，计算结果优于自扩散系数的粗糙Lennard-Jones模型。