分子模拟方法预测流体热力学性质

Prediction of thermodynamic properties of fluid by molecular simulation method

流体的热力学性质数据对化工过程设计具有重要意义,除实验测定外,也可采用分子模拟方法计算。为了考查分子模拟方法预测流体热力学性质的准确性和可靠性,本文以环氧乙烷为例,基于所开发的分子力学力场,综合采用分子动力学和蒙特卡罗等多种分子模拟方法,预测了环氧乙烷在较大温度范围内的气液相平衡、第二维里系数、热容、粘度系数等多种热力学性质。结果表明,采用分子模拟方法所预测的热力学性质与实验值吻合良好,所计算的环氧乙烷的液体密度、气相第二维里系数、热容和粘度系数的平均偏差分别在1%、5%、5%和10%以内。由此可见,分子模拟方法可以成为获取流体热力学性质的另1种可靠手段。

The thermodynamic properties of fluid are key inputs in designing chemical processes and unit operations.These parameters may be obtained by molecular simulations in addition to experimental measurements.In order to investigate the accuracy and reliability to predict thermodynamic properties using molecular simulation method,with the optimized force field of ethylene oxide,we predicted the vapor-liquid equilibrium,second virial coefficient,heat capacity and viscosity of ethylene oxide in a wide range of temperatures using molecular dynamics and Monte Carlo simulation methods.Good agreements between the calculated and experimental data were obtained for the properties predicted and the deviations of the liquid density,second virial coefficient,heat capacity and viscosity are within 1%,5%,5%and 10%respectively.The results show that,the molecular simulation method can be a reliable approach to obtain thermodynamic properties of fluid.