基于分子动力学模拟的过冷态水气液界面特性研究

Study on the characteristics of supercooled water-gas-liquid interface based on molecular dynamics simulation

冷凝分离是重要的天然气脱水工艺,在对冷凝过程进行理论分析时,过冷态水的表面张力是其中非常重要的参数。采用分子动力学方法研究过冷态水的气液界面表面张力等特性。采用Lammps软件,模拟获得了不同温度平衡态下液相水的密度与表面张力,表面张力模拟值与实验数据符合良好,验证了模型的准确性。通过计算Y方向上的密度分布发现液相密度围绕着某个值进行振荡,并且在气液界面处幅度达到最大。以液相密度均值做比较,密度在280 K达到最大值,其他区域仍保持液相密度随温度的升高而减小的规律。研究了温度为220~370 K范围内的过冷态水的表面特性,结果表明过冷态水的气液界面的表面张力与常温区域的表面张力温度曲线斜率不同,并在过冷区域,即温度250 K附近出现第2个拐点(SIP)。

Condensation separation is a important method in natural gas dehydration technology,and the influence of surface tension parameters in the process of condensation is considerable. In this paper,molecular dynamics method is used to study the supercooled surface tension of water. Lammps software was used to simulate the density and surface tension of single component liquid phase at different temperatures,which was in good agreement with the experimental data of surface tension and verified the accuracy of the model. By calculating the density distribution in the Y direction,it is found that the liquid density oscillates around a certain value and reaches its maximum amplitude at the vapor-liquid interface. Compared with the mean liquid density,the density reaches the maximum value at 280 K,and the liquid density decreases with the increase of temperature in other regions. The simulation results show that the slope of the temperature curve of the surface tension at the gas-liquid interface of supercooled water is different from that of the normal temperature area,and there is a second inflection point(SIP)near the supercooled area at 250 K.