客体分子数对甲烷水合物导热性能影响的分子动力学模拟

摘要

采用EMD方法Green-Kubo理论计算263.15 K晶穴占有率0～100％ sI甲烷水合物的热导率,研究客体分子数对甲烷水合物导热性能的影响.模拟结果显示,甲烷水合物的低导热性能由主体分子构建的笼形结构决定.而在相同温压条件下,随着客体分子甲烷进入晶胞数目增多,晶穴占有率增大后,密度增大,同时客体分子对声子的散射也增强,二者均导致导热性能增强.%Thermal conductivity of methane hydrate is an important physical parameter in processes of methane hydrate exploration, mining, gas hydrate storage and transportation as well as other applications. In this paper, equilibrium molecular dynamics (EMD) simulation and the Green-Kubo method are used for the systems with 0-100% occupancy of sI methane hydrate to evaluate the influence of guest molecule number on the thermal performance of methane hydrate. The EMD simulation for the thermodynamics of equilibrium state of si methane hydrate is performed via the Green-Kubo approach for the thermal conductivity of methane hydrates. The DL-POLY molecular dynamics simulation package is employed. TIP4P/Ice water model is used for water-water interactions and the Lennard-Jones potential for methane-methane and methane-water interactions. The Lorentz-Berthelot combination rule is used to determine the parameters of Lennard-Jones potentials between water and methane molecules. The equations of motion are integrated using the Verlet algorithm and the Ewald method is used to handle long-range electrostatic interactions. Results indicate that the poor thermal conduction of methane hydrate is resultedfrom the framework of cage. The thermal conduction of methane hydrate is improved when the framework of cage has slightly higher thermal conductivity with more guest molecules enclosed in the cage> since higher cage occupancy ratio by guest molecules increases the density and their scattering.