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甲烷水合物热导率分子动力学模拟及分析
杨德伟1,刘雨文2,修毓3,徐宏国2,苑昆鹏1,徐哲1
(1.中国石油大学储运与建筑工程学院, 山东青岛 266580;2.中国石化胜利油田分公司滨南采油厂,山东滨州 256600;3.山东省青岛市黄岛区城市建设局工程建设管理中心,山东青岛 266555)
摘要:
采用平衡态分子动力学方法模拟分子甲烷水合物导热性能,结合声子态密度分析甲烷分子和水分子间的能量耦合过程;探究范德华相互作用对热导率温度相关性的影响。结果表明:热导率随着甲烷分子和水分子间范德华相互作用的增强而增大。相互作用的增强令甲烷分子的振动峰值向高频区域移动,使得甲烷分子与水分子间的振动耦合作用增强,VDOS匹配程度增加,进而增大了甲烷水合物的热导率。高温下的温度相关性归因于弛豫时间声子的出现导致的非弹性散射,低温下主要受到光学声子模式和低频声子的约束影响。模拟的热导率的温度依赖性与实验结果吻合较好。
关键词:  甲烷水合物  分子动力学  声子  热导率
DOI:10.3969/j.issn.1673-5005.2016.04.019
分类号::TK 124
文献标识码:A
基金项目:国家自然科学基金项目 (U1262112)
Molecular dynamics simulation and analysis of thermal conductivity of methane hydrate
YANG Dewei1, LIU Yuwen2,XIU Yu3, XU Hongguo2,YUAN Kunpeng1,XU Zhe1
(1.College of Pipeline and Civil Engineering in China University of Petroleum,Qingdao 266580, China;2.Binnan Oil Production Plant of Shengli Oilfield Branch, SINOPEC, Binzhou 256600, China;3.Project Construction Management Center of City Construction Bureau of Huangdao District in Qingdao, Shandong Province, Qingdao 266555, China)
Abstract:
The heat conduction of methane hydrate was simulated using equilibrium molecular dynamics, and the thermal coupling between methane molecules and water lattices was studied by combining with the analysis of phonon density of states (VDOS). The influence of Van der Waals interaction strength on the temperature dependence of thermal conductivity was also investigated. The results show that the thermal conductivity increases proportionally with the enhancement of the Van der Waals interaction strength. With the increase of the interaction strength, the vibration peak of methane molecules shifts to a higher frequency region because of the stronger vibration coupling and the better matching of VDOS between methane molecules and water lattices, and then the thermal conductivity of methane hydrate is enhanced. The temperature dependence at high temperature may be attributed to inelastic scattering of the phonon caused by the appearance of phonons with the immediate relaxation time, while at low temperature it may be attributed to the confinement of the optic phonon modes and low frequency phonons. The calculated temperature dependence trend agrees well with the experimental results.
Key words:  methane hydrate  molecular dynamics  phonon  thermal conductivity
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