不同结构二氧化碳水合物热物性的分子动力学模拟

Molecular Dynamics Simulation of Thermal Properties of Carbon Dioxide Hydrates with Different Structures

二氧化碳水合物在空调蓄冷、海水淡化、烟气捕集以及置换法开采天然气水合物等领域均有重要应用,热物性是气体水合物技术发展和应用的基础。以Ⅰ型二氧化碳水合物、Ⅱ型二氧化碳水合物、Ⅱ型二氧化碳和环戊烷二元水合物为对象,采用平衡分子动力学模拟手段,研究了20MPa、50-200K条件下二氧化碳水合物的热物性,包括密度、等温压缩系数、声学速度、比热、热导率、热扩散率和声子平均自由程,分析了影响水合物热导率的声子输运模式,发现环戊烷存在下,Ⅱ型二氧化碳水合物的声子输运模式与Ⅰ型二氧化碳水合物不同。模拟结果将为二氧化碳水合物在不同热力学添加剂下的应用提供基础数据和理论依据。

Carbon dioxide hydrate has important applications in cold storage of air-conditioning, seawater desalination, flue gas capture, and replacement of natural gas hydrate exploitation. Thermal properties are the basis for the development and application of gas hydrate technology. The thermal properties of carbon dioxide hydrate under the conditions of 20 MPa, 50-200 K are studied for structure Ⅰ carbon dioxide hydrate, structure Ⅱ carbon dioxide hydrate and structure Ⅱ carbon dioxide-cyclopentane binary hydrate using equilibrium molecular dynamics simulation methods. They are density, isothermal compressibility, acoustic velocity, specific heat, thermal conductivity, thermal diffusivity and mean free path of phonons. The phonon transport mode that affects the thermal conductivity of hydrates is analyzed, and it is found that in the presence of cyclopentane, the phonon transport mode of structure Ⅱ carbon dioxide hydrate is different from that of structure Ⅰ. The simulation results will provide basic data and theoretical basis for the application of carbon dioxide hydrate under different thermodynamic additives.