Effect of Graphite Layers on the Conformation and Thermal Conductivity of n-octadecane:A Molecular Dynamics Study

• 作者: ZHANG Tiantian XU Bo CHEN Zhenqian
• 来源期刊: 热科学学报（英文版）
• 年，卷（期）: 2021,（5）
• 所属期刊栏目: Special Column:Advancement in Solar Energy Technologies
• 页码范围: 1789-1802
• 页数: 14页
• 语种: 英文

摘要

To understand the thermal conductivity improvement of the paraffin and graphite composite PCMs in micro-scale,the conformation characteristics of molecules with rising temperature was studied by molecular dynamics (MD) simulation.And then the structure and dynamics characteristics of the paraffin PCM,including the structural evolution,the self-diffusion coefficient,phase change properties and thermal conductivity,were analyzed.The results indicate that the distribution of the n-octadecane molecules is more regular in the region near the graphite layers,although the temperature is higher than the phase transition point,which means that the graphite layer has a significant absorption influence on the conformation of alkane molecules.Then,the self-diffusion coefficient of n-octadecane molecules increases with the increasing of temperature,which shows great agreement with the literature.Meanwhile,the self-diffusion coefficient of n-octadecane molecules staying far away from the graphite layers is larger than that of the molecules in the region near the graphite layer.In addition,the radial distribution function (RDF) was used to analyze the molecular interaction of the system at different temperatures.The sudden increase of R (ratio of the first peak value to the first valley value of the RDF)within the temperature range from 293 K to 313 K corresponds to the phase transition point,indicating that the solid-liquid phase transition occurs at the temperature range.Besides,the results indicate that the thermal conductivity of amorphous n-octadecane is about 2.5 times lower than that of the crystal n-octadecane with perfect structure.This investigation provides theoretical guidance for the study of the micro-mechanism of n-octadecane doped with graphite composite phase change materials.