Self diffusion of the nano-encapsulated phase change materials: A molecular dynamics study

Encapsulated phase change materials with good thermophysical and transport properties are of growing importance for heat transfer fluid in thermal energy storage systems. The presented work aims to understand the melting mechanism of nano-encapsulated phase change materials from molecular point of view. Two nanoencapsulated phase change materials models were fabricated by using SiO2 as shell material and n-octadecane as core material: one with free shell and another with constrained shell. The molecular dynamics simulation results showed that the self diffusion coefficient of n-octadecane decreased when the shell was constrained. The mobility of the n-octadecane, interaction of different n-octadecane molecules and the stretching strength of a single molecular chain were all restrained with the rigid shell. The nano-encapsulated phase change materials with free shell will increase the fluidity of core material and enhance the heat transfer of whole capsule. This study shows that the molecular dynamics simulation is an effective method for further understanding of encapsulated phase change materials.

► The melting behavior of EPCM was investigated by molecular dynamics method.
► Two EPCM models were fabricated by using SiO2 as shell material and n-octadecane as core material.
► The self diffusion coefficient of n-octadecane decreased when the shell was constrained.
► The mobility and interaction of n-octadecane molecules were all restrained with the rigid shell.
► The EPCM with free shell will enhance the heat transfer of whole capsule.