The modeling of meso-structure of fiber/particle composites and its influence on ETC under different inner pressure: A comprehensive study by RNMG-LBM

Fiber/Particle composites (FPCs) have garnered increasing attention as promising insulation materials in the energy field. Establishing a suitable composite model that can be used to investigate each component is essential. In this paper, the random non-contact multi-phase generation (RNMG) method was proposed for generating the meso-structure of FPCs. Furthermore, a comprehensive investigation was conducted using the Lattice Boltzmann Method (LBM) to quantify the influence mechanisms of various physical parameters, including inner pressure, aspect ratio, and particle diameter, as well as orientation angle, on the effective thermal conductivity (ETC) of FPCs. The validity of the RNMG-LBM was examined by comparing its results with experimental data. The simulation results demonstrated that reducing the particle diameters from 5 nm to 2 nm in FPCs leads to decreased pore sizes. Consequently, this reduces the sensitivity of FPCs to pressure fluctuations in the range of 10-1 Pa-105 Pa. Moreover, a physical parameter, called the orientation angle, was introduced to describe and explore the relationship between heat flux orientation and fiber orientation. The findings revealed that when the fiber was oriented perpendicular to the heat flux direction, it exhibited the lowest ETC among the orientation angles ranging from 0 degrees to 90 degrees. In addition, both the diameter and aspect ratio of fiber impacted its thermal properties. It's suggested controlling the aspect ratio below 20 and reducing fiber diameter as much as possible will significantly decrease the ETC of FPCs. The conclusions are valuable for optimizing the manufacturing process of FPCs and further improving their insulation capacity.