Numerical investigation of the thermal conductivity of a composite heat-insulating material with microgranules

THE PURPOSE. To consider the problems that arise when creating a composite heatinsulating material, including a layer of microspherical granules. Numerical modeling of a composite material with different volume content of microspheres and different options for the formation of voids. Determination of the influence of the presence of zones not occupied by microgranules on the insulating properties of the composite material. Determination of the influence of the volume content of microspherical granules on the heat flux through the composite material.

METHODS. Numerical simulation was carried out by creating models of elementary cubic cells of a composite with a package of 27 microspheres in the ANSYS Fluent 19.2 software package. The evaluation of the insulating properties was carried out by measuring the thermal conductivity coefficient.

RESULTS. The article investigates the influence of the presence of zones not occupied by microspherical granules on the thermal insulation properties of a composite material. Models of elementary cubic cells with different volume content of microgranules are constructed. Models of elementary cells are built with various options for the formation of voids, such as the removal of a vertical or horizontal row of granules and the compaction of granules vertically or horizontally.

CONCLUSION. The removal of microgranules has a significant effect on the insulating properties of the composite. The lowest thermal conductivity coefficient was obtained for a simple cubic cell with a volume content of microgranules φ = 40%. The presence of voids in the material contributes to large heat losses, and in the case of a vertical through channel, the heat losses are greater than for a horizontal through channel. In the case of densification of spheres, heat losses in the zone not occupied by microgranules are compensated by a decrease in the heat flux in the area with densification of spheres. 

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