In this work, the effective thermal conductivity of porous materials is studied by a numerical method. A technique for designing an insulating material with specified geometric characteristics is proposed, which makes it possible to predict the thermal conductivity of porous insulation with sufficient accuracy. The design of foamed porous heat-insulating materials was based on the 3D Voronoi tessellation. The effective thermal conductivity of porous media was determined for twenty structures with different geometric characteristics. The thermophysical properties of the material corresponded to melamine. To verify the numerical solution, the effective thermal conductivity of the melamine sponge was determined experimentally. One regular structure and three irregular structures were compared with each other. The porosity of the insulating structures ranged from 0.722 to 0.987, the fiber diameter ranged from 0.0489 mm to 0.1259 mm. A theoretical solution is proposed for determining the effective thermal conductivity of regular structures. The technique proposed in the work can be used to design heat-insulating materials based on additive technologies, with specified heat-insulating and structural properties.

Keywords: effective thermal conductivity, porous structure, porous insulating material, 3D Voronoi tessellation

Porous media can be used as heat transfer intensifiers in the petrochemical, refrigeration, food, energy, and other industries. In this paper, heat transfer in a porous medium with a pulsating flow is studied numerically. The simulation was carried out in the AnsysFluent software product. The porous medium was represented as a two-dimensional channel with square tubes. The working medium was air and water. The heat transfer and hydraulic resistance of a porous medium in a pulsating flow are determined for different porosity and fiber diameter depending on the Reynolds number, Prandtl number, frequency and amplitude of pulsations. It is shown that with an increase in the intensity of pulsations, an increase in heat transfer occurs. Heat transfer intensification essentially depends on regime and geometrical parameters. Several empirical correlation are proposed for calculating heat transfer and the degree of heat transfer intensification for symmetric and asymmetric flow pulsations. The thermal-hydraulic efficiency is determined for the same Reynolds numbers and powers for pumping the heat carrier in a porous medium with symmetric and asymmetric flow pulsations.

Keywords: heat transfer, pulsation flow, porous media, mathematical modeling, thermal-hydraulic efficiency