Abstract
The object of this research is the process of the heat transfer through porous heat insulating materials. The problematic place of research is the absence of a generalized equation of thermal conductivity, which makes unable to predict the effective thermal conductivity of the material at the structure formation stage. The reason of it is lack of complex entrance independent factors of porous structure that influence on the effective thermal conductivity. For determining of this factors the computer simulation was used, it includes three dimensional samples and simulation of thermal process. After it, obtained computer modeling results were confirmed by laboratory experiment with using of the thermal conductivity meter ITP-MH4 of the company «SKB Stroyprybor». The regression equation of thermal conductivity for porous heat-insulating materials was found by the experimental design method, the analysis of it was showed that the most influence (80 % ) on coefficient of effective thermal conductivity have the pore diameter along to the heat flow and the total impact of the pore diameter perpendicular to the heat flow with temperature gradient. The thermal conductivity of initial material without pores λ mat in investigated range of 0,05 to 0,95 W/(m · K) isn't a significant factor. The temperature gradient doesn't linear and not directly proportional impact on the thermal conductivity of the final material. The generalized equation of thermal conductivity and the main factors, which influence on the coefficient of effective thermal conductivity, allow improving the thermal conductivity of new insulation materials and making it possible to develop a complete theory of thermophysical parameters control of porous heat insulating materials by changing the porous structure.
Highlights
The generalized equation of thermal conductivity is needed for assessing of the future effective thermal conductivity of porous material, but it doesn’t exist
Before this time the effective thermal conductivity could be solved by the difficult systems of equations, which taking into account radiation and convection inside the pores [7, 8]
Smaller air velocity in the spiral motion of convective lines means that for increasing the thermal resistance of insulation materials the spiral motion of convective lines in a closed spherical pore is better than the transverse motion with partial flow along the lower and upper spherical poles
Summary
The prospects of using of porous heat-insulating materials in the industry don’t in doubt [1,2,3]. Such materials are used as heat-insulating for houses, constructions, pipelines, furnaces, dryers and other industrial equipment. The generalized equation of thermal conductivity is needed for assessing of the future effective thermal conductivity of porous material, but it doesn’t exist. The generalized equation will allow controlling the thermal conductivity of porous material at the pores formation stage without numerous experiments. Finding of the generalized equation of thermal conductivity of porous heat-insulating materials is an actual scientific task, which is useful for the industry
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