Abstract
This paper proposes a method for determining an effective value of the thermal conductivity for moist, highly porous rigid polymer foams. The model of moist foam based on an ordered structure with interpenetrating components was developed in accordance with the moisture distribution in the pore space. With small moisture content, isolated water inclusions are formed, and the pore space is considered as a binary system (vapor-gas mixture and water) with isolated inclusions. With an increase in moisture content, isolated water inclusions merge, forming a continuous layer, and pore space is considered as a binary system of interpenetrating components. The thermal conductivity of the vapor-gas mixture is represented as the sum of the thermal conductivity of the dry gas and the thermal conductivity of the vapor caused by the diffusion transfer of vapor in the pore space, taking into account the coefficient of vapor diffusion resistance. Using the proposed scheme of calculation, a computational experiment was performed to establish the influence of the vapor diffusion, moisture content, and average temperature of the foam on its thermal conductivity.
Highlights
Rigid polymer foams are widely used in construction and other industries as an effective thermal insulation
This paper proposes a method for determining an effective value of the thermal conductivity for moist highly porous polymer foams, which uses a nonadditive calculation scheme, including the impact of the vapor diffusion on heat transport, as well as consequent binary systems described with structural models with interpenetrating components and isolated inclusions
Thevalue pore surface is completely withconductivity is used to the calculate this case,2).the of the effective wetted thermal water, and the pore space can be represented as a binary system with interpenetrating components, of moist polymer foam is λ = 0.136 W/(m·K) and it is 1.71 times higher than the value of thermal for which Equation (5) is used to calculate thermal conductivity
Summary
Rigid polymer foams are widely used in construction and other industries as an effective thermal insulation. In [4], the effective thermal conductivity of a moist foam consists of the thermal conductivity caused by condensation of diffusing water vapor determined using the relation analogous to Fourier’s law for the heat flux and of the conductive thermal conductivity of a moist material determined according to Krischer’s equation This paper proposes a method for determining an effective value of the thermal conductivity for moist highly porous polymer foams, which uses a nonadditive calculation scheme, including the impact of the vapor diffusion on heat transport, as well as consequent binary systems (a porous substance consisting of a liquid and a vapor-gas mixture, and a solid polymer skeleton and a porous substance) described with structural models with interpenetrating components and isolated inclusions. The conditions for transition from one structural model to the other are determined
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