Concentration dependences of heat conductivity coefficients of inert gases in narrow pores

Abstract

Calculation of the transfer of molecules in porous systems requires self-consistent expressions describing the kinetic transfer coefficients for various concentrations and temperatures. The concentration dependences of heat conductivity and self-diffusion coefficients for fluids with different densities, ranging from rarefied gases to liquids, were considered in terms of a unified model. For monoatomic gases (argon), the model takes into account two energy transfer channels, namely, the vacancy mechanism and energy transfer through collisions of molecules. The former channel is characteristic of rarefied gases, while the latter is noted for condensed phases. The energy parameters of the model were determined on the basis of data on the heat conductivity coefficient in the bulk phase. The heat conductivity coefficient follows a linear temperature dependence for low density; in the medium and large density regions, these dependences follow a more complex pattern that changes depending on temperature. The influence of the interaction of atoms with the pore walls on the concentration dependences of the heat conductivity coefficients was investigated for different total amounts of the adsorbate. These coefficients depend appreciably on the distance to the pore wall and on the direction of heat transfer.