Cherevko K. Pressure, temperature and concentration influence on the stationary diffusion in the bounded systems

The thesis is devoted to the diffusion processes research in the membrane systems and in the sessile drop evaporation process under the diffusive regime.Theoretical models to describe the diffusion problems on the basis of the fundamental equations of irreversible processes thermodynamics but not the Fick’s law with the constant diffusion coefficient applicable in some few cases, are created in the thesis. The suggested approach allows to consider all the main peculiarities of the system on the stage of the problem analysis but not to introduce some artificial correctional terms into the final result which is necessary in the case of the Fick’s law based approach. The diffusion problem in the membrane system containing the two component solution is solved in the project within the linear approximation of irreversible processes thermodynamics. Osmotic phenomena that are to appear in the membrane system when the diffusion exists are described. Analytical results showing the diffusion flow dependence on the concentration difference between the two membrane borders are obtained for the different molecular models of the solution inside the membrane. The influence of the entropy and energy terms consideration in the solution thermodynamic potential on the diffusive flow and entropy production function is investigated. It is found that the reversible chemical reactions could be modeled as the intermolecular interaction but not from the chemical characteristics of the system. From the comparison with the experimental data it is shown that the suggested theoretical approach is able to give the description of the diffusion in the membrane systems. The equations to describe the diffusive flow dependence on the vapor concentration in the vicinity of the sessile evaporating droplet are obtained for the case of the diffusive regime. The near drop temperature distribution is obtained. It shows that in the case of the buffer gas, that could not be dissolved in the droplet, there should appear the temperature gradient during the diffusion process to maintain the stationary regime.