On thermodiffusion influence on the dopant distribution during the freezing of binary liquid column

Abstract

The relevance of the study is caused by the necessity of the extension of fundamental experimental and theoretical research in the field of macroscopic hydrodynamic phenomena in multicomponent liquid molecular mixtures. The results can be used in chemical technologies; they can change our point of view on the processes of deep waste water reclamation and safe utilization of geological resources. The main aim is to investigate the phenomenon of liquid molecular mixtures separation in thin channels by means of thermodiffusion over the self-cooling procedure; to compare different mechanisms of transfer - convection of short duration, diffusion and thermodiffusion - on the process of the components redistribution in the thin columns filled with a water-salt solution. The undertaken investigation has been executed to explain the origination of appreciable vertical stratification of different components of the mixture that gives significant variability of water salinity along the channel height. The methods used in the study: to fulfill the plan of our research the experimental and theoretical methods had been used that simulated physical processes under consideration: experimental data on concentration measurement which were taken during the freezing of the samples had been compared with the results of direct numerical modeling received by the finite difference method. The measurement of temperature fields was realized with the help of thermocouple technique. Numerical procedure was based on the full equations system of thermohaline convection. The results. The authors have shown that thermal convection, diffusion and strong positive thermodiffusion typical for the water-salt solutions can lead to the evident longitudinal division on components in the thin vertical channels filled with liquid mixtures over the selfcooling process and following freezing. The explanation of the strong longitudinal division in the liquid mixtures is based on the joint effect of two different physical mechanisms. There are thermodiffusion displacement of the admixture to the boundary layers of the channel and the large-scale axial convective flow. The similar phenomena could take place in artificial hydrological systems, natural geological processes and technological applications