Numerical modelling of multi-component mass transfer regimes in four-component gas systems

Abstract

For argon and carbon dioxide, which are part of the tetra-component gas mixture He + Ar + CO₂ – N₂ and are the heaviest compared to other components, graphs of the behavior of the concentration of these components at different points of the diffusion channel and time intervals are presented. To simulate convective flows in the four-component mixture under consideration, the Flow Simulation computer package included in the SolidWorks engineering design system was used. The equations are solved by the finite volume method using the standard k – ε turbulence model and with initial and boundary conditions. Indicated, that obtained distributions change nonlinearly both in time and along the length of the diffusion channel. In this case, there is a change in the diffusion process to a convective one, which is due to the nonlinearity in the distribution of the components concentration, which is connected with the imbalance of mechanical equilibrium. It was found that the most significant change in the behavior of the concentrations of heavy-weight components occurs within 120 s. This time interval coincides with the appearance of two contrasting areas on the graphs, namely, the formation of a developed convective flow. An enhancement in the time of the numerical experiment showed that the concentration of the component with the maximal molar mass remains practically unchanged. This behavior of the concentration of heavy-weight components is characteristic of the effect when the mixture is enriched in the heavy-weight component. An analysis of the streamlines on the plots of concentration distributions showed that vortices of various scales interacting with each other and leading to a pulsating mixing regime are formed along the length of the channel. It has been established that the presence of large-scale vortices determines the preferential migration of the components with the maximal molar mass.