Abstract
Abstract The characteristic features of the diffusion of helium and nitrous oxide diluted by propane to the same extent are experimentally studied at different pressures and concentrations of the diluent gas in the mixture. It is found that, at a certain pressure, convection currents appear in the system which intensify the partial mass transfer, which uncommon for diffusion. An increase in pressure intensifies the mixing of the components of the mixture. An increase in the concentration of the diluent gas in the mixture leads to the stabilization of convection modes. Solving diffusion equations shows that, in systems with a ballast gas, conditions for the nonlinear distribution of the concentrations of the components of the mixture along the length of the channel are implemented which can lead to the appearance of an extremum of the density of the mixture (i.e., inversion of the density gradient of the mixture), which induces the appearance of convection currents. The stability of the mechanical equilibrium of the ternary mixture in a vertical cylindrical channel under the action of gravity and at the predefined concentration gradients of the components is numerically studied. The boundary of the diffusion–convection kinetic transition is determined. The experimental and numerical results are compared in the coordinates of the Rayleigh number and pressure.