Changing Diffusion–Convection Modes in Ternary Mixtures with a Diluent Gas

Distinctions of the Emergence of Convective Flows at the “Diffusion–Convections” Boundary in Isothermal Ternary Gas Mixtures with Carbon Dioxide

“…At the final stage (Figure 3e-g), the convective formation begins to move in the gravity field relative to the diffusion interface. Then, but already under other initial condition, the process of structural formation begins again, but, already under other boundary conditions, i.e., in the system under study, the appearance of a drop convective mixing mode, which was recorded experimentally in various ternary mixtures [17,18,22], including those containing CO 2 [23], is possible. The calculation results presented in Figure 3 are in qualitative agreement with the experimental data for the 0.44 He (1) + 0.56 CO 2 (2) − N 2 (3) system given in [22], which shows that at pressures above 0.5 MPa, the conditions for the preferential transfer of carbon dioxide are realized in the system.…”

“…Experimental and computational-theoretical studies for isothermal multicomponent mixing have shown that in gas mixtures, when the condition of decreasing density with height is realized, convective flows that are not typical for diffusion mixing may occur [17][18][19][20][21]. The difference in the diffusion activity of the components causes a violation of the stability of the system and the appearance of isothermal concentration gravitational convection with a synergistic increase in the rate of mixing of the components.…”

“…Due to the different diffusion coefficients, spatial redistribution of dissolved substances in the gravity field occurs, followed by the release of the potential energy of the component with the highest molecular weight, which is converted into the energy of the moving medium. The technique [17][18][19][20][21] was recommended for determining the spectrum of thermophysical and geometric parameters, at which the transition from the diffusion state to the convective one occurs, assessing the role of diffusion mechanisms that form inversion layers, leading to the emergence of gravitational convection, which was presented in [22,23] for special cases of multicomponent mixing. However, the stability analysis formalism used in [22,23] does not allow one to monitor the emergence of structural formations and the subsequent evolution of convective flows.…”

Diffusion mechanisms of convective instability in liquid and gas mixtures

“…In a series of works [61][62][63][64][65][66][67][68], a complex of experimental studies was carried out in isothermal ternary gas mixtures H 2 + N 2 -CH 4 , He + Ar -N 2 , H 2 + Ar -N 2 , He + R12(2)-n-C 4 H 1 0, H 2 + N 2 O -N 2 , CH 4 + Ar-N 2 H 2 + CH 4 -He where it was shown that in these systems the "diffusion-convection" transition is possible at different pressures, temperatures, mixture composition, and inclination angles where mixing takes place. The intensity of convective flows caused by the instability of mechanical equilibrium depends on these parameters in a non-linear manner.…”