A Study of the Stability of the Diffusion Regime in a CH₄–Ar–N₂ Ternary Gas Mixture at Elevated Pressures

Abstract

Diffusive mass transfer in multicomponent gas systems plays a key role in the design and optimization of processes in the chemical, oil and gas, and energy industries. This work presents an experimental and numerical investigation of isothermal mass transfer in the ternary CH₄–Ar–N₂ system at 295 K over a pressure range of 0.58–5.98 MPa. The system is characterized by similar diffusion coefficients of its components and relatively small density differences, which contribute to the stability of the diffusion regime. Experiments were conducted using a two-flask diffusion apparatus, with component concentration changes recorded as a function of time at different pressures. Numerical simulations were performed in ANSYS Fluent using the Species Transport model, Stefan–Maxwell diffusion formulation, and k–ω turbulence model. Good agreement between the experimental and numerical results was obtained over the entire pressure range, with discrepancies within the experimental uncertainty. At low pressures, the system exhibits a stable diffusion regime characterized by smooth, monotonic concentration kinetics. At elevated pressures, a transition to a diffusion–convection mass-transfer regime occurs, accompanied by a qualitative change in the mixing dynamics. The results demonstrate the capability of the proposed numerical approach to describe mass transfer in multicomponent gas systems under high-pressure conditions.