Wave dynamics in counter-current gas-liquid flows for distillation process applications
Résumé
Thin liquid films sheared by a strongly confined counter-current gas flow are common in various engineering applications, such as distillation and absorption for the
chemical process industry. These thin films are inherently unstable and the instability produces interfacial waves. These surface waves may strongly alter flow
structures within the liquid film as well as the surrounding gas, thus enhancing mass
and heat transfers between the two phases.
It is known that this enhancement is strongest in the vicinity of critical operating
conditions that may cause the system to flood. The aim of the current study is to
characterize this flooding regime which occurs when the liquid obstructs the channel
cross-section and strongly increases the pressure drop.
We employ Direct Numerical Simulation (DNS) by using an in-house two-phase
flow solver, where a compressible two-fluid model is implemented alongside a low-
Mach scheme. Linear stability of falling films with and without counter-current gas
flow is validated against the Orr-Sommerfeld theory. Non-linear wave profiles of
vertical falling films are thoroughly compared to experimental data. We also give
insights into the origin of the flooding regime in confined two-layer gas-liquid flows
by analyzing various flow conditions and channel widths.