Transient Rayleigh-Bénard-Marangoni Convection Enhanced Gas-Liquid Solute Transfer in Thin Layers

Abstract

A gas-liquid solute transfer process initiated in a closed vessel can exhibit Rayleigh-Bénard-Marangoni (RBM) convection enhanced mass transfer. For short exposure times experimental and theoretical results demonstrate that for deep liquid systems prior to solute penetration across the depth of the fluid, the stability thresholds of the system decreases with time. For thin liquid layers at longer exposure times the mass transfer enhancement under RBM convection can be affected in two ways: (1) solute penetration to the bottom liquid-solid boundary causing a departure from a penetration type concentration profile; (2) solute penetration to the top gas-solid boundary in the gas phase resulting in deviations of mass transfer Biot number from the penetration type of Biot number. These two effects have been investigated by imposing non-diffusing boundary conditions in the liquid phase as well as the gas phase. For short contact times, the critical thresholds of convection evaluated via a quasi-static stability analysis under non-diffusing boundary conditions are consistent with those under penetration type concentration profile. However, at longer exposure times when solute has completely penetrated the entire liquid depth, there can only be a limited period of time when convective instability is possible. Within this period there is a local maximum of convective intensity, thereby opening up the possibility of optimising gas-liquid mass transfer operations with respect to Rayleigh and Marangoni convection. Experimental results supporting these predictions are presented.

Parametric study of lotus-type pore shape in solid subject to Henry's laws at interfaces

“…It then gives velocity due to thermocapillary force where Marangoni number ∼7, Prandtl number ∼13 [ 14 ], and surface tension coefficient due to temperature ∼ N/m-K [ 16 ]. Similarly, viscous stress balanced by Marangoni force due to concentration, , and inertia force balanced by viscous stress gives velocity induced by Marangoni force due to concentration where Marangoni number ∼60, surface tension coefficient due to concentration [ 17 , 18 ], and Schmidt number ∼450 [ 14 ]. Eqs.…”