Experimental and numerical investigation on interfacial mass transfer mechanism for Rayleigh convection in Hele-Shaw cell

To understand better the evolution of convective finger for Rayleigh convection confined in a gap with moderate width, we investigated the absorption of CO2 into water experimentally and numerically. A combined particle image velocimetry (PIV) and laser-induced fluorescence (LIF) method was used to measure simultaneously the instantaneous liquid velocity and solute concentration distributions in a Hele-Shaw cell. The process was then simulated using a 3D model with nonequilibrium interfacial boundary condition. An investigation in the gap direction showed that the intrinsic mechanism of interfacial mass transfer enhancement relies on a concentration boundary thickness decrease both inside and outside of convective fingers. On the basis of the simulation results, we present a vortex model for characterizing the interfacial mass transfer coefficient in the constant convective period. The model performs well using the penetration model by relating the gas-liquid contact time to the inverse of average vorticity value in liquid within 4 mm near the interface.