Simulation of the enhancement of Dean flow on the liquid–liquid extraction in membrane contactors

Abstract

Dean vortices generated through the curved paths have been demonstrated to be beneficial to enhance gas–liquid mass transfer in membrane contactors. However, the effect of Dean vortices in liquid–liquid membrane extraction was seldom studied. This work implemented a numerical model describing the liquid–liquid extraction process in curved membrane contactors with the software of COMSOL. The liquid–liquid extraction experiments were first performed verifying the applicability of the simulation. Firstly, the discussion about the role of membrane resistance revealed the fact that enhancement provided by Dean flows would be more pronounced for systems with lower membrane resistance. A parametric study was then conducted including geometric parameters and physical properties of the fluid, which indicated smaller pitch, smaller curvature diameter, and less viscous fluid led to a better enhancement. The intensification factor was in the range of 1 ∼ 1.8, corresponding to the Dean number range of 5 ∼ 30. Considering the energy consumption, the values of modified intensification factors were lower than 1 only when the Dean numbers were smaller than 8. Finally, the performance of four curved geometries: helically-wound, 90-degree bend, meander-shaped, knotted were compared. The presented model yielded new insights into the liquid–liquid exaction enhancement in the curved membrane contactors.