Concentration distribution and mass transfer process intensification of single droplet in swirl flow field

In the MIBK-acetic and acid-water system, the effects of swirl flow on the flow, concentration distribution, and mass transfer in a single droplet were investigated using high-speed camera, planar laser-induced fluorescence (PLIF), and particle image velocimetry (PIV) methods. The results show that swirl flow can cause forced convection in the droplet, accelerate solute diffusion to the phase interface, promote the uniform concentration distribution in the droplet, and improve the solute concentration at the phase interface. The oscillation of the swirl field makes the flow in the droplet switch between an “N”-shaped flow and a mirrored “N”-shaped flow, ensuring that the high concentration region is always on the same side as the thin boundary layer. Under the synergistic effect of high mass transfer driving force and low mass transfer resistance, the mass transfer of the droplet is significantly enhanced. Finally, the mass transfer coefficient k_L of the droplet is determined, which increases with the swirl intensity and droplet size.