Experimental investigation of dynamic mass transfer during droplet formation using micro-LIF in a coaxial microchannel

Abstract The mass transfer of Rhodamine 6G from the droplet to the continuous phase in a coaxial micro-channel is studied using micro-LIF (Laser-Induced Fluorescence). The mass distribution inside droplet is measured and visualized. The experimental results affirm that there exists the internal circulation inside the droplet and it could enhance the convective mass transfer. The stagnant center of vortices is also observed. The extraction fraction could reach 40%∼80%. In order to establish the mass transfer model, different flow rates of the dispersed and continuous phase are adopted. The high continuous phase flow rate and low dispersed phase flow rate are both beneficial to enhance mass transfer by expediting the internal circulation. A modified mass transfer model is found to calculate the extraction fraction. A good agreement between the model and experiment in various conditions demonstrates that the mass transfer model in this work is reliable and feasible.