When fluids flow in microchannels, due to the relative low hydraulic diameter and low flow velocity, the flow is usually laminar flow, which hinders the effective mixing between two liquid-liquid phases. In this paper, the mixing efficiency at both droplet forming stage and droplet moving stage are investigated with the volume of fluid (VOF) method. The user defined scalar (UDS) is defined in the dispersed phase to analyze the mixing efficiency quantitatively. The droplet moves in the microchannel with the constant velocity, while serpentine microchannels are designed with different bend radius ranging. \( \overline{R} \) and ε_d are defined as the ratio of the bend radius to the width of the microchannel, and the ratio of the dispersed phase velocity to the droplet moving velocity, respectively. They are used for illustrating the effect of the bend radius and the dispersed phase fraction on the mixing efficiency in the droplet. Results indicate that the smaller dispersed phase fraction and smaller bend radius show the better mixing efficiency. However, the droplet production frequency changes in a parabolic trend with the variation of the dispersed phase fraction. The suitable dispersed phase fraction should be less than 0.5 in order to achieve a higher mixing efficiency and higher droplet formation frequency. In addition, the pressure drop in microchannel is increased with the decrease of the bend radius. The pressure drop observed in the micorchannel with square turn (\( \overline{R} \) = 0) and the microchannel with a bend radius of \( \overline{R} \) = 1 is nearly the same. This paper can be referred by someone dealing with the micromixer design and mass transfer in micro scale.

当流体在微通道中流动时，由于相对较低的水力直径和较低的流速，流动通常为层流，这阻碍了两个液-液相之间的有效混合。在本文中，利用流体体积（VOF）方法研究了液滴形成阶段和液滴移动阶段的混合效率。在分散相中定义用户定义的标量（UDS），以定量分析混合效率。液滴以恒定的速度在微通道中移动，而蛇形微通道则设计为具有不同的弯曲半径范围。\（\划线{R} \）和ε _d 分别定义为弯曲半径与微通道的宽度之比以及分散相速度与液滴移动速度之比。它们用于说明弯曲半径和分散相分数对液滴中混合效率的影响。结果表明，较小的分散相分数和较小的弯曲半径表明较好的混合效率。但是，液滴的产生频率随着分散相分数的变化而呈抛物线状变化。合适的分散相分数应小于0.5，以实现更高的混合效率和更高的液滴形成频率。另外，微通道中的压降随着弯曲半径的减小而增加。在微通道中观察到的压降呈方形转角（\（\ overline {R} \） = 0）和弯曲半径为\（\ overline {R} \） = 1的微通道几乎相同。从事微混合器设计和微观传质的人员可以参考本文。