微通道内相界面形变强化的液-液弹状流传质过程研究

The study on mass-transfer intensification of liquid-liquid slug flow in microchannels has grown up gradually. Due to the limitation of the intensification methods reported in literatures, novel method need to be developed. Decreasing the internal and interfacial mass-transfer resistances is an effective approach to enhance the mass-transfer of liquid-liquid slug flow. Obvious interface deformation of slug droplet could reduce the internal and interfacial mass-transfer resistances by driving liquid mixing inside the droplet and inducing Marangoni effect on droplet interface, finally realizing the improvement of liquid-liquid mass-transfer rate. In this work, an expansion microchannel will be used to trigger the interface deformation of slug flow. The flow and mass-transfer of slug droplet in the expansion of microchannel will be studied by numerical simulation and experimental apparatuses, including high-speed camera and micro-particle imaging velocimetry. This work aims to reveal the reinforcement mechanism of interface deformation on mass-transfer and to develop the control method on mass transfer performance of slug flow with interface deformation. The research results are helpful to enrich the fluid-flow and interphase-mass-transfer theories on microscale and to provide theory and technique supports for the industrialization of micro-chemical technology.

微通道内液-液弹状流传质性能的强化是近年来逐步兴起的一个研究方向。目前文献报道的强化方法均有一定的局限性，因此有待开发新的强化方法。降低液滴内部和界面处的传质阻力是强化液-液弹状流传质过程的有效途径。弹状液滴相界面的剧烈形变可驱动液滴内部的均匀混合，诱发液滴界面的Marangoni效应，从而降低液滴内部和界面的传质阻力，实现液-液两相传质速率的提升。本课题拟利用含突扩结构微通道引发弹状液滴的相界面形变，借助高速摄像仪、微粒子成像测速仪等实验手段以及数值模拟计算，研究微通道突扩结构内弹状液滴的流动和传质过程，揭示弹状液滴形变对传质过程的强化机理，发展相界面形变强化的液-液弹状流传质性能的调控机制，丰富微尺度下流体流动与相间传质理论，为微化工技术的工业化应用提供理论和技术支持。

微通道内液-液两相流的传质强化和调控是近年来逐步兴起的一个研究方向，然而目前的研究尚有诸多不足。本项目借助高速显微摄像仪观察微通道内液液两相流动行为，基于此探究微通道内液液传质的强化与调控机制，而后将微通道反应器应用于生物柴油合成的液液两相反应。重要研究成果如下：（1）微通道内液滴行为可通过特征时间来进行描述；建立了描述液滴行为的特征时间模型，流速、长度和界面稳定剂浓度对时间影响明显；（2）纳米颗粒可有效强化微通道内液液两相传质，其中纳米颗粒的性质对传质性能影响明显；建立了考虑液滴流传质机理的体积传质系数模型，模型中引入了纳米颗粒浓度项；（3）在放大过程中，微反应器的混合器和系统存在不同的放大效应；分别对混合器和微反应器系统建立了考虑水力学直径的体积传质系数模型；（4）探究了液滴聚并行为对微反应器内生物柴油合成的影响；获得了生物柴油合成前120秒内详细的动力学数据，并建立了相应的动力学模型。此外，还将微反应器的流动化学思想拓展应用于香料和医药中间体的合成。本项目的研究成果深化了对微通道内液液两相流动和传质过程的认识，为微反应器的设计、放大和操作提供了重要的理论依据。