The film thickness is a vital parameter for the falling film micro-reactor (FFMR) as a characteristic value representing both the surface to volume ratio and the distance of mass and heat transfer. In this paper, a method and procedure using a stereo digital microscopy to study the flow pattern and liquid film thickness in the FFMR were developed. The hydrodynamic behaviors of three liquids (deionized water, ethanol and isopropanol) have been investigated in a customer designed FFMR. Studies suggest that the film thickness increases with increasing flowrate and viscosity. The viscous force plays a dominant role in the falling film process. The falling film behaviors were also analyzed by computational fluid dynamics (CFD) simulation. A new correlation for the film thickness prediction has been proposed, and its predictions are consistent with the experimental data from this work and public literatures with an accuracy of 7% and 20%, respectively. As a result, stereo digital microscopy has been proved to be an effective device for investigating the hydrodynamic behaviors in FFMR, and the proposed model can accurately predict the film thickness in falling film micro-system within a wide flow regime.

膜厚是降膜微反应器（FFMR）的重要参数，它是代表表面积与体积之比以及质量与热传递距离的特征值。在本文中，开发了一种使用立体数字显微镜研究FFMR中的流型和液膜厚度的方法和程序。在客户设计的FFMR中研究了三种液体（去离子水，乙醇和异丙醇）的流体动力学行为。研究表明，膜厚随流速和粘度的增加而增加。粘性力在降膜过程中起主要作用。还通过计算流体动力学（CFD）模拟分析了降膜行为。已经提出了用于膜厚度预测的新的相关性，其预测值与这项工作和公开文献中的实验数据一致，准确度分别为7％和20％。结果，立体数字显微镜已被证明是研究FFMR中流体力学行为的有效装置，并且所提出的模型可以在宽流量范围内准确地预测降膜微系统中的膜厚。