Complex Gas-Liquid Reactions with Mass Transfer in Coiled Flow Inverters

在化学反应技术中，毛细管内的泰勒泡状流是经常使用的。由于复杂的流体动力学，人们对复杂化学反应的传质和选择性了解很少。特别是在螺旋毛细管中，附加的迪恩流使情况变得复杂，但改善了径向传质。为此，建立了由内径为0.5~6 mm的全氟乙丙毛细管(折射率与水或乙腈相同的FEP)组成的实验系统，并进行了气液反应研究。研究了两步变色反应和平行亚硫酸盐氧化变色葡萄糖氧化酶的氧化反应。对于这些体系，扩散系数和动力学参数是在单独的测试设备中确定的。以内径达6 mm的直立毛细管为参照物，用光学方法观察气泡的形成和气泡流动。研究了螺旋毛细管中的Taylor-Dean流动，包括混合、传质和复杂的化学反应。Taylor-Dean流型可以完全描述，而不同反应的典型时间尺度也可以在不同直径的毛细管中进行光学检查。同时，利用FeatFlow CFD软件对复杂的输运过程进行了数值模拟。单个线圈之间的额外90°偏转(卷流逆变器CFI)通过移动Taylor-Dean旋涡的区域来改善混合。用无量纲数和分离指数或暴露水平来分析描述复杂反应的混合过程。要对复杂的Taylor-Dean流动进行数值模拟，需要对无化学反应和有化学反应的流动和浓度场进行完整的三维模拟。界面的数值网格生成和处理对数值工具提出了很高的要求。对平行和连续反应动力学的调整允许确定对目标分子的局部选择性，这在实验中会导致溶液的颜色变化。作为优先计划的联合合作伙伴，进一步的化学反应将在CFI设置中进行测试。在该项目的过程中，将使用X射线层析成像、拉曼光谱和带微距镜头的高速相机来实现进一步的测量技术。

Taylor bubble flow in capillaries is often used in chemical reaction technology. Due to complex fluid dynamics, it is only partly understood regarding mass transfer and selectivity of complex chemical reactions. Particularly in helical capillaries, the additional Dean flow complicates the situation, but improves radial mass transfer. For this purpose, an experimental system consisting of perfluorinated ethylene-propylene capillaries (FEP with the same refractive index as water or acetonitrile) with an internal diameter of 0.5 to 6 mm is built and investigated with gas-liquid reactions. The oxidation of leuco indigocarmine with a two-step color change as a consecutive reaction and glucose oxidase with color change parallel to sulfite oxidation are investigated. For these systems the diffusion coefficients and kinetic parameters are determined in a separate test facility. Bubble formation and bubble flow can be optically observed in a straight, vertical capillary with an internal diameter up to 6 mm as a reference case. In the helical capillary, Taylor-Dean flow is investigated with mixing, mass transfer, and complex chemical reactions. The Taylor-Dean flow profile can be entirely characterized, while different reactions with their typical time scales can also be optically examined in the capillaries with different diameters. In parallel, complex transport processes are numerically simulated with FeatFlow CFD Software. Additional 90° deflections between individual coils (Coiled Flow Inverter CFI) improve mixing by shifting the regions of the Taylor-Dean vortices. Dimensionless numbers as well as segregation index or exposure level are used for the analytical description of the mixing process of complex reactions. The numerical simulation of the complex Taylor-Dean flow requires a complete 3D simulation of the flow and the concentration field without and with chemical reactions. The numerical grid generation and treatment of the interface imposes high demands on the numerical tools. The adjustment of the kinetics of parallel and consecutive reactions allows for determining the local selectivity to the target molecule, which in the experiment causes a color change of the solution. As associated partner in the priority program further chemical reactions are tested in the CFI setup. In the course of the project further measurement techniques will be available with X-ray tomography, Raman-spectroscopy, and high-speed camera with macro lens.