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

毛细管中的泰勒气泡流动常用于化学反应技术。由于复杂的流体动力学，对于复杂化学反应的传质和选择性，人们只了解了一部分。特别是在螺旋毛细管中，额外的迪安流使情况复杂化，但改善了径向传质。为此，建立了一个由内径为0.5 ~ 6mm的全氟乙烯-丙烯毛细管（与水或乙腈具有相同折射率的FEP）组成的实验体系，并进行了气液反应研究。研究了两步变色连续氧化和亚硫酸盐氧化平行变色的葡萄糖氧化酶反应。对于这些系统，扩散系数和动力学参数是在一个单独的测试设施中确定的。气泡形成和气泡流动可以在一个直的光学观察，垂直毛细管内径高达6毫米作为参考情况。在螺旋毛细管中，研究了混合、传质和复杂化学反应对泰勒-迪安流动的影响。Taylor-Dean流动谱可以完全表征，同时也可以在不同直径的毛细血管中进行不同反应及其典型时间尺度的光学检测。同时，用FeatFlow CFD软件对复杂的运输过程进行数值模拟。额外的90°偏转之间的个别线圈（螺旋流逆变器CFI）改善混合通过转移泰勒-迪恩漩涡的区域。无因次数以及分离指数或暴露水平被用于复杂反应混合过程的分析描述。复杂Taylor-Dean流的数值模拟需要对无化学反应和有化学反应时的流动和浓度场进行完整的三维模拟。数值网格的生成和界面处理对数值工具提出了很高的要求。调整平行反应和连续反应的动力学可以确定对目标分子的局部选择性，这在实验中导致溶液的颜色变化。作为优先计划的合作伙伴，进一步的化学反应在CFI装置中进行测试。在项目过程中，进一步的测量技术将使用x射线断层扫描、拉曼光谱和微距镜头高速相机。

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.