Spatially resolved experimental analysis and modeling of mass transfer from rising gas bubbles under influence of swarm turbulence with superimposed chemical reaction

从分散的气相到液相的传质在化学工业和生物技术中是非常重要的，特别是当化学反应叠加时。然而，对于气液反应器的设计，只有经验关联式可用，这显示出有限的可转换性。这是因为它们是基于在特定条件下获得的综合测量数据。为了通过平衡方程更一般地描述反应体系和群体湍流条件下的传质性能，需要三维速度场和浓度场。在第一个项目阶段，对某些气流验证了由颗粒网格引起的群湍流。在此基础上，进一步发展了利用激光诱导荧光(LIF)测量、评价和重建气泡尾迹三维浓度场的方法。这现在允许在水动力蜂群条件下进行测量。对三维浓度尾迹的分析表明，在锯齿形气泡的情况下，舍伍德数Sh=470，完全符合预期。这表明发展的光学方法非常适合于验证数值传质计算。然而，当包括粒子图像测速仪(PIV)时，速度场可能会更精确。在接下来的项目阶段，将研究叠加反应对气泡尾迹内质量传递的影响，以及与反应相互作用的质量传递对其选择性的影响。在群体湍流下，计划对SPP反应体系Fe-NO的传质数据进行PIV/LIF测量，并对降低复杂性的流动条件(泰勒流)进行核磁共振(NMR)测量。为此，我们将修改SPP的主要实验泰勒流，使其适用于测量SPP反应体系Fe-NO和CuO2的核磁共振要求。此外，我们还希望描述层流Taylor流和湍流群体条件下单泡尾迹中传质现象的相似和区别。与SPP的化学、实验和数值工作组一起，这项分析旨在识别气-液反应器中传质的现象学模型。

The mass transfer from a dispersed gas phase into the liquid phase is of high importance in chemical industry and biotechnology, especially when a chemical reaction is superimposed. However, for a design of gas-liquid reactors, only empirical correlations are available, which show limited transferability. This is because they are based on integrally measured data obtained under specific conditions. For a more general description of the mass transfer performance for reactive systems and under swarm turbulence conditions via balance equations, three-dimensional velocity fields as well as concentration fields are required. In the first project phase swarm turbulences, induced by particle grids, were validated for certain gas flows. Based on this, the method of measuring, evaluating, and reconstructing three-dimensional concentration fields of bubble wakes were developed further by the laser induced fluorescence (LIF). This now allows measurements under hydrodynamic swarm conditions. The analysis of the three-dimensional concentration wake showed in case of a zigzagging gas bubble a Sherwood number of Sh = 470, which lies perfectly within the expectations. This shows that the developed optical method is very well suitable for validating numerical mass transfer calculations. When including Particle Image Velocimetry (PIV), however, even more precise velocity fields can be expected.In the project phase to come, the influence of superimposed reactions on mass transfer within bubble wakes is to be investigated as well as conversely the influence of mass transfer, interacting with reactions, on their selectivity. Under swarm turbulences, PIV/LIF measurements of mass transfer data for the SPP reaction system Fe-NO are scheduled as well as Nuclear Magnetic Resonance (NMR) measurements for flow conditions of reduced complexity (Taylor flow). For this purpose we will adapt the SPP's lead experiment Taylor flow on NMR requirements for measuring SPP reaction systems Fe-NO and Cu-O2.Furthermore we want to describe analogies and differences of mass transfer phenomena in wakes of single bubbles in laminar Taylor flow as well as under turbulent swarm conditions. Together with chemically, experimentally, and numerically working groups of the SPP, this analysis is intended to lead into the identification of a phenomenological modelling of mass transfer in gas-liquid reactors.