Experimental Investigation of Reactive Bubbly Flows - Influence of Boundary Layer Dynamics on Mass Transfer and Chemical Reactions

在化学过程工程中，为了进行高产率和高选择性的反应(如氧化或加氢)，通常必须将气态物质与连续的液体相混合。为此，最好使用混合良好的气泡流，其中气相分散在液体中。混合的时间尺度特别是由靠近相边界的边界层中的输送过程和气泡群湍流决定的。调整传输时间和化学反应的时间可以带来优化实际产率和选择性的相当大的潜力。因此，通过实验确定了泡状流中边界层和界面附近的输运过程，并在此优先方案的框架下对其进行了模拟。特别是考虑了形状动力学(摆动)、气液界面动量交换(群湍流)和气泡碰撞(弹跳)对气泡动态界面变形的影响。为了准确观测相边界附近的局域输运过程，采用了时间分辨扫描激光诱导荧光(TRS-LIF)和高分辨率粒子图像测速技术(PIV)。在第二个资助期，新开发的化学反应系统将用于分析、模拟和计算泡沫流中连续平行反应的产率和选择性。

In chemical process engineering often a gaseous substance has to be mixed with a continuous liquid phase in order to perform a reaction with high yield and selectivity (e.g. oxidation or hydrogenation). For this purpose, the use of well-mixed bubble flows is preferred, in which the gaseous phase is dispersed in the liquid phase. The timescales of mixing are especially determined by the transport processes in the boundary layer close to the phase boundary and by the bubble swarm-turbulence. Tuning the transport timescales and the timescales of the chemical reactions can lead to a considerable potential for optimization of the actual yield and selectivity. Thus transport processes in the boundary layer and close to the interphase in bubble flows with a following chemical reaction are experimentally determined and subsequently modeled in the framework of this priority program. Especially the influence of dynamic interface deformation of the bubbles, due to shape dynamics (wobbling), the momentum exchange at the gas-liquid interface (swarm turbulence) and bubble collisions (bouncing) are taken into account. To accurately observe the local transport processes near the phase boundary Time Resolved Scanning - Laser Induced Fluorescence (TRS-LIF) and high-resolution Particle Image Velocimetry (PIV) are applied. In the second funding period, the newly developed chemical reaction systems will be used to enable the analysis, modeling and calculation of the yield and selectivity of consecutive-parallel reactions in bubble flows.