Mass transfer of rising gas bubbles in reacting liquids

本项目的目的是研究气泡间相互作用对反应性气泡流动中传质的影响。在此之前，实验工作主要集中在确定流体动力学、传质和化学反应之间的相互作用。由于在实际应用中多个气泡相互作用，这里将研究不同类型气泡形成中的某些气泡。在第一个资助期开发的实验系统将进一步用于补充单泡实验。这些实验为评价相互作用气泡形成的结果提供了必要的基本信息。互补性的单气泡研究的目的是确定传质系数。这是根据气泡与(反应)液相接触过程中气泡尺寸的变化来确定的。实验在两台仪器上进行，这两台仪器是在第一个资助期内进一步开发的。装置由气泡上升通道和逆流流动池组成，变化的参数有：化学体系(WG Klüfers/Schindler/Herres-Pawlis)、气泡大小、气泡与液体接触的时间、压力、温度、液相中的产物浓度。结果将用调整后的或新的Sherwood关联式进行数学建模，并合理考虑所有影响参数。这些关联式将用于比较气泡附近具有更复杂速度场和浓度场的系统。这些字段将在受控条件下创建。将测试几种方法。将调查气泡链、气泡阵列和气泡群，这些气泡将随着一个气泡的跟随而停止。作为比较，优先计划中的其他小组在第一个资助期开发和研究的湍流促进器也将进行测试(WG Kähler/Schlüter/Thoeming)。除了对在第一个资助期内开发的化学体系进行调查外，还将调查具有平行和/或连续化学反应的新的和进一步开发的体系。在某些情况下，这需要实验中的新方法能够进行准确的量化。全自动实验仪器将配备新的静止和移动光谱测量技术(WG Rinke/Simon)。这种方法有很大的潜力，因为开发的化学反应具有竞争性的化学反应，导致不同的变色。选择的方法是在气泡上升过程中用光学测量技术跟踪气泡，提供在不同控制条件下的上升路径、气泡形状和收缩行为的结果。这些信息对数字工作组来说很有意义，因为它很容易用于验证(工作组Bothe/Rzehak/Sommerfeld)。

The idea of this project is the investigation of the influence of the interaction of bubbles on the mass transfer in reactive bubbly flows. Previously, the experimental work was focused on the determination of the interaction between fluid dynamics, mass transfer and chemical reaction. As in practical applications multiple bubbles interact, here certain bubbles in different types of bubble formations will be investigated. The experimental systems developed in the first funding period will further be used for complementary single bubble experiments. These experiments provide the necessary basic information to evaluate the results of interacting bubble formations.The aim of the complementary single bubble investigations is the determination of mass transfer coefficients. These are determined based on the change of the bubble size during the bubble's contact with the (reacting) liquid phase. The experiments are performed in two apparatuses which were further developed in the first funding period. The apparatuses are a bubble ascent channel and a counter current flow cell.Varied parameters are: The chemical system (WG Klüfers/Schindler/Herres-Pawlis), bubble size, contact time between bubble and liquid, pressure, temperature, educt concentration in the liquid phase.The results will be mathematically modeled with adjusted or new Sherwood correlations while reasonably incorporating all influencing parameters. These correlations will be used to compare systems with more complex velocity and concentration fields in the vicinity of the bubble. These fields will be created under controlled conditions. Several approaches will be tested. A chain of bubbles, an array of bubbles and a bubble swarm which will be stopped with a single bubble following will be investigated. For comparison, turbulence promoters which were developed and investigated in the first funding period by other groups in the priority program will be tested as well (WG Kähler/Schlüter/Thoeming). Besides the investigation of the chemical systems de-veloped in the first funding period, the new and further developed systems with parallel and/or consecutive chemical reactions will be investigated. In some cases, this requires new ap-proaches in the experiments to be able do an accurate quantification. The fully automated ex-perimental apparatuses will be equipped with new stationary and moving spectral measurement techniques (WG Rinke/Simon). This approach has great potential as chemical reactions are developed which have competing chemical reactions resulting in differing discolorations.The chosen approach of following the bubble during its ascent with an optical measurement technique provides results of the rising path, bubble shape and shrinkage behavior under diverse controlled conditions. This information is of high interest for numerically working groups as it can easily be used for validation (WG Bothe/Rzehak/Sommerfeld).