caa a22 4500 606198385 CHVBK 20210128100933.0 cr unu---uuuuu 210128e20150801xx s 000 0 eng 10.1007/s00348-015-2029-0 doi (NATIONALLICENCE)springer-10.1007/s00348-015-2029-0 Near-wall measurements of the bubble- and Lorentz-force-driven convection at gas-evolving electrodes [Elektronische Daten] [Dominik Baczyzmalski, Tom Weier, Christian Kähler, Christian Cierpka] Chemical energy storage systems, e.g., in the form of hydrogen or methanol, have a great potential for the establishment of volatile renewable energy sources due to the large energy density. The efficiency of hydrogen production through water electrolysis is, however, limited by gas bubbles evolving at the electrode's surface and can be enhanced by an accelerated bubble detachment. In order to characterize the complex multi-phase flow near the electrode, simultaneous measurements of the fluid velocities and the size and trajectories of hydrogen bubbles were performed in a water electrolyzer. The liquid phase velocity was measured by PIV/PTV, while shadowgraphy was used to determine the bubble trajectories. Special measurement and evaluation techniques had to be applied as the measurement uncertainty is strongly affected by the high void fraction close to the wall. In particular, the application of an advanced PTV scheme allowed for more precise fluid velocity measurements closer to electrode. Based on these data, stability characteristics of the near-wall flow were evaluated and compared to that of a wall jet. PTV was used as well to investigate the effect of Lorentz forces on the near-wall fluid velocities. The results show a significantly increased wall parallel liquid phase velocity with increasing Lorentz forces. It is presumed that this enhances the detachment of hydrogen bubbles from the electrode surface and, consequently, decreases the fractional bubble coverage and improves the efficiency. In addition, the effect of large rising bubbles with path oscillations on the near-wall flow was investigated. These bubbles can have a strong impact on the mass transfer near the electrode and thus affect the performance of the process. Springer-Verlag Berlin Heidelberg, 2015 Baczyzmalski Dominik Institute of Fluid Mechanics and Aerodynamics, Universität der Bundeswehr München, 85577, Neubiberg, Germany aut Weier Tom Helmholtz-Zentrum Dresden - Rossendorf, Institute of Fluid Dynamics, 01328, Dresden, Germany aut Kähler Christian Institute of Fluid Mechanics and Aerodynamics, Universität der Bundeswehr München, 85577, Neubiberg, Germany aut Cierpka Christian Institute of Fluid Mechanics and Aerodynamics, Universität der Bundeswehr München, 85577, Neubiberg, Germany aut Experiments in Fluids Springer Berlin Heidelberg 56/8(2015-08-01), 1-13 0723-4864 56:8<1 2015 56 348 https://doi.org/10.1007/s00348-015-2029-0 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00348-015-2029-0 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Baczyzmalski Dominik Institute of Fluid Mechanics and Aerodynamics, Universität der Bundeswehr München, 85577, Neubiberg, Germany aut NATIONALLICENCE 700 1- Weier Tom Helmholtz-Zentrum Dresden - Rossendorf, Institute of Fluid Dynamics, 01328, Dresden, Germany aut NATIONALLICENCE 700 1- Kähler Christian Institute of Fluid Mechanics and Aerodynamics, Universität der Bundeswehr München, 85577, Neubiberg, Germany aut NATIONALLICENCE 700 1- Cierpka Christian Institute of Fluid Mechanics and Aerodynamics, Universität der Bundeswehr München, 85577, Neubiberg, Germany aut NATIONALLICENCE 773 0- Experiments in Fluids Springer Berlin Heidelberg 56/8(2015-08-01), 1-13 0723-4864 56:8<1 2015 56 348