The effect of a Lorentz-force-driven rotating flow on the detachment of gas bubbles from the electrode surface. (17th August 2017)

• Record Type: Journal Article
• Authors: Weier, Tom; Baczyzmalski, Dominik; Massing, Julian; Landgraf, Steffen; Cierpka, Christian
• Is Part Of: International journal of hydrogen energy. Volume 42:Number 33(2017)
• Page Start: 20923
• Page End: 20933
• Publication Date: 2017-08-17
• Subjects: Electrolysis -- Magnetohydrodynamics; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2017.07.034
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: The enhanced bubble detachment in water electrolysis due to Lorentz-forces is discussed for the case of mainly parallel electric and magnetic fields. Experiments and numerical simulations were carried out to assess the velocity and pressure distribution around single rigid spheres mimicking electrolytic bubbles on a horizontal electrode in the presence of a vertical magnetic field. Astigmatism particle tracking velocimetry delivered the three-dimensional flow field and a finite volume method was used for the computations. Formerly it was assumed that the flow-induced pressure decrease at the bubble's top caused the earlier detachment under magnetic field action. However, the experimental and numerical results obtained here demonstrate that this pressure decrease is too weak as to effectively change the detachment process. Finally, an alternative explanation for the observed bubble behavior is suggested: it might result from the comparatively strong global flow generated by the additive effect of a group of bubbles. Highlights: measured Lorentz-force driven flow around a sphere, akin to a bubble on an electrode. pressure distribution above the bubble determined from experiments and simulations. Lorentz-force induced pressure difference too weak to alter bubble detachment. scaling analysis and numerics show findings valid for small bubbles as well. global rotational flow around a group of bubbles might explain earlier detachment.