Electrogenerated bubbles induced convection in narrow vertical cells: PIV measurements and Euler-Lagrange CFD simulation

This paper addresses the two-phase flow hydrodynamics in Vertical Plane Electrode Reactors with Gas Electrogeneration, VPERGEs: (1) An experimental investigation of the hydrodynamics in a laboratory-scale VPERGE reactor - for three different current densities - was carried out. Flow visualisation with a high-speed camera, using the gas bubbles as tracers allowed particular flow features to be evidenced. Moreover, thanks to suitable pre- and post- processing tools, the gas velocity fields have been obtained using a PIV algorithm. Measurement errors related to the use of this technique are discussed. The calculated velocity fields provided an overall picture of the flow behaviour, and constitute a data base that can serve for the validation of future numerical results. (2) The two-phase flow was simulated using the two-way momentum coupling Euler-Lagrange CFD approach. Bubbles were considered to be injected slightly away from the electrodes, and not directly at the electrodes surfaces. The shift in the injection position was taken as the average radius of the bubbles. This slight offset of the bubble injection location allowed to obtain a numerical solution that is quasi-independent of the mesh size. CFD results were in good agreement with experimental data, and reproduced key flow features such as spreading of the bubble curtains and bubbles dispersion toward the centre of the reactor.