Modeling of electrochemically generated bubbly flow under buoyancy-driven and forced convection

Abstract

a b s t r a c tThis work is devoted to the modeling of two phase flows arising in typical electrolysis devices. A numerical mixture model is used in order to resolve the two dimensional bubble plumes evolving along the electrodes. Plumes thickness sensitivity is studied for various parameters, such as bubble diameter, electrolyte viscosity, electrochemical cell geometry and current density. Using thermal buoyancy driven flow analogy, a dimensionless Rayleigh-like number Ra f ;e is defined to predict the behavior of the wallbounded gas convection between two vertical facing electrodes. Different bubbles dispersion mechanisms are observed depending on two-phase flow dynamics and physical properties of the mixture. The effect of forced convection in the channel is also investigated. A scaling law for plume thickness evolution for a large range of Prandtl-equivalent number values is proposed. These results show that the bubble plume can be efficiently controlled by an imposed electrolyte velocity.

Review—Physicochemical Hydrodynamics of Gas Bubbles in Two Phase Electrochemical Systems

“…Increasing the bulk velocity improves the mass transfer by instigating turbulence and avoiding the recombination of the electrochemically produced gaseous species. 88, 89 Understanding the bubble-electrolyte interphase flow is essential to optimizing the mass transfer and bubbles detachment efficiency.…”

Near-wall measurements of the bubble- and Lorentz-force-driven convection at gas-evolving electrodes

“…It would be certainly more appropriate to compare the instability of the bubble-driven flow to the instability of a single-phase natural convection flow along a vertical plate as it was investigated, e.g., by Hieber and Gebhart (1971). One could do so following the approach of Schillings et al (2015), but the calculation of the dimensionless parameters involves several quantities not available from the present measurements. Therefore, we resorted to the more easily accessible characteristic dimensions of a wall jet and found the agreement satisfactory.…”

Operation Strategy for Hydrogen Production by Water Electrolysis Powered by Solar Photovoltaic Energy

“…The studied variables in this paper were the temperature (between 30-70ºC), electrode-membrane distance (0.9, 1.5, 4 and 10 mm) and electrolyte flow rate (from natural convection to 2.8 l/min), according to a central composite design. These variables have been studied previously by different authors [7], [8], [13], [15]. In the following subsections the main results are shown.…”

“…5b). On the other hand, the Stokes velocity (u St ) is the terminal velocity at which a bubble of density "ρ g " and diameter "Ø g " will rise in a medium (30-35 wt% KOH) of density "ρ L " and dynamic viscosity "µ L " [13]:…”