Characterization of fluid dynamics and mass-transfer in an electrochemical oxidation cell by experimental and CFD studies

Abstract

Flow and mass-transfer in a widely used commercial electrochemical flow cell (DiaCell ®) were investigated by computational fluid dynamics (CFD) simulations and validated by experimental measurements. Both qualitative and quantitative comparisons were made for distinct flow regimes in the Reynolds range between 25 and 2500 (based on the inter-electrode distance and on the superficial velocity in the cell middle cross-section area). A mono-phasic CFD methodology was applied for describing the rather complex bi-phasic phenomena taking place in the electrochemical oxidation of organic compounds, where gases are being formed at both electrodes. The adequacy of this assumption was subjected to validation with experimental results. Transient CFD simulations showed that the flow becomes unsteady at a rather low R e (in the range from 65 to 100) mainly due to the observed flow separation upstream the electrodes region. The pressure-drops determined by CFD agreed very well with the experimental measurements. Good agreement was also obtained between the Sherwood values calculated through CFD and experimentally determined by the limiting current technique. Mono-phasic CFD and experimental limiting current data were used for deriving mass-transfer correlations for the DiaCell ®. These correlations were found to correctly describe S h values determined from galvanostatic (electric current density of 332 A/m 2) electrochemical oxidation of selected organic compounds under mass-transfer controlled operating conditions and a turbulent-developing flow regime. These results suggest that turbulent-developing flow in an electrochemical cell can be sufficiently well described by mono-phasic CFD simulations.