Hydrodynamic design of electrochemical reactors based on computational fluid dynamics

The design of electrochemical reactors using computational fluid dynamics (CFD), was investigated. A numerical methodology which considers a complete solution of transport governing equations of fluid dynamics linked together to the electrochemistry was developed. Emphasis was put on the boundary layer region, where most of the reactions between electrolyte and cathode take place, as well as mass transport, km. Properties of cupric sulfur (CuSO4 + 5H2O) compound were considered in the mass transport simulating as part of an electrodeposit process in a parallel plate channel filter-press cell. The proposed design method does not make use of correlations where km is proportional to bulk dimensionless parameters like the Reynolds (Re), Sherwood (Sh), and Schmidt (Sc) numbers. Electrochemical reactor′s design based on these bulk parameters requires a fully developed flow condition that warranties the accuracy of the km calculation. Instead, many designs of reactors can be evaluated in terms of their effective electrochemical reactions if the km and other variables are calculated at the electrolyte dynamic condition in the region of electroactivity, despite it is part of a fully developed flow or not. The Reynolds equations were solved using the commercial code ANSYS Fluent, and turbulence was modeled using the RNG k-ε model. The method was validated by comparing the predicted results against velocity measurements, conducted in a laboratory model of filter-press reactor using particle image velocimetry, PIV. Measured data and predictions showed a channel flow of strong velocity gradients and a recirculation zone. Calculated profiles of km along the reactor were compared using both the measured and predicted velocity. A comparison of reported results for the FM01-LC electrolyser against the present method demonstrates that the use of CFD allows accurate designs. This is because the electroactivity and dynamics are both taken into account in the viscous sub-layer. The method can be useful for the design of electrochemical parallel plate reactors involving mass transport and chemical reactions near the cathode operating under laminar or turbulent flow conditions.