Flow cell characterisation: flow visualisation, pressure drop and mass transport at 2D electrodes in a rectangular channel

Abstract

The reaction environment in a C-Flow Lab 5 × 5® laboratory-scale electrochemical flow cell was characterised in terms of fluid flow, hydraulic pressure drop and space averaged mass transport coefficient. The cell was studied in flow-by configuration with smooth, planar electrodes within its rectangular flow channels. The effect of a turbulence promoter (a polymer mesh with a volumetric porosity of 0.84) placed next to the working electrode was also evaluated. Electrolyte volumetric flow rates ranged from 0.3 to 1.5 dm3 min-1, corresponding to mean linear velocities of 2 to 10 cm s-1 past the electrode surface and channel Reynolds numbers of 53 to 265. The pressure drop was measured both over the electrode channel and through the whole cell as a function of mean linear velocity. The electrochemical performance was quantified using the limiting current technique, which was used to determine the mass transport coefficient over the same range of flow rate. Results were compared to well-characterised electrochemical flow reactors found in the literature. The mass transport enhancement factor due to the presence of the turbulence promoter was between 1.6 and 3.9 under the studied conditions. Reactant conversion in batch recirculation mode and normalised space velocity were predicted from the electrochemical plug flow reactor equation.

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