Numerical investigations of effects of the interdigitated channel spacing on overall performance of vanadium redox flow batteries

The spacing between neighboring interdigitated channels is one key design parameter of the interdigitated flow field (IFF) for vanadium redox flow batteries, since it directly influences the flow distribution and velocity magnitude of the electrolyte across the entire porous electrode, thus simultaneously impacting on the pumping loss and mass transport loss. In this work, the numerical model and systematic evaluation method are constructed to study the effects of channel spacing on the overall cell performance at the wide range of operating conditions. A 3-D CFD model is developed to calculate the pressure drop and pumping loss of the IFF-based cells with different channel spacing and flow rates, and a 3-D coupled electrochemistry/mass-transfer model for a representative unit of the cell is established to investigate the output cell performance with different channel spacings and flow rates. Based on the electrochemical performance and pumping loss, a comprehensive analysis is conducted to reveal the mechanism that how the channel spacing impacts the overall performance of the cell. The results show that the optimized channel spacing under different current densities and flow rates in the present case is 3 mm.