Computational and Experimental Study of Convection in a Vanadium Redox Flow Battery Strip Cell Architecture

Abstract

The impact of convection on electrochemical performance, performance distribution, and local pressure drop is investigated via simple strip cell architecture, a cell with a single straight channel. Various channel depths (0.25, 0.5, 1, 2.5 mm) and flow rates (10–50 mL min−1 cm−2) are employed to induce a wide range of electrolyte velocities within the channel and electrode. Computational flow simulation is utilized to assess velocity and pressure distributions; experimentally measured in situ current distribution is quantified for the cell. Although the total current in the cell is directly proportional to electrolyte velocity in the electrode, there is no correlation detected between electrolyte velocity in the channel and the total current. It is found that the maximum achievable current is limited by diffusion mass transport resistance between the liquid electrolyte and the electrode surfaces at the pore level. Low electrolyte velocity induces large current gradients from inlet to outlet; conversely, high electrolyte velocity exhibits relatively uniform current distribution down the channel. Large current gradients are attributed to local concentration depletion in the electrode since the velocity distribution down the channel is uniform. Shallow channel configurations are observed to successfully compromise between convective flow in the electrode and the overall pressure drop.

Keywords

• vanadium redox flow battery
• strip cell
• convective mass transport
• current distribution
• CFD
• model validation