Electrovortex flow in liquid gallium

Liquid metal batteries are a promising energy storage technology where the electrodes and electrolyte are liquid. The interaction of the current in these batteries with its own magnetic field induces electrovortex flow (EVF) in the conducting fluids. Understanding convection and EVF in these devices and their interactions is crucial: although induced flows can enhance mass transfer, if the flows are fast enough they could disrupt the electrolyte layer and short the battery internally. Therefore, it is important to determine the current ranges at which unfavorable flow occurs.

We present results from a laboratory model developed for studying combined thermal convection and EVF in these batteries. Our experimental setup is a cylindrical container with one electrode entering the vessel at the top center and the other being the bottom plate. We characterize the different flows that are present as the current is varied (characteristic of battery transients) and their interactions. Our analysis shows that localized convection around the top electrode dominates at low current evidenced by a convection roll. As current increases, EVF dominates, suppressing convection and drawing energy from swirl flow which is driven by the interaction of the current with the Earth’s magnetic field. Utilizing these results, we can determine operating current ranges at which liquid metal batteries are most stable.