Electro-vortex flow may appear when currents converge or diverge inside a liquid conductor. It is a well known phenomenon in arc welding, vacuum arc remelting, aluminium electrolysis and electro slag remelting. In liquid metal batteries, electro-vortex flow will typically appear near the current collectors (fig. 1). It drives a flow away from the walls. Electro-vortex flow can be highly beneficial for enhancing mass transfer in liquid metal batteries. However, it should not be too strong in order to avoid a deformation of the electrolyte layer.
|Fig. 1: Sketch of electro-vortex flow in a liquid metal battery.||Fig. 2: Experiment on electro-vortex flow.|
The direction and magnitude of the electro-vortex flow can efficiently be controlled by the placement, conductivity and diameter of the feeding cables of the battery. At HZDR we optimise these parameters in order to increase mass transfer in the cathode of the cells. We conduct both experiments (fig. 2) as well as numerical simulation (fig. 3).
A recently developed solver for electro-vortex flow allows for computing the current distribution in the whole battery, including the feeding lines. In contrast to the experiments it allows exploring the influence of the Earth magnetic field, as well. If no vertical fields are present, the flow in the battery would be purely poloidal (fig. 4, left). However, already the very small Earth magnetic field leads to a helical or swirling flow (fig. 4, right).
Fig. 4: The Earth magnetic field transforms the original poloidal flow (left) into a helical flow (right).
- Ashour, R.; Kelley, D.; Salas, A.; Starace, M.; Weber, N.; Weier, T.
Competing forces in liquid metal electrodes and batteries
Journal of Power Sources 378(2018) 301-310
- Weber, N.; Beckstein, P.; Galindo, V.; Starace, M.; Weier, T.
Electro-vortex flow simulation using coupled meshes
- Weier, T.; Bund, A.; El-Mofid, W.; Horstmann, G.M.; Lalau, C.-C.; Landgraf, S.; Nimtz, M.; Starace, M.; Stefani, F.; Weber, N.
Liquid metal batteries - materials selection and fluid dynamics
IOP Conference Series: Materials Science and Engineering 228(2017), 012013
- Stefani, F.; Galindo, V.; Kasprzyk, C.; Landgraf, S.; Seilmayer, M.; Starace, M.; Weber, N.; Weier, T.
Magnetohydrodynamic effects in liquid metal batteries
IOP Conference Series: Materials Science and Engineering 143(2016), 012024
- Starace, M.; Weber, N.; Seilmayer, M.; Kasprzyk, C.; Weier, T.; Stefani, F.; Eckert, S.
Ultrasound Doppler flow measurements in a liquid metal column under the influence of a strong axial electric current
Magnetohydrodynamics 51(2015)2, 249-256
- Weber, N.; Galindo, V.; Priede, J.; Stefani, F.; Weier, T.
The influence of current collectors on Tayler instability and electro-vortex flows in liquid metal batteries
Physics of Fluids 27(2015), 014103