Ultrasound flow mapping in a model of a secondary hydraulic zinc-air battery

The investigation of complex multiphase flows is relevant for a wide range of industrial processes. For example, the performance of secondary hydraulic zinc-air batteries, here referred to as zinc-air flow batteries (ZAB), where the energy is stored in microscopic zinc particles suspended in an aqueous electrolytic solution (i.e. suspension electrode), strongly depends on the suspension flow in the electrochemical cell. To improve the design of the fluidic cell structures, detailed knowledge of the local flow conditions is required. Flow measurements can be performed inside the opaque fluid using ultrasound technology, if the acoustical properties, i.e. attenuation and speed of sound are known. These properties strongly depend on the characteristics of the multiphase fluid, e.g. the density, compressibility, thermal conductivity and the concentration of the individual phases. Hence, a characterization of the multiphase fluid to parameterize the measurement system is needed. We present results from experimental characterization measurements of a suspension electrode for zinc-air flow batteries, applying a spectroscopic method to parametrize the measurement system for the flow mapping. Finally we present flow mapping results from a fluidic ZAB model and compare them to numerical results from multiphase CFD-DEM simulations.