Toward Reliable Local Fluid Dynamic Measurements in Extraction: A Film Sensor Approach in Miniaturized Setups

Conductivity-based liquid film thickness sensors were adapted from gas–liquid applications to liquid–liquid extraction systems, where they enable spatially and temporally resolved investigations of droplet flows inside structured packings. Two sensor designs were evaluated and integrated into dedicated measuring cells. Experiments with single droplets of butanol, butyl acetate, and silicone oil demonstrated that droplet velocity, residence time, and size can be measured in good agreement with optical reference methods. Complementary simulations revealed the influence of droplet position, size, and distance from the sensor surface on the signal response and confirmed the feasibility of droplet size determination under idealized conditions. The combined results establish the measurement principle as a proof of concept and highlight its potential for future studies on droplet distributions and phase interactions in extraction columns.