Active Sensors for Gas-Liquid Mass Transfer Studies in Capillaries

Gas-liquid and gas-liquid-solid reactions in microstructured devices are an active field in scientific research with many industrial applications. High surface-to-volume ratio as well as enhanced heat and mass transfer are advantageous making microstructured devices a promising technology to overcome mass transfer limitations. The implementation of traditional sensors and analytical methods is a drawback when investigating mass transfer phenomena within microstructured devices, since they disturb the flow and reactor characteristics. Offline measurement techniques provide limited insight into flow structure, while noninvasive online measurement techniques either cannot provide local results or require a sophisticated setup. In this work, a noninvasive ultrasonic sensor (SONOTEC, Germany) is used to measure particle concentration and bubble length in Taylor flow. Particle concentration and bubble detection is derived from the ultrasonic signal. Further, an Arduino based slider setup is developed, which is equipped with a computed-vision system to track bubbles in Taylor flow. This setup can be combined with optical analytical methods allowing for investigating the entire life time of a single bubble or liquid slug.