The transport processes in multiphase systems depend on the properties of the interface between the immiscible phases. Interfacially active substances occur in a variety of industrial applications: on the one hand, they are deliberately used to intensify processes, or they are present undesirably, for example as impurities or by-products. Through adsorption and desorption at the interface (see figure at the top), they have a significant influence on the transport processes that occur and consequently on important process variables.
In addition to the adsorption of the surface-active molecules at the interface, other interfacial effects occur, such as the Marangoni effect. In work already carried out, both a reduction and a possible improvement in mass transfer have been observed. The prediction of the occurrence of interfacial phenomena, of process variables and of a possible reduction or intensification of the transport processes in the presence of interfacially active substances represents a major challenge in multiphase systems.
This work focuses on fluid dynamics and mass transfer in disperse systems. The experimental data obtained in the present project by single droplet experiments show a superposition of the mentioned effects. Detailed spatially and temporally resolved measurements of fluid dynamics (see video in the middle) are used as a sensitive measurement method. In addition, mass transfer measurements on single droplets are performed. With help of the specifically constructed color gradient schlieren photography, the concentration field during the droplet ascent is visualized (see video at the bottom) to interpret the obtained results and to achieve a better understanding of the occurring interfacial phenomena.