Mass Transfer in Dispersed Liquid-Liquid Systems

• Applicants: Professor Dr.-Ing. Matthias Kraume; Professor Dr.-Ing. Tim Zeiner
• Subject Area: Chemical and Thermal Process Engineering
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 524980331

Interfaces play a crucial role in fluid process engineering since they determine the mass transfer between two immiscible phases. The analysis of transport processes is challenging due to the fluid character of the interface and, in particular, the small scales, which cannot be resolved experimentally. Therefore, this project proposes a combination of experiment and modeling to elucidate the processes at interfaces. For this purpose, mass transfer in dispersed liquid/liquid systems is investigated. Ternary systems with a miscibility gap and different transferring components are considered model systems. By doing so, the influence of various parameters on mass transfer, such as viscosity, density difference, phase behavior, interfacial tension and also enrichment at the interface, can be characterized. Experimentally, the mass transfer of acoustically levitated droplets is measured. Here, the droplet is fixed in the continuous phase locally by a standing ultrasonic field so that the droplet is not disturbed by external influences. The existing experimental setup shall be optimized in terms of accuracy and reproducibility. For the first time, by the combination of optical measurement and acoustic levitation, the mass transport at single droplets can be quantified and visualized non-invasively with high temporal resolution. In the field of modeling, the interface itself is resolved using density gradient theory in combination with the Non-Random Two-Liquids model. In this way, enrichments at the interface can be quantified. Based on the developed model, both the phase equilibrium and the interfacial tension at equilibrium can be calculated. Consequently, the model shall be extended to a consistent mass transfer model. Within the scope of this project, it will be used for the first time as the basis for calculating mass transfer in dispersed systems. For this purpose, it will be coupled with the Navier-Stokes equations. The goal is to predict phenomena like Marangoni convection. If successful, a new methodology will be developed that will allow the prediction of interfacial phenomena by combining experiment and model for the first time. In addition, the available database for time-resolved mass transfer and related physical properties will be expanded, and new experimental methods will be made available.

• DFG Programme: Research Grants
• Co-Investigator: Dr.-Ing. Lutz Böhm