Fundamental mechanisms of coalescence filtration with a particular focus on the influence of increased temperature and reduced flow velocity

• Applicant: Professor Dr.-Ing. Achim Dittler
• Subject Area: Mechanical Process Engineering
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 553958833

Coalescence filters are established elements of filtration technology used for droplet separation. The mechanisms involved and their dependence on operational parameters, material parameters, and other factors, such as the geometric arrangement of filter elements, result in complex relationships that need to be considered when designing a coalescence filter in terms of overall separation efficiency and pressure drop. Energy consumption is increasingly important in terms of economic viability and sustainability. In coalescence filtration, energy consumption can be reduced by minimizing pressure drop, which in turn can be achieved by reducing flow velocities. Additionally, there is limited information in the literature regarding the effects of elevated temperatures as encountered in real filter operation. However, the existing knowledge about the effects of elevated temperatures did not align with the results of our own preliminary investigations. This indicates that there is still a lacking fundamental understanding of the effects of media and operational parameters on basic mechanisms in coalescence filtration. Therefore, within the scope of this project, the influence of increased temperature and reduced flow velocity on filter properties (pressure differential, saturation behaviour, separation efficiency) will be comprehensively examined by gradually increasing the level of analysis from individual fibers to fibrous structures and ultimately to full-scale filters. For the experimental series, two existing test setups from extensive preliminary experiments and the current DFG project ill be reused in modified form. The goal of this project is to investigate the influence of temperature and gas velocity on transport behavior, detachment behavior, coalescence kinetics, drainage, and local saturation with high temporal and spatial resolution at different structural levels. For this purpose, oil will be applied to the filter media through the controlled addition of liquid volumes in the nanolitre range, as well as through mist deposition. In the next step, investigations will be expanded to real full-scale filters. Based on the insights gained at the micro and meso levels, pressure drop, separation efficiency, local saturations, and drainage in oil mist filtration will be analyzed. Understanding the influence of reduced flow velocity and increased operating temperature, on the fundamental mechanisms a more energy-efficient application of coalescence filters shall be achieved.

• DFG Programme: Research Grants