Coalescence filters are essential for removing oil mist in compressed air systems. Operating these filters at reduced face velocities offers significant potential for energy savings. Investigations under real operating conditions, particularly at elevated temperatures typical of compressor discharge, are essential to verify whether the potential benefits of lower filter face velocities, such as the reduced energy consumption, are realized in practice. However, most studies have been conducted under laboratory conditions. Preliminary experiments at 80 °C revealed unexpected filter behavior, deviating from theoretical predictions based on the “jump-and-channel” model. These deviations highlight gaps in mechanistic understanding.

This contribution proposes an experimental approach to study coalescence filtration mechanisms across three observation scales: single fibers and fiber arrays (micro), non-woven structures (meso), and full filters (macro). This multi-scale approach has been selected since the macroscopic filter performance results from mechanisms at smaller scales not observable at the filter level. In order to identify how the operating conditions influence the filter behavior, the setup allows for the systematic investigation across the temperature range from 20 °C to 80 °C, with adjustable filtration velocities ranging from 2 to 10 cm/s. A modular filter holder ensures reproducible conditions across all scales within the same filter chamber, which features a glass window enabling optical observation. Specific target parameters such as differential pressure or local saturation are defined in order to characterize the relevant mechanisms at each level.

The proposed approach aims to explain the underlying mechanisms of coalescence filtration by combining the observations from all three scales. Furthermore, it can explain how these mechanisms are affected by reduced face velocities and temperature-induced changes in fluid and media properties, establishing a basis for energy-efficient filter optimization.