Oil mist coalescence filters are essential components in industrial compressed air systems due to their efficient separation of submicron oil droplets from the gas phase. Liquid transport within these multilayer filter systems is governed by complex interactions between airflow, capillary transport, and gravity-driven drainage, which strongly influence pressure loss and separation efficiency during operation. Recent investigations on spatio-temporal drainage in oil mist filters show significant gravitational drainage at the structural interfaces between the support structure and the drainage layer at a moderate filtration velocity of 25 cm/s.

This study presents an experimental methodology to resolve spatially and temporally differentiated oil drainage pathways in multilayer oil mist coalescence filters under realistic operating conditions. A gravimetric online measurement technique is developed to quantify individual drainage flows in real time. The setup combines an additively manufactured filter chamber with defined drainage segmentation and an optical observation system for the rear side of the filter, enabling direct correlation between drainage location, onset time, and pressure loss evolution.

Using this methodology, the influence of filtration velocity (25 and 50 cm/s) and drainage material pore size on oil transport, pressure loss, and separation efficiency for submicron droplets is systematically investigated. The approach allows the relationship between filtration conditions, gravitational drainage behavior, and structural interfaces within the filter to be resolved experimentally.