Validation of a new phenomenological “jump-and-channel” model for the wet pressure drop of oil mist filters

Oil transport across media interfaces (i.e. transitions between regions of different porosity and/or wettability) was associated with a relatively sharp increase in pressure drop ∆p and oil saturation S over a very thin layer of the filter (a “∆p jump”). The magnitude of this ∆p jump was determined by the media properties. It correlated well with the respective static break-through pressures for oil or air, but did not depend on the oil viscosity and loading rate of the filter (at constant air velocity). Oil transport through channel regions of the filter (i.e. the regions connecting interfaces) was associated with a linear increase in ∆p with channel length and liquid throughput. The corresponding saturation level S was relatively flat throughout the channel region and lower than at an interface. (Both quantities are media dependent, of course.) An increase in oil viscosity μ (at constant oil throughput) led to different responses depending on filter wettability.