Macro-scale modeling and simulation of two-phase flow in fibrous liquid aerosol filters

Similar to fine dust, liquid aerosols represent a risk to human health since small droplets may enter the respiratory system and cause health problems or severe diseases, such as COVID-19. Oil mist emissions from production processes and from air brakes are reduced by filters and by air dryer cartridges, respectively, while virus-like aerosols are removed by face-masks. Since the two-phase flow processes involved are highly complex and occur on vastly different scales ranging from the scale of single droplets and fibers up to the scale of a whole filter or face mask, the modeling and simulation is extremely challenging. In this work, we present a macro-scale approach for modeling and simulation of the two-phase flow processes in fibrous filters which allows predicting both pressure loss and filtration efficiency from new to steady-state where material parameters and constitutive relationships are obtained based on nano CT scans and micro-scale simulations. Compared to previous work, this approach starts from a physical basis as it relies on mass and momentum conservation and is then closed by material laws. Using this macro-scale approach it is found that both pressure loss and oil mass at steady-state are in good agreement with experimental findings.