Numerical prediction of the properties of filter media and simulation of filtration processes in pleated filters

Detailed computer simulations are a recent, efficient way to gain valuable insights into filter materials and particle filtration processes. The scales where filtration phenomena can be observed range from the macroscopic regime of flow around a moving vehicle to the atomic regime of adhesion forces between dust particles and an electrically charged filter medium. These scale differences necessitate a complex modeling approach. With our virtual material laboratory software, GeoDict®, we simulate and try to understand these processes by considering two different scales. On the micro-scale, 3D models combined with micro Computer Tomography (mCT) images allow the realization of the detailed geometry of the filter media. Explicit modeling of the interaction between the particles and the media is possible. Filtration simulations can model the different effects that contribute the filter efficiency directly. The properties of the filter media, such as the porosity, pore size distribution, permeability, diffusivity, thermal and electrical conductivity, elasticity, filter efficiency, can be predicted. On the pleat scale, however, the filter media cannot be resolved and must be modeled as homogenized cells with defined properties. To simulate the filtration process on this scale, an environment for numerical experimentation combining GeoDict® and MATLAB®, PleatLab, is provided by accounting for the micro-scale filter efficiency, pleat scale flow simulation, and the capture probability model to determine whether a particle is captured. With PleatLab, all three phases of pleat clogging, namely depth filtration, cake filtration, and surface reduction, can be modeled. The results from the simulation agree well with the experimental measurements.