PleatLab. A pleat scale simulation environment for filtration simulation
On the micro-scale, the detailed geometry of filter media can be considered. With such high resolution, filtration simulations can directly model all different effects that contribute to the filter efficiency, such as interception, inertial impaction and diffusion. However, on the pleat scale, the filter media is not resolved and must be modeled as homogenized cells with defined permeability. Explicit modeling of the interaction between the particles and the media is not possible. We develop an environment for numerical experimentation combining GeoDict® and MATLAB® for pleat scale filtration simulations by separating the direct interaction from the simulation, yet accounting for the micro-scale filter efficiency and pleat scale flow simulation by statistical methods. The combination of GeoDict® and MATLAB® is called PleatLab. The flow field is computed by solving the Stokes-Brinkman equations. In these, the additional term models the permeability of the filter media that cannot be resolved on the scale of a complete pleat; the permeability of the porous media formed by the sub-grid sized deposited particles, and the combination of the two. The filter efficiency of flat sheet media can be obtained from micro-scale simulations or experimental measurements. By analyzing particle paths, the probability of a particle being captured is modeled. In turn, captured particles lead to lower permeability of the pleat and increased capturing probability for later batches of particles over time. With PleatLab, all three phases of pleat clogging, namely in-depth filtration, cake filtration, and surface reduction, can be modeled. Also, the modified SIMPLE-FFT algorithm accelerates the flow simulation greatly and allows simulations to be performed in a timely manner. Besides, task automation, automatic result extraction and improved pre- and post-processing make PleatLab a user-friendly environment for performing research employing pleat scale filtration simulations. The comparison is made between results simulated with PleatLab and experimental data for a pleated filter. A good agreement is found for the evolution of the overall pressure drop across the filter element during clogging for a given flow rate.