Abstract
All the way through the Covid-19 pandemic, Math2- Market has been developing features in the GeoDict software to design, model, simulate and optimize filter media and filter elements at different scales. Many GeoDict users worldwide are pressing towards digital design of modern and optimized filters.
The study of the nano/micro structure of filter media is the starting point to understand, analyze, and optimize a filter. Often, the first simulation step consists of processing of nano/micro CT images of the real media to prepare a 3D nano/micro structure model of the filter media [1]. Alternatively, the 3D digital filter media can be modeled using different modules of GeoDict for structure generation.
The precise simulation of flow through nano fibers was a new feature of GeoDict 2020 based on the implementation of slip length and consideration of tangential slip flow on nano fibers. It enables filter media designers and manufacturers to digitally optimize their filter media. Especially when dealing with multi layers of filter media e.g., for face masks made from micro-fibrous and nano-fibrous layers.
For this presentation, the filtration behavior of a face mask was investigated by the Institute for Flow in Additively Manufactured Porous Structures (ISAPS) of the Heilbronn University of Applied Sciences. The filtration simulation using GeoDict was done under the same conditions as the experiment. A very good agreement was found between simulation results and experimental data. Then, GeoDict was used to optimize the filter media by generating various digital filter media and running and analyzing the filtration simulations.
Another important topic this year is the publicly funded project BiGOFil, aiming to develop coalescer filters with higher efficiency and lower pressure drop. The main focus is on increasing oil droplets coalescence and separation using non-round, profiled bicomponent fibers in a nonwoven medium. For Math2Market, the main task was to implement the computational models into GeoDict to simulate the droplets coalescence and also the detachment of large coalesced droplets through the media. In this presentation, the droplets coalescence on a single fiber and through a filter medium are shown. Further details and technical information will be presented separately by another speaker in the filtration session.
Finally, we present the simulation of the flow and filtration at room scale, e.g., in classrooms using air purifiers. The room CAD geometry, including walls, desks, chairs, shelves, etc. are imported into GeoDict and are voxelized. The CAD geometry of the air purifier is also imported. The effects of air purifiers at different flow rates, and the effect of their location in room, are investigated by running filtration simulations. The time required to minimize the aerosol concentration in room, besides operational and maintenance costs, is a key factor when choosing the right air purifier and the best location.
[1] D. Hoch, M. Azimian, A. Baumann, J. Behringer, J. Niessner, Comparison of Voxel-Based and Mesh-Based CFD Models for Aerosol Deposition on Complex Fibrous Filters, Chem. Eng. Technol. 2020, 43, No. 12, 2538–2547.
