FILTECH 2022, The Filtration Event

Cologne, Germany

08.-10.03.2022

M. Böhle, R. Kirsch, S. Osterroth, A. Schwarzwälder

The last two years have shown an increasing awareness of the use of face masks and respirators in order to protect the wearer or the surrounding people against infections. Two protection concepts can be distinguished: self-protection and external protection. In the first concept, the wearer wants to protect himself or herself against infectious pathogens or viruses in the surrounding. Depending on the availability, corresponding filter masks should be preferably used by people working in health and nursing care. In the second concept, the wearer protects people in the surrounding from being infected.

Specialized computer simulation tools have proven to be very useful for the innovation and optimization of filtration devices. Previous studies were mostly focusing on filtration efficiency and have not considered the moisture transport. Additionally, the breathing behavior was modeled using an idealized sinusoidal profile or a set of linear functions.

The present work is devoted to the adaptation of well-known transport models to the transport of moisture in porous media. Therefore, the rate parameters are adjusted in a phenomenological way to effects as moisture capacity, drag, or capillary effects.
In a first step, a one-dimensional model is sufficient to identify model parameters. One important ingredient is a suitable modeling of the breathing behavior. Either an idealized profile can be used (depending on breathing frequency and peak inhalation flow rate) or a measured cycle. In the second step, the model is extended to include also the detailed geometry of the face mask. Using 3D simulations, it is shown that the conditions at the interface between the mask and the atmosphere have a significant influence on the dynamic moisture propagation in the mask. Thus, it should be also taken into account for 1D simulations as well as bench tests.

Those details are not only important for the user but also the manufacturers, which can design and optimize their products for the intended usage. The modeling approach is presented and illustrated by examples.