Development of an analytical model to account for local porosity variations and anisotropy effects on the permeability of fibrous media

F. Theron*, E. Lys, L. Le Coq, IMT Institut Mines Télécom Atlantique; France; S. Woudberg, Stellenbosch University, South Africa

The prediction of the permeability of fibrous media is a major challenge due to their complex structure. For the case of media used for aerosol filtration, in particular, the determination of the permeability is an important issue as it influences the filter performances (e.g. pressure drop and collection efficiency). Almost all of the numerous empirical or analytical models to predict the permeability of fibrous media take into account two parameters to depict the average structural properties of fibrous media: the porosity (or solid volume fraction) and the fibre diameter (or radius). Due to the local variations that those parameters can exhibit, the models often fail to accurately predict the permeability. Moreover, due to their manufacturing processes, fibrous media can exhibit anisotropic fibrous structures. Furthermore, since in ventilation facilities, for example, the airflow mostly penetrates the filter through pathlines normal to the medium, their through-plane permeability is generally determined through pressure drop measurements in flat configurations normal to the flow. The through plane flow model of Tomadakis and Robertson for example was dedicated to predict the permeability of this type of flow.

The first objective of this study is to compare experimental permeability values of three fibrous media used for air filtration to model predictions from the literature (e.g. the Tomadakis and Robertson model), and especially to the analytical Representative Unit Cell (RUC) models developed for through plane flow and isotropic fibrous media (by Woudberg [2]), as shown on...

... The comparison of the experimental permabilities of the three actual media studied to the predicted ones shows that all the models under-predict the experimental values, but with...

Session: G12 - Modelling and Simulation
Day: 14 March 2018
Time: 16:45 - 18:00 h

Learn more at FILTECH 2018 - Register Now!