Design of fibrous filter media based on the simulation of pore size measures

Filtration media including woven cloths, nonwoven, membranes and particulate beds are used in a wide variety of applications such as biotech, health care, pharmaceutical, food and beverages, power sources and chemical industries. One way to characterise the performance of all these filtration media is by the pore structure characteristics of the media. Several experimental techniques are available to measure such characteristics, each of them producing a different outcome. Having the aim to find the optimal design of filtration media with numerical simulations, it is necessary to be able to predict the outcome of pore size measurements as this allows a comparison of virtually created filtration media with existing filtration media. This paper focusses on the numerical simulation of mercury intrusion porosimetry and liquid extrusion porosimetry. First, the numerical method will be introduced and applied on a sample nonwoven. Results of both methods will be presented and related to the real pore structure of the medium. Afterwards, the influence of a change in a single production parameter on the pore distribution will be investigated exemplarily. Finally - to validate the method - the numerical results will be compared with experimental findings. With the method presented the outcome of pore size measurements performed by mercury intrusion porosimetry and liquid extrusion porosimetry can be predicted. This is of great importance when designing filtration media virtually as pore size distributions calculated with the standard 'geometric' approach are in general not comparable with measurements. The examples presented in this paper show that the geometric approach overestimates the amount of large pores when compared to measurements. In combination with Navier-Stokes simulations the method could also be used to model flow porometry measurements but this approach would be numerically costly and is not presented here. Entnommen aus <a_href="http://www.fiz-technik.de/db/b_tema.htm" target="_blank">TEMA</a>