The air flow resistance of glass fibre filter paper

The air flow resistance of filter papers containing fine glass fibres was measured in the region of streamline flow. Average fibre diameters ranged from 0.18 to 14.4 microns and paper porosities from 0.75 to about 0.94. At atmospheric pressure, the data were correlated by the equation which was derived from an expression for the drag force on an individual fibre perpendicular to the direction of flow. The resistance coefficient k varied with fibre diameter according to the empirical relationship and was about 30 for the largest fibre diameter and 1.6 for the smallest. Two alternative methods are proposed for adapting the equation to pressures below atmospheric. La perte de charge causee par l'ecoulement d'air en regime laminaire dans des papiers-filtres contenant de la fibre de verre d'un diametre variant de 0.18 a 14.4 microns a ete mesuree. La porosite du papier variait de 0.75 a environ 0.91. La relation suivante, determinee a l'aide de la relation de la resistance a l'ecoulement perpendiculaire a une fibre individuelle, est presentee pour les conditions de pression atmospherique: Le coefficient de resistance k varie en fonction du diametre de la fibre selon la relation empirique suivante et est de 30 pour les grosses fibres et de 1.6 pour les plus petites. Deux autres methodes sont proposees pour adapter l'equation aux pressions sous-atmospheriques.