Filtration properties of glass bead media for aerosol particles in the 0·1–2 μm size range

Abstract

Filtration properties of glass bead media for aerosol particles in the 0·1–2 μm size range are studied. Monodisperse aerosols of polystyrene spheres are used and concentration measurements in front and behind the filter are carried out with a Laser Aerosol Spectrometer. For the bead sizes investigated (0·4, 0·16, 0·05, 0·0185 cm in dia.) the porosity of the filter is found to be always 38·5 per cent. The mean flow velocity inside the filter changes from about 0·7 to 17 cm sec −1. Within this range a linear relationship between pressure drop and flow velocity is measured and with respect to the bead size the law of Hagen-Poiseuille is valid. The penetration maximum proves to be a function not only of the particle diameter, but also of the flow velocity and the bead size. In the particle size range of predominating diffusion the penetration can be generally expressed by: c c o =e − 6.39 D 2 3 .L v 2 3 .R 5 3 K L—filter length; D—diffusion constant; v—mean flow velocity; R K—bead radius). For bigger particles the coexistence of gravitational and inertial deposition prevents an exact analysis of the experimental results.