Filtration of Chain Aggregate Aerosols by Model Screen Filter

A screen type diffusion battery was used as a model screen filter for studying the filtration of chain aggregate aerosols. The aerosols, with well-defined diameter and length, were generated with a system that included a flame aerosol generator and a differential mobility analyzer. Particle sizes were characterized using transmission electron microscopy and a digital image processing technique. The penetration efficiency of the aerosols through even stages of the diffusion battery at certain flow velocities were measured using a condensation nucleus counter (CNC). Quantitative data were obtained by operating the CNC in count mode simultaneously with a laser aerosol spectrometer. Results indicated that penetration efficiency decreased exponentially with the number of screens and increased with flow velocity. In addition, theoretical analysis of filtration mechanisms based on the fan model theory has been made and compared with the measurements of penetration efficiency. Results showed that the collection of chain aggregates on model screen niters was in the regime dominated by an interception mechanism. Average orientation angles of the aerosols with respect to the flow field were also estimated.