Proceedings of the
International Conference on Mechanical Engineering 2009
(ICME2009) 26- 28 December 2009, Dhaka, Bangladesh

ICME09-FM-01

VIRTUAL IMPACTORS: A NOBLE DEVICE TO GENERATE HIGH
CONCENTRATION MONODISPERSE AEROSOLS

M. Shamim Akhter1, M. Ariful Islam2 and M.R. I. Sarker1
1Department of Mechanical Engineering, RUET, Rajshahi, Bangladesh
2Department of Industrial & Production Engineering, RUET, Rajshahi, Bangladesh

ABSTRACT

A solid or liquid particle suspended in a gas which is usually air is called an aerosol. Dust, fume, smoke, mist, fog, smog, and cloud are all examples of aerosols found in nature. One of the important applications of aerosol technology is the production of monodisperse test aerosols used for aerosol research, calibration, testing and development of air-cleaning and air-sampling equipments and pollution abatement. The characteristics of an ideal aerosol generator are a constant and reproducible generation of mono disperse, stable, uncharged, spherical aerosol particles whose size and concentration can be easily controlled. Atomization produces aerosols with sufficient mass concentration but the generated aerosols are highly polydisperse. Therefore, polydisperse aerosols produced by atomization should be subsequently segregated to narrow size range so as to obtain aerosol appropriate for use as a test aerosol. A monodisperse aerosol is usually defined as one that has a geometric standard deviation of less than 1.2. An aerosol having geometric standard deviation from 1.2 to 1.5 is said to be narrowly distributed. Polydisperse aerosols have geometric standard deviation greater than 2.0. Virtual impactors are widely used in the sampling of particles because they generate high concentration aerosols. This technology is new in Bangladesh. This paper describes the technical aspects of virtual impactor so as to introduce the reader with this new technology. Results of experimental studies performed with an improved virtual impactor have also been described. It was possible to generate narrowly distributed aerosols with the improved virtual impactor employed. 

Keywords: Aerosols, Virtual impactors, Monodisperse.

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