Dynamic Behavior of Fibrous Filters during Collection of Submicrometer Aerosols: A Dispersion Model
Final rept. 1 Oct 1987-31 Dec 1990
MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMICAL ENGINEERING
Pagination or Media Count:
A novel fundamental theory of the dynamic behavior of fibrous filters for aerosol collection is proposed. The theory is based upon an explicit and systematic procedure for calculating the filter efficiency and for qualitatively describing the filter microstructure, both of which change continuously during filter operation as aerosol particles deposit on the fibers. This theory is free of any of the usual ad hoc assumptions, including the artificial concept of single fiber efficiency nc, explicit or implicit theories. Upon viewing the filter bed as a continuum, the aerosol transport and deposition processes at this coarse-scale level of description are characterized by three fundamental global phenomenological coefficients 1 the mean aerosol velocity vector 2 dispersivity dyadic and 3 mean volumetric aerosol deposition-rate coefficient K. Whereas for clean homogeneous filters these phenomenological coefficients are constants, continuous aerosol deposition on the fiber surfaces causes them to vary with both time t and position R within the filter bed. The filtration efficiency may be rationally expresses explicitly in terms of these three physically realistic, experimentally accessible quantities.
- Physical Chemistry