The single-fiber collision rate and filtration efficiency for nanoparticles ii: Extension to arbitrary-shaped particles

We extend the equations for the dimensionless collision kernel and filtration efficiency, attained previously via mean first-passage time (MFPT) calculations, to particles of arbitrary shape. Specifically, we show that the regression equations for the dimensionless collision rate found considering particle-fiber collisions driven by simultaneous diffusion and interception remain valid for non-spherical particles, provided that an appropriate collision length scale for the non-spherical particle (L) is defined and incorporated into the definitions of the dimensionless collision rate (H) and the diffusive Knudsen number (KnD). Regression equations are provided to calculate this length scale for quasifractal aggregates of varying fractal dimension, as well as cylinders. MFPT calculations reveal that, over ∼5 orders of magnitude in H, these regression equations for the collision length are valid. Furthermore, using the previously attained proportionality between the predicted dimensionless collision rate and the single-fiber efficiency, comparison is made between the equations presented here and measurements of the penetration of both multiwalled carbon nanotubes and quasifractal aggregates through fibrous filters. Reasonable agreement is found between measured and predicted single-fiber efficiencies in both circumstances, supporting the use of the single-fiber efficiency calculation approach we developed.Copyright 2014 American Association for Aerosol Research © 2014