Enhanced power law agglomerate growth in the free molecule regime

Abstract

Aerosols generated at high temperatures tend to form agglomerates which can be characterized by a power law exponent, similar to a fractal dimension. The coagulation dynamics of these particles can be described by a modified collision kernel for the free molecule regime. The collision kernel for power law (fractal-like) particles is a homogeneous function, and the equation is solved using self-preserving size distribution theory for fractal dimensions between 2 and 3. The effects of fractal dimension and primary particle size on agglomerate growth and the size distribution are very strong. Agglomerate growth is rapid at low fractal dimension and fine primary particle size, because the collision cross-section is much larger for the same agglomerate mass. The effect of primary particle size on the rate of particle growth becomes more significant with decreasing fractal dimension, and the particle size distribution becomes much broader at low fractal dimensions.