Numerical Modeling of Aerosol Transport and Dynamics

Abstract

Flow and aerosol transport and dynamics in a reaction chamber, part of an aerosol generation system, is analyzed by coupling Computational Fluid Dynamics (CFD) and Aerosol Dynamic Equation. A predictable parametric aerosol output from reaction chamber is desirable for different contexts. The effect of residence time of the aerosol particles and mixing characteristics of the flow on the aerosol size distribution is analyzed using the ANSWER finite volume CFD code. The ANSWER uses the steady state turbulent flow field to solve the General Dynamics Equations (GDE) for the aerosol particles. The GDE includes mechanisms such as coagulation, gravitational settling and thermophoretic drift etc. A volume (and mass) preserving nodal method is implemented to model particle distribution changes due to coagulation. The modules modeling coagulation and gravitational settling were validated with respect to analytical solutions taken from the literature. The size distribution in reaction chamber design is seen to be robust for various flow scenarios at inlet number concentration of 1 × 1012/m3. This is explained by flow time scale being much smaller than coagulation time scale. At higher inlet concentration of 1 × 1015/m3 the average size distribution and outlet size distribution are significantly shifted from the inlet distribution, due to the much lower coagulation time scale. A noticeable difference between no or low swirl and high swirl flow is seen. A secondary ring inlet within the reaction chamber was seen to lead to identical aerosol distribution for different flow scenarios even at higher inlet concentration.