The free-molecular coagulation model has been validated against one of the examples given by Frenklach and Harris[135] .
Consider a population of soot particles in a closed batch reactor.
Initially the particles have the same size, that is, are mono-dispersed, and the number density
of the particles is 1012 cm-1. The
pressure and temperature of the reactor are kept constant at 1 atm and 1500 K, respectively.
The bulk species comprising the soot particle is carbon atom (
= 3.18 x 10-21 g) and the bulk density of the
particle core, 
, is 1.8 g/cm3.
The simulations were performed with Ansys Chemkin’s homogeneous, closed reactor with Particle Tracking Feature. The chosen gas-phase mechanism and thermodynamic data are from Appel et al.[134] and the surface chemistry is created by Chou et al. of Reaction Design.
The time profiles of particle number density and average particle diameter squared predicted by Ansys Chemkin using Particle Tracking are plotted in Figure 19.7: Evolutions of number density, ND, and ensemble average of diameter squared from the method of moments by Frenklach and Harris[135] (solid lines) and from Chemkin with Particle Tracking (dashed lines) together with the ones computed and published by Frenklach and Harris[135] . Good agreements between the two models validate the coagulation model implementation.
Figure 19.7: Evolutions of number density, ND, and ensemble average of diameter squared from the method of moments by Frenklach and Harris[135] (solid lines) and from Chemkin with Particle Tracking (dashed lines)
