Size effects in the growth of aerosol nanoparticles and their coalescence

SIZE EFFECTS IN THE GROWTH OF AEROSOL NANOPARTICLES AND THEIR COALESCENCE 

Lykov Heat and Mass Transfer Institute, NASB P. Browka 15, 220072 Minsk, Belarus 

SMOLIK, V. ZDIMAL, P. MORAVEC Institute of Chemical Process Fundamentals AS CR Rozvojova 135, 165 02 Prague 6, Czech Republic 

The problems related to an influence of size effects on formation of nanoscale aerosol particles are studied theoretically. Dependence of the trapping coefficient of vapor molecules and the characteristic coalescence time on the particle size is considered. 

Size effects in the particle growth by deposition from the gas phase are related in particular to the Kelvin effect that decreases the saturation pressure near the particle surface with the reduction of the particle size and dependence of the sticking (condensation) coefficient on the particle size. Transfer of vapor molecules to the particle surface in the general case also depends on the particle size through the Knudsen number Kn that is equal to the ratio of the mean free path of gas molecules to the particle radius. Further we consider the free-molecular gas flow when Kn l. The particle growth rate is proportional to the trapping coefficient /i that is defined as the ratio of the resulting flux of vapor molecules into the particle to the flux of vapor molecules incident on the particle 

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