Determination of homogeneous nucleation rates from laminar-flow diffusion chamber data

MADMAcS 1 is a 2D algorithm for the simulation of coupled fluid flow, heat and mass transport, and aerosol dynamics based on the modal aerosol dynamics modelling technique (Whitby, 1989, 1996; Wilck and Stratmann, 1997; Whitby and McMurry, 1997). It is applied to measurements of nucleation of dibutyl phtalate in a laminar flow diffusion chamber presented by Hämeri et al. (1996). A “linear range” is specified inside of which the relation between measured particle number concentrations and nucleation rates is easy and allows the determination of experimental nucleation rates. Based on this approach, a general inversion method for laminar flow diffusion chamber measurements is introduced that is insensitive against many simulation parameters. Moreover, the method can be carried out with simpler models than MADMAcS once the linear range is determined. In a preliminary sensitivity analysis, the thermodynamical properties of the involved substances, particularly the vapor pressure, are shown to be of crucial importance for the reliability of nucleation measurements.