Code for simulating the effect of dilution on particle mass
Inputs Environmental Variables Temperature, pressure, time to solve over, molecular weight dry air Bulk Particle Properties Radius, number concentration VBS Properties Molecular weight, density, saturation vapour pressure, gas-phase concentration, mass fractions in particle phase, accommodation coefficient
Pre-time loop calculations Gas-phase diffusion coefficient The diffusion coefficient is a function of temperature, pressure, molecular weight of the partitioning component and air, and particle size. It needs a correction applied when the aerosol is not in the continuum regime. Corrected concentration above particle surface The saturation concentration is found and then it is corrected for the curvature (Kelvin) effect and solute (Raoult) effect.
Time Loop Estimate of concentration change based on difference between bulk vapour-phase concentration and concentration above particle surface, following Ficks first law (eq. 3 of Zaveri et al. 2008). This is the governing equation for partitioning.
The code includes an option to use the partitioning equation with the effect of partitioning on particle radius through the mass transfer rate and the curvature effect accounted for. There is also an option where the effect of partitioning on radius is presumed to be relatively small and so mass transfer rate and curvature effects are assumed constant.
Output Mass fraction remaining in particle phase