Aerosol Dynamics Modeling With Chemkin-Pro Surface-Kinetics User-Routines

Abstract

The Chemkin-Pro Application Programming Interface (API) was used to implement surface-kinetics user-routines to expand current aerosol dynamics models. Phase change mechanisms were expanded to include homogeneous nucleation in supersaturated environments, and particle size-dependent vapor condensation and evaporation. Homogeneous nucleation of water droplets was modeled with classical nucleation theory (CNT) and a modified form of nucleation theory published by Dillmann, A., and Meier, G. E. A. (1991, “A Refined Droplet Approach to the Problem of Homogeneous Nucleation From the Vapor-Phase,” J. Chem. Phys., 94(5), pp. 3872–3884). The Chemkin-Pro homogeneous nucleation module, developed in this work, was validated against published data for nucleation fluxes at varying pressures, temperatures, and vapor concentrations. A newly released feature in Chemkin-Pro enabled particle size-dependent surface reaction rates. A Chemkin-Pro vapor condensation and evaporation module was written and verified with the formulation published in Hinds, W. C. (1999, Aerosol Technology: Properties, Behavior, and Measurement of Airborne Particles, Wiley, New York). Lastly, Chemkin-Pro results for coagulation in the transition regime were verified with the semi-implicit method developed by Jacobson, M. Z. (1999, Fundamentals of Atmospheric Modeling, Cambridge University Press, New York, NY). Good performance was observed for all three Chemkin-Pro modules. This work illustrates the utility of the Chemkin-Pro API, and the flexibility with which models can be developed using surface-kinetics user-routines. This paper illustrates that Chemkin-Pro can be developed to include more physically representative aerosol dynamics processes where rates are defined based on physical and chemical parameters rather than Arrhenius rates. The methods and modules developed in this work can be applied to industrial problems like material synthesis (e.g., powder production), processes involving phase change like heat exchangers, as well as more fundamental scientific processes like cloud physics.