Atmospheric Measurement Techniques Discussions www.atmos-meas-tech-discuss.net 1867-8610 2 5 2009 10.5194/amtd-2-2217-2009 http://www.atmos-meas-tech-discuss.net/2/2217/2009/ http://www.atmos-meas-tech-discuss.net/2/2217/2009/amtd-2-2217-2009.html http://www.atmos-meas-tech-discuss.net/2/2217/2009/amtd-2-2217-2009.pdf 2217 2239 2009-09-25 Modelling Ag-particle activation and growth in a TSI WCPC model 3785 F. Stratmann E. Herrmann erik.herrmann@helsinki.fi T. Petäjä M. Kulmala Department of Physics, P.O. Box 64, 00014 University of Helsinki, Finland Leibniz Institute for Tropospheric Research (IfT), Permoserstrasse 15, 04318 Leipzig, Germany In this work, we modelled activation and growth of silver particles in the water-operated TSI model 3785 water condensation particle counter (WCPC). Our objective was to investigate theoretically how various effects influence the counting efficiency of this CPC. Coupled fluid and particle dynamic processes were modelled with the computational fluid dynamics (CFD) code FLUENT in combination with the Fine Particle Model (FPM) to obtain profiles of temperature, vapour concentration, nucleation rate, and particle size. We found that the counting efficiency of the TSI 3785 for small particles might be affected by the presence of larger particles. Moreover, homogeneous nucleation processes can significantly influence counting efficiency. Barrett,~J C. and Clement,~C F.: Growth rates for liquid drops, J. Aerosol Sci., 19, 223–242, 1988. Fletcher,~N H.: Size effect in heterogeneous nucleation, J. Chem. Phys. 29, 572–576, 1958. Fluent: FLUENT 6.2 User's Guide, Fluent Inc., Lebanon NY, USA, 2005. Girshick,~S L., Chiu,~C.-P., and McMurry,~P H.: Time-dependent aerosol models and homogeneous nucleation rates, Aerosol Sci. Technol., 13, 465–477, 1990. Hering,~S V. and Stolzenburg,~M R.: A~method for particle size amplification by water condensation in a~laminar, thermally diffusive flow, Aerosol Sci. Technol., 39, 428–436, 2005. Hering,~S V., Stolzenburg,~M R., Quant,~F R., Oberreit,~D R., and Keady,~P B.: A~laminar-flow, water-based-condensation particle counter (WCPC), Aerosol Sci. Technol., 39, 659–672, 2005. Iida,~K., Stolzenburg,~M R., and McMurry,~P H.: Effect of working fluid on sub-2 \unitnm particle detection with a~laminar flow ultrafine condensation particle counter, Aerosol Sci. Technol. 43, 81–96, 2009. Kürten,~A., Curtius,~J., Nillius,~B., and Borrmann,~S.: Characterization of an automated, water-based expansion condensation nucleus counter for ultrafine particles, Aerosol Sci. Techol. 39, 1174–1183, 2005. Lazaridis,~M., Kulmala,~M., and Laaksonen,~A.: Binary heterogeneous nucleation of a~water-sulphuric acid system: The effect of hydrate interaction, J. Aerosol Sci., 22, 823–830, 1991. Particle dynamics: Fine Particle Model (FPM) for FLUENT, Particle Dynamics GmbH, Leipzig, Germany, 2005, www.particle-dynamics.de. Petäjä,~T., Mordas,~G., Manninen,~H., Aalto,~P P., Hämeri,~K., and Kulmala,~M.: Detection efficiency of a~water-based TSI condensation particle counter 3785, Aerosol Sci. Technol., 40, 1090–1097, 2006. Sgro,~L A. and Fernandez de la Mora,~J.: A~simple turbulent mixing CNC for charged particle detection down to 1.2 \unitnm, Aerosol Sci. Technol. 38, 1–11, 2004. Wagner,~P E., Kaller,~D., Vrtala,~A., Lauri,~A., Kulmala,~M., and Laaksonen,~A.: Nucleation probability in binary heterogeneous nucleation of water-$n$-propanol vapor mixtures on insoluble and soluble nanoparticles, Phys. Rev. E, 67, 021605-[1–12], 2005.