Test of the applicability of Kulmala's analytical expression for the mass flux of growing droplets in highly supersaturated systems: growth of homogeneously nucleated water droplets

Commentary on cloud modelling and the mass accommodation coefficient of water

“…The aerosol size distribution is lognormal, with a geometric mean deviation of 50 nm, geometric standard deviation of 1.7, and number concentration of 3000 cm −3 . The updraft velocity is 1.0 m/s and temperature 273 K. To summarize, comparison with the currently available experimental growth rates indicates that the full coupled FuchsSutugin growth expressions with α=1 are in excellent agreement with experiments at saturation ratios between 1.378 and 12 (Fladerer et al, 2002). Furthermore, the simplified equations presented above, suitable for cloud modelling purposes, give very good results at the lower saturation ratio and are in reasonable agreement with the experiments even at S=12.…”

“…The above expression for the mass flux takes approximately into account the correct droplet temperature due to the latent heat release and under atmospheric conditions the formula very precisely gives the same results as the full coupled equations used by (see also Vesala et al, 1997). Furthermore, Fladerer et al (2002) have shown that the formula is applicable to all growth regimes and to initial conditions of high supersaturation, for which it was not expected to work properly. In their experiments, the supersaturations reached values as high as 1100%, i.e.…”

Modeling of H2O/D2O Condensation in Supersonic Nozzles

“…Because the temperature dependence of the equilibrium vapor pressure has been linearized, this growth law should be restricted to small or moderate supersaturations. Prior modeling studies by Fladerer et al (2002) of micron size droplet growth in a nucleation pulse chamber found, however, that this expression yields satisfactory results for water even when the supersaturation exceeded 10.…”

“…Based on prior theoretical and modeling studies (Wegener et al 1972;Moses and Stein 1978;Kulmala 1990;Peters and Paikert 1994;Fladerer et al 2002), the mass and thermal accommodation coefficients are assumed to be unity for all the growth laws used in our modeling work.…”

“…Finally, other related droplet growth studies, such as those conducted in nucleation pulse chambers or shock tubes (Peters and Paikert 1994;Fladerer et al 2002;Luo et al 2006), only study particle growth long after nucleation is completed. Since these studies rely on visible light scattering, the smallest particles observed, r ∼ 0.5 μm, are much larger than the r ∼ 10 nm droplets formed in supersonic nozzles, and because these droplets were produced by a nucleation pulse that is very short compared to the subsequent growth time, they are essentially monodisperse.…”