Experimental Studies of Droplet Evaporation Kinetics: Validation of Models for Binary and Ternary Aqueous Solutions

Abstract

Experiments were conducted with an electrodynamic levitation system to study the kinetics of droplet evaporation under chemically rich conditions. Single solution droplets of known composition (HNO 3 /H 2 O or H 2 SO 4 /HNO 3 /H 2 O) were introduced into an environmentally controlled cubic levitation cell. The gaseous environment was set intentionally out of equilibrium with the droplet properties, thus permitting the HNO 3 mass accommodation coefficient to be determined. Measurements were performed at room temperature and various pressures (200-1000 hPa). Droplet sizes (initial radii in the range 12-26 m) were measured versus time to high precision (Ϯ0.03 m) via Mie scattering and compared with sizes computed by different models for mass and heat transfer in the transition regime. The best agreement between the theoretical calculations and experimental results was obtained for an HNO 3 mass accommodation coefficient of 0.11 Ϯ 0.03 at atmospheric pressure, 0.17 Ϯ 0.05 at 500 hPa, and 0.33 Ϯ 0.08 at 200 hPa. The determination of the mass accommodation coefficient was not sensitive to the transport model used. The results show that droplet evaporation is strongly limited by HNO 3 and occurs in two stages, one characterized by rapid H 2 O mass transfer and the other by HNO 3 mass transfer. The presence of a nonvolatile solute (SO 2Ϫ 4 ) affects the activities of the volatile components (HNO 3 and H 2 O) and prevents complete evaporation of the solution droplets. These findings validate recent attempts to include the effects of soluble trace gases in cloud models, as long as suitable model parameters are used.

Determination of evaporation coefficients of semi-volatile organic aerosols using an integrated volume—tandem differential mobility analysis (IV-TDMA) method

“…a close to 1 was reported for condensation of ammonia onto droplets of 15-65% sulfuric acid solution (Hanson & Kosciuch, 2003). Values around 0.11 were reported for nitric acid condensing to sulfuric acid solutions (Xue, Moyle, Magee, Harrington, & Lamb, 2005). Ammonium nitrate was reported to exhibit a values of 0.5-0.8 in pure form (Dassios & Pandis, 1999) and of 0.25, if coated with dioctyl phthalate (Cruz & Pandis, 2000).…”

Thermodynamic and kinetic behavior of glycerol aerosol

“…The particle trajectory of an evaporating or growing particle through a DMA (Snider et al 2006) is governed by a set of differential equations of the form (Knutson and Whitby 1975;Wilkes 2005;Xue et al 2005):…”

“…Briefly, Z p , E r are taken from Knutson and Whitby (1975) transfer function, u z r ð Þ is the near-parabolic flow profile obtained for viscous, incompressible, laminar flow through a round pipe annulus (Wilkes 2005), m i is taken from Xue et al (2005), applying modeled binary diffusion coefficients (Bird et al 2002; see the SI) and accounting for the mass accommodation effect (Fuchs and Sutugin 1971). Saturation vapor pressure for pure GLY was taken from literature (CHERIC 2015; see the SI).…”

Temperature Dependence of Evaporation Coefficient for Water Measured in Droplets in Nitrogen under Atmospheric Pressure

“…Many attempts have been made over nearly a century, to determine experimentally the values of ␣ C and ␣ T for water, but the results obtained by different authors spanned from ϳ0.001 to 1 for ␣ C and from ϳ0.5 to 1 for ␣ T (see, e.g., Winkler et al 2004;Hagen et al 1989;Zagaynow et al 2000;Sageev et al 1986;Gollub et al 1974;Zou and Fukuta 1999;Shaw and Lamb 1999;Li et al 2001;Xue et al 2005;Marek and Straub 2001;Pruppacher and Klett 1997;Davidovits et al 2004 for reviews). A variety of experimental methods was used.…”