Measurements and simulations of the near-surface composition of evaporating ethanol-water droplets

Christopher J. Homer, Xingmao Jiang, Timothy L. Ward, C. Jeffrey Brinker, Jonathan P. Reid*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

11 Citations (Scopus)

Abstract

The evolving composition of evaporating ethanol-water droplets (initially 32.6 or 45.3 mu m radius) is probed by stimulated Raman scattering over the period 0.2 to 3 ms following droplet generation and with a surrounding nitrogen gas pressure in the range 10 to 100 kPa. The dependence of the evaporation rate on the relative humidity of the surrounding gas phase is also reported. The measured data are compared with both a quasi-steady state model and with numerical simulations of the evaporation process. Results from the numerical simulations are shown to agree closely with the measurements when the stimulated signal is assumed to arise from an outer shell with a probe depth of 2.9 +/- 0.4% of the droplet radius, consistent with a previous determination. Further, the time-dependent measurements are shown to be sensitive to the development of concentration gradients within evaporating droplets. This represents the first direct measurement of the spatial gradients in composition that arise during the evaporation of aerosol droplets and allows the influence of liquid phase diffusion within the condensed phase on droplet evaporation to be examined.

Original languageEnglish
Pages (from-to)7780-7791
Number of pages12
JournalPhysical Chemistry Chemical Physics
Volume11
Issue number36
DOIs
Publication statusPublished - 2009

Keywords

  • LASER-INDUCED FLUORESCENCE
  • DIMENSIONAL STEFAN PROBLEM
  • ENHANCED RAMAN-SCATTERING
  • VAPOR-LIQUID-EQUILIBRIA
  • DIFFUSION-COEFFICIENT
  • TEMPERATURE-GRADIENTS
  • AEROSOL-PARTICLES
  • MOVING BOUNDARY
  • LINEAR STREAM
  • MIXTURES

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