Binary nucleation rates for ethanol/water mixtures in supersonic Laval nozzles: Analyses by the first and second nucleation theorems
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, 140 West 19th Av., Columbus, Ohio 43210 (United States)
We performed pressure trace measurements and small angle x-ray scattering measurements to determine the vapor-liquid nucleation rates of EtOH/H{sub 2}O mixtures including pure EtOH and pure H{sub 2}O in two supersonic Laval nozzles with different expansion rates. The nucleation rates varied from 0.9 × 10{sup 17} to 16 × 10{sup 17} cm{sup −3} s{sup −1} over the temperature range of 210 K to 230 K, EtOH activity range of 0 to 11.6, and H{sub 2}O activity range of 0 to 124. The first and second nucleation theorems were applied to the nucleation rates to estimate the sizes, compositions, and excess energies of the critical clusters. The critical clusters contained from 4 to 15 molecules for pure H{sub 2}O and EtOH/H{sub 2}O clusters, and from 16 to 23 molecules for pure EtOH clusters. Comparing the excess energies of the pure H{sub 2}O critical clusters with the results of a quantum-chemistry calculation suggested that the pre-factor of the theoretical nucleation rate is almost constant regardless of the monomer concentration. One possible explanation for this result is that cooling of the critical clusters limits the nucleation rate under the highly supersaturated conditions. The results of the analyses also yielded the relation between the surface energy and the composition of the critical clusters, where the latter are predicted to consist only of surface molecules. Applying this relationship to the EtOH/H{sub 2}O bulk liquid mixtures, we estimated the EtOH mole fraction in the surface layer and found it is higher than that derived from the surface tension based on the Gibbs adsorption equation when the EtOH mole fraction in the liquid is higher than about 0.2 mol/mol. This discrepancy was attributed to the existence of the EtOH depletion layer just below the surface layer of the liquid.
- OSTI ID:
- 22251544
- Journal Information:
- Journal of Chemical Physics, Vol. 139, Issue 17; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
Similar Records
Nucleation of nanocrystalline diamond by fragmentation of fullerene precursors.
Following heterogeneous nucleation of CO2 on H2O ice nanoparticles with microsecond resolution