Binary nucleation rates for ethanol/water mixtures in supersonic Laval nozzles

摘要

Although the conditions corresponding to the onset of condensation of aqueous-alcohol mixtures have been measured in supersonic nozzles [B. E. Wyslouzil, J. Chem. Phys. 113, 7317 (2000)], the true nucleation rates have not. Here, we propose a new analytical method to estimate the temperature, the concentrations of condensable species in both the vapor and the liquid phases, and the amount of the condensate using only the measured static pressure profiles in the nozzle. We applied the method to ethanol/water (CH CH _2 OH/ D_2 O or CH CH_2 OD/ D_2 O) mixtures and confirmed that the aerosol volume fractions derived from pressure measurements and small angle neutron scattering measurements are in very good agreement when this method is used. Combining the results from the pressure measurements with the number densities of the condensed droplets, measured either by small angle neutron or small angle x-ray scattering, we determined the first quantitative ethanol/water binary nucleation rates in the supersonic nozzle at a temperature of 229±1 K.