Using Small Angle X-ray Scattering to Measure Homogeneous Nucleation Rates of n-propanol in a Supersonic Nozzle
In an earlier publication we presented the results of axial pressure measurements characterizing condensation of a series of n-alcohols (CiH2i+1OH, i = 3–5) in a supersonic nozzle. Although we were able to determine the temperature TJmax, condensible pressure pJmax and characteristic time ΔtJmax, associated with the peak nucleation rate, we could only estimate the nucleation rate Jmax, because we were unable to directly measure the number density N of the aerosol. Here we present the results of our small angle x-ray scattering (SAXS) experiments that characterize n-propanol droplets formed in a comparable supersonic nozzle. By fitting the radially averaged scattering spectrum, we obtain the mean radius ‹r›, the width of the size distribution, and the particle number density N of the aerosol at a fixed position in the nozzle. Finally, by combining the data from both sets of experiments, we find that our measured nucleation rates are about half an order of magnitude higher than the original estimates.
Keywords Homogeneous nucleation, nozzle, n-propanol
KeywordsMass Flow Rate Nucleation Rate Particle Number Density Supersonic Nozzle Advance Photon Source
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