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Vliv tlaku nosného plynu na homogenní nukleaci n-alkoholů
Hyvärinen, A-P. ; Wedekind, J. ; Brus, David ; Lihavainen, H.
An overview on the gas pressure effect of nucleation rates of n-alcohols is made. The recent experimental results are compared to the theory introduced by Wedekind et all. The theory is able to predict both the negative and positive pressure effects observed in the experiments, as well as the magnitude of the effect. However, the ratio of carrier gas over vapor pressure has to be shifted by a factor of 0.3-3 for a best match between theory and experiment. This correction factor depends on temperature, vapor pressure of the nucleating vapor, and the carrier gas type.
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Vliv tlaku v jednofázové kondenzaci
Wedekind, J. ; Hyvärinen, A-P. ; Brus, David ; Reguera, D.
The pressure-efect of a chemically inert carrier-gas on the nucleation rate is one of the biggest puzzles in the research of gas-liquid nucleation. Different experiments may show a positive effect a negative effect, or no effect at all, at the same experiment can show both trends for the same substance depending on temperature or for different substances at the same temperature. We show how this ambiguous pressure effect naturally arises from the competition of nonisothermal effects and pressure volume work. We are able to apparently contradictory experimental results and quantify the variation of the nucleation ability in the presence of an ambient gas. Molecular dynamics simulations confirm these predictions very well.
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Homogenní nukleace vody v difúzní komoře s laminárním tokem
Manka, A. ; Brus, David ; Hyvärinen, A.-P. ; Lihavainen, H. ; Wölk, J. ; Strey, R.
Homogeneous nucleation rates of water at temperature between 240 and 270 K were measured in a laminar flow diffusion chamber at ambient pressure and Helium as carrier gas. The experimental results extend the nucleation rate data from literature substantially. Using the macroscopic vapor pressure, density and surface tension of water we calculate the nucleation rates predicted by classic theory and by the empirical correction function of CNT by Völk and Strey. As in the case of other systems, CNT predicts a stronger temperature dependence than experimentally observed, whereas the agreement with empirical correction function is good. Furthermore, the isothermal nucleation rates curves allow us to determine the experimental critical cluster sizes by use of the nucleation theorem. A comparison with the critical cluster sizes calculated by use of the Gibbs-Thomson equation is remarkably good.
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Binární Homogenní Nukleace H2SO4-H2O
Brus, David ; Hyvärinen, A.-P. ; Lihavainen, H. ; Kulmala, M.
In this study binary homogeneous nucleation of sulfuric acid and water was measured in a laminar flow tube. The concentration of sulfuric acid was determined experimentally by employing bubblers along the nucleation chamber and subsequent ion chromatography analysis. The experimental nucleation rates as a function of sulfuric acid concentration at three different relative humidities, as well as comparison with other studies and atmospheric nucleation are presented.
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