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Experimental investigation of homogeneous nucleation of water in various gases using an expansion chamber
Lukianova, Tetiana ; Lukianov, Mykola ; Hrubý, Jan
Nucleation is an integral part of phase transitions and plays an important role in technology. The control of nucleation in devices such as turbines, rocket and jet engines, wind tunnels, and combustion processes is key to achieving efficient, ecologically sound operation. Our paper presents information about a modernized experimental setup used for homogeneous water nucleation research.\nThe main goal of the study is an analysis of the influence of carrier gas on homogeneous nucleation.The experimental setup based on an expansion chamber has been used for research of homogeneous nucleation over several decades and has undergone various technical improvements. In the Institute of Thermomechanics, the setup was been completely disassembled and cleaned. Pressure transducers, laser, and the data acquisition system have been replaced with modern parts. After that, the chamber was assembled, and thoroughly tested and calibrated.Our investigations were carried with argon and nitrogen as carrier gases in a range of nucleation temperatures 220 – 260 K, pressure range 80-150 kPa, at several concentrations of water vapour. The results thus obtained are consistent with literature data.The findings suggest that this experimental approach is useful for homogeneous water nucleation research.
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The Temperature Dependence of Homogeneous Nucleation Rates by the Gradient Theory
Hrubý, Jan
We demonstrate that the incorrect temperature dependence of the nucleation rates as predicted by the classical nucleation theory is likely a consequence of the ignored dependence of the surface tension on the radius of the droplet parameterized here as a quadratic function of the pressure difference between the gas and liquid phases of the critical cluster. The size-dependent surface tension is obtained using a simplified gradient theory.
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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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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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Měření tlaku sytých par kyseliny sírové – předběžné výsledky
Krejčí, A. Petr ; Ždímal, Vladimír ; Schwarz, Jaroslav ; Hrubý, Jan
Sulphuric acid is crucial component in the initial stage of vapour to liquid transition – nucleation, very important step in environmental and industrial processes, as well as in public health issues. Involved processes are cloud droplet formation, flue gas dew point temperature estimates, as well as increased mortality in highly polluted areas. To model mentioned processes, it is essential to know equilibrium pressures of vapours in concern, sulphuric acid vapour especially.
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Rosný bod spalin: teoretické modelování a předběžné měření
Krejčí, A. Petr ; Hrubý, Jan ; Ždímal, V. ; Trávníček, Zdeněk
Based on industrial needs, the dew point temperature of flue gases is re-examined, both theoretically and experimentally, with mixture of sulphuric acid and water vapors as a flue gas model. This work is motivated by inconsistency and unsufficient accuracy of previous works, which differ significantly in data on sulphuric acid saturation pressure. Experimental setup based on the Laminar co-flow tube is used to express saturation pressure of sulphuric acid via measurements of binary homogeneous nucleation rate.
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