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Investigation of droplet nucleation in CCS relevant systems – design and testing of the expansion chamber
Čenský, Miroslav ; Hrubý, Jan ; Vinš, Václav ; Hykl, Jiří ; Šmíd, Bohuslav
A unique in-house designed experimental apparatus for investigation of nucleation of droplets in CCS relevant systems is being developed by the present team. The apparatus allows simulating various processes relevant to CCS technologies. Gaseous mixtures with CO2 are prepared in a Mixture Preparation\nDevice (MPD) based on accurate adjustment of flow rates of individual components [EPJ Web of Conferences 143, 02140 (2017)]. The mixture then flows into an expansion chamber, where it undergoes a rapid adiabatic expansion. As a consequence of adiabatic cooling, the mixture becomes supersaturated and nucleation and simultaneous growth of droplets occurs. In this study, we describe the design and testing of the expansion part of the experimental setup. The rapid expansion was realized using two valve systems, one for low pressures (up to 0.7 MPa) and the other for high pressures (up to 10 MPa). A challenge for a proper design of the expansion system is avoiding acoustic oscillations. These can occur either in the mode of Helmholtz resonator, where the compressible gas in the chamber acts as a spring and the rapidly moving\ngas in the valve system as a mass, or in the “flute” mode, where acoustic waves are generated in a long outlet tubing.\n
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Surface tension of aqueous binary mixtures under the supercooled conditions – Development of the measuring technique and preliminary data for water + lower alcohols
Vinš, Václav ; Hykl, Jiří ; Nikl, Zbyněk ; Čenský, Miroslav ; Hrubý, Jan
An experimental apparatus originally developed for the measurement of surface tension of supercooled water was modified such that it allows for measurement of binary aqueous mixtures. The measuring principle based on the capillary rise technique is similar to that employed in the previous measurements with pure water [J. Hrubý et al., J. Phys. Chem. Lett. 5 (2014) 425 and V. Vinš et al., J. Phys. Chem. B 119 (2015) 5567]. The temperature dependence of the surface tension is determined from the\nmeasured height of the liquid column elevated in a vertical capillary tube with an inner diameter of 0.32 mm. The aqueous liquid rises to a height of 60 mm to 95 mm depending on the solute concentration and the temperature. Preliminary tests performed with the binary mixtures of water with methanol, ethanol, and n-propanol at various concentrations and temperatures down to –28 °C approved functionality of the measuring technique. Some difficulties, such as influence of impurities on the liquid column elevation or formation of bubbles in the liquid column, were observed. The experimental apparatus is further being modified in order to obtain more accurate data for various aqueous mixtures.
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Investigation of droplet nucleation in CCS relevant systems – Design and testing of a CO2 branch of the mixture preparation device.
Vinš, Václav ; Čenský, Miroslav ; Hykl, Jiří ; Hrubý, Jan
A unique in-house designed experimental apparatus for investigation of nucleation of droplets in CCS relevant systems is being developed by our team. The nucleation is measured with the help of a rapid pressure drop within an expansion chamber. In this study, a CO2 branch representing an important part of the mixture preparation device (MPD) was designed, assembled and tested. MPD is intended for preparation of CO2-rich mixtures in a sense of accurate setting of flow rates of individual gaseous components through the experimental section with the expansion chamber. In the CO2 branch, the saturated liquid CO2 is pressurized by a supercritical pump to the pressures of up to 340 bar. The required mass flow of the supercritical CO2 is accurately tuned with a help of a set of stainless steel capillary tubes. Needed lengths of the capillary tubes were determined with a help of a one-dimensional numerical model allowing prediction of both isothermal and adiabatic flow conditions.
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Improvements of the experimental apparatus for measurement of the surface tension of supercooled liquids using horizontal capillary tube
Vinš, Václav ; Hošek, Jan ; Hykl, Jiří ; Hrubý, Jan
An experimental apparatus with a horizontal capillary tube for measurement of the surface tension of supercooled liquids was designed and tested in the previous study [V. Vinš et al., EPJ Web Conf. 92, 02108 (2015)]. In this work, recent modifications of both the experimental setup and the measurement analysis are described. The main aim is to improve the accuracy and the reproducibility of measured surface tension and to achieve higher degrees of supercooling. Among other modifications, the optical setup observing the liquid meniscus at the open end of the horizontal capillary tube together with the video analysis were thoroughly revised. The modified apparatus was used for the measurement of surface tension of supercooled water at temperatures down to – 11 °C. The new data have a lower scatter compared to the previous horizontal measurements and show a good agreement with the other data obtained with a different measurement technique based on the modified capillary rise method.
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An apparatus with a horizontal capillary tube intended for measurement of the surface tension of supercooled liquids
Vinš, Václav ; Hošek, Jan ; Hykl, Jiří ; Hrubý, Jan
New experimental apparatus for measurement of the surface tension of liquids under the metastable supercooled state has been designed and assembled in the study. The measuring technique is similar to the method employed by P.T. Hacker [NACA TN 2510, 1951]. A short liquid thread of the liquid sample was located in a horizontal capillary tube partly placed in a temperature-controlled chamber. One end of the capillary tube was connected to a setup with inert gas which allowed for precise tuning of the gas overpressure. The open end of the capillary tube was precisely grinded and polished in order to assure its planarity and perpendicularity. The liquid meniscus at the open end was illuminated by a laser beam and observed by a digital camera. Application of an increasing overpressure of the inert gas at the inner meniscus of the liquid thread caused variation of the outer meniscus such that it gradually changed from concave to flat and subsequently convex shape. The surface tension at the temperature of the inner meniscus could be evaluated from the overpressure corresponding to exactly planar outer meniscus.
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Atomiser with excitation by a fluidic oscillator
Tesař, Václav ; Hykl, Jiří
Paper summarises results obtained in preliminary feasibility study of a novel pneumatic atomiser for generation o fine droplet spray. The new feature is pulsating the air supply by means of a no-moving-part fluidic oscillator. Tests involved recording by high-speed camera and optical measurements of the droplet size by laser light scattering and suggested a promising future potential necessitating, however, further development and optimisation.
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EXPERIMENTAL APPARATUS FOR MEASUREMENT OF DENSITY OF SUPERCOOLED WATER AT HIGH PRESSURE
Hrubý, Jan ; Hykl, Jiří ; Peukert, Pavel ; Šmíd, Bohuslav
Thermodynamic behavior of supercooled water (metastable fluid water existing transiently below the equilibrium freezing point) at high pressures was subject to many recent theoretical studies. Some of them assume that a second critical point of water exists, related to two liquid phases of supercooled water: the low-density liquid and the high-density liquid. To test these theories, an original experimental cryogenic apparatus is being developed. The volume changes are measured optically in custom-treated fused-silica capillary tubes. The capillaries are placed in a metal vessel designed for pressures up to 200 MPa. The vessel is connected to a circulation thermostat enabling a rapid change of temperature to prevent freezing. A new high-vacuum device was developed for degassing of the ultrapure water sample and filling it into the measuring capillaries. The experiments will contribute to fundamental understanding of the anomalous behavior of water and to applications in meteorology, aerospace engineering, cryobiology etc.
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