National Repository of Grey Literature 17 records found  1 - 10next  jump to record: Search took 0.01 seconds. 
Thermophysical properties of hydrogen peroxide modeled with the cubic equations of state using software package TREND
Vinš, Václav ; Prokopová, Olga
The research report focuses on modeling of thermophysical properties of hydrogen peroxide intended for use as rocket propellant. Based on the literature review of available data and property correlations, the cubic equations of state by Soave-Redlich-Kwong and Peng-Robinson were developed. The equations were implemented in thermodynamic property package TREND developed at Ruhr University Bochum. Tabulated data for the saturated vapor and liquid and for a set of given isobars were generated. Obtained results will be used as inputs in the CFD simulations of the hydrogen peroxide flows.
Report on the reference densities of water and air employed for the adjustment of vibrating tube density meter
Vinš, Václav ; Prokopová, Olga
Zpráva představuje souhrn několika modelů pro určení referenčních hustot čisté vody a vlhkého vzduchu při atmosférickém tlaku, které jsou potřebné k teplotní kalibraci hustoměru s vibrační trubicí Anton Paar DMA 5000 M. Při nastavení přístroje využívaného v Laboratoři termofyzikálních vlastností vzešla řada technických otázek ohledně kalibrace přístroje. Tato zpráva slouží zejména jako podklad k diskuzi se zástupci společnosti Anton Paar. S použitím softwaru pro technické výpočty Matlab byly vytvořeny programy pro výpočet hustoty vody pomocí stavové rovnice IAPWS-95 od Wagnera a Pruße (2002), CIPM standardu od Tanaky a kol. (2001) a vztahu od Spiewecka a Bettina (1992). Pro vlhký vzduch byl sestaven model na základě IAPWS Guideline G8-10 (2010) založeném na stavové rovnici pro suchý vzduch od Lemmona a kol. (2000) a stavové rovnici pro vodu IAPWS-95. Výsledky byly porovnány s CIPM standardem od Picarda a kol. (2008) a zjednodušeným vztahem od Spiewecka a Bettina (1992). V závěrečné části jsou prezentována data naměřená v Laboratoři termofyzikálních vlastností pro čistou vodu v teplotním rozsahu 2 až 50 °C pro různá nastavení referenčních vztahů pro hustoty vody a vlhkého vzduchu použité při kalibraci přístroje.\n
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
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.
Temperature and pressure correlation for volume of gas hydrates with crystal structures sI and sII.
Vinš, Václav ; Jäger, A. ; Hielscher, S. ; Span, R. ; Hrubý, Jan ; Breitkopf, C.
The temperature and pressure correlations for the volume of gas hydrates forming crystal structures sI and sII developed in previous study [Fluid Phase Equilib. 427 (2016) 268], focused on the modeling of pure gas hydrates relevant in CCS, were revised and modified for the modeling of mixed hydrates in this study. A universal reference state at temperature of 273.15 K and pressure of 1 Pa is used in the new correlation. Coefficients for the thermal expansion together with the reference lattice parameter were simultaneously correlated to both the temperature data and the pressure data for the lattice parameter. The new correlation is in good agreement with the experimental data over wide temperature and pressure ranges from 0 K to 293 K and from 0 to 2000 MPa, respectively. The new correlation provides significantly better agreement with the experimental data for sI hydrates compared to the original correlation. The results of both correlations are comparable in case of sII hydrates.
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.
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.
Molecular Simulations of the Vapor–Liquid Phase Interfaces of Pure Water Modeled with the SPC/E and the TIP4P/2005 Molecular Models
Vinš, Václav ; Celný, David ; Planková, Barbora ; Němec, Tomáš ; Duška, Michal ; Hrubý, Jan
In our previous study [Planková et al., EPJWeb. Conf. 92, 02071 (2015)], several molecular simulations of vapor-liquid phase interfaces for pure water were performed using the DL POLY Classic software. The TIP4P/2005 molecular model was successfully used for the modeling of the density profile and the thickness of phase interfaces together with the temperature dependence of the surface tension. In the current study, the extended simple point charge (SPC/E) model for water together with TIP4P/2005 were employed for the investigation of vapor-liquid phase interfaces over a wide temperature range from 250 K to 600 K. Results of the new simulations are in a good agreement with most of the literature data. TIP4P/2005 provides better results for the saturated liquid density with its maximum close to 275 K, while SPC/E predicts slightly better saturated vapor density. Both models give qualitatively correct representation for the surface tension of water.
Mathematical modeling of planar and spherical vapor–liquid phase interfaces for multicomponent fluids
Celný, David ; Vinš, Václav ; Planková, Barbora ; Hrubý, Jan
Methods for accurate modeling of phase interfaces are important for understanding natural processes and application in technology. In particular, prediction of the non-equilibrium phase transition requires the knowledge of the strongly curved phase interfaces of microscopic droplets. In our work, we focus on the spherical vapor–liquid interfaces for binary mixtures. We developed a computational method able to determine the density and concentration profiles. The fundamentals of our approach lie in the gradient theory, allowing to transcribe the functional formulation into a system of Euler-Langrange equations. System is then modified into a shape suitable for iterative computation. For this task, we employ the Newton-Raphson and the shooting methods ensuring a good convergence speed. For the thermodynamic properties, the PC–SAFT EoS is used. We determined the density and concentration profiles of the binary mixture C O 2 & C 9 H 20 for spherical phase interfaces at various saturation factors.
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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