1,473 research outputs found
Vapor–Liquid Equilibria of Nitrogen + Diethyl Ether and Nitrogen + 1,1,1,2,2,4,5,5,5-Nonafluoro-4-(trifluoromethyl)-3-pentanone by Experiment, Peng–Robinson and PC-SAFT Equations of State
The saturated liquid line of the systems nitrogen (N2) + diethyl ether and N2 + 1,1,1,2,2,4,5,5,5-nonafluoro-4-(trifluoromethyl)-3-pentanone (Novec 649) is measured along three isotherms, that is, 390, 420, and 450 K and 360, 390, and 420 K, respectively. The employed gas solubility apparatus, based on the synthetic method, allows to measure points up to the critical region of these mixtures. The experimental data are used to correlate the Peng–Robinson and PC-SAFT equations of state (EOS). For the parametrization of the system, N2 + diethyl ether the Peng–Robinson EOS is combined with the Huron–Vidal mixing rule and the non-random two-liquid (NRTL) excess Gibbs energy model; for the system N2 + Novec 649 the quadratic mixing rule is used
The air pressure effect on the homogeneous nucleation of carbon dioxide by molecular simulation
Vapour-liquid equilibria (VLE) and the influence of an inert carrier gas on
homogeneous vapour to liquid nucleation are investigated by molecular
simulation for quaternary mixtures of carbon dioxide, nitrogen, oxygen, and
argon. Canonical ensemble molecular dynamics simulation using the
Yasuoka-Matsumoto method is applied to nucleation in supersaturated vapours
that contain more carbon dioxide than in the saturated state at the dew line.
Established molecular models are employed that are known to accurately
reproduce the VLE of the pure fluids as well as their binary and ternary
mixtures. On the basis of these models, also the quaternary VLE properties of
the bulk fluid are determined with the Grand Equilibrium method.
Simulation results for the carrier gas influence on the nucleation rate are
compared with the classical nucleation theory (CNT) considering the "pressure
effect" [Phys. Rev. Lett. 101: 125703 (2008)]. It is found that the presence of
air as a carrier gas decreases the nucleation rate only slightly and, in
particular, to a significantly lower extent than predicted by CNT. The
nucleation rate of carbon dioxide is generally underestimated by CNT, leading
to a deviation between one and two orders of magnitude for pure carbon dioxide
in the vicinity of the spinodal line and up to three orders of magnitude in
presence of air as a carrier gas. Furthermore, CNT predicts a temperature
dependence of the nucleation rate in the spinodal limit, which cannot be
confirmed by molecular simulation
Thermodynamic Speed of Sound Data for Liquid and Supercritical Alcohols
Because of their caloric and thermal nature, speed of sound data are vital for the development of fundamental Helmholtz energy equations of state for fluids. The present work reports such data for methanol, 1-propanol, 2-propanol, and 1-butanol along seven isotherms in the temperature range from 220 to 500 K and a pressure of up to 125 MPa. The overall expanded uncertainty varies between 0.07% and 0.11% with a confidence level of 95%. The employed experiment is based on a double path length pulse-echo method with a single piezoelectric quartz crystal of 8 MHz, which is placed between two reflectors at different path lengths. Measured speed of sound data for the four alcohols are fitted with double polynomial equations and compared with literature sources
MolMod – an open access database of force fields for molecular simulations of fluids
The MolMod database is presented, which is openly accessible at http://molmod.boltzmann-zuse.de and contains intermolecular force fields for over 150 pure fluids at present. It was developed and is maintained by the Boltzmann-Zuse Society for Computational Molecular Engineering (BZS). The set of molecular models in the MolMod database provides a coherent framework for molecular simulations of fluids. The molecular models in the MolMod database consist of Lennard-Jones interaction sites, point charges, and point dipoles and quadrupoles, which can be equivalently represented by multiple point charges. The force fields can be exported as input files for the simulation programmes ms2 and ls1 mardyn, GROMACS, and LAMMPS. To characterise the semantics associated with the numerical database content, a force field nomenclature is introduced that can also be used in other contexts in materials modelling at the atomistic and mesoscopic levels. The models of the pure substances that are included in the database were generally optimised such as to yield good representations of experimental data of the vapour–liquid equilibrium with a focus on the vapour pressure and the saturated liquid density. In many cases, the models also yield good predictions of caloric, transport, and interfacial properties of the pure fluids. For all models, references to the original works in which they were developed are provided. The models can be used straightforwardly for predictions of properties of fluid mixtures using established combination rules. Input errors are a major source of errors in simulations. The MolMod database contributes to reducing such errors.BMBF, 01IH16008E, Verbundprojekt: TaLPas - Task-basierte Lastverteilung und Auto-Tuning in der PartikelsimulationEC/H2020/694807/EU/Enrichment of Components at Interfaces and Mass Transfer in Fluid Separation Technologies/ENRICOEC/H2020/760907/EU/Virtual Materials Market Place (VIMMP)/VIMM
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