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Mengxin Lu - One of the best experts on this subject based on the ideXlab platform.

  • a Helmholtz Free Energy equation of state for the nh3 h2o fluid mixture correlation of the pvtx and vapor liquid phase equilibrium properties
    Fluid Phase Equilibria, 2015
    Co-Authors: Jun Deng, Mengxin Lu
    Abstract:

    Abstract An equation of state (EOS) explicit in Helmholtz Free Energy was developed to calculate the PVTx and vapor–liquid phase equilibrium properties of the NH3–H2O fluid mixture. This EOS, where four mixing parameters are used, is based on highly accurate EOSs for the pure components (H2O and NH3) that NIST recommends and contains a simple generalized departure function presented by Lemmon and Jacobsen (1999) [38] . Comparison with thousands of reliable experimental data available indicates that the EOS can calculate both vapor–liquid phase equilibrium and volumetric properties of this binary fluid system, within or close to experimental uncertainties up to 706 K and 2000 bar over all composition range. The average absolute deviation is 0.68% in molar volume, and the average composition error of vapor phase and that of liquid phase except for those at the near-critical region are in general less than 0.03 and 0.07 in mole fraction, respectively.

  • A Helmholtz Free Energy equation of state for the NH3–H2O fluid mixture: Correlation of the PVTx and vapor–liquid phase equilibrium properties
    Fluid Phase Equilibria, 2015
    Co-Authors: Jun Deng, Mengxin Lu
    Abstract:

    Abstract An equation of state (EOS) explicit in Helmholtz Free Energy was developed to calculate the PVTx and vapor–liquid phase equilibrium properties of the NH3–H2O fluid mixture. This EOS, where four mixing parameters are used, is based on highly accurate EOSs for the pure components (H2O and NH3) that NIST recommends and contains a simple generalized departure function presented by Lemmon and Jacobsen (1999) [38] . Comparison with thousands of reliable experimental data available indicates that the EOS can calculate both vapor–liquid phase equilibrium and volumetric properties of this binary fluid system, within or close to experimental uncertainties up to 706 K and 2000 bar over all composition range. The average absolute deviation is 0.68% in molar volume, and the average composition error of vapor phase and that of liquid phase except for those at the near-critical region are in general less than 0.03 and 0.07 in mole fraction, respectively.

Jun Deng - One of the best experts on this subject based on the ideXlab platform.

  • a Helmholtz Free Energy equation of state for the nh3 h2o fluid mixture correlation of the pvtx and vapor liquid phase equilibrium properties
    Fluid Phase Equilibria, 2015
    Co-Authors: Jun Deng, Mengxin Lu
    Abstract:

    Abstract An equation of state (EOS) explicit in Helmholtz Free Energy was developed to calculate the PVTx and vapor–liquid phase equilibrium properties of the NH3–H2O fluid mixture. This EOS, where four mixing parameters are used, is based on highly accurate EOSs for the pure components (H2O and NH3) that NIST recommends and contains a simple generalized departure function presented by Lemmon and Jacobsen (1999) [38] . Comparison with thousands of reliable experimental data available indicates that the EOS can calculate both vapor–liquid phase equilibrium and volumetric properties of this binary fluid system, within or close to experimental uncertainties up to 706 K and 2000 bar over all composition range. The average absolute deviation is 0.68% in molar volume, and the average composition error of vapor phase and that of liquid phase except for those at the near-critical region are in general less than 0.03 and 0.07 in mole fraction, respectively.

  • A Helmholtz Free Energy equation of state for the NH3–H2O fluid mixture: Correlation of the PVTx and vapor–liquid phase equilibrium properties
    Fluid Phase Equilibria, 2015
    Co-Authors: Jun Deng, Mengxin Lu
    Abstract:

    Abstract An equation of state (EOS) explicit in Helmholtz Free Energy was developed to calculate the PVTx and vapor–liquid phase equilibrium properties of the NH3–H2O fluid mixture. This EOS, where four mixing parameters are used, is based on highly accurate EOSs for the pure components (H2O and NH3) that NIST recommends and contains a simple generalized departure function presented by Lemmon and Jacobsen (1999) [38] . Comparison with thousands of reliable experimental data available indicates that the EOS can calculate both vapor–liquid phase equilibrium and volumetric properties of this binary fluid system, within or close to experimental uncertainties up to 706 K and 2000 bar over all composition range. The average absolute deviation is 0.68% in molar volume, and the average composition error of vapor phase and that of liquid phase except for those at the near-critical region are in general less than 0.03 and 0.07 in mole fraction, respectively.

A V Zakharov - One of the best experts on this subject based on the ideXlab platform.

  • transition Helmholtz Free Energy entropy and heat capacity of Free standing smectic films in water a mean field treatment
    Journal of Chemical Physics, 2014
    Co-Authors: Izabela śliwa, A V Zakharov
    Abstract:

    Using the extended McMillan's mean field approach with anisotropic forces a study of both the structural and thermodynamic properties of Free-standing smectic film (FSSF) in water on heating to the isotropic temperature is carried out numerically. By solving the self-consistent nonlinear equations for the order parameters, we obtained that the smectic-A-isotropic (AI) transition occurs through the series of layer-thinning transitions causing the films to thin in the stepwise manner as the temperature is increased above the bulk smectic-A-isotropic temperature TAI(bulk). With enhanced pair interactions in the bounding layers, the smectic-isotropic transition corresponds to smectic melting of the central layers. The effects of surface “enhanced” pair interactions in the bounding layers and of film thickness on the orientational and translational order parameters, the Helmholtz Free Energy and entropy, as well as the temperature dependence of the heat capacity of FSSFs, have also been investigated. Reasonabl...

  • transition entropy Helmholtz Free Energy and heat capacity of Free standing smectic films above the bulk smectic a isotropic transition temperature a mean field treatment
    Physical Review E, 2010
    Co-Authors: A V Zakharov, D E Sullivan
    Abstract:

    We have carried out a numerical study of both the structural and thermodynamic properties of Free-standing smectic films (FSSFs) for two cases of enhanced pair interactions in the bounding layers. Calculations, based upon the extended McMillan's approach with anisotropic forces, shows a stepwise reduction of the value of the heat capacity as the temperature is raised above the bulk smectic A-isotropic transition. The effects of surface "enhanced" pair interactions in the bounding layers and of film thickness on the orientational and translational order parameters, the Helmholtz Free Energy, and entropy of FSSFs have also been investigated. Reasonable agreement between the theoretically predicted and the experimentally obtained—by means of calorimetric techniques-data on the heat capacity of the partially fluorinated 5-n-alkyl-2-(4-n-(perfluoroalkyl-metheleneoxy)phenyl) (H10F5MOPP) films has been obtained.

Limei He - One of the best experts on this subject based on the ideXlab platform.

  • data for a Helmholtz Free Energy equation of state for the vapor liquid equilibrium and pvtx properties of the h2s h2o mixture and its application to the h2s h2o nacl system
    Applied Geochemistry, 2019
    Co-Authors: Chuanrong Peng, Jiawen Hu, Limei He
    Abstract:

    Abstract An equation of state (EOS) explicit in Helmholtz Free Energy has been developed to calculate the vapor-liquid equilibrium (VLE) and pressure-volume-temperature-composition (PVTx) properties of the H2S H2O fluid mixture. This EOS, where five mixing parameters are used, is based on the highly accurate EOSs of pure H2S and H2O fluids, and contains a simple departure function. Compared to reliable experimental data available, the average absolute deviations of H2S solubility in liquid phase, water content in vapor phase, and liquid density of the H2S H2O system are 3.88%, 5.03% and 0.20%, respectively. The EOS of the H2S H2O fluid mixture, together with the Pitzer activity coefficient of H2S in aqueous NaCl solution from previous study, can be used to predict the H2S solubility in aqueous NaCl solution with an average absolute deviation of 7.52%. The water content of vapor phase in the H2S H2O NaCl system can be reproduced with the fluid EOS of H2S H2O system by a fugacity-activity method within experimental uncertainties. The fluid EOS of H2S H2O system, combined with the Helmholtz Free Energy EOS of H2O NaCl fluid mixture, can predict the PVTx properties of the H2S H2O NaCl mixture without using additional mixing parameters. The developed EOS can be safely used under the conditions of CO2 capture and sequestration (273–473 K, 0–400 bar and 0–6 mol kg−1), beyond which the EOS also has some extrapolated ability. The computer codes are in the supplemental data and can be downloaded from Applied Geochemistry or obtained from the corresponding author.

D Nicholson - One of the best experts on this subject based on the ideXlab platform.

  • molecular simulation of volume of mixing Helmholtz Free Energy of mixing and entropy of mixing in bulk fluid mixtures
    Molecular Simulation, 2018
    Co-Authors: D D Do, D Nicholson
    Abstract:

    We describe a kinetic Monte Carlo molecular simulation procedure to calculate the Helmholtz Free Energy, the entropy and the chemical potentials of all components in a bulk fluid mixture. This allows us to derive the excess properties (volume, Free Energy and entropy) resulting from the mixing of homogeneous fluids of pure components at constant temperature and pressure. We have chosen neon–xenon mixtures to illustrate our method because of the large difference in collision diameter and well-depth of the interaction Energy. When xenon is predominant in the mixture, the volume of mixing is larger. The excess entropy of mixing correlates with the volume of mixing, since a positive excess volume enables more configurations (more possible molecular distributions). The excess thermodynamic quantities as functions of the total density were found to be insensitive to temperature. To investigate the effects of the molecular parameters, we also studied argon–nitrogen and argon–krypton mixtures. The effect of the difference in molecular parameters is in the order: argon–nitrogen < argon–krypton < neon–xenon. A large difference in the well-depth of the interaction energies results in an increase in the excess thermodynamic variables, which is in agreement with the literature McDonald IR. NpT-ensemble Monte Carlo calculations for binary liquid mixtures.

  • an efficient kinetic monte carlo scheme for computing Helmholtz Free Energy and entropy in bulk fluids and adsorption systems
    Chemical Engineering Journal, 2018
    Co-Authors: D D Do, D Nicholson
    Abstract:

    Abstract We present an efficient kinetic Monte Carlo scheme to determine the Helmholtz Free Energy and entropy of bulk fluids and adsorption systems. The method is made possible because this technique enables the accurate determination of the chemical potential. The Helmholtz Free Energy, A, is obtained by integrating the chemical potential with respect to the number of molecules, at constant volume and temperature, and the entropy is then determined from the fundamental thermodynamic equation A = E − TS. The entropy of bulk argon is found to be in excellent agreement with values calculated from the established equation of state (EOS). In a system with two co-existing phases we show that our method can determine the surface tension at the Gibbs dividing surface, without recourse to the mechanical route of Irving, Kirkwood and Buff. We show that the intrinsic integral molecular Helmholtz Free Energy and entropy of the adsorbed phase, corrected for the surface excess, are independent of the size of the simulation box for all chemical potentials tested. The new procedure is illustrated for a range of gases commonly used in the characterization of porous solids (argon, nitrogen, carbon dioxide and ammonia) as adsorbates and a graphitic slit pore as the model adsorbent.

  • chemical potential Helmholtz Free Energy and entropy of argon with kinetic monte carlo simulation
    Molecular Physics, 2014
    Co-Authors: D D Do, D Nicholson, E Ustinov
    Abstract:

    We present a method based on kinetic Monte Carlo (kMC) to determine the chemical potential, Helmholtz Free Energy and entropy of a fluid within the course of a simulation. The procedure requires no recourse to auxiliary methods to determine the chemical potential, such as the implementation of a Widom scheme in Metropolis Monte Carlo simulations, as it is determined within the course of the simulation. The equation for chemical potential is proved, for the first time in the literature, to have a direct connection with inverse Widom potential theory in using real molecules rather than ghost molecules. We illustrate this new procedure by several examples, including fluid argon and adsorption of argon as a non-uniform fluid on a graphite surface and in slit pores.