Viscosities and Densities of Binary Mixtures of Hexadecane with Dissolved Methane or Carbon Dioxide at Temperatures from (298 to 473) K and at Pressures up to 120 MPa

We report measurements of the viscosity and density of two binary mixtures comprising hexadecane with dissolved carbon dioxide or methane over the temperature range from (298.15 to 473.15) K and at pressures up to 120 MPa. The measurements were conducted at various mole fractions <i>x</i> of the light component as follows: <i>x</i> = (0, 0.0690, 0.5877, and 0.7270) for <i>x</i>CO₂ + (1 – <i>x</i>)­C₁₆H₃₄ and <i>x</i> = (0, 0.1013, 0.2021, 0.2976, and 0.3979) for <i>x</i>CH₄ + (1 – <i>x</i>)­C₁₆H₃₄. The viscosity and density measurements were carried out simultaneously using a bespoke vibrating-wire apparatus with a suspended sinker. With respect to the first mixture, the apparatus was operated in a relative mode and was calibrated in octane whereas, for the second mixture, the apparatus was operated in an absolute mode. To facilitate this mode of operation, the diameter of the centerless-ground tungsten wire was measured with a laser micrometer, and the mass and volume of the sinker were measured independently by hydrostatic weighing. In either mode of operation, the expanded relative uncertainties at 95% confidence were 2% for viscosity and 0.3% for density. The results were correlated using simple relations that express both density and viscosity as functions of temperature and pressure. For both pure hexadecane and each individual mixture, the results have been correlated using the modified Tait equation for density, and the Tait–Andrade equation for viscosity; both correlations described our data almost to within their estimated uncertainties. In an attempt to model the viscosity of the binary mixtures as a function of temperature, density, and composition, we have applied the extended-hard-sphere model using several mixing rules for the characteristic molar core volume. The most favorable mixing rule was found to be one based on a mole-fraction-weighted sum of the pure component molar core volumes raised to a power γ which was treated as an adjustable parameter. In this case, deviations of the experimental viscosities from the model were within ±25%

Densities of Aqueous MgCl₂(aq), CaCl₂(aq), KI(aq), NaCl(aq), KCl(aq), AlCl₃(aq), and (0.964 NaCl + 0.136 KCl)(aq) at Temperatures Between (283 and 472) K, Pressures up to 68.5 MPa, and Molalities up to 6 mol·kg^–1

We report the densities of MgCl₂(aq), CaCl₂(aq), KI­(aq), NaCl­(aq), KCl­(aq), AlCl₃(aq), and the mixed salt system [(1 – <i>x</i>)­NaCl + <i>x</i>KCl]­(aq), where <i>x</i> denotes the mole fraction of KCl, at temperatures between (283 and 472) K and pressures up to 68.5 MPa. The molalities at which the solutions were studied were (1.00, 3.00, and 5.00) mol·kg^–1 for MgCl₂(aq), (1.00, 3.00, and 6.00) mol·kg^–1 for CaCl₂(aq), (0.67, 0.90, and 1.06) mol·kg^–1 for KI­(aq), (1.06, 3.16, and 6.00) mol·kg^–1 for NaCl­(aq), (1.06, 3.15, and 4.49) mol·kg^–1 for KCl­(aq), (1.00 and 2.00) mol·kg^–1 for AlCl₃(aq), and (1.05, 1.98, 3.15, and 4.95) mol·kg^–1 for [(1 – <i>x</i>)­NaCl + <i>x</i>KCl]­(aq), with <i>x</i> = 0.136. The measurements were performed with a vibrating-tube densimeter calibrated under vacuum and with pure water over the full ranges of pressure and temperature investigated. An analysis of uncertainties shows that the relative uncertainty of density varies from 0.03 % to 0.05 % depending upon the salt and the molality of the solution. An empirical correlation is reported that represents the density for each brine system as a function of temperature, pressure, and molality with absolute average relative deviations of approximately 0.02 %. Comparing the model with a large database of results from the literature, we find absolute average relative deviations of 0.03 %, 0.06 %, 0.04 %, 0.02 %, and 0.02 % for the systems MgCl₂(aq), CaCl₂(aq), KI­(aq), NaCl­(aq), and KCl­(aq), respectively. The model can be used to calculate density, apparent molar volume, and isothermal compressibility over the full ranges of temperature, pressure, and molality studied in this work. An ideal mixing rule for the density of a mixed electrolyte solution was tested against our mixed salt data and was found to offer good predictions at all conditions studied with an absolute average relative deviation of 0.05 %

Composition Analysis and Viscosity Prediction of Complex Fuel Mixtures Using a Molecular-Based Approach

The automobile industry currently faces the challenge of developing a new generation of diesel motor engines that satisfy both increasingly stringent emission regulations and reduces specific fuel consumption. The performance of diesel engines, seen in terms of emissions and specific fuel consumption, generally improves with increasing fuel-injection pressure. The design of the next generation of diesel fuel injection systems requires the knowledge of the thermophysical properties, in particular viscosity, of a wide-type of diesel fuels at pressures up to 300 MPa or more. The objective of the present work is to demonstrate that it is possible to predict the viscosity of any petroleum-based diesel fuel, using, exclusively, its molar fraction distribution as provided by multidimensional gas chromatography techniques. The precise knowledge of the fuel chemical constituents allows the understanding of the influence of the different hydrocarbon families on the fluid viscosity by means of molecular dynamics simulations. The accuracy of the Anisotropic United Atom force-field was tested and was found to be in agreement with experimental viscosities obtained with a new vibrating wire device at different temperatures and pressures up to 300 MPa. Finally, the experimental and simulated viscosities have been compared with improved group contribution method that has been coupled with gas chromatography experimental measurements for a viscosity prediction that was estimated to be of less than 18% of mean absolute deviation