Simultaneous free-volume modeling of the self-diffusion coefficient and dynamic viscosity at high pressure

International audienceA free-volume model of the dynamic viscosity and the self-diffusion coefficients was discussed. The temperature-pressure variations of the dynamic viscosity and the self-diffusion coefficients of small molecules were predicted. The compounds, carbon tetrachloride, cyclohexane, benzene, chlorotrifluoromethane, tetramethylsilane and methylcyclohexane were used for the investigation. The relation between microstructure, free volume and different complex thermophysical properties were emphasized by the model

Free-volume viscosity model for fluids in the dense and gaseous states

cited By 78International audienceAn approach to model the viscosity of Newtonian fluids is presented. The approach is based on the free-volume concept and on the diffusion models of the molecules. It takes very correctly into account the transition between gas and liquid. The approach emphasizes the relation between microstructure, dynamic viscosity, and free volume in the understanding of such a complex property as dynamic viscosity

Accurate determination of bubble-point of oils from PV data using a combination of Y-function and Tait equation

ACLInternational audienceIn this work, we provide a numerical approach, relying on robust fluid models, to accurately estimate the bubble point of oils from pressure-volume data. The proposed scheme relies on the Tait equation to accurately model the liquid data and on the efficiency on the Y-function to describe the two-phase data. This operator independent scheme has been applied to a set a black-oils and volatile oils of reliable literature experimental data. Results show that the proposed scheme yields bubble-point pressures with deviations of a few psi when compared to experiments. More precisely, we have obtained an average absolute deviation smaller than 0.3% which is one order of magnitude better than usual approaches. © 2016 Elsevier B.V

High-pressure viscosity behavior of x 1,1,1,2-tetrafluoroethane (HFC-134a)+(1-x) triethylene glycol dimethylether (TriEGDME) mixtures: Measurements and modeling

International audienceIn this work new dynamic viscosity measurements for binary mixtures containing a refrigerant (HFC-134a, CF3CH2F) and a lubricant (TriEGDME, CH3O(CH2OCH2)3CH3 ) are reported. The measurements were carried out at temperatures between 293.15 and 373.15 K and pressures from 10 to 100 MPa, for two mole fractions xHFC = 0.3427 and 0.5940 (a total of 100 experimental values). Since lubricants and refrigerants are in two different thermodynamic states at atmospheric pressure and ambient temperature, an especially designed falling-body viscometer has been used to perform the measurements. The data obtained for this binary system have been used to test the ability of several viscosity models having different origins and theoretical backgrounds. The considered models range from simple mixing rules, through empirical correlations, such as the self-referencing model and the LBC model, to recent approaches with a physical and theoretical background, such as the hard-sphere scheme, the free-volume model, and the friction theory

High pressure viscosity and density modeling of two polyethers and two dialkyl carbonates

cited By 29International audienceThis paper reports results concerning the dynamic viscosity η and the density ρ of four pure substances (dimethyl carbonate, diethyl carbonate, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether) as a function of pressure (up to 100 MPa) and temperature (from 283.15 to 353.15 K). All our previously published, Int. J. Thermophy. 22 (2001) 749, experimental values (184 values for viscosity and 410 values for density) have been used in order to test several representative models. The density is discussed with six equations of state (Peng-Robinson, Soave-Redlich-Kwong, Soave-Redlich-Kwong modified, Lee-Kesler, Patel-Teja, and Nishiumi-Saïto) and with the Tait representation. The viscosity is discussed with empirical models, with semi-empirical models such as a self-referencing model and a model based on residual viscosity, and with models with strong physical background such a model based on the hard-sphere scheme, and a free-volume viscosity model. © 2002 Elsevier Science B.V. All rights reserved

Dynamic viscosity modeling of methane plus n-decane and methane plus toluene mixtures: Comparative study of some representative models

International audienceViscosity measurements of well-defined mixtures are useful in order to evaluate existing viscosity models. Recently, an extensive experimental study of the viscosity at pressures up to 140 MPa has been carried out for the binary systems methane + n-decane and methane + toluene, between 293.15 and 373.15 K and for several methane compositions. Although very far from real petroleum fluids, these mixtures are interesting in order to study the potential of extending various models to the simulation of complex fluids with asymmetrical components (light/heavy hydrocarbon). These data (575 data points) have been discussed in the framework of recent representative models (hard sphere scheme, friction theory, and free volume model) and with mixing laws and two empirical models (particularly the LBC model which is commonly used in petroleum engineering, and the self-referencing model). This comparative study shows that the average absolute deviation of the models is between 3.8 and 49.8%, and the maximum deviation is between 11.6 and 78.4%, depending on the considered model