Properties Of Fluid Systems Research Articles

Bulk viscosity of water in acoustic modal analysis and experiment

Bulk viscosity is an important factor in the damping properties of fluid systems and exhibits frequency dependent behaviour. A comparison between modal analysis in ANSYS Acoustics, custom code and experimental data is presented in this paper. The measured system consists of closed ended water-filled steel pipes of different lengths. The influence of a pipe wall, flanges on both ends and longitudinal waves in the structural part were included in measurement evaluation. Therefore, the obtained values of sound speed and bulk viscosity are parameters of the fluid. A numerical simulation was carried out only using fluid volume in a range of bulk viscosity. Damping characteristics in this range were compared to measured values. The results show a significant influence of sound speed and subsequently, the use of sound speed value regressed from experimental data yields a better fit between the measurement and the computation.

Fluid-mineral equilibria and thermodynamic mixing properties of fluid systems

The paper presents a review of an experimental method to quantitatively constrain thermodynamic mixing properties of fluid systems at high temperature T and pressure P. The method is based on bracketing equilibrium parameters of simple fluid-mineral reactions. Experimental data obtained with this technique for the H2O-CO2, H2O-N2, and H2O-H2 binary systems were utilized to calculate mixing parameters corresponding to the simplified van Laar model W12VL, according to which the equation for the integral excess Gibbs free energy of a binary mixture Gex is Gex =X1X2W12VL/(X1V10 + X2V20), where Xi is the mole fractions of the components, and Vi0 are pure species molar volumes at given P and T (in cm3). The W12VL for the three mixtures correspond to 202, 219, and 331 kJ cm3/mol. The empirical correlation \(W_{H_2 O - X}^{VL}\) (kJ cm3/mol) = 887.012 QX − 16.674, where Q = Pc (critical pressure, bar)/Tc (critical temperature, K) for gas X (where X = CH4, CO, H2S, O2, Ar, and NH3) is used to evaluate the van Laar parameters for a number of petrologically important water-gas mixtures. The H2O-H2 system is characterized by the greatest positive deviation from the ideal mixing and can thus decompose into two immiscible fluid phases under the P-T parameters typical of deep lithospheric zones. The exsolution of the H2O-CO2 and H2O-N2 systems is expected to occur only under high pressure and low temperature. This combination of parameters may be expected only in the environments of cold subduction. Salts (highly soluble simple salts and/or silicates) should significantly expand the exsolution regions in petrologically important fluids.

Column miniextractors with a vibrating nozzle

Vibrating minicolumns with low and high-frequency drives are suggested for the laboratory investigation of extraction processes. It has been experimentally determined that these apparatuses of up to 1 m in height and 20–50 ml in volume, depending on the physicochemical properties of fluid systems, can provide an efficiency of mass exchange corresponding to 5–10 theoretical steps.

The fifth industrial fluid properties simulation challenge

The fifth industrial fluid properties simulation challenge was held in 2008. In it the contestants were challenged to predict specific, industrially relevant, properties of fluid systems, namely the 1-octanol/water partition coefficient and the infinite-dilution activity coefficient in water of 1-ethylpropylamine and 3-methyl-1-pentanol at specified state conditions. The focus of this challenge was on evaluating methods that could be applied to more difficult liquid–liquid equilibrium problems where a third component is present at a high enough concentration to influence the mutual solubilities of the two main components. Four groups accepted the challenge and used a variety of molecular simulation methods.

The third industrial fluid properties simulation challenge

The third industrial fluid properties simulation challenge was held from March to September 2006. As in the previous two events contestants were challenged to predict specific, industrially relevant, properties of fluid systems. Their efforts were judged based on the agreement of the predicted values with previously unpublished experimental data (provided by researchers at ExxonMobil and DuPont). The focus of this contest was on the transferability of modeling methods—the ability to predict properties for materials that are chemically different, or at different state points, to those used in model parameterization and validation. Nine groups attempted to compute bubble point pressures for mixtures of 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea) and ethanol at 343 K, given data for mixtures at 283 K, and given the pure component vapor pressures. They used a range of different techniques including statistical mechanical and molecular simulations-based approaches. Four of the groups were recognized for providing predictions that were significantly more accurate than would be obtained by extrapolation using the NRTL model (the standard engineering approach). Three groups undertook the more challenging “molecular transferability” problem, attempting to predict shear viscosities at two different state points for a range of diols and triols for which little experimental data was available.

DESCRIPTION OF CRITICAL BEHAVIOUR OF MODEL SYSTEMS USING NON-GAUSSIAN MEASURES (YUKHNOVSKII'S APPROACH)

We present a brief review of the works devoted to a study of critical phenomena in three-dimensional model systems dwelling on the Yukhnovskii approach in detail. This approach which is based on the use of non-Gaussian measures allows one to obtain both universal and non-universal quantities. In order to illustrate the advantages of the approach proposed by I.R.Yukhnovskii we apply it to a study of non-universal quantities, namely: (1) the phase transition temperature of a 3D one-component lattice model, (2) the gas-liquid critical point properties of fluid systems.