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We report new interfacial tension (IFT) measurements of the (H2O + CO2 + H2) and (H2O + H2) systems at pressures of (0.5 to 45) MPa, and temperatures of (298.15 to 448.15) K, measured by the pendant-drop method. The expanded uncertainties at 95% confidence are 0.05 K for temperature, 70 kPa for pressure, 0.017·γ for IFT in the both the binary (H2O + H2) system and the ternary (CO2 + H2 + H2O) system. Generally, the IFT was found to decrease with both increasing pressure and increasing temperature. However, for (H2O + H2) at the lowest two temperatures investigated, the isothermal IFT data were found to exhibit a maximum as a function of pressure at low pressures before declining with increasing pressure. An empirical correlation has been developed for the IFT of the (H2O + H2) system in the full range of conditions investigated, with an average absolute deviation of 0.16 mN m−1, and this is used to facilitate a comparison with literature values. Estimates of the IFT of the (H2O + CO2 + H2) ternary system, by an empirical combining rule based on the coexisting phase compositions and the interfacial tensions of the binary systems, were found to be unsuitable at low temperatures, with an average absolute deviation of 3.6 mN m−1 over all the conditions investigated.

In this paper, we present density and speed-of-sound experimental measurements for n-nonane at temperatures between (283.15 and 473.15) K and pressures up to 68 MPa and 390 MPa respectively. The density measurements were performed with a vibrating-tube densimeter and the speed-of-sound measurements were carried out in a dual-path pulse-echo apparatus. The vibrating-tube densimeter was calibrated using pure helium and water over the full range of temperature and pressure investigated, while the speed-of-sound apparatus was calibrated using pure water at low pressure over the full range of temperature. The expanded relative uncertainties of the measurements were 0.08% for density and between (0.1 and 0.3)% for sound speed at 95% confidence. The density data were correlated with the modified Tait equation over the entire temperature and pressure range, with an absolute average relative deviation of 0.006%. An empirical equation was developed to represent the sound speed data with an absolute average relative deviation of 0.03%. Both sets of data were compared with the predictions from the equation of state developed by Lemmon and Span. Comparisons have also been made with the available literature and satisfactory agreement was found. Correlations were developed for the density and isobaric heat capacity of the liquid as functions of temperature at a reference pressure of 0.1 MPa, the latter based on literature data. Combining these correlations with the sound-speed surface, properties of the liquid were computed by thermodynamic integration up to a pressure of 390 MPa. Density, isobaric heat capacity, isothermal compressibility and isobaric expansivity values are reported, and their uncertainties were carefully investigated.

We studied shock-darkening in ordinary chondrites by observing the propagation of shock waves and melting through mixtures of silicates, metals and iron sulfides. We used the shock physics code iSALE at the mesoscale to simulate shock compression of modeled ordinary chondrites (using olivine, iron and troilite). We introduced FeS-FeNi eutectic properties and partial melting in a series of chosen configurations of iron and troilite grains mixtures in a sample plate. We observed, at a nominal pressure of 45 GPa, partial melting of troilite in all models. Only few of the models showed partial melting of iron (a phase difficult to melt in shock heating) due to the eutectic properties of the mixtures. Iron melting only occurred in models presenting either strong shock wave concentration effects or effects of heating by pore crushing, for which we provided more details. Further effects are discussed such as the frictional heating between iron and troilite and the heat diffusion in scenarios with strongly heated troilite. We also characterized troilite melting in the 32–60 GPa nominal pressure range. We concluded that specific dispositions of iron and troilite grains in mixtures allow for melting of iron and explain why it is possible to find a wide textural variety of melted and unmelted metal and iron sulfide grains in shock-darkened ordinary chondrites. We finally observe shock-melting of albite within a few iron and troilite grain models, and investigate the effects of higher porosity within the olivine matrix in the single iron and troilite grain models.

In recent years, computational fluid dynamics (CFD) has been applied for the design and analysis of positive displacement machines (both compressors and expanders) with numerous challenges due to the dynamics of the compression (or expansion) process and deforming working chambers. The relative motion and in turn, the variation of the gaps during machine operation implies several obstacles for the implementation of reliable CFD models. The majority of the studies reported in literature focused on scroll, twin screw and reciprocating machines. The limitation of the developed methodologies to be applied directly to positive displacement machines with more complex meshing such as that of single-screw has been highlighted in literature. In this paper, a single screw expander is studied by means of (i) a moving mesh technique (dynamic mesh in the Key Frame Remeshing approach) and (ii) a real gas model of a R134a (Peng-Robinson model) implemented in OpenFOAM. On the top of that, all the possible techniques that come with the software are investigated in their application to single screw. An useful review of the state of the art CFD with open-source software (OpenFOAM-v1606+ and foam-extend4.0) is therefore carried out. The reliability of CFD model represents indeed the first step on which the design process and further optimization will be based. (C) 2017 The Authors. Published by Elsevier Ltd.

The methodologies generally adopted for synthesis of methane hydrates (e.g., the dissolved gas method, excess gas method and the ice seeding method) signifies the importance of appropriate thermodynamic conditions for the dissolution characteristics of methane in water and its subsequent crystallization to form hydrates. The 'dissolved gas method' and 'excess gas method', which mimics the natural formation and existence of methane hydrates beneath ocean bed, can be employed for controlled synthesis of hydrates by regulating the pressure and temperature. However, explicit research has not yet been conducted to understand the rate of temperature decrease in methane dissolution characteristics, prior to gas hydrate formation. At a definite pressure-temperature condition, the dissolution characteristics are largely dependent on the 'interaction time', or 'contact time', available for methane gas to dissolute in water. Therefore, an investigation was conducted to (i) ascertain the rate of hydrate formation, (ii) quantify the volume of gas hydrates formed, corresponding to different combinations of pressure and temperature, and (iii) to understand the impact of memory effect, in a closed cell. This study demonstrates that though the stability of gas hydrates is principally dependent on the pressure and temperature combinations, sufficient interaction time should be provided for their stable occurrence. Moreover, it was also proven that the relevance of memory effect was predominant after the fifth run of hydrate formation-dissociation cycle. (C) 2017 Elsevier B.V. All rights reserved.

The prediction of the solubility of active pharmaceutical ingredients (APIs) is a significant challenge which is of importance in pharmaceutical applications and solvent selection. Here, we extend the table of group interactions (3 like interactions, 47 unlike interactions) of the SAFT- γ Mie group-contribution equation of state to model the phase behaviour and solubility of mefenamic acid, a nonsteroidal anti-inflammatory drug, in a range of solvents. In addition to mefenamic acid, we also consider its molecular synthons: benzoic acid and diphenylamine. New experimental solubility data are presented for the three molecules in a range of solvents, and three new SAFT- γ Mie functional groups are defined (aCCOOH, aCNHaC and CH 3 CO) and characterised, together with their interactions with solvent groups. Literature data for the vapour pressure, single-phase density, saturation density, vapourisation enthalpy, bubble temperature, dew temperature, and bubble pressure are used to characterise the new group interactions. Solubility data are used to characterise the new group-group interactions only if there are no other experimental data available. The transferability and predictive accuracy of the new models are assessed by comparing the theoretical predictions with the experimental solubility data. Our comparison includes alcohols, ketones, and esters as families of solvents and mixed-solvent solubility predictions.

For both ethical and practical reasons accurate tissue simulant materials are essential for ballistic testing applications. A wide variety of different materials have been previously adopted for such roles, ranging from gelatin to ballistics soap. However, while often well characterised quasi-statically, there is typically a paucity of information on the high strain-rate response of such materials in the literature. Here, building on previous studies by the authors on other tissue analogues, equation-of-state data for the elastomeric epithelial/muscular simulant material Perma-Gel ® is presented, along with results from a series of ballistic tests designed to illustrate its impact-related behaviour. Comparison of both hydrodynamic and ballistic behaviour to that of comparable epithelial tissues/analogues (Sylgard ® and porcine muscle tissue) has provided an insight into the applicability of both Perma-Gel ® and, more generally, monolithic simulants for ballistic testing purposes. Of particular note was an apparent link between the high strain-rate compressibility (evidenced in the Hugoniot relationship in the U s -u p plane) and subsequent ballistic response of these materials. Overall, work conducted in this study highlighted the importance of fully characterising tissue analogues – with particular emphasis on the requirement to understand the behaviour of such analogues under impact as part of a system as well as individually.

This work focuses on the extension of the successful COSMO-RS model of mixtures into an equation-of-state model of fluids and its application for the estimation of solvation/hydration quantities of a variety of chemical substances. These quantities include free-energies, enthalpies and entropies of hydration as well as the separate contributions to each of them. Emphasis is given on the estimation of contributions from the conformational changes of solutes upon solvation and the associated restructuring of solvent in its immediate neighborhood. COSMO-RS is a quantum-mechanics based group/segment contribution model in which the Quasi-Chemical (QC) approach is used for the description of the non-random distribution of interacting segments in the system. Thus, the equation-of-state development is done through such a QC framework. The new model will not need any adjustable parameters for the strong specific interactions, such as hydrogen bonds, since they will be provided by the quantum-mechanics based cosmo-files - a key feature of COSMO-RS model. It will need, however, one volumetric and one energy parameter per fluid, which are scaling constants or molecular descriptors of the fluid and are obtained from rather easily available data such as densities, boiling points, vapor pressures, heats of vaporization or second virial coefficients. The performance and the potential of the new equation-of-state model to become a fully predictive model are critically discussed. (C) 2015 Elsevier Ltd. All rights reserved.

Ionic liquids (ILs) are an exciting class of compounds of high interest from a technological point of view. One of the applications that is raising more interest is their possible use as solvents to carry out the conversion of CO2 into more valuable compounds. Theoretical approaches provide an attractive option to screen ILs properties and give quick answers to guide the experiments, becoming a crucial tool for process design. This work illustrates a practical example based on the solubility of greenhouse and acid gases on the butylmethylimidazolium methylsulfate [C(4)mim][MeSO4] IL, in order to study its feasibility for gas separation and conversion. A simple but reliable molecular model is presented for the ionic liquid based on structural information and molecular simulations, and coarse-grained models are used to model the different gases. The absorption of relevant gases for the separation/conversion process (CO2, CH4, CO, H-2, SO2, H2S) in [C(4)mim][MeSO4] is modeled and compared with experimental data using a minimum amount of binary data. From this information, the ternary diagrams of [C(4)mim][MeSO4] with CO2 and the acid gases SO2 and H2S are predicted, and the selectivity of CO2 by respect all the gases is evaluated, with particular attention to the contaminants above mentioned. (C) 2015 Elsevier B.V. All rights reserved.

The capabilities of the soft-SAFT EoS to accurately describe the thermophysical properties of ionic liquids (ILs) and the phase equilibria of their mixtures with greenhouse gases is extended in this work to address the CO2 and the N2O solubilities in [C(4)mim](+) ILs from different anion families. In addition to the commonly studied [BF4](-) and [NTf2](-) anions, the solubility of these gases in ILs with the anions [N(CN)(2)](-), [SCN](-) and [Ac](-) is also studied and compared among them, searching for the best system for separation purposes. A coarse-grained molecular model is proposed within the soft-SAFT framework for each newly studied IL based on structural information, guidance obtained from quantum calculations and previous work. The most adequate set of molecular parameters are selected from the ILs density description and from the ability to reproduce the N2O/CO2 solubilities in these ILs at the lowest and highest temperatures for which experimental data are available. A discussion about the association molecular parameters values and their relation with the anion nature is also presented. With these molecular models, the description of the high pressure phase equilibria of the binary systems composed of the two gases and the ILs referred above are described with soft-SAFT for the remaining isotherms. For most systems, the equilibria behavior of the mixtures is predicted without using any binary parameter. When good agreement with the experimental data is not achieved, a single temperature independent binary parameter is enough to allow a good description. Finally, Henry's law constants are calculated from soft-SAFT to evaluate the selectivity of those ILs for the CO2/N2O separation. (C) 2014 Elsevier B.V. All rights reserved.

Isobaric vapor-liquid equilibrium (VLE) data have been measured for the binary system 2,2'-oxybis[propane] + 2,5-Dimethylfuran at 50, 75, and 94 kPa and over the temperature range 321-364 K using a vapor-liquid equilibrium still with circulation of both phases. Atmospheric surface tension (ST) data have been also determined at 283.15 and 330.15 K using a maximum bubble pressure tensiometer. Experimental results show that the mixture is zeotropic and exhibits slight positive deviation from ideal behavior over the experimental range. Surface tensions, in turn, exhibit negative deviation from the linear behavior. For each isothermal condition, it is observed that the surface tension decreases as the mole fraction of 2,2'-oxybis[propane] increases, whereas at a fixed mole fraction, the surface tension decreases as the temperature increases. The VLE data of the binary mixture satisfy the Fredenlund's consistency test, and the dependence of ST on mole fraction was satisfactorily smoothed using the Redlich-Kister equation. The experimental VLE and ST data were accurately described by applying the square gradient theory to the Cubic-Plus-Association equation of state. This theoretical model was also applied to describe the surface activity of species along the interfacial region, from which it is possible to conclude that only the 2,2'-oxybis[propane] presents an interfacial accumulation which decreases as the concentration of DIPE or temperature increases. (C) 2013 Elsevier B.V. All rights reserved.

International audience; In 2008, the PPR78 model (Predictive Peng-Robinson 1978) was extended to mercaptan-containing systems by adding the sulfhydryl group (-SH). that is, by determining the values of the group-interaction parameters between the group -SH and the fourteen other groups already present in the PPR78 model. Unfortunately, due to a lack of experimental data reported in the open literature, it was not possible to characterize interactions between the group -SH and the three groups: ethane, CO2 and N-2. Very recently, vapor-liquid equilibrium data for three binary systems containing methanethiol and respectively methane, nitrogen and carbon dioxide were however measured. It was thus decided to use these data to estimate two of the missing group-interaction parameters (-SH/CO2 and -SH/N-2). For such systems, deviations observed with the PPR78 model are compared to those obtained with the CPA equation of state.

International audience; In this paper, the various concepts of idealmixtures found in the open literature are analyzed and compared. It is in particular shown that expressions conventionally admitted for the ideal-mixture propertychanges on mixing are incorrect when the idealmixture is obtained from pure components which are not in the same aggregation state as the mixture. Among these properties, a special attention is devoted to the ideal-mixture Gibbs energy change on mixing since it is used to determine the equilibrium conditions. After explaining how to properly estimate this quantity, it is shown how to correctly perform the double-tangent construction of coexisting phases for binary systems modeled with the gamma-phi approach.

In this paper the experimental setup of a new apparatus able to provide the critical properties of pure components and mixtures using either a dynamic or a static method is described. Critical temperatures ( T c ) and critical pressures ( P c ) of pure components ( n -pentane, n -heptane and n -decane) and critical loci of three binary mixtures ( n -pentane + n -heptane, n -pentane + n -decane and n -heptane + n -decane) are investigated using the dynamic method. For the system n -pentane + n -heptane, the results obtained with the dynamic method are compared with those obtained with the static method. The critical points are visually determined by observing the critical opalescence and the simultaneous disappearance and reappearance of the meniscus in the middle of the view cell which withstands operations up to 673 K and 20 MPa. The experimental critical data are compared with success to literature database and with their prediction from the PPR78 thermodynamic model.

The cosmological constant (CC) problem is the biggest enigma of theoretical physics ever. In recent times, it has been rephrased as the dark energy problem in order to encompass a wider spectrum of possibilities. It is, in any case, a polyhedric puzzle with many faces, including the cosmic coincidence problem, i.e. why the density of matter is presently so close to the CC density. However, the oldest, toughest and most intriguing face of this polyhedron is the big CC problem, namely why the measured value of the CC at present is so small as compared to any typical density scale existing in high energy physics, especially taking into account the many phase transitions that our Universe has undergone since the early times, including inflation. In this letter, we propose to extend the field equations of General Relativity by including a class of invariant terms that automatically relax the value of the CC irrespective of the initial size of the vacuum energy in the early epochs. We show that, at late times, the Universe enters an eternal de Sitter stage mimicking a tiny positive cosmological constant. Thus, these models could solve the big CC problem and have also a bearing on the cosmic coincidence problem. Remarkably, they mimic the LCDM model to a large extent, but they still leave some characteristic imprints that should be testable in the next generation of experiments., LaTeX, 13 pages, 3 figures; reference added, matches published version

Supercritical carbon dioxide (CO(2)) is Well established for use as a processing solvent in polymer applications such as polymer modification, formation of polymer composites, polymer blending, microcellular foaming, particle production and polymerization. Its gas-like diffusivity and liquid-like density in the supercritical phase allow replacing conventional, often noxious, solvents with supercritical CO(2). Though only a few polymers are soluble in supercritical CO(2), it is quite soluble in many molten polymers. CO(2) dissolution in a polymer has been interpreted physically but FT-IR studies lead to an explanation in terms of weak interactions between basic and acidic sites. Various experimental methods and equations of state are available to measure or predict the solubility of CO(2). Dissolved CO(2) causes a considerable reduction in the viscosity of molten polymer, a very important property for the applications stated above. CO(2) mainly acts as a plasticizer or solvent when contacted with a polymer. Gas solubility and viscosity reduction can be predicted theoretically from pure-component properties. In this review, experimental and theoretical studies of solubility and viscosity of several polymer melts are discussed in detail. Detailed attention is also given to recently reported applications along with aspects related to polymer processing. (c) 2005 Elsevier Ltd. All rights reserved.