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This study reviews available van der Waals- and Platteeuw-based hydrate models considering multiple occupancy of cavities. Small guest molecules, such as hydrogen and nitrogen, are known to occupy lattice cavities multiple times. This phenomenon has a significant impact on hydrate stability and thermodynamic properties of the hydrate phase. The objective of this work is to provide a comprehensive overview and required correlations for the implementation of a computationally sufficient cluster model that considers up to five guest molecules per cavity. Two methodologies for cluster size estimation are evaluated by existing nitrogen hydrate models showing accurate results for phase equilibria calculations. Furthermore, a preliminary hydrogen hydrate model is introduced and compared with the results of other theoretical studies, indicating that double occupancy of small sII cavities is improbable and four-molecule clusters are predominant in large sII cavities for pressures above 300 MPa. This work lays the foundation for further exploration and optimization of hydrate-based technologies for small guest molecules, e.g., storage and transportation, emphasizing their role in the future landscape of sustainable energy solutions. [ABSTRACT FROM AUTHOR]

Homogeneous droplet nucleation has been studied for almost a century but has not yet been fully understood. In this work, we used the density gradient theory (DGT) and considered the influence of capillary waves (CWs) on the predicted size-dependent surface tensions and nucleation rates for selected n-alkanes. The DGT model was completed by an equation of state (EoS) based on the perturbed-chain statistical associating fluid theory and compared to the classical nucleation theory and the Peng-Robinson EoS. Itwas found that the critical clusters are practically free of CWs because they are so small that even the smallestwavelengths of CWs do not fit into their finite dimensions. The CWs contribute to the entropy of the system and thus decrease the surface tension. A correction for the effect of CWs on the surface tension is presented. The effect of the different EoSs is relatively small because by a fortuitous coincidence their predictions are similar in the relevant range of critical cluster sizes. The difference of the DGT predictions to the classical nucleation theory computations is important but not decisive. Of the effects investigated, the most pronounced is the suppression of CWs which causes a sizable decrease of the predicted nucleation rates. The major difference between experimental nucleation rate data and theoretical predictions remains in the temperature dependence. For normal alkanes, this discrepancy is much stronger than observed, e.g., for water. Theoretical corrections developed here have a minor influence on the temperature dependency. We provide empirical equations correcting the predicted nucleation rates to values comparable with experiments. [ABSTRACT FROM AUTHOR]

• Five hydrofluoroethers (HFEs) representing promising engineering fluids were investigated. • Property models based on PC-SAFT equation and density gradient theory were developed. • A consistent description of properties of HFEs for vapor and liquid was achieved. • Models are in agreement with new data for the surface tension and density at 0.1 MPa. • Results can be used in HFE applications, e.g., electronics cooling and refrigeration. Hydrofluoroethers (HFEs) belong to a family of promising fluids that find application potential both in scientific research and in many industrial areas. These include electronics cooling, cascade refrigeration, heat transfer fluids, lubricant carriers or even rinsing agents. However, the thermophysical properties of HFEs required for an effective design of technical applications are only vaguely described and the available experimental data for thermodynamic and transport properties are still limited. In order to improve the description of HFEs, new experimental measurements of liquid density and surface tension at pressure of 0.1 MPa and temperatures from 260 to 338 K were carried out with a series of five HFEs; namely HFE-7000, HFE-7100, HFE-7200, HFE-7300, and HFE-7500. Liquid density was determined from a single sinker buoyancy method with an expanded uncertainty of 0.50 kg•m−3. The Wilhelmy plate method and the du Noüy ring method were used for the measurement of surface tension with expanded uncertainties of 0.068 mN•m−1 and 0.18 mN•m−1, respectively. In the modelling part, a consistent fluid property model was developed based on the physically based equation of state PC-SAFT. Additionally, regarding polarity of HFEs, empirical correlation for dipole moment was addressed. In case of larger HFE molecules, it was determined that the polar modification named PCP-SAFT, provides only marginal correction. The equations were combined with the density gradient theory (DGT) in order to model vapor-liquid phase interface and predict the surface tension. DGT+PC-SAFT was found to provide good predictions for the surface tension of the five selected HFEs. [Display omitted] [ABSTRACT FROM AUTHOR]

The experimental apparatus used for the measurement of surface tension of supercooled water using a capillary rise technique [Hrubý et al. J. Phys. Chem. Lett 5 (2014) 425 and Vinš et al. J. Phys. Chem. B 119 (2015) 5567] was modified for the measurements with seawater. New data for the surface tension of IAPSO seawater standard were collected for a salinity range from 10 g/kg to 38 g/kg and at temperatures from 30 °C down to −25 °C. The reported measurements are relative to the surface tension of pure water at the reference temperature of 15 °C. The combined standard uncertainty of the relative surface tension is better than 0.30%. The new data do not indicate any anomaly in the temperature trend of the surface tension of low-temperature and supercooled seawater down to temperature of −25 °C. The data agree with other literature data measured at stable conditions above 0 °C. Recent correlation by Nayar et al. [J. Phys. Chem. Ref. Data 43 (2014) 043103], considered as a potential standard for the surface tension of seawater, shows a very good agreement with the new data both in the stable region and under the metastable supercooled conditions. The differences between the correlation and the experimental data are entirely within the experimental uncertainty. Consequently, the recommended range of validity of the correlation by Nayar et al. can be extended into the supercooled region down to −25 °C for salinity up to 38 g/kg. In addition, an alternative correlation for the surface tension of seawater compatible with the recent correlation by Pátek et al. [J. Chem. Eng. Data 61 (2016) 928] for pure water is introduced. The new correlation has the same form as that by Nayar et al., however with slightly modified coefficients. Both correlations for seawater provide comparable results over the temperature and salinity ranges of the available experimental data. Unlabelled Image • New accurate data for the surface tension of seawater were measured with a unique capillary-rise apparatus. • Data were collected from 30 °C down to −25 °C, i.e. including the supercooled conditions below equilibrium freezing point. • The study substantially enlarges rather limited database of the experimental data for the surface tension of seawater. • New measurements can be well reproduced by the recent correlation by Nayar et al. (2014) extrapolated below 0 °C. • Data will be used in the evaluation of correlation by Nayar et al. as a new standard for seawater surface tension. [ABSTRACT FROM AUTHOR]

Abstract This study presents mathematical modelling of the properties of vapour-liquid phase interfaces for multi-component mixtures. The developed model can be applied both on a standard case of a planar phase interface and on a spherical interface representing droplets or bubbles. The PCP-SAFT equation of state is utilized for thermodynamic property evaluation. The fundamentals of the presented model lie in the Density Gradient Theory (DGT) used to formulate the governing differential equations. An innovative approach to the problem formulation divides the solution into two parts, an algebraic solution and a differential equations solution, that can be solved individually. The developed solution method can be applied on both interface geometries, for which the density profile is solved as the main quantity describing the interface. In addition to the density profile, the surface tension and adsorptions of mixture components within the interface are computed. Mixtures with CO 2 were selected as the demonstrative systems in this work. Modelled mixtures of n -butane + CO 2 , n -decane + CO 2 , and SF 6 + CO 2 were compared with available experimental data for surface tension and also with the predictions of a more general Density Functional Theory (DFT). Based on these comparisons, the model was found to be in a good agreement with experimental data and comparable to the DFT predictions. Graphical abstract Image 1 Highlights • Unified model for planar and spherical phase interface geometric types is developed. • Specialized split solution method is used for PCP-SAFT together with DGT. • Properties usefull for nucleation are calculated on examples of CO 2 rich systems. • Model is verified on available experimental data and also density functional theory. • Some predictions can be used even with zero binary interaction parameter. [ABSTRACT FROM AUTHOR]

A new model for mixed hydrates is proposed, which is intended for modeling the formation of mixed hydrates in carbon capture and storage (CCS)-relevant mixtures. The model is based on the model developed by Ballard and Sloan [A.L. Ballard, E.D. Sloan Jr., Fluid Phase Equilib. 194 (2002) 371–383], which itself is based on the statistical approach by van der Waals and Platteeuw [J.H. van der Waals, J.C. Platteeuw, Adv. Chem. Phys. 2 (1959) 1–57]. The model of Ballard and Sloan contains a considerable amount of adjustable parameters for mixed hydrates and comparatively complex mixing rules, especially for the molar volume of mixed hydrates. For the newly developed mixed hydrate model, a simple mixing rule for the volume is used, which does not contain any adjustable parameters. Comparisons of the new model with experimental data for mixed hydrates in the ternary system carbon dioxide + methane + water show better results than the model by Ballard and Sloan. Results for the quaternary system nitrogen + oxygen + argon + water are in good agreement with the available experimental data. Furthermore, as in our previous work focused on modeling hydrates of pure gases [Fluid Phase Equilib. 427 (2016) 268] and contrary to other published hydrate models, reference equations of state are used in order to model phases in equilibrium with hydrates. A comprehensive study on phase equilibria with up to four phases in equilibrium for ternary mixtures forming gas hydrates and other solid phases was carried out in this work. The obtained results demonstrate the capabilities of the proposed mixed hydrate model and developed phase equilibrium algorithms. [ABSTRACT FROM AUTHOR]

• New force field parameters were derived from quantum mechanical calculations for five polar hydrofluoroethers. • Molecular dynamics (MD) simulations were done for the coefficient of self-diffusion, viscosity, and thermal conductivity. • The Cohen-Turnbull free volume and the fractional Stokes-Einstein equations were tested for the self-diffusion coefficient. • Self-diffusion coefficient was scaled with viscosity in the logarithmic plot of DT −1 vs η for the five hydrofluoroethers. • Nonequilibrium MD simulations outperform the equilibrium one for the thermal conductivity, but with comparable accuracy. Hydrofluoroethers (HFEs) having simultaneously hydrocarbon (HC) and fluorocarbon (FC) moieties connected through ether oxygen are polar chain molecules with dielectric properties, which makes them a good heat transfer medium, e.g., for cooling of electronics or magnetic devices. In this work, we report, validate, and test high level-ab initio derived force fields and we use partial charges fitted to the electrostatic potential surface (EPS) to reproduce the dipole moments. Computer simulations were performed over a wide range of temperatures and densities to calculate the transport coefficients in the condensed-phase and comparisons were made against available experimental data for five selected molecules; namely HFE-7000, HFE-7100, HFE −7200, HFE −7300, and HFE −7500. Furthermore, structural properties and enthalpy of vaporization were obtained from molecular simulations. Cohen and Turnbull formula for the translational self-diffusion coefficient was tested in the free-volume cast, which itself was correlated against the isothermal compressibility, which can explain the phenomenon of transport properties in liquids, D ∝ e x p - γ / V f / V ∗ . The fractional Stokes-Einstein relation was also tested to scale the self-diffusion coefficient vs viscosity in the form of (DT −1) ∝ (1/ η) s , with s ranging between ≈ 0.89 and 0.92 for the five molecules in the reduced density range of ρσ 3 = 0.56 to 0.75. Finally, the non-equilibrium molecular dynamics (NEMD) simulations of thermal conductivity was found to outperform the equilibrium Green-Kubo approach, but both with comparable accuracy. [ABSTRACT FROM AUTHOR]

The temperature course of the surface tension of supercooled water was suspected to exhibit an anomalous feature--the so-called second inflection point (SIP). Besides some theoretical and molecular simulation studies, this hypothesis was primarily supported by experimental data by P. T. Hacker [NACA TN 2510, 1951]. Recently, the present group performed accurate surface tension measurements down to -26 °C using a modified capillary rise [Hrubý et al. J. Phys. Chem. Lett 2014, 5, 425 and Vinš et al. J. Phys. Chem. B 2015, 119, 5567] which, in contrast to Hacker's data, showed no SIP anomaly. To confirm that the qualitatively different observations are not related to some fundamental phenomenon, we developed an experimental device employing basically the same method as Hacker with a horizontal capillary tube. New experimental data for the surface tension of supercooled water measured with the horizontal capillary setup down to -23 °C are presented in this study. The new data show a very good agreement with the previous capillary rise measurements. It was confirmed that the temperature dependence of the surface tension is free of SIP in a temperature range from -23 to 23 °C and can be well-represented by the IAPWS standard extrapolated below 0.01 °C. However, a small systematic deviation from the IAPWS correlation can be seen at temperatures below -15 °C. [ABSTRACT FROM AUTHOR]

In this study comprising a series of three articles, the model for pure CO 2 hydrate by Jäger et al. [Fluid Phase Equilib. 338 (2013) 100–113] has been improved and extended to other gases relevant in Carbon Capture and Storage (CCS) applications. The new model for eight pure gas hydrates is inspired by the currently most accurate model available for natural gas hydrates by Ballard and Sloan [Fluid Phase Equilib. 194 (2002) 371–383], which belongs to the family of van der Waals and Platteeuw (vdWP) models [Adv. Chem. Phys. 2 (1959) 1]. The new model is combined with highly accurate equations of state (EoS) in form of the Helmholtz energy for fluid phases and with Gibbs energy models for pure solid phases. Part I contains a critical analysis of the main parameters of the vdWP-based hydrate model. In this article (part II), the new hydrate model is described. A multi-property fitting algorithm is presented, which allows for simultaneous fitting of the model parameters to hydrate phase equilibrium data and to various types of hydrate composition data. Kihara potential parameters and reference parameters of the hydrate model were evaluated for eight selected hydrate formers; namely the CCS relevant gases carbon dioxide, argon, nitrogen, oxygen, carbon monoxide, and methane, and additionally ethane and propane. Experimental data used as an input to the fitting algorithm were weighted using uncertainty estimates. Estimation of the uncertainties of chemical potential along the three-phase coexistence lines including hydrates is a non-trivial task. Clearly, the uncertainty is dominated by various metastable and hysteresis effects, rather than by uncertainties of pressure and temperature measurements. For these reasons, some ad-hoc approaches have been developed. The uncertainty could straightforwardly be estimated in sparingly occurring regions covered by multiple data sources. Assuming a band of constant work of formation of hydrates along the three-phase coexistence lines then provided a plausible estimate of the uncertainties in a broad range of thermodynamic conditions. Usually, the Langmuir constant is fitted together with the reference state parameters of the hydrate model to three-phase hydrate formation data. In this work, a method is discussed that directly links the Langmuir constant to hydrate composition data. The performance of the new hydrate model dedicated to typical CCS gases in binary mixtures with water is demonstrated in part III. The model has been implemented in the software package TREND 2.0 by Span et al. [Thermodynamic Reference and Engineering Data 2.0. (2015) Lehrstuhl fuer Thermodynamik, Ruhr-Universitaet Bochum]. [ABSTRACT FROM AUTHOR]

In this study divided in a series of three articles, the model for pure CO 2 hydrate by Jäger et al. [Fluid Phase Equilib. 338 (2013) 100–113] has been improved and extended to other gases relevant in Carbon Capture and Storage (CCS) applications. The new hydrate model is inspired by the model for natural gas hydrates by Ballard and Sloan [Fluid Phase Equilib. 194 (2002) 371–383], which belongs to the family of van der Waals and Platteeuw (vdWP) models [Adv. Chem. Phys. 2 (1959) 1]. The new model is combined with highly accurate equations of state (EoS) in form of the Helmholtz energy for fluid phases and with Gibbs energy models for pure solid phases. In part I, a critical analysis of the main parameters of the vdWP-based hydrate model was performed. A multi-property fitting algorithm developed for optimization of parameters of the new hydrate model is introduced in part II. Results of the model, including phase equilibria with hydrates, composition of hydrates, and enthalpy of formation of hydrates are provided in this article (part III). The model results are for most hydrate formers better or comparable to the results of the model of Ballard and Sloan. However, for ethane hydrates the overall results are worse which is discussed in the results section. The model has been implemented in the software package TREND 2.0 by Span et al. [Thermodynamic Reference and Engineering Data 2.0. (2015) Lehrstuhl fuer Thermodynamik, Ruhr-Universitaet Bochum]. Example calculations with the new hydrate model implemented in TREND 2.0 and applied to CCS-relevant problems are shown and discussed. [ABSTRACT FROM AUTHOR]

In this study, divided in a series of three articles, the model for pure CO 2 hydrate by Jäger et al. [Fluid Phase Equilib. 338 (2013) 100–113] has been improved and extended to other gases relevant in Carbon Capture and Storage (CCS) applications. The new gas hydrate model is inspired by the currently most accurate model available for natural gas hydrates by Ballard and Sloan [Fluid Phase Equilib. 194 (2002) 371–383], which belongs to the family of van der Waals and Platteeuw (vdWP) models [Adv. Chem. Phys. 2 (1959) 1]. The new model is combined with highly accurate equations of state (EoS) in form of the Helmholtz energy for fluid phases and with Gibbs energy models for pure solid phases. Part I describes a critical analysis of the main parameters of the vdWP-based hydrate model. The influences of the specific hydrate volume, of the Langmuir constant, and of the EoSs used for other phases than hydrate on the predicted hydrate composition and on phase equilibria with gas hydrates were investigated. A new correlation for the pressure dependency of the volume of gas hydrates forming structures sI and sII has been developed. The correlation based on the Murnaghan EoS [Proc. Natl. Acad. Sci. U. S. A. 30 (1944) 244] has good extrapolating behavior and behaves in a physically reasonable manner. It is shown that all experimental data for hydrate formers including mixed hydrates can be represented reasonably well by a universal bulk modulus around 10 GPa. Furthermore, it was found that the bulk modulus affects phase equilibria at high pressures while its impact on phase equilibria at moderate and low pressures below about 30 MPa is negligible. A strong influence of the Langmuir constant on the hydrate composition was observed, especially in case of small cavities of both sI and sII hydrate structures. Additionally, the influence of EoSs used for other phases than hydrate on the accuracy of quadruple point predictions is discussed. A multi-property fitting algorithm developed for optimization of parameters of the new hydrate model is introduced in part II. Results of the model including phase equilibria with hydrates, composition of hydrates, and enthalpy of formation of hydrates are provided in part III. The model has been implemented in the software package TREND 2.0 by Span et al. [Thermodynamic Reference and Engineering Data 2.0. (2015) Lehrstuhl fuer Thermodynamik, Ruhr-Universitaet Bochum]. [ABSTRACT FROM AUTHOR]

In this study, the Cahn-Hilliard density gradient theory (GT) is used for predicting the surface tension of various binary mixtures at relatively wide temperature ranges and for testing the application of the GT for predictions of homogeneous nucleation. The GT was combined with two physically based equations of state (EoS), namely the perturbed-chain (PC) statistical associating fluid theory (SAFT) and its modification for polar substances the perturbed-chain polar (PCP) SAFT. The GT applied to the planar phase interface was employed to predict the interfacial tension for various quadrupolar (CO and benzene) and dipolar (difluoromethane, i.e., R32; pentafluoroethane, i.e., R125; and 1,1,1,2-tetrafluoroethane, i.e., R134a) substances and for five binary mixtures including polar components ( n-decane + CO, benzene + CO, R32 + R125, R32 + R134a, R134a + R125). The PCP-SAFT EoS combined with the GT provides more accurate results for both the quadrupolar and dipolar substances than the original PC-SAFT EoS. Besides the planar phase interface, the GT was also applied to the spherical phase interface simulating a critical cluster occurring in homogeneous nucleation of droplets. Carbon dioxide was considered, because it has a relatively high quadrupole moment and because of its relevance to natural gas processing. Application of the PCP-SAFT EoS provides a significant improvement compared to the PC-SAFT EoS, and it is clearly superior to the classical cubic Peng-Robinson EoS, which is still used for modeling droplet nucleation. [ABSTRACT FROM AUTHOR]

Abstract: Formation of gas hydrates is an important feature of the water–carbon dioxide system. An accurate description of thermodynamic properties of this system requires a consistent description of both fluid (liquid, vapor, and supercritical fluid) and solid states (ice, dry ice, and hydrates) and of their respective phase equilibria. In this study, we slightly modified and refitted the gas hydrate model by A.L. Ballard, E.D. Sloan [Fluid Phase Equilib. 194 (2002) 371–383] to combine it with highly accurate equations of state (EoS) in form of the Helmholtz energy and Gibbs energy for other phases formed in the water–carbon dioxide system. The mixture model describing the fluid phases is based on the IAPWS-95 formulation for thermodynamic properties of water by W. Wagner, A. Pruß [J. Phys. Chem. Ref. Data 31 (2002) 387–535] and on the reference EoS for CO2 by R. Span, W. Wagner [J. Phys. Chem. Ref. Data 25 (1996) 1509–1596]. Both pure-fluid equations are combined using newly developed mixing rules and an excess function explicit in the Helmholtz energy. Pure-component solid phases were modeled with the IAPWS formulation for water ice Ih by R. Feistel, W. Wagner [J. Phys. Chem. Ref. Data 35 (2006) 1021–1047] and with the dry ice EoS by A. Jäger, R. Span [J. Chem. Eng. Data 57 (2012) 590–597]. Alternatively, the hydrate model was combined with the GERG-2004 EoS [O. Kunz, R. Klimeck, W. Wagner, M. Jaeschke, GERG technical monograph 15, VDI Verlag GmbH, Düsseldorf, 2007]. Since the gas hydrate model uses the fugacity of the gas component in the coexisting phase as an input variable, the accuracy of the predicted phase equilibria was significantly improved by using highly accurate EoSs for coexisting phases. The new hydrate model can be used in a temperature range of 150–295K and at pressures up to 500MPa. Together with the models describing the fluid and pure solid phases it allows for the desired accurate and consistent description of all phases and phase equilibria including, e.g., flash calculations into two and three phase regions. [Copyright &y& Elsevier]

Abstract: Even small amount of non-condensable gas – mostly air or nitrogen – present inside a compression refrigerating circuit may decrease the efficiency of the cooling system. So far, a quantitative assessment of the effect of dissolved gases on the cooling circuit performance is hindered by unavailability of suitable thermodynamic models. In this study, we analyzed the solubility of nitrogen in the following refrigerants: hydrochlorofluorocarbons (HCFC) R22, R123, R124; hydrofluorocarbons (HFC) R23, R32, R125, R134a; perfluorocarbons (PFC) R14, R116, R218, R-3-1-10; and hydrocarbons (HC) R290, R600a. Perturbed-Chain (PC) Statistical Associating Fluid Theory (SAFT) and its modification for polar fluids PCP-SAFT were used to model the temperature dependence of the Henry’s law constant of nitrogen. A simple correlation of the Henry’s law constants valid over large temperature ranges was developed, suitable for assessment of the adverse effects of dissolved nitrogen (and approximately air) on the performance of compression cooling systems. [Copyright &y& Elsevier]

Hydrofluoroethers (HFEs) represent a new family of promising engineering fluids suitable for technical cleaning and cooling of electronic and magnetic devices or as admixtures in refrigerant blends. Here, we report accurate data for the liquid density at 0.1 MPa and temperatures from 273.15 K to 343.15 K for a series of five HFEs, namely, HFE-7000, HFE-7100, HFE-7200, HFE-7300, and HFE-7500. A highly sensitive vibrating tube densimeter with a borosilicate glass U-tube calibrated according to the procedure by Prokopová et al. (J Chem Thermodyn 173:106855, 2022) provided density data with an expanded uncertainty ( k = 2 ) of 0.13 kg · m - 3 . Influences such as sample degassing, water content, or sample temperature before its dosing into the densimeter are discussed. Thanks to the high sensitivity of the used densimeter, an unexpected shift in the density of different HFE-7100 and HFE-7200 liquid samples was detected. Unlike other HFEs, HFE-7100 and HFE-7200 are mixtures of two hardly separable isomers, which were so far considered having identical thermophysical properties. Utilizing nuclear magnetic resonance spectroscopy, the ratio of n-isomer and iso-isomer was inspected for various liquid samples. In the range of iso-isomer mole fraction from 0.61 to 0.77, the new measurements revealed density differences of more than 5 kg · m - 3 in case of HFE-7100 and of about 3 kg · m - 3 in case of HFE-7200. Consequently, for some applications, the properties of different HFE isomers cannot be considered identical. The Rackett-type correlation for the saturated liquid density was fitted using the new and the literature data. [ABSTRACT FROM AUTHOR]

Hydrofluoroethers (HFEs) represent a new generation of promising engineering fluids for heat transfer or cleaning applications. In this work, quantum chemistry calculations (qcc) were employed to obtain ideal gas heat capacities, Cpig, for the selected HFEs and comparisons were made against the group contribution (GC) methods by Rihani and Doraiswamy, Yoneda, and Joback. Comparison between B3LYP/6-31++ G(d,p) density functional theory (DFT) and Hartree–Fock (HF) methods showed that HF method provides better representation of the available experimental gas-phase speed of sound data for HFE-7000. Critical properties and acentric factors of the selected HFEs were optimized and compared to the other reported values. The Peng–Robinson equation of state (PR EoS) combined with the Cpig correlation, allowing calculation of the ideal gas Helmholtz free energy, was used to model a complete set of thermodynamic properties of the five selected HFEs; namely HFE-7000, HFE-7100, HFE-7200, HFE-7300, and HFE-7500. The volume-translated (VT) PR EoS was also tested as an alternative. The accuracy of PR EoS for representing the phase behavior and caloric properties of the selected HFEs was analyzed based on the comparison with nearly 3500 experimental data points and a preliminary multiparameter EoS available for HFE-7000. Although relatively simple, but still widely used, PR EoS was found to provide reasonable vapor–liquid predictions for HFEs and, as such, can be used effectively in the design of their various applications. In addition, a vapor pressure correlation and the critical compressibility factor were analyzed from the view of application on various alternative refrigerants such as HFEs and hydrofluoroolefines. [ABSTRACT FROM AUTHOR]

Abstract: We present experimental speed of sound data for the saturated fluorocarbons used most frequently in particle detector cooling systems. Data were collected over the moderate range of pressure (≤0.4MPa) and temperature 250–340K. A commercial sound/density analyzer operating on the vibrating tube principle was employed for the measurements in liquid state. A dedicated sonar analyser – described in detail – was recently redesigned and developed for the speed of sound measurements in gas phase. Data for speed of sound in saturated fluorocarbons presented in previous papers [V. Vacek, G. Hallewell, S. Ilie, S. Lindsay, Fluid Phase Equilib. 174 (2000) 191–201; V. Vacek, G. Hallewell, S. Lindsay, Fluid Phase Equilib. 185 (2001) 305–314] were reanalyzed and corrected and some new measured data were added. Our experimental data were then used to validate a theoretically based equation of state application rather than the empirical or semi-empirical equations of state mostly used up to now in fluorocarbon applications. [Copyright &y& Elsevier]

• A calibration procedure of the atmospheric vibrating tube densimeter is introduced for temperatures between 273 and 363 K. • An uncertainty analysis is introduced based on the accurate measurements with ultrapure water and dry air. • The calibration was verified on a series of reference liquids with viscosity ranging from 0.3 mPa s to 600 mPa s. • Standard uncertainty of liquid density was determined between 0.030 kg m−3 and 0.14 kg m−3 for typical and highly viscous liquids, respectively. Vibrating tube densimeter (VTD) is a popular instrument providing a quick and accurate measurement of density for large variety of liquids and gases. Sensitive commercial instruments have resolution of down to 0.001 kg · m - 3 and their accuracy is declared to reach 0.007 kg · m - 3 under ideal conditions at temperatures close to ambient. However, the uncertainty of the obtained data can be significantly higher when it comes to measurements over wider temperature range. We present calibration procedure for a commercial borosilicate glass VTD (namely Anton Paar DMA 5000 M) over the temperature range from 275 to 363 K together with an uncertainty analysis. The approach is similar to that of Fritz et al. [J. Phys. Chem. B 104 (2000) 3463] when the density can be obtained from the relative oscillation period PQ , damping difference Δ D 0 and calibration parameters A , B , V 1 , and V 2 as ρ = A (1 + V 1 Δ D 0 + V 2 Δ D 0 2) PQ 2 - B. Temperature dependencies of the calibration parameters A and B were determined from a series of precise measurements with ultrapure water and dry air correlated to the densities calculated from the IAPWS-95 equation of state for water and the IAPWS G8-10 guideline for humid air. The calibration procedure was verified on measurements with toluene, ethanol, ethylene glycol, and glycerol. A detailed analysis of the uncertainty budget resulted in the standard uncertainty around 0.030 kg · m - 3 for typical low-viscosity samples. In case of highly viscous liquids such as low-temperature ethylene glycol or glycerol, the uncertainty can reach 0.060 kg · m - 3 or even 0.14 kg · m - 3 , respectively, at the dynamic viscosity exceeding 50 mPa · s. Other influences are also discussed, such as the relation between fluid viscosity and damping, the isotopic composition of the calibration water, the measurement procedure covering VTD cleaning and filling, and the effect of water contained in samples. [ABSTRACT FROM AUTHOR]