Density Of Liquid Phase Research Articles

Measurements of Vapor Pressure, Heat Capacity, and Density along the Saturation Line for Cyclopropane Carboxylic Acid, N,N-Diethylethanolamine, 2,3-Dihydrofuran, 5-Hexen-2-one, Perfluorobutanoic Acid, and 2-Phenylpropionaldehyde

This paper reports measurements made for DIPPR Research Project 821 in the 1997 Project Year. Vapor pressures were measured to a pressure limit of 270 kPa or lower decomposition point for all six compounds using a twin ebulliometric apparatus. Liquid-phase densities along the saturation line were measured for each compound over a range of temperatures (ambient to a maximum of 448 K). A differential scanning calorimeter was used to measure two-phase (liquid + vapor) heat capacities for each compound in the temperature region ambient to the critical temperature or lower decomposition point. The results of all the measurements were combined to derive a series of thermophysical properties including critical temperature, critical density, critical pressure, acentric factor, enthalpies of vaporization [within the temperature range (±50 K) of the vapor pressures], solubility parameter, and heat capacities along the saturation line. Wagner-type vapor-pressure equations were derived for each compound. In addition, the liquid-phase densities were compared with values derived using a four-term power series in [(1 − Tr)n/3]. All measured and derived values were compared with those obtained in a search of the literature.

Vessel outflow sensitivity to composition

The vessel composition is important when considering vessel outflow because changes in composition change the density and potentially more importantly change the shape and location of the boundary of the two-phase envelope. The influence on the phase boundary can be significant on vessel outflow as the liquid phase density is typically two orders of magnitude larger than the gas phase density for pressures and temperatures remote from the thermodynamic critical point. In this article two issues are addressed, outflow sensitivity to composition of hydrocarbon systems with a large component of methane, and outflow from systems where a petroleum fraction representation of composition is used. It is shown that approximating multi-component systems with a large methane content by methane can result in significant discrepancies in the predicted mass flow rate and vessel pressure. When a vessels composition is characterised by petroleum fractions, and the Kesler–Lee equations are used to predict thermodynamic properties, the predicted outflow is almost comparable to the predicted outflow calculated using a mole fraction representation of composition.

THEORETICAL INVESTIGATION ON VARIABLE-DENSITY SPRAYS

The aim of the present investigation is the analysis of the influence of liquid-fuel compressibility on the simulation of sprays produced by high-pressure injection systems. Two different equations have been introduced in the KIVA3V code to calculate liquid-phase density. The first one determines fuel density by using a second-order function of drop temperature and pressure, while the second one also takes into account the quantity of air dissolved in the fuel. Breakup, vaporization, and collision models as well as the energy, momentum, and air-spray mass exchange equations were modified so that each droplet would have a different density, according to its position and evolution. A comparison between experimental and numerical data for sprays injected in a constant-volume vessel at ambient temperature and pressure has been carried out to test the practical capability of the modified KIVA3V subroutines. The predicted and measured results of penetration versus time and drop size distribution showed good agreement. An in-depth study of the influence of gas temperature on the droplet vaporization rate has been performed for a single droplet and for sprays injected in a high-temperature, medium-pressure, constant-volume chamber. The effect of fuel density variability on vaporizing noncombusting sprays has been investigated for both models. The air dissolved in the fuel was found to affect liquid-phase density only at low ambient pressure. Finally, the experimental data measured on a small-bore diesel engine have been used to verify the provisional capabilities of constant- and variable-density models. NO and soot predictions have shown to be dependent on the model used for liquid-phase density.

Momentum Distribution of Liquid 3He: Simulation of Deep Inelastic Neutron Scattering Experiments with the VESUVIO Spectrometer

The recent experimental determination of the 3He single-particle mean kinetic energies in solid hcp, bcc and dense liquid phases has allowed to perform an accurate test of the single-particle dynamical properties derived from the existing theoretical models. A Monte Carlo simulation of a Filter-Difference neutron spectrometer for Deep Inelastic Neutron Scattering with enhanced resolution performance is presented. It aims to study the feasibility of an accurate experimental determination of the 3He momentum distributions in pure liquid and in 3He-4He liquid mixtures.

The non-random distribution of free volume in fluids: non-polar systems

In local composition models the focus is, usually, on the distribution of molecules or molecular segments and not on the distribution of the free volume of the system. At conditions, however, where the free volume is a significant percentage of the total volume of the system, as in the case of critical or supercritical conditions, its non-random distribution may not be negligible even for non-polar substances. In this work an attempt is made to account for the non-random distribution of the free volume in fluids and their mixtures. The classical quasi-chemical approach is used in connection with the lattice fluid model. The basic formalism is first developed for pure fluids and subsequently extended to multi-component mixtures by preserving its simplicity. The model is used for the calculation of vapour pressures and orthobaric densities of representative non-polar fluids and for the calculation of compositions and densities of liquid and vapour phases at equilibrium in mixtures of non-polar fluids. These calculations are compared with experimental data and with the corresponding calculations of the original lattice fluid model.

Equilibrium phase compositions, densities, and interfacial tensions for ethane + 1-methylnaphthalene at 344.3 K

An automated experimental apparatus was used to measure the equilibrium liquid and vapor phase compositions and densities, and interfacial tensions for ethane+1-methylnaphthalene at 344.3 K. The phase composition data can be described within 0.0005 in mole fraction, the phase densities within 3 kg/m 3, and the interfacial tensions within 5%, using scaling-law-based smoothing functions. The present measurements constitute a useful complement to existing literature data.

Measurement of phase equilibria of supercritical ethane and paraffins

This work entails the design and development of a static variable-volume cell with the aim to measure high-pressure phase equilibria of mixtures of supercritical solvents and paraffinic hydrocarbons. The cell was used to measure the ethane– n-alkane phase equilibria and densities near the critical point of the mixture. Experimentally determined phase equilibria are reported for the binary mixtures of supercritical ethane with n-C 16, n-C 24 and n-C 28 in the temperature range of 313–352 K. Several equations of state (EOS) were fitted to this data, and it was found that the Soave–Redlich-Kwong equation gives a reasonable representation of the measured phase equilibria but fails in the representation of the mixture densities—a known problem of cubic EOS. The use of the Patel–Teja EOS resulted in the smallest error in the liquid phase density representation.

Phase equilibria of binary mixtures by molecular simulation and cubic equations of state

Molecular simulation data were used to study the performance of equations of state (EoS) and combining rules usually employed in thermodynamic property calculations. The Monte Carlo method and the Gibbs ensemble technique were used for determining composition and densities of vapor and liquid phases in equilibrium for binary mixtures of Lennard-Jones fluids. Simulation results are compared to data in the literature and to those calculated by the t-PR-LJ EoS. The use of adequate combining rules has been shown to be very important for the satisfactory representation of molecular simulation data.

Correlation of Vapor-Liquid Equilibria and Saturated Densities of Binary Mixtures by the Generalized Scott-Fuller-Soave-Redlich-Kwong Equation of State.

A new cubic type of Scott-Fuller-Soave-Redlich-Kwong equation of state (SFSRK EOS) has been proposed to calculate both vapor-liquid equilibria and saturated densities of vapor and liquid phases. The parameters of the proposed EOS are given for each pure substance. In this study, the parameters were generalized, based on the critical properties and the acentric factor, for several components representative of LNG. Furthermore, by adopting the exponent type mixing rules for the parameters, both the vapor-liquid equilibria and the saturated densities of vapor and liquid phases for binary mixtures were correlated using the SFSRK EOS. The calculated results show a good correlation with observations, especially for the liquid phase densities.

A study of the condensed phases and solid–solid phase transition in toluene: A Monte Carlo investigation

A Monte Carlo study of the orthorhombic(β), monoclinic(α), and liquid phases of toluene in the isobaric isothermal ensemble employing variable shape simulation cell is reported here. The intermolecular potential of Williams and Starr is seen to reproduce the lattice parameters and other known properties reasonably well for the α-phase. The β-phase is not reproduced as well. The structure has been characterized in terms of the radial distribution functions and orientational correlation functions. The transition from the orthorhombic low temperature β-phase to the high temperature monoclinic α-phase has been successfully simulated. The transition is first order and lies between 140 and 145 K in agreement with experiment. The reverse transition from the α- to the β-phase does not take place in agreement with experiment. The liquid phase density and the heat of vaporization are reproduced well. The potential employed predicts an interaction energy which is about 5% in excess of the experimental value. The orientational correlation function and the radial distribution functions are sensitive to the potential and suggest where improvements are possible.

Liquid-gas phase transition in Bose-Einstein condensates with time evolution

We study the effects of a repulsive three-body interaction on a system of trapped ultra-cold atoms in Bose-Einstein condensed state. The stationary solutions of the corresponding $s-$wave non-linear Schr\"{o}dinger equation suggest a scenario of first-order liquid-gas phase transition in the condensed state up to a critical strength of the effective three-body force. The time evolution of the condensate with feeding process and three-body recombination losses has a new characteristic pattern. Also, the decay time of the dense (liquid) phase is longer than expected due to strong oscillations of the mean-square-radius.

Conformational properties of cyclooctane: a molecular dynamics simulation study

Atomistic molecular dynamics simulations have been used to elucidate the conformational properties of cyclooctane in the gas and bulk liquid phases. Accurate reproduction of the gas phase structure, and of the liquid phase densities and solubility parameters have been used as prerequisites to the prediction of conformational properties. The gas phase results clearly indicate the presence of a conformational mixture consisting of the crown, boat-chair, twist-boat-chair and boat-boat conformers at all temperatures (161, 313 and 400 K) studied. The fraction of the crown family of conformers was found to be relatively insensitive to temperature. However, the relative concentrations of the twist-boat-chair and boat-chair conformations was found to be highly temperature dependent with the boat-chair being favoured at low temperatures. Bulk packing was found to have a profound effect on the conformational properties in the liquid phase. At the temperatures studied (313 and 400 K) the boat-chair family was predominant, with the crown and boat families being essentially absent. The twist-boat-chair conformation was detected in the liquid phase at both temperatures. The pseudorotation pathway for the twist-boat-chair to boat-chair interconversion was prevalent in both gas and liquid phases establishing the conformational flexibility and the relative importance of the twist-boat-chair conformer in comparison to the crown family. The study successfully explains the separate experimental findings in both the gas and liquid phases of cyclooctane.

Conformational properties of cyclooctane: a molecular dynamics simulation study

Atomistic molecular dynamics simulations have been used to elucidate the conformational properties of cyclooctane in the gas and bulk liquid phases. Accurate reproduction of the gas phase structure, and of the liquid phase densities and solubility parameters have been used as prerequisites to the prediction of conformational properties. The gas phase results clearly indicate the presence of a conformational mixture consisting of the crown, boat-chair, twist-boat-chair and boat-boat conformers at all temperatures (161, 313 and 400 K) studied. The fraction of the crown family of conformers was found to be relatively insensitive to temperature. However, the relative concentrations of the twist-boat-chair and boat-chair conformations was found to be highly temperature dependent with the boat-chair being favoured at low temperatures. Bulk packing was found to have a profound effect on the conformational properties in the liquid phase. At the temperatures studied (313 and 400 K) the boat-chair family was predominant, with the crown and boat families being essentially absent. The twist-boat-chair conformation was detected in the liquid phase at both temperatures. The pseudorotation pathway for the twist-boat-chair to boat-chair interconversion was prevalent in both gas and liquid phases establishing the conformational flexibility and the relative importance of the twist-boat-chair conformer in comparison to the crown family. The study successfully explains the separate experimental findings in both the gas and liquid phases of cyclooctane.

The first observation of muon-to-alpha sticking K β X-rays in muon catalyzed D-T fusion

At the RIKEN-RAL Muon Facility, we have observed K β (3 p→1 s) μα sticking X-rays from muon catalyzed D-T fusion with various tritium concentrations ( C t =0.1−0.7) and high density solid and liquid phases. Statistics of K β X-rays were not enough to determine the peak shape, but the intensity was obtained with an adequate constraint to the K β shape using the theoretically calculated peak shape. No significant dependence of the K β /K α ratio on these target conditions was found, and our results ( Y( K β )/ Y( K α )∼7%) gave smaller values than the existing theoretical calculations. It suggests an existence of unexplained atomic process in the collision processes between ( αμ) + and condensed media.

Vapour-Liquid and Liquid-Solid Equilibria in the System Th(NO3)4-UO2(NO3)2-HNO3-H2O

Vapour-liquid and liquid-solid equilibria were studied in the system Th(NO3)4-UO2(NO3)2-HNO3-H2O. Hexahydrate of thorium nitrate as well as hexa- and trihydrate of uranyl nitrate were supposed to be formed in this system. Empiric equations of solubility isotherms were derived for 25 °C and liquid phase densities were determined. It was established that nitric acid was salted out into the vapour phase by the nitrates present in the system both separately and simultaneously. Empiric equation was derived that describes the relationship between the HNO3 concentration of condensate and that of all liquid phase components.

INFLUENCE OF PHYSICAL PROPERTIES OF SOLID-LIQUID PHASE ON DEBRIS FLOWS

The velocity and sediment concentration of sediment-water mixture flow change by the physical properties; e. g., mass density of solid and liquid phase, viscosity of liquid, interparticle friction angle of solid particle, etc. The laminar viscous term is introduced into the constitutive relations developed formerly by Egashira et al. to solve those. The effects of physical properties of solid and liquid phase on debris flow are investigated by means of experimental data as well as of numerical solutions for velocity profile, sediment concentration profile, flux sediment concentration and flow resistance. The results suggest that the present constitutive relations evaluate any changes of debris flow caused by physical properties of solid-liquid phase.

Apparatus for Measuring Vapor-Liquid Equilibria and Phase Densities of Complex Aqueous Solutions

A new apparatus has been designed and constructed to measure the vapor- liquid equilibria and phase densities of corrosive, complex aqueous solutions containing organic solvents and salts. The apparatus is designed for isothermal operation from ambient temperatures to 400 K. Phase equilibrium measurements at higher temperatures may be achieved without density measurements. This paper presents a detailed description and performance testing of the apparatus. Measurements of the vapor pressures and saturated liquid densities of ethanol and the vapor pressure of an ethanol-water mixture (xethanol=0.6743 mole fraction) from 308 to 385 K at pressures to 15 MPa are used as performance tests.

Regression to Experimental PVT Data

Abstract A procedure is presented for regression of equation of state parameters to experimental PVT-data. The starting point is a predictive C7+ characterization based on the available analytical data. If the agreement between the experimental and calculated PVT data is unsatisfactory, the first step is to critically evaluate the analytical data. If this still does not lead to satisfactory results, an adjustment of the equation of state volume translation parameter is performed. This parameter is chosen because it influences the liquid phase densities without having any influence on the phase equilibrium results. Any additional parameter regression needed is performed by adjustment of the two most sensitive coefficients in the expressions used to determine the equation of state parameters. It is shown that the applied procedure may be used to match experimental PVT data without having a major influence on properties which may be derived from an equation of state, but for which no experimental data exist for the actual composition. Also it is shown that reasonable results are obtained for the measured PVT properties at conditions not used in the regression. Introduction The requirements to a PVT simulation program are not limited to prediction of volumetric properties, phase fractions and saturation points at reservoir conditions. PVT simulation software is also expected to be able to predict the phase behaviour at process plant and transport conditions. Not only saturation points and volumetric properties need to be calculated but also derived properties as for example enthalpies, entropies, heat capacities, Joule- Thomson coefficients and sound velocities. This has to do with the frequent use of PVT simulation packages to generate the PVT property tables needed as input to reservoir and flow simulation programs. Petroleum reservoir fluids consist of thousands of different hydrocarbon constituents. The diversity in chemical structure of the individual components increases with carbon number. It is, therefore, unpractical to analyse for all C7+ components. A standard composition analysis most often stops at either C7+, C10+ or C20+. In PVT simulations the C7+ fraction is usually represented through a number of pseudo-components. Previously the detailed composition of the plus-fraction was not given much attention when selecting the pseudo-components. Though different in their detailed approach, the formerly used characterization procedures had in common that experimental PVT data were needed to be able to assign equation of state parameters to the pseudocomponents. The applied experimental data most often originated from PVT experiments (constant mass expansion, constant volume depletion and differential liberation) carried out at reservoir temperature. One of the most extensive works on how to perform a component pseudorization without estimating the composition of the plus-fraction has been presented by Coats(1). One reason for previously making no attempt to estimate the detailed composition of the plus-fraction was lack of high quality analytical data. Composition analyses to above C7+ were rare and often the information available about the C7+ fraction was limited to its mole fraction. New analytical techniques have made it possible to develop C7+ characterization procedures based on fairly accurate estimations of the molar composition of the plus fraction.

Molecular simulation of the phase behavior of noble gases using accurate two-body and three-body intermolecular potentials

Gibbs ensemble Monte Carlo simulations are reported for the vapor–liquid phase coexistence of argon, krypton, and xenon. The calculations employ accurate two-body potentials in addition to contributions from three-body dispersion interactions resulting from third-order triple-dipole, dipole–dipole–quadrupole, dipole–quadrupole–quadrupole, quadrupole–quadrupole–quadrupole, and fourth-order triple-dipole terms. It is shown that vapor–liquid equilibria are affected substantially by three-body interactions. The addition of three-body interactions results in good overall agreement of theory with experimental data. In particular, the subcritical liquid-phase densities are predicted accurately.

Enhancement of immobilized protease catalyzed dipeptide synthesis by the presence of insoluble protonated nucleophile

α-Chymotrypsin immobilized on celite catalyzing a kinetically controlled dipeptide synthesis reaction in acetonitrile medium showed an odd behavior in response to additions of triethylamine to the reaction mixture. This base is used to deprotonate the nucleophilic reagent, l-alaninamide hydrochloride, in order to increase its nucleophilicity and solubility. However, the enzyme performance is apparently enhanced by additions of triethylamine below one equivalent (in the range 15–20 mm) while the used concentration of nucleophilic reagent is 30 mm. Under these conditions, the initial rate is up to 2.5 times higher and the nucleophile specificity is approximately 30% better than when one equivalent is added. The activating effect on initial rates of dipeptide synthesis was not observed when polyamide was used as support. Unlike polyamide, celite is a material with quite low porosity. Improvement of nucleophile specificity was observed using both supports. It is shown that this activation arises due to the presence of a separate dense liquid phase of insoluble l-alaninamide hydrochloride that intimately contacts with the enzyme preparation, and does not depend on the addition of triethylamine itself. Additions of l-alaninamide hydrochloride improved initial rates of synthesis more than 2.5-fold, and nucleophile specificity more than threefold. The initial rate activation was also observed when using non-porous glass beads to immobilize the enzyme at a loading of 5 mg enzyme g−1 glass but not at 1 mg enzyme g−1 glass when no mass transfer limitations in the immobilized enzyme layer are expected to occur. The results suggest that the presence of the separate phase helps to relieve mass transfer limitations on the system caused by overloading at the supports. One possible mechanism for the initial rate activation might be that the enzyme is partially desorbed from the support particles into the separate phase of nucleophile, and the better nucleophile specificity observed is due to increased local concentrations of the nucleophile within this phase.