Theory of quantum nucleation of bubbles in liquid helium

We calculate the rate at which bubbles form by quantum tunneling in liquid helium-3 and helium-4 at negative pressure. We find that quantum tunneling should be observable at temperatures below about 0.1 K in helium-3 and 0.2 K in helium-4, and at pressures close to the critical negative pressure at which the liquid becomes unstable against long wavelength density fluctuations.     

Elementary excitations and sound speed in liquid 4He at negative pressures

No Heading We present neutron scattering measurements of the phonon-roton excitations of superfluid ⁴He at negative pressures in the porous medium MCM-41. The phonon and maxon energies decrease systematically below bulk values as the density is decreased below the bulk value due to stretching of the liquid. The negative internal pressures are estimated by comparison of the observed maxon energies with extrapolation of positive pressure values and from the sound speed. The maximum negative pressure realized, about –5.5 bar, is consistent with surface tension arguments and the MCM-41 pore diameter of 47 Å. Slight broadening of the intrinsic lineshape is observed, suggesting shorter lifetimes of the excitations.PACS numbers: 61.12.Ex; 61.25.Bi; 62.60.+v; 68.03.Cd; 68.03.Kn; 67.40.Mj     

Water and Gallium at Absolute Negative Pressures. Loci of Maximum Density and of Melting

Several physical properties of liquids as well as those of the coexistence between liquid and solid can be determined at absolute negative pressures. Examples for this include thermal pressure coefficients, loci of temperature of maximum density, melting lines, speed of propagation of low-intensity sound waves, and (p, T, x) conditions of occurrence of liquid/liquid phase separation. Three model temperature-pressure cycles, which allow for the measurement of temperature-pressure conditions of the occurrence of maxima of liquid density, negatively sloped fusion lines, and the upper critical solution temperature (UCST) of liquid solutions in these metastable regimes are described. A new apparatus for measuring negative pressures was developed. The temperature and pressure are determined within an uncertainty of ±0.05°C and ±5 bar, respectively. Water and heavy water have been used as testing systems with respect to the location of their temperatures of maximum density (TMD) loci. Empirical equations of state whose parameters have been fitted to experimental data located in the normal positive pressure region have proven to extrapolate well to the negative pressure regime. Furthermore, an attempt was made to use SAFT in order to provide a more theoretically founded framework. Preliminary results for gallium have shown that a TMD exists 45 K inside the supercooled regime, and that the continuation of its melting line down to –80 bar evolves with a slope of –515±25 bar·K^–1.     

Nucleation of bubbles in liquid helium

We give a brief survey of experiments that have been performed to study the nucleation of bubbles in liquid helium at negative pressures.     

The Creation of Long-Lived Multielectron Bubbles in Superfluid Helium

Multielectron bubbles (MEBs) in liquid helium were first observed in the late 1970s, but their properties have never been explored experimentally due to their short lifetimes. MEBs in liquid helium are predicted to have dynamic instabilities for zero or positive pressures, and stability for negative pressures. We report the production of long-lived MEBs in a novel cell filled with helium at static negative pressures. MEBs were extracted from the vapor sheath of a heated filament loop embedded in the superfluid helium and were observed by high-speed photography as they rose in the helium under buoyant forces. In earlier studies we found that MEBs created in this way had large amplitude oscillations and were unstable to decay. By creating MEBs at temperatures just under the lambda point, these oscillations are rapidly damped and the MEBs relax toward a spherical shape and stability as they rise in the helium.     

The density of petroleum products in a wide range of parameters of state

The density of liquid products of catalytic cracking (CC) and viscosity breaking (VB) is measured in the temperature range from 293 K to 473 K at atmospheric pressure and at pressures elevated to 60 MPa. The resultant data are generalized along with experimental data on the density of directly distilled liquid petroleum fractions and commercial petroleum products. Dependences are obtained, which are suitable for determining the density of a wide range of petroleum products in view of the special features of their hydrocarbon composition.     

Speed of Sound and Some Thermodynamic Properties of Liquid Methylcyclopentane and Butylcyclohexane in a Wide Range of Pressure

Ultrasonic velocity measurements were performed on liquid methylcyclopentane and butylcyclohexane at pressures from atmospheric up to 150 MPa in the temperature range from 293 to 373 K using a pulse echo technique operating at 3 MHz. The data were used to evaluate various thermophysical properties such as density, and isentropic and isothermal compressibilities up to 150 MPa with the help of additional density measurements.     

Compressed Liquid Densities and Helmholtz Energy Equation of State for Fluoroethane (R161)

In this study, compressed liquid densities of Fluoroethane (R161, CAS No. 353-36-6) were measured using a high-pressure vibrating-tube densimeter over the temperature range from (283 to 363) K with pressures up to 100 MPa. A Helmholtz energy equation of state for R161 was developed from these density measurements and other experimental thermodynamic property data from the literature. The formulation is valid for temperatures from the triple point temperature of 130 K to 420 K with pressures up to 100 MPa. The approximate uncertainties of properties calculated with the new equation of state are estimated to be 0.25 % in density, 0.2 % in saturated liquid density between 230 K and 320 K, and 0.2 % in vapor pressure below 350 K. Deviations in the critical region are higher for all properties. The extrapolation behavior of the new formulation at high temperatures and high pressures is reasonable.     

Measurements and Correlations of cis-1,3,3,3-Tetrafluoroprop-1-ene (R1234ze(Z)) Subcooled Liquid Density and Vapor-Phase PvT

22 182 compressed liquid density data and 98 vapor-phase PvT data for cis-1,3,3,3-tetrafluoroprop-1-ene (R1234ze(Z)) are presented. The compressed liquid density data are for nine isotherms evenly spaced approximately from 283 K to 363 K for pressures from close to saturation to 35 MPa, and the vapor-phase PvT data are for seven isochores for temperatures approximately from 303 K to 375 K for pressures approximately from 82 kPa to 436 kPa. In addition, a saturated liquid density correlation, a Tait correlation for the compressed liquid density data, and a Martin–Hou equation of state for the vapor-phase PvT data are presented.     

Thermal conductivity of oct-1-ene in the temperature range 307 to 360 K at pressures up to 0.5 GPa

New measurements of the thermal conductivity of liquid oct-1-ene in the temperature range 307 to 360 K at pressures up to 0.5 GPa have been performed. The experimental data have an estimated uncertainty of ±0.3%. Within the limited range of pressures for which data for the density of the liquid are available, it has proved possible to represent all of the thermal conductivity results by means of a single equation with just one temperature-dependent parameter. This representation is based on the ideas of the hard-sphere theory of fluids and is consistent with that employed earlier for alkanes.     

Micromechanical and thermodynamical aspects of environmental crazing

The present study aims 1) to investigate theoretically the relation between the craze microstructure and the basic materials parameters such as the yield stress and the surface energy and 2) to provide a detailed thermodynamic treatment of a single isolated craze in glassy polymer tested in an aggressive liquid environment. Based on the assumption that the craze tip is somewhat blunted by small scale yielding and on the Taylor meniscus instability as the mechanism responsible for the propagation of the leading edge of the craze, the detailed micromechanical analysis is used to provide estimates of the critical opening displacement of the craze for growth initiation, mean fibril spacing, mean fibril diameter and fibril volume fraction at the craze tip. The influence of aggressive liquid environments on the yield stress and the surface energy is discussed together with predicted changes in the craze microstructure. The thermodynamic analysis starts with the recognition that induced high negative pressures around the craze tip can increase the solubility of a liquid at this site by several orders of magnitude. As a consequence the local density of thermodynamic potential drops significantly. This unbalanced fall in thermodynamic potential provides an additional driving force for the craze advance. It is shown that a corresponding release of external load is required to preserve the overall balance of the specimen with craze.     

Vapor pressure and liquid and gas densities of 2,2,2-trifluoroethanol

Forty-three vapor pressures were measured for temperatures from the normal boiling point to the critical point. These data were obtained with a phase-equilibrium cell designed for precise static measurements at pressures up to 20 MPa. The cell is located within an oil-operated thermostatic bath which provides a homogeneous temperature field with variations less than ±1 mK. The vapor pressure data were fitted to a Wagner-type equation. Sixty-two liquid densities were measured on seven isotherms between 20 and 140°C for pressures up to 16 MPa. These measurements were carried out with a precision density meter operating on a vibrational technique. Sixty-nine gas-PVT triples were determined from Burnett expansion series on five isotherms between 140 and 200°C for pressures up to the saturation line. In all experiments, temperature measurements were made with platinum resistance thermometers. Precise pressure measurements were performed using a mercury column of 6-m height and a standard deadweight gauge for the higher pressures.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

An analytical equation of state for refrigerants

The liquid density of halogenated hydrocarbons has been calculated using an analytical equation of state. The temperature-dependent parameters of the equation of state have been calculated using our previous corresponding-states correlation based on the normal boiling point constants. In this work, it is shown that the equation of state for halogenated paraffins could be expressed in terms of the minimum input information, namely the normal boiling point temperature and the liquid density at the normal boiling point. The equation of state has been employed to calculate the liquid density of a great number of refrigerants both at saturation and compressed states, over a wide range of temperatures and pressures. A comparison of the predicted results with experimental data shows that the agreement is quite good.     

Carbon monoxide compressibility data from 100 to 300 K; derived virial coefficients,orthobaric densities,and heats of vaporization

Experimental densities of carbon monoxide are tabulated along experimental pseudoisochores from 100 through 300 K at pressures to 35 MPa. Virial coefficient data on isotherms are derived from 120 through 300 K and are formulated vs temperature by including data from other sources. Vapour pressures from other sources are formulated and used to derive some orthobaric vapour densities via the virial equation; and orthobaric vapour and liquid densities via isochoric Pp T data. All available orthobaric vapour and liquid density data are then formulated and are used to derive and to formulate the heats of vaporization.     

Dielectric constant and polarizability of saturated and compressed fluid methane

Accurate measurements of the dielectric constant of methane have been made on the saturated liquid from near the triple point to 188 K and on the compressed fluid along selected isotherms from 100 K to 300 K and at pressures to 345 bar. The data are combined with accurate densities to obtain the molar polarizability and its dependence on density and temperature. The density range examined extends to nearly three times the critical density. The molar polarizability is found to increase initially with density and then decrease in qualitative agreement with theoretical predictions and the behaviour of other fluids.     

New Fundamental Equations of State with a Common Functional Form for 2,3,3,3-Tetrafluoropropene (R-1234yf) and <Emphasis Type="Italic">trans</Emphasis>-1,3,3,3-Tetrafluoropropene (R-1234ze(E))

New fundamental equations of state explicit in the Helmholtz energy with a common functional form are presented for 2,3,3,3-tetrafluoropropene (R-1234yf) and trans-1,3,3,3-tetrafluoropropene (R-1234ze(E)). The independent variables of the equations of state are the temperature and density. The equations of state are based on reliable experimental data for the vapor pressure, density, heat capacities, and speed of sound. The equation for R-1234yf covers temperatures between 240 K and 400 K for pressures up to 40 MPa with uncertainties of 0.1 % in liquid density, 0.3 % in vapor density, 2 % in liquid heat capacities, 0.05 % in the vapor-phase speed of sound, and 0.1 % in vapor pressure. The equation for R-1234ze(E) is valid for temperatures from 240 K to 420 K and for pressures up to 15 MPa with uncertainties of 0.1 % in liquid density, 0.2 % in vapor density, 3 % in liquid heat capacities, 0.05 % in the vapor-phase speed of sound, and 0.1 % in vapor pressure. Both equations exhibit reasonable behavior in extrapolated regions outside the range of the experimental data.     

A vibrating-wire densimeter for liquids at high pressures: The density of 2,2,4-trimethylpentane from 298.15 to 348.15 K and up to 100 MPa

A new apparatus for the measurement of liquid densities at high pressures is presented. The instrument is a development of a vibrating-wire densimeter described earlier and uses the buoyancy force exerted by the sample fluid on an immersed buoy to alter the tension of a wire from which it is suspended. The tension of the wire is related to its resonant frequency under steady-state transverse vibrations through a rigorous theoretical model which includes a complete analysis of the hydrodynamic effect of the fluid surrounding the wire. The present instrument uses a new design for the measuring cell with the purpose of relieving the degeneracy of perpendicular oscillation modes of the vibrating wire. The modifications lead to a significant increase in the precision of the results. Tests performed on the new apparatus and the operating procedure used, which requires the determination of one cell parameter from one density datum at atmospheric pressure, are described. New results for the density of liquid 2,2,4-trimethylpentane at temperatures from 298.15 to 348.15 K and pressures up to 100 MPa are presented. The data obtained have a precision of ±0.05% at a 2a level and an estimated accuracy of approximately ±0.1%.     

Development of a Magnetic Suspension Densimeter and Measurement of the Density of Toluene

The development of a magnetic suspension densimeter that has been built for measurement of the density of compressed liquid at pressures up to 30 MPa in the temperature range 20 to 150°C is described. The densimeter was first built by the author and his coworkers at NIST. We describe here further improvements made on a second system built at NMIJ based on the same principle. The densimeter uses a small coil suspended from an electronic balance. Within the coil is placed a sample cell in which the pressurized sample and a buoy, which is a permanent magnet, are enclosed. For measurement of density, balance readings are recorded (1) with the buoy at rest and (2) with the buoy in magnetic suspension. The measurement procedure is basically a hydrostatic weighing, which is simpler than those of conventional magnetic densimetry. As an example, measurements of toluene density performed as part of an inter-laboratory comparison are presented. The data agreed with reliable literature values to within a few hundredths of a per cent.