The density of 1,1-dichloro-1-fluoroethane (HCFC 141b)

In this Note we present the density of HCFC 141b, measured between 293.15 and 300.15 K, with an mechanical oscillator densimeter, with an uncertainty of 0.007%. The results are compared with the densities estimated by the reduced hard-sphere-DeSantis equation of state and with the experimental data obtained by several authors.     

Measurement of the viscosity of HCFC 123 in the temperature range 233–418 K and at pressures up to 20 MPa

The viscosity of HCFC 123 was measured over the range of temperature from 223 to 418 K and pressure up to 20 MPa. The experimental method was that of the capillary flow and a closed-circuit high-pressure viscometer was used. The sample fluid was circulated through a Pyrex glass capillary from a high-pressure plunger system. The constant of the Pyrex glass capillary was calibrated against the reference standard, pure water. The viscosity of the sample was calculated from the flow rate, the pressure drop at the capillary, and the capillary constant using the Hagen-Poiseuille equation. Measurements were made on seven isotherms. In the case of the transpiration method, the density is needed for calculation of the viscosity from the kinematic viscosity. The available density data of HCFC 123 are less reliable than those for CFC 11. Therefore, uncertainty in the viscosity of HCFC 123 is larger, although the measured kinematic viscosity itself has a reproducibility of 0.1 %. HCFC 123 is proposed as an alternative to CFC 11. Comparisons of the data for these two substances show that the viscosity of HCFC 123 is similar in magnitude to that of CFC 11 at temperatures around 350 K, higher at lower temperatures, and lower at higher temperatures. The pressure gradients for these two corresponding substances are similar over the entire temperature range.     

Saturated liquid densities and bubble-point pressures of the binary HFC 152a+HCFC 142b system

Forty-eight sets of the saturated liquid densities and bubble-point pressures of the binary HFC 152a + HCFC 142b system were measured with a magnetic densimeter coupled with a variable-volume cell. The measurements obtained at four compositions, 20, 40, 60, and 80 wt%, of HFC 152a cover a range of temperatures from 280 to 400 K. The experimental uncertainties in temperature, pressure, density, and composition were estimated to be within ±15mK, ±20kPa, ±0.2%, and between –0.14 and ±0.01 wt% HFC 152a (–0.01 and + 0.14 wt% HCFC 142b), respectively. The purities of the samples were 99.9 wt% for HFC 152a and 99.8 wt% for HCFC 142b. A binary interaction parameter, k _ij , in the Peng-Robinson equation of state was determined as a function of temperature for representing the bubble-point pressures. On the other hand, two constant binary-interaction parameters, k _ij and l _ij , were introduced into the mixing rule of the Hankinson-Brobst-Thomson equation for representing the saturated liquid densities.     

A Two-Sinker Densimeter for Accurate Measurements of the Density of Natural Gases at Standard Conditions

A special reference densimeter has been developed for accurate measurements of densities of natural gases and multicomponent gas mixtures at standard conditions of temperature and pressure (T _s = 273.15 K and p _s = 0.101325 MPa). The densimeter covers the range from 0.7 kg · m^?3 to 1.3 kg · m^?3; the total measurement uncertainty in density is 0.020 % (95 % level of confidence). The measurement principle used is the two-sinker method, which is based on the Archimedes buoyancy principle. The certified calibration laboratory of E.ON Ruhrgas AG, Germany, uses this densimeter to verify the standard densities of certified calibration gases (binary and multicomponent gas mixtures). Moreover, the densimeter is used to determine the compositions of commercially available binary gas mixtures with a small uncertainty of (0.01–0.03) mol%.     

High-Pressure Viscosity and Density Measurements for the Asymmetric Binary System cis-Decalin +2,2,4,4,6,8,8-Heptamethylnonane

Measurements of the viscosity and density of seven binary mixtures composed of cis-decahydronaphthalene (cis-decalin)+2,2,4,4,6,8,8-heptamethylnonane along with the pure compounds have been performed in the temperature range 293.15 to 353.15 K and at pressures up to 100 MPa. The viscosity was measured with a falling-body viscometer, except at 0.1 MPa where a classical capillary viscometer (Ubbelohde) was used. The experimental uncertainty for the measured viscosities is less than 2% at high pressures. The density was measured up to 60 MPa with a resonance densimeter and extrapolated with a Tait-type relationship up to 100 MPa. The uncertainty for the reported densities is less than 1 kgm^–3. The measured data have been used in an evaluation of the simple mixing laws of Grunberg and Nissan and of Katti and Chaudhri, which require only the density and viscosity of the pure compounds. This evaluation showed that these mixing laws can accurately represent the viscosity of this asymmetric binary system within an average absolute deviation of 1%.     

PρT Measurements of Nonafluorobutyl Methyl Ether and Nonafluorobutyl Ethyl Ether Between 283.15 and 323.15 K at Pressures Up to 40 MPa

In this paper, experimental densities for nonafluorobutyl methyl ether and nonafluorobutyl ethyl ether from 283.15 to 323.15 K at pressures up to 40 MPa are reported. The density measurements were performed by means of a high pressure vibrating tube densimeter. Data reliability was checked by comparing experimental results obtained for tetrachloromethane—whose density is close to those of the fluids studied—with recommended literature data. Furthermore, the isobaric thermal expansion, isothermal compressibility, and internal pressure have been calculated from these density data.     

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.     

The dielectric constant of liquid HFC 134a and HCFC 142b

This paper presents measurements of the dielectric constant of HFC 134a and HCFC 1426, as a function of pressure and temperature, in the temperature range from 200 to 300 K and pressures up to 20 M Pa, using a direct capacitance method, The samples used had a stated purity of 99.8 and 99.9%, respectively, The values of the dielectric constant have a precision of 0.01 % and an accuracy of 0.1%, The data obtained were correlated as a function of density and pressure, The theory developed by Vedam et al,, based on the Eulerian strain. and the Kirkwood equation for the variation of modified molar polarization with temperature and density were applied to analyze the data and to obtain the dipole moment of both refrigerants in the liquid state.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

Performance of an HCFC22-based vapour absorption refrigeration system

A single-stage vapour absorption refrigeration system (VARS) is tested with monochlorodifluoromethane (HCF22) as refrigerant and different absorbents: dimethylether of tetraethylene glycol (DMETEG) and dimethyl acetamide (DMA). The influence of generator temperatures in the range 75–95°C, which represents low-grade heat sources, is studied. Cooling water temperatures were varied between 20 and 30°C. Two cases of cooling water flow paths are considered, i.e. water entering either absorber or condenser, which are connected in series. For HCFC22-DMETEG, COP values in the range 0.2–0.36 and evaporator temperatures between 0 and 10°C are obtained. For HCF22-DMA, COP values in the range 0.3–0.45 and evaporator temperatures between −10 and 10°C are obtained. It is observed that HCFC22-DMETEG can work at lower heat source temperatures than HCFC22-DMA. However, at the same operating conditions HCFC22-DMA is better from the viewpoints of circulation ratio and COP. Experiments also show that at low heat source temperature, cooling water temperature has strong influence on circulation ratio but does not affect COP significantly. Preferably, cooling water should first flow through the condenser and then through the absorber in order to achieve improved overall performance.     

Thermal conductivity of normal pentane in the temperature range 306–360 K at pressures up to 0.5 GPa

This paper reports the results of new, absolute measurements of the thermal conductivity of normal pentane in the temperature range 306 to 360 K at pressures up to 0.50 GPa. The experimental data have an estimated uncertainty of ±0.3%. The density dependence of the thermal conductivity along all of the isotherms cannot be represented by a common equation within its estimated uncertainty. Nevertheless, such a universal equation does provide a simple method of correlating the complete set of data with an error of no more than ±2.5%.     

Gaseous thermal conductivity of difluoromethane (HFC-32), pentafluoroethane (HFC-125), and their mixtures

The gaseous thermal conductivity of dilluoromethane (HFC-32). pentalluoroethane (HFC-125). and their binary mixtures was measured with a transient hot-wire apparatus in the temperature ranges 283–333 K at pressures up to saturation. The uncertainty of the data is estimated to be within I %. The thermal conductivity as a function of composition of the mixtures at constant pressure and temperature is found to have a small maximum near 0.3–0.4 mole fraction of HFC-32. The gaseous thermal-conductivity data obtained for pure HFC-32 and HFC-125 were correlated with temperature and density together with the liquid thermal-conductivity data from the literature, based on the excess thermal-conductivity concept. The composition dependence of the thermal conductivity at a constant temperature is represented with the aid of the Wassiljewa equation.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado. U.S.A.     

Compressed Liquid and Supercritical Densities of 1,1,1,2,3,3,3-Heptafluoropropane (R227ea)

Densities of 1,1,1,2,3,3,3-heptafluoropropane (R227ea) have been measured with a computer-controlled high-temperature high-pressure vibrating-tube densimeter system (DMA-HDT) in the sub- and supercritical states. The densities were measured at temperatures from 278 to 473 K and pressures up to 30 MPa (overall 257 data points), whereby a density range between 285 and 1588 kgm^–3 was covered. The uncertainty in the density measurement was estimated to be better than ±0.2 kgm^–3. The experimental data of R227ea were correlated with a virial-type equation of state (EoS) and compared with published data. A comparison is also made with a recent wide-range dedicated equation of state for R227ea.     

A Liquid Density Standard Over Wide Ranges of Temperature and Pressure Based on Toluene

The density of liquid toluene has been measured over the temperature range −60 °C to 200 °C with pressures up to 35 MPa. A two-sinker hydrostatic-balance densimeter utilizing a magnetic suspension coupling provided an absolute determination of the density with low uncertainties. These data are the basis of NIST Standard Reference Material® 211d for liquid density over the temperature range −50 °C to 150 °C and pressure range 0.1 MPa to 30 MPa. A thorough uncertainty analysis is presented; this includes effects resulting from the experimental density determination, possible degradation of the sample due to time and exposure to high temperatures, dissolved air, uncertainties in the empirical density model, and the sample-to-sample variations in the SRM vials. Also considered is the effect of uncertainty in the temperature and pressure measurements. This SRM is intended for the calibration of industrial densimeters.     

Density and Viscosity of Mixtures of n-Hexane and 1-Hexanol from 303 to 423 K up to 50 MPa

Experimental results for the density and viscosity of n-hexane+1-hexanol mixtures are reported at temperatures from 303 to 423 K and pressures up to 50 MPa. The binary mixture was studied at three compositions, and measurements on pure 1-hexanol are also reported. The two properties were measured simultaneously using a single vibrating-wire sensor. The present results for density have a precision of ±0.07% and an estimated uncertainty of ±0.3%. The viscosity measurements have a precision of ±1% and an estimated uncertainty of ±4%. Representations of the density and viscosity of the mixture as a function of temperature and pressure are proposed using correlation schemes.     

An Automated Vibrating-Tube Densimeter for Measurements of Small Density Differences in Dilute Aqueous Solutions

The core of the automated apparatus is a high-temperature high-pressure densimeter with a metal vibrating tube designed for accurate flow measurements of densities of liquids in the temperature range from 298 to 573 K and at pressures from 0.1 MPa up to 30 MPa. The densimeter is being employed for a study of dilute solutions of aqueous solutions of organic substances where the density difference {solution–water} is a primary experimental quantity. Consequently, partial molar volumes of solutes at infinite dilution in water are evaluated from the measured data. Two sampling sections are connected in series in the filling line of the densimeter. One of them is employed for manual filling of the measured sample into a sampling loop using a syringe. The other section allows fully automated measurement of up to 12 samples in one run. The recorded data are evaluated after the automated run is completed.     

Nucleate boiling heat transfer coefficients of pure halogenated refrigerants

Nuclate pool boiling heat transfer coefficients (HTCs) of HCFC123, CFC11, HCFC142b, HFC134a, CFC12, HCFC22, HFC125 and HFC32 on a horizontal smooth tube of 19.0 mm outside diameter have been measured. The experimental apparatus was specially designed to accomodate high vapor pressure refrigerants such as HFC32 and HFC125 with a sight glass. A cartridge heater was used to generate uniform heat flux on the tube. Data were taken in the order of decreasing heat flux from 80 to 10 kW m⁻² with an interval of 10 kW m⁻² in the pool of 7 °C. Test results showed that HTCs of HFC125 and HFC32 were 50–70% higher than those of HCFC22 while HTCs of HCFC123 and HFC134a were similar to those of CFC11 and CFC12 respectively. It was also found that nucleate boiling heat transfer correlations available in the literature were not good for certain alternative refrigerants such as HFC32 and HCFC142b. Hence, a new correlation was developed by a regression analysis taking into account the variation of the exponent to the heat flux term as a function of reduced pressure and some other properties. The new correlation showed a good agreement with all measured data including those of new refrigerants of significantly varying vapor pressures with a mean deviation of less than 7%.     

Experimental liquid densities of cis-1,3,3,3-tetrafluoroprop-1-ene (R1234ze(Z)) and trans-1-chloro-3,3,3-trifluoropropene (R1233zd(E))

In this work, liquid phase densities of two fourth generation refrigerants, cis-1,3,3,3-tetrafluoroprop-1-ene R1234ze(Z) and trans-1-chloro-3,3,3-trifluoropropene R1233zd(E), are measured. The densities have been measured using a vibrating tube densimeter over the temperature range from 273.15 K to 333.15 K for pressures up to 30 MPa. For both fluids, the expanded uncertainty at a confidence level of 95% in the density measurements is estimated to be 0.07% over the entire T–p range measured.     

Molecular properties of alternative refrigerants derived from dielectric-constant measurements

A review of the current work in Lisbon on the measurement of the dielectric constant of the liquid phase of some environmentally acceptable refrigerants proposed as alternative replacements of the chlorofluorocarbons (CFCs), responsible for the destruction of the ozone layer, is presented. Measurements on HCFC 141b, HCFC 142b, HCFC 123, HFC 134a, HFC 152a, and HFC 32 samples of stated purities of 99.8 mass% or better were performed as a function of pressure and temperature, in the temperature range from 200 to 300 K and at pressures up to 20 MPa. The ratio of the capacitances of a cell filled with the sample and under vacuum was measured with a direct capacitance method. The dielectric-constant measurements have a repeatability of 0.003% and an accuracy of 0.1%. The theory developed by Vedam et al. based on the Eulerian Strain and the Kirkwood equation for the variation of the modified molar polarization with temperature and density were applied to obtain the dipole moments of the refrigegrants in the liquid state, to obtain a physical insight of the molecular behavior, and to understand the equilibrium configuration of these liquids. Invited paper presented at the Fourth Asian Thermophysical Properties Conference. September 5–8, 1995, Tokyo, Japan.     

Micro-Raman densimeter for CO2 inclusions in mantle-derived minerals

We investigated the applicability of Raman microprobe spectroscopy for determining the density of CO2 in fluid inclusions in minerals of mantle-derived xenolith samples. A separation (delta) between two Raman bands of CO2 due to Fermi resonance can be a reliable densimeter for CO2 fluid. The relationship between the density of CO2 (g/cm3) and delta (cm-1) can be expressed as: d = -0.03238697 delta 3 + 10.08428 delta 2 - 1046.189 delta + 36163.67. This equation was obtained from the Raman data on CO2 fluid with densities from 0.1 to 1.21 g/cm3, including super critical fluids at 58-59 degrees C. The delta value was constant with increasing temperature from room temperature to 200 degrees C. This indicates that the Raman densimeter is not affected by a possible rise in temperature, an artifact induced by the high flux of the incident laser. The minimum size of measurable inclusions is 1 micron, and the precision in the determination of delta is 0.1 cm-1, corresponding to 0.02 g/cm3 for inclusions of 1 micron in size. The precision can be better for larger inclusions. The micro-Raman densimeter can determine the density of CO2 fluid inclusions over a wide range. In particular, densities of gas and mixtures of gas and liquid phases, which cannot be measured by microthermometry, can be determined.     

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.