Gas-phasePVT properties of 1,1,1,2,3,3-Hexafluoropropane

We have measured the gas-phasePVT properties of 1,1,1,2,3,3,-hexafluoro-propane (R-236ea), which is considered to be a promising candidate for the replacement of 1,2-dichlorotetrafluoroethane (R-114). The measurements have been performed with a Burnett apparatus over a temperature range of 340 390 K and at pressures of 0.10–2.11 MPa. The experimental uncertainties of the measurements were estimated to be within ±0.5 kPa in pressure. ±8 mK in temperature, and ±0.15% in density. A truncated virial equation of state was developed to represent thePVT data and the second virial coefficients were also derived. The saturated vapor densities were also calculated by extrapolating the gas-phase isotherms to the vapor pressures. The critical density estimated from the rectilinear diameter was compared with the experimental value. The purity of the R-236ea sample used in the present measurements was 99.9 mol%. Paper presented at the Fourth Asian Thermophysical Properties Conference, September 5–8, 1995, Tokyo, Japan.     

Thermodynamic and Transport Properties of Liquid HFC-227ea

The thermal conductivity and heat capacity of liquid 1,1,1,2,3,3,3-hepta-fluoropropane (HFC-227ea) have been studied by a high-frequency thermal-wave method over the temperature range of 294 to 345 K at pressures up to 2.8 MPa. The purity of the samples used throughout the measurements is 99.99 mol%. The experimental uncertainties of the thermal conductivity and heat capacity measurements were estimated to be within ±1.5 and ±2%, respectively. The thermal conductivity of HFC-227ea in the liquid phase decreases as temperature increases, while the pressure has an opposite effect.     

Properties of Perfluorobenzene near the Critical Point

The density of vapor and liquid perfluorobenzene along the liquid–vapor coexistence curve has been studied by a gamma-ray attenuation technique over the temperature range from 299 to 517 K. According to measurements, the coordinates of the critical point are T_C = 516.66 ± 0.05 K and ρ _C = 550.5 ± 2 kg · m⁻³. The critical exponent β of the coexistence curve equals 0.343 ± 0.005, which agrees closely with the non-classical value. The results of our measurements were compared with data available in the literature. The height dependence of the density of a two-phase sample was investigated in relation to the temperature and time. These experiments made it possible to determine the isothermal compressibility of liquid and vapor phases near the critical point.Paper presented at the Seventeenth European Conference on Thermophysical Properties, September 5–8, 2005, Bratislava, Slovak Republic.     

Vapor Pressure, Speed of Sound, and PVT-Properties of R-404a in the Vapor Phase

The density (300–363 K, up to 3.5 MPa) and speed of sound (293–373 K, 7.5–480 kPa) in gaseous R-404a have been studied by an isochoric piezometer method and an ultrasonic interferometer, respectively. The pressures of the saturated vapor along the dew line were measured from 298 to 330 K. The experimental uncertainties of the temperature, pressure, density, and speed-of-sound measurements were estimated to be within ±20 mK, ±1.5 kPa, ±0.15%, and ±(0.1–0.2)%, respectively. On the basis of the obtained data, the isobaric molar heat capacity of R-404a was calculated for the ideal-gas state. An eight-coefficient Benedict–Webb–Rubin equation of state has been developed for the gaseous phase of R-404a.     

Vapor+Liquid Equilibrium Measurements and Correlation of the Binary Refrigerant Mixtures Difluoromethane (HFC-32)+1,1,1,2,3,3-Hexafluoropropane (HFC-236ea) and Pentafluoroethane (HFC-125)+1,1,1,2,3,3-Hexafluoropropane (HFC-236ea) at 288.6, 303.2, and 318.2 K

Isothermal vapor–liquid equilibria (VLE) for the binary systems of difluoromethane (HFC-32)+1,1,1,2,3,3-hexafluoropropane (HFC-236ea) and pentafluoroethane (HFC-125)+1,1,1,2,3,3-hexafluoropropane (HFC-236ea) were measured at 288.6, 303.2, and 318.2 K using an apparatus in which the vapor phase was recirculated through the liquid. The phase composition at equilibrium was measured by gas chromatography, based on calibration using gravimetrically prepared mixtures. Both systems show a slight deviation from Raoult's law. The uncertainties in pressure, temperature, and vapor- and liquid-phase composition measurements were estimated to be no more than ±1 kPa, ±0.02 K, and ±0.002 mol fraction, respectively. The data were analyzed using the Carnahan–Starling–DeSantis equation of state.     

Correlation for the Carbon Dioxide and Water Mixture Based on The Lemmon–Jacobsen Mixture Model and the Peng–Robinson Equation of State

Models representing the thermodynamic behavior of the CO₂–H₂O mixture have been developed. The single-phase model is based upon the thermodynamic property mixture model proposed by Lemmon and Jacobsen. The model represents the single-phase vapor states over the temperature range of 323–1074 K, up to a pressure of 100 MPa over the entire composition range. The experimental data used to develop these formulations include pressure–density–temperature-composition, second virial coefficients, and excess enthalpy. A nonlinear regression algorithm was used to determine the various adjustable parameters of the model. The model can be used to compute density values of the mixture to within ±0.1%. Due to a lack of single-phase liquid data for the mixture, the Peng–Robinson equation of state (PREOS) was used to predict the vapor–liquid equilibrium (VLE) properties of the mixture. Comparisons of values computed from the Peng–Robinson VLE predictions using standard binary interaction parameters to experimental data are presented to verify the accuracy of this calculation. The VLE calculation is shown to be accurate to within ±3 K in temperature over a temperature range of 323–624 K up to 20 MPa. The accuracy from 20 to 100 MPa is ±3 K up to ±30 K in temperature, being worse for higher pressures. Bubble-point mole fractions can be determined within ±0.05 for CO₂.     

Thermodynamic Properties of HFC-227ea

The density and speed of sound in gaseous and liquid 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea) have been studied by a -attenuation technique, an ultrasonic interferometer, and an isochoric piezometer method over the temperature range of 273 to 383K at pressures up to 3.5MPa. The purity of the samples used throughout the measurements are 99.99mol%. The pressures of the saturated vapor were measured over the same temperature range. The experimental uncertainties of the temperature, pressure, density, and speed of sound measurements were estimated to be within ±20mK, ±1.5kPa, ±0.2%, and ±(0.15–0.2)%, respectively. On the basis of the obtained data, the isobaric molar heat capacity of HFC-227ea was calculated for the ideal-gas state.     

Thermal conductivity of amorphous Teflon (AF 1600) at high pressure

The thermal conductivity, λ of amorphous Teflon AF 1600 [poly(1,3-dioxole-4,5-difluoro-2,2-bis(trifluoromethyl)-co-tetrafluoroethylene)] has been measured at pressures up to 2 GPa in the temperature range 93–392 K. At 295 K and atmospheric pressure, we obtained λ=0.116, W·m⁻¹·K⁻¹. The bulk modulus was measured up to 1.0 GPa in the temperature range 150–296 K and the combined data yielded the following values ofg=(∂ln λ ∂lnp) _r :2.8±0.2 at 296 K, 3.0±0.2 at 258 K, 3.0±0.2 at 236 K. 3.4±0.2 at 200 K. and 3.4±0.2 at 150 K.     

Measurement and correlation of viscosity of HFC227ea and HFC236fa in the vapor phase

The viscosities of HFC227ea and HFC236fa in vapor phase were measured with an oscillating disk viscometer of the Maxwell type at the temperature range from 300 to 370 K and pressures up to 2.0 MPa. The uncertainty of the reported viscosities was estimated to be within ±2.0% with a coverage factor of k = 2. The experimental viscosities at 0.1 MPa were employed to determine the intermolecular potential parameters with the aid of the extended law of corresponding states developed by Kestin et al. In addition, viscosity models in the vapor phase based on the friction theory at high pressures were correlated for both HFC227ea and HFC236fa.     

Thermal conductivity, heat capacity, and compressibility of atactic poly(propylene) under high pressure

The thermal conductivity λ and the heat capacity per unit volume of atactic poly(propylene) have been measured in the temperature range 90–420 K at pressures up to 1.5 GPa using the transient hot-wire method. The bulk modulus has been measured in the range 200–295 K and up to 0.7 GPa. These data were used to calculate the volume dependence of λ,g=−[∂λ/λ)/(∂V/V)] _T , which yielded the following values for the glassy state (T<256 K at atmospheric pressure): 3.80±0.19 at 200 K, 3.74±0.19 at 225 K, 3.90±0.20 at 250 K, 3.77±0.19 at 271 K, and 3.73±0.19 at 297 K. The resultant value forg of the liquid state was 3.61±0.15 at 297 K. Values forg which are calculated at 295 K, using theoretical models of λ(T), agree to within 12% with the experimental value for the glassy state.     

Isochoric Heat Capacities of Propane + Isobutane Mixtures at Temperatures from 280 to 420 K and at Pressures to 30 MPa

The isochoric heat capacity (c_v) and pressure–volume–temperature-composition (pvTx) properties were measured for propane + isobutane mixtures in the liquid phase and in the supercritical region. The expanded uncertainty (k = 2) of temperature measurements is estimated to be ±13 mK, and that of pressure measurements is ±8 kPa. The expanded relative uncertainty for c_v is ±3.2% for the liquid phase, increasing to ±4.8% for near-critical densities. The expanded uncertainty for density is estimated to be ±0.16%. The present measurements for {xC₃H₈ +(1−x)i-C₄H₁₀} with x = 0.0, 0.498, 0.756, and 1.0, were obtained at 659 state points at temperatures from 270 to 420 K and at pressures up to 30 MPa. The experimental data were compared with a published equation of state. Paper presented at the Fifteenth Symposium on Thermophysical Properties, June 22–27, 2003, Boulder, Colorado, U.S.A.     

Thermodynamic properties of seven gaseous halogenated hydrocarbons from acoustic measurements: CHClFCF3, CHF2 CF3, CF3 CH3, CHF2CH3, CF3CHFCHF2, CF3CH2CF3, and CHF2CF2CH2F

Measurements of the speed of sound in seven halogenated hydrocarbons are presented. The compounds in this study are 1-chloro-1,2,2,2-tetrafluoroethane (CHClFCF₃ or HCFC-124), pentafluoroethane (CHF₂ CF₃ or HFC-125), 1,1,1-trifluoroethane (CF₃CH₃ or HFC-143a), 1,1-difluoroethane (CHF₂CH₃ or HFC-152a), 1,1,1,2,3,3-hexafluoropropane (CF₃CHFCHF₂ or HFC-236ea), 1,1,1,3,3,3-hexafluoropropane (CF₃CH₂CF₃ or HFC-236fa), and 1,1,2,2,3-pentafluoropropane (CHF₂CF₂CH₂F or HFC-245ca). The measurements were performed with a cylindrical resonator at temperatures between 240 and 400 K and at pressures up to 1.0 MPa. Ideal-gas heat capacities and acoustic virial coefficients were directly deduced from the data. The ideal-gas heat capacity of HFC-125 from this work differs from spectroscopic calculations by less than 0.2% over the measurement range. The coefficients for virial equations of state were obtained from the acoustic data and hard-core square-well intermolecular potentials. Gas densities that were calculated from the virial equations of state for HCFC-124 and HFC-125 differ from independent density measurements by at most 0.15%, for the ranges of temperature and pressure over which both acoustic and Burnett data exist. The uncertainties in the derived properties for the other five compounds are comparable to those for HCFC-124 and HFC-125.     

Relative Permittivity and Resistivity of Liquid HFC Refrigerants Under High Pressure

The static relative permittivity (dielectric constant) and the resistivity of HFC-236ea (CF₃–CHF–CHF₂) and HFC-245fa (CF₃–CH₂–CHF₂) in the liquid phase were studied at temperatures from 293 to 343 K and pressures from 0.1 to 50 MPa. The relative permittivity was measured by a concentric-cylinder-type capacitance cell with an LCR meter with an uncertainty of less than 0.1%. The resistivity was measured by a high resistance meter using plane-parallel platinum electrodes installed in a borosilicate glass syringe. It was found that the relative permittivities and the resistivities of liquid HFC-236ea and HFC-245fa at 303 K and 0.101325 MPa are about 5.13 and 6.54 and 1.5×10¹⁰ and 0.2×10¹⁰ ·cm, respectively. The relative permittivity and the resistivity increase monotonically with increasing pressure and decreasing temperature.     

Measurement of surface tension and specific heat of Ni-18.8 at.% Si alloy melt by containerless processing

The surface tension and specific heat of superheated and undercooled Ni-18.8 at.% Si alloy melt have been measured by the oscillating drop method and the drop calorimetry technique in combination with electromagnetic levitation, respectively. The surface tension follows a linear relationship with temperature within the range of 1370–2100 K. The surface tension at the melting temperature and the temperature coefficient are determined to be 1.796 N/m and −3.858 × 10⁻⁴ N/m/K, respectively. The specific heat is determined to be 40.80 ± 1.435 J/mol/K over the temperature range 1296–2000 K. The maximum undercooling of 178 K is achieved in the experiments. Based on the measured data of surface tension and specific heat, the viscosity, solute diffusion coefficient, density and thermal diffusivity of liquid Ni-18.8 at.% Si alloy are calculated.     

A vibrating tube flow densitometer for measurements with corrosive solutions at temperatures up to 723 K and pressures up to 40 MPa

A new version of a vibrating tube flow densitometer has been designed permitting measurements of density differences between two fluids in the temperature range from 298 to 723 K and at pressures up to 40 MPa. The instrument is equipped with a Pt/Rh20 vibrating tube (1.6-mm o.d.) and a Pt/Rh10 transporting tube (1.2-mm o.d.) permitting measurements with highly corrosive liquids. The period of oscillation of the tube is about 7.5 ms, with a typical stability better than 10⁻⁴% over about a 1-h period over the entire temperature interval. The calibration constantK at room temperature is about 530 kg·m⁻³·ms⁻², with a temperature coefficient of approximately −0.13kg·m⁻³·ms⁻²·K⁻¹, and is practically pressure independent. It can be determined by calibration with a reproducibility generally better than 0.1%. The instrument was tested with NaCl(aq) solutions in the temperature range from 373 to 690 K for density differences between sample and reference liquid ranging from 200 to 2 kg·m⁻³; the corresponding errors are believed to be below 0.3 and 5%, respectively. A highly automated temperature control maintains the temperature of the tube stable to within ±0.02 K.     

An Experimental Study of the <Emphasis Type="Italic">pVTx</Emphasis> Properties for Binary Mixtures of HFC-32 and HFC-125 from 258 to 354 K at Pressures up to 16.9 MPa

An experimental study of the pVTx properties for binary mixtures of HFC-32 (CH₂F₂) and HFC-125 (C₂HF₅) was conducted in the range of temperatures from 258 to 354 K, pressures up to 16.9 MPa, densities from 900 to 1400 kg·m⁻³, and compositions from 0 to 1 mole fraction of HFC-32, within the uncertainties of 4.8 mK of temperatures, 1.8 kPa of pressures, 0.022% of densities, and 0.0022 mole fraction of compositions. The present results were determined with the use of a constant-volume apparatus consisting of a cylindrical vessel of approximately 173 cm³ internal volume. The available data including the present measurements are critically compared with the equation of state developed by Tillner-Roth et al., and it is found that, in the liquid region for the range of compositions from 0.1 to 0.4 mole fraction of HFC-32, this equation of state is less reliable because of the lack of experimental data. Paper presented at the Fifteenth Symposium on Thermophysical Properties, June 22–27, 2003, Boulder, Colorado, U.S.A.     

Hot deformation behavior of Ti-15-3 titanium alloy: a study using processing maps,activation energy map,and Zener–Hollomon parameter map

The hot deformation behavior of Ti-15-3 titanium alloy was investigated by hot compression tests conducted in the temperature range 850–1150 °C and strain rate range 0.001–10 s⁻¹. Using the flow stress data corrected for deformation heating, the activation energy map, processing maps and Zener–Hollomon parameter map were developed to determine the optimum hot-working parameters and to investigate the effects of strain rate and temperature on microstructural evolution of this material. The results show that the safe region for hot deformation occurs in the strain rate range 0.001–0.1 s⁻¹ over the entire temperature range investigated. In this region, the activation energy is ~240 ± 5 kJ/mol and the ln Z values vary in range of 13.9–21 s⁻¹. Stable flow is associated with dynamic recovery and dynamic recrystallization. Also, flow instabilities are observed in the form of localized slip bands and flow localization at strain rates higher than 0.1 s⁻¹ over a wide temperature range. The corresponding ln Z values are larger than 21 s⁻¹. The hot deformation characteristic of Ti-15-3 alloy predicted from the processing maps, activation energy map, and Zener–Hollomon parameter map agrees well with the results of microstructural observations.     

Structure and dielectric properties of a new series of pyrochlores in the Ca–Sm–Ti–M–O (M = Nb and Ta) system

The present work investigates the dielectric properties of pyrochlore type oxides, Ca–Sm–Ti–M–O (M = Nb and Ta) in the low frequency region (100 Hz–1 MHz) over the temperature range 30–100 °C. The 1 MHz dielectric constants (K) of these oxides are in the range 23–108 and show low variation with frequency (1 kHz–1 MHz). The temperature coefficient of dielectric constant (TCK) over the temperature range varies from positive to negative values in the range 48 to −107 ppm/°C. Rietveld analysis of the X-ray diffraction data establishes a cubic pyrochlore-type phase in the space group Fd3 m (no. 227).The grain morphology observation by scanning electron microscope shows well sintered grains.     

Dependence of electrical and thermal conductivity on temperature in directionally solidified Sn–3.5 wt% Ag eutectic alloy

Sn–3.5 wt% Ag alloy was directionally solidified upward with a constant growth rate (V = 16.5 μm/s) and a temperature gradient (G = 3.3 K/mm) in a Bridgman-type growth apparatus. The variations of electrical resistivity (ρ) with temperature in the range of 293–476 K for the directionally solidified Sn–3.5 wt% Ag eutectic alloy was measured. The measurements indicate that the electrical resistivity of the directionally solidified Sn–Ag eutectic solder increases with increasing temperature. The variations of thermal conductivity of solid phases versus temperature for the same alloy was determined from the Wiedemann-Franz and Smith-Palmer equations by using the measured values of electrical conductivity. From the graphs of electrical resistivity and thermal conductivity versus temperature, the temperature coefficient of electrical resistivity (α _TCR ) and the temperature coefficient of thermal conductivity (α _TCT ) for the same alloy were obtained. According to experimental results, the electrical and thermal conductivity of Sn–Ag eutectic solder linearly decrease with increasing the temperature. The enthalpy of fusion (ΔH) and the change of specific heat (ΔC _P ) during the transformation at the studied alloy were determined from heating curve during the transformation from eutectic solid to eutectic liquid by means of differential scanning calorimeter (DSC).     

Thermodynamic Properties of 1,1,1,2,3,3,3-Heptafluoropropane

A vapor pressure equation has been developed for 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea) based on previous measurements from 202 to 375K, from which the boiling point of HFC-227ea was determined. Based on the previous pressure–volume–temperature (PVT) measurements in the gaseous phase for HFC-227ea, virial coefficients, saturated vapor densities, and the enthalpy of vaporization for HFC-227ea were also determined. The vapor pressure equation and the virial equation of state for HFC-227ea were compared with the available data. Based on the previous measurements of speed of sound in the gaseous phase for HFC-227ea, the ideal-gas heat capacity at constant pressure and the second acoustic virial coefficient of HFC-227ea were calculated. A correlation of the second virial coefficient for HFC-227ea was obtained by a semiempirical method using the square-well potential for the intermolecular force and was compared with results based on PVT measurements. A van der Waals-type surface tension correlation for HFC-227ea was proposed, based on our previous experimental data by the differential capillary rise method from 243 to 340K.