Hironobu Kubota

Volumetric behavior of pure alcohols and their water mixtures under high pressure

The specific volumes of C1-C4 alcohols and binary mixtures of water with methanol, ethanol, 1-propanol, 2-propanol, and 2-methyl-2-propanol are presented as functions of temperature, pressure, and composition. The measurements were carried out using a modified Adams piezometer and a high-pressure burette method in a temperature range from 283.15 to 348.15 K at pressures up to 350 MPa. The uncertainties in the specific volume obtained are estimated to be less than 0.09%. The specific volumes of the pure alcohols and their mixtures with water are found to decrease monotonously with increasing pressure. The numerical P-V relations at each temperature and composition are correlated satisfactorily as a function of pressure by the Tait equation. Definite inflections appear on the isobars of isothermal compressibility or partial molar volume versus composition of alcohol + water mixtures.

Thermal conductivity and density of toluene in the temperature range 273–373 K at pressures up to 250 MPa

New experimental data on the thermal conductivity and the density of liquid toluene are presented in the temperature range 0–100°C at pressures up to 250 MPa. The measurements of thermal conductivity were performed with a transient hot-wire apparatus on an absolute basis with an inaccuracy less than 1.0%. The density was measured with a high-pressure burette method with an uncertainty within 0.1%. The experimental results for both properties are represented satisfactorily by the Tait-type equations, as well as empirical polynomials, covering the entire ranges of temperature and pressure. Furthermore, it is found that simple relations exist between the temperature dependence of thermal conductivity and the thermal expansion coefficient, and also between the pressure dependence of thermal conductivity and the isothermal compressibility, as are suggested theoretically.

Viscosity and density of binary mixtures of cyclohexane with n-octane, n-dodecane, and n-hexadecane under high pressures

The viscosity and density of three binary mixtures of cyclohexane with n-octane, n-dodecane, and n-hexadecane have been measured at 298, 323, and 348 K at pressures up to 150 MPa or freezing pressures. The measurements of the viscosity were performed by a torsionally vibrating crystal viscometer on a relative basis using benzene and cyclohexane as reference materials. The density was measured using a high-pressure burette apparatus. The uncertainties of the measurements are estimated to be less than 2% for viscosity and 0.1% for density, respectively. The effects of temperature, pressure, density, and composition on the viscosity are discussed. Applicabilities of several empirical correlating equations to the viscosity data were examined.

Viscosity of (water + alcohol) mixtures under high pressure

New experimental viscosity data are presented for aqueous solutions of methanol, ethanol, 1-propanol, 2-propanol, and 2-methyl-2-propanol (t-butyl alcohol) in the temperature range from 283 to 348 K and pressures up to 120 MPa. The viscosity measurements were performed using a falling-cylinder viscometer on a relative basis with an uncertainty of less than 2%. The viscosity of pure alcohols and aqueous solutions is found to increase almost linearly with increasing pressure, whereas that of water decreases slightly with pressure at temperatures below 298 K. As for the composition dependence of the viscosity, a distinct maximum appears near 0.3–0.4 mole fraction of alcohol on all isobars at each temperature. The viscosity maximum shifts gradually to a higher alcohol concentration with increasing temperature and pressure. The isobars of aqueous 2-propanol and 2-methyl-2-propanol solutions have another shallow minimum near 0.9 mole fraction of alcohol below 323 K. The experimental results were analized empirically by a Tait-type equation and a free-volume theory. It was found that the isothermal viscosity data were satisfactorily correlated by these equations as functions of pressure and composition or of density and composition.

Vapor pressures of new fluorocarbons

The vapor pressures of four fluorocarbons have been measured at the following temperature ranges: R123 (2,2-dichloro-l,l,l-trifluoroethane), 273–457 K; R123a (1,2-dichloro-1,1,2-trifluoroethane), 303–458 K; R134a (1,1,1,2-tetrafluoroethane), 253–373 K; and R132b (l,2-dichloro-l,l-difluoroethane), 273–398 K. Determinations of the vapor pressure were carried out by a constant-volume apparatus with an uncertainty of less than 1.0%. The vapor pressures of R123 and R123a are very similar to those of R11 over the whole experimental temperature range, but the vapor pressures of R134a and R132b differ somewhat from those of R12 and R113, respectively, as the temperature increases. The numerical vapor pressure data can be fitted by an empirical equation using the Chebyshev polynomial with a mean deviation of less than 0.3 %.

Thermal conductivity of fourteen liquids in the temperature range 298–373 K

New experimental data on the thermal conductivity of 14 organic liquids at atmospheric pressure are presented in the temperature range from 25 to 100°C. The liquids measured are five n-alkanes (C6, C7, C8, C10, C12), cyclohexane, six aromatic hydrocarbons (benzene, ethylbenzene, o-, m-, p-xylenes, isopropylbenzene) and two phenyl halides (chloro-, bromobenzenes). The measurements were performed by a transient hot-wire method on a relative basis. The thermal conductivity of toluene, which was selected as a reference liquid, was determined on an absolute basis with another transient apparatus. The precision of the present experimental results is within ±1.2%. The uncertainty of the thermal conductivity values is estimated to be within ±2%; this includes the uncertainty of the values of toluene as the reference liquid. The experimental results for each liquid are represented satisfactorily by a linear equation in temperature. At a reduced temperature T/Tc=0.5, thermal conductivity has a simple relation with the molar density for each homologous series of liquids.

Thermodynamic properties of 1-chloro-1,2,2,2-tetrafluoroethane (R124)

The critical temperature and pressure, vapor pressure, and PVT relations for gaseous and liquid 1-chloro-1,2,2,2-tetrafluoroethane (R124) were determined experimentally. The vapor pressure was measured in the temperature range from 278.15 K to the critical temperature. The PVT measurements were carried out using two types of volumeters in the temperature range from 278.15 to 423.15 K, at pressure up to 100 MPa. The numerical PVT data of gaseous state are fitted as a function of density to a modified Benedict-Webb-Rubin equation. The pressure-volume relations of the liquid at each temperature are correlated satisfactorily as a function of pressure by the Tait equation. The critical density and saturated vapor and liquid densities are also determined and some of the thermodynamic properties are derived from the experimental results.

Viscosity of aqueous solutions of 1,2-ethanediol and 1,2-propanediol under high pressures

New experimental data on the viscosity of aqueous solutions of 1,2-ethanediol (ethylene glycol) and 1,2-propanediol (propylene glycol) are presented at 298 and 323 K under pressures up to 120 MPa. The measurements were performed by a falling-cylinder viscometer on a relative basis with an uncertainty of less than ±2%. The viscosity of these aqueous solutions at a constant temperature and pressure increases monotonously with increasing concentrations of diols (glycols) and is slightly lower than the mole fraction average value at each composition. The viscosity also increases almost linearly with pressure at a constant temperature and composition. The pressure coefficient of the viscosity, (∂η/∂P)T,x, increases with decreasing temperature and increasing concentrations of diols. The experimental results are correlated with pressure, density, and composition by several empirical equations.

Thermal conductivity of five normal alkanes in the temperature range 283-373 K at pressures up to 250 MPa

Experimental data on the thermal conductivity of five liquid n-alkanes-hexane, heptane, octane, decane, and dodecane-are presented in the temperature range from 283 to 373 K at pressures up to 250 MPa or the freezing pressures. The measurements were performed on an absolute basis by an automated transient hot-wire apparatus. The uncertainty of the reported data is estimated to be within ±1%. The thermal conductivity of each alkane decreases almost linearly with rising temperature at a constant pressure and increases with increasing pressure at a constant temperature. Both the temperature coefficient of the thermal conductivity ¦(∂λ/∂T)p¦ and the pressure coefficient (∂λ/∂P)T decrease with increasing carbon number of alkanes. The experimental results were correlated with temperature and pressure by a similar expression to the Tait equation. It is also found that both the dense hard-sphere model presented by Menashe et al. and the modified significant structure theory proposed by Prabhuram and Saksena provide good representations of the present experimental results.

Thermal conductivity of gaseous fluorocarbon refrigerants R 12, R 13, R 22, and R 23, under pressure

The thermal conductivity of four gaseous fluorocarbon refrigerants has been measured by a vertical coaxial cylinder apparatus on a relative basis. The fluorocarbon refrigerants used and the ranges of temperature and pressure covered are as follows: R 12 (Dichlorodifluoromethane CCl2F2): 298.15–393.15 K, 0.1–4.28 MPa R 13 (Chlorotrifluoromethane CClF3): 283.15–373.15 K, 0.1–6.96 MPa R 22 (Chlorodifluoromethane CHClF2): 298.15–393.15 K, 0.1–5.76 MPa R 23 (Trifluoromethane CHF3): 283.15–373.15 K, 0.1–6.96 MPaThe apparatus was calibrated using Ar, N2, and CO2 as the standard gases. The uncertainty of the experimental data is estimated to be within 2%, except in the critical region. The behavior of the thermal conductivity for these fluorocarbons is quite similar; thermal conductivity increases with increasing pressure. The temperature coefficient of thermal conductivity at constant pressure, (∂λ/∂T)p, is positive at low pressures and becomes negative at high pressures. Therefore, the thermal conductivity isotherms of each refrigerant intersect each other in a specific range of pressure. A steep enhancement of thermal conductivity is observed near the critical point. The experimental results are statistically analyzed and the thermal conductivities are expressed as functions of temperature and pressure and of temperature and density.