Simultaneously measurements of the PVT and thermal – pressure coefficient of benzene in the critical and supercritical regions (original) (raw)
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Heat capacity and molar volume are analyzed as a function of temperature using the experimental data from the literature for the solid phases I and II of benzene. For this analysis, the experimental data for the heat capacity at constant pressures of 0.1, 0.9 and 1.5 GPa are used whereas for the molar volume, the experimental data at 1 atm are analyzed. The temperature dependences of the thermal expansion and the isothermal compressibility are calculated. On the basis of those thermodynamic quantities, it is found that the Pippard relations are valid at various temperatures (P=1 atm) for the solid phases I and II of benzene.
Pressure dependence of molar volume near the melting point in benzene
Tsinghua Science and Technology, 2007
The pressure dependence of the molar volume was at constant temperatures close to the melting point in benzene. The molar volume of benzene was calculated using experimental data for the thermal expansivity for constant temperatures of 25 , 28.5 , 40 , and 51 at various pressures for both the solid and liquid phases. The predictions are in good agreement with the observed volumes in both the solid and liquid phases of benzene. The predicted values of the molar volume for a constant temperature of 28.5 in the liquid phase of benzene agree well with experimental data in the literature.
International Journal of Thermophysics, 2020
PVT properties and the thermal-pressure coefficient, V = (P∕ T) V , of 2-propanol have been simultaneously measured in the near-and supercritical regions using hightemperature and high-pressure nearly constant-volume piezo-calorimeter. Measurements were made along 9 liquid and 3 vapor isochores between (234.3 and 697.69) kg•m −3 and at temperatures from (317.17 to 522.36) K at pressures up to 6.05 MPa. For each measured isochore (), the values of phase transition temperature (T S) and pressure (P S) at the liquid-gas phase equilibrium curve have been determined using the isochoric P − T break point and thermal-pressure coefficient abruptness techniques. The measured saturated liquid (′ S) and vapor (′′ S) densities near the critical point and thermal-pressure coefficient abruptness disappearance were used to estimate the values of the critical parameters (T C = 508.72 K, P C = 4.840 MPa, and C = 268.82 kg•m −3) of 2-propanol. The expanded uncertainty of the pressure (P), density (), and thermal-pressure coefficient (V) measurements at the 95 % confidence level with a coverage factor of k = 2 are estimated to be 0.05 %, 0.16 %, and 1.5 %, respectively. Scaling-type critical anomaly of the asymptotic behavior of thermal-pressure coefficient in the immediate vicinity of the critical point was experimentally observed. The measured pressures (PVT) and thermal-pressure coefficients (V VT) have been used to calculate of the other key thermodynamic properties such as internal pressure (P int), enthalpy (ΔH vap) and entropy (ΔS vap) of vaporization, saturation (C sat), isobaric (C P), and isochoric (C V) heat capacities.
2012
An equation of state (EOS) is presented for the thermodynamic properties of benzene that is valid from the triple point temperature (278.674 K) to 725 K with pressures up to 500 MPa. The equation is expressed in terms of the Helmholtz energy as a function of temperature and density. This formulation can be used for the calculation of all thermodynamic properties. Comparisons to experimental data are given to establish the accuracy of the EOS. The approximate uncertainties (k = 2) of properties calculated with the new equation are 0.1% below T = 350 K and 0.2% above T = 350 K for vapor pressure and liquid density, 1% for saturated vapor density, 0.1% for density up to T = 350 K and p = 100 MPa, 0.1 – 0.5% in density above T = 350 K, 1% for the isobaric and saturated heat capacities, and 0.5% in speed of sound. Deviations in the critical region are higher for all properties except vapor pressure.
An equation of state (EOS) is presented for the thermodynamic properties of benzene that is valid from the triple point temperature (278.674 K) to 725 K with pressures up to 500 MPa. The equation is expressed in terms of the Helmholtz energy as a function of temperature and density. This formulation can be used for the calculation of all thermodynamic properties. Comparisons to experimental data are given to establish the accuracy of the EOS. The approximate uncertainties (k = 2) of properties calculated with the new equation are 0.1% below T = 350 K and 0.2% above T = 350 K for vapor pressure and liquid density, 1% for saturated vapor density, 0.1% for density up to T = 350 K and p = 100 MPa, 0.1 -0.5% in density above T = 350 K, 1% for the isobaric and saturated heat capacities, and 0.5% in speed of sound. Deviations in the critical region are higher for all properties except vapor pressure.
An equation of state (EOS) is presented for the thermodynamic properties of benzene that is valid from the triple point temperature (278.674 K) to 725 K with pressures up to 500 MPa. The equation is expressed in terms of the Helmholtz energy as a function of temperature and density. This formulation can be used for the calculation of all thermodynamic properties. Comparisons to experimental data are given to establish the accuracy of the EOS. The approximate uncertainties (k = 2) of properties calculated with the new equation are 0.1% below T = 350 K and 0.2% above T = 350 K for vapor pressure and liquid density, 1% for saturated vapor density, 0.1% for density up to T = 350 K and p = 100 MPa, 0.1 -0.5% in density above T = 350 K, 1% for the isobaric and saturated heat capacities, and 0.5% in speed of sound. Deviations in the critical region are higher for all properties except vapor pressure.
The Journal of Chemical Thermodynamics, 2012
The pressures (P) and its temperature derivatives or thermal-pressure coefficient, c V = (oP/oT) V , of DEE have been measured in the near-and supercritical regions as a function of temperature along the various liquid and vapour isochores. Measurements were made in the immediate vicinity of the liquid-gas phase transition and the critical points (single-and two-phase regions) using a high-temperature, high-pressure, nearly constant-volume adiabatic piezo-calorimeter. The constant-volume adiabatic calorimeter previously used for C V measurements was additionally supplied with high accurate strain gauge (calibrated piezoelectric transducer) to measure simultaneously the PvT, C V vT, and thermal-pressure coefficient c V. Measurements were made along 17 liquid and vapour isochores in the range from (212.6 to 534.6) kg Á m À3 and at temperatures from (347 to 575) K and at pressures up to 18 MPa. The quasi-static thermo-(reading of PRT, T-s plot) and barograms (readings of the high accurate strain gauge, P-s plot) techniques were used to accurate measure of the phase transition parameters (P S , q S , T S) and c V at saturation curve. Temperatures at the liquid-gas phase transition curve, T S (q), for each measured density (isochore) and the critical parameters (T C and q C) for DEE were obtained using the quasi-static thermograms technique. The expanded uncertainty of the pressure and its temperature derivative, (oP/oT) V , measurements at the 95% confidence level with a coverage factor of k = 2 is estimated to be 0.05% and (0.12 to 1.5)% (depending on temperature and pressure), respectively. The measured pressures and temperature derivatives, (oP/oT) V , have been used to calculate the internal pressure (or energy-volume coefficient)
The Journal of Chemical Thermodynamics, 2008
The densities of (octane + benzene) were measured at elevated pressures (0.1 to 40) MPa at four temperatures over the range (298.15 to 328.15) K with a high-pressure apparatus. The high-pressure density data were fitted to the Tait equation and the isothermal compressibilities were calculated with a novel computation procedure with the aid of this equation. The low-and high-pressure values of excess molar volume V E m calculated from the density data show that the deviations from ideal behaviour in the system are practically independent of temperature and decreases slightly as the pressure is raised. The V E m data were fitted to the fourth-order Redlich-Kister equation, with the maximum likelihood principle being applied for the determination of the adjustable parameters.
High-pressure effects on the benzene pre-crystallization metastable states
The European Physical Journal E, 2019
We report new results on the liquid to solid phase transition of benzene. We determine experimentally and investigate the properties of a number of parameters of the benzene metastable state under different pressures (from 0.1 up to 2200 atm). It is shown that the supercooling, pressure drop, incubation period, time of abrupt transition from the metastable state to the crystalline state, and time of isothermal freezing all decrease as the external pressure increases, then they all vanish at 2200 atm and 356 K which may mark the end-point of metastability. Quadratic interpolation formulas for these parameters are provided. The densities and molar heat capacities of supercooled benzene under different pressures have been calculated too.
Quasi-isochoric pθT measurements, 2nd virial coefficient and vapor pressure of benzene
Fluid Phase Equilibria, 1992
Quasi-isochoric ppT measurements on benzene vapor were carried out in the low density region using an improved apparatus that was originally proposed by Opel and SchaRenger (1969). The experimental results cover the temperature range between 350 and 600 K and the density range between 13 and 44 mol/m3. The study includes results that were measured with a similar apparatus by Pietsch (1978) which have been reanalyzed. 2nd virial coefficients are derived with an assumed maximum uncertainty of f 1.5 per cent. The results are compared with others in the literature and used to develop an improved correlation function for the temperature dependence of B(T). Vapor pressures mea.sured using the same cell are also presented. These are in good agreement with other experimental data as well as with a recently published correlation.