Equation of state for benzene for temperatures from the melting line up to 725 K with pressures up to 500 MPa | NIST (original) (raw)
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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.
Journal of Molecular Liquids, 2019
The values of pressure (P), the temperature derivative, γ V = (∂P/∂T) V , and the density (ρ) of benzene have been simultaneously measured in the near-and supercritical regions using high-temperature and high-pressure piezo-calorimeter. Measurements were made along 10 liquid and vapor isochores between (265.5 and 653.9) kg•m −3 and at temperatures from (346.03 to 615.92) K and at pressures up to 9.171 MPa. For each isochore most measurements were made in the immediate vicinity of the liquid-gas phase transition temperature (singleand two-phase regions) where the break of the P-T isochores and the jumps of the thermal-pressure coefficient γ V are observing. Temperatures and pressures (T S , P S) at the liquid-gas phase transition curve for each constant density (isochore, ρ) and the critical parameters (T C ,P C ,ρ C) for benzene were measured using the isochoric P − T break point and thermal-pressure coefficient jump techniques. The expanded uncertainty of the pressure (P), density (ρ), and thermal-pressure coefficient (γ V) measurements at the 95% confidence level with a coverage factor of k = 2 is estimated to be, 0.16%, 0.05% and (0.12 to 1.5) % (depending on temperature and pressure), respectively. The measured pressures (PVT) and thermal-pressure coefficients (γ V VT) have been used to calculate of the internal pressure (or energy-volume coefficient) as ð ∂U ∂V Þ T ¼ Tð ∂P ∂T Þ V −P. We have also measured the temperature derivatives of the internal energy ð ∂U ∂T Þ V ¼ C V (isochoric heat capacity) using the same piezocalorimetric cell. The effect of pressure and temperature on the internal pressure was studied. Isochoric P-T curve break point and isochoric thermal-pressure coefficient jump techniques were used to accurately determine of the phase transition and critical points parameters. The measured values of the thermal-pressure coefficient were interpreted in term of scaling theory of critical phenomena. The measured values of pressure (P), temperature derivative, (∂P/∂T) V , temperature and density at the saturation curve together with our previous isochoric heat capacity measurements were used to calculate other thermodynamic properties of benzene at saturation curve.
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.
A Fundamental Equation of State for the Calculation of Thermodynamic Properties of n-Octane
Journal of Physical and Chemical Reference Data
An empirical equation of state in terms of the Helmholtz energy is presented for n-octane. It is valid from the triple-point temperature 216.37 K to 650 K with a maximum pressure of 1000 MPa and allows for the calculation of all thermodynamic properties in the vapor and liquid phase, in the supercritical region, and in equilibrium states. In the homogeneous liquid phase, the uncertainty in density is 0.03% at atmospheric pressure. For pressures up to 200 MPa and temperatures between 270 and 440 K, density is described with an uncertainty of 0.1%. Outside this region, the uncertainty in the liquid phase increases to 0.5%. Densities in the vapor phase are estimated to be accurate within 0.5%. The uncertainty in vapor pressure depends on the temperature range and varies from 0.02% to 0.4%. Speed of sound in the liquid phase at temperatures below 500 K is described with an uncertainty of 0.1% or less. The isobaric heat capacity in the liquid phase can be calculated with an uncertainty o...
2012
Dow This paper contains new, representative reference equations for the thermal conductivity of benzene. The equations are based in part upon a body of experimental data that have been critically assessed for internal consistency and for agreement with theory whenever possible. In the case of the dilute-gas thermal conductivity, a theoretically based correlation was adopted in order to extend the temperature range of the experimental data. Moreover, in the critical region, the experimentally observed enhancement of the thermal conductivity is well represented by theoretically based equations containing just one adjustable parameter. The correlations are applicable for the temperature range from the triple point to 725 K and pressures up to 500 MPa. The overall uncertainty (considered to be estimates of a combined expanded uncertainty with a coverage factor of two) of the proposed correlation is estimated, for pressures less than 350 MPa and temperatures less than 725 K, to be less t...
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.
Reference Correlation of the Viscosity of Benzene from the Triple Point to 675 K and up to 300 MPa
Journal of Physical and Chemical Reference Data, 2014
This paper contains new, representative reference equations for the viscosity of benzene. The equations are based in part upon a body of experimental data that has been critically assessed for internal consistency and for agreement with theory whenever possible. The correlation is valid from the triple point (278.647 K) to 675 K, and at pressures up to 300 MPa, with the exception of temperatures lower than 350 K where the pressure is restricted to 200 MPa. For the liquid phase, at temperatures from 288 to 373 K at pressures up to 80 MPa, we estimate the uncertainty (at a 95% confidence level) to be 1.8%, increasing to 3.4% at 200 MPa, and 5% at pressures up to the correlation maximum. For the liquid at temperatures from 373 to 523 K, the uncertainty is 2.7% at pressures from saturation to 50 MPa, rising to 3.6% at 300 MPa. For temperatures above 523 K, we estimate the uncertainty in the liquid phase to be 5%. The uncertainty for the low-density fluid phase at temperatures from 305 to 640 K and pressures to 0.3 MPa is estimated to be 0.2%.