Thermal Pressure Coefficient Research Articles

Calculation of Thermal Pressure Coefficient of Lithium Fluid by pVT Data

For thermodynamic performance to be optimized, particular attention must be paid to the fluid’s thermal pressure coefficients and thermodynamics properties. A new analytical expression based on the statistical mechanics is derived for thermal pressure coefficients of dense fluids using the intermolecular forces theory to be valid for liquid lithium as well. The results are used to predict the parameters of some binary mixtures at different compositions and temperatures metal-nonmetal lithium fluid which agreement with experimental data. In this paper, we have used newly presented parameters of analytical expressions based on the statistical mechanics and predicted the metal-nonmetal transition for liquid lithium. The repulsion term of the effective pair potential for lithium shows well depth at 1600 K, and the position of well depth maximum is in agreement with X-ray diffraction and small-angle X-ray scattering.

Liquid phase PVTx properties of (water + tert-butanol) binary mixtures at temperatures from 278.15 to 323.15 K and pressures from 0.1 to 100 MPa. II. Molar isothermal compressions, molar isobaric expansions, molar thermal pressure coefficients, and internal pressure

Molar isothermal compressions, molar isobaric expansions, molar coefficients of thermal pressure, and internal pressure were calculated over the whole concentration range of {water (1)+tert-butanol (2)} mixture at pressures from 0.1 to 100MPa and temperatures from 278.15 to 323.15K. It was revealed that the extremes, observed on concentration dependences of molar isothermal compression KT,m and molar isobaric expansion EP,m of the mixture, became more pronounced with pressure growth and temperature lowering. Values of molar thermal pressure coefficients of the mixture sharply rose at compositions with small TBA mole fraction and then decreased practically linearly with the alcohol content increasing. Temperature and pressure dependences of the mixture internal pressure were almost linear, and at low TBA concentrations changed significantly from the dependences of water, tert-butanol and their mixtures at large alcohol content.

Derived thermodynamic properties for the (ethanol + decane) and (carbon dioxide + ethanol + decane) systems at high pressures

Volumetric properties for the binary (ethanol+decane) and ternary (ethanol+decane+carbon dioxide) systems are reported from (313 to 363)K and pressures up to 20MPa. Compressed liquid densities of both systems were measured in a vibrating tube densimeter at different compositions. Binary mixtures {x1 ethanol+(1-x1) decane} were prepared at x1=0.0937, 0.1011, 0.2507, 0.4963, 0.7526, 0.9014. Compositions for the ternary system were prepared by varying the ethanol/decane relation and trying to keep constant the presence of carbon dioxide at about 0.2 mole fraction. These were {x1 ethanol+x2 decane+(1-x1-x2) carbon dioxide} x1=0.0657, 0.1986, 0.4087, 0.6042, 0.7109. Density results were correlated using an empirical model with five parameters. Deviations between experimental and calculated values agree and are within the experimental uncertainty. Isobaric expansivity, isothermal compressibility, thermal pressure coefficient, and internal pressure have been calculated for both binary and ternary systems using the empirical model.

Thermophysical properties of liquid squalane C30H62 within the temperature range of 298.15–413.15 k at atmospheric pressure

The measurements results of the sound speed, density, and isobaric heat capacity of liquid squalane on the saturation line and at atmospheric pressure within the temperature range of 263.15–413.15 K are presented. The data obtained are used to calculate the ratio of the heat capacities, γ; adiabatic, βS, and isothermal, βT, compressibilities; thermal expansion coefficient, αP, thermal pressure coefficient, \(\left( {\frac{{\partial P}} {{\partial T}}} \right)_V \) and also to estimate the energy of the intermolecular interaction on the basis of the discrete-continuum model.

PvT and thermal-pressure coefficient measurements of diethyl ether (DEE) in the critical and supercritical regions

The pressures (P) and its temperature derivatives or thermal-pressure coefficient, γV=(∂P/∂T)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 CV measurements was additionally supplied with high accurate strain gauge (calibrated piezoelectric transducer) to measure simultaneously the PvT, CV vT, and thermal-pressure coefficient γV. Measurements were made along 17 liquid and vapour isochores in the range from (212.6 to 534.6)kg·m−3 and at temperatures from (347 to 575)K and at pressures up to 18MPa. The quasi-static thermo- (reading of PRT, T–τ plot) and barograms (readings of the high accurate strain gauge, P–τ plot) techniques were used to accurate measure of the phase transition parameters (PS,ρS,TS) and γV at saturation curve. Temperatures at the liquid-gas phase transition curve, TS(ρ), for each measured density (isochore) and the critical parameters (TC and ρC) for DEE were obtained using the quasi-static thermograms technique. The expanded uncertainty of the pressure and its temperature derivative, (∂P/∂T)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, (∂P/∂T)V, have been used to calculate the internal pressure (or energy–volume coefficient) as ∂U∂vT=T∂P∂TV-P. The effect of pressure and temperature on the internal pressure near the critical point was studied. The measured values of thermal-pressure coefficient, (∂P/∂T)V, were used to determine accurately the behaviour of second temperature derivative (∂2P/∂T2)V near the critical point and compared with our previous isochoric heat capacity measured results, ∂2P∂T2ρ=-ρ2T∂CV∂ρT. The measured and derived thermodynamic properties of DEE near the critical point were interpreted in terms of theory of critical phenomena.

A laboratory investigation of thermally induced pore pressures in the Callovo-Oxfordian claystone

In the framework of research into radioactive waste disposal, it was decided to investigate the thermally induce pore pressure occurring in the Callovo-Oxfordian claystone (a possible host rock in France). Thermal pore pressures appear in low permeability soils and rocks because the thermal expansion coefficient of water is significantly higher than that of the solid grains.Claystone samples provided to the laboratory are often desaturated, so particular emphasis was put on the saturation of the samples, carried out under in-situ effective stress condition.Thermal pressurization was investigated by performing undrained heating tests while measuring pore pressures changes in a specially adapted thermal isotropic compression cell. Special care was devoted to calibration procedures to account for the effects of the system on pore pressure measurements. The thermal pressurization coefficient measured appeared to change with temperature, mainly because of the changes with temperature of both the water thermal expansion coefficient and the drained compression coefficient of the claystone.

Densities and derived thermodynamic properties of binary (alkanol + boldine) mixtures in the compressed liquid region

In this work, densities of two binary systems of {alkanol (ethanol and 1-propanol)+boldine} are measured at temperatures from (313 to 363)K and pressures up to 20MPa using an Anton Paar vibrating tube densimeter. Each (alkanol+boldine) system was prepared at five diluted compositions with respect to the alkaloid. These are (x2=0.0012, 0.0074, 0.0136, 0.0196, 0.0267) and (x2=0.0018, 0.0046, 0.0077, 0.0112, 0.0142) mixed in ethanol and 1-propanol, respectively. Experimental densities are correlated using an empirical 6-parameter equation with deviations within 0.04%. Extrapolated densities at atmospheric pressure agree with the literature data. Isobaric expansivity, isothermal compressibility, thermal pressure coefficient, and internal pressure have been calculated.

Thermophysical properties of 1-butyl-4-methylpyridinium tetrafluoroborate

Thermophysical properties, {(p,ρ,T) at T=(283.15 to 393.15)K, pressures up to p=100MPa, and viscosity at T=(283.15 to 373.15)K and p=0.101MPa}, of 1-butyl-4-methylpyridinium tetrafluoroborate [b4mpy][BF4] are reported. The measurements were carried out with a recently constructed Anton-Paar DMA HPM vibration-tube densimeter and a fully automated SVM 3000 Anton-Paar rotational Stabinger viscometer. The vibration-tube densimeter was calibrated using double-distilled water, methanol, toluene, and aqueous NaCl solutions.An empirical equation of state for fitting of the (p,ρ,T) data of [b4mpy][BF4] has been developed as a function of pressure and temperature to calculate the thermal properties of the ionic liquid (IL), such as isothermal compressibility, isobaric thermal expansibility, differences in isobaric and isochoric heat capacities, thermal pressure coefficient, and internal pressure. Internal pressure and the temperature coefficient of internal pressure data were used to make conclusions on the molecular characteristics of the IL.

Calculation of Thermal Pressure Coefficient of Dense C<sub>15</sub>H<sub>32</sub>, C<sub>17</sub>H<sub>36</sub>, C<sub>18</sub>H<sub>38</sub> and C<sub>19</sub>H<sub>40</sub> Using <i>pVT</i> Data

The thermal pressure coefficients in liquid n-Pentadecane (C15), n-Heptadecane (C17), n-octadecane (C18) and n-nonadecane (C19) was measured using pVT data. The measurements were carried out at pressures up to 150 MPa in the temperature range from 293 to 383 K. The experimental results have been used to evaluate various thermophysical properties such as thermal pressure coefficients up to 150 MPa with the use of density and temperature data at various pressures. New parameters of the linear isotherm regularity, the so-called LIR equation of state, are used to calculate of thermal pressure coefficients of n-Pentadecane (C15), n-Heptadecane (C17), n-octadecane (C18) and n-nonadecane (C19) dense fluids. In this paper, temperature dependency of linear isotherm regularity parameters in the form of a first order has been developed to second and third order and their temperature derivatives of new parameters are used to calculate thermal pressure coefficients. The resulting model predicts accurately thermal pressure coefficients from the lower density limit at the Boyle density at the from triple temperature up to about double the Boyle temperature. The upper density limit appears to be reached at 1.4 times the Boyle density. These problems have led us to try to establish a function for the accurate calculation of the thermal pressure coefficients based on the linear isotherm regularity theory for different fluids.

Thermal properties of 1-butyl-3-methylimidazolium dicyanamide at high pressures and temperatures

Thermophysical properties of 1-butyl-3-methylimidazolium dicyanamide (BMIM)(DCA) {(p, , T) data at T = (283.15 to 393.15) K, pressures up to p =100 MPa, and viscosity at T = (283.15 to 373.15) K and p = 0.101 MPa} are reported with an estimated experimental relative combined standard uncertainty of ∆/ = ±(0.01 to 0.08) % in density and ∆/ = ±0.35 % in dynamic viscosity. The measurements were carried out with a recently constructed Anton-Paar DMA HPM vibration-tube densimeter and a fully automated SVM 3000 Anton-Paar rotational Stabinger viscometer. The vibration-tube densimeter was calibrated using double- distilled water, methanol, toluene and aqueous NaCl solutions. An empiric equation of state for fitting of the (p, , T) data of (BMIM)(DCA) has been developed as a function of pressure and temperature. This equation was used for the calculation of thermomechanical properties of the IL, such as isothermal compressibility, isobaric thermal expansibility, differences in isobaric and isochoric heat capacities, thermal pressure coefficient and internal pressure. Viscosity measurements were fitted to the polynomial equation.

Thermodynamic properties of electrolyte solutions. Compressibility studies in aqueous solutions of urayl nitrate

Sound velocities in aqueous solutions of uranyl nitrate were measured at 5 K intervals from T = (283.15 to 323.15) K, within the (0.1 to 2.8) mol · kg −1 concentration range. The sound velocities determined then served to evaluate the isentropic and isothermal compressibilities, the apparent molar compressibilities, the isochoric thermal pressure coefficients, changes of the cubic expansion coefficients with pressure and the heat capacities with volume and these parameters are qualitatively correlated with the changes in the structure of water when uranyl nitrate is dissolved in it.

Volumetric properties of ethyl acetate + carbon dioxide binary fluid mixtures at high pressures

Volumetric properties of carbon dioxide, ethyl acetate and their binary mixtures containing 27.7, 42.6, 52.9 and 67.3% by mass CO 2 have been determined over a temperature range from 295 to 380 K for pure components, and from 295 to 340 K for mixtures at pressures up to 32 MPa. A new measurement methodology was employed in which a pressure-generator is used to alter the position of a movable piston while continually monitoring its position, thus the internal volume, with a computer-interfaced linear variable differential transformer (LVDT). The real-time recording of the internal volume permits generation of continuous density–pressure data which are correlated by smooth functions and used to determine the isothermal compressibility, the isobaric expansivity, the thermal pressure coefficient, and the excess volumes. The densities were observed to vary in the range from 0.60 to 0.98 g/cm 3 for carbon dioxide; from 0.80 to 0.92 g/cm 3 for ethyl acetate, and from 0.75 to 0.98 g/cm 3 for the mixtures. Depending upon the temperature and pressure, the compressibility values were in the range 0.002–0.04 MPa −1 for CO 2, and 1.0–2.3 × 10 −3 MPa −1 for ethyl acetate. The expansivity values were in the range 3.7–11 × 10 −3 K −1 for CO 2 and 1.0–1.4 × 10 −3 K −1 for ethyl acetate. The thermal pressure coefficients were in the range 0.3–1.9 MPa/K for CO 2 and 0.55–1.2 MPa/K for ethyl acetate. In the mixtures, the isothermal compressibility and isobaric expansivity were found to increase while the thermal pressure coefficients decreased in going from ethyl acetate to carbon dioxide. The mixtures displayed mostly negative excess volumes. The magnitude of the negative excess volume was observed to decrease with pressure at a given temperature, but increase with increasing temperature at a given pressure. The largest (negative) excess volume, approaching −16 cm 3/mol, was observed at the higher experimental temperature (340 K) and the lower pressure (16 MPa).

Free Volume from Pressure and Temperature Dependent Viscosity and from PVT Measurements for Homo- and Copolymers

Abstract Pressure and temperature dependency of shear and elongation viscosity and the thermal expansivity and the compressibility determined from PVT data were investigated for propylene homo- and propylene-1-pentene, -1-hexene, 1-heptene and -nonene copolymers and ethylene homopolymer and ethylene-1-butene, 1-pentene and 1-hexene copolymers. The short branching degree dependence of thermal sensitivity and pressure coefficient and the thermal expansivity and the compressibility has been determined. The fractional free volumes were calculated from the viscosity and PVT curves and the thermal expansion coefficient and compressibility factor of fractional free volume were determined. The temperature, pressure and stress dependence of fractional free volume was investigated. The fractional free volume calculated from viscosity data were compared from values comes from PVT measurement. A conversion equation was suggested.

Thermodynamic properties of 1-butyl-3-methylpyridinium tetrafluoroborate

Pressure, density, temperature ( p, ρ, T) data of 1-butyl-3-methylpyridinium tetrafluoroborate [C4mpyr][BF 4] at T = (283.15 to 393.15) K and pressures up to p = 100 MPa are reported with an estimated experimental relative combined standard uncertainty of Δ ρ/ ρ = ±(0.01 to 0.08)% in density. The measurements were carried out with a newly constructed Anton-Paar DMA HPM vibration-tube densimeter. The system was calibrated using double-distilled water, methanol, toluene and aqueous NaCl solutions. An empirical equation of state for fitting of the ( p, ρ, T) data of [C4mpyr][BF 4] has been developed as a function of pressure and temperature to calculate the thermal properties of the ionic liquid (IL), such as isothermal compressibility, isobaric thermal expansibility, differences in isobaric and isochoric heat capacities, thermal pressure coefficient and internal pressure. Internal pressure and the temperature coefficient of internal pressure data were used to make conclusions on the molecular characteristics of the IL.

Experimental Study of the Thermodynamic Properties of Diethyl Ether (DEE) at Saturation

The isochoric heat capacities \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\), saturation densities (\({\rho _{\rm S}^{\prime}}\) and \(({\rho_{\rm S}^{\prime\prime})}\)), vapor pressures (P S), thermal-pressure coefficients \({\gamma_V=\left({\partial P/\partial T}\right)_V}\), and first temperature derivatives of the vapor pressure γ S = (dP S/dT) of diethyl ether (DEE) on the liquid–gas coexistence curve near the critical point have been measured with a high-temperature and high-pressure nearly constant-volume adiabatic piezo-calorimeter. The measurements of \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\) were made in the liquid and vapor one- and two-phase regions along the coexistence curve. The calorimeter was additionally supplied with a calibrated extensometer to accurately and simultaneously measure the PVT, C V VT, and thermal-pressure coefficient, γ V , along the saturation curve. The measurements were carried out in the temperature range from 416 K to 466.845 K (the critical temperature) for 17 liquid and vapor densities from 212.6 kg · m−3 to 534.6 kg · m−3. The quasi-static thermo- (reading of PRT, T − τ plot) and baro-gram (readings of the tensotransducer, P − τ plot) techniques were used to accurately measure the phase-transition parameters (P S ,ρ S ,T S) and γ V . The total experimental uncertainty of density (ρ S), pressure (P S), temperature (T S), isochoric heat capacities \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\), and thermal-pressure coefficient, γ V , were estimated to be 0.02 % to 0.05 %, 0.05 %, 15 mK, 2 % to 3 %, and 0.12 % to 1.5 %, respectively. The measured values of saturated caloric \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\) and saturated thermal (P S, ρ S, T S) properties were used to calculate other derived thermodynamic properties C P , C S, W, K T , P int, ΔH vap, and \({\left({\partial V/\partial T}\right)_P^{\prime}}\) of DEE near the critical point. The second temperature derivatives of the vapor pressure, (d2 P S/dT 2), and chemical potential, (d2 μ/dT 2), were also calculated directly from the measured one- and two-phase liquid and vapor isochoric heat capacities \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\) near the critical point. The derived values of (d2 P S/dT 2) from calorimetric measurements were compared with values calculated from vapor–pressure equations. The measured and derived thermodynamic properties of DEE near the critical point were interpreted in terms of the “complete scaling” theory of critical phenomena. In particular, the effect of a Yang–Yang anomaly of strength R μ on the coexistence-curve diameter behavior near the critical point was studied. Extended scaling-type equations for the measured properties P S (T), ρ S (T), and \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\) as a function of temperature were developed.

Solvation of hydrophobes in water and simple liquids

The solvation of nonpolar molecules in water and that in simple liquids are compared and contrasted. First, solvation thermodynamics is reviewed in a way that focuses on how the enthalpy and entropy of solvation depend on the choice of microscopic volume change v in the solvation process--including special choices v being zero (fixed-volume condition) and v being the partial molecular volume of a solute molecule (fixed-pressure condition)--and how the solvation quantities are related with temperature derivatives of the solvation free energy. Second, the solvation free energy and the solvation enthalpy of a Lennard-Jones (LJ) atom in model water are calculated in the parameter space representing the solute size and the strength of the solute-solvent interaction, and the results are compared with those for an LJ atom in the LJ solvent. The solvation diagrams showing domains of different types of solvation in the parameter space are obtained both for the constant-volume condition and for the constant-pressure condition. Similarities between water and the simple liquid are found when the constant-volume solvation is considered while a significant difference manifests itself in the fixed-pressure solvation. The domain of solvation of hydrophobic character in the parameter space is large in the constant-volume solvation both for water and for the simple liquid. When switched to the constant-pressure condition accompanying a microscopic volume change, the hydrophobic domain remains large in water but it becomes significantly small in the simple liquid. The contrasting results are due to the smallness of the thermal pressure coefficient of water at low temperatures.

Thermodynamic Properties of 1-Ethyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide

(p,ρ,T) data of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [EMIM][NTf2] at T = (283.15 to 373.15) K and pressures up to p = 100 MPa are reported with an estimated experimental relative combined standard uncertainty of Δρ/ρ = ± (0.01 to 0.08) % in density. The measurements were carried out with a newly constructed Anton Paar DMA HPM vibration-tube densimeter. The system was calibrated using double-distilled water, methanol, toluene and aqueous NaCl solutions. An empiric equation of state for fitting of the (p,ρ,T) data of [EMIM][NTf2] has been developed as a function of pressure and temperature. This equation was used for the calculation of the thermal properties of IL, such as isothermal compressibility, isobaric thermal expansibility, differences in isobaric and isochoric heat capacities, thermal pressure coefficient, and internal pressure.

Pressure–volume–temperature behavior of two polycyanurate networks

AbstractThe pressure–volume–temperature (PVT) behavior was studied for two polycyanurate networks having different crosslink densities using a pressurizable dilatometer. The samples were studied at temperatures ranging from 60 to 180 °C and at pressures up to 170 MPa to yield PVT data in both rubbery and glassy states. The Tait equation is found to well describe the isobaric temperature scan and isothermal pressure scan data. The thermal expansion coefficients, instantaneous bulk moduli, and thermal pressure coefficients are extracted from the data and their dependence on crosslink density is examined. The time‐dependent viscoelastic bulk modulus (K(t)) is also calculated in the vicinity of the α‐relaxation from previously published pressure relaxation experimental data, and the strength and shape of the dispersion are found to be independent of crosslink density. The limiting bulk moduli depend strongly on temperature with those of the more loosely crosslinked sample being lower at a given temperature and pressure, although at Tg(P), the limiting moduli of the more loosely crosslinked sample are slightly higher than those of the more highly crosslinked sample. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010

Densities and Volumetric Properties of Ethylene Glycol + Dimethylsulfoxide Mixtures at Temperatures of (278.15 to 323.15) K and Pressures of (0.1 to 100) MPa

Densities, ρ, and compressibility coefficients, k = (vo − v)/vo, of ethylene glycol (1) + dimethylsulfoxide (2) mixtures were measured over the whole concentration range at pressures of (0.1 to 100) MPa and temperatures of (278.15 to 323.15) K. Excess molar volumes, isothermal compressibility, and thermal isobaric expansivity coefficients as well as thermal pressure coefficients were calculated. It was revealed that concentration dependences of specific volumes, v, at some state parameters passed a minimum. The shift of minimum position to molar fraction x2 = 0.5 was observed with increasing pressure and decreasing temperature. The negative excess molar volumes, VmE, indicated a compression of EG (1) + DMSO (2) systems when mixing. Composition dependences of isothermal compressibility, κT, and thermal isobaric expansivity coefficients, α, as well as thermal pressure coefficients, β, were near-linear. Both increasing and decreasing of κT and β values were observed with x2 increase depending on temperature ...

Empirical Regularity of the Thermal Pressure Coefficient for Dense Fluids

In this paper, an empirical regularity has been proposed for dense fluids, namely, that the thermal pressure coefficient is a near-parabola function of pressure. The regularity has been tested with experimental data for both associating and nonassociating compounds. The applicable ranges have also been investigated widely. It is found that the regularity holds well from the freezing temperature to critical temperature, and no obvious limits were found for pressure and compound type. Moreover, parameters of the thermal pressure coefficient expression were regressed from experimental data for n-alkanols, and the statistical results show it is an accurate correlation equation. Further, on the basis of the Lennard-Jones (12-6) potential function, the theoretical analysis was given to confirm the existence and uniqueness of the peak point for Lennard-Jones fluids.