The Experts below are selected from a list of 219 Experts worldwide ranked by ideXlab platform
Christopher J. Wormald - One of the best experts on this subject based on the ideXlab platform.
-
The isothermal Joule–Thomson Coefficient of steam measured fromT = 313.00 K toT = 413.19 K
The Journal of Chemical Thermodynamics, 2000Co-Authors: M.l. Mcglashan, Christopher J. WormaldAbstract:A flow calorimeter with an adjustable throttle has been used to measure the isothermal Joule–Thomson Coefficient of water vapour at temperatures from T = 313.00 K to 413.19 K. At each temperature measurements made over a range of pressures were extrapolated to zero pressure to obtain the quantityφo = (B − TdB / dT), where B is the second virial Coefficient. At temperatures above 330 K the measurements are in good agreement with the work of Collins and Keyes (1937), and if their value at T = 312.09 K is corrected by 3.3 per cent, the amount by which their measurement of the heat capacity of steam at this temperature is in error, the agreement is within the combined experimental error over the whole temperature range. Values of the zero pressure isothermal Joule–Thomson Coefficientφo derived from the measurements are compared with an equation for B(T) proposed by Gallagher which is consistent with the 1984 NBS/NRC steam tables, an equation for B(T) proposed in 1988 by Hill and MacMillan, and with values of B(T) derived from the 1995 IAPWS equation of state for steam of Pruss and Wagner. The new measurements are found to be in agreement with the equation of Hill and MacMillan to within the experimental error.
-
Second virial Coefficients of chloromethane and chloroethane from measurements of the excess enthalpy of (0.5N2+ 0.5CH3Cl)(g), and (0.5N2+ C2H5Cl)(g). The excess enthalpy of (0.5CH3Cl + 0.5C2H5Cl)(g)
The Journal of Chemical Thermodynamics, 1998Co-Authors: M Massucci, Christopher J. WormaldAbstract:Abstract A gas-mixing flow calorimeter has been used to measure the excess molar enthalpy H m E of (nitrogen+chloromethane)(g), (nitrogen+chloroethane)(g), and (chloromethane+chloroethane)(g) at standard atmospheric pressure over the temperature range 250 K to 390 K. The measurements are analysed using the corresponding states correlation of Tsonopoulos with the acentric factor ω as a disposable parameter. From the value of ω that fitted the H m E measurements, values of the second virial Coefficient B and the isothermal Joule–Thomson Coefficient φ= B − T (d B /d T ) were calculated. The values of B for chloromethane are in good agreement with other work, but at low temperatures those for chloroethane are less negative than previous measurements. The excess enthalpy of (chloromethane+chloroethane) is fitted using the mean value of ω for the pure components.
-
The excess molar enthalpy of (nitrogen + dimethyl ketone)(g) from temperatures of 333.2 K to 423.2 K
The Journal of Chemical Thermodynamics, 1997Co-Authors: J. A. Doyle, N. M. Lancaster, D.j. Hutchings, Christopher J. WormaldAbstract:Abstract A differential flow mixing calorimeter has been used to measure the excess molar enthalpy H m E of (nitrogen+dimethyl ketone)(g) at standard atmospheric pressure over the temperature range 333.2 K to 423.2 K. The measurements are analysed using the corresponding states correlation of Tsonopoulos using his parameter a as a disposable parameter. The measurements are found to be consistent with measurements of the second virial Coefficient B , the isothermal Joule–Thomson Coefficient φ= B − T (d B /d T ) and the pressure derivative χ=− T 2 (d 2 B /d T 2 ) of the heat capacity of dimethyl ketone. As the H m E measurements are of good accuracy (nitrogen+dimethyl ketone)(g) is recommended as a test system for checking the correct operation of gas phase mixing calorimeters.
G. Ernst - One of the best experts on this subject based on the ideXlab platform.
-
Flow-calorimetric results for the massic heat capacitycpand the Joule–Thomson Coefficient of CH4, of (0.85CH4 + 0.15C2H6), and of a mixture similar to natural gas
The Journal of Chemical Thermodynamics, 2001Co-Authors: G. Ernst, B. Keil, H. Wirbser, M. JaeschkeAbstract:Abstract As a part of an international project, initiated by the Ruhrgas AG, the massic heat capacity c p and the Joule–Thomson Coefficient μ JT were measured with flow calorimeters. Great effort was made in the designing and construction of the equipment and in the experiments to reach a high accuracy of the results. The pressure range of the measurements was 0.5 MPa to 30 MPa and the temperature range 250 K to 350 K. The results are contained in the present paper. They yield the enthalpy as a function of temperature and pressure. Within the project they contribute to the experimental basis for a formulation of an equation of state.
-
Massic heat capacities and Joule–Thomson Coefficients of CH2FCF3(R134a) at pressures up to 30 MPa and temperatures between about 253 K and 523 K
The Journal of Chemical Thermodynamics, 1997Co-Authors: G. Ernst, J. Gürtner, H. WirbserAbstract:Abstract The massic heat capacity c p =(∂ h /∂ T ) p of 1,2,2,2-tetrafluoroethane (refrigerant R134a) was measured at 18 temperatures from 253 K to 523 K at pressures between 40 kPa and 30 MPa. The Joule–Thomson Coefficient μ JT =(∂ T /∂ p ) h of this substance was measured at six temperatures from 333 K to 423 K at pressures up to 20 MPa. The R134a has no ozone depletion potential. Its global warming potential is about one-tenth of that of the refrigerant R115 (C 2 F 5 Cl) for which it can be a substitute as a working fluid in energy technologies.
-
Flow-calorimetric specific heat capacities and Joule-Thomson Coefficients of CF3CHFCF3 (R227) - a new working fluid in energy technics - at pressures up to 15 MPa and temperatures between 253 K and 423 K
The Journal of Chemical Thermodynamics, 1992Co-Authors: H. Wirbser, G. Bräuning, J. Gürtner, G. ErnstAbstract:The specific heat capacity of CF 3 CHFCF 3 was measured at pressures up to 15 MPa with two flow calorimeters of high accuracy. The Joule-Thomson-Coefficient was measured at pressures between 0.6 MPa and 15 MPa with a new flow calorimeter. The temperature range of the experiments was 253 K to 423 K. The critical region ( T c = 375.1 K; p c = 2.95 MPa) and the regions of the maxima of the isotherms and isobars were studied with high effort. The comprehensive results are a basis for the determination of the enthalpy as a function of temperature and pressure.
H. Wirbser - One of the best experts on this subject based on the ideXlab platform.
-
Flow-calorimetric results for the massic heat capacitycpand the Joule–Thomson Coefficient of CH4, of (0.85CH4 + 0.15C2H6), and of a mixture similar to natural gas
The Journal of Chemical Thermodynamics, 2001Co-Authors: G. Ernst, B. Keil, H. Wirbser, M. JaeschkeAbstract:Abstract As a part of an international project, initiated by the Ruhrgas AG, the massic heat capacity c p and the Joule–Thomson Coefficient μ JT were measured with flow calorimeters. Great effort was made in the designing and construction of the equipment and in the experiments to reach a high accuracy of the results. The pressure range of the measurements was 0.5 MPa to 30 MPa and the temperature range 250 K to 350 K. The results are contained in the present paper. They yield the enthalpy as a function of temperature and pressure. Within the project they contribute to the experimental basis for a formulation of an equation of state.
-
Massic heat capacities and Joule–Thomson Coefficients of CH2FCF3(R134a) at pressures up to 30 MPa and temperatures between about 253 K and 523 K
The Journal of Chemical Thermodynamics, 1997Co-Authors: G. Ernst, J. Gürtner, H. WirbserAbstract:Abstract The massic heat capacity c p =(∂ h /∂ T ) p of 1,2,2,2-tetrafluoroethane (refrigerant R134a) was measured at 18 temperatures from 253 K to 523 K at pressures between 40 kPa and 30 MPa. The Joule–Thomson Coefficient μ JT =(∂ T /∂ p ) h of this substance was measured at six temperatures from 333 K to 423 K at pressures up to 20 MPa. The R134a has no ozone depletion potential. Its global warming potential is about one-tenth of that of the refrigerant R115 (C 2 F 5 Cl) for which it can be a substitute as a working fluid in energy technologies.
-
Flow-calorimetric specific heat capacities and Joule-Thomson Coefficients of CF3CHFCF3 (R227) - a new working fluid in energy technics - at pressures up to 15 MPa and temperatures between 253 K and 423 K
The Journal of Chemical Thermodynamics, 1992Co-Authors: H. Wirbser, G. Bräuning, J. Gürtner, G. ErnstAbstract:The specific heat capacity of CF 3 CHFCF 3 was measured at pressures up to 15 MPa with two flow calorimeters of high accuracy. The Joule-Thomson-Coefficient was measured at pressures between 0.6 MPa and 15 MPa with a new flow calorimeter. The temperature range of the experiments was 253 K to 423 K. The critical region ( T c = 375.1 K; p c = 2.95 MPa) and the regions of the maxima of the isotherms and isobars were studied with high effort. The comprehensive results are a basis for the determination of the enthalpy as a function of temperature and pressure.
D. K. Belashchenko - One of the best experts on this subject based on the ideXlab platform.
-
Molecular dynamics simulation of the thermodynamic properties of mercury at pressures below 2.5 GPa and temperatures below 10000 K
Russian Journal of Physical Chemistry A, 2017Co-Authors: D. K. BelashchenkoAbstract:Models of mercury were constructed by molecular dynamics using the interparticle potential of the embedded atom model (EAM) at temperatures below 10 000 K and pressures below 2.5 GPa. The thermodynamic properties of the models were presented on the isobars of 0.5, 1.0, 1.5, 2.0, and 2.5 GPa. The compressibility factors Z = pV /( RT ) were calculated; the coordinates of the inversion points of the Joule–Thomson Coefficient below 5600 K were found from the positions of minima on the Z ( p , T ) isobars. At densities above 8–9 g/cm^3, the results of simulation agreed well with experiment; at lower densities there were discrepancies associated with a loss of metal properties by real mercury. The behavior of the models was analyzed in the region of the van der Waals loop. The calculated critical temperature of mercury was found to be significantly overestimated relative to the experiment. Modeling the “meta-mercury” with the EAM potential with excluded embedded potential contribution gave better agreement with the equation of state of mercury at lower densities. The states with Z = 1 can be observed below 1.0 GPa. The calculated temperature of the inversion of the Joule–Thomson Coefficient increased monotonically to 5600 K as the pressure increased to 2.5 GPa.
-
Molecular dynamics simulation of the structure and thermodynamic properties of liquid rubidium at pressures of up to 10 GPa and temperatures of up to 3500 K
Russian Journal of Physical Chemistry A, 2016Co-Authors: D. K. BelashchenkoAbstract:The models of rubidium at temperatures of up to 3500 K, degrees of compression of up to Y = V / V _0 = 0.3, and pressures of up to 32 GPa were constructed by molecular dynamics (MD) using the interparticle potential ЕАМ. The thermodynamic properties of the MD models agree satisfactorily with experiment in the range of parameters under study at rubidium densities higher than 0.86 g/cm^3. The behavior of the models in the range of the van der Waals loop was analyzed; the calculated critical temperature of rubidium T _c is ∼2250 ± 25 K, density ∼0.41 g/cm^3, pressure ∼0.019 GPa, and compressibility factor Z = pV / RT ≈ 0.137. The states with the unity factor Z = 1 were observed at pressures of up to 0.30 GPa (at ∼3000 K); the temperature dependence of the density of the models with Z = 1 is nearly linear, and the Boyle temperature is T _B ≈ 10160 K. The ratio T _c/ T _B = 0.221 is close to this value for cesium (0.23) and mercury (0.276). In the temperature and pressure ranges under study, the inversion of the Joule–Thomson Coefficient did not take place, but should be observed at pressures of ⩽0.3 GPa and elevated temperatures. It was found that the diffusion Coefficient D ( T ) dependences do not straighten in the usually used coordinates within wide temperature ranges. It was concluded that the structure of the liquid smoothly changes when the rubidium models are compressed and this reveals in the change of the degree of asymmetry of the first peak of the radial distribution function.
-
Structure and thermodynamic properties of liquid cesium at pressures below 10 GPa and temperatures below 4000 K according to the molecular dynamics data
Russian Journal of Physical Chemistry A, 2015Co-Authors: D. K. BelashchenkoAbstract:The models of cesium at temperatures of up to 4000 K, compressions of up to Y = V / V _0 = 0.3, and pressures of up to 24 GPa were constructed by the molecular dynamics (MD) method using the ЕАМ interparticle potential. The thermodynamic properties of the models are presented in the tables. The compressibility factors were calculated: Z = pV / RT . The thermodynamic properties of the MD models were in satisfactory agreement with experiment in the range of parameters under study at a cesium density of higher than 1.2 g/cm^3. The behavior of the models in the region of the van der Waals loop was analyzed. The calculated critical temperature of cesium T _c was shown to be ~1950 ± 25 K, approximating the real temperature, the density was ~0.53 g/cm^3, the pressure ~0.015 GPa, and the compressibility factor Z = pV / RT ≈ 0.23. The states with a unity factor Z = 1 were observed at pressures below 0.20 GPa (at 2800 K); the temperature dependence of the density of the models with Z = 1 was almost linear, and the Boyle temperature T _B was 7160 K; the ratio T _c/ T _B = 0.269 was very close to that for mercury (0.276). In the pressure and temperature ranges under study, the inversion of the Joule–Thomson Coefficient was not observed, but took place at densities below 1.2 g/cm^3. The structure of the liquid changed when the degree of compression of the cesium models changed from 0.54 to 0.52. This was reflected by a change in the degree of asymmetry of the first peak of the radial distribution function. An analysis of the structural data of the models of liquid sodium, potassium, and rubidium showed that the structure of these metals also experienced similar changes near the degree of compression 0.5; these changes in alkali metals are not related to the 6 s → 5 d electron transition.
W Wagner - One of the best experts on this subject based on the ideXlab platform.
-
a new equation of state for carbon dioxide covering the fluid region from the triple point temperature to 1100 k at pressures up to 800 mpa
Journal of Physical and Chemical Reference Data, 1996Co-Authors: Roland Span, W WagnerAbstract:This work reviews the available data on thermodynamic properties of carbon dioxide and presents a new equation of state in the form of a fundamental equation explicit in the Helmholtz free energy. The function for the residual part of the Helmholtz free energy was fitted to selected data of the following properties: (a) thermal properties of the single‐phase region (pρT) and (b) of the liquid‐vapor saturation curve (p s, ρ′, ρ″) including the Maxwell criterion, (c) speed of soundw and (d) specific isobaric heat capacityc p of the single phase region and of the saturation curve, (e) specific isochoric heat capacityc v , (f) specific enthalpyh, (g) specific internal energyu, and (h) Joule–Thomson Coefficient μ. By applying modern strategies for the optimization of the mathematical form of the equation of state and for the simultaneous nonlinear fit to the data of all these properties, the resulting formulation is able to represent even the most accurate data to within their experimental uncertainty. In the technically most important region up to pressures of 30 MPa and up to temperatures of 523 K, the estimated uncertainty of the equation ranges from ±0.03% to ±0.05% in the density, ±0.03% to ±1% in the speed of sound, and ±0.15% to ±1.5% in the isobaric heat capacity. Special interest has been focused on the description of the critical region and the extrapolation behavior of the formulation. Without a complex coupling to a scaled equation of state, the new formulation yields a reasonable description even of the caloric properties in the immediate vicinity of the critical point. At least for the basic properties such as pressure, fugacity, and enthalpy, the equation can be extrapolated up to the limits of the chemical stability of carbon dioxide. Independent equations for the vapor pressure and for the pressure on the sublimation and melting curve, for the saturated liquid and vapor densities, and for the isobaric ideal gas heat capacity are also included. Property tables calculated from the equation of state are given in the appendix.
