Experimental HE Data Research Articles

Excess molar enthalpies in the binary system of carbon dioxide + ethyl lactate at 298.15 and 303.15 K and 5.0–7.0 MPa

This paper presents an experimental determination of the excess molar enthalpies (HE) for the binary system of carbon dioxide (CO2) + ethyl lactate at temperatures of 298.15 and 303.15 K and pressures in the range of 5.0–7.0 MPa. A maximum exothermic value of approximately 7.4 kJ mol−1 was found, similar to the exotherms observed in our previous work for other binary systems such as CO2 + ester or ether. We discussed this exothermic behavior based on the change-of-state contribution, strong CO2-ester interactions, and unusual intra- and intermolecular hydrogen bonding of ethyl lactate. The experimental HE data correlated well with a composition-dependent equation and the Peng–Robinson equation of state with the van der Waals one-fluid mixing rule.

Excess enthalpy, density, speed of sound and refractive index of binary mixtures {2-(2-ethoxyethoxy)ethanol + 1-hexene, or cyclohexane, or methylcyclohexane at (298.15 and 313.15) K: Application of the PPR-78 cubic equation of state, NRTL and UNIQUAC models

Excess enthalpy, HE, density, ρ, speed of sound, u, and refractive index, nD, measured data (312 points) are presented for {2-(2-ethoxyethoxy)ethanol (carbitol) with 1-hexene, or cyclohexane, or methylcyclohexane} at 0.1 MPa and (298.15 and 313.15) K throughout the full range of composition. Consequently, derivative properties were determined from the reported experimental data: VE, excess volume, Ks, isentropic compressibility, ΔKs, deviation in isentropic compressibility, ΔnD, deviation in refractive index. The modified Redlich-Kister is employed for the experimental data correlation of HE, while the Predictive Peng-Robinson 1978 (PPR78) EoS is used to model the measured data of HE. As a comparison with PPR78 EoS, the NRTL and UNIQUAC models are applied to have a prediction on the experimental HE data. Also, the Redlich-Kister equation is employed to fit the excess volume, deviation in isentropic compressibility and deviation in refractive index. In the present work, we have discussed intermolecular interactions for the studied binary mixtures.

Excess molar enthalpies of the binary system carbon dioxide + butyl levulinate at 298.15 and 303.15 K and 5.0–7.0 MPa

The excess molar enthalpies (HE) of the binary system carbon dioxide (CO2) + butyl levulinate (a solvent obtainable from biomass) were determined near the critical point of CO2, using a flow-type isothermal microcalorimeter. Values are reported for temperatures of 298.15 and 303.15 K and pressures in the range of 5.0–7.0 MPa. A maximum exothermic value of approximately 8.1 kJ mol−1 was determined, similar to the significant exotherms observed in our previous work for other binary systems. The experimental HE data were well correlated with a composition-dependent equation and the Peng-Robinson equation of state in conjunction with the conventional mixing rule.

Excess molar enthalpies for binary mixtures of cyclopentanone, cyclohexanone, or cycloheptanone with n-nonane at T = 298.15 K and atmospheric pressure

Excess molar enthalpies, HE, for the binary mixtures of cyclopentanone, cyclohexanone, or cycloheptanone with n-nonane were measured at T=298.15K and 0.1MPa, by means of a Setaram Tian-Calvet MS80 microcalorimeter. All the binary systems investigated show endothermic behaviour (positive values) over the whole mole fraction range. The molar excess enthalpies decrease as the size of the cycloalkanone increases. The experimental results of HE are fitted to the Redlich–Kister equation to correlate the composition dependence. The experimental HE data are also used to test the suitability of the Wilson, NRTL, and UNIQUAC models. The correlation of excess enthalpy data in these binary systems using the UNIQUAC model provides relatively the most appropriate results.

Single-electron capture by Al3+ions from rare gases

Theoretical cross sections for single-electron capture in collision of Al${}^{3+}$ ions with helium, neon, and argon targets have been calculated in the 10${}^{\ensuremath{-}2}$--2 a.u. velocity range (${E}_{\mathrm{lab}}$: 0.06 keV through 2.7 MeV). Calculations have been carried out by means of semiclassical collision methods based on multireference configuration interaction potential-energy curves and nonadiabatic couplings. Partial and total cross sections are given and the obtained results agree well with the available experimental data for He and Ar targets while those for neon are considered as prediction.

Hydrodynamic force measurements under precisely controlled conditions: Correlation of slip parameters with the mean free path

A customized atomic force microscope has been utilized in dynamic mode to measure hydrodynamic forces between a sphere and a flat plate, both coated with gold. In order to study the influence of the mean free path on slippage without systematic errors due to varying surface properties, all data have been acquired at precisely the same spot on the plate. Local accommodation coefficients and slip lengths have been extracted from experimental data for He, Ne, Ar, Kr, as well as N2, CO2, and C2H6, at Knudsen numbers between 3 × 10−4 and 3. We found that slippage is effectively suppressed if the mean free path of the fluid is lower than the roughness amplitude on the surface, while we could not observe a clear correlation between the accommodation coefficient and the molecular mass.

Excess molar enthalpies for binary mixtures of 1,2-dichloroethane with ethers at 298.15 K and atmospheric pressure

Excess molar enthalpies, HE, for the binary mixtures of 1,2-dichloroethane (1,2-DCE) with diethyl ether (DEE), methyl 1,1-dimethylethyl ether (MTBE), diisopropyl ether (DIPE), 1,3-dioxolane (1,3-DIOXO), 1,4-dioxane (1,4-DIOXA), tetrahydropyran (THP), ethylene glycol dimethyl ether (EGDME), diethylene glycol dimethyl ether (DEGDME), and diethylene glycol diethyl ether (DEGDEE), have been measured at 298.15K and atmospheric pressure, using a Setaram Tian-Calvet C80 microcalorimeter. All the binary systems investigated are characterized by exothermic mixing over the entire composition range, except for 1,2-DCE+DIPE which presents a S-shape HE behavior. The experimental HE data have been fitted to the Redlich–Kister polynomial equation.

Hydrogen recombination due to collisions with He and Ar

Quantum-mechanicalcalculationsarereportedforhydrogenrecombinationinthepresenceofachemicallyinert spectator. The calculations employ a square integrable Sturmian basis set to provide a discrete representation of the H2 continuum. Direct three-body recombination is approximated by computing transitions from the nonresonant continuum. Resonant and nonresonant states are handled on equal footing within the sequential two-step energy transfer mechanism. Theoretical rate coefficients are computed within the equilibrium and steady-state approximations for the density of intermediate molecules. The results are compared with existing experimental data for He and Ar. The sensitivity of the calculations to pressure variations and to changes in the potential energy surface are investigated for He. The reliability of these calculations and their relevance for astrophysical models are discussed. DOI: 10.1103/PhysRevA.83.042713

Excess Molar Enthalpies of Binary Systems of n-Valeric Anhydride or n-Hexanoic Anhydride with n-Dodecane, n-Tetradecane, or n-Hexadecane at 298.15 K

Excess molar enthalpies, HE, of binary mixtures of n-valeric anhydride or n-hexanoic anhydride with n-dodecane, n-tetradecane, or n-hexadecane were measured by an isothermal titration calorimeter at 298.15 K under atmospheric pressure. The experimental HE values are positive for all binary systems over the entire composition range. In these six investigated systems, the maximum values of HE exhibit at the composition ranging from 0.47 to 0.49 and 0.44 to 0.47 in the mole fraction of anhydrides for the mixtures containing n-valeric anhydride and n-hexanoic anhydride, respectively. The maximum values increase with increasing chain length of the alkanes for the mixtures containing a given anhydride. A Redlich−Kister equation correlated the experimental HE data to within the experimental uncertainty. The new enthalpy data were also correlated, respectively, with the Peng−Robinson (PR), the Patel−Teja (PT), and two versions of the cubic chain-of-rotators (CCOR) equations of state and the NRTL model as well. Th...

Salt effect on the enthalpy of mixing of 2-propanol + acetic acid at 303.15 K

Salt effect on the enthalpy of mixing of 2-propanol + acetic acid at 303.15 K This paper presents the effect of two dissolved inorganic salts (zinc chloride, ZnCl2 and ammonium chloride, NH4Cl) on the enthalpy of mixing (H E) of 2-propanol + acetic acid binary system measured at 303.15 K using an isothermal displacement calorimeter with vapour space. A decreasing trend in the excess enthalpy of mixing values in the presence of ZnCl2 and NH4Cl indicate the endothermic behavior of this system. The Redlich-Kister equation has been used to fit the experimental H E data. The deviations from the ideal value and binary parameters were calculated and reported.

Dissociative excitation due to collisions of electrons and helium ions with oxygen molecules

The absolute cross sections of luminescence related to atomic and ionic oxygen at dissociative excitation through e-O2 and He+-O2 collisions are determined. An intense OII line (83.4 nm) is discovered. For e-O2 collisions, a weak OIII line (70.5 nm) is found. Experimental data for He+-O2 collisions are qualitatively interpreted in terms of the quasi-diatomic approximation.

Simulation of the Hydrodynamics and Drying in a Spouted Bed Dryer

Gas–particle flow behavior in a spouted bed of spherical particles was simulated using the Eulerian–Eulerian two-fluid modeling approach, incorporating a kinetic–frictional constitutive model for dense assemblies of the particulate solid. The interaction between gas and particles was modeled using the Gidaspow drag model and the predicted hydrodynamics is compared with published experimental data. To investigate drying characteristics of particulate solids in axisymmetric spouted beds, a heat and mass transfer model was developed and incorporated into the commercial computational fluid dynamics (CFD) code FLUENT 6.2. The kinetics of drying was described using the classical and diffusional models for surface drying and internal moisture drying, respectively. The overall flow patterns within the spouted bed were predicted well by the model; i.e., a stable spout region, a fountain region, and an annular downcomer region were obtained. Calculated particle velocities and concentrations in the axisymmetric spouted bed were in reasonable agreement with the experimental data of He et al. (Can. J. Chem. Eng. 1994a, 72:229; 1994b, 72:561). Such predictions can provide important information on the flow field, temperature, and species distributions inside the spouted bed for process design and scale-up.

Equation of State of He-H2 and He-D2 Dense Fluid Mixtures at High Pressures and Temperatures

The fluid variational theory is used to calculate the Hugoniot equation of state (EOS) of He, D 2 , He + H 2 , and He + D 2 fluid mixtures with different He:H 2 and He:D 2 compositions at high pressures and temperatures. He, H 2 , and D 2 are the lightest elements. Therefore, the quantum effect is included via a first-order quantum correction in the framework of the Wigner-Kirk-wood expansion. An examination of the reliability of the above computations is performed by comparing experiments and calculations, in which the calculation procedure used for He and D 2 is adopted also for He + D 2 and He + H 2 , since no experimental data for the mixtures are available to conduct these comparisons. Good agreement in both comparisons is found. This result may be seen as an indirect verification of the calculation procedures used here, at least, in the pressure and temperature domains covered by the experimental data for He and D 2 used for comparisons, which is nearly up to 40 GPa and 10 5 K. Also, the equation of state of He + H 2 fluid mixtures with different compositions is predicted over a wide range of temperatures and pressures.

Computational fluid dynamics (CFD) modeling of spouted bed: Influence of frictional stress, maximum packing limit and coefficient of restitution of particles

Following the previous article [Du, W., Bao, X., Xu, J., Wei, W., 2006. Computational fluid dynamics (CFD) modeling of spouted bed: assessment of drag coefficient correlations. Chemical Engineering Science 61 (5), 1401–1420], this contribution describes the influences of the frictional stress, maximum packing limit and coefficient of restitution of particles on CFD simulation of spouted beds. Using the two-fluid method embedded in the commercial CFD simulation package Fluent 6.1, the spouting hydrodynamics of a cylindrical–conical spouted bed was simulated and verified with the experimental data of He et al. [He, Y.L., Lim, C.J., Grace, J.R., Zhu, J.X., Qin, S.Z., 1994a. Measurements of voidage profiles in spouted beds. Canadian Journal of Chemical Engineering 72 (4), 229–234; He, Y.L., Qin, S.Z., Lim, C.J., Grace, J.R., 1994b. Particle velocity profiles and solid flow patterns in spouted beds. Canadian Journal of Chemical Engineering 72(8), 561–568]. The results showed that, for coarse particles, the frictional stress is important only for the annulus computation and has no obvious effects on the hydrodynamics of the solids flow in the spout region. The specification of the maximum packing limit could significantly affect the properties of the pseudo-fluid phase of the particles by changing the radial distribution function. The strong dependence of the pseudo-fluid properties of the particle phase, such as pressure, bulk viscosity and shear viscosity, on the granular temperature accounts for the influence of the coefficient of restitution of particles on CFD modeling. The solids volume fraction at loose packing state is suitable for spouted bed simulations, and a pretest of the coefficient of restitution of particles must be conducted when no experimental datum is available.

Computational fluid dynamics (CFD) modeling of spouted bed: Assessment of drag coefficient correlations

In the computational fluid dynamics (CFD) modeling of gas–solids two-phase flows, drag force is the only accelerating force acting on particles and thus plays an important role in coupling two phases. To understand the influence of drag models on the CFD modeling of spouted beds, several widely used drag models available in literature were reviewed and the resulting hydrodynamics by incorporating some of them into the CFD simulations of spouted beds were compared. The results obtained by the different drag models were verified using experimental data of He et al. [He, Y.L., Lim, C.J., Grace, J.R., Zhu, J.X., Qin, S.Z., 1994a. Measurements of voidage profiles in spouted beds. Canadian Journal of Chemical Engineering 72 (4), 229–234; He, Y.L., Qin, S.Z., Lim, C.J., Grace, J.R., 1994b. Particle velocity profiles and solid flow patterns in spouted beds. Canadian Journal of Chemical Engineering 72 (8), 561–568.] The quantitative analyses showed that the different drag models led to significant differences in dense phase simulations. Among the different drag models discussed, the Gidaspow (1994. Multiphase Flow and Fluidization, Academic Press, San Diego.) model gave the best agreement with experimental observation both qualitatively and quantitatively. The present investigation showed that drag models had critical and subtle impacts on the CFD predictions of dense gas–solids two-phase systems such as encountered in spouted beds.

New contribution to study on stark broadenings of 5870.90 Å KR(I) spectral lineshape in dense cold plasmas including levels of like and unlike parentage interactions ( [formula omitted], [formula omitted

In the present paper, we extend our previous Stark broadening calculations, giving significant and good agreements with experimental data of He(I) and Ar(I) spectral lineshapes, to the 5870.90 Å Kr(I) line. In particular, using the appropriateness of the N–N approximation for the many electrons atoms and the possibility to estimate the contributions of interacting levels of like and unlike parentage, we perform for every experimental conditions theoretical profiles whose shifts and half-widths rigorously match with experimental ones, the values always lying into their margins of error. Finally, it seems possible to present as a “quasi-universality’’ the strong complementarity between the parameter linked to the electron screening upper cut-off ρ max and the parameter associated to the rate of interaction between like and unlike parentage levels. Moreover, relations between the electron density N e and these parameters are found on the basis of the good fitting between experimental and theoretical profiles.

Excess Molar Enthalpies for Dimethyl Carbonate with o-Xylene, m-Xylene, p-Xylene, Ethylbenzene, or Ethyl Benzoate at 298.15 K and 10.2 MPa

A flow-type isothermal microcalorimeter was used to measure excess molar enthalpies, HE, for the binary mixtures of dimethyl carbonate with o-xylene, m-xylene, p-xylene, ethylbenzene, or ethyl benzoate at 298.15 K and 10.2 MPa. The experimental HE values are positive for all the binary mixtures over the entire composition range. In comparison with the values of HE at 0.1 MPa, the excess enthalpies were found to decrease with increasing pressure for these binary systems, except for dimethyl carbonate + ethylbenzene. The maximum HE values are in the range 356.8 J·mol-1 to 652.8 J·mol-1, which are located at about xi = 0.5. The experimental HE data were correlated accurately with the Redlich−Kister polynomial equation. The Peng−Robinson and the Cubic Chain-of-Rotators equations of state with the binary interaction parameters determined from HE data at atmospheric pressure were adopted to calculate the excess enthalpies at 10.2 MPa. The Cubic Chain-of-Rotators equation with two binary interaction parameters y...

Doubleionization of helium-like ions by electron impact:from fully differential to total cross section

Using a wavefunction with the radial correlation only for the boundelectrons and a correlated double-continuum wavefunction for the ejectedelectrons, an analytical expression is obtained in the Born approximationfor the fully differential cross section of double ionization of helium-likeions by electrons. The result is found within the framework of theshake-offmodel considering only the radial correlation of electrons in the target.An analytical expression is obtained for the fourfold differential crosssection following integration of the fully differential cross section overthe solid angles of the ejected electrons. For the first time the totalcross sections (TCS) are calculated for direct double ionization oftwo-electron atomic systems from H-(Z = 1)to N5+(Z = 7). Thecalculations are carried out for energies extending up to a maximum 200times the double-ionization threshold. The calculated values of TCS arefound to be in fair agreement with the available experimental data forHe and Li+. Disagreement between theory and experiment isdiscussed. TCS are found to be very sensitive to the inclusion of repulsionbetween the ejected electrons in the final state.

Computational models for multiphonon scattering from surfaces: applications to He scattering from insulators

We consider the inelastic interaction of a neutral atomic projectile scattering from a solid surface. Several computational models are developed to analyze the diffuse multiphonon component in the scattered intensity. Through extensive numerical calculations we determine the validity ranges of these approximations. Comparisons with experimental data for He scattering from LiF(001) and KCN(001) provide examples of the applicability of these theoretical approximations.

Prediction of vapor‐liquid equilibrium data from excess enthalpy data for alkanol/alkane mixtures by the extended real associated solution model

AbstractThe prediction of Vapor‐liquid Equilibrium data (VLE) from excess enthalpy data (HE) for alkanol/alkane mixtures by means of the Hanks‐Gupta‐Christensen (HGC) method is examined. The Extended Real Associated Solution model (ERAS) for the excess Gibbs energy which combines the Kretschmer‐Wiebe linear association model with Flory's equation of state for chainlike molecules is used. In this prediction, the parameters of the ERAS model are evaluated by fitting the experimental HE data to the algebraic equation for the HE of this model. Results from this study indicate that the ERAS model leads to VLE predictions which are more accurate than those previously obtained when the HGC method was used in conjunction with the Continuous Linear Association model or the Wiehe‐Bagley model.