Vaporization Thermodynamic Properties Research Articles

Thermodynamic study of alkane-α,ω-diamines – Evidence of odd–even pattern of sublimation properties

Calculated ideal-gas heat capacities and experimental data for vapor pressure, condensed phase heat capacities, and calorimetric vaporization enthalpies of alkane-α,ω-diamines, NH2-(CH2)n-NH2 (2≤n≤8), were treated simultaneously to obtain a consistent thermodynamic description. Vapor pressures for the members with 3≤n≤8 were measured using the static method in the temperature range from 233 to 314K. The thermodynamic properties in the ideal gaseous state for the members with n=2 and 3 were obtained using the fundamental vibrational frequencies, molecular structure data, and potential energy profiles of internal rotations calculated using the density functional theory (DFT) at the B3LYP/6-311+G(d,p) level of theory and four statistical thermodynamic models of different complexity. Based on the results of the simultaneous correlation, the sublimation and vaporization thermodynamic properties for 2≤n≤8 and the triple-point coordinates for n=3, 4, 5 and 7 were calculated. The thermodynamic properties for liquid–vapor equilibrium display a linear dependence on number of methylene groups n while the sublimation thermodynamic properties show an evident odd–even effect with higher values for even members of a homologous series. The alternating pattern is interpreted on the basis of the literature crystallographic data and corresponding intermolecular interactions. Based on the observed trends, the correlations allowing the prediction of the thermodynamic properties for the crystal–vapor and liquid–vapor equilibria and crystalline and ideal-gas heat capacities within the homologous series are suggested.

Simulation of two-region and four-region models for typical PWR pressurizer and benchmark obtained results using available results

In light water pressurized reactors, pressurizer plays an important role in controlling the coolant pressure during in-surge or out-surge transients. Increase and decrease coolant mass flow rate or specific volume leads to in-surge or out-surge transient, which changes pressurizer tank’s pressure. There are different thermodynamic models, which are predicted the pressurizer surge tank’s pressure, water and vapor properties in different times. In the present article, two-region and four-region thermodynamic models were used for simulation of typical PWR pressurizer and the calculated results were benchmarked with RELAP5/Mod3 code findings. Finite difference method is applying to differential equations’ analytical solving. Water and vapor thermodynamic properties are calculating according to IAPWS-IF97 (International Association for the Properties of Water and Steam) correlations in each time steps. Try and error method is using for pressure estimations. The pressure results are compared and show that accuracy of the presented models are acceptable and deviations from RELAP code results are justifiable.

Thermal Diffusivity as an Automotive Fuel Characterization Parameter: Correlation with Motor Octane Number

The standard method for evaluating the quality of automotive fuels is based on the determination of its motor octane number (MON) using the ASTM motor testing. The resulting figures of merit of this standard testing are known to be strongly linearly correlated to the fuels' vapor thermodynamic properties such as, for instance, their vapor pressure. In this paper we explore this strong correlation between the MON parameter and the fuels' vapor thermal properties to seek the development of an alternative low-cost method. The proposed method is based upon the photothermal measurement of the thermal diffusivity of the fuels' vapor in a closed air cell. It is found that the thermal diffusivity is well correlated with the corresponding MON values of the fuels investigated. The eventual improvements of the proposed method aimed at gaining accuracy and developing a portable device for field applications are also discussed.

Thermodynamics of Gaseous Species in the Sodium‐Scandium‐Iodine System

The vaporization behavior of , , and mixtures of these two phases containing 50, 92, 95, and 98 mole percent (m/o) has been studied by effusion‐beam mass spectrometry and by torsion‐mass‐effusion techniques in the approximate region 700–900 K. Vapor molecular weights show that and monomers make up 84 and 94 m/o, respectively, of the saturated vapors over the pure phases with the balance primarily dimer. is the major gaseous species over the mixtures, with a small amount of also present. Total vapor pressures of the pure phases and the mixtures were determined by the torsion method, and the enthalpies of sublimation of the monomer and dimer species over and were determined. The total vapor pressures of molten and the mixtures were also measured in the 10−2–10−1 atm range by the TGA boiling point method, and vapor mass spectra were used to estimate the activities of and in the liquid mixtures. Additionally, gaseous equilibria involving as well as the lower valent species and were studied by mass spectrometry. Vapor thermodynamic properties were derived and are compared with results in the literature.

PVT surface and thermodynamic properties of isopentane

A number of correlational studies presents both vapor liquid coexistence and superheated vapor thermodynamic properties of n-butane. The present compilation is part of a general revision of the j-Tables of API Research Project 44 (31) for C/sub 1/-C/sub 5/ alkanes. Selected values of vapor pressure, specific volume, enthalpy, and entropy are presented for saturated liquid and vaporous n-butane from the normal boiling point (272.67/sup 0/K) to the critical point (425.16/sup 0/K). Tabular data show the following: (1) physical and conversion constants used in this investigation; (2) critical constants of n-butane; (3) saturated properties of n-butane; (4) comparison of enthalpies of vaporization; (5) comparison of saturated liquid enthalpies; (6) comparison of saturated liquid entropies; (7) constants for the DR-BWR equation; (8) condensed thermodynamic properites of n-butane; (9) compressibility factors from corresponding states; and (10) second virial coefficients. (37 refs.)