Showing papers on "Gibbs–Duhem equation published in 2017"

Evaluation Model for Viscosity of Fe–Ni–Cr Alloys Using Gibbs Free Energy of Mixing and Geometric Methods

Abstract: Thermo-physical properties of these liquid metals, such as heat capacity, thermal conductivity, surface tension, density and viscosity are of particular interest because these properties play important roles in heat and mass transport processes. Knowledge of the viscosities1–7) of pure liquid metals and respective mixtures is important for practical and theoretical purposes. Furthermore, the viscosity of multicomponent8,9) liquid mixtures is an invaluable type of data for the chemical engineer in the design and optimization of industrial processes, particularly for the smelting, casting and welding processes of Fe-based alloys and stainless steels. Therefore, it is very important to obtain a precise and reliable viscosity, especially for high melting point alloys from the industrial point of view. Proposed methods for the measurement of the viscosity include: capillary, oscillating vessel, rotational bob or crucible, oscillating plate, draining vessel, levitation using the damping of surface oscillations and acoustic methods. It is well known that the measurement of the viscosity of molten metals, especially at high temperatures, is difficult because of the reactivity with the crucibles and atmosphere, and also the sensor limitation of the low viscosity. Compilations of the viscosities of pure liquid metals at different temperatures, as well as those of binary liquid mixtures through the whole composition range, Evaluation Model for Viscosity of Fe–Ni–Cr Alloys Using Gibbs Free Energy of Mixing and Geometric Methods

On the relationship between microcanonical and canonical Gibbs distributions

Abstract: It is established that the agreement between the use of microcanonical and canonical Gibbs distributions is possible only if the temperature of a closed equilibrium system and its specific energy in a thermostat are mutually inverse functions. The analysis shows that the derivation of the canonical Gibbs distribution from the microcanoncial does not agree with the physical condition for separating a macroscopic part of a closed equilibrium system.

A Reaction Method for Estimating Gibbs Energy and Enthalpy of Formation of Complex Minerals

Abstract: New and updated thermodynamic data for simple binary compounds are readily available from both experimental measurements and theoretical calculations. Based on these available data, an approach is proposed to predict Gibbs energies and enthalpies of formation for complex minerals of metallurgical, chemical, and other industrial importance. The approach assumes that complex minerals are formed from binary composite oxides, which in turn, are formed from individual pure oxides. The validity of this approach is examined by comparing the calculated values of Gibbs energies and enthalpies against the experimentally measured ones reported in literature. The results show that for typical complex minerals with available experimental data, the calculated results exhibit an average residual of 0.51 pct for Gibbs energies and 0.52 pct for enthalpies, compared to the experimental results. This new approach thus correlates well with experimental approaches and can be applied to most of the complex minerals.

Analytic gibbs-duhem correction for quasi-chemical models with composition dependent interactions

Abstract: A method for simulation, in particular for computerized calculation, of at least one physical property of a system of one or more chemical species that includes at least one chemical species dissolved in at least one chemical species, using a quasi-chemical, COSMO-RS, COSMO-SAC, or COSMOSPACE calculation involving composition dependent segment interactions and achieving Gibbs-Duhem consistent chemical potentials and activity coefficients or Gibbs-Duhem consistent chemical potentials or Gibbs-Duhem consistent activity coefficients. According to the invention, either at least one uncorrected segment activity coefficient or at least one segment contacting probability resulting from an initial quasi-chemical, COSMO-RS, COSMO-SAC or COSMOSPACE calculation is used as an input variable as for the calculation, or at least one uncorrected segment activity coefficient and at least one segment contacting probability resulting from the initial quasi-chemical, COSMO-RS, COSMO-SAC or COSMOSPACE calculation are used as input variables as for the calculation.

A feature in deriving the Gibbs distribution from the entropy maximum principle

Abstract: It is proved that, in the general case, the Gibbs distribution may not provide an entropy maximum.

Chemical potential, Gibbs–Duhem equation and quantum gases

Abstract: Thermodynamic relations like the Gibbs–Duhem are valid from the lowest to the highest temperatures. But they cannot by themselves provide any specific temperature behavior of thermodynamic functions like the chemical potential. In this work, we show that if some general conditions are attached to the Gibbs–Duhem equation, it is possible to obtain the low temperature form of the chemical potential for the ideal Fermi and Bose gases very directly.

Basics of Thermodynamics—Derivatives of Gibbs Energy, G

Abstract: The combination of the first and a half of the second laws of thermodynamics results in the starting equation. Then the concept of entropy is introduced. On the other hand, by using the “order theoretical” approach by Giles, we show that the same starting equation results. We develop mathematically and give naturally the enthalpy and Gibbs free energy, G . Then all thermodynamic quantities are shown to be expressed as a derivative of G with respect to the independent variables ( p , T , n i ) of the system. The list is provided for possible thermodynamic quantities in terms of the various order of derivatives, some of which could be used in the future.