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1.
The calculation of the thermodynamical properties in the liquid-gas region
Jurij Avsec, Milan Marčič, 1999, original scientific article

Abstract: The paper features the mathematical model of computing phase diagrams and thermodynamic functions of the state in the liquid, gas and two phase domain with the help of statistical thermodynamics. The paper features all important contributions (translation, rotation, internal rotation, vibration, intermolecular potential energy and influenceof electron and nuclei excitation). To calculate the thermodynamic properties of real gases we developed the cluster theory, which yields better results than the classical virial equation. For the realm of real liquids the Johnson-Zollweg-Gubbins model basedon the modified Benedict-Webb-Rubin eqution was applied. The Lennard-Jones intermolecular was used. The analytical resulats are compared with the thermodynamical data and models obtained by classical thermodynamics and show relatively good agreement.
Keywords: thermodynamic, statistical thermodynamic, liquid-gas, thermodynamic properties
Published in DKUM: 10.07.2015; Views: 1004; Downloads: 89
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2.
Calculation of thermophysical and thermochemical properties during hydrocarbon combustion
Jurij Avsec, Franc Zgaga, Milan Marčič, 2002, original scientific article

Abstract: A mathematical model is presented for computing the chemical and thermophysical properties in the process of combustion of natural gas. To identify the parameters of state of combustion products, their composition hasto be known, which may be determined from chemical equilibrium. The computation is performed with the use of chemical potentials and statistical thermodynamics, featuring all important molecular contributions (translation, rotation, vibration, and intermolecular potential energy). A thermal equation of state with two virial terms is used. The real gas mixture is treated as consisting of four components: carbon dioxide, nitrogen, carbon monoxide, and water. Virial coefficients are dependent on temperature and mole fractions of the real components. Mixed terms are taken into account. The caloric equation of state is based on statistical thermodynamics for an ideal gas. Corrections are made in accordance with the second law of thermodynamics and the thermal equation of state. As the whole computation is based on matrix algebra, increasing the number of components presents no problems. We tested our model in the high-pressure region (100 bar) and the low-pressure region (1 bar), in the temperature range 500 - 6000°K. Our model is compared with other analytical models presented in the literature and shows relatively good agreement. At the same time we tested the influence of real conditions on the chemical and thermophysical properties of combustion products.
Keywords: statistical thermodynamics, thermodynamical properties, combustion of natural gas, mathematical models, thermodynamic functions of state, equation of state, virial coefficients
Published in DKUM: 01.06.2012; Views: 2294; Downloads: 120
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3.
Statistical approach to calculate thermodynamic properties for propane
Jurij Avsec, K. A... Watanabe, 2005, original scientific article

Abstract: The paper describes a mathematical model to compute equilibrium thermodynamic properties in the fluid phase of pure hydrocarbons with the aid of classical thermodynamics and statistical associating chain theories. In the present paper thermodynamic properties for propane, as an example of hydrocarbon substances, are calculated. To calculate the thermodynamic properties of real fluids, models based on the Lennard-Jones intermolecular potential were applied. To calculate the thermodynamic properties of real fluids with the aid of classical thermodynamics, Miyamoto-Watanabe (MW) equations, developed in terms of the Helmholtz energy were used. Analytical results obtained by statistical thermodynamics are compared with the MW model and show relatively good agreement.
Keywords: statistical thermodynamics, propane, thermodynamic properties, SAFT model, chain theory
Published in DKUM: 01.06.2012; Views: 1855; Downloads: 84
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4.
The combined analysis of phonon and electron heat transfer mechanism on thermal conductivity for nanofluids
Jurij Avsec, 2008, original scientific article

Abstract: The paper features the mathematical model representing the analytical calculation of phonon and electron heat transfer analysis of thermal conductivity for nanofluids. The mathematical model was developed on the basis of statistical nanomechanics. We have made the detailed analysis of the influence of temperature dependence on thermal conductivity for nanofluids. On this basis are taken into account the influences such as formation of nanolayer around nanoparticles, the Brown motion of solid nanoparticles and influence of diffusive-ballistic heat transport. The analytical results obtained by statistical mechanics are compared with the experimental data and they show relatively good agreement.
Keywords: statistical nanomechanics, phonons, electron heat transfer, nanofluids, thermal conductivity, thermodynamic properties, mathematical model, statistical nanomechanics
Published in DKUM: 31.05.2012; Views: 2578; Downloads: 120
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5.
The calculation of thermal conductivity, viscosity and thermodynamic properties for nanofluids on the basis of statistical nanomechanics
Jurij Avsec, Maks Oblak, 2007, original scientific article

Abstract: The paper features the mathematical model of calculation of thermophysical properties for nanofluids on the basis of statistical nanomechanics. Calculation of properties for nanofluids for real substances is possible by the classical and statistical mechanics. Classical mechanics has no insight into the microstructure of the substance. Statistical mechanics, on the other hand, calculates the properties of state on the basis of molecular motions in a space, and on the basis of the intermolecular interactions. The equations obtained by means of classical thermomechanics are empirical and apply only in the region under observation. The main drawback of classical thermomechanicsis that it lacks the insight into the substance of microstructure. Contrary to classical mechanics, statistical mechanics calculates the thermomechanic properties of state on the basis of intermolecular and intramolecular interactions between particles in the same system of molecules. It deals with the systems composed of a very large number of particles. The results of the analysis are compared with experimental data and show a relatively good agreement. The analytical results obtained by statistical mechanics are compared with the experimental data and show relatively good agreement.
Keywords: statistical thermodynamics, thermophysical properties, viscosity, thermal conductivity, thermodynamic properties, mathematical model, nanofluids, statistical nanomechanics
Published in DKUM: 31.05.2012; Views: 2341; Downloads: 140
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