1. Estimation of solid solubilities in supercritical carbon dioxide: Peng-Robinson adjustable binary parameters in the near critical regionMojca Škerget, Zorka Novak-Pintarič, Željko Knez, Zdravko Kravanja, 2002, original scientific article Abstract: The density dependence of the binary parameters of the Peng-Robinson equation of state in near the critical region was examined. Published solubility data of eight compounds in pure CO2 have been fitted to the Peng-Robinson equation in combination with one and two parameters van der Waals mixing rules and in combination with the three parameter density dependent mixing rule of Mohamed and Holder. A systematic study has been done to determine the influence of different terms in the mixing rules. In order to obtain density dependence, binary parameters were calculated for each isotherm at particular experimental point separately in the way to equalise experimental and calculated solubility data. The system was formulated as an equation-oriented model and solved by means of a nonlinear programming optimisation algorithm. For all compounds the binary interaction parameters thus obtained were found to vary strongly with pressure in the range from 75 bar to approximately 150 bar, i.e. near the critical end point (CEP) of the low temperature branch of the three phase solid-liquid-gas (SLG) curve. At higher pressures, the parameter is practically independent on pressure. In general, for the systems investigated, kij increases linearly with increasing density and reaches a constant value at higher densities in the range from 700 to 800 kg/m3, depending on the system under investigation. Keywords: solid liquid equilibria, equation of state, mixing rules, binary parameters, near critical region, nonlinear programming, thermodynamic model, supercritical fluids, CO2, solubility Published in DKUM: 01.06.2012; Views: 2198; Downloads: 117 Link to full text |
2. Statistical approach to calculate thermodynamic properties for propaneJurij 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: 1787; Downloads: 83 Link to full text |
3. The combined analysis of phonon and electron heat transfer mechanism on thermal conductivity for nanofluidsJurij 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: 2493; Downloads: 119 Link to full text |
4. The calculation of thermal conductivity, viscosity and thermodynamic properties for nanofluids on the basis of statistical nanomechanicsJurij 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: 2266; Downloads: 138 Link to full text |