Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
Thermodynamic Properties Calculation of Pure Compounds Using a Multiobjective Approach in Estimating the Adjustable Empirical Parameters of the GEOS3C Equation of State
Submission Author:
Géssica Ramos da Silva , RJ
Co-Authors:
Géssica Ramos da Silva, Tania Galo, Nélio Henderson, Acir Moreno Soares Jr.
Presenter: Géssica Ramos da Silva
doi://10.26678/ABCM.COBEM2021.COB2021-0218
Abstract
For many engineering applications, especially in the simulation of phase equilibrium problems, thermodynamic properties can be estimated accurately in situations where there is no reliable experimental data through an equation of state. Since van der Waals' first publication, a lot of equations of state have been proposed to represent the PVT behavior of pure compounds, as is the case with GEOS3C, which is a new form of generalized cubic equation of state that uses a temperature function dependent on three adjustable empirical parameters. In this context, a modified MOPSO algorithm, that uses the e-dominance criteria to avoid problems of purely numerical dominance, a simplified storage management system to promote a better particles distribution and a fixed global leadership for a certain number of iterations, was employed to estimate the temperature's function parameters of GEOS3C equation of state that lead to the lowest errors of vapor pressure and saturated liquid volume compared to synthetic experimental data. This method has the main advantage to provide a set of solutions that show the existing conflict in the attempt to minimize the properties of interest in the optimization process. Substances from different chemical families were used to evaluate the methodology proposed in this work and comparisons against experimental data available in the literature were made, using the parameters obtained through multiobjective optimization for the calculation of the following thermodynamic properties: saturated liquid volume, saturated vapor volume, enthalpy of vaporization, entropy of vaporization, internal energy of vaporization, heat capacity at constant pressure of vaporization and heat capacity at constant volume of vaporization. The results showed that the new values obtained for the adjustable parameters of the GEOS3C equation of state provide better predictions for the thermodynamic properties in almost all cases tested. In particular, for the properties that were directly used in the optimization process, it can be noticed a significant improvement in minimizing the errors. In addition, in the viable region of the obtained Pareto fronts, it was possible to observe a correlation between the temperature's function parameters of GEOS3C equation of state: C1 assuming a constant value in relation to C2 and C3, whereas the two later are linearly dependent on each other.
Keywords
equations of state, parameter estimate, multiobjective optimization, thermodynamic properties
