The Development Of Phase Equilibrium Database Software

Chemical process simulation and optimization has become a useful tool inchemical engineering design saving energy and improving economic effectivenesswith the rapid development of computer application technology. In the flow simulationprocess, the calculation of phase equilibrium data is following as necessary. Soestablishing phase equilibrium database software in the flow simulation system whichhas general and special-purpose at one time is essential. This software should becomposed by a large phase equilibrium database and data processing module. Thesoftware not only can accurately provide vapor-liquid equilibrium data and completethe parameter estimating of thermodynamics models, but also can calculate bubble anddew point, to meet the flow simulation and the engineering calculation needs.Taking the versatility and practicality of computer system into account, thesoftware choose binary file written by FORTRAN as the database backend. Thedatabase composed of two parts, one is the system database containing the basicphysical parameters of510kinds of compounds, and13400vapor-liquid equilibriumdata and model parameter of these compounds, the other is the user database which isused for user to expand personal data.Firstly this paper points out some methods limitation by generally analyzing eachkind of optimization methods development and their application in chemicalcalculation. Established using the simplex method to regression thermodynamic modelparameters and Newton-Raphson combined with Secant method to calculate bubbleand dew point. Based on the depth study and research of the simplex method in theparameter regression and Newton-Raphson combined with Secant method in bubbleand dew point we established thermodynamic equation of state binary interactionparameter regression model, the regression model of the activity coefficient modelparameters and the saturated vapor pressure equation coefficients regression model and the bubble point and dew point calculation model. In the parametric regression modulebased on vapor-liquid equilibrium data of binary systems under certain temperatureand pressure, we estimated model parameters, and projections to the vapor-liquidequilibrium data of the binary systems, compared with the experimental data, showedthat using simplex method to return thermodynamic model parameters has goodconvergence and high accuracy, and further illustrates the use of the simplex regressionmodel parameters is feasible. In the bubble dew point calculation module, throughcompared the calculation results with function transformation method and secantmethod showing that Newton-Raphson combined with secant method convergence ismore rapid and result is more accurate.In the summary of these four modules and the basis of work of previous, usingFORTRAN programming language we developed and refined the four modules. Thenusing the object-oriented programming language C++MFC, we developed the interfaceof data management, parametric regression module and bubble point and dew pointcalculation. Finally, using the assembly language technology, we compile the fourFortran program into dynamic link library file, and added these file to the directory ofC++program, accomplished the use of phase equilibrium database software in thewindows environment.The development of the database software has great practical value. The softwarenot only has a general database management function, but also has a model for thetypical parametric regression, and can be used as a part added to the other chemicalprocess simulation software, to extend its capabilities to better meet the needs ofchemical process simulation.