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The isothermal flash problem: New methods for phase split calculations
Author(s) -
Ammar M. N.,
Re H.
Publication year - 1987
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690330606
Subject(s) - maxima and minima , minification , convergence (economics) , gibbs free energy , isothermal process , computer science , flash evaporation , nonlinear system , mathematics , mathematical optimization , energy (signal processing) , algorithm , equation of state , thermodynamics , mathematical analysis , statistics , physics , quantum mechanics , economics , economic growth
Various numerical approaches have been adopted to solve the single‐stage isothermal flash problem. These approaches result in two classes of methods. The first includes equation‐solving methods that try to solve a nonlinear equation system; the second is based on a minimization of the total Gibbs free energy. Most of these methods may fail to find a solution or may lead to erroneous solutions near critical conditions when an equation of state is applied to both the vapor and liquid phases. New methods for solving the problem are proposed. Combining the simplicity in structure of the conventional successive‐substitution method and the efficiency of some unconstrained minimization algorithms, they all ensure convergence to local minima of the Gibbs free energy. The new methods are compared from the standpoints of computer storage and calculational effort requirements. The performance of these methods is tested on four multicomponent systems taken from literature, and a comparison is made with other published methods.