A NEW OBJECT-ORIENTED LIBRARY FOR CALCULATING ANALYTICALLY HIGH-ORDERMULTIVARIABLE DERIVATIVES AND THERMODYNAMIC PROPERTIES OF FLUIDS WITHEQUATIONS OF STATE

A new global approach for calculating thermodynamic properties of flui ds with equations of state is proposed. This method uses an object-ori ented library, written in C++, and containing a number of routines tha t facilitate thermodynamic calculations. It is applicable to any equat ion of state formulated by an analytical expression of the Helmholtz f ree energy. The programming work of the user is limited to the buildin g of a parse representation of the Helmholtz free energy. This parse g raph is then processed by the program for analytically calculating the required derivatives and thermodynamic properties of fluids. A demons tration of this library is made with the Anderko and Fitter equation o f state for H2O-NaCl-KCl fluids. The Helmholtz free energy has been di fferentiated analytically up to the fourth order with respect to the t emperature, molar volume, and composition. Calculated derivatives are used to calculate the critical line of H2O-NaCl mixtures and other the rmodynamic properties, which otherwise would be difficult to obtain. C opyright (C) 1996 Elsevier Science Ltd