Thermodynamic Properties of the oxygen-nitrogen mixture using Peng Robinson cEOS for GAMS

Abstract

Dynamic link library with functions for calculating the thermodynamic properties of an oxygen-nitrogen mixture (air) in the equation-oriented optimization software GAMS (General Algebraic Modeling System). The library is based on the Peng-Robinson cubic equation of state and the supported compounds are oxygen and nitrogen. The properties that can be calculated are the enthalpy, entropy, density, and fugacity of each component in the mixture. For all cases, there are two versions of the function, one for the vapor phase that selects the largest root of the cubic polynomial and another for the liquid phase that chooses the smallest. In single real root zones, both functions yield the same result. When calling the library, the included functions and the units used can be observed. The library was implemented in the C programming language and all its functions include their corresponding analytical gradient and Hessian matrix. It must be included using the command $funcLibIn (see GAMS help).