Thermodynamic Properties of pure methane using Peng Robinson cEOS for GAMS

Abstract

Dynamic Link Library with functions for calculating thermodynamic properties of pure methane in the equation-oriented optimization software GAMS (General Algebraic Modeling System). The library is based on the Peng-Robinson cubic equation of state. The properties that can be calculated include enthalpy, entropy, density, and fugacity. For all cases, there are two versions of each function: one designed for the vapor phase, which selects the largest root of the cubic polynomial, and another for the liquid phase, which selects the smallest root. In regions with a single real root, 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 gradient and analytical Hessian matrix. It should be included using the $funcLibIn command (see GAMS help).