PYTERMO - AN OPEN-SOURCE PYTHON PROGRAM FOR THERMODYNAMIC PROPERTIES DETERMINATION, USING THE LEE- KESLER GENERALIZED EQUATION OF STATE.

In project, analysis and optimization of thermal systems it is very important to be able to automatically obtain the thermodynamic properties of the working fluids at any time as the systems evolve between states. Unfortunately, property evaluation could be very onerous if done through thermodynamic chart lookups. However a quite accurate answer, at least for pure substances, can be obtained, determining the thermodynamic properties using a suitable generalized equation of state and some computational methods. According to that idea, Lee and Kesler suggested a modification of the Benedict-Webb-Rubin Equation of State, able to correlate the thermodynamic behavior of pure substances in compressed liquid, superheated vapor and liquid-vapor mixture states, from their critical temperature, critical pressure and Pitzer's acentric factor, as well as the coordinates of the actual state. There are some packages in the literature employing the same foundations, almost all closed source. The present code has been developed in Python as part of a much larger simulation program, although it may be used standalone. Python has been chosen as a multiplataform object-oriented open-source programming language, exhibiting very readable and powerful syntax. In order to validate both the methodology and the code, several results from the literature are compared, for water, hydrocarbons and refrigerants.