Comparison of Pure Component Thermodynamic Properties from CHEMCAD with Direct Calculation using the Peng-Robinson Equation of State

Abstract Accurate calculations of properties such as enthalpy, entropy, and fugacity are crucial for chemical process design. These properties are calculated from equations of state in commonly used process design software such as CHEMCAD [1] and software-based calculations of properties have been routine for decades. Correct application of chemical thermodynamics is a requirement for successful process simulations and it is important to be able to rely on the accuracy of these calculations. To verify choices made during the development of a simulation, students and process engineers must be able to easily reproduce the calculations. In a previous study [4] , we validated the compressibility factors, enthalpy, entropy, and fugacity coefficients from CHEMCAD by comparing the results of the process simulator to results obtained independently from the Lee-Kesler method. In this paper, we extend our study to include the Peng-Robinson equation of state [5] . This report presents a detailed comparison of the thermodynamic properties of 48 molecules at two different states. Our results show good consistency for most of these molecules. We observe deviations for hydrogen, nitric oxide, and water. For absolute (stream) enthalpies, we observe deviations for air, chlorine, nitrogen, oxygen, and water. For absolute (stream) entropies, we observe deviations for hydrogen, hydrogen chloride, nitric oxide, and water. The views expressed herein are those of the authors and do not reflect the position of the United States Military Academy, the United States Department of the Army, or the United States Department of Defense.