Consistency of Thermodynamic Properties from CHEMCAD Process Simulations

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. It is important to be able to rely on the accuracy of these calculations. Furthermore, students of thermodynamics and process engineers must be able to easily reproduce the calculations from the process simulator. In this study, we attempted to validate the compressibility factors, enthalpy, entropy, and fugacity coefficients from CHEMCAD by comparing the results of the process simulator to results from a published solution algorithm [2] . Our results show good consistency for most molecules. However, we observe large deviations for nitric oxide, water and hydrogen, and somewhat smaller deviation for a few other molecules. This report presents a detailed comparison of the thermodynamic properties of 48 molecules at two different states to demonstrate that our calculation is correct and that the deviations for hydrogen and water are real. 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.