Data for: Comparison of Pure Component Thermodynamic Properties from CHEMCAD with Direct Calculation using the Soave-Redlich-Kwong Equation of State
These calculations accompany the paper “Comparison of Pure Component Thermodynamic Properties from CHEMCAD with Direct Calculation using the Soave-Redlich-Kwong Equation of State," submitted to Chemical Data Collections, to replicate the data in the paper. Abstract of Original Paper: Properties such as gas-phase enthalpy, entropy, and fugacity are routinely calculated with equations of state in process design software such as CHEMCAD. To verify understanding of the underlying principles as well as the fidelity of the simulation, users must be able to reproduce the thermodynamic calculations in the simulator. In a previous study, we examined the compressibility factors, enthalpy, entropy, and fugacity coefficients from CHEMCAD using the Lee-Kesler method [2,3]. After observing a few anomalies, we extended the study to include the Peng-Robinson equation of state [4,5], observing similar anomalies. We also reported that compressibility and fugacity coefficients did not change when the equation of state was changed . We therefore further extended our study to include the Soave-Redlich-Kwong (SRK) equation of state and again compare the properties of the same 48 molecules at the same two different states. Our results show good consistency for most of these molecules, with percent errors decreasing for the SRK method to generally less than .2% compared to about 1% for the Lee-Kesler  and Peng-Robinson  methods. For percent error, we see deviations for nitric oxide, styrene, carbon disulfide, and hydrogen. For absolute differences, we see deviations for air, hydrogen sulfide, ethylbenzene, formaldehyde, and chlorine. Unlike the previous two studies, we now see agreement for all 48 molecules for compressibility and fugacity coefficient. The files provided here were used to develop the dataset in the paper, which is a comparison of thermodynamic properties of 48 molecules calculated with the Soave-Redlich-Kwong Equation of State. The calculations for methane are provided here. To use the calculation in either platform (Mathematica or MATLAB), users must specify two process temperatures and pressures, critical temperature and pressure, acentric factor, enthalpy and Gibbs energy of formation, and ideal gas heat capacity polynomials for DIPPR equation 107. A different equation my be used if programmed in by the user. When calculating compressibility, a plot is presented for the user to examine the number of roots found by the program and to select the correct root for further processing. The CHEMCAD 7.1.8 file is also provided for methane. In this file, a data map is used to export results to Microsoft Excel to obtain more significant figures in the result. The data map is found in the CHEMCAD explorer panel and is called “DataMap1.” Clicking this after running the file will open the results spreadsheet. Users should note that enthalpy units must be set to kJ. References in this document are cited in the order listed below.
Steps to reproduce
We took the following steps to validate our work. Each author independently repeated the calculations for any outlier molecules. We also developed an independent calculation in MATLAB, applying the same algorithm to all 48 molecules in our study, with the only differences being in the temperatures and pressures, critical constants, and acentric factor, formation enthalpy, and entropy, and ideal gas heat capacity constants. In this way, we minimized the chance of data entry errors. Our results are in good agreement with CHEMCAD for most of the molecules in this study, providing further evidence that the actual algorithm used is most probably correct.