Data for: Comparison of Pure Component Thermodynamic Properties from CHEMCAD with Direct Calculation using the Soave-Redlich-Kwong Equation of State
Description
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: Gas-phase thermodynamic properties are routinely calculated with equations of state in process design software such as CHEMCAD[1], and users should be able to verify the calculations. In a previous study, we reproduced the enthalpy, entropy, compressibility factors, and fugacity coefficients obtained from CHEMCAD using the Lee-Kesler method [2,3], and later extended this study to include the Peng-Robinson equation of state {4,5]. An interesting feature of the earlier work is that compressibility and fugacity coefficients in CHEMCAD did not match up precisely with our independent calculations. We therefore extended the study to include the Soave-Redlich-Kwong (SRK) equation of state. Our results show consistency for most of the 48 molecules studied, with percent errors decreasing significantly for the SRK method to generally less than ~3x10-6% compared to about 0.3-1.8% for the Lee-Kesler and Peng-Robinson methods. Unlike the previous two studies, we now see nearly perfect agreement in the compressibility and fugacity coefficient. Furthermore, we show that compressibility and fugacity coefficient remain constant in CHEMCAD even when the equation of state is changed. For enthalpy, while the results are much closer than in the previous studies, we see deviations for methane, air, carbon monoxide, carbon dioxide, nitrogen, and oxygen. Discrepancies in entropy were also observed for bromine, carbon dioxide, chlorine, hydrogen sulfide, and nitrous oxide. 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.
Files
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.