Evaluation of the PR, tc-PR, CPA, PC-SAFT and IAPWS-95 models in the predicting thermodynamic properties of pure water at the supercooled, compressed liquid, saturated liquid-vapor and superheat regions

Abstract

This study provides a comprehensive understanding of the potential and limitations of the PR, tc-PR, CPA, PC-SAFT and IAPWS-95 equations of state in the prediction of thermodynamic properties of pure water. Using these equations of state (EoS), non-derivative properties, including entropy, enthalpy, internal energy, volume and derivative properties including heat capacity at constant pressure (∂H/∂T)P and constant volume (∂U/∂T)V, isobar expansivity (∂V/∂T)P, isothermal compressibility (∂V/∂P)T and speed of sound were calculated for water. The IAPWS-95 is a specialized formulation for water, which has great performance, but it shows limitation to the temperature and the pressure range where the parameters are fitted. At supercooled and compressed liquid region, the PR, tc-PR, CPA, and PC-SAFT models could not predict the properties well. At saturated liquid-vapor region, all of the equations of state lead to acceptable results for non-derivative properties; however, the CPA and PC-SAFT, as the associating type models, have limitations at the near-critical region. Accordingly, the parameters of these two models must be re-tuned to experimental data covering triple to the critical point. The PR, tc-PR, CPA and PC-SAFT models have a major shortcoming in predicting derivatives properties including (∂P/∂V)T, (∂P/∂T)V, (∂V/∂T)P and (∂V/∂P)T in all regions. Results showed that the tc-PR is a suitable EoS for predicting thermodynamic properties in saturated liquid-vapor and superheated regions. None of the models can predict the thermodynamic properties of pure water at the supercooled and compressed liquid region.