Consistent Twu Parameters for More than 2500 Pure Fluids from Critically Evaluated Experimental Data

The construction of the standard cubic equations of state, such as Peng–Robinson or Soave–Redlich–Kwong, does not automatically yield physically reasonable values when the equation of state is extrapolated beyond the range where experimental data are available. A multiproperty fitting exercise was carried out in which we obtained a consistent set of Twu α function parameters for 2570 pure fluids based on the experimental data contained in the ThermoDataEngine (TDE) database developed at NIST. We have applied the consistency checks of Le Guennec et al. to the Twu α function of the Peng–Robinson equation of state. The experimental data stored in the TDE passed through a critical evaluation, and we used only the data that were determined to be thermodynamically reliable. Over all the considered fluids, the mean average percentage error is approximately 7% for vapor pressure, 1% for latent heat of vaporization, and 1% for saturation specific heat.