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.