WS (formerly IUPAC-CH4)

Wagner–Setzmann reference equation

This is an empirical high-precision reference EOS that can cover the whole fluid range of a pure substance within the experimental uncertainty. Its more than 50 parameters were optimized by a complicated procedure for a couple of fluids of industrial interest. The EOS can only be used for these fluids, not for any others.

The EOS cannot be used for metastable states; the behaviour for densities between the liquid and the gas density (at subcritical temperatures) is erratic.

The EOS had originally been developed for methane, and it had been used to prepare the IUPAC “Tables of the Fluid State” for this substance. Therefore older versions of ThermoC refer to this EOS as IUPAC-CH4. But then it was found that the EOS is applicable to many other fluids.

For carbon dioxide nonanalytical terms were added to this EOS. These can cause numerical problems in the vicinity of the critical point.

The GERG model is an extension to mixtures, which, however, is usually not always of reference quality.

adjustable parameters: 0

This ThermoC version contains parameter sets for methane [1, 2], argon [3], nitrogen [4], ethane [5], propane [6], butane and methylpropane [7], (n-)hydrogen, p-hydrogen, and o-hydrogen [8], sulfur hexafluoride [9], 1,2-dichloroethane [10], and carbon dioxide [11].

  1. U. Setzmann and W. Wagner, J. Phys. Chem. Ref. Data 20 (1991) 1061–1155.
  2. W. Wagner and K. M. de Reuck, IUPAC International Tables of the Fluid State, Vol. 13: Methane, Blackwell Science, Oxford 1996.
  3. Ch. Tegeler, R. Span, and W. Wagner, J. Phys. Chem. Ref. Data 28 (1999) 779–850.
  4. R. Span, E. W. Lemmon, R. T. Jacobsen, W. Wagner, and A. Yokozeki, J. Phys. Chem. Ref. Data 29 (2000) 1361-1433.
  5. D. Bücker and W. Wagner, J. Phys. Chem. Ref. Data 35 (2006) 205–266.
  6. E. W. Lemmon, M. O. McLinden, and W. Wagner, J. Chem. Eng. Data 54 (2009) 3141–3180.
  7. D. Bücker and W. Wagner, J. Phys. Chem. Ref. Data 35 (2006) 929–1019.
  8. J. Leachman, MSc Thesis, U. of Idaho, Moscow 2007.
  9. C. Guder and W. Wagner, J. Phys. Chem. Ref. Data 38 (2009) 33–94.
  10. M. Thol, G. Rutkai, A. Köster, S. Miroshnichenko, W. Wagner, J. Vrabec, and R. Span, Mol. Phys. 115 (2016) 1166–1185.
    Note: This EOS is based to some extent on computer simulation results.
  11. R. Span and W. Wagner, J. Phys. Chem. Ref. Data 25 (1996) 1509–1596.

    12. Return to the list of equations of state!