Equation of state for square-well fluids: Development of a coordination number model

Kh Nasrifar*, F. Jalali

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)


A new expression for the coordination number of square-well fluids is developed. This expression meets the low density and close-packed density boundary conditions. On the basis of this model, a new equation of state (EOS) is introduced. This EOS needs the square-well potential function parameters - that is, R, σ, and ε/k - as input parameters. When these parameters are used as adjustable parameters, the EOS accurately describes the thermodynamic properties of normal fluids. The average absolute error for calculating the saturated vapor pressure, liquid density, vapor volume and enthalpy of vaporization of pure fluids was found to be 6.85, 3.95, 8.68, and 4.75%, respectively. Also, for a wide range of temperature and pressure, the compressed liquid density of methane and 1,1-difluoroethane were predicted accurately. The average absolute error was found to be 4.13 and 1.43% for methane and 1,1-difuoroethane, respectively.

Original languageEnglish
Pages (from-to)167-181
Number of pages15
JournalFluid Phase Equilibria
Issue number1-2
Publication statusPublished - May 30 2003
Externally publishedYes


  • Coordination number
  • Equation of state
  • Pure fluid
  • Square-well fluid

ASJC Scopus subject areas

  • General Chemical Engineering
  • General Physics and Astronomy
  • Physical and Theoretical Chemistry

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