A Rational Helmholtz Fundamental Equation of State for Difluoromethane with an Intermolecular Potential Background

I. M. Astina, H. Sato

Research output: Contribution to journalArticle

9 Citations (Scopus)


A new fundamental thermodynamic equation of state for difiuoromethane was developed by considering the intermolecular potential behavior for improving the reliability in the gaseous phase. Reliable second and third virial coefficients are introduced in accordance with the principle of a unified relation of the intermolecular potential energy and the fundamental equation of state. The fundamental equation of state is able to provide reliable thermodynamic properties even at low temperatures or in the region near saturation where precise and accurate experimental data are not available. The estimated uncertainties of calculated properties from the equation of state are 0.07% in density for the liquid phase, 0.1% in pressure for the gaseous phase, 0.35% in pressure for the supercritical region, 0.07% in vapor pressure, 0.2% in saturated-liquid density, 0.7% in saturated-vapor density, 0.01% in speed of sound for the gaseous phase, 0.7% in speed of sound for the liquid phase, and 0.6% in isochoric specific heat for the liquid phase. The equation is valid for temperatures from the triple point to 450 K and pressures up to 72 MPa.

Original languageEnglish
Pages (from-to)963-990
Number of pages28
JournalInternational Journal of Thermophysics
Issue number4
Publication statusPublished - 2003 Jul



  • Difluoromethane
  • Equation of state
  • HFC refrigerant
  • HFC-32
  • Intermolecular potential
  • R32

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Mechanics of Materials
  • Computational Mechanics
  • Fluid Flow and Transfer Processes
  • Physics and Astronomy (miscellaneous)

Cite this