The method for constructing the fundamental equation of state for SF6

Abstract

Abstract The paper investigates issues related to construction of the equation of state which takes into account the peculiarities of substance behavior in the critical region and which is associated with the scalihg theory of critical phenomena. Construction method of a unified fundamental equation of state (UFEoS) for SFß that satisfies the power laws of scaling theory (ST) and the requirements imposed on the fundamental equations of state of the virial form (FEoS) is considered. UFEoS is based on a new representation of the scaling hypothesis in variables density – temperature and Benedek hypothesis. The authors have developed FEoS for SF6 in the range of state parameters: in density up to 2000 kg/m3, in temperature from 223.555 to 650 K. The authors have performed comparison with the certain fundamental equations of state for SF6: Scalabrin et al (2007 J. Phys. Chem. Ref. Data 36 617), Guder et al (2009 J. Phys. Chem. Ref. Data 38 33); Bezverkhii (2017 High Temp. 55 702). It is shown that in accordance with the requirements of ST, in contrast to the certain FEoS, the proposed equation of state transmits SF6 behavior into the vicinity of the critical point and in this region of state parameters significantly exceeds them in accuracy.