A New Approach to PVT Properties and Compressibility Charts Using the SRK Equation of State

The Soave-Redlich-Kwong (SRK) equation is a cubic equation of state used to calculate PVT properties of a substance given its critical temperature, critical pressure, and acentric factor.  A new dimensionless version of the SRK equation was developed.  The dimensionless variables used in this approach were Ψ, an independent variable incorporating both pressure and temperature, η, an independent variable incorporating both temperature and acentric factor, and ρ_r’, a dependent variable representing molar density or volume.  The standard SRK equation containing three substance-specific independent variables was represented exactly by the new version containing only two substance-specific independent variables.  This new approach was then used to construct compressibility charts analogous to existing charts, but with the Ψ variable replacing reduced pressure and the η variable replacing reduced temperature. These new charts include the effect of acentric factor ω on compressibility, unlike existing compressibility charts.  Constant ρ_r’ lines on the new charts replaced the constant volume curves on existing charts, and these lines were shown to project from the origin of the graph. Work continues on applying the new approach to other problems in equations of state, vapor-liquid equilibrium, and physical property prediction.