Inversion Curve of Joule-Thomson Using the Peng-Robinson Cubic Equation of State
The Peng–Robinson cubic equation of state (CEOS) is used to calculate the inversion curve of the Joule–Thomson effect for any fluid. The alpha function is calculated using a generalized expression . You can vary the acentric factor to see changes in the inversion curve.
 D. Y. Peng and D. B. Robinson. "A New Two-Constant Equation of State," Industrial and Engineering Chemistry Fundamentals, 15(1), 1976 pp. 59–64.
 K. A. M. Gasem, W. Gao, Z. Pan, and R. L. Robinson, "A Modified Temperature Dependence for the Peng–Robinson Equation of State," Fluid Phase Equilibria, 181(1–2), 2001 pp. 113–125.