Supporting information to accompany: Super-Ancillary Equations for Cubic Equations of State

Supplementary files to accompany the the paper "Super-Ancillary Equations for Cubic Equations of State" of Ian Bell and Ulrich Deiters in Ind. Eng. Chem. Res. Abstract: Calculation of thermodynamic phase equilibrium is error-prone and can fail both near the critical point and at very low temperatures due to the limited precision available in double precision arithmetic. Most importantly, these calculations frequently represent a computational bottleneck. In this work we extend the "super-ancillary" equation approach developed for reference multiparameter equations of state to classical cubic equations of state (van der Waals, Redlich-Kwong-Soave, Peng-Robinson). Iterative calculations in double precision are replaced by non-iterative evaluation of pre-built Chebyshev expansions constructed with extended precision arithmetic. Exact solutions for the equation of state constants are given. The Chebyshev expansions are shown to reproduce the equation of state values to within nearly double precision (aside from in the very near vicinity of the critical point) and are more than 40 times faster to evaluate than the VLE calculations from the fastest computational library. In this way we further expand the domains in which iterative calculations for pure fluid phase equilibria may be rendered obsolete. A C++ header implementing these expansions (and with no external dependencies) is provided as supplemental information. Contact Ian Bell (ian.bell@nist.gov) for more information about this paper and/or the supporting information

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[
  "Chemistry:Chemical engineering and processing",
  "Chemistry:Thermochemical properties",
  "Mathematics and Statistics:Numerical methods and software"
]