Cubic volume translation¶

The study separates a Péneloux-style physical-volume mapping from the parent SRK and PR78 equilibrium equations. It checks translation sign and thermodynamic identities in the notebook, then compares untranslated and translated liquid densities with methane/n-decane measurements.

Density curves¶

Translated cubic density curves

Translated-model isotherm comparison

Experimental markers include uncertainty bars where they are visible at the plot scale. Model curves connect calculations along the reported experimental state coordinates and should not be interpreted as additional measurements.

Parity and signed error¶

Volume-translation density parity and residuals

The parity and residual panels show the volumetric effect independently of the notebook's pressure, fugacity, residual-Helmholtz, and constant-translation phase-equilibrium identity checks. Agreement is specific to these model, translation, and mixture choices.

Sources: Péneloux, Rauzy, and Fréze (1982); Pedersen, Christensen, and Shaikh (2024); Whitson and Brulé, Phase Behavior, SPE Monograph 20 (2000); and Segovia et al. (2017).