Peng-Robinson Fluid Phase-Envelope Continuation Calculator

Trace both C1-C6 bubble and dew branches through the critical neighborhood, correcting native continuation seeds and auditing every returned equilibrium state.

Results

Calculate to view linked results. Default values are examples, not recommended operating inputs.

Learn, compare and practice

Worked explanations, controlled studies and printable exercises connected to this calculation.

Bubble dew and critical regions on a phase envelope

Calculation sequence

Enter a normalized two-or-more-component C1-C6 feed. The engine uses unmodified, version-pinned CoolProp 8 PR continuation rather than solving independent saturation temperatures on a rectangular grid. Both branches must reach below the declared 0.1 MPa(a) plotting floor and exchange density order once in the critical neighborhood.
Reconstruct the incipient composition at every returned node, then correct the complete equilibrium equations. Native near-critical interpolation is a starting point, never an exemption from fugacity or EOS checks. Reject extra branch switches, collapsed roots, unsupported domains or a correction that leaves its continuation neighborhood. No failed node is silently omitted or replaced by a straight line.
Read the bubble and dew curves as fluid-only EOS predictions. The critical point lies in the displayed crossing-temperature bracket; it is not the maximum pressure or temperature. Reported trace maxima depend on native point spacing and are explicitly not converged cricondentherm or cricondenbar solves. Compare measured saturation and critical data before adopting an EOS model.
Calculations remain local in a dedicated WebAssembly worker. The existing self-hosted scientific engine is about 33 MB raw on first use; the envelope additionally loads the pinned CoolProp engine and eccentric flow loads a 178 KB FEM package. Nothing is downloaded until calculation. No composition, heat history or measurements are sent to a calculation server. Save retains canonical input values; file backup can be shared with colleagues, while CSV/PDF retain samples, assumptions and sources. Browser storage alone can be lost.

Worked check

The default 0.50/0.15/0.15/0.10/0.05/0.05 C1-C6 feed gives a maximum traced temperature about 379.292804 K and maximum traced pressure about 11.565069 MPa(a). The native and independent critical-point calculations are checked separately; exact point count and crossing bracket can differ between native and WASM floating-point continuation paths.

Synthetic examples for reproducibility, not measured field results.

Assumptions and limitations

C1-C6 only, all kij=0, classical PR without volume translation. This is not a tuned composition/interaction regression, water association model or arbitrary multi-liquid phase topology.
The plotted curve is bounded below by 0.1 MPa(a), with accepted fluid states within 80-500 K and below 50 MPa. Fluid continuation can be metastable with respect to real solids at low temperatures; no hydrate/wax/ice boundary is overlaid.
Near-critical crossing is bracketed, not an exact mixture-critical-point calculation. Discrete maxima are not certified retrograde extrema. Some native feeds trace incorrectly and are rejected in full rather than presented as valid envelopes.

Implemented equations

Corrected continuation equilibrium

\begin{aligned}x_i\phi_i^L&=y_i\phi_i^V\\p_{\rm PR}(T,\rho_L,x)&=p\\p_{\rm PR}(T,\rho_V,y)&=p\end{aligned}

Sources and maintenance

Published by PetroCalcHub Team. Implementation and source checks: 2026-10-22. This does not claim independent expert review.

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