One mixture.
Two phases. One criterion.

A small numerical residual verifies the equations solved. It does not establish experimental accuracy or validate a model outside its assumptions.

Ideal vapor, pure-liquid reference states, and negligible Poynting correction give:

Bubble pressure is evaluated directly. Dew pressure is found by bracketing the liquid composition whose equilibrium vapor matches the specified y₁.

For binary TP flash, first bracket all roots of P_bubble(x₁) − P = 0. Activity coefficients are recalculated at every trial x₁. Retain tie lines that contain the feed; then solve Rachford–Rice with the converged Kᵢ = γᵢPᵢˢᵃᵗ/P.

Composition-root relative-pressure tolerance: 10⁻¹³. Rachford–Rice tolerance: 10⁻¹⁴. Independent component balance and equilibrium checks must each be ≤10⁻⁸. Near an azeotrope, β is poorly conditioned; at exact azeotropic or pure-component saturation, T and P do not determine β.

Current calculation

Temperature at the phase boundary

At the selected pressure, using x₁ = z₁ for bubble T and y₁ = z₁ for dew T. These are separate boundary calculations.

Every fifth point of the selected model is shown. Download CSV for the complete curve. Missing T–x–y values mean the correlation range does not bracket a root.

Antoine form: log₁₀(P/bar) = a − b/(T/K + c). Synthetic form: ln(P/P_ref) = −ΔH_vap/R · (1/T − 1/T_ref).

Pressure inputs are restricted to 1–200 kPa as a teaching scope, not an accuracy guarantee. Temperature limits are the intersection of both component correlation ranges. Curves are clipped to this domain.

The engine checks that h(x₁) = x₁(1−x₁) d²(g^L/RT)/dx₁² stays positive across the entire composition interval. For the two-parameter model, the minimum of this cubic is evaluated at both endpoints and every internal stationary point. Non-convex or near-critical parameter sets are rejected because this VLE-only calculation does not solve LLE. Equal A₁₂ = A₂₁ = A recovers the one-parameter model. The engine searches its binary vapor–liquid tie lines; it does not implement a general multicomponent TPD stability test, VLLE, or energy balances.

Model equations and parameter convention: Harvey Mudd College, Excess Gibbs Energy model table. Parameters are held constant with temperature in this teaching model.

Export includes inputs, diagnostics, property records and sampled curves. Inspect the engine · Property records · Regenerate a publication figure (Python)