CONNECT MEASUREMENTS TO YOUR MODEL
Parameter fitting
Fit binary NRTL or UNIQUAC parameters to one or several kinds of experimental data.
Experimental observations
Paste a webpage, book or paper table, with or without headings, or enter an observation below. Imported data is added to the existing observations. Ambiguous columns and units can be resolved in a popup.
Fill the scales you want to set. They apply to new observations; Apply σ also updates the selected existing set. Empty fields preserve existing row settings and use the model defaults for new rows. These are residual scales, not automatically converted temperature/composition measurement errors.
For several measurement columns sharing one composition axis, choose Repeated series / multicolumn in the interpretation popup. Assign shared columns and each series’ measurements, then supply its temperature or pressure and units. Repeated columns are expanded only after you explicitly select that mode.
Every row needs kind and T_K or T_C. VLE needs P_bar (or P_kPa/P_atm) and x1; y1 is optional. LLE needs x1_alpha and/or x1_beta; a missing endpoint is inferred. Alpha is the lower component-1 mole fraction and beta the higher. HE needs x1 and HE_J_mol or HE_kJ_mol. GAMMA_INF needs gamma1_inf and/or gamma2_inf. AZEOTROPE needs x1 and pressure; vapor and liquid compositions coincide. UCST/LCST need temperature; x1 is optional and otherwise fitted.
weight upweights a row. pin: true requires every scaled residual for that row to lie within pin_tolerance (default 10⁻⁵), including phase-stability conditions. Incompatible pins fail explicitly. Pins constrain model predictions at the supplied coordinates; they do not fix model coefficients.
sigma overrides a residual scale: a number for all residuals in that row, or an object with keys shown under Advanced controls. HE scales are J/mol; activity and fugacity scales are logarithmic. Critical curvature and third derivative scales refer to dimensionless g/RT. Critical points also require positive fourth derivative and the correct UCST/LCST temperature direction. source records provenance and group controls grouped validation.
Multi-term temperature laws generally need multiple measurement temperatures or additional caloric data. The fit reports rank deficiency when coefficients are not uniquely determined. For joint HE fitting, choose a temperature-dependent law. Examples illustrate the format and are not experimental reference data.
VLLE / heteroazeotrope points need temperature and pressure, with optional shared vapor composition. Supply both liquid endpoints or leave both blank to infer the coexisting phases. They have a separate objective weight.
Validation-only observations are never fitted or pinned. They appear separately in plots and physical error metrics, and are excluded from training and cross-validation folds.
Missing values: leave a cell blank or use ?, None, null, NA/N/A, NaN, a dash, an ellipsis, or “missing”, “unknown”, “not measured”, or “not reported”. Required fitting conditions must still be supplied; optional measurements may be omitted.
Fit assessment
Physical errors
Predicted and observed objectives
Diagnostic data · scaled residuals and objective scores
Cross-validation results
Coefficients and solver diagnostics
Export and apply
For UNIQUAC, the R/Q component definitions are included in the complete PFD export. The selected vapor method appears there too.
Applying changes the selected scope's method and this pair’s coefficients. Entered Psat, pure-fluid properties, R/Q and VDM definitions apply to the component globally and therefore also affect other scopes using it.
Submit for general inclusion
Submit the observations, model settings, coefficients and diagnostics with their source for review. Submission does not automatically modify PFDSim’s reference database.