NeqSim Input Validation Rules

Validate inputs before creating NeqSim objects or running simulations. Each rule includes the check, the error it prevents, and the corrective action.

Thermodynamic System Inputs

Temperature

Corrective action: Convert Celsius to Kelvin: T_K = 273.15 + T_C

Pressure

Corrective action: Verify units — NeqSim uses bara (absolute), not barg (gauge) or psia.

Composition

Corrective action: Normalize fractions: x_i = x_i / sum(x). Or alert user that fractions don't sum to 1.

Component Names

Valid component names must match entries in src/main/resources/data/COMP.csv. Common correct names:

Corrective action: Search COMP.csv for the correct component name.

Mixing Rule

Corrective action: Select the EOS and mixing rule from the governing named standard or validated task model before applying defaults. For ordinary SRK/PR, "classic" is a default; for CPA, numeric rule 10 is the usual setup. For ISO 18453 / GERG-water, retain rule 8 and follow the ISO 18453 / GERG-water execution rule. Set the selected rule after adding all components; never replace a specified model with a generic CPA or classic-rule recommendation.

Process Equipment Inputs

Stream

Compressor

Valve / Throttle

Heat Exchanger / Cooler / Heater

Separator

Pipeline

EOS Selection Validation

Corrective action: Match EOS to the governing standard and task model, then the fluid type. CPA is a general water/polar-system option; it does not replace the named ISO 18453 / GERG-water calculation. Resolve an unspecified model basis before claiming standard-specific results.

Order-of-Operations Validation

These operations must happen in the correct sequence:

1. Create fluid (SystemSrkEos, etc.)
2. Add ALL components
3. Set mixing rule                    ← BEFORE characterization or flash
4. Characterize plus fractions (if oil) ← AFTER mixing rule
5. Create database (if needed)
6. Run flash (TPflash, etc.)
7. Call initProperties()              ← AFTER flash, BEFORE reading properties
8. Read properties (density, viscosity, etc.)

Common order violations:

• Characterizing before setting mixing rule → ArrayIndexOutOfBoundsException
• Reading properties before initProperties() → zero values for transport properties
• Adding components after setting mixing rule → mixing rule parameters stale

Quick Validation Checklist

Use this checklist before every simulation setup:

• Temperature in Kelvin for constructors (not Celsius)
• Pressure in bara (not barg or psia)
• Mole fractions sum to ~1.0
• Component names match COMP.csv exactly
• Mixing rule set after all components added
• EOS and mixing rule match the named standard/task basis (ISO 18453: GERG-water and rule 8)
• Flash called before reading properties
• initProperties() called after flash
• Equipment connected via outlet streams (not new streams)
• ProcessSystem.run() called once after building full flowsheet