neqsim-api-patterns

name	neqsim-api-patterns
description	NeqSim API patterns and code recipes. USE WHEN: writing Java or Python code that uses NeqSim for thermodynamic calculations, process simulation, or property retrieval. Covers EOS selection, fluid creation, flash calculations, property access, equipment patterns, and unit conventions.
last_verified	2026-07-10

NeqSim API Patterns

Copy-paste reference for common NeqSim operations. All Java code must be Java 8 compatible.

EOS Selection Guide

Fluid Type	Java Class	Mixing Rule
Dry/lean gas, simple HC	SystemSrkEos	"classic"
General hydrocarbons, oil	SystemPrEos	"classic"
Matched to commercial simulator PR-LK	SystemPrLeeKeslerEos	"classic"
Water, MEG, methanol, polar	SystemSrkCPAstatoil	10 (numeric)
Custody transfer, fiscal metering	SystemGERG2008Eos	(none needed)
Electrolyte systems, hydrate with salt brine	SystemElectrolyteCPAstatoil	10
Volume-corrected SRK	SystemSrkEosvolcor	"classic"

PR-LK vs PR78: SystemPrLeeKeslerEos uses PR76 alpha for ALL ω: m = 0.37464 + 1.54226ω − 0.26992ω². Standard SystemPrEos1978 uses a modified cubic for ω > 0.49. Use PR-LK when matching commercial simulator models that use this EOS label.

Fluid Creation (Required Sequence)

// 1. Create: temperature in KELVIN, pressure in bara
SystemInterface fluid = new SystemSrkEos(273.15 + 25.0, 60.0);

// 2. Add components (name, mole fraction)
fluid.addComponent("methane", 0.85);
fluid.addComponent("ethane", 0.10);
fluid.addComponent("propane", 0.05);

// 3. MANDATORY: set mixing rule — NEVER skip
fluid.setMixingRule("classic");

// 4. Optional: multi-phase check for water/heavy systems
fluid.setMultiPhaseCheck(true);

Oil Characterization (C7+ Fractions)

fluid.addTBPfraction("C7", 0.05, 92.0 / 1000, 0.727);   // name, moleFrac, MW_kg/mol, density
fluid.addTBPfraction("C8", 0.04, 104.0 / 1000, 0.749);
fluid.addPlusFraction("C20+", 0.02, 350.0 / 1000, 0.88);
fluid.getCharacterization().getLumpingModel().setNumberOfLumpedComponents(6);
fluid.getCharacterization().characterisePlusFraction();

Loading Fluids from E300 Files

NeqSim can read Eclipse E300-format fluid files with full component properties and binary interaction parameters:

// Load fluid from E300 file (returns SystemInterface with PR-EOS)
SystemInterface fluid = EclipseFluidReadWrite.read("path/to/fluid.e300");
// Returns a PR-EOS fluid with all components, properties, and BIPs set

Required E300 sections: CNAMES, TCRIT, PCRIT, ACF, MW, TBOIL, VCRIT, PARACHOR, SSHIFT, BIC, ZI.

Optional E300 sections (NeqSim parses and applies these):

• OMEGAA / OMEGAB — per-component OmegaA/B overrides (applied after init(0))
• BICS — surface-condition BICs (parsed, same lower-triangular format as BIC)
• SSHIFTS — surface-condition volume shift
• PEDERSEN — activates Pedersen viscosity model

EOS keyword determines fluid class:

• EOS\nSRK / → SystemSrkEos
• EOS\nPR /\nPRCORR → SystemPrEos1978
• EOS\nPR /\nPRLKCORR → SystemPrLeeKeslerEos ← use for PR-LK matching
• EOS\nPR / → SystemPrEos

CRITICAL: The BIC section must ALWAYS be present. If omitted, NeqSim defaults to zero BIPs (no crash, but results may differ significantly from the source simulator). The PARACHOR section is also required — estimate unknown values with 4.0 * MW^0.77.

Component name mapping: C1→methane, C2→ethane, C3→propane, iC4→i-butane, C4→n-butane, iC5→i-pentane, C5→n-pentane, C6→n-hexane, N2→nitrogen, CO2→CO2, H2O→water. All other names are treated as TBP pseudo-fractions via addTBPfraction() — including aromatics (Benzene, Toluene, etc.).

# Python usage — auto-detects EOS from file
from neqsim import jneqsim
EclipseFluidReadWrite = jneqsim.thermo.util.readwrite.EclipseFluidReadWrite
fluid = EclipseFluidReadWrite.read("path/to/fluid.e300")

# Force a specific EOS regardless of what's in the file
SystemPrLeeKeslerEos = jneqsim.thermo.system.SystemPrLeeKeslerEos
target_fluid = SystemPrLeeKeslerEos(288.15, 1.01325)
fluid = EclipseFluidReadWrite.read("path/to/fluid.e300", target_fluid)

JSON process builder also supports PR-LK via "model": "PR_LK":

{ "fluid": { "model": "PR_LK", "temperature": 288.15, "pressure": 50.0, ... } }

Flash Calculations and Property Retrieval

ThermodynamicOperations ops = new ThermodynamicOperations(fluid);
ops.TPflash();

// CRITICAL: call initProperties() AFTER flash, BEFORE reading properties
// init(3) alone does NOT initialize transport properties — they return ZERO
fluid.initProperties();

// Bulk properties
double density = fluid.getDensity("kg/m3");
double molarMass = fluid.getMolarMass("kg/mol");
double Z = fluid.getZ();

// Phase properties
double gasDensity = fluid.getPhase("gas").getDensity("kg/m3");
double gasViscosity = fluid.getPhase("gas").getViscosity("kg/msec");
double gasThermalCond = fluid.getPhase("gas").getThermalConductivity("W/mK");
double gasCp = fluid.getPhase("gas").getCp("J/kgK");

// Phase checks
int numPhases = fluid.getNumberOfPhases();
boolean hasGas = fluid.hasPhaseType("gas");

Other Flash Types

ops.PHflash(enthalpy);                  // Pressure-Enthalpy
ops.PSflash(entropy);                   // Pressure-Entropy
ops.dewPointTemperatureFlash();          // Dew point temperature
ops.bubblePointPressureFlash();          // Bubble point pressure
ops.hydrateFormationTemperature();       // Hydrate T at given P
ops.calcPTphaseEnvelope();              // Phase envelope

Unit Conventions

Quantity	Constructor default	Setter pattern
Temperature	Kelvin	setTemperature(25.0, "C")
Pressure	bara	setPressure(50.0, "bara")
Flow rate	—	setFlowRate(50000.0, "kg/hr")
Getting temp	Returns Kelvin	getTemperature() - 273.15 for °C

Process Equipment Patterns

Stream

Stream feed = new Stream("feed", fluid);
feed.setFlowRate(100.0, "kg/hr");
feed.setPressure(50.0, "bara");
feed.setTemperature(30.0, "C");

Separator

Separator sep = new Separator("HP Sep", feedStream);
Stream gasOut = sep.getGasOutStream();
Stream liqOut = sep.getLiquidOutStream();

Separator class ↔ orientation (affects gas-capacity results):

Class	Default orientation	Use for
Separator, ThreePhaseSeparator	horizontal	horizontal separators (VA-tag)
GasScrubber, GasScrubberSimple, NeqGasScrubber (2-phase)	vertical	vertical scrubbers (VG-tag)
ThreePhaseGasScrubber (3-phase)	vertical	vertical 3-phase scrubbers

A horizontal vessel derates the gas area by the design liquid level (default 80% → gas area (1−0.8)=0.2×), so using a horizontal Separator/ThreePhaseSeparator for a physically vertical scrubber over-reads getGasLoadFactor() / getGasSuperficialVelocity() by ~5×. Prefer the *GasScrubber classes for vertical scrubbers, or override with sep.setOrientation("vertical"). setInternalDiameter() propagates correctly through run() — the trap is orientation, not diameter.

Separator Mechanical Design (Physical Configuration)

Physical dimensions, internals, and design parameters are configured through SeparatorMechanicalDesign — NOT directly on Separator. The Separator class handles process simulation (flash, entrainment); SeparatorMechanicalDesign owns the physical vessel design.

// After process.run():
sep.initMechanicalDesign();
SeparatorMechanicalDesign design =
    (SeparatorMechanicalDesign) sep.getMechanicalDesign();

// Design envelope
design.setMaxOperationPressure(85.0);           // bara
design.setMaxOperationTemperature(273.15 + 80); // K

// Vessel sizing parameters (configured via MechanicalDesign)
design.setGasLoadFactor(0.107);       // K-factor [m/s]
design.setRetentionTime(120.0);       // Liquid retention [s]
design.setFg(0.5);                    // Gas area fraction

// Nozzle diameters (set via MechanicalDesign, NOT on Separator)
design.setInletNozzleID(0.254);       // 10-inch inlet nozzle [m]
design.setGasOutletNozzleID(0.20);    // Gas outlet [m]
design.setOilOutletNozzleID(0.15);    // Oil outlet [m]

// Demister/mist eliminator parameters
design.setDemisterType("wire_mesh");  // "wire_mesh", "vane_pack", "cyclone"
design.setDemisterPressureDrop(1.5);  // [mbar]
design.setDemisterThickness(150.0);   // [mm]
design.setFoamAllowanceFactor(1.0);   // 1.0 = no foam

// Bridge methods — entrainment internals (delegate to Separator)
design.setInletPipeDiameter(0.254);   // Inlet pipe ID for DSD generation [m]
design.setInletDeviceType(InletDeviceModel.InletDeviceType.INLET_VANE);
design.setGasLiquidSurfaceTension(0.020); // Interfacial tension [N/m]
design.addSeparatorSection("Demister", "meshpad");

// Bridge methods — dynamic internals (delegate to Separator)
design.setWeirHeightAbsolute(0.30);   // Weir height [m] (syncs weirFraction)
design.setWeirLength(1.5);            // Weir crest length [m]
design.setBootVolume(2.0);            // Boot/sump volume [m3]
design.setMistEliminatorDpCoeff(150.0);  // Euler number for dP calc
design.setMistEliminatorThickness(0.15); // Demister pad thickness [m]

// Run design calculation
design.readDesignSpecifications();
design.calcDesign();
String report = design.toJson();

// Results: design.getInnerDiameter(), design.getTantanLength(),
//          design.getWallThickness(), design.getInletNozzleID(), etc.

Separator Entrainment (Carry-Over)

Imperfect separation is modelled with setEntrainment() on the Separator / ThreePhaseSeparator itself (not the mechanical design). It transfers a fraction of one phase into another outlet stream.

// setEntrainment(double val, String specType, String specifiedStream,
//                String phaseFrom, String phaseTo)
//   specType        : "mole" | "mass" | "volume"
//   specifiedStream : "feed" (fraction of feed) | "product" (fraction of receiving outlet)
//   phaseFrom/To    : "gas" | "oil" | "aqueous"  (base Separator also accepts "liquid")

ThreePhaseSeparator sep = new ThreePhaseSeparator("1st Stage", feed);

// Liquid carry-over into gas (feed basis)
sep.setEntrainment(0.001, "mole", "feed", "oil", "gas");      // oil-in-gas
sep.setEntrainment(0.001, "mole", "feed", "aqueous", "gas");  // water-in-gas

// Cross-contamination expressed on the receiving product stream
sep.setEntrainment(0.005, "mass",   "product", "aqueous", "oil"); // 0.5 mass% BS&W in oil
sep.setEntrainment(500e-6, "mass",   "product", "oil", "aqueous"); // 500 ppm oil-in-water
sep.run();

• Base Separator supports 3 paths: oil→gas, aqueous→gas, gas→liquid.
• ThreePhaseSeparator supports all 6 paths: oil→gas, aqueous→gas, gas→oil, gas→aqueous, oil→aqueous, aqueous→oil.
• With specifiedStream="product", val is clamped: ≤0 transfers nothing, ≥1 transfers the entire source phase.

Typical screening values (indicative only — always defer to the project separation spec / datasheet; for rigorous physics use the enhanced entrainment model and SeparatorMechanicalDesign):

Carry-over path	Typical range	Basis	Notes
Liquid-in-gas (oil or water → gas)	0.01 – 0.5 %	mole/mass, feed	Well-designed mist extractor; tighter (<0.01%) with high-efficiency internals
Gas carry-under (gas → liquid)	0.1 – 2 %	mole, feed	Higher with foaming / short retention
Water-in-oil (BS&W, aqueous → oil)	0.5 – 5 vol%	volume, product	Export crude spec often ≤ 0.5 vol%; inter-stage higher
Oil-in-water (oil → aqueous)	100 – 1000 ppm	mass, product	Produced-water inlet; overboard discharge typically ≤ 30 ppm (OSPAR)

Separation Efficiency Report (K-Factor Operating Windows)

SeparatorMechanicalDesign.calculateSeparationEfficiency() returns a SeparatorEfficiencyReport that combines the physics-based entrainment / carry-under fractions with a per-internal Souders-Brown K-factor operating window check (from the internals database MinKFactor/MaxKFactor). It answers "is this mist mat / vane pack / cyclone inside its good performance band, below turndown, or into flooding?" and works for two-phase AND three-phase separators and gas scrubbers (GasScrubberMechanicalDesign inherits it).

It is read-only — it does not change what run() does. Whether the physics entrainment model is applied at run time is a separate opt-in toggle (setEfficiencyModelEnabled). Default behaviour (no entrainment, or manual setEntrainment(...)) is unchanged.

sep.run();                                    // flash
SeparatorMechanicalDesign design =
    (SeparatorMechanicalDesign) sep.getMechanicalDesign();
design.calcDesign();
design.setDesign();                           // push sized diameter to the separator

// Optional: pick a specific database sub-type for the mist mat
design.setDemisterType("wire_mesh");          // "wire_mesh" | "vane_pack" | "cyclone"
design.setDemisterSubType("High Efficiency"); // sub-type from SeparatorInternals.csv

// Read-only assessment (2-phase or 3-phase, auto-detected)
SeparatorEfficiencyReport report = design.calculateSeparationEfficiency();
double opK      = report.getOperatingKFactor();           // m/s
double effGL    = report.getOverallGasLiquidEfficiency(); // 0-1
String verdict  = report.getVerdict();  // GOOD_PERFORMANCE | BELOW_TURNDOWN | FLOODING_RISK | MARGINAL_EFFICIENCY
for (InternalOperatingWindow w : report.getWindows()) {
  // w.getStatus(): BELOW_MIN_TURNDOWN | IN_RANGE | ABOVE_MAX_FLOODING
  // w.getMinKFactor(), w.getMaxKFactor(), w.getUtilization(), w.getTurndownRatio()
}
String json = report.toJson();  // full report incl. per-internal windows

// Apply the physics entrainment/carry-under model during run() (opt-in):
design.setEfficiencyModelEnabled(true);   // delegates to setDetailedEntrainmentCalculation(true)
sep.run();                                // gas/liquid outlets now reflect computed carry-over
design.setEfficiencyModelEnabled(false);  // back to no-entrainment / manual setEntrainment

K-factor window meaning (limits from SeparatorInternals.csv): K < Kmin → below turndown (poor coalescence, droplets slip through); Kmin ≤ K ≤ Kmax → good performance band; K > Kmax → flooding / re-entrainment.

Compressor

Compressor comp = new Compressor("Comp", gasStream);
comp.setOutletPressure(120.0);
// comp.setIsentropicEfficiency(0.75);
Stream out = comp.getOutletStream();
// After run: comp.getPower("kW")

Compressor chart library (multiple named/selectable charts)

A Compressor can hold several performance maps at once via a CompressorChartLibrary and switch the active chart by name — the professional way to keep vendor-expected, as-tested and field-fitted curves for the same machine side by side (revamp studies, digital twins, design-vs-tested checks). See the Compressor Chart Library doc.

comp.addChart("BCL405B-design", expectedChart);
comp.addChart("BCL405B-tested", asTestedChart,
    new CompressorChartMetadata("BCL 405/B", "gas export", "27-KA01",
        "8300199-CA-001", CompressorChartMetadata.CurveType.AS_TESTED));
comp.selectChart("BCL405B-tested");   // sets + enables the chart, turns on polytropic calc
comp.run();

List<String> charts = comp.getAvailableCharts();      // ["BCL405B-design", "BCL405B-tested"]
String active = comp.getSelectedChartName();          // "BCL405B-tested"

// Persist / reload a shared vendor-curve database (all curves + metadata):
comp.getChartLibrary().saveToFile("BCL405B_charts.json");
comp.setChartLibrary(CompressorChartLibrary.loadFromFile("BCL405B_charts.json"));

Compressor deposit / fouling degradation and washing

Model deposit (fouling) mass from process thermodynamics, its effect on performance, where it lands per impeller, the degraded chart after N hours, and online washing. Package neqsim.process.equipment.compressor. See the Compressor Deposit and Performance Degradation doc.

// 1) Deposit mass -> performance effect (combine several mechanisms)
CompressorDeposit dep = CompressorDeposit.fromCompressor(comp); // sizes foulable geometry
dep.addDeposit(DepositMechanism.SULFUR_S8, 1.2);   // kg (S8 study)
dep.addDeposit(DepositMechanism.SALT_NACL, 0.4);   // kg (salt study)
comp.setDepositModel(dep);                          // run() now degrades efficiency/power
comp.run();
double effLoss = 1.0 - dep.getEfficiencyMultiplier();

// 2) Deposit mass FROM the process (precipitation bridge)
SolidFlashDepositSource s8 =
    new SolidFlashDepositSource(feed, "S8", DepositMechanism.SULFUR_S8, 0.3); // TPSolidflash
EntrainedSaltDepositSource salt =
    new EntrainedSaltDepositSource(10.0, 0.05);     // 10 kg/hr entrained water, 5 wt% salt
dep.accumulate(s8, 500.0);                          // deposit after 500 operating hours
dep.accumulate(salt, 500.0);

// 3) Degraded performance chart after N hours (chart-based machines)
CompressorChart chart500 = comp.buildDegradedChart();

// 4) Where deposits form (per impeller). Rigorous = real per-step flashed states:
comp.setPolytropicMethod("detailed");
comp.getPropertyProfile().setActive(true);
comp.run();
List<CompressorDepositProfile.StageDeposit> profile =
    CompressorDepositProfile.computeFromPropertyProfile(comp, 5, "S8");
int worst = CompressorDepositProfile.worstStage(profile); // 1 = cold first impeller

// 5) Online washing: recommend fluid, plan rate, simulate removal
WashFluid fluid = CompressorDepositWash.recommend(dep);   // salt->WATER, S8->XYLENE
CompressorDepositWash washer = new CompressorDepositWash();
washer.setContactEfficiency(0.7);
double rateKgHr = washer.requiredFluidRateKgHr(dep, fluid, 2.0, 3.0); // remove 2 kg in 3 h
CompressorDepositWash.WashResult r = comp.washOnline(fluid, rateKgHr, 3.0);
comp.run();                                               // performance recovers

Wash-fluid → deposit matching (screening solubilities): water dissolves salt/scale; xylene/toluene dissolve S8 and wax; condensate dissolves wax; methanol moderate salt. recommend() returns the fluid that removes the most mass — for mixed salt+S8 fouling, wash in sequence (water, then xylene).

Cooler / Heater

Cooler cooler = new Cooler("Cooler", hotStream);
cooler.setOutTemperature(273.15 + 30.0);
Stream out = cooler.getOutletStream();
// After run: cooler.getDuty() — Watts

HeatExchanger (Two-Sided)

HeatExchanger has two feed/outlet sides indexed 0 and 1. Use setFeedStream(int, StreamInterface) to connect both sides and getOutStream(int) to retrieve the outlet for each side.

IMPORTANT: Do NOT use getOutletStream() when you need a specific side — it only returns side 0. Always use getOutStream(int).

HeatExchanger hx = new HeatExchanger("E-100");
hx.setFeedStream(0, shellSideFeed);   // side 0 = shell
hx.setFeedStream(1, tubeSideFeed);    // side 1 = tube
// Optional: hx.setUAvalue(35000.0);  // W/K

// After run: retrieve each side's outlet
Stream shellOut = (Stream) hx.getOutStream(0);
Stream tubeOut  = (Stream) hx.getOutStream(1);
double duty = hx.getDuty();  // Watts

# Python
hx = HeatExchanger("E-100")
hx.setFeedStream(0, shell_feed)
hx.setFeedStream(1, tube_feed)
# Downstream connections:
cooler = Cooler("C-100", hx.getOutStream(int(0)))   # shell side out
valve  = ThrottlingValve("VLV-100", hx.getOutStream(int(1)))  # tube side out

Valve (JT / Isenthalpic Expansion)

ThrottlingValve valve = new ThrottlingValve("JT Valve", stream);
valve.setOutletPressure(20.0);
Stream out = valve.getOutletStream();

CRITICAL: Always use ThrottlingValve inside a ProcessSystem for Joule-Thomson cooling calculations. Manual PHflash() on a cloned fluid gives wrong JT temperatures (tested: 14.9°C error vs 1.7°C with ThrottlingValve). The valve handles the isenthalpic enthalpy bookkeeping internally.

# Python — Correct JT expansion pattern
proc = ProcessSystem()
feed = Stream('SG', fluid.clone())
feed.setFlowRate(flow, 'kg/hr')
feed.setTemperature(T_in, 'C')
feed.setPressure(P_in, 'bara')
proc.add(feed)
valve = ThrottlingValve('JT', feed)
valve.setOutletPressure(P_out)
proc.add(valve)
proc.run()
T_jt = float(valve.getOutletStream().getTemperature('C'))

Mixer

Mixer mixer = new Mixer("Mix");
mixer.addStream(stream1);
mixer.addStream(stream2);
Stream out = mixer.getOutletStream();

ComponentSplitter (TEG / Glycol Contactor — Water Removal)

Used to model TEG dehydration contactors as simple water-removal units. Splits a stream per-component: splitFactor[k] = 1.0 keeps the component in stream 0 (dry gas), 0.0 removes it to stream 1 (water).

TEG dehydration pattern: water is always the last component added, so use [1.0] * (N-1) + [0.0] to remove only water.

// Java
ComponentSplitter dehydrator = new ComponentSplitter("TEG contactor", wetGasStream);
int nComp = wetGasStream.getFluid().getNumberOfComponents();
double[] sf = new double[nComp];
Arrays.fill(sf, 1.0);
sf[nComp - 1] = 0.0;  // last component = water
dehydrator.setSplitFactors(sf);
// After run:
Stream dryGas = dehydrator.getSplitStream(0);   // all components except water
Stream water  = dehydrator.getSplitStream(1);   // removed water

# Python
water_dehydration = neqsim.process.equipment.splitter.ComponentSplitter(
    "dehyd", wet_gas_stream)
complen = wet_gas_stream.getFluid().getNumberOfComponents()
water_dehydration.setSplitFactors([1.0] * (complen - 1) + [0.0])
water_dehydration.run()
dry_gas = water_dehydration.getSplitStream(0)

When to use: Any absorber with a glycol-related name ("glyc", "teg", "dehydrat") should be modeled as a ComponentSplitter rather than a DistillationColumn. This avoids solver convergence issues and is the standard pattern for production platform models.

Pump

Pump pump = new Pump("P-100", liquidStream);
pump.setOutletPressure(20.0);           // bara
pump.setIsentropicEfficiency(0.75);     // 0-1
Stream out = pump.getOutletStream();
// After run: pump.getPower("kW")

Three operating modes:

1. Isentropic (default): PS flash → isentropic enthalpy → divide by efficiency → PH flash
2. Fixed outlet temperature: pump.setOutletTemperature(40.0, "C") → back-calculates power
3. Pump chart: pump.getPumpChart() → head, efficiency, NPSH curves

Pipeline

AdiabaticPipe pipe = new AdiabaticPipe("Pipeline", stream);
pipe.setLength(50000.0);   // meters
pipe.setDiameter(0.508);   // meters (20 inch)
Stream out = pipe.getOutletStream();

Route-Level Piping From STID/E3D Line Lists

For route pressure-drop tasks based on STID P&IDs, E3D exports, stress isometrics, or line-list tables, prefer PipingRouteBuilder over manually creating many pipe units. It creates a serial ProcessSystem with one PipeBeggsAndBrills unit per segment and stores explicit material connection metadata.

PipingRouteBuilder route = new PipingRouteBuilder()
    .setDefaultPipeWallRoughness(45.0, "micrometer")
    .setMinorLossFrictionFactor(0.02)
    .addSegment("S1", "Manifold", "Valve Station", 100.0, "m", 0.2, "m")
    .setSegmentWallThickness("S1", 8.0, "mm")
    .addMinorLoss("S1", "manual valve", 1.0)
    .addSegment("S2", "Valve Station", "Compressor Scrubber", 25.0, "m", 8.0, "inch")
    .addMinorLoss("Valve Station->Compressor Scrubber", "long-radius bend", 0.3);

ProcessSystem routeProcess = route.build(feedStream);
routeProcess.run();
String routeJson = route.toJson();

To embed the extracted route in a larger flowsheet, add it to the existing ProcessSystem and use the returned outlet stream as the inlet to downstream equipment:

ProcessSystem process = new ProcessSystem("Full plant process");
process.add(feedStream);
StreamInterface routeOutlet = route.addToProcessSystem(process, feedStream);
Cooler downstreamCooler = new Cooler("Downstream cooler", routeOutlet);
process.add(downstreamCooler);
process.run();

If the route starts from an upstream equipment outlet, use the overload with source-equipment metadata: route.addToProcessSystem(process, sep.getGasOutStream(), "HP Sep", "gasOut").

Always preserve source document/page/row references in the task notes and export route.toJson() in the task results so later STID work can reuse the route.

Recycle (Detailed)

Recycles enable iterative convergence of process loops. The ProcessSystem automatically detects and iterates recycles up to 100 times.

// 1. Create placeholder stream with estimated conditions
Stream placeholder = new Stream("recycle estimate", fluidGuess.clone());
placeholder.setFlowRate(estimatedFlow, "kg/hr");
placeholder.setTemperature(estimatedT, "C");
placeholder.setPressure(estimatedP, "bara");
process.add(placeholder);

// 2. Build downstream equipment using the placeholder as input
Mixer mixer = new Mixer("recycle mixer");
mixer.addStream(mainFeed);
mixer.addStream(placeholder);       // ← placeholder used here
process.add(mixer);
// ... more equipment in the loop ...

// 3. Create Recycle that connects actual outlet back to placeholder
Recycle recycle = new Recycle("RCY-1");
recycle.addStream(actualOutletStream);    // downstream end of loop
recycle.setOutletStream(placeholder);      // connects back to start
recycle.setTolerance(1e-3);               // tighter than default 1e-2
process.add(recycle);

Convergence tuning:

recycle.setFlowTolerance(1e-3);          // flow convergence (default 1e-2)
recycle.setTemperatureTolerance(1e-3);   // temperature convergence
recycle.setCompositionTolerance(1e-3);   // composition convergence
recycle.setPriority(50);                 // lower = solved first (default 100)
recycle.setAccelerationMethod("Wegstein"); // or "Direct Substitution", "Broyden"

Priority-based nesting: Set lower priority numbers on inner recycle loops. The RecycleController solves lower-priority recycles first, then higher. ProcessSystem hard cap: 100 iterations (not user-configurable).

Adjuster

Adjuster adjuster = new Adjuster("Adj");
adjuster.setAdjustedVariable(equipment, "methodName");
adjuster.setTargetVariable(stream, "methodName", targetValue);

ProcessSystem Assembly

ProcessSystem process = new ProcessSystem();
process.add(feed);
process.add(separator);
process.add(compressor);
process.add(cooler);
process.run();  // Run ONCE after adding all equipment

For multi-area plants, use ProcessModel to combine multiple ProcessSystem instances (see below).

ProcessModel — Combining Multiple Process Areas (MANDATORY for Large Plants)

For large process plants (platforms, refineries, gas plants), split the model into separate ProcessSystem objects per process area, then combine them into a single ProcessModel. NEVER try to add a ProcessModule or ProcessSystem to another ProcessSystem — use ProcessModel as the top-level container.

Architecture Pattern (from reference platform models)

ProcessModel ("Gas Platform")                ← TOP-LEVEL CONTAINER
  ├── ProcessSystem ("well process")          ← Well feed & manifold
  ├── ProcessSystem ("separation train A")    ← HP/LP separation
  ├── ProcessSystem ("separation train B")    ← HP/LP separation
  ├── ProcessSystem ("TEX process A")         ← Turbo-expander
  ├── ProcessSystem ("TEX process B")         ← Turbo-expander
  ├── ProcessSystem ("export compressor A")   ← Gas compression
  ├── ProcessSystem ("export gas")            ← Gas export pipeline
  └── ProcessSystem ("export oil")            ← Oil export

Java Example

// Each area is its own ProcessSystem
ProcessSystem wellProcess = new ProcessSystem();
wellProcess.add(wellFeed);
wellProcess.add(manifold);
wellProcess.add(splitter);

ProcessSystem separationA = new ProcessSystem();
separationA.add(new Heater("HP heater", splitter.getSplitStream(0)));
separationA.add(new ThreePhaseSeparator("1st stage", ...));
// ... more equipment

ProcessSystem compressionA = new ProcessSystem();
compressionA.add(new Compressor("export comp",
    separationA.getUnit("gas mixer").getOutletStream()));  // cross-ref

// Combine into ProcessModel
ProcessModel plant = new ProcessModel();
plant.add("well process", wellProcess);
plant.add("separation train A", separationA);
plant.add("export compressor A", compressionA);
plant.run();  // Iterates until all converge

// Access equipment by process area
plant.get("separation train A").getUnit("1st stage separator");

// Convergence info
System.out.println(plant.getConvergenceSummary());
System.out.println(plant.getMassBalanceReport());

Python Example (Recommended Pattern)

The reference model uses functions that return ProcessSystem objects:

def create_well_feed_model(inp):
    well_process = neqsim.process.processmodel.ProcessSystem()
    feed = Stream("feed", fluid)
    feed.setFlowRate(inp.flow_rate, "kg/hr")
    well_process.add(feed)
    splitter = Splitter("manifold", feed)
    splitter.setSplitFactors([0.5, 0.5])
    well_process.add(splitter)
    return well_process

def create_separation_process(inp, feed_stream):
    sep_process = neqsim.process.processmodel.ProcessSystem()
    separator = ThreePhaseSeparator("1st stage", feed_stream)  # cross-ref!
    sep_process.add(separator)
    # ... more equipment
    return sep_process

# Build and run each area
well_model = create_well_feed_model(params)
well_model.run()

sep_train_A = create_separation_process(params,
    well_model.getUnit("manifold").getSplitStream(0))  # cross-system stream
sep_train_A.run()

# Combine into ProcessModel
ProcessModel = jneqsim.process.processmodel.ProcessModel
plant = ProcessModel()
plant.add("well process", well_model)
plant.add("separation train A", sep_train_A)
plant.run()  # Iterates until convergence

print(plant.getConvergenceSummary())
print(plant.getMassBalanceReport())

ProcessModel Key Features

Feature	Method
Add named sub-process	add("name", processSystem)
Get sub-process	get("name")
Remove sub-process	remove("name")
Run all (iterates to convergence)	run()
Run single step	runStep()
Run in background thread	runAsTask() returns Future
Check convergence	isModelConverged(), getConvergenceSummary()
Mass balance report	getMassBalanceReport(), getFailedMassBalanceReport()
Validation	validateSetup(), validateAll(), getValidationReport()
Execution analysis	getExecutionPartitionInfo()
Set convergence tolerance	setTolerance(1e-4) or individual setFlowTolerance() etc.
Save/load model	saveToNeqsim("file.neqsim"), loadFromNeqsim("file.neqsim")
JSON report	getReport_json()
Automation facade	getAutomation() returns ProcessAutomation (string-addressable variables)
Lifecycle state	ProcessModelState.fromProcessModel(plant), .saveToFile(), .compare(v1, v2)

Cross-System Stream Sharing

Streams cross sub-system boundaries by direct object reference:

• Equipment in System B takes an outlet stream from System A as a constructor argument
• ProcessModel.run() executes systems in insertion order
• System A populates its outlet streams BEFORE System B reads from them
• Order of add() calls matters — add upstream systems first

ProcessModel vs ProcessModule vs ProcessSystem

Class	Purpose	Use When
ProcessSystem	Single process area with equipment	Always — the basic building block
ProcessModel	Named collection of ProcessSystems with convergence tracking	Multi-area plants (platforms, gas plants)
ProcessModule	Legacy container for ProcessSystems	Backward compatibility only — prefer ProcessModel

NEVER add a ProcessModule or ProcessModel to a ProcessSystem — it will throw TypeError.

Key Rules

• Clone fluids before branching: fluid.clone() to avoid shared-state bugs
• Equipment constructors take (String name, StreamInterface inlet)
• Connect equipment via outlet streams — don't create separate streams
• Add equipment to ProcessSystem in topological order
• Call process.run() only ONCE after building the entire flowsheet
• For multi-area plants: use ProcessModel to combine ProcessSystem objects — never nest them

Automation API (String-Addressable Variables)

Use ProcessAutomation for agent-friendly variable access — no Java class navigation needed.

Setup and Discovery

ProcessAutomation auto = process.getAutomation();   // or plant.getAutomation()
List<String> units = auto.getUnitList();             // ["Feed Gas", "HP Sep", ...]
List<SimulationVariable> vars = auto.getVariableList("HP Sep");
// Each variable: address, name, type (INPUT/OUTPUT), defaultUnit, description
String eqType = auto.getEquipmentType("HP Sep");     // "Separator"

Read / Write Variables

// Read with unit conversion (dot-notation addressing)
double temp = auto.getVariableValue("HP Sep.gasOutStream.temperature", "C");
double flow = auto.getVariableValue("HP Sep.gasOutStream.flowRate", "kg/hr");

// Write INPUT variables, then re-run
auto.setVariableValue("Compressor.outletPressure", 150.0, "bara");
process.run();

Multi-Area Addressing

ProcessAutomation plantAuto = plant.getAutomation();
List<String> areas = plantAuto.getAreaList();
// Area-qualified: "Area::Unit.property"
double t = plantAuto.getVariableValue("Separation::HP Sep.gasOutStream.temperature", "C");

Lifecycle State (Save / Restore / Compare)

JSON snapshots for reproducibility and version tracking.

// Save
ProcessSystemState state = ProcessSystemState.fromProcessSystem(process);
state.setName("Gas Processing"); state.setVersion("1.0.0");
state.saveToFile("model_v1.json");

// Load and validate
ProcessSystemState loaded = ProcessSystemState.loadFromFile("model_v1.json");
assert loaded.validate().isValid();

// Multi-area
ProcessModelState ms = ProcessModelState.fromProcessModel(plant);
ms.saveToFile("plant_v1.json");

// Version diff
ProcessModelState.ModelDiff diff = ProcessModelState.compare(v1, v2);
// diff.getModifiedParameters(), diff.getAddedEquipment(), diff.getRemovedEquipment()

// Compressed bytes for API transfer
byte[] bytes = ms.toCompressedBytes();
ProcessModelState restored = ProcessModelState.fromCompressedBytes(bytes);

Design Feasibility Reports

After running equipment in a process simulation, generate a feasibility report to answer: "Is this machine realistic to build? What will it cost? Who can supply it?"

Compressor Feasibility

// After process.run():
CompressorDesignFeasibilityReport report =
    new CompressorDesignFeasibilityReport(compressor);
report.setDriverType("gas-turbine");
report.setCompressorType("centrifugal");
report.setAnnualOperatingHours(8000);
report.generateReport();

String verdict = report.getVerdict();  // FEASIBLE / FEASIBLE_WITH_WARNINGS / NOT_FEASIBLE
String json = report.toJson();         // Full JSON with mech design, cost, suppliers, curves
List<SupplierMatch> suppliers = report.getMatchingSuppliers();

// Apply generated performance curves back to compressor
report.applyChartToCompressor();

Heat Exchanger / Cooler / Heater Feasibility

// After process.run():
HeatExchangerDesignFeasibilityReport hxReport =
    new HeatExchangerDesignFeasibilityReport(heatExchanger);
hxReport.setExchangerType("shell-and-tube");
hxReport.setDesignStandard("TEMA-R");
hxReport.setAnnualOperatingHours(8000);
hxReport.generateReport();

String verdict = hxReport.getVerdict();
String json = hxReport.toJson();
List<HXSupplierMatch> suppliers = hxReport.getMatchingSuppliers();

Key points:

• Equipment must have been run() before generating the report
• Verdicts: FEASIBLE, FEASIBLE_WITH_WARNINGS, NOT_FEASIBLE
• Issues have severity: BLOCKER (not feasible), WARNING (review), INFO (note)
• Supplier matching uses built-in OEM databases (CompressorSuppliers.csv, HeatExchangerSuppliers.csv)
• Reports include: operating point, mechanical design, cost estimation, supplier list, issues
• For compressors: also generates performance curves from templates

When to run feasibility checks:

• Any task involving equipment sizing or selection
• Process design tasks where cost or buildability matters
• Field development or FEED-level studies
• When the user asks "is this realistic?", "can this be built?", "what will it cost?"

Heat Exchanger Thermal-Hydraulic Design

TEMA-level shell-and-tube thermal design with tube/shell-side HTCs, pressure drops, LMTD correction, vibration screening, and full mechanical design.

Standalone Thermal Calculation

ThermalDesignCalculator calc = new ThermalDesignCalculator();
calc.setTubeODm(0.01905);    // 3/4" OD
calc.setTubeIDm(0.01483);
calc.setTubeLengthm(6.0);
calc.setTubeCount(200);
calc.setTubePasses(2);
calc.setTubePitchm(0.0254);
calc.setTriangularPitch(true);
calc.setShellIDm(0.489);
calc.setBaffleSpacingm(0.15);
calc.setBaffleCount(30);
calc.setBaffleCut(0.25);

// Tube-side fluid (density, viscosity, cp, conductivity, massFlow, isHeating)
calc.setTubeSideFluid(995.0, 0.0008, 4180.0, 0.62, 5.0, true);
// Shell-side fluid
calc.setShellSideFluid(820.0, 0.003, 2200.0, 0.13, 8.0);

calc.setShellSideMethod(ThermalDesignCalculator.ShellSideMethod.BELL_DELAWARE);
calc.calculate();
String json = calc.toJson();  // Full results: U, dP, HTCs, zone analysis

LMTD Correction Factor

double ft = LMTDcorrectionFactor.calcFt(tHotIn, tHotOut, tColdIn, tColdOut, 1);  // 1 shell pass
int minShells = LMTDcorrectionFactor.requiredShellPasses(tHotIn, tHotOut, tColdIn, tColdOut);
// MIN_ACCEPTABLE_FT = 0.75

Vibration Screening

VibrationAnalysis.VibrationResult vib = VibrationAnalysis.performScreening(
    tubeOD, tubeID, unsupportedSpan, tubeMaterialE, tubeDensity,
    fluidDensityTube, fluidDensityShell, "fixed-fixed",
    crossflowVelocity, tubePitch, true, shellID, sonicVelocity);
if (!vib.passed) {
    // Check vib.vortexSheddingCritical, vib.fluidElasticCritical, vib.acousticCritical
}

Full Shell-and-Tube Mechanical + Thermal Design

ShellAndTubeDesignCalculator stCalc = new ShellAndTubeDesignCalculator();
stCalc.setTemaDesignation("AES");
stCalc.setTemaClass(TEMAClass.R);
stCalc.setRequiredArea(50.0);           // m²
stCalc.setShellSidePressure(30.0);      // bara
stCalc.setTubeSidePressure(10.0);       // bara
stCalc.setDesignTemperature(200.0);     // °C
stCalc.setShellMaterialGrade("SA-516-70");
stCalc.setTubeMaterialGrade("SA-179");
stCalc.setSourServiceAssessment(true);
stCalc.setH2sPartialPressure(0.01);     // bar

// Provide fluid properties for thermal + vibration analysis
stCalc.setTubeSideFluidProperties(995.0, 0.0008, 4180.0, 0.62, 5.0, true);
stCalc.setShellSideFluidProperties(820.0, 0.003, 2200.0, 0.13, 8.0);
stCalc.setShellSideMethod(ThermalDesignCalculator.ShellSideMethod.BELL_DELAWARE);

stCalc.calculate();  // Runs mechanical + thermal + vibration
String json = stCalc.toJson();  // MAWP, wall thickness, U, dP, vibration, cost, BOM

Standards: TEMA R/C/B, ASME VIII Div.1 (UHX-13, UG-27, UG-37, UG-99), NACE MR0175/ISO 15156, Bell-Delaware, Gnielinski, Von Karman, Connors criterion.

CO2 Injection Well Analysis

Full-stack safety analysis for CO2 injection wells covering steady-state flow, phase boundary mapping, impurity enrichment, shutdown transients, and flow corrections.

CO2InjectionWellAnalyzer (High-Level Orchestrator)

CO2InjectionWellAnalyzer analyzer = new CO2InjectionWellAnalyzer("InjectionWell-1");
analyzer.setFluid(co2Fluid);
analyzer.setWellGeometry(1300.0, 0.1571, 5e-5);      // depth_m, tubingID_m, roughness_m
analyzer.setOperatingConditions(90.0, 25.0, 150000.0); // WHP_bara, WHT_C, flow_kg/hr
analyzer.setFormationTemperature(4.0, 43.0);            // top_C, bottom_C
analyzer.addTrackedComponent("hydrogen", 0.10);         // name, alarm mol fraction
analyzer.addTrackedComponent("nitrogen", 0.05);
analyzer.runFullAnalysis();

boolean safe = analyzer.isSafeToOperate();
Map<String, Object> results = analyzer.getResults();

ImpurityMonitor (Measurement Device)

ImpurityMonitor monitor = new ImpurityMonitor("H2-Monitor", stream);
monitor.addTrackedComponent("hydrogen", 0.10);   // alarm at 10 mol%
monitor.setPrimaryComponent("hydrogen");

// After process.run():
double gasH2 = monitor.getGasPhaseMoleFraction("hydrogen");
double enrichment = monitor.getEnrichmentFactor("hydrogen"); // y_gas / z_feed
boolean alarm = monitor.isAlarmExceeded("hydrogen");
Map<String, Map<String, Double>> report = monitor.getFullReport();

TransientWellbore (Shutdown Cooling)

TransientWellbore wellbore = new TransientWellbore("Shutdown", stream);
wellbore.setWellDepth(1300.0);
wellbore.setTubingDiameter(0.1571);
wellbore.setFormationTemperature(273.15 + 4.0, 273.15 + 43.0);
wellbore.setShutdownCoolingRate(6.0);   // tau = 6 hours
wellbore.setNumberOfSegments(10);

wellbore.runShutdownSimulation(48.0, 1.0);  // 48 hours, 1-hour steps
List<TransientSnapshot> snaps = wellbore.getSnapshots();
double maxH2 = wellbore.getMaxGasPhaseConcentration("hydrogen");

PipeBeggsAndBrills (Formation Temperature Gradient)

PipeBeggsAndBrills pipe = new PipeBeggsAndBrills("Wellbore", feed);
pipe.setLength(1300.0);
pipe.setElevation(-1300.0);    // downward
pipe.setDiameter(0.1571);
pipe.setFormationTemperatureGradient(4.0, -0.03, "C"); // 4°C top, -30°C/km (increases with depth)
pipe.run();

CO2FlowCorrections (Static Utility)

boolean co2Dominant = CO2FlowCorrections.isCO2DominatedFluid(system);      // > 50 mol% CO2
double holdupCorr = CO2FlowCorrections.getLiquidHoldupCorrectionFactor(system);  // 0.70–0.85
double frictionCorr = CO2FlowCorrections.getFrictionCorrectionFactor(system);    // 0.85–0.95
boolean dense = CO2FlowCorrections.isDensePhase(system);
double Tr = CO2FlowCorrections.getReducedTemperature(system);

Engineering Deliverables

Generate study-class-appropriate engineering documents from a converged ProcessSystem.

StudyClass and Package

// Standalone — generates all deliverables for the selected study class
EngineeringDeliverablesPackage pkg =
    new EngineeringDeliverablesPackage(process, StudyClass.CLASS_A);
pkg.generate();
String json = pkg.toJson();

// Through orchestrator
orchestrator.setStudyClass(StudyClass.CLASS_A);
orchestrator.runCompleteDesignWorkflow();
EngineeringDeliverablesPackage pkg = orchestrator.getEngineeringDeliverables();

Study Class	Deliverables
CLASS_A (FEED/Detail)	PFD, Thermal Utilities, Alarm/Trip, Spare Parts, Fire Scenarios, Noise, Instrument Schedule
CLASS_B (Concept/Pre-FEED)	PFD, Thermal Utilities, Fire Scenarios, Instrument Schedule
CLASS_C (Screening)	PFD only

Instrument Schedule Generator (with Live Device Bridge)

Creates ISA-5.1 tagged instruments and optionally registers real MeasurementDeviceInterface objects on the ProcessSystem for dynamic simulation:

InstrumentScheduleGenerator instrGen = new InstrumentScheduleGenerator(process);
instrGen.setRegisterOnProcess(true);  // bridge: creates live MeasurementDevice objects
instrGen.generate();

// Query instruments
List<InstrumentScheduleGenerator.InstrumentEntry> all = instrGen.getEntries();
List<InstrumentScheduleGenerator.InstrumentEntry> pts =
    instrGen.getEntriesByType(InstrumentScheduleGenerator.MeasuredVariable.PRESSURE);

// Each entry has: tag, equipmentName, service, measuredVariable, rangeMin/Max, unit,
//                 alarmHH/H/L/LL, silRating, liveDevice (if registerOnProcess=true)
for (InstrumentScheduleGenerator.InstrumentEntry e : all) {
    System.out.println(e.getTag() + " " + e.getEquipmentName()
        + " SIL=" + e.getSilRating());
    if (e.getLiveDevice() != null) {
        // Real MeasurementDevice registered on ProcessSystem
        System.out.println("  Live: " + e.getLiveDevice().getMeasuredValue());
    }
}

String instrJson = instrGen.toJson();

Tag numbering convention: PT-100+, TT-200+, LT-300+, FT-400+ (ISA-5.1).

Phase Envelope Calculation and Interpretation

For phase-envelope generation, plotting, physical branch classification, zero/trace-component handling, or Michelsen solver changes, load neqsim-phase-envelope. This section is the compact API reference; the dedicated skill owns the end-to-end workflow and regression rules.

Calculating a PT Phase Envelope

SystemInterface fluid = new SystemSrkEos(273.15 + 25.0, 50.0);
fluid.addComponent("methane", 0.85);
fluid.addComponent("ethane", 0.10);
fluid.addComponent("propane", 0.05);
fluid.setMixingRule("classic");

ThermodynamicOperations ops = new ThermodynamicOperations(fluid);
ops.calcPTphaseEnvelope(true, 1.0);  // bubblePointFirst=true, lowPres=1.0 bara

// Access envelope data via the operation object
PTPhaseEnvelopeMichelsen envelope = (PTPhaseEnvelopeMichelsen) ops.getOperation();
double[] cricondenBar = envelope.getCricondenBar();    // [T_K, P_bara, 0]
double[] cricondenTherm = envelope.getCricondenTherm(); // [T_K, P_bara, 0]
double critT = envelope.getCriticalTemperature();       // Kelvin
double critP = envelope.getCriticalPressure();          // bara

CRITICAL: Branch Classification Bug with bubblePointFirst=true

When using calcPTphaseEnvelope(true, 1.0) (bubblePointFirst=true), the NeqSim Michelsen algorithm stores the envelope branches with SWAPPED labels:

• getBubblePointTemperatures() / getBubblePointPressures() → actually the DEW curve (right side, higher T, includes cricondentherm)
• getDewPointTemperatures() / getDewPointPressures() → actually the BUBBLE curve (left side, lower T)

Root cause: The algorithm initializes isDewPhase=true regardless of the bubblePointFirst flag. When starting from the bubble side, initial points go into the dew list. At the critical point, isDewPhase flips, sending post-CP points (the actual dew side) into the bubble list.

Always determine which branch is which using physical reasoning:

branch_A_T = np.array(envelope.getBubblePointTemperatures())
branch_A_P = np.array(envelope.getBubblePointPressures())
branch_B_T = np.array(envelope.getDewPointTemperatures())
branch_B_P = np.array(envelope.getDewPointPressures())

# The DEW curve always contains the cricondentherm (maximum temperature)
if branch_A_T.max() > branch_B_T.max():
    dew_T, dew_P = branch_A_T, branch_A_P
    bub_T, bub_P = branch_B_T, branch_B_P
else:
    dew_T, dew_P = branch_B_T, branch_B_P
    bub_T, bub_P = branch_A_T, branch_A_P

Phase Envelope Physical Interpretation

Bubble point curve (left side of envelope):

• Boundary between subcooled liquid and two-phase region
• At the bubble point, the first infinitesimal bubble of vapor forms
• Crossing from left to right: liquid → two-phase

Dew point curve (right side of envelope):

• Boundary between superheated vapor and two-phase region
• At the dew point, the first infinitesimal drop of liquid forms
• Crossing from right to left: vapor → two-phase

Key points on the envelope:

• Critical point: Where bubble and dew curves meet; liquid and vapor become indistinguishable
• Cricondenbar: Maximum pressure on the envelope (above this, no two-phase region exists at any T)
• Cricondentherm: Maximum temperature on the envelope (above this, no liquid forms at any P); always on the DEW curve side
• For lean gas (mostly methane): cricondenbar and cricondentherm are both on the dew curve side, close to the critical point
• For rich gas/condensate: the envelope is wider; cricondentherm extends to significantly higher temperatures

Retrograde condensation region (between cricondenbar and cricondentherm on the dew curve):

• Reducing pressure at constant T causes MORE liquid to form (counter-intuitive)
• This is critical for gas condensate reservoirs and pipeline design

Documentation Code Verification

When writing code examples for documentation (markdown guides, cookbook recipes, tutorials):

1. Read the source class first — verify every method signature, constructor, inner class
2. Write a JUnit test that calls every documented API method (append to DocExamplesCompilationTest.java)
3. Run the test and confirm it passes before publishing the doc
4. Common pitfalls:
   • Plus fraction names: use "C20" not "C20+" (the + character breaks parsing)
   • Set mixing rule BEFORE calling characterisePlusFraction()
   • getUnit("name") not getUnitOperation("name")
   • setDepreciationYears takes double, not int
   • Risk thresholds: always read source for actual comparison logic (subcooling direction, enum ordering)