title: “Thermodynamic Documentation Set” description: “This folder collects topic-specific documentation for using NeqSim’s thermodynamic, PVT, and physical property capabilities. Each page is intended to be self-contained while pointing to related guides…” —
This folder collects topic-specific documentation for using NeqSim’s thermodynamic, PVT, and physical property capabilities. Each page is intended to be self-contained while pointing to related guides so you can jump directly to the workflows you need.
Package Structure
thermo/
├── system/ # Fluid-system and equation-of-state implementations
├── phase/ # Phase models and calculations
├── component/ # Pure-component and mixture-component properties
├── mixingrule/ # Equation-of-state mixing rules
└── characterization/ # TBP and plus-fraction characterization
Subpackage Documentation
| Subpackage | Description | Documentation |
|---|---|---|
| system | Equations of state implementations | system/README.md |
| phase | Phase modeling (gas, liquid, solid, asphaltene) | phase/README.md |
| component | Component property calculations | component/README.md |
| mixingrule | Binary interaction parameters | mixingrule/README.md |
| characterization | Plus fraction and asphaltene characterization | characterization/README.md |
Guide Contents
Core Guides
- Thermodynamic Models Guide: Comprehensive overview of all thermodynamic models in NeqSim, including equations of state, CPA, reference equations (GERG-2008, EOS-CG), activity coefficient models, electrolyte models, and the auto-select feature. Covers theory, usage, and model selection guidelines.
- Mercury Thermodynamics: Mercury-focused workflow for SRK-TwuCoon-Statoil-EOS, TPflash setup, INTER-table usage, and thesis-linked correlation guidance.
- Søreide-Whitson Model: Gas solubility in brine - Modified Peng-Robinson EoS with salinity-dependent alpha function for water. Essential for produced water emission calculations and used in NeqSimLive. Includes mathematical formulation, salt type coefficients, validation data, and literature references.
- Fluid Creation Guide: Comprehensive guide to creating fluids in NeqSim, including all available equations of state, mixing rules, and model selection guidelines.
- Mixing Rules Guide: Detailed documentation on mixing rules, including mathematical formulations, binary interaction parameters, and usage examples for different applications.
- Flash Calculations Guide: Comprehensive documentation of flash calculations available via ThermodynamicOperations, including TP, PH, PS, VU flashes, saturation calculations, and hydrate equilibria.
- Reactive Flash: Simultaneous chemical and phase equilibrium using the Modified RAND method. Covers reactive TP and PH flash for systems with gas-phase reactions, ionic equilibria, and multiphase reactive systems.
- Hydrate Models Guide: Comprehensive documentation of gas hydrate thermodynamic models, including van der Waals-Platteeuw theory, Structure I/II hydrates, CPA and PVTsim implementations, and inhibitor modeling.
- Electrolyte CPA Model: Detailed documentation of the electrolyte CPA model, including Fürst electrostatic contributions, validation data, and usage examples.
Database Documentation
- Component Database Guide: Detailed documentation of the COMP pure component parameters database, including parameter descriptions, units, and links to thermodynamic models.
- INTER Table Guide: Detailed documentation of the INTER binary interaction parameters database, including column reference for all EoS, CPA, Huron-Vidal, Wong-Sandler, and NRTL parameters.
Reference Documentation
- Mathematical Models: Equations of state, activity-coefficient formulations, and transport correlations available in NeqSim.
- GERG-2008 and EOS-CG: Detailed guide to the reference equations of state for natural gas and CCS applications.
Acid Gas and Sour Fluid Modeling
- H2S Distribution Guide: H2S phase distribution modeling between gas, oil, and water using SRK, PR, CPA, and Electrolyte-CPA equations of state. Covers acid-base chemistry, pH effects, and salinity impacts.
- H2S Distribution Modeling (Detailed): Comprehensive H2S modeling including chemical reactions, model selection guidance, and validation examples.
- Amine CO2 Solubility (Kent-Eisenberg): Screening-level CO2 solubility in aqueous MEA / DEA / MDEA / activated-MDEA solvents using the Kent-Eisenberg apparent-equilibrium-constant model. Covers the validated screening API, validation status, equations, and usage examples.
Application Guides
- Thermodynamic Workflows: How to set up systems, select models, and perform common equilibrium calculations.
- Adsorption Isotherm Models: Complete reference for all adsorption isotherm models — Langmuir, Extended Langmuir, BET, Freundlich, Sips, DRA potential theory, capillary condensation, and the parameter database.
- PVT and Fluid Characterization: Building realistic fluid descriptions, including heavy-end handling and lab-data reconciliation.
- Thermodynamic Operations: Flash calculations, phase envelopes, and other process-centric operations.
- Physical Properties: Density, viscosity, surface tension, and transport-property calculations.
- Attainable Metastability — Volume Balancing Method: Superheat / pressure-undershoot limit of a rapidly depressurising liquid (Log, 2025). Rarefaction-outflow vs. Plesset-Zwick bubble-growth balance, the
n_bubtuning parameter, and a CO₂ blowdown example.
Examples are written for the Java API unless a page says otherwise. Python uses the NeqSim gateway and different import conventions; follow the Python quickstart rather than translating Java syntax literally.