---
title: NeqSim Base Modules
description: This document provides an overview of the seven foundational modules that make up NeqSim. Each module resides under `src/main/java/neqsim` and works together to support fluid characterization and proc...
---

# NeqSim Base Modules

This document provides an overview of the seven foundational modules that make up NeqSim. Each module resides under `src/main/java/neqsim` and works together to support fluid characterization and process design.

## Thermodynamic routines
- **Location:** `thermo` and `thermodynamicoperations`
- **Features:** fluid phase equilibria, equation-of-state implementations, flash and phase envelope calculations.

## Physical properties routines
- **Location:** `physicalproperties`
- **Features:** density, viscosity, heat capacity and other transport properties calculated from thermodynamic state.

## Fluid mechanic routines
- **Location:** `fluidmechanics`
- **Features:** models for steady-state and transient flow, pipeline hydraulics, and flow node/leg modelling.

## Unit operations
- **Location:** `process/equipment`
- **Features:** library of process equipment including separators, heat exchangers, valves and other common unit operations.
- **Distillation columns:** nine solver modes (direct substitution, damped, inside-out, adaptive matrix inside-out, Wegstein, sum-rates, Newton temperature correction, Naphtali-Sandholm simultaneous MESH correction, and MESH residual monitoring) with convergence diagnostics and Murphree efficiency support. See [distillation column docs](wiki/distillation_column.md).

## Chemical reactions routines
- **Location:** `chemicalreactions`
- **Features:** equilibrium and kinetic reaction models with support for reaction mechanisms and kinetic rate expressions.

## Parameter fitting routines
- **Location:** `statistics/parameterfitting`
- **Features:** tools for regression and parameter estimation using experimental data, including Monte Carlo simulations.

## Process simulation routines
- **Location:** `process`
- **Features:** framework for assembling flowsheets and running dynamic or steady-state process simulations that couple unit operations and property packages.

## Process safety simulation
- **Location:** `process/safety`, `process/equipment/tank`, `process/util/fire`
- **Features:** comprehensive safety simulation capabilities including:
  - **Depressurization:** Dynamic vessel blowdown with multiple thermodynamic modes (isothermal, isentropic, energy balance), fire case modeling, and transient wall heat transfer
  - **Relief valve sizing:** API 520/521 compliant PSV sizing with dynamic fire scenarios
  - **Source term generation:** Leak/rupture mass flow, jet velocity, and momentum calculations for consequence modeling (PHAST, FLACS, KFX export)
  - **Safety envelopes:** Hydrate, WAX, CO2 freezing, and MDMT envelope calculations with operating point validation
  - **Risk framework:** Monte Carlo and deterministic risk analysis with event trees, sensitivity analysis, and F-N curve generation