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Merge pull request #17 from pathsim/feature/ikcape-correlations
ikcape correlations
2 parents 43fd9d3 + 0c3f907 commit ab37ecc

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‎.github/workflows/tests.yml‎

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name: Run tests
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on: [push, pull_request]
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jobs:
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test:
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runs-on: ubuntu-latest
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steps:
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- uses: actions/checkout@v4
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- name: Set up Python
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uses: actions/setup-python@v5
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with:
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python-version: '3.x'
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- name: Install dependencies
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run: |
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python -m pip install --upgrade pip
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pip install -e .[test]
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- name: Test with pytest
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run: |
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pytest tests/ -v

‎README.md‎

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<img src="https://raw.githubusercontent.com/pathsim/pathsim-chem/main/docs/source/logos/chem_logo.png" width="300" alt="PathSim-Chem Logo" />
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</p>
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------------
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<p align="center">
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<strong>Chemical engineering blocks for PathSim</strong>
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</p>
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<p align="center">
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<a href="https://pypi.org/project/pathsim-chem/"><img src="https://img.shields.io/pypi/v/pathsim-chem" alt="PyPI"></a>
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<img src="https://img.shields.io/github/license/pathsim/pathsim-chem" alt="License">
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</p>
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<p align="center">
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<a href="https://docs.pathsim.org/chem">Documentation</a> &bull;
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<a href="https://pathsim.org">PathSim Homepage</a> &bull;
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<a href="https://github.com/pathsim/pathsim-chem">GitHub</a>
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</p>
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---
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PathSim-Chem extends the [PathSim](https://github.com/pathsim/pathsim) simulation framework with blocks for chemical engineering and thermodynamic property calculations. All blocks follow the standard PathSim block interface and can be connected into simulation diagrams.
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## Features
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- **IK-CAPE Thermodynamics** — 50+ blocks implementing the DECHEMA IK-CAPE standard for thermodynamic property calculations
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- **Pure Component Correlations** — Antoine, Wagner, Kirchhoff, Rackett, Aly-Lee, DIPPR, and 10 more temperature-dependent property correlations
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- **Mixing Rules** — Linear, quadratic, Lorentz-Berthelot, and other calculation-of-averages rules for mixture properties
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- **Activity Coefficients** — NRTL, Wilson, UNIQUAC, and Flory-Huggins models for liquid-phase non-ideality
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- **Equations of State** — Peng-Robinson and Soave-Redlich-Kwong cubic EoS with mixture support
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- **Fugacity Coefficients** — EoS-based and virial equation fugacity calculations
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- **Excess Enthalpy & Departure** — NRTL, UNIQUAC, Wilson, Redlich-Kister excess enthalpy and EoS departure functions
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- **Chemical Reactions** — Equilibrium constants, kinetic rate constants, and power-law rate expressions
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- **Tritium Processing** — GLC columns, TCAP cascades, bubblers, and splitters for tritium separation
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## Install
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```bash
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pip install pathsim-chem
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```
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## Quick Example
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Compute the vapor pressure of water at 100 °C using the Antoine equation:
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```python
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from pathsim_chem.thermodynamics import Antoine
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# Antoine coefficients for water (NIST)
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antoine = Antoine(a0=23.2256, a1=3835.18, a2=-45.343)
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# Evaluate at 373.15 K
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antoine.inputs[0] = 373.15
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antoine.update(None)
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P_sat = antoine.outputs[0] # ≈ 101325 Pa
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```
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Use activity coefficients in a simulation:
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```python
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from pathsim_chem.thermodynamics import NRTL
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# Ethanol-water NRTL model
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nrtl = NRTL(
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x=[0.4, 0.6],
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a=[[0, -0.801], [3.458, 0]],
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c=[[0, 0.3], [0.3, 0]],
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)
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# Evaluate at 350 K
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nrtl.inputs[0] = 350
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nrtl.update(None)
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gamma_ethanol = nrtl.outputs[0]
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gamma_water = nrtl.outputs[1]
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```
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## Modules
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| Module | Description |
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|---|---|
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| `pathsim_chem.thermodynamics.correlations` | 16 pure component property correlations (Antoine, Wagner, etc.) |
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| `pathsim_chem.thermodynamics.averages` | 10 mixing rules for calculation of averages |
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| `pathsim_chem.thermodynamics.activity_coefficients` | NRTL, Wilson, UNIQUAC, Flory-Huggins |
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| `pathsim_chem.thermodynamics.equations_of_state` | Peng-Robinson, Soave-Redlich-Kwong |
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| `pathsim_chem.thermodynamics.corrections` | Poynting correction, Henry's law |
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| `pathsim_chem.thermodynamics.fugacity_coefficients` | RKS, PR, and virial fugacity coefficients |
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| `pathsim_chem.thermodynamics.enthalpy` | Excess enthalpy and enthalpy departure functions |
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| `pathsim_chem.thermodynamics.reactions` | Equilibrium constants, rate constants, power-law rates |
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| `pathsim_chem.tritium` | GLC, TCAP, bubbler, splitter blocks for tritium processing |
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## Learn More
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- [Documentation](https://docs.pathsim.org/chem) — API reference and examples
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- [PathSim](https://github.com/pathsim/pathsim) — the core simulation framework
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- [Contributing](https://docs.pathsim.org/pathsim/latest/contributing) — how to contribute
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# PathSim Chemical Engineering Toolbox
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## License
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This toolbox extends the core pathsim package with domain specific component models for chemical engineering.
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MIT

‎docs/source/examples/equation_of_state.ipynb‎

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{
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"cells": [
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"# Cubic Equations of State\n",
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"\n",
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"Simulating the compressibility factor of methane across a pressure sweep using the Peng-Robinson and Soave-Redlich-Kwong equations of state wired into a PathSim simulation."
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"Cubic equations of state compute the compressibility factor $Z = Pv/(RT)$ by solving a cubic polynomial at each $(T, P)$ condition. The EoS blocks take two inputs (temperature and pressure) and produce two outputs (molar volume and compressibility factor).\n",
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"\n",
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"At low pressure $Z \\to 1$ (ideal gas). At moderate pressure attractive forces cause $Z < 1$, and at high pressure excluded-volume effects push $Z > 1$."
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {},
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"outputs": [],
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"source": [
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"import matplotlib.pyplot as plt\n",
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"\n",
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"from pathsim import Simulation, Connection\n",
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"from pathsim.blocks import Source, Constant, Scope\n",
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"\n",
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"from pathsim_chem.thermodynamics import PengRobinson, RedlichKwongSoave"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## System Definition\n",
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"\n",
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"Create Peng-Robinson and SRK blocks for pure methane. A `Constant` block supplies a fixed temperature while a `Source` sweeps pressure from 0.1 MPa to 30 MPa."
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {},
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"outputs": [],
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"source": [
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"# Critical properties of methane\n",
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"Tc, Pc, omega = 190.6, 4.6e6, 0.011\n",
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"\n",
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"# EoS blocks\n",
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"pr = PengRobinson(Tc=Tc, Pc=Pc, omega=omega)\n",
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"rks = RedlichKwongSoave(Tc=Tc, Pc=Pc, omega=omega)\n",
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"\n",
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"# Fixed temperature, logarithmic pressure sweep\n",
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"import numpy as np\n",
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"T_const = Constant(250) # 250 K (above Tc, supercritical)\n",
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"P_src = Source(func=lambda t: 10**(4 + t * 0.035)) # 10 kPa to ~30 MPa over 100s\n",
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"\n",
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"# Scopes: record Z from both EoS (output port 1)\n",
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"scp_pr = Scope(labels=[\"Z_PR\"])\n",
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"scp_rks = Scope(labels=[\"Z_RKS\"])"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Wiring\n",
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"\n",
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"Both EoS blocks receive the same $(T, P)$ inputs. We record the compressibility factor (output port 1) from each."
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {},
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"outputs": [],
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"source": [
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"sim = Simulation(\n",
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" blocks=[T_const, P_src, pr, rks, scp_pr, scp_rks],\n",
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" connections=[\n",
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" # Temperature -> both EoS (input port 0)\n",
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" Connection(T_const, pr, rks),\n",
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" # Pressure -> both EoS (input port 1)\n",
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" Connection(P_src, pr[1], rks[1]),\n",
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" # Z output (port 1) -> scopes\n",
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" Connection(pr[1], scp_pr),\n",
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" Connection(rks[1], scp_rks),\n",
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" ],\n",
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" dt=1.0,\n",
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")\n",
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"\n",
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"sim.run(100)"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {},
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"outputs": [],
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"source": [
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"time, Z_pr = scp_pr.read()\n",
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"_, Z_rks = scp_rks.read()\n",
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"P_vals = 10**(4 + time * 0.035) / 1e6 # MPa\n",
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"\n",
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"fig, ax = plt.subplots(figsize=(7, 5))\n",
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"ax.semilogx(P_vals, Z_pr[0], label=\"Peng-Robinson\")\n",
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"ax.semilogx(P_vals, Z_rks[0], \"--\", label=\"Soave-Redlich-Kwong\")\n",
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"ax.axhline(1.0, color=\"gray\", linestyle=\"-.\", alpha=0.5, label=\"Ideal gas\")\n",
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"ax.set_xlabel(\"Pressure [MPa]\")\n",
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"ax.set_ylabel(\"Compressibility Factor Z\")\n",
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"ax.set_title(\"Methane at T = 250 K\")\n",
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"ax.legend()\n",
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"ax.grid(True, alpha=0.3)\n",
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"plt.tight_layout()\n",
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"plt.show()"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"Both EoS give very similar results. The characteristic dip below $Z = 1$ at moderate pressures reflects attractive intermolecular forces, while the rise above $Z = 1$ at high pressures is due to repulsive (excluded volume) effects."
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Mixture\n",
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"\n",
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"The EoS blocks also support mixtures through van der Waals one-fluid mixing rules. Here we set up a methane-ethane mixture and sweep pressure."
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {},
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"outputs": [],
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"source": [
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"pr_mix = PengRobinson(\n",
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" Tc=[190.6, 305.3],\n",
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" Pc=[4.6e6, 4.872e6],\n",
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" omega=[0.011, 0.099],\n",
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" x=[0.7, 0.3],\n",
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")\n",
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"\n",
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"T_const2 = Constant(300)\n",
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"P_src2 = Source(func=lambda t: 10**(4 + t * 0.035))\n",
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"scp_mix = Scope(labels=[\"Z_mixture\"])\n",
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"\n",
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"sim_mix = Simulation(\n",
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" blocks=[T_const2, P_src2, pr_mix, scp_mix],\n",
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" connections=[\n",
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" Connection(T_const2, pr_mix),\n",
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" Connection(P_src2, pr_mix[1]),\n",
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" Connection(pr_mix[1], scp_mix),\n",
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" ],\n",
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" dt=1.0,\n",
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")\n",
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"\n",
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"sim_mix.run(100)"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {},
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"outputs": [],
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"source": [
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"time_m, Z_mix = scp_mix.read()\n",
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"P_mix = 10**(4 + time_m * 0.035) / 1e6\n",
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"\n",
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"fig, ax = plt.subplots(figsize=(7, 5))\n",
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"ax.semilogx(P_vals, Z_pr[0], label=\"Pure CH₄ (250 K)\")\n",
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"ax.semilogx(P_mix, Z_mix[0], \"--\", label=\"70/30 CH₄-C₂H₆ (300 K)\")\n",
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"ax.axhline(1.0, color=\"gray\", linestyle=\"-.\", alpha=0.5)\n",
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"ax.set_xlabel(\"Pressure [MPa]\")\n",
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"ax.set_ylabel(\"Compressibility Factor Z\")\n",
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"ax.set_title(\"Peng-Robinson: Pure vs Mixture\")\n",
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"ax.legend()\n",
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"ax.grid(True, alpha=0.3)\n",
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"plt.tight_layout()\n",
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"plt.show()"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"The mixture shows a deeper dip because ethane ($T_c = 305.3$ K) is near its critical temperature at 300 K, leading to stronger non-ideal behavior."
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]
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}
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],
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"metadata": {
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"kernelspec": {
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"display_name": "Python 3",
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"language": "python",
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"name": "python3"
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},
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"language_info": {
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"name": "python",
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"version": "3.11.0"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 4
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}

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