# Thermo Process Properties

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- **Type:** Skill
- **Install:** `agentstack add skill-jskherman-engg-skills-thermo-process-properties`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [jskherman](https://agentstack.voostack.com/s/jskherman)
- **Installs:** 0
- **Category:** [Agent Skills](https://agentstack.voostack.com/c/agent-skills)
- **Latest version:** 0.1.0
- **License:** Apache-2.0
- **Upstream author:** [jskherman](https://github.com/jskherman)
- **Source:** https://github.com/jskherman/engg-skills/tree/main/skills/thermo-process-properties

## Install

```sh
agentstack add skill-jskherman-engg-skills-thermo-process-properties
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# Thermodynamic Property Calculations

## Overview

Caleb Bell library wrapper utilities. Implements:

- `recommend`: property-method recommendation given components and
  application context.
- `costald-density`: COSTALD (saturated) or COSTALD_compressed mixture
  liquid density for light hydrocarbons.
- `pr-translated-eos`: instantiate `thermo.eos_mix.PRMIXTranslatedPPJP`
  with reported molar volumes, Z-factors, and departure functions.
- `iapws-state` / `iapws-saturation`: pure water / steam properties.

Heuristics for method selection are transparent and built from public
sources (DWSIM, Carlson, AVEVA / Aspen training material). No
proprietary defaults are reproduced.

## Prerequisites

1. `uv` available.
2. On first use, the script writes `LICENSE_NOTIFICATION.txt` listing
   the upstream library terms.

## When to Use

- Picking a property method for a flowsheet zone.
- Estimating LPG liquid density at storage / vessel conditions (COSTALD).
- Getting a Translated-PR liquid molar volume for an LPG mixture.
- Pure-water / steam state at known T, P.

## Don't use for

- Multi-component flash (`vle-flash-calculations`).
- EOS decision tree by itself (`equation-of-state-selection`).
- Steam-table-only calculations (`steam-tables-iapws`).
- Non-LPG hydrocarbon systems where COSTALD is outside its accuracy
  envelope.

## Utility Scripts

- `uv run scripts/property_methods.py recommend --components propane,n-butane,isobutane --application LPG --pressure-pa 1200000 --output /tmp/method.json`
- `uv run scripts/property_methods.py costald-density --components propane,n-butane --zs 0.5,0.5 --temperature-k 300 --pressure-pa 1000000 --output /tmp/lpg_density.json`
- `uv run scripts/property_methods.py iapws-state --temperature-k 373.15 --pressure-pa 101325 --output /tmp/steam.json`
- `uv run scripts/property_methods.py pr-translated-eos --components propane,n-butane --zs 0.5,0.5 --temperature-k 300 --pressure-pa 1000000 --output /tmp/pr.json`

## Procedure

1. Identify components and the operating envelope (T, P, composition).
2. Run `recommend` for a property-method check.
3. For LPG liquid density at vessel conditions, prefer COSTALD compressed.
4. For pure water/steam, prefer IAPWS.
5. For full flash, hand off to `vle-flash-calculations` with the selected
   EOS.

## Pitfalls

- Using PR (default) for LPG liquid density at moderate pressure; PR
  underpredicts liquid density by 5-15%. Use Translated-PR or COSTALD.
- Using COSTALD for a non-light-hydrocarbon (water, alcohol, amine);
  COSTALD is accurate only for nonpolar light hydrocarbons.
- Using IAPWS for water-in-hydrocarbon systems; IAPWS is pure water only.
- Passing the kij matrix as zeros for a sour LPG mixture; H2S / mercaptan
  / amine interactions need real kij.
- Confusing mass density (kg/m³) with molar volume (m³/mol).
- Treating the PRMIXTranslatedPPJP molar volume as exact without
  providing the per-component translation constants `cs`.
- Using `recommend` output as a final decision without doing the
  second-opinion flash recommended by the decision-tree.
- Treating water-content trace as negligible without checking with a
  hydrate / glycol skill.

## Fallback Strategies

- If `thermo` / `chemicals` import fails for an exotic component, fall
  back to built-in LPG defaults via `engg_skills_common.property_backends`.
- For density that is wildly off, switch from COSTALD to
  PRMIXTranslatedPPJP (or vice versa) and report both.

## Verification

- Run the listed script with representative inputs and an `--output` file when a deterministic calculation is available.
- Confirm the JSON result contains `ok: true`, expected units, and no unhandled warnings.
- Check result magnitudes against the stated assumptions, references, and a hand calculation or known operating range before reporting them.

## References

- `references/property_method_selection.md` — full method matrix.
- `references/caleb_bell_libraries.md` — library overview and links.
- `thermo` docs: https://thermo.readthedocs.io/
- `chemicals` docs: https://chemicals.readthedocs.io/
- DWSIM property package selection wiki.

## Anti-Patterns

- Reporting properties without naming the EOS or correlation.
- Using cubic EOS for steam.
- Reporting LPG liquid density without naming whether COSTALD or PR was
  used.

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [jskherman](https://github.com/jskherman)
- **Source:** [jskherman/engg-skills](https://github.com/jskherman/engg-skills)
- **License:** Apache-2.0

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-jskherman-engg-skills-thermo-process-properties
- Seller: https://agentstack.voostack.com/s/jskherman
- Browse the marketplace: https://agentstack.voostack.com/browse

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