DWSIM MCP Server

Lets Claude open, build, edit, solve and report on DWSIM process simulations on your Windows PC -- either live in a DWSIM window you're watching, or in a hidden background copy of DWSIM.

Platform: Windows 10/11 only, tested with DWSIM 9.0.5 (classic .NET Framework build). macOS/Linux aren't supported -- the classic DWSIM build is Windows-only and the cross-platform build can't be automated from Python; run both inside a Windows virtual machine instead.

Not affiliated with DWSIM. DWSIM is developed by Daniel Medeiros and contributors (https://dwsim.org). This is an independent project that uses DWSIM's public automation API.

Check the results. This is an engineering tool driven by an AI assistant. Simulation results depend on the thermodynamic model and data you choose (see the model notes below) -- verify them independently before using them for design, operation or safety decisions. Provided as is, without warranty (see LICENSE).

Requirements

• Windows 10/11 (64-bit).

• DWSIM, classic .NET Framework build -- developed and tested with DWSIM 9.0.5. This is the build with DWSIM.exe and DWSIM.Automation.dll in its folder (the default per-user install goes to %LOCALAPPDATA%\DWSIM). The newer cross-platform (Avalonia / self-contained .NET) build does not work: pythonnet can't host self-contained .NET deployments.

• .NET Framework 4.6.2+ (already present on current Windows; it also provides the C# compiler used to build the DWSIM extender).

• Python 3.10-3.13, 64-bit, from python.org (not the Microsoft Store alias).

• Claude Desktop (or Claude Code).

• Internet access only for the optional Cheméo compound lookups.

Related MCP server: opm-mcp

Quick start

1. Download the latest release from Releases (currently v0.1.0): under Assets, choose Source code (zip) and unzip it anywhere -- or git clone https://github.com/markKinyingi/dwsim_9.0.5_mcp.git to get updates with git pull. What changed in each version is in CHANGELOG.md.

2. Close DWSIM, then from this folder run:

   powershell -ExecutionPolicy Bypass -File setup.ps1

   It installs the Python requirements, finds DWSIM, builds and installs the MCP Bridge extender into DWSIM (allow-listing exactly your Python + this folder's server.py), and adds the dwsim server to Claude Desktop's config (keeping a backup). Options: -Python <path>, -DwsimPath <folder>, -SkipClaudeConfig, -RunExamples.

3. Fully quit Claude Desktop (system tray too) and reopen it.

4. Check it works -- either ask Claude "Use the dwsim tools to locate DWSIM", or run the end-to-end test, which rebuilds the example simulations through the MCP server and checks the results:

   python examples\build_examples.py

5. For live editing, open DWSIM, tick Tools > MCP Bridge > Allow MCP control, and click Yes when DWSIM asks to allow Claude's connection. Then ask Claude to open or build a simulation.

Try asking Claude, for example:

Open examples\02_water_ethanol_nrtl_splitter.dwxmz, show me the stream table in engineering units, then compare NRTL, Wilson and Raoult's Law for the mixer outlet temperature.

Create a new simulation with methanol and water using NRTL, add a feed at its bubble point at 1 atm with 30 mol% methanol, and tell me the temperature.

If you move this folder or reinstall Python, run setup.ps1 again (the extender only accepts the exact Python + server.py it was built for). Close DWSIM and Claude Desktop before re-running it.

Folder contents

Live mode (DWSIM window) vs background mode

The MCP server can drive simulations two ways:

• Live -- if DWSIM is running with the MCP Bridge extender (dwsim_plugin/), open_simulation opens the file in that DWSIM window (or reuses it if it's already open) and every change -- added, connected or deleted objects, property edits, solves -- appears on screen immediately. No closing and reopening.

• Background -- otherwise, a hidden copy of DWSIM is used, as before. You only see changes after save_simulation and reopening the file.

open_simulation(file_path, mode="auto") picks live when available; pass mode="live" or mode="background" to force one. list_dwsim_windows shows what's open in the DWSIM window.

Installing the MCP Bridge extender

powershell -ExecutionPolicy Bypass -File dwsim_plugin\build_plugin.ps1

This compiles MCPBridge.cs, CompoundTools.cs and FlowsheetTools.cs with the .NET Framework compiler that ships with Windows and copies DWSIM.Extensions.MCPBridge.dll (plus its allow-list, see below) into DWSIM's extenders folder (DWSIM only loads files named *Extensions*.dll from there). Restart DWSIM.

The same DLL also provides the compound and flowsheet tools in background mode, so the MCP server loads it too. Rebuild with both DWSIM and the Claude app closed -- the DLL is locked while either is using it.

Switching live control on and off

Live control is off every time DWSIM starts. Tick Tools > MCP Bridge > Allow MCP control to let Claude edit the window; the item reads "Allow MCP control (ON)" with a check mark while it's on. Click it again (or close DWSIM) to switch it off -- open connections are dropped immediately and the session key is deleted. While it's off, the MCP tools fall back to background mode.

Security model

• No network port. The bridge uses a Windows named pipe, so web pages can't reach it. The pipe's access list admits only your Windows account and explicitly denies network logons; its name is random each session.

• Per-session secret key. Switching control on creates a random key in %LOCALAPPDATA%\DWSIM_MCPBridge\session.json, readable only by your account. Every connection must answer a random challenge with HMAC-SHA256 of that key; the key itself is never sent over the pipe.

• Server check. The MCP server only talks to the pipe if it is served by the DWSIM.exe process that wrote the session file.

• Client check. DWSIM only accepts connections from the interpreter and script listed in extenders\DWSIM.Extensions.MCPBridge.allowed.json (your python.exe + this server.py, written by setup.ps1 / build_plugin.ps1). Anything else is refused before the key check, without a prompt. Re-run build_plugin.ps1 if you move Python or this folder.

• Your approval. The first time the MCP server connects after you switch control on, DWSIM asks "allow connection?" and shows the program, script and process ID. Approval lasts for that server process until you switch control off; a restarted Claude app asks again.

• Residual risk: malware already running under your own Windows account can't be fully stopped (it could inject into DWSIM or edit its files directly), but it would now need control to be on, to impersonate the allowed program, and to get past a prompt you'd notice.

What it can do

Property codes are DWSIM-internal identifiers, documented at https://dwsim.org/wiki/index.php?title=Object_Property_Codes. Handy ones: PROP_MS_0 temperature (K), PROP_MS_1 pressure (Pa), PROP_MS_2 mass flow (kg/s), PROP_MS_3 molar flow (mol/s), PROP_MS_102/<compound> mole fraction of a compound, SR1, SR2, ... splitter split fractions.

Building and reporting a simulation

New simulations. new_simulation(file_path, compounds, property_package) creates a flowsheet with exact database compound names (or CAS numbers) and a model, saves it, and opens it (live if MCP control is on). Then add objects with add_object, specify feeds with set_stream, and solve.

Thermodynamic models. list_property_packages shows what each object uses. add_property_package(model="NRTL", assign_to_all=True) adds a model and switches every stream and unit operation to it; partial names work if unambiguous ("Raoult", "Peng-Robinson (PR)"). Activity models load DWSIM's interaction-parameter database automatically; check them with get_interaction_parameters and override with set_interaction_parameters (12/21 follow the order you give; NRTL/UNIQUAC energies in cal/mol, EOS kij dimensionless). Always solve again after changing models.

Model choice matters. For 50/50 mol ethanol–water at 1 atm, NRTL gives a bubble point of 79.8 °C (matches data) while Raoult's Law gives 87.1 °C. DWSIM 9.0.5's built-in UNIQUAC parameters for methanol–water behave worse than ideal (bubble point 85 °C vs ~78 °C measured; NRTL, Wilson and UNIFAC agree with data) -- check parameters before trusting a model on a new mixture. NRTL parameters fitted to VLE data also don't reproduce heats of mixing well, so treat adiabatic mixing temperatures with care.

Stream specification. set_stream sets everything in one call. Each quantity is a plain SI number or a string with units:

• temperature: K, C, F, R (e.g. "25 C")

• pressure: Pa, kPa, MPa, bar, barg, mbar, atm, psi(a), psig, mmHg

• mass flow: kg/s, kg/h, t/h, t/d, lb/h, g/s ...

• molar flow: mol/s, kmol/h, lbmol/h ...

• volumetric flow: m3/s, m3/h, L/min, gpm, bbl/d ...

Give two of temperature, pressure and vapor_fraction (0 = bubble point, 1 = dew point) and at most one flow. composition takes any scale and is normalised (composition_basis = "mole" or "mass"); unlisted compounds are set to zero.

Results. stream_table returns every stream's conditions, flows, vapour fraction, enthalpy, density and compositions in one call (units = "engineering" (default: °C, bar, kg/h, kmol/h, m3/h), "SI" or "field"; include_phases=True adds per-phase compositions). export_results writes the same data as a classic stream table (one column per stream) to .csv or a formatted .xlsx.

Unit operations, reactions, diagnostics and studies

Unit-operation settings. get_unit_settings(object) lists every setting with its English name (e.g. a heater's PROP_HT_2 = "Outlet Temperature"), SI unit, current value and whether it's writable, plus the calculation modes and their allowed values (e.g. a heater's CalcMode: HeatAdded, OutletTemperature, OutletVaporFraction, TemperatureChange...). set_unit_settings takes several at once, by code, name or mode, with units: {"CalcMode": "OutletTemperature", "Outlet Temperature": "80 C"}. Temperature settings whose name reads like a difference (rise, drop, delta...) treat "10 C" as 10 K.

Reactions. add_reaction defines a reaction and files it in a reaction set (created on demand); reactor= points a reactor at that set.

• type="conversion" + conversion="60" (% of the base compound, or an expression in T) -- for RCT_Conversion.

• type="equilibrium" + optional ln_keq="..." in T; without it, Keq(T) comes from Gibbs energies of formation -- for RCT_Equilibrium.

• type="kinetic" + A_forward, E_forward (J/mol), optional reverse terms and orders (default: stoichiometric) -- for RCT_CSTR / RCT_PFR.

Reactor ports: inlet 0 = feed, inlet 1 = energy stream; conversion and equilibrium reactors have outlet 0 = vapour, 1 = liquid. Set the reactor's mode (Isothermic, Adiabatic, OutletTemperature...) with set_unit_settings.

Diagnostics. diagnose_flowsheet reports problems found now (unconnected inlets/outlets, feeds without flow or composition, reactors without reactions, missing compounds or packages) and errors from the last solve (labelled as such -- they clear on the next successful solve). calculate_flowsheet adds the failing objects and these issues to its result automatically whenever something fails.

Sensitivity studies. run_sensitivity varies one property (values=[...] or start/stop/steps, with units) and records outputs given as "Object:PROPERTY", e.g. ["Out:PROP_MS_0", "Mixture:PROP_MS_102/Ethanol"]. The input is restored and the flowsheet re-solved afterwards; export_file writes .csv/.xlsx.

Model comparison. compare_property_packages(models=[...], outputs=[...]) solves the flowsheet under each model in turn and tabulates the outputs, then restores the original model assignments and removes the temporary packages. Example (30 mol% methanol in water, bubble point at 1 atm): NRTL 77.9 °C, Wilson 77.7 °C, UNIFAC 78.2 °C, Raoult 84.0 °C, UNIQUAC 85.0 °C (measured ≈ 78 °C).

Compounds

Database compounds. search_compounds looks through DWSIM's ~1,500 built-in compounds (ChemSep, ChEDL, CoolProp, ...) plus anything installed in addcomps. add_compound adds one to the simulation and to every existing stream with zero amount -- set feed compositions afterwards with PROP_MS_102/<compound>. remove_compound takes it out again and renormalises the affected streams (a stream that contained only that compound is flagged as needing a new composition).

Custom compounds (create_compound). Units: molar mass g/mol, Tc K, Pc Pa, Tb K, Vc m3/kmol, formation energies kJ/mol.

• Required: molar_mass, tc, pc, and acentric_factor or tb (the acentric factor is then estimated with Lee-Kesler). zc/vc are estimated (Pitzer) if missing.

• Vapour pressure: estimated from Tc, Pc and the acentric factor (Lee-Kesler) -- typically within a few percent near the boiling point.

• Ideal-gas heat capacity is needed for energy balances. Give one of:

  • cp_ig_coefficients: [A, B, C, D, E] for Cp = A + B·T + C·T² + D·T³ + E·T⁴ in J/(kmol·K) (DWSIM equation 5);

  • cp_ig_points: [[T_K, Cp_J_per_mol_K], ...], fitted to that polynomial (up to 4th order);

  • cp_from: an existing compound whose Cp correlation is copied.

• based_on: start from a full copy of an existing compound and override only what you give (useful for isomers and variants).

• The result lists every estimate made and warns about anything missing.

Online import. search_online_compounds + import_online_compound use DWSIM's Cheméo connector (internet required). Cheméo supplies critical constants, acentric factor, boiling point, formation energies and identifiers but no ideal-gas Cp correlation, so pass Cp the same way as for custom compounds. source="kdb" is accepted, but DWSIM 9.0.5's KDB connector points at a server address that no longer responds.

Files. export_compound writes a DWSIM compound .json; import_compound_file loads one into another simulation (optionally under a new name). install_compound copies it into DWSIM's addcomps folder so it appears in every simulation and in DWSIM's own compound list after DWSIM is restarted (it won't overwrite an existing file unless overwrite=true). Compounds used in a simulation are also saved inside its .dwxmz, so they travel with the file.

Manual setup (what setup.ps1 does)

1. pip install -r requirements.txt

2. python scripts\find_dwsim.py -- confirms DWSIM is found and its engine loads. If it isn't found, set DWSIM_PATH to the DWSIM folder.

3. With DWSIM closed: powershell -ExecutionPolicy Bypass -File dwsim_plugin\build_plugin.ps1 -PythonExe <python.exe> -ServerScript <this folder>\server.py

4. python scripts\configure_claude.py -- or edit %APPDATA%\Claude\claude_desktop_config.json yourself:

   {
     "mcpServers": {
       "dwsim": {
         "command": "C:\\full\\path\\to\\python.exe",
         "args": ["C:\\full\\path\\to\\dwsim_9.0.5_mcp\\server.py"]
       }
     }
   }

   Use full absolute paths for both; a bare "python" often isn't found when Claude Desktop launches it. Claude Code instead: claude mcp add dwsim -- <python.exe> <path>\server.py.

5. Fully quit and reopen Claude Desktop.

Troubleshooting

• ModuleNotFoundError: No module named 'mcp.server.fastmcp' -- your installed mcp package is 2.x, which renamed FastMCP to MCPServer (this code already uses the new name/import). Just re-run pip install -r requirements.txt to make sure the version pin took.

• "MCP dwsim: Server disconnected" in Claude Desktop, but python server.py runs fine directly in a terminal -- almost always the command path issue above (use the full path to python.exe, not just "python"). If it still fails, click "View logs" in Claude Desktop's Local MCP servers panel for the actual error.

• "No method matches given arguments" on LoadFlowsheet -- version mismatch between Automation3 and what your DWSIM build actually ships. Check whether your DWSIM version uses Automation2 instead, and swap it in dwsim_bridge.py if so.

• COM/threading errors on startup -- confirm pywin32 installed (pip install pywin32); the bridge calls pythoncom.CoInitialize() before loading DWSIM's assemblies, which needs it.

• list_object_properties raises a "PropertyType enum" error -- see _property_type_enum() in dwsim_bridge.py; add the real namespace from DWSIM's API docs if neither candidate resolves.

• A DLL fails to load -- confirm DWSIM_PATH points at a complete install (the folder should contain all the .dll files alongside DWSIM.Automation.dll), not a partial copy.

• "MCP control is switched off in DWSIM" -- tick Tools > MCP Bridge > Allow MCP control in DWSIM, or open the file with mode="background".

• "Connection refused by DWSIM: ... not the configured MCP server" -- Python or this folder moved since build_plugin.ps1 last ran. Close DWSIM and the Claude app and run it again.

• "The installed MCP Bridge DLL is out of date" -- the compound tools need the current DLL. Close DWSIM and the Claude app, run build_plugin.ps1, reopen both.

• build_plugin.ps1 can't overwrite the DLL -- DWSIM or the MCP server (i.e. the Claude app) still has it loaded; close both first.

• Cheméo lookups fail -- check internet access; the connector needs TLS 1.2+, which the tools enable automatically.

• Console noise from DWSIM (Ipopt banners, "Estimated NRTL IP set...") -- the server redirects all of DWSIM's console output to stderr at startup so it can't corrupt the MCP message stream on stdout. If you see it in Claude Desktop's MCP log, that's expected and harmless.

Sharing your own simulations

DWSIM saves the file's full path (including your Windows user name), the author as COMPUTER\user, and a log of the last session inside every .dwxmz. Before posting a simulation publicly (e.g. with a bug report):

python scripts\sanitize_dwxmz.py path\to\simulation.dwxmz

Reporting problems

Open an issue using the bug template; it asks for your Windows, DWSIM and Python versions and the output of python scripts\find_dwsim.py. Security issues: please follow SECURITY.md instead of opening a public issue.

Licence

This project is released under the MIT Licence.

DWSIM itself is a separate program licensed under the GNU GPL v3 and is not included here; this project only calls its public APIs and builds an extender against the DWSIM you install. MIT-licensed code is GPL-compatible, but if you redistribute the built extender together with DWSIM, DWSIM's GPL terms apply to that combined distribution.