Choupo

Choupo is a free and open-source chemical process simulator for chemical engineering education, research and exploratory process design. It combines a C++17 calculation engine with a browser-based interface, allowing users to run simulations without installing software, creating an account or paying a licence fee.

The defining feature of Choupo is its glass-box approach: instead of only displaying final results, it makes models, input data, numerical methods, iterations and material and energy balances available for inspection. Users can investigate how an answer was obtained and assess the assumptions behind it.

The simulator supports steady-state flowsheets with recycle streams, batch and transient processes, feedback control and thermophysical property calculations. Its models include phase equilibrium and flash calculations, distillation, absorption, chemical reactors (CSTR, PFR and Gibbs), heat exchangers, pumps, compressors, adsorption, crystallisation, drying, nanofiltration and reverse osmosis. Parameter studies, optimisation, property fitting and preliminary equipment or cost calculations are also available.

Choupo includes runnable tutorials, integrated process examples and interactive EduTools that connect engineering theory with calculations performed by the simulation engine. Students can examine individual unit operations, while more advanced users can explore interconnected flowsheets and process-design trade-offs.

Simulation cases are defined through readable text dictionaries, separating process configuration, property models and initial conditions. This supports reproducibility, version control and AI-assisted case preparation. Documentation, model catalogues and automated regression checks help users assess model behaviour and track numerical changes.

The underlying source code is published under the GPL-3.0-or-later licence. The browser application executes the calculation engine locally through WebAssembly; the engine can also be built from source for native execution.

Choupo is intended for learning, investigation and research. It is not certified for safety-critical or industrial design decisions, which require independent validation.