The NeqSim Web project is a web user interface for the neqsim process simulator.
The application is in initial development and is using the streamlit framework.
The application is hosted by streamlit and can be tested at neqsim web app link.
The Pipeline page provides two native NeqSim calculation paths:
- Steady-State (Beggs-Brill) uses
PipeBeggsAndBrillsfor liquid holdup, flow regime, friction, hydrostatic pressure change, thermodynamics, and optional specified-U heat transfer. The app solves inlet pressure to match the requested outlet pressure and reports NeqSim's native increment profiles. - Dynamic Simulation (Two-Fluid Model) uses
TwoFluidPipefor separate gas and liquid conservation equations, terrain, heat transfer, flow-regime transitions, and optional slug tracking. A converged native steady state is used to initialize the transient calculation.
Both paths use the same normalized fluid table. The page starts with a lean natural-gas preset and also provides a two-phase gas-condensate regression fluid and a blank custom fluid. SRK is the explicit default thermodynamic model; PR, CPA, and NeqSim automatic model selection are available in the sidebar. Standard gas rate is interpreted at 1.01325 bara and 15 °C; actual volume rate uses the entered pressure and temperature. Pressures are absolute unless a result is explicitly labelled as a pressure drop.
Terrain distances must be strictly increasing. The dynamic page shifts the first distance to zero and interpolates absolute elevations at the native two-fluid section centres. Zero mass flow is rejected before the Java model is called. Results are intended for engineering screening and require model validity, discretization, and time-step sensitivity checks before project use.
Process Flowsheet Studio builds and solves reusable steady-state NeqSim cases from shared fluid packages, independent inlet streams, unit operations, and explicit material or energy connections.
Enable an equipment design basis in a pump, two-sided heat exchanger, valve, or pipeline to compare its solved operating point with explicit capacities. The Workbook · Design view reports operating value, capacity, margin, utilization, status, and engineering unit in a normalized table. Pipeline rows also identify the critical native velocity-profile segment and length when the NeqSim unit exposes that profile.
The downloadable engineering workbook contains the same review-ready data in the Equipment Design worksheet together with streams, equipment, constraints, convergence, and conservation evidence. These results support screening and engineering studies; they are not design certification.
Schema v4 adds execution-neutral subflowsheets on top of the authoritative flat process graph. A subflowsheet owns a non-overlapping set of units and declares every material or energy port used where a connection crosses its boundary. Terminal product ports may also be exposed explicitly. Studio validates these contracts during import, draft history, execution planning, and solve readiness; the draft diagram renders each group as a labeled dashed container and lists its boundary-port mappings. Schema-v1–v3 cases migrate to v4 with an empty subflowsheet list, so existing calculations remain unchanged.
Studio runs each native flowsheet build, convergence pass, mixer-energy closure, design rerun, and final solve within one 180-second execution budget. Workers that exceed the budget are interrupted or abandoned after a bounded cancellation wait, and failed or timed-out native models are discarded instead of being published as solved results. Timeout classification survives normal Streamlit reruns while the last trustworthy result stays hidden.
The current UniSim-parity assessment and production-readiness gaps are tracked in docs/process_flowsheet_unisim_parity.md.