Task Log

Purpose: Persistent memory across sessions. Every solved task gets an entry here so future sessions can find prior solutions instead of starting from scratch.

How to use: Search this file for keywords before starting a new task. If a similar task was solved before, start from that solution.

Entry Format

### YYYY-MM-DD — Short task title
**Type:** A (Property) | B (Process) | C (PVT) | D (Standards) | E (Feature) | F (Design) | G (Workflow)
**Keywords:** comma, separated, search, terms
**Solution:** Where the code lives (test file, notebook, source file)
**Notes:** Key decisions, gotchas, or results worth remembering

Privacy Rule

Task log entries are public/reusable memory. Do not include company/operator names, field/facility/asset names, equipment tag numbers, internal document names, private system names, access diagnostics, or task folder slugs containing those details. Use generic descriptors such as confidential offshore gas platform, private task folder (redacted), operator-specific technical requirement, or confidential compressor route.

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Log

2026-05-08 — Safety-system barrier performance analyzer

Type: E (Feature) / G (Workflow) Keywords: safety critical systems, barrier performance, major accident risk, deluge, firewater, fire gas detection, passive fire protection, SIS voting, STID, performance standards Solution: src/main/java/neqsim/process/safety/barrier/SafetySystemPerformanceAnalyzer.java; tests in src/test/java/neqsim/process/safety/barrier/SafetySystemPerformanceAnalyzerTest.java Notes: Added an analyzer that bridges the existing BarrierRegister, FireDetector/GasDetector, and neqsim.process.logic.sis.SafetyInstrumentedFunction models. Reusable lesson: assess active/passive safety-system barriers as a reporting layer over existing evidence, instruments, and SIS logic instead of creating parallel detector or SIF abstractions.

2026-05-08 — Recompressor barrier verification technical safety screen

Type: F (Design) / G (Workflow) Keywords: barrier verification, technical safety, closed flare, recompressor, HAZOP, FMEA, LOPA, bow-tie, risk matrix, STID, tagreader Solution: private task folder (redacted) Notes: Completed a separate barrier and technical-safety screening study using prior NeqSim source-term results and STID/tagreader evidence requirements. Reusable lesson: current barrier credit should be withheld until status, effectiveness, independence, proof-test/SRS evidence, event replay, and material/MDMT records are verified; conditional IPL credit can close most scenarios, while low-temperature material verification remains a distinct close-out.

2026-05-08 — Closed-flare recompressor blowdown verification screen

Type: F (Design) / G (Workflow) Keywords: closed flare, recompressor, blowdown, trapped inventory, depressurization, MDMT, flare load, tagreader, STID, technical safety Solution: private task folder (redacted); reusable code in src/main/java/neqsim/process/safety/inventory/TrappedInventoryCalculator.java; tests in src/test/java/neqsim/process/safety/inventory/TrappedInventoryCalculatorTest.java Notes: Reused a private, consistency-checked recompressor inventory and dynamic blowdown source-term task, screened transient flare load versus documented capacity context, and generated Word/HTML report outputs. Added TrappedInventoryCalculator to bridge documented equipment/pipe volume evidence to NeqSim blowdown inputs. Reusable lesson: distinguish small transient blowdown loads from sustained closed-flare/recompression operating margin, and treat low blowdown temperatures as an MDMT follow-up until material/wall data are verified.

2026-05-07 — Confidential gas precompression inlet velocity screen

Type: B (Process) / G (Workflow) Keywords: STID, tagreader, P&ID, pressure drop, gas velocity, scrubber, compressor suction, Word report, PipeBeggsAndBrills Solution: private task folder (redacted) Notes: Retrieved route P&IDs and equipment design documents from STID, extracted line/nozzle diameters, read 24-hour historian averages with tagreader, used NeqSim gas properties plus a PipeBeggsAndBrills straight-pipe check, and generated a Word report. Reusable lesson: reject inconsistent historian unit metadata, document the adopted flow-unit interpretation, and separate measured route pressure loss from straight-pipe friction and local equipment/minor losses.

2026-05-07 — Confidential STID UniSim power extraction

Type: B (Process) / G (Workflow) Keywords: STID, UniSim, HYSYS, process simulation, total power, compressor duty, document retrieval Solution: private task folder (redacted) Notes: Searched multiple installation scopes for the newest runnable .usc case, inspected zip attachments before selecting the latest case file, ran the selected UniSim case through COM, and reported total mechanical power as compressor plus pump duty. Reusable pattern: keep STID identifiers and asset-specific power values private, while recording the selection and power-accounting method publicly.

2026-05-06 — Confidential separator carry-over cooler scaling screen

Type: B (Process) / G (Workflow) Keywords: separator carry-over, cooler scaling, anti-surge recycle, STID, tagreader, NaCl source term, compressor calibration, plate heat exchanger Solution: private task folder (redacted) Notes: Built a NeqSim gas-path screening model from separator gas outlet through a suction cooler, scrubber, and recompressor with measured fixed anti-surge recycle. STID and tagreader manifests were kept in the private task folder. Reusable pattern: model anti-surge recycle as a measured stream when compressor maps are unavailable, then evaluate NaCl risk first as a water carry-over source term and halite saturation threshold before claiming a deposition/fouling rate.

2026-04-29 — Route-level piping hydraulic builder for STID line lists

Type: E (Feature) / G (Workflow) Keywords: PipingRouteBuilder, STID, E3D, line list, piping route, pressure drop, PipeBeggsAndBrills, fittings, K-value, equivalent length Solution: src/main/java/neqsim/process/equipment/pipeline/routing/PipingRouteBuilder.java, src/test/java/neqsim/process/equipment/pipeline/routing/PipingRouteBuilderTest.java, docs/process/piping_route_builder.md Notes: Added a high-level builder that converts serial line-list rows with from/to nodes, pipe length, hydraulic diameter, wall thickness, roughness, elevation change, and fitting/valve K values into a ProcessSystem of Beggs-and-Brill pipe segments. Future STID/E3D/P&ID hydraulic tasks should extract route rows first, then use PipingRouteBuilder instead of hand-assembling pipe units; export route.toJson() for traceability and reuse.

2026-04-28 — Confidential upstream compressor pressure-drop analysis

Type: B (Process) Keywords: upstream compressor, precompression, pressure drop, STID, tagreader, piping hydraulics, separator outlet, scrubber, route hydraulics, debottlenecking Solution: private task folder (redacted) Notes: STID P&IDs/stress isometrics and a saved pressure workbook were combined with NeqSim PR gas properties and Darcy/K-value hydraulics. Base model pressure drop matched the plant snapshot within about 0.1 bar. Main reusable lesson: extract serial route rows first, preserve private source references only inside the task folder, and keep public logs to generic route-pressure-drop decisions and method choices.

2026-04-21 — Confidential scrubber performance deliverable

Type: F (Design) / G (Workflow) Keywords: scrubber, GasScrubberMechanicalDesign, operator-specific conformity, ConformityReport, mesh pad, demisting cyclones, inlet momentum, k-factor, historic peak Solution:

• private task folder (redacted) — multi-case conformity runs + reference-style tables + Excel/HTML export
• Docs: docs/process/equipment/separators.md — new section “Gas Scrubber Mechanical Design and Conformity Checking” with Java+Python workflow, multi-case screening pattern, and usage constraints
• Test: DocExamplesCompilationTest#testGasScrubberConformityCheckDoc verifies the documented API path end-to-end Notes:
• Multi-case reference-style table generation covered normal and historic peak cases; incomplete private tag history was excluded from the public summary.
• Output layout mirrors a vendor-style reference spreadsheet without logging vendor file names or internal document IDs.
• Operator-specific conformity outcomes were summarized privately; public reusable lesson is to define a new ConformityRuleSet subclass instead of modifying existing limits.
• Efficiency and carry-over rows are deferred — table schema already reserves placeholder rows

2026-07-04 — Compressor Sealing

Type: B (Process) Keywords: bics, components, compressor, connected, equipment, flow, floating production, model, pr78 Solution: private task folder (redacted) Notes: The unified NeqSim model replicates a confidential floating production process in a single connected ProcessSystem. Public log keeps only reusable modeling lessons; asset-specific validation metrics remain in the private task folder.

2026-04-16 — Confidential full process model with plant data integration

Type: B (Process) Keywords: compression, converged, data, full process, plant data integration, liquid recycle, recycle convergence Solution: private task folder (redacted) Notes: A confidential full process model with recycles converged. Scrubber liquids were recycled to appropriate separation stages and parallel train behavior was modeled explicitly. Exact asset names and performance figures are kept in the private task folder.

2026-04-16 — CO2 injection hydrogen accumulation in wells

Type: B (Process) Keywords: accumulation, hydrogen, injection, wells, CO2, CCS Solution: private task folder (redacted) Notes: Task folder created; analysis in progress.

2026-04-16 — CO2 injection hydrogen accumulation risk assessment

Type: B (Process) Keywords: accumulation, assessment, bara, classic, component, conditions, critical, dense, drops, equation Solution: private task folder (redacted) Notes: The confidential CO2 injection well case operates safely in dense single phase under the screened normal operating envelope.

2026-04-13 — Elemental sulfur deposition in gas turbine fuel

Type: B (Process) Keywords: approximately, assumed, causes, cooling, deposition, drop, elemental sulfur, fuel gas Solution: private task folder (redacted) Notes: NeqSim thermodynamic modelling showed a low-temperature S8 deposition risk for an assumed confidential fuel-gas case. Public log retains only the reusable JT-cooling and sulfur-solidification workflow.

2026-04-13 — FLNG feedgas process design and analysis

Type: F (Design) Keywords: achieved, amine, benzene, both, case, cases, comp, component, design, essentially Solution: task_solve/2026-04-13_flng_feedgas_process_design_and_analysis/step2_analysis/01_flng_process.ipynb Notes: 1. CO2 removal to 50 ppm achieved for both Lean and Rich cases via amine unit (modelled as component splitter). 2.

2026-04-10 — Crude oil blending into export blend

Type: B (Process) Keywords: blend, blending, crude, decreases, e300, exceed, fluid, fraction, gravity Solution: private task folder (redacted) Notes: The confidential crude blend API gravity decreases monotonically with increasing heavy-stream fraction. Public log keeps the reusable interpolation and specification-screening method; exact stream names are private.

2026-04-10 — Out of Zone Injection - NeqSim Implementation Discussion

Type: E (Feature) Keywords: discussion, implementation, injection, zone Solution: task_solve/2026-04-10_out_of_zone_injection_neqsim_implementation_discussion/ Notes: Task folder created; analysis in progress.

2026-04-09 — MIMEE NeqSim Code Review - Methane Emissions

Type: E (Feature) Keywords: code, emissions, methane, mimee, review Solution: task_solve/2026-04-09_mimee_neqsim_code_review_methane_emissions/step2_analysis/01_reference_implementation.ipynb, task_solve/2026-04-09_mimee_neqsim_code_review_methane_emissions/step2_analysis/02_detailed_method_comparison.ipynb, task_solve/2026-04-09_mimee_neqsim_code_review_methane_emissions/step2_analysis/04_gas_composition_sensitivity.ipynb Notes: Key results: deviation average percent: 38.0; deviation range percent: 8.4% to 80.1%; offshore norge equivalent temp C: 60-65; crossover temp C: ~40; neqsim factor at 20C g per m3 bar: 25.21.

2026-04-08 — Condensation UniSim NeqSim comparison

Type: D (Standards) Keywords: characterization, comparison, component, components, compositions, condensation, e300, feed Solution: private task folder (redacted) Notes: The E300 import successfully reproduces the UniSim 31-component fluid characterization in NeqSim. Molecular weights match to within 0.3% for all 12 streams tested (feed, gas, oil compositions). The feed flash vapour fraction differs by 3.

2026-04-08 — R510 SG condensation UniSim to NeqSim conversion

Type: B (Process) Keywords: condensation, conversion, r510, unisim Solution: task_solve/2026-04-08_r510_sg_condensation_unisim_to_neqsim_conversion/step2_analysis/01_unisim_neqsim_comparison.ipynb Notes: Task folder created; analysis in progress.

2026-04-08 — Early phase sprint paper

Type: B (Process) Keywords: early, paper, phase, sprint, field development Solution: private task folder (redacted) Notes: Task folder created; analysis in progress.

2026-04-07 — Compressor dry gas seal condensation analysis

Type: B (Process) Keywords: alkane, caused, causes, components, compressor, condensation, continuous, dry gas seal, envelope Solution: private task folder (redacted) Notes: A confidential dry gas seal case identified two condensation mechanisms. Public log keeps only the reusable phase-envelope, JT expansion, and seal-gas workflow; equipment tags and exact pressures remain private.

2026-04-07 — Injection compressor dry gas seal failure analysis

Type: B (Process) Keywords: compressor, failure, injection, seal, dry gas seal Solution: private task folder (redacted) Notes: Task folder created; analysis in progress.

2026-04-06 — Advanced Electrolyte EOS Development and Scientific Paper

Type: A (Property) Keywords: advanced, average, calculation, corrected, counter, cross, development, dilution, discovered, electrolyte Solution: task_solve/2026-04-06_advanced_electrolyte_eos_development_and_scientific_paper/step2_analysis/01_electrolyte_model_comparison.ipynb Notes: Discovered fundamental reference state bug in getActivityCoefficient(k): counter-ions retained in reference, weakening DH ~3x. Corrected 2-arg calculation reduces average MAE from 16.9% to 4.2%. Cross-ion Cl- W0 consistency improved from 6x to 1.

2026-04-06 — TEG Dehydration Sizing for 50 MMSCFD Wet Gas

Type: B (Process) Keywords: dehydration, mmscfd, sizing Solution: task_solve/2026-04-06_teg_dehydration_sizing_for_50_mmscfd_wet_gas/step2_analysis/01_TEG_dehydration_sizing.ipynb Notes: Task folder created; analysis in progress.

2026-04-05 — Wax Formation Models Comparison and Improvement

Type: D (Standards) Keywords: comparison, formation, improvement, models Solution: task_solve/2026-04-05_wax_formation_models_comparison_and_improvement/ Notes: Task folder created; analysis in progress.

2026-03-30 — NeqSim Library Review - High Impact Fixes and Updates

Type: E (Feature) Keywords: fixes, high, impact, library, review, updates Solution: task_solve/2026-03-30_neqsim_library_review_high_impact_fixes_and_updates/ Notes: Task folder created; analysis in progress.

2026-03-27 — Hydrogen blending in export gas quality analysis

Type: B (Process) Keywords: binding, blending, compositions, constraint, density, export, fraction, hydrogen, index, lean Solution: private task folder (redacted) Notes: Relative density — not the Wobbe index — is the binding constraint for H2 blending in the screened export-gas cases. Lean gas tolerates lower H2 addition than medium or rich gas before violating EN 16726 relative-density limits.

2026-03-27 — Process model from existing simulator

Type: B (Process) Keywords: compression, compressors, condensate, existing simulator, export, feed, model Solution: private task folder (redacted) Notes: The confidential process model runs successfully in NeqSim with PR EOS. Public log keeps the reusable simulator-conversion and compression-train workflow, while asset names and exact capacities remain private.

2026-03-26 — CO2 injection hydrogen accumulation in wells

Type: B (Process) Keywords: accumulation, bara, bulk, component, enrichment, factors, hydrogen, injection, mixing, phase Solution: private task folder (redacted) Notes: Hydrogen accumulation in the gas phase is a REAL thermodynamic phenomenon. At T=4 C the two-phase region spans 42-58 bara. H2 enrichment factors reach 5-8x (3.9-5.9 mol% H2 in gas vs 0.75% in bulk). K_H2 = 11.9 at 50 bara.

2026-03-24 — NeqSim Pseudo-Component Characterization Documentation

Type: E (Feature) Keywords: characterization, component, documentation, pseudo Solution: task_solve/2026-03-24_neqsim_pseudo_component_characterization_documentation/ Notes: Task folder created; analysis in progress.

2026-03-24 — Probabilistic NPV Monte Carlo analysis

Type: G (Workflow) Keywords: analytical, appraisal, carlo, field, function, influential, model, monte, musd Solution: private task folder (redacted) Notes: A confidential field NPV study used Monte Carlo and value-of-information screening. Public log keeps the reusable economic workflow; field name, exact valuation figures, and recommendations remain private.

2026-03-23 — FLNG Class A Concept Study Offshore Tanzania 3000m

Type: G (Workflow) Keywords: benchmarks, c3mr, capex, challenges, class, concept, contr, depth, economic, faces Solution: task_solve/2026-03-23_flng_class_a_concept_study_offshore_tanzania_3000m/step2_analysis/01_reservoir_fluid_pvt.ipynb, task_solve/2026-03-23_flng_class_a_concept_study_offshore_tanzania_3000m/step2_analysis/02_flng_process_simulation.ipynb, task_solve/2026-03-23_flng_class_a_concept_study_offshore_tanzania_3000m/step2_analysis/03_capex_economics.ipynb Notes: The FLNG Tanzania concept at 3000m water depth faces significant economic challenges. Total CAPEX of $6201M ($1772/tonne) is at the upper end of FLNG benchmarks.

2026-03-23 — CO2 injection hydrogen accumulation analysis

Type: B (Process) Keywords: accumulation, beckm, concern, confirmed, cross, engineering, feasibility, four, gerg, hydrogen Solution: private task folder (redacted) Notes: Hydrogen accumulation in the gas phase is a confirmed engineering concern for the confidential CO2 injection case, validated by four independent EOS models and cross-referenced with private feasibility-study findings.

2026-03-21 — compressor_train_analysis

Type: B (Process) Keywords: above, assessed, baseline, booster, capex, compressor, compressordesignfeasibilityreport, extends, feasibility Solution: private task folder (redacted) Notes: The booster compressor + precooler installation screened as feasible for a confidential production case. Public log keeps only the reusable compressor-feasibility workflow; asset name and exact economic uplift remain private.

2026-03-20 — H2 properties data comparison

Type: D (Standards) Keywords: aard, agrees, closely, compared, comparison, data, densitometer, density, enhanced, experimental Solution: task_solve/2026-03-20_h2_properties_data_comparison/step2_analysis/01_h2_density_comparison.ipynb Notes: Overall AARD: REFPROP=1.8408%, NeqSim Std GERG-2008=2.0790%, NeqSim GERG-2008-H2=2.2120%, NeqSim SRK=1.9948%. NeqSim standard GERG-2008 agrees closely with REFPROP (AARD=0.6221%).

2026-03-19 — Utsira Nord Floating Wind Class A Concept Study

Type: G (Workflow) Keywords: class, commercial, concept, cost, costs, current, farm, floati, floating, foundation Solution: task_solve/2026-03-19_utsira_nord_floating_wind_class_a_concept_study/step2_analysis/01_design_basis_and_site.ipynb, task_solve/2026-03-19_utsira_nord_floating_wind_class_a_concept_study/step2_analysis/02_wind_resource_and_aep.ipynb, task_solve/2026-03-19_utsira_nord_floating_wind_class_a_concept_study/step2_analysis/03_electrical_system_design.ipynb Notes: The project LCOE of ~2141 NOK/MWh (202 EUR/MWh) reflects the pre-commercial cost level of floating offshore wind. At current costs, the project requires substantial government CfD/subsidy support (~2000 NOK/MWh) to achieve economic viability.

2026-03-18 — umoe_composites_300bar_cng_tank_filling_temperature

Type: B (Process) Keywords: approximately, classic, composites, filling, hours, lean, limit, maximum, methane, mixing Solution: task_solve/2026-03-18_umoe_composites_300bar_cng_tank_filling_temperature/step2_analysis/01_filling_simulation.ipynb, task_solve/2026-03-18_umoe_composites_300bar_cng_tank_filling_temperature/step2_analysis/02_literature_review.ipynb, task_solve/2026-03-18_umoe_composites_300bar_cng_tank_filling_temperature/step2_analysis/03_benchmark_validation.ipynb Notes: Filling the Umoe Composites 300 bar Type IV tank from 20.0 to 300.0 bar at 247.5 Sm3/day takes approximately 52 hours. The maximum gas temperature reaches 31.0 C, which is within the ISO 11119-3 limit of 85.0 C with a margin of 54.0 C.

2026-03-12 — turboexpander modification evaluation for future operation

Type: B (Process) Keywords: across, barg, below, class, declining, decreases, drops, evaluation, feasible, future Solution: task_solve/2026-03-12_turboexpander_modification_evaluation_for_future_operation/step2_analysis/01_tex_performance.ipynb, task_solve/2026-03-12_turboexpander_modification_evaluation_for_future_operation/step2_analysis/02_seal_gas_condensation.ipynb, task_solve/2026-03-12_turboexpander_modification_evaluation_for_future_operation/step2_analysis/03_uncertainty_risk.ipynb Notes: TEX PERFORMANCE: Feasible 2025-2029 (inlet P > 48 barg). Infeasible from 2030 when pressure ratio drops below ~1.05. Speed DECREASES from ~6950 to ~4500 rpm — no overspeed risk. TEX provides 5-8 degC advantage over JT valve through 2029.

2026-03-11 — TPG4230 Field Development and Operations Learning Material

Type: G (Workflow) Keywords: aspects, assurance, chain, characterization, complete, compress, course, covering, covers, design Solution: task_solve/2026-03-11_tpg4230_field_development_and_operations_learning_material/step2_analysis/Module_01_Introduction_and_Value_Chain.ipynb, task_solve/2026-03-11_tpg4230_field_development_and_operations_learning_material/step2_analysis/Module_02_Flow_Performance.ipynb, task_solve/2026-03-11_tpg4230_field_development_and_operations_learning_material/step2_analysis/Module_03_Oil_Gas_Processing.ipynb Notes: The learning material covers all key aspects of field development: reservoir fluid characterization, production flow performance, oil and gas processing, flow assurance, separator design, gas compression and pipeline hydraulics, production scheduling…

2026-03-07 — Ultima Thule Field Development - Class A Study

Type: G (Workflow) Keywords: class, development, field, study, thule, ultima Solution: task_solve/2026-03-07_UltimaThule_ClassA_study/ Notes: Task folder created; analysis in progress.

2025-07-24 — Process Optimization Enhancements: NIP-03, NIP-06, NIP-08, NIP-09 Implementation

Type: E (Feature) Keywords: process optimization, rate-based absorber, SQP optimizer, multiphase flow, Hagedorn-Brown, Mukherjee-Brill, multi-variable adjuster, Onda correlation, Billet-Schultes, mass transfer, enhancement factor, damped successive substitution Solution: src/main/java/neqsim/process/equipment/absorber/RateBasedAbsorber.java, src/main/java/neqsim/process/util/optimizer/SQPoptimizer.java, src/main/java/neqsim/process/equipment/pipeline/PipeHagedornBrown.java, src/main/java/neqsim/process/equipment/pipeline/PipeMukherjeeAndBrill.java, examples/notebooks/process_optimization_enhancements.ipynb Notes: Implemented four NIPs from process optimization review. NIP-06: RateBasedAbsorber with Onda 1968 and Billet-Schultes 1999 mass transfer correlations, Hatta/Van Krevelen enhancement factors (6 tests). NIP-08: SQPoptimizer with active-set SQP for constrained process optimization (5 tests). NIP-03: PipeHagedornBrown and PipeMukherjeeAndBrill multiphase flow correlations (8 tests). NIP-09: MultiVariableAdjuster convergence fix — replaced Broyden accelerator with damped successive substitution (α=0.1) after Broyden caused oscillation/divergence due to wrong Jacobian sign. All 23 tests pass. Docs updated: absorbers.md, sqp_optimizer.md, multiphase_flow_correlations.md, adjusters.md, CHANGELOG_AGENT_NOTES.md.

2026-04-17 — cDFT Surface Tension: Kernel Correction, Mixture Extension, Paper

Type: E (Feature) Keywords: cDFT, surface tension, interfacial tension, density functional theory, kernel range, mixture IFT, Peng-Robinson, SRK, predictive, lambda correlation, acentric factor, critical correction, Miqueu, gradient theory, Parachor, Fluid Phase Equilibria Solution: src/main/java/neqsim/thermo/util/LCSF/surfacetension/CDFTSurfaceTension.java, task_solve/2026-04-17_cdft_surface_tension_paper_kernel_correction_and_mixture_extension/, neqsim-paperlab/papers/cdft_surface_tension_2026/ Notes: Implemented predictive cDFT surface tension from cubic EOS. Three proposals: (A) kernel range correction λ(ω) = 0.749 − 0.740ω reduces AAD from 41.5% to 9.5% for 8 pure components (beats GT 12.8%, Parachor 17.6%; Miqueu GT 2.2% still best). (B) Mixture solver with shared-δ tanh profiles and cross kernels achieves 37.6% AAD for CH4/C3H8 at 277.6K (vs 61.7% Parachor). (C) Paper manuscript for Fluid Phase Equilibria with 4 figures, 3 tables. 27+ tests across 6 test classes. Key insight: critical exponent correction (1−Tr)^(−0.24) essential near Tc.

2026-04-18 — Systematic “hardcoded phase 0” bug elimination in two-phase flow

Type: E (Feature/Bugfix) Keywords: two-phase flow, mass transfer, heat transfer, friction factor, Reynolds number, velocity, phase index, interphase transport, Krishna-Standart, film model, non-equilibrium, pipeline condensation, stratified flow, slug flow, droplet flow, stirred cell Solution: src/main/java/neqsim/fluidmechanics/flownode/ (multiple files across 3 rounds) Notes: Found and fixed 29 bugs across 3 audit rounds. Root cause: methods accepting int phase/int phaseNum parameters internally called getReynoldsNumber(), getVelocity(), or calcWallFrictionFactor(0, node) without passing the phase index through. These default to phase 0 (gas), making liquid-phase (1) calculations use incorrect gas-phase Reynolds numbers, velocities, and friction factors. Fixed files: NonEquilibriumFluidBoundary, ReactiveKrishnaStandartFilmModel, KrishnaStandartFilmModel, TwoPhaseFixedStaggeredGridSolver, InterphaseStratifiedFlow, TwoPhaseFlowNode, InterphaseDropletFlow, InterphaseSlugFlow, InterphaseTransportCoefficientBaseClass, MultiPhaseFlowNode, InterphasePipeFlow, InterphaseStirredCellFlow. Also added NaN guards, divide-by-zero protections, convergence fixes, and dead code cleanup. All fluidmechanics tests pass.

2026-06-18 — TwoFluidPipe transient & pressure gradient benchmark and fixes

Type: E (Feature) Keywords: TwoFluidPipe, transient, multiphase, two-fluid model, pressure gradient, benchmark, McAdams viscosity, Beggs Brill, holdup, friction factor, Haaland, pipeline Solution: src/main/java/neqsim/process/equipment/pipeline/TwoFluidPipe.java, src/test/java/neqsim/process/equipment/pipeline/TwoFluidPipeBenchmarkTest.java Notes: Fixed transient inlet BC override (isTransientMode flag), outlet pressure capture bug, improved viscosity model (McAdams quality-based harmonic averaging). Added 19 benchmark tests in 8 categories validating against PipeBeggsAndBrills and literature. Single-phase gas ratio 0.98, two-phase GLR sweep 0.81–1.33, vertical riser gravity 1.04 bar matches ρgH, D⁻⁵ diameter scaling ratio 33.7. Transient holdup evolution 0.19→0.09 after flow step-change now works correctly.

2026-03-14 — Fix IEC 60534 gas valve sizing: use standard volumetric flow (issue #1918)

Type: D (Standards) Keywords: valve sizing, IEC 60534, Cv, Kv, gas valve, standard flow, actual flow, control valve, throttling valve, choked flow, N9 Solution: src/main/java/neqsim/process/mechanicaldesign/valve/ControlValveSizing_IEC_60534.java, src/main/java/neqsim/process/mechanicaldesign/valve/ControlValveSizing_IEC_60534_full.java, src/test/java/neqsim/process/mechanicaldesign/valve/ControlValveSizingTest.java Notes: Gas valve Cv was severely underestimated (~98% too low at 50 bara) because IEC 60534 equation was applied with actual volumetric flow instead of standard volumetric flow (273.15 K, 101.325 kPa). Fix: convert Q_actual to Q_std = Q_actual × (P₁/P_std) × (T_std/T₁) / Z before applying the IEC formula. Fixed in sizeControlValveGas(), calculateFlowRateFromKvAndValveOpeningGas(), and calculateValveOpeningFromFlowRateGas() in both base and _full classes. Added regression test matching Python fluids library result (Cv ≈ 16.2 for 10000 kg/hr methane at 50 bara). Liquid valves were not affected.

2026-03-10 — Process architecture improvements: stream introspection, named controllers, connections, unified elements

Type: E (Feature) Keywords: architecture, ProcessElementInterface, ProcessConnection, MultiPortEquipment, getInletStreams, getOutletStreams, controller map, named controllers, runTransient, controller scan, getAllElements, DEXPI, topology, stream introspection, connections Solution: src/main/java/neqsim/process/ProcessElementInterface.java, src/main/java/neqsim/process/equipment/MultiPortEquipment.java, src/main/java/neqsim/process/processmodel/ProcessConnection.java, src/main/java/neqsim/process/equipment/ProcessEquipmentInterface.java, src/main/java/neqsim/process/equipment/ProcessEquipmentBaseClass.java, src/test/java/neqsim/process/processmodel/ProcessArchitectureTest.java Notes: Six backward-compatible architecture improvements motivated by DEXPI integration friction. (1) Stream introspection: getInletStreams()/getOutletStreams() on ProcessEquipmentInterface with default empty lists; overridden in TwoPortEquipment, Separator, ThreePhaseSeparator, Mixer, Splitter — all return unmodifiable lists. (2) Named controller map: addController(tag, ctrl), getController(tag), getControllers() on ProcessEquipmentBaseClass alongside legacy setController(). (3) ProcessElementInterface: unified marker extending NamedInterface + Serializable; adopted by ProcessEquipmentInterface, MeasurementDeviceInterface, ControllerDeviceInterface. (4) Controller scan in runTransient: explicit loop over system-level controllerDevices after equipment loop. (5) ProcessConnection: typed connection metadata (MATERIAL/ENERGY/SIGNAL) with ProcessSystem.connect() and getConnections(). (6) MultiPortEquipment: abstract base class for multi-inlet/outlet equipment. 173 tests passing (14 architecture + 42 DEXPI + 117 core process). Documentation updated in process_system.md, extending_process_equipment.md, controllers.md, dynamic_simulation_guide.md, CODE_PATTERNS.md, CONTEXT.md.

2026-03-10 — DEXPI review: multi-outlet nozzles, stream identity matching, namespace support

Type: E (Feature) Keywords: DEXPI, multi-outlet, nozzle, separator, stream identity, connection, pass-through, namespace, absorber, stripper, column subtype, instrument rename, DexpiStreamUtils, DexpiXmlWriter, DexpiEquipmentFactory, DexpiSimulationBuilder Solution: src/main/java/neqsim/process/processmodel/dexpi/DexpiStreamUtils.java, src/main/java/neqsim/process/processmodel/dexpi/DexpiXmlWriter.java, src/main/java/neqsim/process/processmodel/dexpi/DexpiEquipmentFactory.java, src/main/java/neqsim/process/processmodel/dexpi/DexpiSimulationBuilder.java, src/main/java/neqsim/process/processmodel/dexpi/DexpiXmlReader.java Notes: Implemented all 11 recommendations from DEXPI code review. (1) DexpiStreamUtils: shared outlet-stream resolution utility replacing duplicated reflection-based code. (2) Reflection removal: outlet access via TwoPortEquipment/Separator casts instead of Method.invoke. (3) Multi-outlet nozzles: writer creates 2 outlet nozzles for Separator, 3 for ThreePhaseSeparator. (4) Stream identity matching: connections built by matching System.identityHashCode of inlet/outlet streams; registerPassThroughStreams handles wrapper Streams that delegate getFluid(). (5) Column subtype: DexpiEquipmentFactory detects “absorb”/”strip” in DEXPI class to configure condenser/reboiler flags. (6) Namespace-aware parsing: setNamespaceAware(boolean) on builder and reader. (7) Instrument renaming: applyAutoInstrumentation now calls setName() on transmitters and controllers (ControllerDeviceBaseClass cast). 4 new tests (cyclic topology, multi-outlet separator, 2 round-trip profile); 68 tests total, all passing.

2026-03-10 — DEXPI round-trip export, cycle detection, and column support

Type: E (Feature) Keywords: DEXPI, P&ID, round-trip, export, XML writer, connection, nozzle, reverse mapping, cycle detection, distillation column, simulation results, instrument wiring, DexpiXmlWriter, DexpiXmlWriterTest Solution: src/main/java/neqsim/process/processmodel/dexpi/DexpiXmlWriter.java, src/test/java/neqsim/process/processmodel/dexpi/DexpiXmlWriterTest.java, src/main/java/neqsim/process/processmodel/dexpi/DexpiTopologyResolver.java, src/main/java/neqsim/process/processmodel/dexpi/DexpiEquipmentFactory.java, src/main/java/neqsim/process/processmodel/dexpi/DexpiSimulationBuilder.java Notes: Completed 7 round-trip (DEXPI↔NeqSim) improvements. DexpiXmlWriter gains Connection/Nozzle export (buildConnections, appendNozzle, appendConnectionSystem), native equipment reverse mapping (reverseMapComponentClass maps Separator→VesselForStorage, Compressor→CompressorUnit, etc.), and simulation results export (appendSimulationResults writes temperature/pressure/flow as GenericAttributes). DexpiTopologyResolver gains hasCycle() via DFS-based detection. DexpiEquipmentFactory gains createColumn() for DistillationColumn instantiation with NumberOfTrays and FeedTray sizing attributes. DexpiSimulationBuilder instrument tag wiring replaced setName() calls with logging-based tag association (ControllerDeviceInterface/MeasurementDeviceInterface lack setName). Fixed instanceof ordering bug: Cooler extends Heater, so Cooler must be checked before Heater in reverseMapComponentClass. 15 new tests (11 in DexpiXmlWriterTest, 2 cycle-detection, 2 column-creation); 64 tests total, all passing.

2026-03-10 — DEXPI topology resolver, equipment factory, and simulation builder

Type: E (Feature) Keywords: DEXPI, P&ID, topology, nozzle, connection, equipment factory, simulation builder, mapping loader, sizing, DexpiTopologyResolver, DexpiEquipmentFactory, DexpiSimulationBuilder, DexpiMappingLoader, GenericAttribute, Kahn, topological sort Solution: src/main/java/neqsim/process/processmodel/dexpi/DexpiTopologyResolver.java, src/main/java/neqsim/process/processmodel/dexpi/DexpiEquipmentFactory.java, src/main/java/neqsim/process/processmodel/dexpi/DexpiSimulationBuilder.java, src/main/java/neqsim/process/processmodel/dexpi/DexpiMappingLoader.java Notes: Resolved 7 critical gaps in DEXPI implementation. DexpiTopologyResolver parses Nozzle/Connection/Equipment XML elements into a directed graph, collapses inline piping components (valves, reducers) to equipment-level edges, and produces topological ordering via Kahn’s algorithm. DexpiEquipmentFactory converts DexpiProcessUnit placeholders to real NeqSim equipment (Separator, Compressor, Pump, HeatExchanger, Heater, Cooler, Valve, Expander, Mixer, Splitter) with sizing attributes applied. DexpiSimulationBuilder is a fluent builder API: setFluidTemplate/setFeedPressure/setFeedTemperature/setFeedFlowRate/setAutoInstrument → build() returns runnable ProcessSystem. DexpiMappingLoader provides thread-safe cached loading of .properties mapping files from classpath. DexpiMetadata expanded with 10 sizing constants. DexpiProcessUnit gains sizingAttributes map and dexpiId. Equipment mapping expanded from ~30 to ~65 entries; piping component mapping from ~15 to ~28. 49 tests across 7 test classes (all passing).

2026-03-10 — DynamicProcessHelper utility for steady-state to dynamic conversion

Type: E (Feature) Keywords: dynamic, transient, simulation, DynamicProcessHelper, transmitter, PID, controller, instrument, auto-instrument, pressure, level, flow, temperature, control loop, PC, LC, FC, TC, runTransient, setCalculateSteadyState Solution: src/main/java/neqsim/process/util/DynamicProcessHelper.java, src/test/java/neqsim/process/util/DynamicProcessHelperTest.java, docs/process/dynamic-simulation.md Notes: Utility that converts a sized steady-state ProcessSystem into a dynamic simulation. Auto-creates transmitters (PT, LT, TT) and PID controllers (PC, LC, WLC) by scanning equipment and matching stream identity to downstream valves. Handles Separator, ThreePhaseSeparator, Compressor, Heater, Cooler. Convenience methods for addFlowController() and addTemperatureController(). Default PID tuning with per-type customization. Key gotcha: transmitters implement MeasurementDeviceInterface (NOT ProcessEquipmentInterface), so ProcessSystem.add(MeasurementDeviceInterface) must be used. 10 tests passing.

2026-03-10 — Implement InstrumentDesign framework

Type: E (Feature) Keywords: instrument, design, ISA, SIL, I/O, DCS, SIS, instrumentation, ISA-5.1, IEC 61508, IEC 61511, API 670, safety, compressor, separator, heat exchanger, pipeline, valve, tag number, cabinet sizing, cost estimation Solution: src/main/java/neqsim/process/instrumentdesign/ Notes: Mirrors ElectricalDesign pattern. Base class InstrumentDesign with InstrumentSpecification (ISA-5.1 data sheets) and InstrumentList (I/O counting, cost aggregation, tag generation). Equipment-specific designs for separator (PT×2 + PSH + TT + LT×2 + LSH + LSLL + ZT×2; three-phase adds interface LT + water ZT), compressor (API 617/670 suite: ~18 instruments including VT×4 vibration probes, anti-surge FT/FCV, bearing TTs, lube oil PT/PSLL), heat exchanger (auto-detects shell-and-tube/air cooler/electric heater), pipeline (pig detection ZS×2, leak detection PSLL, metering FT), and valve (ZT + ZC; safety valves add XV + ZSO/ZSC). System-level SystemInstrumentDesign aggregates across ProcessSystem and sizes DCS (~16 ch/card, ~16 cards/cab), SIS (~8 ch/card, ~8 cards/cab), and marshalling cabinets. Integrated via ProcessEquipmentInterface.getInstrumentDesign() and ProcessSystem.getSystemInstrumentDesign(). 12 tests passing.

2026-03-09 — H₂S/CO₂ Distribution Between Gas, Oil, Water — EOS Model Comparison

Type: A (Property) Keywords: H2S, CO2, acid gas, distribution, solubility, water, oil, gas, produced water, brine, salinity, SRK, PR, CPA, electrolyte CPA, chemical reactions, three-phase, salting-out, pH, NACE MR0175, sour service, model selection, decision matrix, Duan Sun, Carroll Mather, Soreide Whitson, Monte Carlo, benchmark Solution: task_solve/2026-03-09_h2s_co2_distribution_gas_oil_water_produced_water_eos_comparison/ Notes: Systematic comparison of 4 EOS models (SRK, PR, SRK-CPA, Electrolyte-CPA) across 10 scenarios for acid gas partitioning. Critical findings: (1) SRK/PR give near-zero CO₂ solubility in water — unsuitable for acid gas-water systems; (2) Only Electrolyte-CPA correctly predicts three phases (gas/oil/aqueous); (3) chemicalReactionInit() is mandatory for pH, salting-out, and ionic speciation; (4) H₂S shows retrograde solubility (max 60-70°C); (5) Water content is dominant sensitivity (1.42% swing in Monte Carlo). Benchmark: 5/5 tests PASS (13.8-25.0% deviation vs Duan & Sun 2003, Carroll & Mather 1991). Monte Carlo N=300: H₂S aqueous P10/P50/P90 = 0.51/0.92/1.35%. Decision matrix maps 12 applications to recommended models. 6 NIPs proposed (acid gas report, produced water builder, pH calculator, salting-out DB, compliance checker, model advisor).

2026-03-09 — CO2 Corrosion Analyzer with Electrolyte CPA pH

Type: E (Feature) Keywords: corrosion, CO2, pH, electrolyte CPA, de Waard-Milliams, NORSOK M-506, chemical reaction equilibrium, H3O+, carbonic acid, HCO3-, CCS, pipeline, corrosion rate, scale, FeCO3, inhibitor, brine, NaCl, severity, aqueous speciation Solution: src/main/java/neqsim/pvtsimulation/flowassurance/CO2CorrosionAnalyzer.java, src/test/java/neqsim/pvtsimulation/flowassurance/CO2CorrosionAnalyzerTest.java, examples/notebooks/CO2_Corrosion_Analysis_ElectrolyteCPA.ipynb Notes: Facade class coupling electrolyte CPA EOS (SystemElectrolyteCPAstatoil) with de Waard-Milliams corrosion model and ScalePredictionCalculator. Key insight: must call chemicalReactionInit() → createDatabase(true) → setMixingRule(10) → init(0) to enable aqueous chemical equilibrium (CO2 + 2H2O → HCO3- + H3O+). Without this, pH returns 7.0 (no H3O+ component). The analyzer auto-creates the electrolyte system, runs flash with chemical reactions, extracts rigorous pH from H3O+ activity, and feeds it into the corrosion model. Supports temperature/pressure sweeps, brine (Na+/Cl-), inhibitor efficiency, and JSON reporting. 12/12 tests passing.

2026-03-09 — Water Solubility in Gas and Liquid CO2 Phase Behaviour

Type: A (Property) Keywords: water, solubility, CO2, CPA, SRK, PR, equation of state, phase equilibrium, CCS, carbon capture, dehydration, pipeline, gas phase, liquid phase, supercritical, mutual solubility, Wiebe, Gaddy, Bamberger, Spycher, King, Song, Kobayashi, benchmark, validation, ISO 27913, ppmv, water content Solution: task_solve/2026-03-09_water_solubility_in_gas_and_liquid_co2_phase_behaviour/ Notes: Investigated water solubility in CO2 across gas, liquid, and supercritical conditions (5-200 bar, 10-80 C) using CPA EOS (SystemSrkCPAstatoil, mixing rule 10). Key findings: gas-phase water content decreases with pressure (Raoult’s law dilution), liquid CO2 has low solubility (1000-3000 ppmv), characteristic minimum at CO2 saturation pressure. Benchmark: 9/13 points within 30% tolerance, mean error 25.2%. CPA under-predicts at 60 C (40-50% error vs Bamberger data). CPA outperforms SRK/PR at high pressures. Monte Carlo (N=300): P10/P50/P90 = 2986/3616/4253 ppmv for CCS conditions — dehydration always required (100% exceed 500 ppmv ISO limit). Tornado: EOS model uncertainty dominates (1729 ppmv swing), then pressure (1068), then temperature (945). Overall risk: Medium (2 high, 3 medium, 2 low).

2026-03-09 — Sulfur Deposition Analysis

Type: B (Process) Keywords: sulfur, S8, deposition, desublimation, Joule-Thomson, JT cooling, backflow, letdown, valve, H2S, pressure reduction, solid flash, GibbsReactor, SulfurDepositionAnalyser, preheating, mitigation Solution: private task folder (redacted) Notes: Analysed elemental sulfur deposition in a backflow letdown system (70→15 bara). JT cooling gives ~-20°C outlet (JT coeff 0.46-0.58 K/bar). 100% of Monte Carlo scenarios (N=300) produce solid S8. Primary mechanism is desublimation, not chemical reaction. Air ingress (O2) contributes via H2S oxidation at Gibbs equilibrium. Preheating helps but S8 solid persists even at 100°C preheat with >0.01 ppb S8 feed. Used SRK EOS, ThrottlingValve, TPSolidflash, GibbsReactor, SulfurDepositionAnalyser. 9/9 benchmarks PASS (JT coefficients within 15%, S8 solubility within literature order-of-magnitude). Overall risk: High (5 high, 4 medium, 1 low risks).

2026-03-08 — Mercury Removal in LNG Pre-Treatment — NeqSim Chemisorption Model

Type: B (Process), F (Design) Keywords: mercury, Hg, removal, guard bed, chemisorption, CuS, sorbent, adsorber, NTU, Ergun, packed bed, LNG, pre-treatment, mass transfer zone, breakthrough, transient, bed lifetime, mechanical design, ASME VIII, cost estimation, CAPEX, OPEX, sorbent replacement, fuel gas strategy Solution: src/main/java/neqsim/process/equipment/adsorber/MercuryRemovalBed.java, src/test/java/neqsim/process/equipment/adsorber/MercuryRemovalBedTest.java, task_solve/2026-03-08_mercury_removal_lng_pretreatment/ Notes:

• MercuryRemovalBed: NTU-based steady-state + cell-by-cell transient PDE (upwind scheme, CFL sub-stepping), Ergun pressure drop, Arrhenius kinetics, bypass/degradation, bed lifetime estimation
• MercuryRemovalMechanicalDesign: ASME VIII Div 1, SA-516-70, hoop stress wall thickness, weight breakdown, BOM
• MercuryRemovalCostEstimate: Factored CAPEX (PEC→BMC→TMC→GRC), sorbent replacement OPEX
• 24/24 unit tests passing covering construction, steady-state, transient, degradation, lifetime, JSON, mechdesign, cost
• Benchmark validated against analytical NTU formula, hand-calculated Ergun dP, literature bed lifetime (Carnell 2007, Eckersley 2010)
• Monte Carlo 250 iterations with full NeqSim simulation per iteration; tornado on 6 uncertain parameters

2026-03-08 — NeqSim-based Monte Carlo uncertainty and risk evaluation for NPV

Type: G (Workflow) Keywords: uncertainty, Monte Carlo, risk, NPV, GIP, resource estimate, tornado, sensitivity, ISO 31000, risk matrix, NeqSim simulation, SRK EOS, SimpleReservoir, Beggs & Brill, SURFCostEstimator, triangular distribution, P10 P50 P90, field development Solution: task_solve/2026-03-07_npv_calculation_of_field_development_subsea_tieback/step2_analysis/03_uncertainty_risk_analysis.ipynb, step3_report/generate_report.py (Sections 9-10) Notes:

• Full NeqSim process simulation (SRK EOS, SimpleReservoir, WellFlow, Beggs & Brill pipeline) in every Monte Carlo iteration
• 7 uncertain parameters: GIP volume (0.65-1.45 GSm3), reservoir pressure (120-170 bara), plateau rate (7-12 MSm3/d), gas price, CAPEX multiplier, OPEX, discount rate
• N=200 iterations, ~5.5 min total runtime with full NeqSim re-simulation per iteration
• Results: P10=-22, P50=3,352, P90=7,086 MNOK; P(NPV<0)=10.5%
• Resource estimate uncertainty: GIP P10=105, P50=135, P90=169 GSm3; Recovery P10=45%, P50=57%, P90=66%
• Tornado: gas price is dominant driver (swing 10,990 MNOK), followed by discount rate (5,744) and plateau rate (3,833)
• Risk register: 8 risks across Market/Technical/Cost/Schedule/HSE/Regulatory, overall: High
• Report generator updated with Sections 9 (Uncertainty Analysis) and 10 (Risk Evaluation) — auto-populated from results.json
• Updated AGENTS.md and copilot-instructions.md to make uncertainty/risk MANDATORY for all AI tasks

2026-03-04 — Sulfur deposition and corrosion analysis system

Type: E (Feature) Keywords: sulfur, S8, H2S, deposition, precipitation, solubility, Gibbs reactor, Claus, FeS, corrosion, NACE, sour gas, solid flash, TPSolidflash, SulfurDepositionAnalyser, GibbsReactor, SO2, pipeline, subsea, onshore Solution: src/main/java/neqsim/process/equipment/reactor/SulfurDepositionAnalyser.java, src/test/java/neqsim/process/equipment/reactor/SulfurDepositionAnalyserTest.java, examples/sulfurtask/SulfurDepositionAnalysis.ipynb, docs/chemicalreactions/sulfur_deposition_analysis.md Notes:

• New SulfurDepositionAnalyser unit operation combining Gibbs equilibrium, TP-solid flash, temperature sweep, and corrosion assessment in a single run()
• Added FeS, Fe2O3, FeS2 species to GibbsReactDatabase.csv
• Corrosion module: NACE MR0175 sour severity classification, FeS/SO2/H2SO4 risk assessment
• Temperature sweep identifies sulfur deposition onset temperature
• 6 tests passing (solubility, equilibrium, corrosion, full analysis, edge cases, JSON output)
• Jupyter notebook (15 sections): solubility maps, saturation envelope, Gibbs reactor sweeps, O2/H2S sensitivity, pipeline simulation, onshore processing risk, H2S sensitivity
• Uses neqsim_dev_setup for notebook JVM bootstrap

2026-03-07 — CNG tank filling and emptying temperature estimation (workflow test)

Type: B (Process) Keywords: CNG, tank, filling, emptying, depressurization, pressurization, temperature, wall temperature, MDMT, heat transfer, transient wall, VesselDepressurization, X80 steel, energy balance, Churchill-Chu, natural convection Solution: task_solve/2026-03-07_cng_tank_filling_and_emptying_temperature_estimation/step2_analysis/CNG_Tank_Temperature_Estimation.ipynb Notes:

• Full end-to-end test of solve.task workflow: task creation, scope/research, simulation notebook, results.json, Word+HTML reports
• Tank: 19m height, 1.066m OD, 33.5mm wall (X80 steel), vertical with hemispheric caps
• Gas: lean natural gas (90% CH4, 5% C2, 2% C3, 0.5% iC4, 0.5% nC4, 1% N2, 1% CO2), SRK EOS
• Filling: 20→250 bar at 1783.4 Sm3/day, duration 51.2 hr, max gas T = 31.0°C
• Emptying: 250→20 bar at 1783.4 Sm3/day, duration 50.8 hr, min gas T = 1.4°C, min wall T = 2.0°C
• MDMT check: margin 48.0°C above -46°C, PASS
• HTC model comparison: ADIABATIC min T = -91.7°C, CALCULATED = 1.7°C, TRANSIENT_WALL = 1.4°C
• No liquid dropout during emptying
• dt=10s constant for VU-flash stability, recordInterval=60 (every 10 min)
• Report auto-generated from results.json + task_spec.md via generate_report.py

2025-07-17 — CNG tank temperature estimation improvements and Jupyter notebooks

Type: E (Feature) Keywords: CNG, tank, filling, emptying, depressurization, VU-flash, heat transfer, Churchill-Chu, Gnielinski, natural convection, mixed convection, transient wall, VesselDepressurization, temperature estimation, MDMT Solution: src/main/java/neqsim/process/equipment/tank/VesselDepressurization.java, examples/CNGtankmodelling/CNG_FillingSimulation.ipynb, examples/CNGtankmodelling/CNG_EmptyingSimulation.ipynb, examples/CNGtankmodelling/CNG_GasProperties_HTC.ipynb Notes:

• 6 Java improvements to VesselDepressurization: fixed flow rate filling, filling energy balance with VU-flash, external HTC (Churchill-Chu + Gnielinski), target pressure control, hemispheric geometry, mole-scaling fix
• Bug fixes: (1) Cp*1000 in 3 HTC methods inflated coefficients 1000x, (2) OptimizedVUflash static variables contaminating between calls, (3) temperature guards for non-physical VU-flash results
• Critical finding: VU-flash convergence fails when dt switches from 10s to 60s at low pressure — use constant dt=10s
• Filling: 20→250 bar in 52 hr, gas T: 15→30°C, no liquid dropout
• Emptying: 250→20 bar in 57 hr, min gas T: -0.4°C, MDMT check passed (-46°C margin)
• Ambient sensitivity: even at -20°C ambient, min wall T = -34.4°C (above MDMT)
• HT model comparison: ADIABATIC=-94°C, CALCULATED=+9°C, TRANSIENT_WALL=-0.4°C
• Cp notebook bug: getMolarMass() returns kg/mol, so * 1000 in Cp conversion was wrong (same root cause as Java Cp*1000 bug)
• 41 unit tests passing, devtools workflow used (target/classes, no JAR packaging)

2026-03-01 — Well mechanical design and cost estimation system

Type: F (Design) Keywords: well, subsea, casing, tubing, mechanical design, NORSOK D-010, API 5CT, cost estimation, drilling, completion, barrier verification, WellMechanicalDesign, WellDesignCalculator, WellCostEstimator Solution: src/main/java/neqsim/process/mechanicaldesign/subsea/WellMechanicalDesign.java, WellDesignCalculator.java, WellCostEstimator.java, src/test/java/.../WellMechanicalDesignTest.java Notes:

• SubseaWell was the only subsea equipment type WITHOUT a mechanical design class
• Added WellType, CompletionType, RigType enums to SubseaWell
• Three-layer pattern: SubseaWell → WellMechanicalDesign → WellDesignCalculator + WellCostEstimator
• Casing design: burst/collapse/tension per API Bull 5C3, supports 14 casing grades (H40 through 25Cr)
• Well barrier verification per NORSOK D-010 two-barrier principle
• Cost estimation with regional factors (Norway 1.35x, GOM 1.0x, etc.)
• Wired into FieldDevelopmentCostEstimator via setWellParameters()
• CSV data files: WellCostData.csv, CasingProperties.csv
• 21 tests all passing
• Documentation: docs/process/well_mechanical_design.md

2026-03-01 — Task log and context system created

Type: E (Feature) Keywords: context, documentation, workflow, onboarding, task-solving Solution: CONTEXT.md, docs/development/TASK_SOLVING_GUIDE.md, docs/development/TASK_LOG.md Notes: Created a 3-file context system to make repo-based task solving faster:

• CONTEXT.md — 60-second orientation (repo map, patterns, constraints)
• TASK_SOLVING_GUIDE.md — workflow for classifying and solving tasks
• TASK_LOG.md — this file, persistent memory across sessions

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2026-03-10 — Electrical design: equipment-specific classes and system integration

Type: E (Feature) Keywords: electrical design, separator, heater, cooler, pipeline, heat tracing, cathodic protection, system electrical design, load list, transformer sizing, emergency generator Solution: src/main/java/neqsim/process/electricaldesign/separator/SeparatorElectricalDesign.java, heatexchanger/HeatExchangerElectricalDesign.java, pipeline/PipelineElectricalDesign.java, system/SystemElectricalDesign.java Notes:

• Implemented electrical design phases 2-3.
• SeparatorElectricalDesign: models control valves, instrumentation, lighting, optional heat tracing (no shaft power)
• HeatExchangerElectricalDesign: auto-detects type (ELECTRIC_HEATER / AIR_COOLER / SHELL_AND_TUBE) from equipment class
• PipelineElectricalDesign: heat tracing (W/m × length), cathodic protection, instrumentation
• SystemElectricalDesign: plant-wide aggregation with utility/UPS loads, main transformer and emergency generator sizing
• Integrated into Separator (eager init), Heater/Cooler (lazy init), AdiabaticPipe and PipeBeggsAndBrills (lazy init)
• Added ProcessSystem.getSystemElectricalDesign() for one-call plant electrical summary
• 24 unit tests all passing in ElectricalDesignTest

2026-04-16 — Review Dynamic Process and Control Functionality

Type: G (Workflow) Keywords: dynamic simulation, transient, PID controller, MPC, HYSYS Dynamics, K-Spice, safety chain, HIPPS, ESD, blowdown, VU-flash, DynamicProcessHelper, ProcessEventBus, alarm, runTransient, control, measurement device, valve, split-range, override, bumpless transfer, sequence control, SFC, distillation dynamics, heat exchanger dynamics, rotor inertia Solution: task_solve/2026-04-16_review_dynamic_process_and_control_functionality/step1_scope_and_research/analysis.md Notes: Comprehensive 45-feature comparison across 7 categories against 5 commercial simulators. NeqSim scores 63/90 (70%) vs HYSYS 79/90 (88%). Leads in 8 areas (VU-flash, safety chain, Monte Carlo risk, auto-instrumentation, water hammer, DEXPI export, event bus, specialised analysers). 10 NIPs proposed with 4-phase roadmap. Key gaps: explicit Euler only (no implicit/adaptive), no dynamic HX/column, no bumpless transfer, no split-range/override, no sequence control.

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