PHAST Modelling for Hydrogen Leakage

Hydrogen Pipeline Leakage Dispersion Study 1. Objective Perform consequence modelling in PHAST to determine the downwind distance to the lower flammability limit (LFL = 4% v/v) for high-pressure hydrogen pipeline leak scenarios. Results will be used as reference data for simplified model development and comparison. 2. Modelling Approach • Software: PHAST (latest available version) • Release type: Continuous gaseous release • Release model: Orifice leak from pressurized pipeline • Flow regime: Determined by PHAST (choked flow expected) • Terrain: Flat, open terrain, no obstacles • Release height: Ground level (H = 0 m) • Release direction: Vertical • Surface roughness: 0.1 m • Gas: Hydrogen (100%) • Gas temperature: 298 K • Relative humidity: 50% 3. Scenario Matrix Pipeline diameter: • 500 mm • 900 mm • 1200 mm Operating pressure: • 5 MPa • 8 MPa • 10 MPa Leak diameter (circular hole): • 1 mm • 3 mm • 6 mm • 12 mm Meteorological conditions: • Case M1: 1.5 m/s, stability class F • Case M2: 3.0 m/s, stability class D • Case M3: 5.0 m/s, stability class D Total scenarios: 108 4. Release Assumptions • Continuous steady-state release (no blowdown modelling) • Infinite supply assumption (no inventory depletion) • Pipeline treated as pressurized source, not full rupture • Discharge coefficient: PHAST default • No obstacle or terrain effects 5. Output Requirements Primary result (for each scenario): • Maximum downwind distance to LFL (4% v/v), m o Based on centreline concentration at 1.5 m height Additional outputs: • Mass flow rate at release (kg/s) • Exit velocity (m/s) • Cloud height at LFL distance (if available) 6. Visual Outputs Provide for each scenario or agreed representative subset: • Concentration contour plot with LFL boundary (4%) • Side view (plume profile) • Top view (dispersion footprint) Requirements: • Clear distance scale • LFL contour indicated • Scenario ID shown 7. Data and Model Files Provide full reproducibility package: • PHAST project files (.psu or equivalent) • All input files • Exported calculation outputs 8. Data Format Excel table including: • Scenario ID • Pipeline diameter • Pressure • Leak size • Meteorology case • Mass flow rate • LFL distance 9. Deliverables • Excel dataset • PHAST model files • Plot package (images) • Short technical note (1–2 pages) describing setup

Project ID: 40406636