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Simulation of the efficiency of hydrogen recombiners as safety devices. Ernst-Arndt Reinecke, Stephan Kelm, Wilfried Jahn, Christian Jäkel, Hans-Josef Allelein. International Conference on Hydrogen Safety September 12-14, 2011, San Francisco, CA. Overview.

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Simulation of the efficiency of hydrogen recombiners as safety devices

Simulation of the efficiency of hydrogen recombiners as safety devices

Ernst-Arndt Reinecke, Stephan Kelm, Wilfried Jahn, Christian Jäkel, Hans-Josef Allelein

International Conference on Hydrogen Safety

September 12-14, 2011, San Francisco, CA


Overview
Overview safety devices

Simulation of the efficiency of hydrogen recombiners as safety devices

  • Passive auto-catalytic recombiner (PAR)

  • Goal of the numerical study

  • Scenario investigated

  • Model approach

  • Results


Unintended h 2 release inside confined space
Unintended H safety devices2 release inside confined space



Commercial pars in nuclear power plants
Commercial PARs in Nuclear Power Plants safety devices

Vendors

  • AECL, Canada

  • AREVA, France/Germany

  • NIS, Germany

Source: Siempelkamp


Operational boundary conditions
Operational boundary conditions safety devices

NPP containment

  • large temperature and density gradients

  • large natural convection loops

  • large geometry (20,000-70,000 m³, typical length scales 5-50 m)

  • steam-inertized in early accident phase

    Typical H2 and FC applications

  • significant smaller scales

  • different thermal hydraulic conditions

PAR applicability ?

NPP

H2 & FC

GOAL:


Scenario safety devices


Experiment
Experiment safety devices

Source: CEA

  • GARAGE facility at CEA/France

  • single vehicle private garage (~40 m³)

  • concentration measurement at ~60 pos.

    Test 1: He release (~2 g/s) for ~2 min

    data recently published:Gupta et al., Int J Hydrogen Energy 34 (2009) 5902–5911



Approach
Approach safety devices

Scenario based on GARAGE experiment (CEA)

  • Simulation of the helium release and distribution scenario and validation against experimental data

  • Replace helium by hydrogen and verify the calculated distribution

  • Add a PAR to the scenario and compare mitigated/unmitigated scenario


Model approach safety devices


Coupled modeling approach
Coupled Modeling Approach safety devices

Micro Scale

Meso Scale

Macro Scale

REKO-DIREKT(in-house)

ANSYS CFX


Par model reko direkt

Output: T, y safety devicesi, m

natural convection

Chimney

chemical (catalytical) reaction

mass/heat transfer

Catalystsection

Input: T, yi, p

PAR model: REKO-DIREKT


REKO-DIREKT safety devices

REKO-DIREKT  CFX- Outlet gas temperature- Outlet gas composition- Mass flow through PAR

REKO-DIREKT  CFX

T / °C

yH2 / Vol.-%

CFX  REKO-DIREKT- Inlet gas temperature- Inlet gas composition- Pressure


Results safety devices


Unmitigated release setup
Unmitigated release - setup safety devices

  • Physical Model:

  • Half Symmetry

  • RANS equations

  • Ideal gas equation of state

  • Isothermal

  • SST-model incl. buoyancy prod. & dissipation

  • Injection

    • He: 240 g (1,99 g/s)

    • H2: 120 g (0,99 g/s)

  • Wall functions at inner walls

  • Vent: Outlet Boundary



Mitigated release setup
Mitigated release - setup safety devices

  • Physical Model:

  • Half Symmetry

  • RANS equations

  • Ideal gas equation of state

  • SST-model incl. buoyancy prod. & dissipation

  • Injection

    • H2: 120 g (0,99 g/s)

  • Wall functions at inner walls

  • Fixed Wall Temperature

  • Temperature dependent properties

  • No heat radiation

  • Vent: Outlet Boundary


Comparison mitigated unmitigated scenario

120 s safety devices

240 s

800 s

Comparison mitigated/unmitigated scenario




Par model details
PAR model details safety devices



Performance estimates
Performance (estimates) safety devices

Processor

  • 1 CPU Quadcore I7-860, 2.8 GHz

  • Open Suse Linux 11.3

  • CFX 12.1

    Calculation time (1200 s)

  • unmitigated scenario: ~10 d

  • mitigated scenario: ~40 d

    • REKO-DIREKT: ~6 min

    • more time steps

    • more gas components (H2+O2+N2+H2O)


Conclusions safety devices


Conclusions 1 2
Conclusions (1/2) safety devices

Goal

  • investigate the applicability of PAR from NPP containment to typical H2&FC application

    • significant differences in operational boundary conditions

  • first study based on GARAGE experiment, performed with ANSYS-CFX and REKO-DIREKT

    Results

  • H2 injection of 1.5 m³, flammable cloud was removed within 10 minutes

  • hot exhaust plume promotes the transport of hydrogen rich gas mixture towards the PAR inlet


Conclusions 2 2
Conclusions (2/2) safety devices

Next steps

  • parameter variation

    • injection rate, location, and direction

    • PAR design and number

    • geometry of the enclosure

  • consideration of possible PAR ignition scenarios

  • validation against mitigation experiments in new multi-compartment facility, currently under construction at JÜLICH



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