Mitglied der Helmholtz-Gemeinschaft Simulation of the efficiency of hydrogen recombiners as safety...

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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

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Overview

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

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Unintended H2 release inside confined space

safety measure device

detection sensor

release interruption automatic valve

avoid hydrogen accumulation and ignition/explosion

ventilation

recombiner

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Passive auto-catalytic recombiner (PAR)

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Commercial PARs in Nuclear Power Plants

Vendors AECL, Canada AREVA, France/Germany NIS, Germany

Source: Siempelkamp

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Operational boundary conditions

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

NPP PAR applicability ? H2 & FCGOAL:

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Scenario

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Source: CEAExperiment

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

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Release scenario and measurement locations

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Approach

Scenario based on GARAGE experiment (CEA)

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

2. Replace helium by hydrogen and verify the calculated distribution

3. Add a PAR to the scenario and compare mitigated/unmitigated scenario

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Model approach

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Coupled Modeling Approach

Macro ScaleMeso ScaleMicro Scale

REKO-DIREKT(in-house)

ANSYS CFX

H2-Injection

Vent

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PAR model: REKO-DIREKT

Input: T, yi, p

Output: T, yi, m

chemical (catalytical)

reaction

natural convection

Ch

imn

eyC

atal

yst

sec

tio

n

mass/heat transfer

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T / °CyH2 / Vol.-%

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

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

REKO-DIREKT CFX

REKO-DIREKT

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Results

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Unmitigated release - setup

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

H2-Injection

Vent

Grid statistics:Nodes 214.272y+ < 250face angle > 45°aspect ratio < 49volume ratio < 14

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Helium/Hydrogen concentration profiles

0

500

1000

1500

2000

2500

0% 1% 2% 3% 4% 5% 6% 7% 8% 9%He / H2 fraction [vol.%]

z -

axis

[m

m]

Experiment

CFX - Helium

CFX - Hydrogen

30 s 60 s 90 s 120 s

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H2-Injection

Vent

Mitigated release - setup

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

AREVA PAR type FR90-150

Inlet Boundary

Outlet Boundary

Adiabatic WallsGrid statistics:

Nodes 203.385y+ < 70face angle > 45°aspect ratio < 49volume ratio < 16

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Comparison mitigated/unmitigated scenario

800 s

240 s

120 s

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Comparison mitigated/unmitigated scenario

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Details mitigated scenario

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PAR model details

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Flammable cloud volume histories

0

5

10

15

20

25

0 200 400 600 800 1000

time [s]

flam

mab

le v

olum

e (>

4 vo

l.% H

2) [m

³]

with PAR

unmitigated

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Performance (estimates)

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)

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Conclusions

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Conclusions (1/2)

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

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Conclusions (2/2)

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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Thank you for your attention !