CFD MODELING OF LH2 DISPERSION USING THE ADREA-HF CODE

4TH International Conference on Hydrogen Safety (ICHS2011) organized by IA HySafeSeptember 12-14, 2011, San Francisco, USA 1

CFD MODELING OF LH2 DISPERSION USING THE

ADREA-HF CODEGiannissi, S.G.Giannissi, S.G.1,21,2, , Venetsanos, A.G.Venetsanos, A.G.11, Bartzis, Bartzis33, , J.G., MarkatosJ.G., Markatos22, N., Willoughby, D.B., N., Willoughby, D.B.44 and and Royle, M.Royle, M.44

11 Environmental Research Laboratory, National Centre for Scientific Research Environmental Research Laboratory, National Centre for Scientific Research Demokritos, 15310 Aghia Paraskevi, Attikis, Greece, email: Demokritos, 15310 Aghia Paraskevi, Attikis, Greece, email: [email protected]@ipta.demokritos.gr,,[email protected]@ipta.demokritos.gr

22 National Technical University of Athens, School of Chemical Engineering, National Technical University of Athens, School of Chemical Engineering, Department of Process Analysis and Plant Design, Heroon Polytechniou 9, 15780 Department of Process Analysis and Plant Design, Heroon Polytechniou 9, 15780 Zografou, Greece, email: [email protected], Greece, email: [email protected]

33 Department of Energy and Resources Management Engineering, University of West Department of Energy and Resources Management Engineering, University of West Macedonia, Kozani, Greece, email: [email protected], Kozani, Greece, email: [email protected]

44 Health and Safety Laboratory, Buxton, Derbyshire, SK17 9JN, United Kingdom, Health and Safety Laboratory, Buxton, Derbyshire, SK17 9JN, United Kingdom, email: [email protected], [email protected]: [email protected], [email protected]

4TH International Conference on Hydrogen Safety (ICHS2011) organized by IA HySafe September 12-14, 2011, San Francisco, USA4TH International Conference on Hydrogen Safety (ICHS2011) organized by IA HySafe September 12-14, 2011, San Francisco, USA4TH International Conference on Hydrogen Safety (ICHS2011) organized by IA HySafe September 12-14, 2011, San Francisco, USA

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OUTLINE

• ObjectivesObjectives

• HSL (Health and Safety Laboratory) ExperimentsHSL (Health and Safety Laboratory) Experiments • Test1 Test1 (test chosen for simulation)(test chosen for simulation)

o Test1-Humidity EffectTest1-Humidity Effect

• Modeling StrategyModeling Strategyo PhysicsPhysicso NumericsNumerics

• ResultsResults

• ConclusionsConclusions


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OBJECTIVES

• Validation of the CFD code, ADREA-HF, for its Validation of the CFD code, ADREA-HF, for its performance in simulation of cryogenic releases. performance in simulation of cryogenic releases. Test1 of the HSL experiments (LH2 release Test1 of the HSL experiments (LH2 release experiments) is chosen for simulation. experiments) is chosen for simulation.

• Examination of the humidity effect on the hydrogen Examination of the humidity effect on the hydrogen vapor dispersion. vapor dispersion.

Heat liberation Heat liberation (latent heat of (latent heat of liquefaction and liquefaction and solidification)solidification)

H2 vapor cloud H2 vapor cloud more buoyantmore buoyant

Water vapor liquefactionWater vapor liquefactionand solidification due to and solidification due to the cold, hydrogen the cold, hydrogen cloud (20K)cloud (20K)


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HSL (HEALTH AND SAFETY LABORATORY) EXPERIMENTS1

• 4 LH2 release tests with spill rate 60lt/min 4 LH2 release tests with spill rate 60lt/min

Test Test Release Release height height (mm (mm

above ground)above ground)

Release Release directiondirection

Spill Spill duration duration

(sec)(sec)

11 3.363.36 horizontalhorizontal 248248

22 100100 vertically vertically downwardsdownwards 561561

33 860860 horizontalhorizontal 305305

44 100100 vertically vertically downwardsdownwards 215215

Photograph taken from HSL

1 Willoughby, D.B., Royle, M., Experimental Releases of Liquid Hydrogen, 4th International Conference on Hydrogen Safety, San Francisco, California-USA, ICHS , Paper 1A3, 2011


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TEST1

• Release and weather conditionsRelease and weather conditions

source diameter (mm)source diameter (mm) 26.626.6

source temperature (K)source temperature (K) 2020

release rate release rate (kg/sec)(kg/sec) 0.070.07

release duration release duration (sec)(sec) 248248

wind speed wind speed (m/s)(m/s)[email protected]@2.5 2.6752.675

wind direction-@ 2.5 mwind direction-@ 2.5 m 291.02291.02

average ambient average ambient temperature temperature (K)(K)

283.56283.56

relative humidity relative humidity (%)(%) 6868

Photographs taken from HSL


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TEST1

• Release and weather conditionsRelease and weather conditions

Site layout (not drawn to scale)

source diameter (mm)source diameter (mm) 26.626.6

source temperature (K)source temperature (K) 2020

release rate release rate (kg/sec)(kg/sec) 0.070.07

release duration release duration (sec)(sec) 248248

wind speed wind speed (m/s)(m/s)[email protected]@2.5 2.6752.675

wind direction-@ 2.5 mwind direction-@ 2.5 m 291.02291.02

average ambient average ambient temperature temperature (K)(K)

283.56283.56

relative humidity relative humidity (%)(%) 6868


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MODELING STRATEGY Physics (1/3)

• Multi-phase multi component RANS CFD calculation using ADREA-Multi-phase multi component RANS CFD calculation using ADREA-HF CFD code.HF CFD code.

• 3-D transient, fully compressible conservation equations for 3-D transient, fully compressible conservation equations for mixture mass, mixture momentum, mixture enthalpy, hydrogen mixture mass, mixture momentum, mixture enthalpy, hydrogen mass fraction and water mass fraction (when ambient humidity mass fraction and water mass fraction (when ambient humidity was taken into account).was taken into account).

• Phase distribution: Non vapor phase (liquid+solid) of component-I Phase distribution: Non vapor phase (liquid+solid) of component-I appears when the mixture temperature falls below the mixture appears when the mixture temperature falls below the mixture dew temperature, which is calculated using the Raoult’s law for dew temperature, which is calculated using the Raoult’s law for ideal gases. The solid phase of component-I appears when the ideal gases. The solid phase of component-I appears when the mixture temperature drops below the freezing point.mixture temperature drops below the freezing point.

• Standard k-Standard k-ε ε with buoyancy effect term.with buoyancy effect term.• One dimensional, transient energy (temperature) equation inside One dimensional, transient energy (temperature) equation inside

the ground. The ground has the concrete’s properties.the ground. The ground has the concrete’s properties.


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• In presence of solid H2O (ice), mixture dynamic viscosity is In presence of solid H2O (ice), mixture dynamic viscosity is calculated using 2 different approaches:calculated using 2 different approaches:o Ice viscosity function of temperatureIce viscosity function of temperature

• The liquid H2O viscosity correlation used below the FPThe liquid H2O viscosity correlation used below the FPo Constant ice viscosityConstant ice viscosity

• Equal to the water viscosity at freezing pointEqual to the water viscosity at freezing point

isisililiviv qqq


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Initial conditions:Initial conditions: • To obtain the initial conditions of wind speed, ambient temperature and To obtain the initial conditions of wind speed, ambient temperature and

turbulence the procedure that followed consists of two steps: turbulence the procedure that followed consists of two steps: 1.1. One dimensional (in the z-direction) problem was solved to obtain One dimensional (in the z-direction) problem was solved to obtain

the wind profile according to the experimental data. Neutral the wind profile according to the experimental data. Neutral atmospheric conditions were assumed. atmospheric conditions were assumed.

2.2. Three dimensional, steady problem was solved with initial conditions Three dimensional, steady problem was solved with initial conditions the ones calculated by the previous step (the wind direction was in the ones calculated by the previous step (the wind direction was in line with the release). line with the release).

• The transient problem with hydrogen release was solved using as initial The transient problem with hydrogen release was solved using as initial conditions the ones derived by the second step. In the case with humidity, conditions the ones derived by the second step. In the case with humidity, additional initial condition for the water vapor mass fraction (5.34additional initial condition for the water vapor mass fraction (5.34 ∙10∙10-3-3) ) was was used in the whole domain, calculated by the experiment’s relative used in the whole domain, calculated by the experiment’s relative humidity.humidity.

Boundary conditions:Boundary conditions:• Inlet: The values of all variables were the same as the initial conditions. Inlet: The values of all variables were the same as the initial conditions. • Source: The source was modeled as two phase jet. The void fraction of the Source: The source was modeled as two phase jet. The void fraction of the

vapor phase is calculated by assuming isenthalpic expansion from 2 bars vapor phase is calculated by assuming isenthalpic expansion from 2 bars (inside the tanker) to 1.2 bars (after the valve is open) and is equal to (inside the tanker) to 1.2 bars (after the valve is open) and is equal to 71.34%. Temperature, pressure and horizontal velocity were set equal to 71.34%. Temperature, pressure and horizontal velocity were set equal to 21K, 1.2 bars and 6.02 m/s respectively.21K, 1.2 bars and 6.02 m/s respectively.


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MODELING STRATEGY Numerics

Computational Computational

domain (m)domain (m)Grid Grid

characteristics (m)characteristics (m)

xx yy zz

grid dimensiongrid dimension total number total number of cellsof cells

dxdx

(min-max)(min-max)dydy

(min-max)(min-max)dzdz

(min-max)(min-max)

8080 7070 2020 66 x 66 x 2366 x 66 x 23 100188100188 0.1-6.4880.1-6.488 0.1-3.8670.1-3.867 0.2-2.2700.2-2.270

Figure from Edes (GUI of ADREA-Hf code)

• First order fully implicit scheme for time First order fully implicit scheme for time integration.integration.

• First order upwind scheme for discretization of First order upwind scheme for discretization of the convective termsthe convective terms

• ILU(0) preconditioned BiCGStab solver for the ILU(0) preconditioned BiCGStab solver for the algebraic systems (parallel)algebraic systems (parallel)

• Initial time step 10Initial time step 10-4-4

• Courant number restriction (CFL<2)Courant number restriction (CFL<2)


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RESULTS (1/6)

Hydrogen concentration history

at locations downwind the release point


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RESULTS (2/6)Hydrogen concentration history at different heights


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RESULTS (3/6)

Duration 12 secDuration 12 sec

humidityhumidityno humidityno humidity


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RESULTS (4/6)

humidityno humidity

t = 20 sec


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RESULTS (5/6)

HH22 vapor volume fraction contoursvapor volume fraction contours

t = 20 sec

HH22O non vapor mass fraction contoursO non vapor mass fraction contours


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RESULTS (6/6)

Temperature contoursTemperature contours HH22O non vapor mass fraction contoursO non vapor mass fraction contours

t = 20 sec


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CONCLUSIONS (1/2)

Multi-phase, multi component CFD calculations have been performed Multi-phase, multi component CFD calculations have been performed with ADREA-HF code to simulate HSL test-1 LH2 release. The working with ADREA-HF code to simulate HSL test-1 LH2 release. The working fluid was assumed to be composed of dry air (gas), water fluid was assumed to be composed of dry air (gas), water (vapor/liquid/solid) and h2 (vapor/liquid)(vapor/liquid/solid) and h2 (vapor/liquid)

Predicted concentration histories with humidity are in better Predicted concentration histories with humidity are in better agreement with the experiment compared to the case without agreement with the experiment compared to the case without humidity.humidity.

It has been verified that the H2-humid air cloud becomes more It has been verified that the H2-humid air cloud becomes more buoyant than when neglecting the humidity, due to the heat buoyant than when neglecting the humidity, due to the heat liberation by the water vapor condensation/solidification.liberation by the water vapor condensation/solidification.

Predictions with humidity were found sensitive to the way mixture Predictions with humidity were found sensitive to the way mixture molecular viscosity is modeled in case of presence of solids (ice). molecular viscosity is modeled in case of presence of solids (ice). The assumption that ice viscosity follows the liquid viscosity formula The assumption that ice viscosity follows the liquid viscosity formula below the freezing point gave good results.below the freezing point gave good results.


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CONCLUSIONS (2/2)

Predictions show that including humidity reduces horizontal Predictions show that including humidity reduces horizontal distance to LFL cloud by 40% (almost 10m) and increase the distance to LFL cloud by 40% (almost 10m) and increase the height to LFL cloud (almost 1m) in the present case. height to LFL cloud (almost 1m) in the present case.

Further work on the humidity effects is necessary to support Further work on the humidity effects is necessary to support present findingspresent findings

4TH International Conference on Hydrogen Safety (ICHS2011) organized by IA HySafeSeptember 12-14, 2011, San Francisco, USA

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CFD MODELING OF LH2 DISPERSION USING THE ADREA-HF CODE