Large-Scale Hydrogen Release In

An Isothermal Confined Area J.M. LACOME – Y. DAGBA – D. JAMOIS – L. PERRETTE- C. PROUST

ICHS- San Sebastian, sept 2007

OBJECTIVES :

• Study confined moderate releases of hydrogen :

Hydrogen stratification in the room during release depending upon release flow rate and release diameter (subsonic releases)

And diffusion mechanisms when release stops (in quiescent atmosphere)

• Based upon concentration mapping and video recording

In order to better predict when hydrogen explosive atmospheres may occur

•Test facility description :

• Experimental set up

• Measurement techniques

• Experimental Program

• Results and discussion

• Conclusion

CONTENT

TESTS SETTING

measurement points (1 to 16)Value Unit

Widht 3.78 m

Lenght 7.2 m

height 2.88 m

Groundsurface

27.216 m2

Volume 78.382 m3

Test Chamber

Isothermal and supposed tight

16

14

13

1 4 6

8

9

10

11

12

7

88

188

138238

268

283

190140

40Vertical Plan viewcutting the release point

Release orifice

"sevran 1"

P1

Th1

H2

V1V3V2

P diaph.

Mass flow control: sonic nozzle

Release orifice at the centre of the room

Release velocity: release orifice

PID

HCl conc

Pressure and temperature measurement

NH3 aq conc

NH4Cl droplets

265 mm

120 mm

P1,T1

P2,T2

P3

T3

MEASUREMENTS

O2 controllers

• Accuracy:

– O2 = 0.02% vol.

– gas = 1.5 % rel.

• Flow:– 2 l/mn

– 2 mm tube

– 9 m long

– transients 5-10 sec

3 analysers for 12 measurements points with a period of 80s (for 4 measurements)

Measurements

Seeding to see...

Controlled flow of HydrogenArgon laser Rotating mirror Gas seeding device

Helium release seeded with NH4Cl

nanometric droplets

Mirror

With He only and without O2 sensors

EXPERIMENTAL PROGRAMME

H2 release- Realistic flow rate for moderate up to relatively severe subsonic hydrogen

release

- Up to 4 hours test duration (release and diffusion phase)

- Indirect H2 concentration measurement with O2 controllers

- No laser and no video recording (safety concerns)

Experimental Programme

Flow rate(g/s)

Release diameter(mm)

Exit velocity(m/s)

Release duration(s)

Openingstatus

(open/closed)

0,7 20 38 240 closed

0,7 20 38 240 open

1 20 53 240 closed

1 10 210 240 closed

0,2 20 11 240 closed

0,2 5 170 240 closed

He release- Volumetric flow rate conservation: same as H2 releases

- Some tests with seeding and video recording to visualise the He rich atmosphere pattern but no O2 measurements (pollution concerns)

- Some tests with indirect He concentration measurement (O2 controllers)

- Up to 4 hours test duration (release and diffusion phase)

Experimental Programme

Flow rate

(g/s)

Release diameter(mm)

Exit velocity(m/s)

Release duration(s)

Openingstatus

(open/closed)

1,84 20 55 240 closed

1,84 10 215 240 closed

0,4 5 190 240 closed

RESULTS :Video

He - 1,84 g/s - 4 minutes

10 s 120 s 235 s

First phase: Subsonic jet and stratification

- convective flow

- short time scale

Diffusion: several hours

4 min 85 min 160 min

Second phase: Diffusion

- Diffusive flow

- large time scale

RESULTS :Concentration measurements

0%

1%

2%

3%

4%

5%

6%

7%

8%

9%

0 1000 2000 3000 4000 5000 6000 7000 8000

Time (s)

Vo

lum

ic f

ract

ion

of H

2 (

v/v)

position 6position 8position 9position 10position 11position 12

Variation of %H2 at different heights, 1m40 aside from release

Results for a 1g/s H2 release through a 20 mm hole during 240 s and subsequent diffusion phase during 2 hours

16

14

13

1 4 6

8

9

10

11

12

7

88

188

138238

268

283

190140

40Vertical Plan viewcutting the release point

Variation of %H2 at various sampling points located at the ceiling

Typical results for a 1g/s H2 release through a 20 mm hole during 240 s

0%

1%

2%

3%

4%

5%

6%

7%

8%

9%

10%

0 1000 2000 3000 4000 5000 6000 7000

Time (s)

Vo

lum

ic f

ract

ion

of H

2 (

v/v)

position 1

position 4

position 6

position 7

16

14

13

1 4 6

8

9

10

11

12

7

88

188

138238

268

283

190140

40Vertical Plan viewcutting the release point

Variation of %H2 in the jet axis

Results for a 1g/s H2 release through a 20 mm hole during 240 s

0%

2%

4%

6%

8%

10%

12%

14%

16%

18%

20%

0 1000 2000 3000 4000 5000 6000 7000

Time (s)

Vol

umic

frac

tion

of H

2 (v

/v)

position 1

position 13

position 14

position 16

16

14

13

1 4 6

8

9

10

11

12

7

88

188

138238

268

283

190140

40Vertical Plan viewcutting the release point

Time (minutes)

0,0%

0,2%

0,4%

0,6%

0,8%

1,0%

1,2%

1,4%

1,6%

1,8%

2,0%

2,2%

2,4%

0 20 40 60 80 100 120 140 160 180 200 220 240

Gas

co

nce

ntr

atio

n (

%v

/v)

position 6

position 8

position 9

position 10

position 11

position 12

Homogeneous mixing concentration

16

14

13

1 4 6

8

9

10

11

12

7

88

188

138238

268

283

190140

40Vertical Plan viewcutting the release point

Variation of %H2 at different heights, 1m40 aside from release

Results for a 200mg/s H2 release through a 5 mm hole during 240 s

0

50

100

150

200

250

300

0 2 4 6 8 10

concentration %vol

Hei

ght f

rom

rel

ease

poi

nt (c

m)

1g - 20mm - 53 m/s

1g - 10mm - 210 m/s

0,2g - 10mm - 11 m/s

0,2g - 5mm - 170 m/s

Concentration Profiles at 240 s for various subsonic releases

1m40 aside from release

16

14

13

1 4 6

8

9

10

11

12

7

88

188

138238

268

283

190140

40Vertical Plan viewcutting the release point

He - 1,84 g/s - 20mm - 240sH2 - 1 g/s - 20mm - 240s

Similarity between H2 and He at same flow rate (in mole)

0%

1%

2%

3%

4%

5%

6%

7%

8%

9%

0 1000 2000 3000 4000 5000

Time (s)

volu

mic

fra

ctio

n o

f H2

(v/

v)

position 8 position 9 position 10 position 11 position 12

0%

1%

2%

3%

4%

5%

6%

7%

8%

9%

0 1000 2000 3000 4000 5000

Time (s)

volu

mic

fra

ctio

n (

v/v)

Conclusions - perspectives

Experimental achievements – mass control of small leakages

– released gas visualisation with large tomography

– multiport gas sampling

Physical analysis– practical study of stratification process

– study of large scale hydrogen molecular diffusion

– observations on He / H2 similarities

Numerical modelling– Data used for CFD benchmark (HySafe)

Perspectives– Deeper study of ventilation effects

– Supersonic releases in confined volume

Tightness of the chamber walls and control of small leakage

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 20 40 60 80 100 120 140 160 180 200

Time (mn)

rela

tiv

e h

yd

rog

en

vo

lum

e in

th

e c

ha

mb

er

1g/s - orifice 10mm release diameter

0,7 g/s - orifice 20mm release diameter with theupper opening

Pos 6

Pos 8

Pos 9

Pos 10

Pos 11

Pos 12

Simulated holes

D.S.csup/hi

-D.S.cinf/hi

-(/ .g. hi)0.5

Vi/hi

Variable : holes surface

Modelling hydrogen concentration in the chamber

Equivalent leak area between 90 and 170 cm2

0

50

100

150

200

250

0 50 100 150 200 250

Caculated velocity from mass fow rate (m/s)

Mea

sure

d v

elo

city

(m

/s)

hydrogène

helium

Comparison between measured velocity and calculated velocity with Cd = 0.68

Mass flow rate and velocity at orifice