1. 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

2. 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 ë In order to better predict when hydrogen explosive atmospheres may occur

3. Test facility description : Experimental set up Measurement techniques Experimental Program Results and discussion Conclusion CONTENT

4. TESTS SETTING

5. measurement points (1 to 16) Test Chamber Isothermal and supposed tight

6. Release orifice "sevran 1" P1 Th1 H 2 V1 V3 V2 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 NH 3 aq conc NH 4 Cl droplets 265 mm 120 mm P 1,T 1 P 2, T 2 P3P3 T3T3

7. MEASUREMENTS

8. O 2 controllers Accuracy: –O 2 = 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

9. Seeding to see... Controlled flow of Hydrogen Argon laser Rotating mirror Gas seeding device Helium release seeded with NH 4 Cl nanometric droplets Mirror With He only and without O2 sensors

10. EXPERIMENTAL PROGRAMME

11. H 2 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

12. H e 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

13. RESULTS : Video

14. He - 1,84 g/s - 4 minutes 10 s 120 s235 s First phase: Subsonic jet and stratification - convective flow - short time scale

15. Diffusion: several hours 4 min 85 min 160 min Second phase: Diffusion - Diffusive flow - large time scale

16. RESULTS : Concentration measurements

17. 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

18. 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

19. Variation of %H2 in the jet axis Results for a 1g/s H2 release through a 20 mm hole during 240 s 500060007000 Time (s) Volumic fraction of H2 (v/v) position 1 position 13 position 14 position 16

20. Time (minutes) 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

21. Concentration Profiles at 240 s for various subsonic releases 1m40 aside from release

22. He - 1,84 g/s - 20mm - 240sH2 - 1 g/s - 20mm - 240s Similarity between H2 and He at same flow rate (in mole)

23. Conclusions - perspectives

24. 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 / H 2 similarities Numerical modelling – Data used for CFD benchmark (HySafe) Perspectives – Deeper study of ventilation effects – Supersonic releases in confined volume

25. Tightness of the chamber walls and control of small leakage

26. Pos 6 Pos 8 Pos 9 Pos 10 Pos 11 Pos 12 Simulated holes D.S.  c sup / h i -D.S.  c inf /h i -(  / .g. h i ) 0.5 V i /h i Variable : holes surface Modelling hydrogen concentration in the chamber Equivalent leak area between 90 and 170 cm 2

27. Comparison between measured velocity and calculated velocity with Cd = 0.68 Mass flow rate and velocity at orifice