1. Gilles Bernard-Michel (CEA)
Comparisons of helium and hydrogen releases in 1m3 and 2 m3 two vents enclosures: concentration measurements at different flow rates and for two diameters of injection nozzle.
Gilles Bernard-Michel (CEA)
Deborah Houssin
(Air Liquide)

2. Geometry: 2 vents cavities
2 m3 cavity:
2.10 m height
1mx1m base
top and bottom vent of 19cmx98cm
1 m3 cavity:
1 m height
0.995mx0.995m base
top and bottom vent of 18cmx96cm

3. Sensors Xensor TCG3880 catharometres: 15 sensors
Calibrated for he and h2
Regular spacing

4. Experiments, C measurements:
Varying parameters
Experiments, C measurements:
2 different enclosures (1m3 and 2m3)
2 different injection nozzle (4 mm, 27.2 mm)
Flow rates from 5Nl/min up to 210 Nl/min
2 gas: He and H2
From plume to jet:
- Richardson number 5.77·107 down to 7.08·10-4

5. Experimental process Reproducibility: Stationnary state:
Tests performed at INERIS, AL and CEA (different facilities)
2 differents sets of sensors for some of the tests
Series of tests at INERIS
Different flowmeters used
Stationnary state:
Only stationnay data are used
long enough gas injections (approx 10 min)
Time averaged concentrations:
Errors less than 0.3% absolute concentration
- Mainly calibration

6. Reproducibility results with he
-2 locations: INERIS and CEA
Ambient temperature
of 11°C (INERIS) and 20°C (CEA)
Almost no air circulation
Humidity of 100% (INERIS)
and 55%(CEA)
2 sets of sensor (AL and CEA)
2 different calibrated flowmeters
(CEA and AL)
Exp. I
Exp. II
Exp. III
Diameter
Flow rate
Cmax mm
NL/min
%vol 27
210
6.6
6.5
6.7 70
2.81
2.9
3.1 20
1.34
1.4
1.3 5
0.68
0.55
0.6

7. Model and scaling Scaling: Linden model:
2 homogenous layers
1D distribution outside the jet
pure air layer at the bottom
concentration depends on
distance between injection and
top vent
Scaling:

8. Hydrogen versus helium comparisons on 2-m3 enclosure
Diam mm
flow rate he
NL/min
Cmax he
%vol
Cmax h2 27 5
0.68
1,06 4
0.88
1.09 20
1.34
1.83
1.41
1.73 70
2.81
3.35
2.74
3.3
210
6.6
6.17
4,69
5,44

9. Hydrogen versus helium comparisons on 1-m3 enclosure
Injection
(mm)
flow rate
NL/min
Cmax he
%vol
Cmax h2 27 10
1,79
1.80 4
1.97
2.04 20 -
2.52
2.76
3.0 60
5.03
4.35
4.99
100
8.23
6.69
4.84
6.15
210
11.12
7.38

10. First observations Injection diameter: Gas effect:
Smaller injection diameter => smaller maximum concentration at higher flow rates
injection diameter has few influence for plumes regimes.
Gas effect:
similar behavior for plumes regimes for he and H2 with slightly higher concentrations
for h2.
larger spreading of maximum he concentration vs diameter than for h2.
=> For large injection diameter, max he concentration > max h2 concentration
=> For small injection diameter, max h2 concentration > max he concentration
Similitude law has to be improved
=> Based on flow rates and another parameter (diameter?, ……)

11. Some first explanations ?
Similitude law requires same
Interface’s height
We observe different interfaces
heights for he and h2.
The sensitive parameter in
Linden’s model is the mixing
Length. We need to have a
closer look at this (models
are based on different definitions
of reduced gravity)

12. Thanks for your attention