Detection of Hydrogen Released in a Full-scale Residential Garage Thomas Cleary & Erik Johnsson Fire...
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Detection of Hydrogen Released in a Full-scale Residential Garage Thomas Cleary & Erik Johnsson Fire Research Division Engineering Laboratory National Institute of Standards and Technology Gaithersburg, MD ICHS 2011 September 12-14, 2011 San Francisco, California-USA
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Transcript of Detection of Hydrogen Released in a Full-scale Residential Garage Thomas Cleary & Erik Johnsson Fire...
Detection of Hydrogen Released in a Full-scale Residential Garage
Thomas Cleary & Erik Johnsson
Fire Research DivisionEngineering Laboratory
National Institute of Standards and TechnologyGaithersburg, MD
ICHS 2011September 12-14, 2011
San Francisco, California-USA
Objective
To assess whether or not a low-level leak of hydrogen gas can be detected in a residential garage space and if detectable, whether or not hydrogen concentration is uniform across the selected sensor placement locations (ceiling and wall).
NIST Indoor Air Quality House
Garage
• Volume ~ 93 m3
• Ceiling 2.44 m high
Experimental
• A non-combustible gas mixture of nominally 5% hydrogen and 95 % nitrogen was released in a residential garage (forming gas)
• Gas mixture was released through a dispersion box located on the garage floor at a rate of 350 L/min (standard conditions) for about ¾ hour
• Hydrogen sensors mounted on ceiling locations and a wall location recorded concentrations during and after the gas release
• Tests were conducted with and without a car over the dispersion box
Idealized Case
Assuming injected gas displaces garage air, then injecting 3 cylinders of forming gas would yield a well mixed hydrogen concentration of 0.8%, and the oxygen concentration would be reduced from 21% to 17%.
Dispersion Box
• Dispersion Box was a 30 cm by 30 cm sand burner
• Centrally located on garage floor
• Average gas exit velocity was 6.5 cm/s
• Low momentum plume
30 cm
Sensors
• Catalytic bead type hydrogen sensors– range 0 % to 2.5 %
– typical 90 % response time (T-90) of 2 s
– relative uncertainty ± 3 % of reading (two standard deviations)
– Reliable output in reduced oxygen environment (20% reduction possible due to nitrogen flow)
• MOS sensors experienced calibration shift
Sensor Locations
CCeil
WCeil
SCeil
EWall
No Car Over Dispersion Box (Test 4)
Initial Response
• CCeil – 19 s
• WCeil – 29 s
• SCeil – 40 s
• EWall – 49s
0.0
0.2
0.4
0.6
0.8
1.0
0 500 1000 1500 2000 2500 3000 3500 4000
CCeil-H2EWallH-H1SCeil-H3WCeil-H4
Hyd
rog
en
Vo
lum
e P
erc
en
t
Time, s
Source Off
Car Over Dispersion Box (Test 2)
Initial Response
• CCeil – 57 s
• SCeil – 70 s
• EWall – 84 s
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 500 1000 1500 2000 2500 3000 3500 4000
CCeil-H2EWallH-H1SCeil-H3WCeil-H4
Hyd
rog
en
Vo
lum
e P
erce
nt
Time, s
Source Off
Car Over Dispersion Box (Test 3)
Initial Response
• CCeil – 58 s
• EWall – 80 s
• SCeil – 85 s
• WCeil – 90 s
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 500 1000 1500 2000 2500 3000 3500 4000
CCeil-H2EWallH-H1SCeil-H3WCeil-H4
Hyd
rog
en
Vo
lum
e P
erce
nt
Time, s
Source Off
Central Ceiling Location
0.0
0.2
0.4
0.6
0.8
1.0
0 1000 2000 3000 4000
Test 2 - CarTest 3 - CarTest 4 - No Car
Hyd
rog
en
Vo
lum
e P
erc
en
t
Time, s
Source Off
South Ceiling Location
0.0
0.2
0.4
0.6
0.8
0 1000 2000 3000 4000
Test 2 - CarTest 3 - CarTest 4 - No Car
Hyd
rog
en
Vo
lum
e P
erc
en
t
Time, s
Source Off
West Ceiling Location
0.0
0.2
0.4
0.6
0.8
0 1000 2000 3000 4000
Test 2 - CarTest 3 - CarTest 4 - No Car
Hyd
rog
en
Vo
lum
e P
erc
en
t
Time, s
Source Off
East Wall Location
0.0
0.2
0.4
0.6
0.8
0 1000 2000 3000 4000
Test 2 - CarTest 3 - CarTest 4 - No Car
Hyd
rog
en
Vo
lum
e P
erc
en
t
Time, s
Source Off
Time to Reach 0.4% Hydrogen
0
500
1000
1500
2000
2 3 4
Central CeilingSouth CeilingWest CeilingEast Wall
Tim
e to
0.4
% H
yd
rog
en
, s
Experiment
Car Car No Car
Ceiling Air Speed
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0 1000 2000 3000 4000
Test 2 - CarTest 3 - CarTest 4 - No Car
Air
Sp
eed
, m/s
Time, s
57 point smooth applied(1 pt/s data rate)
Hydrogen Concentration Decay Experiment 2
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 8000 16000 24000 32000 40000 48000 56000
CCeil-H2EWallH-H1SCeil-H3WCeil-H4
Hyd
rog
en
Vo
lum
e P
erc
en
t
Time, s
5 h 10 h
Average air exchange rate = 0.37/hr
Conclusions
• The low level hydrogen leak was easily detected in the unventilated garage space
• A car placed over the dispersion box:– reduced peak concentration by 25% compared to the
no-car case
– took considerably more time to reach a threshold of 0.4 % hydrogen compared to the no-car case
• No clear advantage locating sensor in any of the investigated locations
