Thomas Cleary amp Erik Johnsson Fire Research Division Engineering Laboratory National Institute of Standards and Technology Gaithersburg MD ICHS 2011 September 1214 2011 San Francisco CaliforniaUSA ID: 513893
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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-USASlide2
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).Slide3
NIST Indoor Air Quality House
Garage
Volume ~ 93 m
3
Ceiling 2.44 m highSlide4
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 Slide5
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%. Slide6
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
plumeSlide7
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 Slide8
Sensor LocationsSlide9
No Car Over Dispersion Box (Test 4)
Initial Response
CCeil
– 19 s
WCeil
– 29 sSCeil – 40 sEWall – 49sSlide10
Car Over Dispersion Box (Test 2)
Initial Response
CCeil
– 57 s
SCeil
– 70 sEWall – 84 sSlide11
Car Over Dispersion Box (Test 3)
Initial Response
CCeil
– 58 s
EWall – 80 s
SCeil – 85 sWCeil – 90 sSlide12
Central Ceiling LocationSlide13
South Ceiling LocationSlide14
West Ceiling LocationSlide15
East Wall LocationSlide16
Time to Reach 0.4% HydrogenSlide17
Ceiling Air SpeedSlide18
Hydrogen Concentration Decay
Experiment 2
Average air exchange rate = 0.37/hrSlide19
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