B.CARITEAU, I. TKATSCHENKO CEA Saclay, DEN, DM2S, SMFE, LEEF
description
Transcript of B.CARITEAU, I. TKATSCHENKO CEA Saclay, DEN, DM2S, SMFE, LEEF
ICHS 4, San Francisco, California, USA, September 2011
Experimental study of the effects Experimental study of the effects of vent geometry on the of vent geometry on the
dispersion of a buoyant gas in a dispersion of a buoyant gas in a small enclosuresmall enclosure
B.CARITEAU, I. TKATSCHENKOCEA Saclay, DEN, DM2S, SMFE, LEEF
ICHS 4, San Francisco, California, USA, September 2011
Dispersion in an enclosure : Natural ventilation through one vent
U0,
V
X(z)?
ICHS 4, San Francisco, California, USA, September 2011
A wide range of injection velocity
U0,
V
X(z)?
Dispersion in an enclosure : Natural ventilation through one vent
ICHS 4, San Francisco, California, USA, September 2011
Vent effects
U0,
V
X(z)?
Dispersion in an enclosure : Natural ventilation through one vent
ICHS 4, San Francisco, California, USA, September 2011
Volume Richardson number: 2
00
031
UVgRi a
v
Cleaver et. al. (1994, J. Hazardous Mater. Vol. 36)
Previous results on dispersion regimes without ventilation
ICHS 4, San Francisco, California, USA, September 2011
Volume Richardson number:
RivBuoyancy dominated dispersion
Momentum dominated dispersion
200
031
UVgRi a
v
Cleaver et. al. (1994, J. Hazardous Mater. Vol. 36)
1
Stratified
RiVcd
H
Homogeneous layer
Fully homogeneous
Previous results on dispersion regimes without ventilation
2
025
RHRivc
ICHS 4, San Francisco, California, USA, September 2011
A simple analytical model for dispersion with 1 ventLinden, Lane-Serff & Smeed (1990, J. Fluid Mech. Vol. 212)
ICHS 4, San Francisco, California, USA, September 2011
A simple analytical model for dispersion with 1 ventLinden, Lane-Serff & Smeed (1990, J. Fluid Mech. Vol. 212)
Hypotheses for the analytical model: P and T ConstantHomogeneous distributionPure gravity driven flow through the ventBoussinesq approximation
ICHS 4, San Francisco, California, USA, September 2011
A simple analytical model for dispersion with 1 ventLinden, Lane-Serff & Smeed (1990, J. Fluid Mech. Vol. 212)
Hypotheses for the analytical model: P and T ConstantHomogeneous distributionPure gravity driven flow through the ventBoussinesq approximation
2/10 )( hgXSCQ De Volume flow rate
through the ventS h
a
agg
00
CD=0.25 discharge coefficient
ICHS 4, San Francisco, California, USA, September 2011
A simple analytical model for dispersion with 1 ventLinden, Lane-Serff & Smeed (1990, J. Fluid Mech. Vol. 212)
Hypotheses for the analytical model: P and T ConstantHomogeneous distributionPure gravity driven flow through the ventBoussinesq approximation
2/10 )( hgXSCQ De Volume flow rate
through the ventS h
a
agg
00
CD=0.25 discharge coefficient
3/2
2/10
0
)(
hgSC
QXD
Steady state volume fraction in the enclosure
11ICHS 4, San Francisco, California, USA, September 2011
Goals of the present experiments:
Influence of Riv and vent geometry on the vertical distribution
Compare results to the analytical model
Check the validity of the criterion for homogeneous filling
12ICHS 4, San Francisco, California, USA, September 2011
Experimental set-upExperimental set-up
Steady state vertical distributionSteady state vertical distribution
Volume fraction variations with the flow Volume fraction variations with the flow raterate
13ICHS 4, San Francisco, California, USA, September 2011
Experimental set-upExperimental set-upExperimental set-upExperimental set-up
Steady state vertical distributionSteady state vertical distribution
Volume fraction variations with the flow Volume fraction variations with the flow raterate
ICHS 4, San Francisco, California, USA, September 2011
Vents: (a) 180x900 mm2
(b) 180x180 mm2
(c) 35x900 mm2
Experimental setup and injection Experimental setup and injection conditionsconditions
Injection tube
930m
m
930mm
1260mm
Vent
180m
m20m
m
(b)
180m
m
(a)
35m
m (c)
900mm 180mm
V=1.1m3
ICHS 4, San Francisco, California, USA, September 2011
Sources :D0=5mm or 20mmX0=100% heliumQ0=1 to 300Nl/min
Experimental setup and injection Experimental setup and injection conditionsconditions
Injection tube
930m
m
930mm
1260mm
Vent
180m
m20m
m
D0=5mmD0=20mm
Riv=8 10-4 to 75 Riv=0.2 to 740
Working gases : Helium/Air
V=1.1m3
16ICHS 4, San Francisco, California, USA, September 2011
Helium volume fraction measurement : min-katharometers
100mm
220mm
340mm
460mm
580mm
700mm
820mm
940mm
1060mm
1160mm
Injection tube
katharometers
255mm
625mm
135m
m
240mm
930m
m
930mm
1260mm
Vent
M2 M4
M2
M4
195mm
230mmM1
M1
7mm
17ICHS 4, San Francisco, California, USA, September 2011
Experimental set-upExperimental set-upExperimental set-upExperimental set-up
Steady state vertical distributionSteady state vertical distribution
Volume fraction variations with the flow Volume fraction variations with the flow raterate
ICHS 4, San Francisco, California, USA, September 2011
Steady state: vertical profilesSteady state: vertical profiles
180x900 mm2 vent (a)
0,0
0,2
0,4
0,6
0,8
1,0
0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5
X/<X>
z /H
5Nl/min10Nl/min20Nl/min40Nl/min60Nl/min100Nl/min180Nl/min300Nl/min
Riv
10.2
20mm source : toward buoyancy dominated flow
ICHS 4, San Francisco, California, USA, September 2011
Steady state: vertical profilesSteady state: vertical profiles
180x900 mm2 vent (a)
0,0
0,2
0,4
0,6
0,8
1,0
0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5
X/<X>
z /H
5Nl/min10Nl/min20Nl/min40Nl/min60Nl/min100Nl/min180Nl/min300Nl/min
Riv
10.2
Strong vertical variations
20mm source : toward buoyancy dominated flow
ICHS 4, San Francisco, California, USA, September 2011
Steady state: vertical profilesSteady state: vertical profiles
180x900 mm2 vent (a)
0,0
0,2
0,4
0,6
0,8
1,0
0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5
X/<X>
z /H
5Nl/min10Nl/min20Nl/min40Nl/min60Nl/min100Nl/min180Nl/min300Nl/min
Riv
10.2
Auto-similar
20mm source : toward buoyancy dominated flow
ICHS 4, San Francisco, California, USA, September 2011
0,0
0,2
0,4
0,6
0,8
1,0
0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5X/<X>
z /H
5Nl/min10Nl/min20Nl/min40Nl/min60Nl/min100Nl/min140Nl/min180Nl/min
Riv1
0.05
0.0023
Steady state: vertical profilesSteady state: vertical profiles
180x900 mm2 vent (a)
5mm source : toward momentum dominated flow
ICHS 4, San Francisco, California, USA, September 2011
0,0
0,2
0,4
0,6
0,8
1,0
0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5X/<X>
z /H
5Nl/min10Nl/min20Nl/min40Nl/min60Nl/min100Nl/min140Nl/min180Nl/min
Riv1
0.05
0.0023
Steady state: vertical profilesSteady state: vertical profiles
180x900 mm2 vent (a)
5mm source : toward momentum dominated flow
Top homogeneous layer
ICHS 4, San Francisco, California, USA, September 2011
0,0
0,2
0,4
0,6
0,8
1,0
0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5X/<X>
z /H
5Nl/min10Nl/min20Nl/min40Nl/min60Nl/min100Nl/min140Nl/min180Nl/min
Riv1
0.05
0.0023
Steady state: vertical profilesSteady state: vertical profiles
180x900 mm2 vent (a)
5mm source : toward momentum dominated flow
Homogeneous for Riv<0.0023
ICHS 4, San Francisco, California, USA, September 2011
0,0
0,2
0,4
0,6
0,8
1,0
0,8 0,9 1,0 1,1 1,2 1,3 1,4
z /H
X/<X>
5Nl/min10Nl/min20Nl/min40Nl/min60Nl/min100Nl/min180Nl/min300Nl/min
Riv
10.2
Steady state: vertical profilesSteady state: vertical profiles
180x180 mm2 vent (b)
20mm source : toward buoyancy dominated flow
ICHS 4, San Francisco, California, USA, September 2011
0,0
0,2
0,4
0,6
0,8
1,0
0,8 0,9 1,0 1,1 1,2 1,3 1,4
z /H
X/<X>
5Nl/min10Nl/min20Nl/min40Nl/min60Nl/min100Nl/min140Nl/min180Nl/min
Riv1
0.05
0.0023
Steady state: vertical profilesSteady state: vertical profiles
180x180 mm2 vent (b)
5mm source : toward momentum dominated flow
ICHS 4, San Francisco, California, USA, September 2011
0,0
0,2
0,4
0,6
0,8
1,0
0,8 0,9 1,0 1,1 1,2 1,3 1,4
z /H
X/<X>
5Nl/min10Nl/min20Nl/min40Nl/min60Nl/min100Nl/min140Nl/min180Nl/min
Riv1
0.05
0.0023
Steady state: vertical profilesSteady state: vertical profiles
180x180 mm2 vent (b)
5mm source : toward momentum dominated flow
Homogeneous for Riv<0.0023
ICHS 4, San Francisco, California, USA, September 2011
0,0
0,2
0,4
0,6
0,8
1,0
0,4 0,6 0,8 1,0 1,2 1,4
X/<X>
z /H 5Nl/min
10Nl/min20Nl/min40Nl/min60Nl/min100Nl/min180Nl/min300Nl/min
Riv
10.2
Steady state: vertical profilesSteady state: vertical profiles
35x900 mm2 vent (c)
20mm source : toward buoyancy dominated flow
ICHS 4, San Francisco, California, USA, September 2011
0,0
0,2
0,4
0,6
0,8
1,0
0,7 0,8 0,9 1,0 1,1 1,2 1,3 1,4X/<X>
z /H 5Nl/min
10Nl/min20Nl/min40Nl/min60Nl/min100Nl/min140Nl/min180Nl/min
Riv1
0.05
0.0023
Steady state: vertical profilesSteady state: vertical profiles
35x900 mm2 vent (c)
5mm source : toward momentum dominated flow
ICHS 4, San Francisco, California, USA, September 2011
0,0
0,2
0,4
0,6
0,8
1,0
0,7 0,8 0,9 1,0 1,1 1,2 1,3 1,4X/<X>
z /H 5Nl/min
10Nl/min20Nl/min40Nl/min60Nl/min100Nl/min140Nl/min180Nl/min
Riv1
0.05
0.0023
Steady state: vertical profilesSteady state: vertical profiles
35x900 mm2 vent (c)
5mm source : toward momentum dominated flow
Homogeneous for Riv<0.0023
30ICHS 4, San Francisco, California, USA, September 2011
Experimental set-upExperimental set-upExperimental set-upExperimental set-up
Steady state vertical distributionSteady state vertical distribution
Volume fraction variations with the flow Volume fraction variations with the flow raterate
ICHS 4, San Francisco, California, USA, September 2011
0,1
1,0
10,0
100,0
1,E-05 1,E-04 1,E-03 1,E-02
<X>
(%)
Q (m3/s)
Average volume fraction
Volume fraction variations with the flow Volume fraction variations with the flow raterate
Filed symbols: 20mm source
Vent 35x900 mm2 (c)
Vent 180x900 mm2 (a)Vent 180x180 mm2 (b)
Model with CD=0.25
ICHS 4, San Francisco, California, USA, September 2011
0,1
1,0
10,0
100,0
1,E-05 1,E-04 1,E-03 1,E-02
<X>
(%)
Q (m3/s)
Average volume fraction
Volume fraction variations with the flow Volume fraction variations with the flow raterate
Filed symbols: 20mm source
Vent 35x900 mm2 (c)
Vent 180x900 mm2 (a)Vent 180x180 mm2 (b)
Model with CD=0.25
ICHS 4, San Francisco, California, USA, September 2011
0,1
1,0
10,0
100,0
1,E-05 1,E-04 1,E-03 1,E-02
<X>
(%)
Q (m3/s)
Average volume fraction
Volume fraction variations with the flow Volume fraction variations with the flow raterate
Filed symbols: 20mm source
Vent 35x900 mm2 (c)
Vent 180x900 mm2 (a)Vent 180x180 mm2 (b)
Model with CD=0.25
The model over estimate the experimental resultsIn particular for vent (a)
ICHS 4, San Francisco, California, USA, September 2011
0,1
1,0
10,0
100,0
1,E-05 1,E-04 1,E-03 1,E-02
<X>
(%)
Q (m3/s)
Average volume fraction
Volume fraction variations with the flow Volume fraction variations with the flow raterate
Filed symbols: 20mm source
Vent 35x900 mm2 (c)
Vent 180x900 mm2 (a)Vent 180x180 mm2 (b)
Model with CD=0.25
The power law is no longer valid for SOME data
ICHS 4, San Francisco, California, USA, September 2011
0,1
1,0
10,0
100,0
1,E-05 1,E-04 1,E-03 1,E-02
<X>
(%)
Q (m3/s)
Average volume fraction
Volume fraction variations with the flow Volume fraction variations with the flow raterate
Filed symbols: 20mm source
Vent 35x900 mm2 (c)
Vent 180x900 mm2 (a)Vent 180x180 mm2 (b)
Model with CD=0.25
ICHS 4, San Francisco, California, USA, September 2011
0,1
1,0
10,0
100,0
1,E-05 1,E-04 1,E-03 1,E-02
Xm
ax(%
)
Q (m3/s)
Maximum volume fraction
Volume fraction variations with the flow Volume fraction variations with the flow raterate
Filed symbols: 20mm source
Vent 35x900 mm2 (c)
Vent 180x900 mm2 (a)Vent 180x180 mm2 (b)
Model with CD=0.25
ICHS 4, San Francisco, California, USA, September 2011
Maximum volume fraction vs normalized flow rate
0,0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,0 0,5 1,0 1,5 2,0
Xm
ax
Q/Qe
2/10max )( hgXSCQ De
Source flow rate normalized by the expected outflow rate :
i.e. only gravity driven outflow
ModelX=Q/Qe<1
Filed symbols: 20mm source
Event 35x900 mm2
(c)
Event 180x900 mm2
(a)Event 180x180 mm2
(b)
Volume fraction variations with the flow Volume fraction variations with the flow raterate
ICHS 4, San Francisco, California, USA, September 2011
0,0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,0 0,5 1,0 1,5 2,0
Xm
ax
Q/Qe
Filed symbols: 20mm source
Event 35x900 mm2
(c)
Event 180x900 mm2
(a)Event 180x180 mm2
(b)
Maximum volume fraction vs normalized flow rate
Volume fraction variations with the flow Volume fraction variations with the flow raterate
0,1
1,0
10,0
100,0
1,E-05 1,E-04 1,E-03 1,E-02
Xm
ax(%
)
Q (m3/s)
0.3
ICHS 4, San Francisco, California, USA, September 2011
0,0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,0 0,5 1,0 1,5 2,0
Xm
ax
Q/Qe
Filed symbols: 20mm source
Event 35x900 mm2
(c)
Event 180x900 mm2
(a)Event 180x180 mm2
(b)
Maximum volume fraction vs normalized flow rate
Volume fraction variations with the flow Volume fraction variations with the flow raterate
0,1
1,0
10,0
100,0
1,E-05 1,E-04 1,E-03 1,E-02
Xm
ax(%
)
Q (m3/s)
0.3
ICHS 4, San Francisco, California, USA, September 2011
0,0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,0 0,5 1,0 1,5 2,0
Xm
ax
Q/Qe
Filed symbols: 20mm source
Event 35x900 mm2
(c)
Event 180x900 mm2
(a)Event 180x180 mm2
(b)
Maximum volume fraction vs normalized flow rate
Volume fraction variations with the flow Volume fraction variations with the flow raterate
0,1
1,0
10,0
100,0
1,E-05 1,E-04 1,E-03 1,E-02
Xm
ax(%
)
Q (m3/s)
0.3
Purely gravity driven flow through the vent
ICHS 4, San Francisco, California, USA, September 2011
0,0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,0 0,5 1,0 1,5 2,0
Xm
ax
Q/Qe
Filed symbols: 20mm source
Event 35x900 mm2
(c)
Event 180x900 mm2
(a)Event 180x180 mm2
(b)
Maximum volume fraction vs normalized flow rate
Volume fraction variations with the flow Volume fraction variations with the flow raterate
0,1
1,0
10,0
100,0
1,E-05 1,E-04 1,E-03 1,E-02
Xm
ax(%
)
Q (m3/s)
0.3
Additional pressure effects
ICHS 4, San Francisco, California, USA, September 2011
ConclusionsConclusions
Strong vertical stratificationStrong vertical stratification
Highly dependent on the vent geometryHighly dependent on the vent geometry
Source momentum effects : homogeneous layerSource momentum effects : homogeneous layer
Criterion for complete homogeneity still Criterion for complete homogeneity still validvalidHomogeneous model gives fairly good resultsHomogeneous model gives fairly good results
Pressure effects are significant when Q/QPressure effects are significant when Q/Qee>0.3>0.3