Experimental study of the concentration build-up regimes in an enclosure without ventilation

ICHS 4, San Francisco, California, USA, September 2011

Experimental study of the Experimental study of the concentration build-up regimes in concentration build-up regimes in an enclosure without ventilationan enclosure without ventilation

B.CARITEAU, I. TKATSCHENKOCEA Saclay, DEN, DM2S, SMFE, LEEF


U0,

V

X(z)?

Dispersion in an enclosure without ventilation


A wide range of injection velocity

U0,

V

X(z)?



A wide range of injection velocity

U0,

V

X(z)?

U0Buoyancy dominated dispersion

Momentum dominated dispersion



Volume Richardson number:

U0Buoyancy dominated dispersion


Cleaver et. al. (1994, J. Hazardous Mater. Vol. 36) 200

031

UVgRi a

v



RivBuoyancy dominated dispersion


Cleaver et. al. (1994, J. Hazardous Mater. Vol. 36) 200

031

UVgRi a

v





Cleaver et. al. (1994, J. Hazardous Mater. Vol. 36)

1

200

031

UVgRi a

v






1

Stratified

0

0,2

0,4

0,6

0,8

1

0 10 20

z/H

X/X*

t Worster & Huppert (1984, J. Fluid. Mech. Vol. 132)

time

200

031

UVgRi a

v






1

Stratified

0

0,2

0,4

0,6

0,8

1

0 10 20

z/H

X/X*


time21

0

vRiRd

dH

Homogeneous layer

200

031

UVgRi a

v





200

031

UVgRi a

v


1

Stratified

0

0,2

0,4

0,6

0,8

1

0 10 20

z/H

X/X*


RiVc

time21

0

vRiRd

dH

Homogeneous layer

Fully homogeneous

Hd


Goals of the present experiments:



1

Stratified

0

0,2

0,4

0,6

0,8

1

0 10 20

z/H

X/X*


RiVc

time21

0

vRiRd

dH

Homogeneous layer

Fully homogeneous

Hd



Buoyancy dominated dispersion

0

0,2

0,4

0,6

0,8

1

0 10 20

z/H

X/X*


RiVc

time21

0

vRiRd

Hd

Riv

1


Stratified

dH

Homogeneous layer

Fully homogeneous

Check the existence of these regimes




1 RiVc

Hd

Stratified

dH

Homogeneous layer

Fully homogeneous

0

0,2

0,4

0,6

0,8

1

0 10 20

z/H

X/X*


time21

0

vRiRd


Check the validity of existing models


21

0

vRiRd

time

Buoyancy dominated dispersion

Stratified

dH

Homogeneous layer

0

0,2

0,4

0,6

0,8

1

0 10 20

z/H

X/X*



Riv

1 RiVc

Hd

Fully homogeneous


Give a criterion for fully homogenous regime

15ICHS 4, San Francisco, California, USA, September 2011

Experimental set-upExperimental set-up

Dispersion for RiDispersion for Rivv>1 : >1 : Buoyancy dominated regimeBuoyancy dominated regime

Dispersion for RiDispersion for Rivv<1 : <1 : Homogeneous layer formationHomogeneous layer formation

Dispersion for RiDispersion for Rivv<<1 : <<1 : Criterion for fully homogeneous Criterion for fully homogeneous

dispersion dispersion


Experimental setup and injection Experimental setup and injection conditionsconditions

Working gases : Helium and Air

Injection tube

930m

m

930mm

1260

mm

Top view

Side view

10mm hole

V=1,1m3



Source :

D0=5mm or 20mmX0=60%, 80% or 100% heliumQ0=1 to 350Nl/min


Injection tube

930m

m

930mm

1260

mm

Top view

Side view

10mm hole

V=1,1m3



Source :

D0=5mm or 20mmX0=60%, 80% or 100% heliumQ0=1 to 350Nl/min

Ri0=5.6 10-6 to 200Riv=2.3 10-3 to 20000

20

0

0

00 U

RgRi a

Injection tube

930m

m

930mm

1260

mm

Top view

Side view

10mm hole

V=1,1m3




Injection tube

930m

m

930mm

1260

mm

Top view

Side view

10mm hole

V=1,1m3

Local helium volume fraction measurement : Mini-Katharometers



Injection tube

930m

m

930mm

1260

mm

Top view

Side view

10mm hole

V=1,1m3

Heat conductivity measurement

7mm




100mm

220mm

340mm

460mm

580mm

700mm

820mm

940mm

1060mm

1140mm

Injection tube

mini-katharometers

300mm

580mm

180m

m35

0mm

930m

m

930mm

1260

mm

Top view

Side view

10mm hole

V=1,1m3

Heat conductivity measurement

7mm



0

0,2

0,4

0,6

0,8

1

0 5 10 15 20 25 30

X/X*

z/H

5t*10t*20t*

Source : D=20mm, Riv=3 to 20000

Comparison with Worster & Huppert (1983) model.

Dispersion for RiDispersion for Rivv>1 : Buoyancy dominated regime>1 : Buoyancy dominated regime

Volume fraction vs height and time


0

0,2

0,4

0,6

0,8

1

0 5 10 15 20 25 30

X/X*

z/H

5t*10t*20t*



31

32

34

32

0

*

4 BHAt

0

0*35

34

32

32

4 gHBX

Characteristic time and volume fraction:




0

0,2

0,4

0,6

0,8

1

0 5 10 15 20 25 30

X/X*

z/H

5t*10t*20t*



31

32

34

32

0

*

4 BHAt

0

0*35

34

32

32

4 gHBX




The entrainement coefficient


0

0,2

0,4

0,6

0,8

1

0 5 10 15 20 25 30

X/X*

z/H

5t*10t*20t*



31

32

34

32

0

*

4 BHAt

0

0*35

34

32

32

4 gHBX





Tuned between 0.065 and 0.04


0

0,2

0,4

0,6

0,8

1

0 5 10 15 20 25 30

X/X*

z/H

5t*10t*20t*



31

32

34

32

0

*

4 BHAt

0

0*35

34

32

32

4 gHBX





Tuned between 0.065 and 0.04

Source Ri0 from 0.03 to 200




0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 20 40 60 80

X/X*

z/H

Q=1Nl/minQ=2Nl/minQ=3Nl/minQ=4Nl/minQ=5Nl/min

t/t*=10 t/t*=20 t/t*=40Volume fraction vs height and time

Entrainement coefficient : 0.1


Worster et Huppert (1983) model

0

0,2

0,4

0,6

0,8

1

0 5 10 15 20 25

X/X*

z/H

t/t*=10t/t*=5 t/t*=20



0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 20 40 60 80

X/X*

z/H


t/t*=10 t/t*=20 t/t*=40Volume fraction vs height and time

Entrainement coefficient : 0.1


Vertical volume fraction profiles, D=5mm source

0,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 1,8 2,0X/<X>

z/H


At t=10, with QV100

Riv 0.00520.00750.0251.5 3

Dispersion for RiDispersion for Rivv<1 : Homogeneous layer formation<1 : Homogeneous layer formation


100

1000

0,001 0,01 0,1 1Riv

d/R

0

Xo=100%Xo=60%Xo=80%

Thickness of the homogeneous layer vs Riv

vRiRd 25

0

Dispersion for RiDispersion for Rivv<1 : Homogeneous layer formation<1 : Homogeneous layer formation


0

5

10

15

20

25

30

35

40

45

0 50 100 150 200

X (%

)

t (s)

0,1m0,22m0,34m0,46m0,58m0,70m0,82m0,94m1,06m1,14m

Local time variations of the volume fraction D=5mm, Riv=0.0023

Dispersion for RiDispersion for Rivv<<1 : <<1 : Criterion for fully homogeneous Criterion for fully homogeneous dispersion dispersion


Experimental critical values of Riv to reach

homogeneity

X0 (%) Riv100 0.002380 0.003560 0.0038

Critical value derived from the Cleaver et. al. (1994) correlation for the actual enclosure :

Riv = 0.0025

Dispersion for RiDispersion for Rivv<<1 : <<1 : Criterion for fully homogeneous Criterion for fully homogeneous dispersion dispersion


ConclusionsConclusions

The 3 regimes have been identified with respect to the The 3 regimes have been identified with respect to the volume Richardson numbervolume Richardson number Buoyancy dominated regime occurs for RiBuoyancy dominated regime occurs for Rivv>1>1 For RiFor Rivv>1, Worster & Huppert model fits fairly well with >1, Worster & Huppert model fits fairly well with the 20mm sourcethe 20mm source For RiFor Rivv>1, the 5mm source gives unexpected results with >1, the 5mm source gives unexpected results with much higher maximum volume fractionmuch higher maximum volume fraction For RiFor Rivv<1, formation of a homogeneous layer is observed, <1, formation of a homogeneous layer is observed, it sickness follows the Cleaver et. al. correlation only for it sickness follows the Cleaver et. al. correlation only for RiRivv<0.01<0.01 The Cleaver et. al. correlation can be extended to give a The Cleaver et. al. correlation can be extended to give a good critical value of the volume Richardson number below good critical value of the volume Richardson number below which the volume fraction is fully homogeneouswhich the volume fraction is fully homogeneous

Experimental study of the concentration build-up regimes in an enclosure without ventilation

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