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Mechanical and thermal actions of liquid curtains using hydroshield nozzles
J Aerosol ScL Vol. 30, Suppl. 1, pp. $535-$536, [999 © 1999 Published by Elsevier Science Ltd. All rights reserved Printed in Great Britain 0021-8502/99/$ - see front matter
Pergamon
Mechanical and thermal actions of liquid curtains using hydroshield nozzles Malet J., Corieri P., Buchlin J.-M. Von Karman Institute for Fluid Dynamics Environmental and Applied Fluid Dynamics Department Chauss&~ de Waterloo 72 Rhode-Saint-Gen6se, Belgium Phone: +32 2 359 96 22 Fax: +32 2 359 96 00 e-mail: [email protected] Keywords: water droplets, liquid curtains, spray, hydroshield nozzle, dense cloud, mitigation, dispersion Introduction This work shows the applicability of water sprays for industrial applications and environmental protection. Its objective is to evaluate the efficiency of water spray curtains used to mitigate the consequence of accidental releases of toxic and/or flammable gases ~. The curtain is formed by a row of sprays. The mechanical action of the sprays results in gas entrainment and turbulence enhancement, which promote the dilution and the heating of a cloud formed by a toxic cold and dense gas. The mechanical and thermal actions of water spray curtain improve significantly the dispersion of toxic and/or flammable gases in the atmosphere in case of an accidental release. The efficiency of these actions depends on the spray characteristics 3, atmospheric conditions and topography. In former studies 2'4, several nozzles have been investigated to produce the liquid curtain: full-cone spray, hollow cone spray and flat-fan spray nozzles. In this study, the hydroshield nozzles are considered. They produce a spray in a "peacock tail" shape and are often used in the industry to protect people or equipment from radiation caused by an accidental fire. The results obtained with the hydroshield sprays for the heating of a cold dense cloud and the dilution of a toxic gas are presented.
Method The mitigation efficiency of the water spray curtain is evaluated through small-scale experiments conducted in a dedicated wind tunnel. The study is completed with numerical simulations. The water droplet characteristics are first measured in a test facility especially devoted to this purpose 5. Phase Doppler Particle Analyser (PDPA) is used to determine the size distribution and the velocities of the particles in the spray. The wind tunnel called Wind Gallery5 has been designed to simulate wind speed at scale 10 and spray curtain at scale 5. The Wind Gallery is 11.5 m long, 4 m wide and 5 m high. The test section is 1 m high and 1.3 m wide. The air velocity is ranging from 0.25 m/s to 1 m/s. The water spray is placed 3 m downstream of the gas source. To simulate the heavy toxic gas release, a Freon-22 cloud of 15 cm high is formed in the test section. The vertical concentration profiles without and with water curtain working are measured using a hot-wire anemometer especially developed for this purpose. To simulate a cold gas release, an air-nitrogen cloud of 15 cm high is produced at a temperature of-30 or -10 °C. The vertical temperature profiles are obtained with a comb of standard thermocouples. All the concentration and velocity profiles are measured at a location 2.25 m downstream of the spray curtain. The results are obtained in terms of concentration and temperature profiles. Their analysis yields the dilution and warming factors of the initial toxic/cold cloud. These factors are determined by comparing the concentration and temperature profiles in the case of natural dispersion (no spray working) to those measured in the presence of spray curtain pointing upward or downward. Liquid curtains of 20 sprays per meter are used in this study.
$535
S536
Abstracts of the 1999 European Aerosol Conference
Results Dimensionless temperature profiles are plotted for the two different configurations of the curtain and for three wind velocities in figure 1. A normalised temperature equal to 1 and 0 corresponds to the maximal and minimal temperature, respectively).
CURTAIN A OFF-mean --.A.-- ON - UP - 30n. -- ~ DOWN - 30n.
0.8
'
'/
1 ~
CURTAIN ~ OFF - mean - - ' A ' - ON - UP - 30n.
1
--E-
ON - DOWN - 30n.
0.8
I ~
,
0.2, [ o
0
0.2
0.2
'
.
.
. 0.4
.
.
.
0.6
.
.
.
0.8
1
o "x"-
0
-
k/-
0.2
0.4
o
(a)
0.6
0.8
t
o
Co)
Figure 1: Dimensionless temperature profiles without spray curtain (only natural dispersion), with a downward spray curtain and with an upward spray cunair~ Gas source temperature: -10 °C. Wind velocities: (a): 0.25m/s, (b): lm/s.
Figure 1 shows that the downward configuration is more efficient in terms of cloud heating than the upward spray configuration in particular at high wind speed. The smaller efficiency of the upward curtain is explained by the eventual presence of some leakage between the sprays at the ground level just near the injection nozzle. These openings in the curtain let part of the cold dense cloud pass through the curtain without being affected. To get rid of such drawback, a small wall is installed at the ground just upstream the water curtain. The results show a significant enhancement of the heating efficiency. A curtain with 10 nozzles per meter has also been tested. Even though the efficiency of this curtain is reduced compared the previous design, this configuration remains interesting since the water consumption is rather decreased. Experiments with hydroshield nozzles are underway in order to determine their dilution efficiency for toxic cloud release.
References 1. Buchlin J.M. (1994) Mitigation of problem clouds, J. Loss Prey. Process Ind., Voi 7 (2), pp. 167-174 2. Corieri, P., Zimmer L., Moschos M., Buchlin J.-M., Attenuation des cons~uences de rejets accidentels de gaz toxiques et/on inflammables par rideau d'eau. Etude du comportement des jets plats en soufflerie, VKI CR 1998-19. 3.
R•the P. H.• B••ck J. A. ( • 977)• Aer•dynamic behavi•r •f •iquid sprays. •nt. J. Mu•tiphase F••w V••. 3• pp.
263-272 4. St-Georges M., Buchlin J.-M., Riethmuller M. L., Projet CEE EVSV CT 920072 - Contr61e des rejets accidentels par rideau de fluides - rapport final IVK, VK1CR 1996-57 5. St Georges, M., Buchlin, J-M. : (~Detailed Single Spray Experimental Measurements and one-dimensional Modelling >>.Int. J. Multiphase Flow Vol. 20, No. 6, pp979-992, 1994
Pergamon
Mechanical and thermal actions of liquid curtains using hydroshield nozzles Malet J., Corieri P., Buchlin J.-M. Von Karman Institute for Fluid Dynamics Environmental and Applied Fluid Dynamics Department Chauss&~ de Waterloo 72 Rhode-Saint-Gen6se, Belgium Phone: +32 2 359 96 22 Fax: +32 2 359 96 00 e-mail: [email protected] Keywords: water droplets, liquid curtains, spray, hydroshield nozzle, dense cloud, mitigation, dispersion Introduction This work shows the applicability of water sprays for industrial applications and environmental protection. Its objective is to evaluate the efficiency of water spray curtains used to mitigate the consequence of accidental releases of toxic and/or flammable gases ~. The curtain is formed by a row of sprays. The mechanical action of the sprays results in gas entrainment and turbulence enhancement, which promote the dilution and the heating of a cloud formed by a toxic cold and dense gas. The mechanical and thermal actions of water spray curtain improve significantly the dispersion of toxic and/or flammable gases in the atmosphere in case of an accidental release. The efficiency of these actions depends on the spray characteristics 3, atmospheric conditions and topography. In former studies 2'4, several nozzles have been investigated to produce the liquid curtain: full-cone spray, hollow cone spray and flat-fan spray nozzles. In this study, the hydroshield nozzles are considered. They produce a spray in a "peacock tail" shape and are often used in the industry to protect people or equipment from radiation caused by an accidental fire. The results obtained with the hydroshield sprays for the heating of a cold dense cloud and the dilution of a toxic gas are presented.
Method The mitigation efficiency of the water spray curtain is evaluated through small-scale experiments conducted in a dedicated wind tunnel. The study is completed with numerical simulations. The water droplet characteristics are first measured in a test facility especially devoted to this purpose 5. Phase Doppler Particle Analyser (PDPA) is used to determine the size distribution and the velocities of the particles in the spray. The wind tunnel called Wind Gallery5 has been designed to simulate wind speed at scale 10 and spray curtain at scale 5. The Wind Gallery is 11.5 m long, 4 m wide and 5 m high. The test section is 1 m high and 1.3 m wide. The air velocity is ranging from 0.25 m/s to 1 m/s. The water spray is placed 3 m downstream of the gas source. To simulate the heavy toxic gas release, a Freon-22 cloud of 15 cm high is formed in the test section. The vertical concentration profiles without and with water curtain working are measured using a hot-wire anemometer especially developed for this purpose. To simulate a cold gas release, an air-nitrogen cloud of 15 cm high is produced at a temperature of-30 or -10 °C. The vertical temperature profiles are obtained with a comb of standard thermocouples. All the concentration and velocity profiles are measured at a location 2.25 m downstream of the spray curtain. The results are obtained in terms of concentration and temperature profiles. Their analysis yields the dilution and warming factors of the initial toxic/cold cloud. These factors are determined by comparing the concentration and temperature profiles in the case of natural dispersion (no spray working) to those measured in the presence of spray curtain pointing upward or downward. Liquid curtains of 20 sprays per meter are used in this study.
$535
S536
Abstracts of the 1999 European Aerosol Conference
Results Dimensionless temperature profiles are plotted for the two different configurations of the curtain and for three wind velocities in figure 1. A normalised temperature equal to 1 and 0 corresponds to the maximal and minimal temperature, respectively).
CURTAIN A OFF-mean --.A.-- ON - UP - 30n. -- ~ DOWN - 30n.
0.8
'
'/
1 ~
CURTAIN ~ OFF - mean - - ' A ' - ON - UP - 30n.
1
--E-
ON - DOWN - 30n.
0.8
I ~
,
0.2, [ o
0
0.2
0.2
'
.
.
. 0.4
.
.
.
0.6
.
.
.
0.8
1
o "x"-
0
-
k/-
0.2
0.4
o
(a)
0.6
0.8
t
o
Co)
Figure 1: Dimensionless temperature profiles without spray curtain (only natural dispersion), with a downward spray curtain and with an upward spray cunair~ Gas source temperature: -10 °C. Wind velocities: (a): 0.25m/s, (b): lm/s.
Figure 1 shows that the downward configuration is more efficient in terms of cloud heating than the upward spray configuration in particular at high wind speed. The smaller efficiency of the upward curtain is explained by the eventual presence of some leakage between the sprays at the ground level just near the injection nozzle. These openings in the curtain let part of the cold dense cloud pass through the curtain without being affected. To get rid of such drawback, a small wall is installed at the ground just upstream the water curtain. The results show a significant enhancement of the heating efficiency. A curtain with 10 nozzles per meter has also been tested. Even though the efficiency of this curtain is reduced compared the previous design, this configuration remains interesting since the water consumption is rather decreased. Experiments with hydroshield nozzles are underway in order to determine their dilution efficiency for toxic cloud release.
References 1. Buchlin J.M. (1994) Mitigation of problem clouds, J. Loss Prey. Process Ind., Voi 7 (2), pp. 167-174 2. Corieri, P., Zimmer L., Moschos M., Buchlin J.-M., Attenuation des cons~uences de rejets accidentels de gaz toxiques et/on inflammables par rideau d'eau. Etude du comportement des jets plats en soufflerie, VKI CR 1998-19. 3.
R•the P. H.• B••ck J. A. ( • 977)• Aer•dynamic behavi•r •f •iquid sprays. •nt. J. Mu•tiphase F••w V••. 3• pp.
263-272 4. St-Georges M., Buchlin J.-M., Riethmuller M. L., Projet CEE EVSV CT 920072 - Contr61e des rejets accidentels par rideau de fluides - rapport final IVK, VK1CR 1996-57 5. St Georges, M., Buchlin, J-M. : (~Detailed Single Spray Experimental Measurements and one-dimensional Modelling >>.Int. J. Multiphase Flow Vol. 20, No. 6, pp979-992, 1994