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The Use of a Water Mist Curtain as a Radiation Shield

Martin, Daniel LU (2015) In LUTVDG/TVBB VBRM05 20151
Division of Fire Safety Engineering
Abstract
Water mist systems have seen an increase in use as an alternative clean agent fire suppressant since the late 1980s after the use of Halon gases were discontinued. One of the potential uses of these systems is to provide a protective curtain between a fire and desired target. The following experimental work investigates the radiation attenuation abilities of a single water mist spray. These experimental results are the first ever conducted with high pressure water mist. Two sources of heat flux were utilized: radiant panel and diffusion flame line burner. Radiation levels were measured along the normal propagation path and at an angle of ±5º above and below the normal in the vertical plane. Attenuation levels were found to be greater than... (More)
Water mist systems have seen an increase in use as an alternative clean agent fire suppressant since the late 1980s after the use of Halon gases were discontinued. One of the potential uses of these systems is to provide a protective curtain between a fire and desired target. The following experimental work investigates the radiation attenuation abilities of a single water mist spray. These experimental results are the first ever conducted with high pressure water mist. Two sources of heat flux were utilized: radiant panel and diffusion flame line burner. Radiation levels were measured along the normal propagation path and at an angle of ±5º above and below the normal in the vertical plane. Attenuation levels were found to be greater than 40% for all locations 300+ mm below the nozzle. Initially the attenuation is high near the nozzle, decreases in intensity until 200 mm, rises again until the 500 mm mark, and then experiences a slight decrease below 500 mm. This S-curve shaped attenuation distribution is attributed to the droplet size, volumetric water concentration, and residency time of the droplets. Water mist curtains can be an effective way of protecting high value targets from radiation. (Less)
Popular Abstract
Daniel A. Martin, “The Use of a Water Mist Curtain as a Radiation Shield”
IMFSE Master’s Thesis, Lund University Spring 2015
Popular Science Summary
Can a curtain of tiny water droplets block the dangerous, invisible radiation produced by a fire? It was found that small water droplets that are generated at high pressures can block 40% - 95% of the radiation from a heat source. Droplets of the smallest size are the best at blocking the radiation. As the droplets grow in size further and further away from the nozzle, the percentage of blocking decreases. Once the droplets reach a diameter that is a factor of 10 larger than the radiation wavelength, the blocking percentage increases to a maximum. Below that point, the droplets get even... (More)
Daniel A. Martin, “The Use of a Water Mist Curtain as a Radiation Shield”
IMFSE Master’s Thesis, Lund University Spring 2015
Popular Science Summary
Can a curtain of tiny water droplets block the dangerous, invisible radiation produced by a fire? It was found that small water droplets that are generated at high pressures can block 40% - 95% of the radiation from a heat source. Droplets of the smallest size are the best at blocking the radiation. As the droplets grow in size further and further away from the nozzle, the percentage of blocking decreases. Once the droplets reach a diameter that is a factor of 10 larger than the radiation wavelength, the blocking percentage increases to a maximum. Below that point, the droplets get even larger and the radiation blocking decreases again. The blocking percentage of the spray, as you move away from the nozzle, follows the same trend as the amount or concentration of water within the spray. Close to the nozzle the spray is narrow and contains a lot of water and greater blocking. Further away from the nozzle the spray gets wider and the concentration decreases and the blocking decreases. At 30 cm below the nozzle, the spray width becomes constant. The concentration of water at this point begins to increases and so does the amount of radiation blocked by the mist curtain. Two different gas burning heat sources were used to create the radiation measured in this
project: a radiation panel and a straight line flame. Between the two radiation sources, the water mist was more efficient in blocking the radiation from the flame compared to the radiant panel. This is due to the fact that the radiation from the flame has several different radiation wavelength sizes that can be absorbed better since the mist has several different droplet sizes within it.
Laboratory experiments were designed and conducted in order to understand how a water mist curtain can block the dangerous radiation from a fire. Several previous studies have looked at water mist curtains supplied with low pressure and high water flow. These tests are the first to investigate the radiation blocking ability of a high pressure (100 bar), low water flow water mist curtain.
These results will not only benefit the scientific community, but building safety designers all over the world. This work provides a broad approach to understanding the complex scattering and absorbing capabilities of water mist curtains. Every day, people are looking for economical, low cost, and efficient ways of protecting their interests. It is the author’s opinion that water mist
curtains can be an excellent method of stopping the fire from spreading from compartment to compartment and save lives and property. This work can be used as a stepping stone for future research projects in the private sector and academic fields; both experimental and computer simulations studies. Also, these results
provide vital information to fire protection engineers in regards to system effective as they look to implement water mist curtains into their building designs to protect people and property. (Less)
Please use this url to cite or link to this publication:
author
Martin, Daniel LU
supervisor
organization
course
VBRM05 20151
year
type
H2 - Master's Degree (Two Years)
subject
keywords
water curtain, radiation attenuation, water mist, radiation
publication/series
LUTVDG/TVBB
report number
5497
other publication id
LUTVDG/TVBB—5497--SE
language
English
id
5431385
date added to LUP
2015-05-25 13:58:44
date last changed
2015-05-25 13:58:44
@misc{5431385,
  abstract     = {Water mist systems have seen an increase in use as an alternative clean agent fire suppressant since the late 1980s after the use of Halon gases were discontinued. One of the potential uses of these systems is to provide a protective curtain between a fire and desired target. The following experimental work investigates the radiation attenuation abilities of a single water mist spray. These experimental results are the first ever conducted with high pressure water mist. Two sources of heat flux were utilized: radiant panel and diffusion flame line burner. Radiation levels were measured along the normal propagation path and at an angle of ±5º above and below the normal in the vertical plane. Attenuation levels were found to be greater than 40% for all locations 300+ mm below the nozzle. Initially the attenuation is high near the nozzle, decreases in intensity until 200 mm, rises again until the 500 mm mark, and then experiences a slight decrease below 500 mm. This S-curve shaped attenuation distribution is attributed to the droplet size, volumetric water concentration, and residency time of the droplets. Water mist curtains can be an effective way of protecting high value targets from radiation.},
  author       = {Martin, Daniel},
  keyword      = {water curtain,radiation attenuation,water mist,radiation},
  language     = {eng},
  note         = {Student Paper},
  series       = {LUTVDG/TVBB},
  title        = {The Use of a Water Mist Curtain as a Radiation Shield},
  year         = {2015},
}