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I denna studie har det utforskats skillnader mellan två olika typer av brandsläckningssystem:traditionella vattensprinklersystem och högtrycksvattendimma med avseende påbrandskyddsegenskaper samt miljö och hållbarhetsaspekterna. Syftet med denna studie är attförbättra förståelsen av de två olika systemen och dess användning för brandbekämpning.Traditionella vattensprinklersystem visade sig erbjuda effektiv branddetektion och respons tackvare värmekänsliga glasbulber och var särskilt effektiva i stora öppna utrymmen. Dessutomframstod dessa två vattensprinklersystemen som mycket lämpliga för miljöer med hög fibrositetsom till exempel sågverk.Högtrycksvattendimma erbjuder flera fördelar, såsom tidig branddetektion och respons, samt enmer effektiv brandsläckningsförmåga. Systemet använder små vattendroppar som avges medhögt tryck, vilket skapar en större täckningsyta och leder till upp till 90% mindrevattenanvändning. Detta minskar risken för vattenskador och gör systemet särskilt lämpligt föranvändning i trånga utrymmen och för skydd av objekt som Li-jonbatterier, samt i de flestaandra miljöer med undantag för dem där material med hög fibrositet förekommer.Miljömässigt visade sig vattendimma vara överlägsen utifrån flera olika aspekter. Det gällermindre vattenanvändning vilket därmed leder till mindre miljöfarligt brandvatten som behöverhanteras efter brandsläckning. Det uppnås även högre energieffektivitet och därmed lägrekoldioxidutsläpp på grund av att pumpen inte behöver hantera lika mycket vatten som med etttraditionellt sprinklersystem. Högtrycksvattendimma bidrar även till förbättrad luftkvalitet föratt den fokuserar på att bekämpa de farliga brandgaserna.Sammanfattningsvis har denna studie bidragit med viktiga insikter och analytiska slutsatser,som erbjuder en förstärkt förståelse av de jämförda brandskyddssystemen. Analyserna påvisaratt både högtrycksvattendimma och traditionella vattensprinklersystem har sina specifikafördelar beroende på deras tillämpningsom, This study explores differences between two types of fire suppression systems: traditional watersprinkler system and high-pressure water mist system from the perspective of fire protection aswell as environmental properties. The purpose of this study is to gain a deeper understanding ofthese two systems and their use for fire protection.Traditional water sprinkler systems systems showed to offer effective fire detection and quickresponse thanks to heat-sensitive glass bulbs. It was also particiularly more effective in largeopen spaces. Traditional water sprinklers have also appeared to be effective for enfironmentswith high fibrosity, such as sawmills.High-pressure water has shown several advantages, such as early fire detection and responsetime, as well as a more efficient fire extinguishing capacity. The system uses small waterdroplets discharged at high pressure, which creates a larger coverage area and leads to up to90% less water usage. This reduces the risk of water damage and makes the system particularlysuitable for use in confined spaces and for protecting objects like lithium-ion batteries, as wellas in most other environments except those with high fibrosity.From an environmental perspective, water mist proved to be superior from several aspects. Thisincludes reducing water usage, which leads to less, environmentally hazardous firewater, thatneeds to be managed after extinguishing a fire. Higher energy efficiency is also achieved,resulting in lower carbon dioxide emissions because the pump does not need to handle as muchwater as a traditional sprinkler system. High-pressure water mist also contributes to improvedair quality by suppressing hazardous fire gases.In conclusion this study has shown important insights and conclusions, offering a betterunderstanding of the compared fire protection systems. The analyses indicate that both high-pressure water mist and traditional water sprinkler systems have their specific advantagesdepending on their usage areas.

I denna studie har det utforskats skillnader mellan två olika typer av brandsläckningssystem:traditionella vattensprinklersystem och högtrycksvattendimma med avseende påbrandskyddsegenskaper samt miljö och hållbarhetsaspekterna. Syftet med denna studie är attförbättra förståelsen av de två olika systemen och dess användning för brandbekämpning.Traditionella vattensprinklersystem visade sig erbjuda effektiv branddetektion och respons tackvare värmekänsliga glasbulber och var särskilt effektiva i stora öppna utrymmen. Dessutomframstod dessa två vattensprinklersystemen som mycket lämpliga för miljöer med hög fibrositetsom till exempel sågverk.Högtrycksvattendimma erbjuder flera fördelar, såsom tidig branddetektion och respons, samt enmer effektiv brandsläckningsförmåga. Systemet använder små vattendroppar som avges medhögt tryck, vilket skapar en större täckningsyta och leder till upp till 90% mindrevattenanvändning. Detta minskar risken för vattenskador och gör systemet särskilt lämpligt föranvändning i trånga utrymmen och för skydd av objekt som Li-jonbatterier, samt i de flestaandra miljöer med undantag för dem där material med hög fibrositet förekommer.Miljömässigt visade sig vattendimma vara överlägsen utifrån flera olika aspekter. Det gällermindre vattenanvändning vilket därmed leder till mindre miljöfarligt brandvatten som behöverhanteras efter brandsläckning. Det uppnås även högre energieffektivitet och därmed lägrekoldioxidutsläpp på grund av att pumpen inte behöver hantera lika mycket vatten som med etttraditionellt sprinklersystem. Högtrycksvattendimma bidrar även till förbättrad luftkvalitet föratt den fokuserar på att bekämpa de farliga brandgaserna.Sammanfattningsvis har denna studie bidragit med viktiga insikter och analytiska slutsatser,som erbjuder en förstärkt förståelse av de jämförda brandskyddssystemen. Analyserna påvisaratt både högtrycksvattendimma och traditionella vattensprinklersystem har sina specifikafördelar beroende på deras tillämpningsom, This study explores differences between two types of fire suppression systems: traditional watersprinkler system and high-pressure water mist system from the perspective of fire protection aswell as environmental properties. The purpose of this study is to gain a deeper understanding ofthese two systems and their use for fire protection.Traditional water sprinkler systems systems showed to offer effective fire detection and quickresponse thanks to heat-sensitive glass bulbs. It was also particiularly more effective in largeopen spaces. Traditional water sprinklers have also appeared to be effective for enfironmentswith high fibrosity, such as sawmills.High-pressure water has shown several advantages, such as early fire detection and responsetime, as well as a more efficient fire extinguishing capacity. The system uses small waterdroplets discharged at high pressure, which creates a larger coverage area and leads to up to90% less water usage. This reduces the risk of water damage and makes the system particularlysuitable for use in confined spaces and for protecting objects like lithium-ion batteries, as wellas in most other environments except those with high fibrosity.From an environmental perspective, water mist proved to be superior from several aspects. Thisincludes reducing water usage, which leads to less, environmentally hazardous firewater, thatneeds to be managed after extinguishing a fire. Higher energy efficiency is also achieved,resulting in lower carbon dioxide emissions because the pump does not need to handle as muchwater as a traditional sprinkler system. High-pressure water mist also contributes to improvedair quality by suppressing hazardous fire gases.In conclusion this study has shown important insights and conclusions, offering a betterunderstanding of the compared fire protection systems. The analyses indicate that both high-pressure water mist and traditional water sprinkler systems have their specific advantagesdepending on their usage areas.

Concern about PFAS containing foam fire suppression agents’ negative environmental impact motivated the U.S. Air Force to perform a two-phase feasibility analysis of water mist systems for protection of aircraft hangars. Phase I involved a feasibility analysis of COTS water mist technologies based on manufacturer specifications, literature, and previous test data. Phase I identified seven manufacturers who have developed systems with potential for successful protection of aircraft hangars. Phase II used FDS to model two low pressure and one high pressure system identified in Phase I. Phase II completed an analysis and validation simulations of the Lagrangian particle, extinction, and evaporation model in FDS. Following validation simulations each nozzle was tested in a full-scale hangar configuration for protection of a JP-8 spill fire. The results found the high-pressure mist system was able to extinguish the fire and earlier activation times lead to less damage to the aircraft and hangar compartment.

Demands to increase the safety and reliability of the modern nuclear reactors are constantly being made. Typical demands include the increases the thermal performance of the passive heat removal system PHRS by removing larger amounts of energy and applied a technique that leads to reduce size and weight of the PHRS unit. This article presents an experimental investigation on the natural convection based on alternative cooling approach using water mist. The results obtained from the related experimental work indicated that the heat transfer rate was enhanced over that for the airflow as a result of water mist evaporation on the surface of the tubes. The Nu number increases by about 148%, 144%, and 128% respectively for all tube rows compared with airflow. The experimental results of the thermal performance factor values obtained by suspended water mist were correlated as functions of Rayleigh number (Ra) and Weber number (We). Subsequently, the predicted thermal performance factor from the correlation was plotted to compare with the experimental data. It was found that the thermal performance factor was within ±11%. © 2020 PENERBIT AKADEMIA BARU.

Modern, commercial water mist fire protection system technology evolved at the beginning of the 1990s due a need to replace halon fire-extinguishing systems and improve fire safety on passenger ships. This thesis documents the unknown water mist system development work by two Swedish companies during the 1970s and 1980s. It also documents the development of the first international installation recommendations and fire test procedures for marine applications.Several of these fire test procedures needed revisions. A research project in the thesis showed that those for machinery space protection can be significantly improved by using simple and inexpensive measurements and performance measurement parameters. In another research project, tests simulating fire on a ro-ro cargo space of a ship was conducted. The results indicate that large water droplets are required for fire suppression, but smaller water droplets cool the fire gases well. For the protection of heritage buildings, a field study suggests that functional testing is essential to maintain the function of a system. Testing using commercial nozzles indicate that exposure of sensitive wall paintings to water spray could cause significant damage under real-life conditions, even if the flow rate is low.Future research should focus on improving fire test procedures based on experience as well on a theoretical understanding of the mechanisms of water mist. Long-term field experience is also desired for continual improvements of the performance and reliability of systems. In order to convince authorities, insurers, fire protection consultants and end-users on using water mist, these issues need to be dealt with in a systematic manner.

This paper reports the preparation and fire-suppression efficiency of oil-in-water microemulsions containing ferrocene. In this work, oil-in-water emulsions containing 0–1000 ppm ferrocene and four surfactants (Surfynol 465, Olfin E1020, Triton X-100 (TX), and Noigen TDS-80 (NT)) were prepared by homogenizing n-octane solutions of ferrocene and aqueous surfactant solutions at ambient temperature. Four emulsion parameters were then characterized: emulsion stability, oil-droplet size in emulsion, flash point, and capability of extinguishing n-heptane pool fires. Emulsion stability experiments and droplet-size measurements clearly demonstrated that the oil-in-water emulsions containing ferrocene and TX/NT were thermodynamically stable microemulsions. Flash-point measurements confirmed that no oil-in-water microemulsions tested ignited below 93 °C. Suppression trials involving microemulsions containing 0–1000 ppm ferrocene and NT revealed the relationship between their fire suppression efficiency and the concentrations of ferrocene and NT, and also demonstrated that the microemulsions tested in this study have a higher ability to suppress pool fires compared with a conventional wet chemical agent.

This report analyzes fire extinguishing solutions that might cut time between fire alarm and fire extinguishing at the European Spallation Source. A special design fire with a very high peak heat release rate is used. The method used includes a literature study, meetings with supervisors and ESS representatives and participation in workshops and study visits. Some fire protection measures are already planned, but additional measures are investigated, namely automatic fire extinguishing systems and manual fire suppression. The conclusion of the report is that the time aspect is crucial and that combining different local automatic extinguishing systems with an on- site First Responder team might save crucial time. The team should be educated in firefighting, equipped with several fire suppression systems and have the possibility to use positive pressure ventilation. Also, some improvements for an intervention by the municipal fire brigade are presented.

This report analyzes fire extinguishing solutions that might cut time between fire alarm and fire extinguishing at the European Spallation Source. A special design fire with a very high peak heat release rate is used. The method used includes a literature study, meetings with supervisors and ESS representatives and participation in workshops and study visits. Some fire protection measures are already planned, but additional measures are investigated, namely automatic fire extinguishing systems and manual fire suppression. The conclusion of the report is that the time aspect is crucial and that combining different local automatic extinguishing systems with an on- site First Responder team might save crucial time. The team should be educated in firefighting, equipped with several fire suppression systems and have the possibility to use positive pressure ventilation. Also, some improvements for an intervention by the municipal fire brigade are presented.

An experimental study of water mist fire suppression in a buoyant, turbulent diffusion flame is presented. An existing turbulent line burner facility was modified to allow for water mist suppression. These modifications include streamlining the oxidizer delivery system, facility improvements to increase mist generation efficiency, as well as the addition of a mist containment system and an enhanced exhaust flow to homogenize the water mist in the flame region and reduce secondary flows. Following these improvements, the capabilities of the water mist generation system were characterized both using a classical mass balance approach and using more modern advanced diagnostic techniques. The turbulent line burner facility fitted with the water mist improvements were applied to suppress a 50 kW methane flame. Species-based calorimetry was used to evaluate the global heat release rate and combustion efficiency to evaluate suppression behavior. Detailed local measurements of flame temperature were also performed and provide a useful data set for the evaluation of flame suppression response and for the validation of CFD fire models.

Current legislation regarding implementation of water mist system(s) requires full scale testing specific to its intended use which involves extensive funding that discourages potential users. This motivates the desire for accurate water mist simulation. The extent to this possibility is studied for a specific high pressure water mist system, “Danfoss 1910”, and its effect on controlled fires of different heat release rates were studied. Concepts to accurately simulate the water mist system were also looked into, where the combined use of an additional air inlet, obstruction (turbulence) meshes and reduced initial particle velocity showed the best performance. A horizontal water mist orientation was adopted to reduce the direct interaction between water mist spray and buoyant plumes. The results attained from a quasi steady state extinguishment model, simulations and experimental data were compared and vast discrepancies were discovered. The quarter scale ISO room corner used was found to be too small which created high levels of circulation within the enclosure; hindering the proper assessment of extinguishing mechanisms such as gas phase cooling and oxygen depletion. One of the conclusions is the need to compile larger scale tests validation data to form a baseline reference., This project identifies the extent of water mist simulation accuracy and its effect on a controlled fire. The largest hindrance to utilising the full potential of water mist systems is the uncertainty in its simulation accuracy. Here, several simulation concepts were tested and an accurate simulation of a specific water mist system was achieved. These results would hopefully contribute to the long term goal to reduce the dependency of full scale testing for water mist applications. Various scenarios to study several factors were first identified, these factors include; accurate simulation of water mist spray (in relation to velocity profile at predetermined distances from nozzle), water distribution accuracy and extinguishment predictions using simulation. In the recent decade, simulation accuracy of water mist sprays in the Computational Fluid Dynamic (CFD) simulation software used (Fire Dynamics Simulator, FDS) has drastically improved where the concept of momentum lost is better captured which in turn improves the water distribution prediction. Several combinations of simulation concepts including the use of additional air inlets, obstruction meshes and reducing the particles’ initial velocity were looked into. The best suited concept was then identified by comparing accuracy with experimental test data of velocity profiles previously performed by Husted for his doctorate study submitted in 2007. Having a spectrum of water mist characteristics, the best suited concept found here is limited to the particular model of water mist nozzle used for this project (Danfoss 1910). However, the simulation accuracy is reduced when enclosure effects are introduced which can be attributed to the lack of computational model between the relationship of turbulence effect and water particle size. This likely affected the water distribution accuracy within the enclosure seen in one of the scenarios where high circulation levels were observed. The simulation’s extinguishment predict

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., 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 a

This work investigates crew opinions about manual intervention on board submarines and planned new solutions on the new submarine, the A26. The planned solutions include an unmanned aft and the installation of water mist instead of Halon 1301 as fire suppression system. Literature, survey and interviews were used to gather information. The crew routines and previous fire incidents were determined. The survey shows that many crew members have not experienced fire on board and that in many cases they start a manual intervention later than as prescribed in the regulations. Interviews and survey show that the crew is sceptical towards the planned changes but that information could change this. This work has contributed to the design and construction of the next Swedish submarine, the A26.

The effects water mist has on the overpressures produced by the detonation of 50 lb equivalent of high explosives (HE) TNT, Destex, and PBXN-109 in a chamber is reported. The overpressures for each charge density were measured with and without mist preemptively sprayed into the space. The impulse, initial blast wave, and quasi-static overpressure measured in the blast mitigation experiments were reduced by as much as (40%, 36%, and 35%) for 50 lbs TNT, (43%, 25%, and 33%) for 50 lbs TNT equivalent Destex, and (49%, 39%, and 41%) for 50 lbs TNT equivalent PBXN-109 when water mist was sprayed 60 seconds prior to detonation at a concentration of 70 g/m sup3 and droplet Sauter Mean Diameter (SMD) of 54 micrometer. These results suggest that current water mist technology is a potentially promising concept for the mitigation of overpressure effects produced from the detonation of high explosives., The original document contains color images. Prepared in cooperation with Hughes Associates, Inc., Baltimore, MD, Naval Surface Warfare Center, Indian Head, MD and Marioff, Inc., Linthicum, MD.

This report evaluates an existing method for testing water mist systems - CEN/TS 14972:2008. Annex A.3. The evaluation is to be seen as an analysis of the uncertainties with respect to repeatability and reproducibility of the test. It is concluded that the test method does not meet the standards required to become an EN-standard in its present form. A new concept is presented and verified, bot theoretically and experimentally. This report is to be seen as one step out of many to make the test method acceptable for its purpose.

This report evaluates an existing method for testing water mist systems - CEN/TS 14972:2008. Annex A.3. The evaluation is to be seen as an analysis of the uncertainties with respect to repeatability and reproducibility of the test. It is concluded that the test method does not meet the standards required to become an EN-standard in its present form. A new concept is presented and verified, bot theoretically and experimentally. This report is to be seen as one step out of many to make the test method acceptable for its purpose.

Computations are performed to examine the effectiveness of mono-disperse water droplets in extinguishing a co-flow, propane diffusion flame by injecting the droplets into the air stream. The calculations show that the droplets entrained into the reaction kernel at the flame base are crucial for extinction. The reaction kernel detaches from the burner rim and blows-off when the droplet concentration is increased to a critical value (extinction concentration). At the critical value, the maximum chain-branching reaction (H2+O=OH+H) rate in the reaction kernel was found to be reduced by a factor of 5 in our computations. A large decrease in the reaction rate indicates that the maximum heat generations rate and Damkholer number are too low to sustain the flame, and cause the flame blow-off. Large drops are more effective than small drops, and the extinction concentration of water increases from 10.5% to 15% by mass as the size is reduced from 32 to 4 micro m. As the droplet size is increased further (>32 micro m), the trend will reverse as the evaporation rates get too small despite increased penetration of flame core by the drops., The original document contains color images.

The use of water mist for fire extinguishment has increased rapidly in recent years. The main reason is the abandonment of halon-based extinguishing systems in favour of environmentally friendlier systems. Furthermore the use of water mist systems has spread from mainly marine applications to also include the protection of buildings. The main problem in this regard is to verify the effectiveness of the system. At present time this can only by done by full-scale tests. This is however expensive and in some cases also unrealistic and expensive when it comes to water mist systems for buildings. The aim of this thesis is to provide experimental data that can serve as a basis for simulations of the interaction of water mist and a fire and to demonstrate that CFD can predict the performance of a water mist system. The physics of water mist systems has been studied by theoretical considerations as well as experimental work. Measurements of droplet velocities, diameters and volumetric water distribution were carried out on the spray from a high-pressure system of 100 bars. Experiments have been conducted on a hollow cone nozzle without fire and with fire, as well as a full cone nozzle without fire. Relevant measurement results were obtained with Phase Doppler Anemometry and Particle Image velocimetry as well as Laser Tomography and High Speed camera. Suggestions were made for improvement of the water density apparatus. The measurements have been the basis for simulations of water mist with CFD. Initial simulations involving the complex zone around the nozzle resulted in droplets with radial velocities and insufficient transfer of momentum to the air. A new approach has been used for the simulations with the LES model in FDS 4.07. In this approach the simulations of the water mist spray is not done in the zone close to the nozzle. Instead the boundary conditions are set further downstream, based on the conducted measurements. This approach resulted in droplets and air moving

The costs associated with personnel and maintenance account for approximately 70% of the total operating costs of a ship. Of these costs more than 50% are associated with personnel. As the Canadian Forces have made the reduction of the total operating costs of ships a priority, approaches to the reduction in crewing levels without jeopardizing operational capabilities and safety are being investigated. Of particular concern is how labour intensive tasks, such as damage and fire control, can be carried out on ships with reduced crewing levels. To aid in addressing the challenges arising from attempts to reduce crewing levels and maintain or enhance damage control, DRDC Atlantic initiated a project entitled Damage Control and Crew Optimization. This project has several objectives including a state-of-the-art review of damage and fire control technologies, modeling and simulation of damage control activities and the evaluation of how automation will affect crewing levels required to maintain damage and fire control capabilities, identification of materials with enhanced damage and fire resistance, and the evaluation and demonstration of wireless condition monitoring systems In this memorandum the literature pertinent to developments in damage and fire control technologies that have the potential to allow reduced crewing while maintaining damage control capabilities has been reviewed. The technologies include damage control systems, fire and damage sensors, fire suppression agents and techniques such as water mist, gaseous agents and aqueous fire fighting foams, smart valves, ventilation control and fire hardened materials. In addition, specifications for and manufacturers/vendors of fire and damage control systems and hardware are reviewed.

We report a modeling study to understand the observed suppression behavior of 14-, 30-, and 42-um-diameter water drops on propane-air non-premixed counterflow flames. The model employed is a hybrid Eulerian-Lagrangian formulation for treating the interaction of drops and counterfiow non-premixed flames. For treatment of the propane chemical kinetics, a skeletal model was developed with validation against experimental non-premixed counterfiow flame extinction conditions and low pressure flame structure data for both propane and methane flames, as well as indirection comparison to experimental methane-air burning velocity results. The degree of drop evaporation and resulting levels of water vapor in the incoming air stream were estimated for the experimental conditions. Comparison of the computational extinction strain rates with the reported experimental measurements shows good agreement in consideration of the degree of mist evaporation in the experimental air stream entering the flame. The current results explain the observed drop dependent suppression behavior in these flames., Prepared in collaboration with Univ. of VA., Charlottesville, VA.

Water mist is one of the best nongaseous fire suppression replacement agents for Halon 1301 on a mass basis. In general, small drops are more effective than larger drops, but the highly complex nature of fires defies a simple generalization. Drop size is important but so are drop transport and evaporation behavior. Understanding each of these is critical to the design of water mist fire suppression systems. Water spray systems like sprinklers in many buildings produce very large drops, generally above a millimeter in diameter. These systems ineffectively deliver much more water than is usually needed. Water mist systems that use low-pressure nozzles typically produce drops between 200 microns and 1 mm. The production of fine water mist (drops below 200 microns) requires high-pressure nozzles. NRL studies in laboratory flames show that drops smaller than 40 microns are more effective than Halon 1301 on a mass basis at extinguishing methane/air and propane/air non-premixed flames. Experimental and computer fire modeling studies indicate that effectiveness continues to increase with decreasing drop size. The case looks especially attractive for very fine water mist with drop diameters less than 10 microns., Published in the NRL Review 2005, p124-126. Prepared in collaboration with Geo-Centers Inc.

ELECTRONIC FILE CHARACTERISTICS: 1 file; MS Word (.DOC). PHYSICAL DESCRIPTION: 1 computer laser optical disc (CD-ROM); 4 3/4 in.; 3.39 MB and 1 hardcopy report. SYSTEMS DETAIL NOTE: ABSTRACT: Water mist systems can be used to thermally manage conditions in the primary damage area (PDA) and effectively provide boundary cooling. Overall, the high pressure systems were more effective than the low pressure systems in totally extinguishing fires, which provides the greatest degree of thermal management. For equivalent flow rates, high pressure systems performed better than low pressure systems in terms of extinguishment and thermal management. For the test where the same nozzle design was used, greater flow rate generally resulted in improved thermal management. Nozzle design (pattern, flow, projection) has an impact on thermal management characteristics (flow rate alone is not a reliable indicator of performance). In general, the use of the obstruction did not seem to greatly impact the ability of the water mist system to thermally manage the PDA and prevent flashover. This test series only evaluated Class B fuels., CD-ROM contains appendices A-C. Hardcopy report accompanies CD-ROM. Prepared in cooperation with Hughes Associates, Inc. Baltimore, MD.

While the Halon 1301 fire suppression systems installed in machinery spaces are very effective, environmental regulations have essentially prohibited the use of these systems for future ships. A high-pressure water mist system was developed as an environmentally friendly alternative for conventional Halon 1301 systems. Outlined in NSTM Chapter 555, Section 10 are procedures for dealing with an out-of-control class B fire in a machinery space protected with Halon 1301. Some of these procedures are unnecessary when water mist is used, since water mist can discharge for an extended period of time and offer continuous protection, the need to wait 15 minutes before entering the space is eliminated, and the affected space ventilation can be used during attack team entry. Also, due to the high thermal capacity of water, the potential exposure to hazardous post- fire conditions and the likelihood of fire spread are significantly reduced.

A water mist system that incorporates a survivable design has the potential to significantly reduce the thermal conditions in the primary damage area (PDA) following a weapon hit. This reduction in thermal conditions would certainly prevent flash over and could potentially prevent fire spread to adjacent compartments. The analysis put forth in this paper demonstrates that the likelihood of the PDA to reach flash over following a weapon hit is a function of the size of the opening to the weather created by the blast. Up to the point where the fire becomes fuel surface limited, the larger the vent opening, the greater the fire size and the higher the resulting compartment temperatures. The increased air flow provided by the larger vent opening also dictates the amount of water vapor required to saturate the gases in the PDA. As a result, the amount of mist required to achieve thermal management is also a function of the size of the vent opening. The results of this analysis demonstrate that the conditions produced by the fire following a typical weapon hit could be mitigated by appropriately discharging a minimal amount of water mist into the PDA.

This is the preliminary test report analyzing the DD(X) CONOPS for DC manning and PDA(F) cooling. These tests were conducted in May 2003 on the ex-USS Shadwell. A variety of peacetime and combat damage fire scenarios were evaluated as part of this test series. This report contains a brief summary of the events for each test. The following summarizes the preliminary conclusions for these tests. A properly trained damage control team, familiar with the layout of the DD(X) is essential for optimum DC response. The need for modes of operation for the DD(X), PDA(F), and APDA(F) water mist systems should be analyzed. PDA cooling using sidewall water mist nozzles has been shown to he effective in reducing temperatures and suppressing the fire. Investigators are an essential part of the DC organizations. Communications have been and still are a problem., Prepared in collaboration with Hughes Associates, Inc. Baltimore, MD.

This report describes the results of the first year of an experimental program aimed at developing a prototype water mist fire suppression (WMFS) system for integration with DC-ARM (Damage Control-Automation for Reduced Manning) objectives on Navy shipboard applications. The WMFS system is to provide, as a minimum, flashover suppression and boundary cooling, so that a fire may be controlled and confined to the compartment of origin for an extended period. Damage control crews responding to the fire will encounter small fires, which can be extinguished using a minimum of manpower. In this way the number of persons required for Damage Control response will be reduced from current levels. The WMFS system is to be designed to be reflexive, so that battle damage to piping will be self-isolated to the area of direct damage, leaving the surrounding parts of the distribution system in operable condition., Prepared in collaboration with Hughes Associates, Inc., Baltimore, MD. ADA369112

This report describes the results of the first year of an experimental program aimed at developing a prototype water mist fire suppression (WMFS) system for integration with DC-ARM (Damage Control-Automation for Reduced Manning) objectives on Navy shipboard applications. The WMFS system is to provide, as a minimum, flashover suppression and boundary cooling, so that a fire may be controlled and confined to the compartment of origin for an extended period. Damage control crews responding to the fire will encounter small fires, which can be extinguished using a minimum of manpower. In this way the number of persons required for Damage Control response will be reduced from current levels. The WMFS system is to be designed to be reflexive, so that battle damage to piping will be self-isolated to the area of direct damage, leaving the surrounding parts of the distribution system in operable condition., Prepared in collaboration with Hughes Associates, Inc., Baltimore, MD. ADA369113

This report is the fourth in a series dealing with numerical modeling of fire suppression using water mist. While the first two reports examined the interaction of water mist with two-dimensional methane air diffusion flames, the third report presented a numerical model for studying methanol liquid pool fires, As shown in that report, numerical results exhibited a flame structure that compared well with experimental observations and thermocouple temperature measurements. In the present report we describe results for water-mist suppression of liquid methanol pool fires. The interaction of water-mist with pulsating pool fires is studied. Time dependent heat release rate profiles and temperature profiles identify the location where the water droplets evaporate and absorb energy. Numerical results are also presented for the effect of water mist on steady methanol pool fires stabilized by a strong co-flowing air jet. The relative contribution of the various suppression mechanisms such as oxygen dilution, radiation and thermal cooling on overall fire suppression is investigated. Parametric studies are performed to determine the effect of droplet injection density, velocity and droplet diameter on entrainment and overall suppression of pool fires. These results are reported in terms of reduction in peak temperature, effect on burning rate and changes in overall heat release rate. Numerical simulations indicate that small droplet diameters exhibit smaller characteristic time for decrease of relative velocity with respect to the gas phase, and therefore entrain most rapidly into the diffusion flame. Hence for the co-flow injection case, smaller diameter droplets produce maximum flame suppression for a fixed amount of injection spray density., Prepared in collaboration with Science Applications International Corp., Arlington, VA. See also AD-A337 904, AD-A349 379 and AD-A355 969.

This report is the first in a series dealing with the numerical modeling of fire suppression using water mist. The focus of this report is on the suppression of gas jet diffusion flames using fine water droplets. A two continuum formulation is used in which the gas phase and the water mist are both described by equations of the eulerian form. The model is used to obtain a detail understanding of the physical processes involved during the interaction of water mist and flames. The relative contribution of various mist suppression mechanisms is studied. The effect of droplet diameter, spray injection density and velocity on water mist entrainment into the flames and flame suppression is quantified. Droplet trajectories are used to identify the regions of the flame where the droplets evaporate and absorb energy. Finally, the model is used to determine the water required for extinction, and this is reported in terms of the ratio of the water supply rate to the fuel flow rate.

A tool suitable for conducting industrial fire and explosion hazard analysis is presented, together with an identification of weak links in the hazard evaluation chain. For some of the weak links additional research has been carried out. The tool, "FREIA", evaluates the consequences for humans and components due to fires and accidental releases indoors and outdoors using established engineering methods. Investigations have been carried out to find possible methods to simulate detector activation. The temperature, velocity, soot, CO2, CO and oxygen concentration were determined in the plume above a fire. Close agreement was found between the different compound fields. A CFD simulation of the same plume closely matched the experiments. However, there are large uncertainties involved when transforming light attenuation measurements into soot volume fraction. Simulations of tests according to the EN54 detector standard were also carried out. The agreement differed for different fuels. In addition, there is a problem with comparing light attenuation measurement performed at different wavelengths. All the results obtained indicate that it is possible to model smoke detector activation by treating the soot as an inert gas, or by assuming the soot concentration closely corresponds to one of the other compound fields. Heat detector activation is not as complicated to simulate. The phasing out of halons often demands new solutions in order to maintain the given protection level. More recently water mist has been mentioned as a possible replacement for halons. Experiments together with theoretical considerations have shown that no presently available water mist system fulfils the requirements of a total flooding system. A narrow window exists, however, in which a water mist can function as a total flooding system. Several halon-like agents have been developed. These, however, produce more thermal decomposition products than halons, the amount produced was found to be proportio

A series of tests was conducted to evaluate the capability of water mist nozzles for extinguishing fires in engine and generator rooms on U.S. Army watercraft. Three types of nozzles were evaluated: single fluid low pressure, single fluid high pressure and dual fluid (air/water) nozzles. The international Maritime Organization's (IMO) test protocol for halon alternatives in machinery spaces and pump-rooms was used. The tests were conducted in a simulated machinery space 9.1 x 9.1 x 4.6 m. The best performance was obtained with a single fluid high pressure nozzle which was able to extinguish all of the fires in the IMO test protocol except the bilge-fire mist nozzles in the bilge areas., Prepared in collaboration with Hughes Associates, Inc., Baltimore, MD.

The present study focuses on extinction of flames with water mist where surface cooling effects are neglected i.e. water mist as a total flooding system where the direct spray cannot reach and cool all burning items in the protected volume. The study includes a survey of the production and properties of water mist such as different types of nozzles and means to describe droplet size distribution. Properties of jets and sprays are discussed as well as water droplet movement, fall and evaporation. Three different series of experiments were conducted with different hydraulic atomising nozzles. In the first series, droplet size distribution and water spray distribution measurements for the nozzles were conducted. The measurements showed that the droplet size distribution ranged from a Sauter Mean Diameter of approximately 35 - 85 µm, all dependent on the water pressure and the configuration of nozzles. The measurements show that considerably larger droplets are formed when individual nozzles are placed together. This can be explained by a coalescence effect when droplets from the sprays of the nozzles collide. The second series of experiments were done using a tubular propane gas bumer where water and propane were mixed prior to reaching the burner outlet. Based on the tests, the specific amount of extinguishing medium required (Required Extinguishing Medium Portion, REMP = m, / m, i.e. the ratio of the agent quantity to fuel quantity consumed) is given as a quantitative measure of the efficiency of the agent. The lower the REMP value, the more efficient the agent. The water pressure ranged between 40 and 80 bar which provided for droplet sizes with a Sauter Mean Diameter in the order of 35 pm. The results show that the amount of water needed for extinguishment by weight is between 1.2 - 2,2 times the amount of propane gas. The decrease in droplet sizes decreased the amount of water needed. Another observation was that the heat release rate of the fire is not affected u

Fires in mine tunnels and other underground space are a serious hazard, that can, if left unchecked, result in significant economic loss and human tragedy. In the UK, methods such as water deluge, foam application, and various types of handheld extinguishers have been used, but statistics show no improvement in the incidence of fire. Water mist has the potential to be an effective fire suppression system for tunnel spaces. Typical water mist systems utilise small droplets of around 100 micron that have a low terminal velocity and a high surface to volume ratio. This leads to behaviour distinct from that of traditional sprinklers. Various mechanisms of action have been identified: removal of heat; oxygen depletion; fuel cooling; attenuation of radiation; and disruption of air flow. The relative importance of each is case dependent. Current research has focussed almost exclusively on enclosures with minimal or no ventilation, and no data relevant to the application of mist in tunnels exists. In this thesis, a series of Computational Fluid Dynamics (CFD) simulations, based on published experimental data, are used to indirectly validate a CFD model of a hypothetical water mist system applied to a real tunnel fire, and to improve the understanding of how water mist performs in a strongly ventilated space. The water mist is represented by a Lagrangian-based particle-tracking model. This model is fully coupled to the continuous phase, accounting for transfer of momentum, heat, and mass. A 16m3 unventilated enclosure is used first to validate a pool fire model based on 0.3m square pools of methanol (27 kW) and hexane (115 kW). The behaviour of a thermal plume in a tunnel with forced ventilation is then validated, initially using a fixed volumetric heat source of 7.5kW in a small-scale tunnel, and then on a full-scale 3m square cross-section tunnel with a 3m diesel pool using the pool fire model. The water mist model is validated with the enclosure fire, and a sensitivity st

Fires in mine tunnels and other underground space are a serious hazard, that can, if left unchecked, result in significant economic loss and human tragedy. In the UK, methods such as water deluge, foam application, and various types of handheld extinguishers have been used, but statistics show no improvement in the incidence of fire. Water mist has the potential to be an effective fire suppression system for tunnel spaces. Typical water mist systems utilise small droplets of around 100 micron that have a low terminal velocity and a high surface to volume ratio. This leads to behaviour distinct from that of traditional sprinklers. Various mechanisms of action have been identified: removal of heat; oxygen depletion; fuel cooling; attenuation of radiation; and disruption of air flow. The relative importance of each is case dependent. Current research has focussed almost exclusively on enclosures with minimal or no ventilation, and no data relevant to the application of mist in tunnels exists. In this thesis, a series of Computational Fluid Dynamics (CFD) simulations, based on published experimental data, are used to indirectly validate a CFD model of a hypothetical water mist system applied to a real tunnel fire, and to improve the understanding of how water mist performs in a strongly ventilated space. The water mist is represented by a Lagrangian-based particle-tracking model. This model is fully coupled to the continuous phase, accounting for transfer of momentum, heat, and mass. A 16m3 unventilated enclosure is used first to validate a pool fire model based on 0.3m square pools of methanol (27 kW) and hexane (115 kW). The behaviour of a thermal plume in a tunnel with forced ventilation is then validated, initially using a fixed volumetric heat source of 7.5kW in a small-scale tunnel, and then on a full-scale 3m square cross-section tunnel with a 3m diesel pool using the pool fire model. The water mist model is validated with the enclosure fire, and a sensitivity st