Application Of Water Mist Research Articles

The efficiency of dodecafluoro-2-methylpentan-3-one in suppressing NCM 811 lithium-ion battery fire

With the increase in the specific energy of lithium-ion batteries (LIBs), fire accidents occur more frequently; however, the effective and clean suppression of LIB fires remains a challenge. In the present work, the efficiency of dodecafluoro-2-methylpentan-3-one (C6F12O) in suppressing high energy density (HED) ternary LIB fires is experimentally investigated. It is found that C6F12O can efficiently extinguish the HED battery and its module fire. As the flow rate increases, the extinguishment time decreases and the peak temperature decreases, but the cooling efficiency for the long-term process is reduced. When the C6F12O spray can completely cover the thermal runaway (TR) area, its extinguishing and cooling effect is the best. For the HED module, the application of C6F12O effectively increases the TR trigger temperature, reduces the TR peak temperature, and decreases heat production. The application of water mist enhances the cooling of extinguished LIBs, the combination of C6F12O and water mist extends the TR propagation time of the fully charged LIB module to 1.4 times that without suppression, and the total TR heat production is reduced by 1423.1 kJ. These results provide guidance for the design of inhibitor volume fractions for HED LIB fires.

Assessment of the Impact of Extinguishing with a Low-Pressure Fog Lance on a Fire Environment

A main purpose of the study was to assess the impact of extinguishing with a low-pressure fog lance on a fire environment, especially of temperature. A low-pressure fog lance has recently been recommended for fighting fires in either limited spaces or difficult to access places. Four tests were conducted in real internal fire conditions. The following lances were used in sequential tests: fognail attack, MK with attack head, fognail defense and MK with defense head. They were fed from a fire vehicle GBA 2.5/24 equipped with a pump with automatic pressure regulation and hose lines W75 and W52. The temperature was measured with thermocouples at various points of the room, including the ceiling. Photographic documentation of the tests was prepared using thermal and video cameras. The best way of using a fog lance was established from literature sources and the manufacturer’s requirements. Two main factors of effective firefighting were observed during the tests: smoke cooling and isolation of the fire by formed water vapor. The use of a fog lance significantly improves of fire-fighting operations. A proper application of water mist eliminates the risk of fire gases’ ignition. The assumed times of ensuring safe conditions in the room were confirmed.

Improvement of aerosol spray scavenging efficiency with water mist

The resolidified fuel debris from the damaged Fukushima Daiichi reactors must be cut into small pieces prior to removing it from reactor buildings. Submicron radioactive aerosol particles are likely to be generated and dispersed into the primary containment vessel (PCV) atmosphere during this cutting process. However, traditional sprays cannot effectively scavenge aerosol particles with diameters in the range of 0.1–1 μm from gas environments. In this paper, a new aerosol agglomeration method is accordingly proposed employing water mist as a pretreatment to enlarge the aerosol particles prior to removing them using water sprays. First, the water mist is injected into a vessel in which aerosol particles are primarily dispersed. Following a short waiting time, subsequent spray injection is then able to more effectively remove the enlarged aerosol particles. The application of water mist was found to improve the aerosol spray scavenging efficiency by coalescing with aerosol particles under both diffusiophoresis and different coagulation mechanisms to form large-sized agglomerated mist–aerosol particles that can subsequently be removed by the water spray. The efficiency of removal is increased due to the enhanced collection mechanisms of inertial impaction and improved particle surface hydrophilicity. The optimized spray system evaluated in this study will be used to effectively control radioactive aerosol suspension inside the Fukushima Daiichi PCVs and protect workers and the public from any unknown consequences of internal radiation exposure during reactor decommissioning. The proposed method can also be applied throughout the nuclear industry to reduce the risk posed by small-sized aerosol particles during maintenance.

Experimental study on the synergistic effect of gas extinguishing agents and water mist on suppressing lithium-ion battery fires

Abstract Currently, effective suppression methods are still required to deal with lithium-ion battery (LIB) fires. In this paper, a novel synergistic fire extinguishing method of gas extinguishing agent (C6F12O, CO2 and HFC-227ea) and water mist is designed to evaluate the effect of their combination. A 243 Ah large-scale LIB with LiFePO4 as cathode is used in this work. Several cell parameters are measured to evaluate the suppression effect of fire extinguishing method, such as extinguishing time, maximum temperature, mass loss and heat release rate. Meanwhile, the cooling effect, fire extinguishing effect and economic benefit of different fire extinguishing methods are all considered. Results show that the suppression effect of synergistic fire extinguishing method is better than that of the single agent. Single application of water mist can hardly extinguish the flame, while the combination of gas extinguishing agents and water mist can extinguish the flame finally. However, the C6F12O extinguishes the flame immediately, while CO2 has a longer extinguishing time, and HFC-227ea cannot extinguish the flame. So in these experiments, the C6F12O combined with water mist exhibits the best extinguishing and cooling effect. The CO2 combined with water mist has good economic benefit, better fire extinguishing effect and cooling effect in these experiments, which can also be considered in suppressing LiFePO4 LIB fires.

The Ceiling Height Limits for Water Mist Protection of Two Solid Combustible Fire Hazards in Open Environment

CEN and NFPA have expanded the application of water mist in open environments from light solid combustible fire hazards to several in the higher hazard categories. A previous analysis and test evaluation showed that such application expansion is feasible, provided that the water mist spray meets droplet size and application density requirements for the intended fire challenge. However, this evaluation was performed exclusively for water mist sprays discharging at 1.65 m above the burning combustibles. This led to the question of whether the water mist protection could still be effective for larger clearances of nozzle discharge above the combustibles. Therefore, a series of fire tests was conducted subsequently to determine the ceiling height limits for both deluge and automatic nozzle protections. As for the previous evaluation, the two tested fire challenges were a 2-tier (2.74 m) high rack-storage of corrugated cardboard cartons on wood pallets, and a palletized storage of cartoned expanded polystyrene up to 1.68 m high. Both fire challenges were in the CEN OH-3 category, and respectively represented fire hazards in the FM Global HC-2 and HC-3 categories, which in turn corresponded to the NFPA OH-1 and OH-2 fire hazards. Each water mist spray discharged 76 l/min at 16.5 bar, with a volume median droplet diameter of around 220 µm. The nozzles were spaced 3.05 × 3.05 m to provide a designated application density of 8.1 mm/min. Quick-response thermal sensors, with an activation temperature of 74°C and a response index of 27.6 (m s)1/2, were employed to initiate the nozzle discharge. The tests showed that the deluge protection is applicable to both fire challenges for ceiling heights up to 9.1 m. However, for the automatic nozzle protection, the ceiling height limit is reduced to 6.1 m, with a water supply requirement of providing 17 nozzle operations for a safety factor of about 50% over the maximum number of nozzle operations observed in the tests.

Laboratory Investigation to Assess Spontaneous Combustion/Fire During Extraction of Thick Coal Seam

Spontaneous combustion/fire and explosions occurring in the goaf area due to depillaring of thick coal seam (5–8 m) experiences significant loss to the mining industry. This ultimately causes destruction of natural resources and fatal accidents in India. Thus, it is threatening the safety of underground coal mines. This paper includes various laboratory studies to determine the cause of spontaneous combustion/fire during depillaring of panels in thick coal seams. The laboratory investigation comprises of proximate analysis, critical oxidation temperature study, differential scanning calorimetric analysis, fire ladder study, and goaf ignition temperature. The field investigation comprises of hygrometric survey to determine moisture loss and ventilation survey of the working seam to reveal that the goaf of the working panel is highly prone to spontaneous combustion/fire. The results of the above studies will help to develop suitable technique, i.e., partial stowing in goaf areas with the application of water mist spraying to prevent spontaneous combustion/fire during depillaring of thick coal seam. The above studies were carried out during depillaring panels (B2A and B2B) of a thick seam (5.4 m) at Khottadih Colliery, M/s Eastern Coalfields Limited of Raniganj coalfield of India.

Fire Protection of Steel Structures by Low Pressure Water Mist in Large-Scale Fire Test

Water mist extinguishing systems are becoming more popular due to their much higher fire-fighting efficiency at lower water consumption compared to conventional sprinklers. The article focuses on the possibility of further utilization in a form of cooling structures and presents the results of a research in the area of low-pressure water mist and the development of a new low-pressure water mist cooling system. It also introduces a new possible direction for application of cooling steel structures or their surroundings in order to increase fire resistance of steel structures. To verify the cooling effects of low-pressure water mist, a large-scale fire test with a model of steel roof construction was carried out in a room with dimensions of 4.0 × 4.0 × 2.0 m. The fire test was conducted in two scenarios. The first scenario is a reference test without application of water mist, where temperatures of the burning room and steel structures are monitored. Compared to the first scenario, the second scenario includes the use of low-pressure water mist protection of the steel structure model at the time of full fire development.

Adhesion of dry and wet electrostatic capture silk of uloborid spider.

We demonstrate the impressive adhesive qualities of uloborid spider orb-web capture when dry, which are lost when the nano-filament threads are wetted. A force sensor with a 50 nN-1 mN detection sensitively allowed us to measure quantitatively the stress-strain characteristics of native silk threads in both the original dry state and after wetting by controlled application of water mist with droplet sizes ranging between 3 and 5 μm and densities ranging between 10(4) and 10(5) per mm(3). Stress forces of between 1 and 5 μN/μm(2) in the native, dry multifilament thread puffs were reduced to between 0.1 and 0.5 μN/μm(2) in the wetted collapsed state, with strain displacements reducing from between 2 and 5 mm in the dry to 0.10-0.12 mm in the wetted states. We conclude that wetting cribellate threads reduce their van der Waals adhesion with implications on the thread's adhesive strength under tension. This should be considered when discussing the evolutionary transitions of capture silks from the ancestral dry-state nano-filaments of the cribellate spider taxa to the wet-state glue-droplets of the ecribellate taxa.

Numerical Simulation on Turbine Blade Leading-Edge High-Efficiency Film Cooling by the Application of Water Mist

Numerical simulation is performed to explore leading film cooling enhancement by the application of injecting water mist into the air. The accuracy of numerical simulation program for conjugate heat transfer methodology is verified with the C3X gas turbine vanes cooled with leading edge films. The effect of various parameters including mist concentration, mist diameter, different particle wall interactions conditions, and different forces on the improvement of cooling performance is investigated in this paper. It indicates that mist film cooling can decrease the temperature of boundary layer without impact on the temperature of the mainstream and the thickness of boundary layer.

On the Fire Intensification of Pool Fire with Water Mist

Intensification of pool fire will occur under the application of water mist. The phenomenon was discovered in previous studies; however, there has been no unified conclusion for the reason of this phenomenon. Studying mechanisms of the intensification has a very important significance in the engineering application of water mist. According to previous studies, the intensification can be divided into two categories, one is the fire intensification in gas flame; the other is the interaction of water mist with the heated fuel, which lead to the increase of mass loss rate. In this paper, Mechanisms of the second type of fire intensification are studied through theoretical analysis and experiment. Research shows that the primary mechanism of fire intensification by water mist is boil over.

The Experimental Study on Extinguishing Cooking Oil Fires by Water Mist

Abstract. The effects of flow coefficients, working pressures and different spray distances on extinguishing cooking oil fires by water mist were studied by experiment. The results show that the fire suppression effectiveness is increased with the increase of flow coefficient and working pressure, spray distance also affects the fire extinguishment efficiency of water mist. Reasonable conditions and designing parameters for practical engineering application of water mist are suggested.

CONCEPT DESIGN AND TESTING OF MULTI-NOZZLE WATER MIST FIRE SUPPRESSION SYSTEM

In this work a flexible design of multi-nozzle arrangement of water mist fire suppression system was studied. The source of fire was a 65 mm diameter cooking oil fire. An investigation on the impact of nozzle arrangement on the temperature profile of fires was conducted. The occurance of oil splash due to the application of water mist was also studied. The water mist systems developed in the present work can effectively extinguish cooking oil fires and prevented them from re-ignition. The spray angle, discharge pressure, and water flow rate were important factors to determine the effectiveness of water mist in extinguishing cooking oil fires.

Preliminary Experimental Study and Numerical Simulations on Suppressing Spray Bitumen Fire with Water Mist in a Confined Space

Spray bitumen fires often occur in buildings and industrial processes. To investigate this type of hazard, the burning behavior of this flammable mixture was tested under practical conditions. Investigations of the suppression of this typical kind of fire were also included. CFD simulations were used as supplementary validation of tests that assessed the suppression of this type of fire by application of water mist. The water mist was generated from a centrifugal nozzle operating at low pressure about 1.0 MPa. The characteristics of the water mist were tested by LDV/APV system. The fuel was sprayed using the same sprayer as the sub-sprayer of the water mist nozzle. The flame structure was observed by the Thermograph (TG, SATHY6850). The various temperatures were tracked every 1 second by the K-type thermocouple. The flame suppression processes were observed and analyzed using a Charge Coupled Device (CCD) video camera. All the experiments were carried out in a 3 m × 3 m × 3 m confine space. Results indicated that the highest temperature of the spray bitumen fire was recorded in the core of the spray. The spray bitumen fire could be suppressed effectively by using the water mist fire suppression system. For lower pressure of the spray bitumen, the water mist suppression demonstrated higher efficiency. The test results showed that there was a short-lived “fire enhancement” phenomena as long as the water mist was released into the spray fire. Also, using the FDS to simulate the spray bitumen fire, we found comparative results between the numerical and experimental results.

Fire Protection of Heritage Structures: Use of a Portable Water Mist System under High-altitude Conditions

In order to verify the application of water mist on fire protection of the Potala Palace in Tibet and deepen the knowledge of its suppression mechanisms under high-altitude conditions, a series of experiments are performed with a portable water mist fire protection system and with diesel oil, gasoline and, in Lhasa, ghee as fuels. All of the experimental tests are conducted with and without multicomposition (MC) additives. The experimental results show that the MC additive can evidently improve the extinguishing efficiency of water mist for a diesel fire, but the gasoline fire is a little difficult to extinguish. The effects of high-altitude conditions on fire suppression are discussed.

Effects of water mist on open fire – a model study

Outbreak of open fire in coal mines is one of the major causes of disaster involving loss of life, hindrance in coal production and loss of machinery involved in coal winning operations. Until recently, no substantive work has been carried out in India to prevent such untoward incidents. To understand the complex phenomenon of open fires and its preventive techniques, a mine fire model gallery has been designed and constructed at the Central Mining Research Institute, Dhanbad, India. The gallery is equipped with state-of-the-art instrumentation systems to monitor the important fire parameters. Three fire suppression techniques –liquid nitrogen, high-pressure high-stability (HPHS) nitrogen foam, and water mist – were tried in three sets of experiments. This paper addresses the important design features of the gallery, experimental details, and the effects of the application of water mist on open fires. An international literature review regarding the application of water mist technology is also outlined. Experiments showed that water mist has the potential to reduce the intensity of fire, lower the products of combustion (POC) and reduce suspended particulate matter (SPM). Water mist technology is able to control open fires in underground coal mines.

Application Of Water Mist To Extinguish Large Oil Pool Fires For Industrial Oil Cooker Protection

Large oil fires occurring in industrial oil cookers are very challenging to extinguish due to their size and the large amount of hot oil involved. This paper reports a study to use water mist for large industrial oil cooker protection. The extinguishing mechanisms of water mist and corresponding criteria required for extinguishing large pool cooking oil fires were investigated both theoretically and experimentally. Based on the extinguishing mechanisms and required criteria, two water mist systems were developed in the present work. A series of full-scale fire tests were conducted in a large industrial oil cooker mock-up. The study showed that the two water mist systems presently developed worked effectively to extinguish large cooking oil fires and prevented them from re-igniting. Their extinguishing performance was determined by the type of water mist system, discharge pressure and hood position in the oil cooker.

EXPERIMENTAL STUDY ON EXTINGUISHING POOL FIRE SHELTERED BY BARRIER WITH WATER MIST

In order to systematically study the interaction of water mist with flame sheltered by barrier, a series of experiments were conducted in a 8m X 10m X 5m full scale confined space with high pressure water mist system. Before and after the application of water mist, some K-type thermocouples along the liquid pool fire up-surface centerline were used to measure flame temperature and a CCD camera was used to record the extinguishment events onto VHS tapes for subsequent frame-by-frame analysis, respectively. The experimental results show that when the liquid pool fire is thoroughly sheltered by barrier, common water mist cannot extinguish the fire, but it can effectively control and suppress the fire spread and reduce the fire temperature obviously; when the liquid pool fire is sheltered partly, more water mist can reach the fire area by increasing the water mist pressure, reducing the horizontal distance and the height between the nozzle and pool fire, so the fire extinguishing time can be decreased. Language: en

Progress in research and application of water mist fire sup-pression technology

Progress in research and application of water mist fire sup-pression technology

Experimental Study on the Effectiveness of the Extinction of a Pool Fire with Water Mist

In order to study the effectiveness of the extinction of a pool fire with one nozzle water mist, a series of experiments were conducted under different conditions in an open space. Fire sources are small-scale circular stainless steel pans of 130 and 200 mm in diameter with the fuel of alcohol and kerosene. Before and after the application of water mist, some K-type thermocouples along the pool centerline and a digital camera were used to measure the flame temperature and visualize the process of the fire extinction. A thermogage and a turbine flux sensor were used to measure the flame radiant heat flux and the application rate of water, respectively. A Particle Image Velocimetry and Sizing (PIVS) technique was developed to characterize the water mist. The experimental results show that both the flame of alcohol and kerosene cannot be extinguished in many cases when the pressure is lower than 0.4 MPa. In addition, the distance between the flame and the nozzle, and the application rate of water are two main factors which influence the effectiveness of the extinction of a pool fire when the working pressure is lower and the impulse injection of water mist can improve the effectiveness of fire extinction. However, it should be noted that the results are limited to the experimental conditions because it is still difficult to get the functional relationships of pool fire extinction mechanisms with water mist.

Preliminary Study on the Interaction of Water Mist with Pool Fires

In this paper, some preliminary measurements and observations were conducted to investigate the interaction of water mist with pool fires. The fire source is a small-scale circular stainless steel pan with heptane, ethanol and kerosene as fuel. Water mist was generated by a downward-directed pressure nozzle that was positioned on a square steel plate 300 mm over the fuel sample and was operated at pressures of 0.5 MPa. The water mist characteristics were determined by a LDV/APV system. The radiation spectra of the flames were measured by a monochromator and the radiant heat flux was obtained by a thermogage before and after application of water mist. Thermography was used to visualize the thermal field of the flame. The experimental results show that the interaction mechanisms of kerosene flame are different from those of ethanol and heptane.