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Lithium-ion batteries experience rapid temperature increases with a high risk of combustion and explosion during thermal runaway, and water mist has been considered as one of the most effective cooling strategies. The water mist field can be impacted by the safety valve airflow, subsequently affecting the cooling characteristics. In this paper, the water mist nozzle with a fixed working pressure is located 1 m above the 100 Ah LiFePO4 battery to suppress the thermal runaway, and the cooling characteristics under various stages have been compared and analyzed. The results show that the development of thermal runaway can be inhibited before thermal runaway is initiated, and the water mist presents a better cooling effect after the battery safety valve is opened. The critical accumulation heat density of 155 kJ/kg has been identified, which is the threshold for thermal runaway suppression. The confrontation between water mist and the flame has been analyzed, and the water mist droplets cannot fall on the battery surface, resulting in a poor cooling rate of 0.57 kW. This means the suppression effect of water mist will be affected by the airflow impact of the safety valve. [ABSTRACT FROM AUTHOR]

Drives in belt conveyors are critical components of the conveyor system, susceptible to various factors that can cause disruptions and energy losses. In underground mining conditions, the risk of drive fires is particularly hazardous. Therefore, it is necessary to develop highly effective fire suppression systems. However, there are no guidelines for designing such systems. This study presents a methodology for selecting and verifying the fire suppression systems for belt conveyor drives. The proposed AMIGA system for extinguishing fires on underground coal mine conveyor belts, incorporating spraying and water mist installations, is supported by a theoretical calculation methodology. This enables determining the number of required nozzles and flow rate for complete fire suppression. The development of a methodology for the selection and verification of the sprinkler system components utilized guidelines provided in the standard VdS 2109:2002-03 and the PN-EN 12845+A2 standard from 2010, while a novel approach is proposed for water mist parameters that has not been previously applied anywhere else, and is based on assessing the fire's intensity and the persistent disruption of the energy balance of the combusted coal. The theoretical calculations for potential fire power facilitate the determination of the appropriate water flow rate for the spraying system to protect the upper belt drive. For the proposed AMIGA system, the potential fire power was calculated to be 10.33 MJ / min . Based on this, the water flow rate for the spraying installation to protect the upper drive belt of the conveyor was established to be a minimum 37.5 dm 3 / min , and 21.4 dm 3 / min for the mist installation used to protect the space below the conveyor drive. In order to verify the developed methodology for parameter selection, on-site tests were conducted to verify the results. Tests were conducted on an AMIGA prototype suppression system integrated into a conveyor drive. The results demonstrate that the developed system is effective in extinguishing fires on the belt using the spraying installation, as well as under the conveyor belt drive using the water mist installation, within the entire supply pressure range ( 0.4 MPa to 1.6 MPa ). [ABSTRACT FROM AUTHOR]

Determining the input parameters for the calibration of a water mist extinguishing system in a compartment is important for the evaluation of the performance of the design. Although there is a lot of research on the use of water mist, it is still difficult understand the behavior of the system in terms of safety of people and protection of things. In this study, we aimed to conduct an experimental analysis to evaluate the effectiveness of water mist extinguishing systems in protecting paintings in art gallery museums. We compared onsite tests in a compartment of an art gallery and a numerical analysis carried out with Fire Dynamics Simulator (FDS). Numerical analysis using FDS included the water-cooling effect and the heat power in the simulated environment and the calibration for a model was found by reproducing the onsite results. The temperature trend was monitored as an essential parameter for the protection of the paintings. The study aimed to not only verify the effectiveness of the water mist system but also investigate the reproducibility of real-scale conditions through a simulated environment. The most important result obtained is the possibility of using a simulated environment instead of real-scale tests in order to test water mist capabilities. [ABSTRACT FROM AUTHOR]

Interest in water mist fire suppression has increased within the fire protection industry due to its ability to control the spread and development of fire without using environmentally damaging agents. Water mist fire suppression has been used for many years in various applications such as machinery spaces, combustion turbine enclosures, and onboard passenger sea vessels. Now there is a demand to use this firefighting method to protect other fire risks such as cooking areas, commercial buildings, residential buildings, electrical equipment, road tunnels, bushfire (wildland fire) protection, and nuclear power generation facilities. To support this industry demand, this review covers the fundamentals of water mist, its suppression mechanisms, areas of application, existing research and development, and the codes and standards related to design. This comprehensive review provides a clear history of water mist suppression. It is able to identify the issues and challenges related to the technology to help pave the way for future research and development that will improve these systems to a level so that they are suitable for these new applications and meet the industry demand for nontoxic fire suppression systems. [ABSTRACT FROM AUTHOR]

In this paper, to reflect a real fire combustion situation of stilted buildings with a typical wooden structure, we used FDS numerical simulation software to study the suppression effect of a fine-water-mist fire-extinguishing system under different working conditions. The influences of different mist droplet diameters, spray flows, and nozzle densities on the temperature change in the combustion area were analyzed and compared. The particle sizes of fog droplets exhibited a significant impact, indicating that the smaller the particle size, the faster the vaporization rate and the better the cooling effect. The cooling effect was better when the particle size was 150 μm or less when compared to the particle sizes of 200 and 300 μm. As the spray flow rate and nozzle density were increased, the fire field temperature decreased, and the cooling effect was enhanced, optimal at a water-mist flow rate of 8 L/min. Therefore, given the possible working conditions, the spray flow rate and the nozzle density should be high, while a suitable droplet size should be selected to achieve the best fire-extinguishing effect. [ABSTRACT FROM AUTHOR]

Fire safety is a changing science for which the dominant parameters that affect fire suppression are still not well defined. The aim of this work is to show that sensitivity analysis techniques can speed up and improve the design process of fire suppression experiments by water mists. The important parameters that play a role in the performance of water mists were confirmed using the CFD code FDS. Various sensitivity analysis methods based on the factorial design and variance decomposition are used with four input parameters (flow rate, spray cone angle, discharge duration and droplet diameter). In our case, results highlight the importance of the discharge duration for the performance of water mists in a confined environment and a strong non-linear effect of the spray cone angle on temperature when variance decomposition methods are used. Further works will be conducted in order to confirm that sensitivity analysis can be used for application in fire suppression by water mist. [ABSTRACT FROM AUTHOR]

In this article, a collective database from validated numerical simulation has been established to study the suppression effects of water-based suppression systems under a single-compartment fire scenario at various suppression configurations and fire locations. Five fuel locations along the axis between the centre and corner of the room were configurated to dynamically analyse how the horizontal distance between the nozzle and fuel pan affects the heat release rate (HRR), temperature cooling phenomena at different heights and also the velocity profile. Throughout the fuel pan relocations, the water-mist system has achieved an average suppression time of 25 s for all the locations, it was found that the water mist system can effectively control the fire under 200 °C that is distanced over 2 m spanwise displacement from the nozzle against the fire, while the sprinkler has exhibited an excellent fuel surface cooling effect due to large momentum and heat capacity within the coverage area with an average suppression time of 50 s. The results of this study have further explored the spray coverage and droplet penetrability of different suppression systems at different locations corresponding to the fire source, and the quantitative assessment of fuel locations could also contribute to the future development of performance-based fire safety designs. [ABSTRACT FROM AUTHOR]

It is commonly assumed in fire modelling that suppression systems can control the heat release rate of a fire. However, many performance-based assumptions are derived from experimental data for sprinklers, and uncertainty remains for their application to water mist systems. In the UK, residential water mist systems are usually tested to the BS 8458:2015 standard, but the heat release rate in these tests is not quantified and focus is instead placed on thermocouple temperatures. This paper details a series of fire tests to the BS 8458:2015 standard for an electronically controlled water mist system. The paper also includes B-RISK zone modelling of these tests to estimate the suppression performance of the system, comparing model outputs to thermocouple test data. Three traditional suppression assumptions, historically derived from experimental data for sprinklers, have been adopted in the zone modelling to examine whether their application following system activation can be extended to the tested water mist system. The work indicates that applying these suppression assumptions remains reasonable in the context of the performance of the tested water mist system, noting the constraints of the test methods in representing a limited number of fire scenarios. [ABSTRACT FROM AUTHOR]

The aim of this paper was to study the suppression influence of water mist on oil pool fires, taking diesel fires and n-heptane fires as experimental objects. The effects of spray pressure and temperature on water mist suppression were examined, and an experimental platform for the suppression of water mist in a small space was set up. Their fire prevention performance and fire extinguishing mechanisms were analyzed by comparing the flame temperature and extinguishing time of diesel and n-heptane pool fire. Three types of spray pressure were set. Water mist was designed at different temperatures and design experiments were carried out for this purpose. The change process of smoke concentration, thermocouple temperature, and flame combustion under different working conditions were analyzed, and the factors affecting the fire extinguishing effect of water mist on oil pool fire were discussed. The results show that 20 °C water mist is more effective at medium and high pressure than at low pressure. Moreover, 80 °C water mist at 9 MPa is more effective in extinguishing n-heptane fire. The flame extinction time is about 10 s, which is more than 40 s higher than that of cold water. [ABSTRACT FROM AUTHOR]

The self-built fine water mist fire extinguishing platform studied the fire extinguishing effect of ultra-fine water mist in cold storage fires. The combustible material selected for our experiments is the cold storage insulation material—polystyrene insulation foam board. The combustion characteristics of the insulation board were studied by pyrolysis analysis. We analyzed the temperature, smoke, and other characteristics of the fire scene when a fire occurs in the cold storage and then manipulated the water mist to carry out the fire extinguishing experiment. Experiments aim to change the particle size and pressure of water mist and study the fire extinguishing efficiency of water mist under different conditions. A thorough analysis was used to determine the particle size range of fine water mist most suited for extinguishing fires in cold storage to offer a theoretical foundation for fire protection design. [ABSTRACT FROM AUTHOR]

Featured Application: Development of water mist fire suppression systems with improved performance. In this study, the effects of discharge area and atomizing gas type in a twin-fluid atomizer on heptane pool fire-extinguishing performance were investigated under the heat release rate conditions of 1.17 and 5.23 kW in an enclosed chamber. Large and small full cone twin-fluid atomizers were prepared. Nitrogen and air were used as atomizing gases. With respect to the droplet size of water mist, as the water and air flow rates decreased and increased, respectively, the Sauter mean diameter (SMD) of the water mist decreased. The SMD of large and small atomizers were in the range of approximately 12–60 and 12–49 μm, respectively. With respect to the discharge area effect, the small atomizer exhibited a shorter extinguishing time, lower peak surface temperature, and higher minimum oxygen concentration than the large atomizer. Furthermore, it was observed that the effect of the discharge area on fire-extinguishing performance is dominant under certain flow rate conditions. With respect to the atomizing gas type effect, nitrogen and air appeared to exhibit nearly similar extinguishing times, peak surface temperatures, and minimum oxygen concentrations under most flow rate conditions. Based on the present and previous studies, it was revealed that the effect of atomizing gas type on fire-extinguishing performance is dependent on the relative positions of the discharged flow and fire source. [ABSTRACT FROM AUTHOR]

To safely mine coal, engineers must prevent gas combustion and explosions, as well as seek feasible and reasonable techniques to control for these types of incidents. This paper analyzes the causes and characteristics of methane combustion and explosions. Water mist is proposed to prevent and control methane combustion in an underground confined space. We constructed an experiment platform to investigate the suppression of methane combustion using water mist for different conditions. The experimental results showed that water mist is highly effective for methane flame inhibition. The flame was extinguished with water mist endothermic cooling. However, the annular regions of water vapor around the fire played a vital role in flame extinction. Water from the evaporating mist replaces the oxygen available to the fuel. Additionally, the time required for fuel ignition is prolonged. For these reasons, the water particle action to flame surface is reinforced and the fuel's reaction with air is delayed. As a result, flame stretching and disturbances occur, which serve to extinguish the flame. Engineering application tests were carried out in the goaf, drill hole and upper-corner to investigate the prevention and control of methane gas combustion, with the results showing a good application effect. [ABSTRACT FROM AUTHOR]

Water mist nozzles are becoming increasingly popular as water extinguishing devices in buildings, increasing people's safety during evacuation. There are questions as to whether or not they are as effective as conventional sprinkler systems. The measurement of the size distribution of the created droplets is one of the components for determining the extinguishing effectiveness of water mist nozzles. The project's goal was to look into the characteristics of the atomized stream produced by a swirl water mist nozzle. The general properties of the tested nozzle are covered in the article. The measurement technique and test stand were given. The collected data was compared to data from the literature. The results are displayed as graphs that depict the distribution of mean droplets with a quantitative volume that varies with pressure and proximity to the test nozzle. The results proved the extinguishing and cooling capabilities of hot fire gases in the water stream created by the tested nozzle.

Lithium-ion batteries (LiBs) are a proven technology for energy storage systems, mobile electronics, power tools, aerospace, automotive and maritime applications. LiBs have attracted interest from academia and industry due to their high power and energy densities compared to other battery technologies. Despite the extensive usage of LiBs, there is a substantial fire risk associated with their use which is a concern, especially when utilised in electric vehicles, aeroplanes, and submarines. This review presents LiB hazards, techniques for mitigating risks, the suppression of LiB fires and identification of shortcomings for future improvement. Water is identified as an efficient cooling and suppressing agent and water mist is considered the most promising technique to extinguish LiB fires. In the initial stages, the present review covers some relevant information regarding the material constitution and configuration of the cell assemblies, and phenomenological evolution of the thermal runaway reactions, which in turn can potentially lead to flaming combustion of cells and battery assemblies. This is followed by short descriptions of various active fire control agents to suppress fires involving LiBs in general, and water as a superior extinguishing medium in particular. In the latter parts of the review, the phenomena associated with water mist suppression of LiB fires are comprehensively reviewed. [ABSTRACT FROM AUTHOR]

The main purpose of this study was to analyze the impact of some parameters (water mist flow rate and type of gas used) of the hybrid extinguishing system on the fire environment (temperature as well as carbon monoxide and oxygen concentrations) in a closed room. Hybrid fire-extinguishing systems in which water mist is driven by inert gas combine the advantages of typical fog systems and fixed gas extinguishing devices. They have been developed in the last years but are now being used more and more often and the preparation of standards for them is planned for 2020. For this purpose, many fire tests with this system should be conducted. Some of them are discussed in this paper. Two different flow rates of water mist (1.5 or 3 dm3/min) and inert gas (nitrogen or air) were used during hybrid system testing. Some parameters of the fire environment in the compartment such as temperature measured by thermocouples as well as carbon monoxide and oxygen concentrations measured by electrochemical gas sensors are presented here. The characteristic values of the extinguishing process are also included. The assumed times of ensuring safe conditions in the room have been confirmed. [ABSTRACT FROM AUTHOR]