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Full-scale experimental studies on extinguishing cooking oil fires with water mist
Abstract
A full-scale heat release rate platform for multifunctional measurement is used to study the interaction of water mist with cooking oil fires in an open space. The heat release rate of cooking oil fires, the temperature history of flame, and the characteristic of smoke are measured and investigated in the experiment. The effect of preignition time on fire extinguishment efficiency of water mist is analyzed, and the principles of effect of water mist on cooking oil fires development are also studied. The experimental results show that cooking oil fires is restrained and extinguished by water mist effectively, the temperature and heat release rate decrease quickly with application of water mist, the concentration of carbon monoxide and carbon dioxide is decreased by water mist, and the concentration of oxygen and the visibility of smoke is increased. At the same time the heat release rate of cooking oil fires is also calculated by heat release rate model of steady fire, which shows that this model can forecast the heat release rate of the developing K-class fires.
... During boiling of water, the CO concentration was at lowest point because water particles can absorb emitted CO. Lee [32] found that the most amount of pollutants are generated during barbecuing. Jiang [33] stated that water mists can diminish both CO and CO 2 concentrations during cooking. ...
Burning fossil fuels has a significant effect on indoor air quality. In this study, the concentration of SO 2 , NO x , NO 2 , NO, CO was measured in five houses at Isfahan focusing attention on kitchens as a source of indoor pollutants. Selected houses differed in terms of kitchen type and finish, presence or absence of a range hood, and type of stove heating. Samplings were done over three days at a fixed time window for each location. Results showed that in closed kitchens without a range hood, the 1-h concentration of pollutants was higher compared to kitchens having open and semi-open range hoods. Minimum pollutant levels were seen for kitchens using an electric stove with a range hood.
... In addition, we did not use a lid in this study; therefore, much water mist was generated during boiling. In full-scale experimental studies, Fang et al. (2006) used water mist to quench cooking oil fires and found that this mist could reduce both CO and CO 2 concentrations. However, further study with fully controlled variables in test kitchens such as a chamber should be conducted to confirm whether CO is absorbed or dissipated from the room because of ventilation. ...
Pollutant emissions from indoor cooking activities using clean fuels such as natural gas or LPG are strongly influenced by cooking ingredients and cooking methods. In this study, we explore the characterization of indoor fine particles (PM 2.5) and CO that are produced by two distinctive cooking methods: frying and boiling. This characterization includes quantifying the presence of fine particles in a kitchen as well as in the adjoining room, analyzing size-segregated carbonaceous materials (EC and OC), and identifying variations in CO associated with the cooking method. Four monitoring devices—a UCB particle monitor, an optical particle counter, a cascade impactor, and a CO monitor—were simultaneously used to measure temporal variations in mass concentrations of fine particles (PM 2.5), particle number concentrations, their size distributions, and CO concentrations in the two rooms, respectively. EC and OC analyses of the particles collected on a quartz filter by cascade impactor were conducted using the thermal optical method. Frying produced higher emissions of fine particles with a wider range of aerodynamic sizes than boiling. Particle spatial distribution was uniform across the rooms during boiling, because emissions were dominated by very fine particle size. It was observed that particle mass size distributions with cut size ≤ 0.25 µm were predominant in all cooking methods. CO concentration was lowest in tofu boiling and about one-tenth of the stove background level. This is possibly due to the absorption of CO by steam cooking.
Using the self-developed compressed air foam fire suppression system, the principles of extinguishing efficiency on pool fire under such factors as foam concentration, nozzle height, forepart structure of mixing chamber and working pressure are studied. It is found that foam concentration has a great impact on extinguishing speed, and that there exists an optimal range of foam concentration for extinguishment. It is also found that coaxial mixing chamber outperforms T-shape mixing chamber in extinguishing efficiency, that there appears to be a second order relationship between extinguishing time and nozzle height, and that increasing working pressure will boost foam covering speed over the pool and then reduce extinguishing time.
The validity of water mist extinguishing quenching oil pool fire was studied using two kinds of nozzles by bench-scale experiments. It was found that in both processes of water mist fire suppression the phenomenon of fire expansion may be found initially. The one with larger droplet size and faster velocity leaded to a much more intensively but evidently shorter combustion intensifying, and showed a higher extinguishing efficiency. Experiments and theoretic study showed that the one with smaller and slower mists intensified combustion mainly by air entraining and extinguished fire mainly by flame and oil surface cooling, while the one with larger and faster mists intensified combustion mainly by azeotropism with oil and extinguished fire mainly by oil surface cooling.
Based on software of Fire Dynamic Simulator, the optimum parameters of water mist were analyzed to suppress the K-class fire. Under different flux velocity and flow rate of water mist by FDS, flame temperature, concentration of hazardous gas and oxygen, as well as heat release rate were recorded to analyze the spreading trend of cooking oil fire and the fire suppression mechanism. The simulation results show that kitchen fire can be effectively extinguished and the harmful gases are under control by using appropriate water mist, with the optimum spray parameter was 3 L/min and 5 m/s for the studied scenario. Featured on K-class fires, this research can provide theoretical supports for performance-based fire safety design on water mists with proper parameters to control complicated kitchen fires in large-scale commercial kitchen buildings.
The concentration of carbon monoxide during fire suppression with water mist is one of the important parameters for safety evaluation of water mist system. Based on the experimental results of fire suppression with water mist in confined space, it is found that the carbon monoxide production rate during fire suppression is controlled in two modes. One is fuel controlled mode, and the other is water mist flux controlled mode. In the fuel controlled mode, the carbon monoxide production rate increases with the increase of fuel flux. In the water mist flux controlled mode, the carbon monoxide production rate increases with the increase of water mist flux. In order to classify the critical condition for transformation between these two modes, the concentration of water vapor in confined space is analyzed. The results show that the critical concentration of water vapor for the mode transformation is 25%-65.5%, which is consistent with Suh and Atryeya's conclusion.
Nuisance alarms have been identified as a leading cause of disabled smoke alarms in homes. In the 2013 Edition of NFPA 72, National Fire Alarm and Signaling Code, the Technical Committee approved requiring household alarms and detectors installed between 6 ft (1.8 m) and 20 ft (6.1 m) of cooking appliances to be listed for resistance to common cooking sources 2016 and for all household alarms, and detectors to be listed for resistance to common nuisances by 2019, respectively. There is currently no clear understanding of how “resistance to common nuisance sources” should be defined within these requirements. In this paper, Statistical data, surveys, and alarm installations were assessed to quantify the potential impacts of reducing nuisance alarms toward overall public safety and reduction of fire loss. Based on these reports, it has been estimated that elimination of nuisance alarms may reduce annual U.S. fire deaths by as much as 10%, or 214 deaths per year (1050 injuries). This number does not account for negative potential consequences on death and injury rates, such as increased alarm costs or decreased sensitivity to real fires. A review of laboratory test data and studies evaluating household installation performance was conducted to identify and characterize common household nuisance sources, such as cooking (60% to 80% of nuisance alarms), water mist (1% to 40%), or increased sensitivity from long term contamination (up to 70% of nuisance alarms). Detailed recommendations are made based on existing data to address remaining information gaps and develop new performance test protocols in ANSI/UL 217 and ANSI/UL 268 product standards in order to meet the NFPA 72-2013 requirements.
This paper presents an experimental study of fire suppression effectiveness with water mist containing FeCl2 additives.The investigation focuses on suppression effectiveness under various FeCl2 additives concentrations,working pressures and nozzle different height above the fire source . The experimental results show that: there is a significant impact on fire suppression effectiveness when adding FeCl2 to water mist. There is an optimum additive concentration of extinguishing fire, corresponding to the shortest extinguishing time, the least amount of water, the highest efficiency of extinguishing fire. The nozzle working pressures and nozzle position have effect on the performance of the water mist extinguishing: the greater the pressure is, the shorter water mist fire extinguishing time is. Under the same experimental conditions, the closer the water mist nozzles are to the oil pan, the shorter extinguishing time is.
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.
This paper begins with a brief statistical analysis to establish the significant contribution of cooking equipment fires to fire losses and injuries in Canadian homes. Due to lack of comprehensive fire loss data for Canadian homes, further analysis is focused on Alberta data. The most frequent ignition scenario, based on a top-down analysis of Alberta home fires, was the ignition of overheated cooking oil in pots, deep-fat fryers, or pans heated on stove tops. These fires also accounted for the majority of home fire injuries. Fire characteristics of cooking oils, which point to the importance of maintaining oil temperatures below their flash points, and thermostatically controlled deep-fat fryers as the best available solution to the problem are discussed.
A series of full-scale experiments were conducted in a mock-up commercial cooking area to study extinguishing mechanisms and effectiveness of water mist against cooking oil fires. The impact of water mist characteristics, such as spray angle, droplet size, flow rate, discharge pressure and type of nozzle, on the effectiveness of water mist against cooking oil fires was investigated. A series of oil splash experiments were also conducted to determine if the oil was splashed by water mist. In addition, the change in oil composition during heating and fire suppression was determined using Fourier Transform Infrared (FTIR) technique.The study showed that cooking oil fires were very difficult to extinguish, because they burned at high temperature and re-ignited easily due to changes in oil composition during heating and fire suppression. The water mist systems developed in the present work effectively extinguished 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.
PMMA and pine are chosen as two typical solid materials. The method based on the principle of oxygen consumption is applied, the Calorimetry System is used, and the heat release rates of solid combustion with different fluxes radiant heat are measured. Then the infection of radiant heat to the solid heat release rate is analyzed.
In a given confined space, temperature, heat fluxes, and toxic gases emitted by materials involved in the fire can be directly correlated to the HRR of a real fire. HRR affects the progress of the combustion directly and shows the performance of the fire. HRR of some typical combustibles, such as PMMA and pine, were measured by using the Cone Calorimeter under fire exposure radiation conditions. The results show that combustion state of solids is closely related with their construction and characteristics: the heat release rate curve the pine has two obvious peak value, but the heat release rate of PMMA increases stably and behaves like liquid. Exposure radiation has very big influence on the combustion and heat release rate of solid.
Designing fire is a key step in fire hazard analysis. How to design the heat release rate curve of the given fire scenario reasonably is a focus in recent research. This paper discusses the existing design fire model, improves the subsection-average method and the subsection-linear method based on previous research, and explains how to design fire curve by fire models.
Cooking oil fires in kitchens are difficult to extinguish as they are easy to re-ignite. Such kind of fires are different from the conventional flammable liquid fuel fires and have been classified into a new fire class, i.e. Class F, by some international recognized standard institutions such as National Fire Protection Association. Water mist fire suppression systems are proposed to suppress kitchen fires. In this paper, results in small-scale experiments using cone calorimeter on suppressing cooking oil fires with water mist will be reported. It is observed that good design of the system can suppress peanut oil fire effectively. There might be adverse effects on enhancing the combustion, producing more carbon monoxide and giving out more dark smoke for improper design.