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Experimental Study of the Interation Between the Water Mists and PVC Fire
Abstract
Effect of water mist on the small-scale solid fuel polyvinyl chloride (PVC) fire in the confined space has been studied experimentally with the heat release rate measured by a cone calorimeter in this paper.The water mist is generated by a single pressure nozzle and the diffusion flame is produced from PVC samples respectively. The LDV/APV system is employed to determine the water mist characteristics. The Cone Calorimeter is used to measure the heat release rate, oxygen and carbon monoxide concentrations and other important parameters of the interaction under various conditions.The results of the test showed that heat extraction cooling (flame cooling and fuel surface cooling) plays a dominating role to suppress the PVC fire, when the water mist with enough volume flux are applied to the diffusion flame in the confined space. The higher the operation pressure, the easier the suppression. The faster the PVC fire suppressed by water mist with large enough water flux, the less the total amount of toxic gases (CO, CO2) produced.
... With the increasing awareness of environmental protection, water mist is widely regarded as a clean and efficient fire-suppressing technology (Cui and Liu, 2021;Gupta et al., 2013;Dasgotra et al., 2021;Zhou et al., 2018Zhou et al., , 2019a due to its intrinsic non-polluting nature, high-efficiency, and little damage. Also, mist droplets cool the flame (Jenft et al., 2014), reduce radiant and convective heat transfer (Zhou et al., 2019a), and decrease the carbon monoxide concentration (Gupta et al., 2013;Zhang et al., 2007). Moreover, a water mist system can achieve huge savings in comparison to ventilation systems (Ingason et al., 2016). ...
... The theoretical model of energy transfer is constructed as shown in Fig. 2. In this model, the following assumptions are employed: the gas physical parameters (such as T g , c p,g , ρ g , ν, α, k g ) are uniform in the smoke layer; the influence of water mist on the smoke layer thickness in the carriage is neglected; the temperature of the carriage body T s is assumed to be ambient temperature T ∞ during the burning process. By developing previous correlations (Gupta et al., 2020;Maluk et al., 2017;Zhang et al., 2007), the energy correlation between smoke and the surroundings can be described as: ...
... Therefore, for such a train fire shielded by a carriage body, the suppression performance influenced by the water mist activation time is controlled by the competition between the fuel cooling and the inhibiting effect of the smoke layer. Obviously, the suppression mechanism is different from fires directly exposed to water mist (Jenft et al., 2014;Zhang et al., 2007;Zhou et al., 2019a). ...
In real tunnel fire scenarios, water mist has little opportunities to directly apply to train fires shielded by a carriage body. However, most models for heat transfer analysis assume direct contact between the fire source and mist droplets. It is of interest to find a method to evaluate the energy exchange between water mist and a shielded fire. To investigate the water mist suppression performance on a shielded fire, a full-scale experimental and theoretical study was performed by varying the activation time of the water mist system, working pressure, and the diameter of the mist droplets. The suppression performance is found to be dependent on the working pressure for the small mist droplets, and sensitive to the size of mist droplets at high working pressure. Moreover, the suppression performance is also influenced by the water mist activation time due to the competition of fuel cooling and the inhibition effect of the smoke layer. A theoretical model was developed to predict the energy exchange among smoke, water mist, and surroundings. It was found that in comparison to the indirectly restricted effect of cooling the carriage and fire, the direct heat loss between water mist and smoke is the main controlling mechanism. This study provides an important reference for the design of fire water system in the tunnel rescue station and is beneficial to the environmental protection of fire extinguishing sites.
... However, additional fan power is required for overcoming the airflow resistance of the evaporative cooler, which trades off the reduction of compressor power partly. Zhang et al. [7] reported that the application of evaporative precoolers improved the COP of air-cooled chillers by 14.7% under the climatic conditions of Tianjin. According to a reported simulation study [8], a decrease of 1.4-14.4% in chiller power was achieved when an air-cooled reciprocating chiller with an evaporative precooler operated under HPC. ...
... An alternative for evaporative cooler is to install a water mist system to pre-cool the air before entering the condenser. The water mist pre-cooling system is not a new concept, and has been applied successfully in the industries [12][13][14]. However, the application of water mist pre-cooling associated with a chiller system is uncommon. ...
This paper presents the effect of operating water mist system to enhance the energy efficiency of air-cooled chillers under various operating conditions. A thermodynamic model for an air-cooled chiller with twin refrigeration circuits coupled with a water mist system was developed and validated by measured operating data. The validated model was used to investigate how the thermal properties of the entering condenser air and the performance of the air-cooled chiller varied under different operating schemes with water mist pre-cooling. Under the conventional head pressure control (HPC) with a designed water mist generation rate, the coefficient of performance (COP) increased by up to 21.3%. The chiller performance could be improved further under variable condensing temperature control (CTC). Under CTC, chiller COP was increased up to 51.5% with optimal water mist generation rate. The potential energy savings of these chillers serving a representative office building in subtropical climate was evaluated, and CTC coupling with optimal water mist generation rate would reduce the annual total electricity consumption for cooling by 14.1%. The water consumption of the water mist system was comparatively small, comparing with the total water losses for an open-loop cooling tower system with equivalent heat rejection capacity.
... Liu et al., 2021;Liu et al., 2006;Lv et al., 2019;Pei et al., 2021). However, previous studies have mainly focused on the interaction between water mist and a single-fire, including solid, liquid, and gaseous fires (Chang et al., 2008;Grant et al., 2000;Liu et al., 2020;Wang et al., 2002Wang et al., , 2018Zhang et al., 2007). Ndubizu et al. (Ndubizu et al., 1998) proposed fire suppression mechanisms of the gaseous diffusion flame by water mist and determined the effects of droplet size and injection orientation of the water mist. ...
Single-fire and double-fire extinguishments by water mist were conducted to assess the similarities and differences. The double-fire extinguishment requires higher applied volume flux of the water mist and spray momentum, while it is achieved faster than the single-fire extinguishment, owing to the smaller size of the single flames of the double-fire. Both the air entrainment restriction among the two flames of the double-fire and the typical re-ignition phenomenon have a significant effect on the double-fire extinguishment. A double-fire merging from the burner surface is more difficult to be extinguished in terms of the critical operating pressure since the air entrainment restriction among the two flames of the double-fire is more intense. A double-fire with a smaller flame spacing requires a longer extinguishing time since re-ignition happens more easily. The equivalent diameter (De) is applied to calculate the plume–spray thrust ratio of the double-fire and evaluate the competition between the double-fire and the water mist quantitatively.
... An ISO 5660 cone calorimeter (Fire Testing Technology, UK), as shown in Fig. 2, was used to measure the combustion characteristics of different types of solid and liquid combustibles under various external heat fluxes Yongfeng et al., 2007). Samples are wrapped in aluminum foil prior to testing. ...
Vegetable oil residues, which are often used for biogas production, are prone to fires. The decomposition and fire behaviors of four vegetable oil residues, namely rapeseed oil residue (ROR), peanut oil residue (POR), gingili oil residue (GOR), and soybean oil residue (SOR), were investigated using elemental analysis, thermogravimetry-differential scanning calorimetry-derivative thermogravimetry (TG-DSC-DTG), Fourier transform infrared (FTIR) spectrometry, and a cone calorimeter. Based on the TG-DSC-DTG results, ROR is the residue most susceptible to spontaneous ignition and complete decomposition. Further, although the FTIR results showed that the functional group compositions of the four residues are similar, according to cone colorimetry experiments, SOR has the lowest critical heat flux and the lowest peak value of heat release rate under an external heat flux.
... When water mist is used to suppress Class A fires that can form carbon layers, as the evaporation rate of droplets decreases, water can penetrate the carbon layer between burned and unburned fuel and further prevent the spread of combustion (Wu et al., 2014). In PVC fire, where endothermic cooling (flame cooling and fuel surface cooling) plays a major role, the heat release rate of the combustible decreases at a rate of 9.5 kW/ m 2 /s (Zhang et al., 2007). ...
Due to its high efficiency and non-pollution, water mist fire extinguishing technology has attracted increasing interest and attention from various fire protection fields, including library fire safety, traffic hub station fire safety, ship fire safety and spacecraft fire safety. To support research and development of water mist fire extinguishing technology and its application in the field of battery fires, this paper begins by detailing the mechanisms by which water mist extinguish fires. The influence of internal and external factors on the fire suppression effectiveness of water mist is then discussed, such as water mist characteristics, additives, obstacles, ventilation conditions, fuel types, flame scales, followed by a review of researches of water mist technology in battery fires. In the final part, based on current research tendency, the paper provides future development direction and research ideas of water mist fire extinguishing technology and foresees the development prospects of its application in the battery fire field.
... Zhang et al. (2016b) analyzed the interaction between fire and water mist in long and narrow spaces, and found that the radiant heat flux attenuation and the fuel surface cooling are the controlling fire suppression mechanisms. Moreover, Liang et al. (2015) and Zhang et al. (2007) also found that the flame cooling and fuel surface cooling played a dominating role on suppressing the pool fires and PVC fires. Lemaire and Kenyon (2006) conducted a series of fire experiments in the Second Benelux Tunnel, and investigated the effects of detection systems, mechanical ventilation and sprinklers. ...
Rescue stations are essential for emergency evacuation in super-long railway tunnels. However, the deficiency of related studies aiming at improving the fire suppression performance of water mist system in fire scenarios limits its application significantly. In this work, 20 sets of full-scale water mist fire suppression experiments were conducted to examine the impacts of water mist system on smoke temperature characteristics, including water mist activation time (denoted by t), working pressure (P), k-factor (K) and longitudinal wind speed. Results show that when t = 3 min, P = 12 MPa, and K = 0.5, the best performance of temperature control could be achieved. Although there are violent temperature fluctuations in the train side, the smoke temperature could be easily restrained. Moreover, it is found that longitudinal ventilation is helpful to improve the visibility at platform and reduce smoke temperature. When P = 12 MPa, the coupling effect of water mist and longitudinal ventilation on cooling smoke is better. In addition, the non-dimensional maximum temperature rise is found to show a great cubical dependency on vertical height, and decreases along with a larger longitudinal distance for all cases. Also, under longitudinal ventilation, the non-dimensional maximum temperature rises are lower than that without longitudinal ventilation in the coverage area of water mist. Results of this work can provide a significant reference for the design of water mist system in railway tunnel rescue stations.
... Due to its advantages of cleanness and good fire suppression effectiveness, water mist fire suppression technology has been a subject of many investigations over the last decade. [18][19][20][21][22][23][24] Many achievements have been made in the methods of generating water mist, the measurement of spray characteristics, the fire suppression mechanisms and effectiveness, the influence factors, etc. 17,[25][26][27][28][29][30][31][32][33][34] However, the low pressure water mist systems with higher water flow rates, larger droplet sizes, high cost pipe network and nozzle and high requirements for water quality, are barely used in industrial and building fire, hence the applicability of water mist under low pressures has not been given enough research attention. But it demonstrated good performance in extinguishing unshielded pool fires and wood crib fires. ...
Fire suppression tests using low pressure twin‐fluid water mist under low pressure environments were carried out to exam the performance of water mist systems at low pressure environments. The experiment results show that the suppression time gets shorter for lower chamber pressure, and relevant total weight of water and nitrogen used decreases as the chamber pressure gets lower. For the case of 30‐cm diameter pool fire, the suppression times are 20.19, 7.5, and 2.24 under the chamber pressure of 60, 38, and 24 kPa, respectively. In case of a cargo compartments fire, it is suggested to open the ventilation valve of the cargo compartment at a high cruising altitude to relieve pressure, so as to achieve rapid fire suppression. When a fire happens at the position off the center below the water mist nozzle, the water mist suppression effects will be weakened. The fire size has little effects on the fire extinguishing process under pressure of 24 kPa. Under the critical atomization condition with the pressure differential between the inlet and outlet of the nozzle for water as 0.05 MPa (5.04 L/min), and the pressure differential for nitrogen as 0.10 MPa (10.97 L/min), the suppression time is the shortest as 18.66 seconds.
... The lowest oxygen concentration and highest CO 2 concentration measured during the test were 16.0% and 3.3%, respectively. Chang et al., Liu and Kim, Shu et al., and Liang et al. have assessed the performance of water mist fire suppression systems for the wet benches of semi-conductor plants (Liu and Kim, 2001;Shu et al., 2005;Zhang et al., 2007;Chang et al., 2008;Liang et al., 2015;Tang et al., 2019). The parameters in their tests included the size of the oil pan, quantity and position of nozzles, and operating pressure and duration of door opening. ...
This paper described full-scale tests of water mist fire suppression system under forced desmoking conditions. Pool fire was effectively suppressed in 25.0 and 37.0 s for 1,500.0 (test 1) and 3,000.0 (test 2) mL of oil with no ventilation, respectively. Moreover, under ventilation rates of 50.0 and 75.0 m³/min, the suppression time were lengthened to 54.0 s (test 1) and 202.0 s (test 2), and 102.0 s (test 1) and 222.0 s (test 2), correspondingly. However, the smoke exhaust had a strong effect on the water mist to result in fire could not extinguish, when the ventilation rate increased to 120.0 m³/min. The temperature distribution during the early period in the scenario of no ventilation has a higher magnitude than those scenarios of 50.0, 75.0, and 120.0 m³/min, because combustion proceeds smoothly to result in temperature increased rapidly at no ventilation. Furthermore, similar results presented in smoke concentration distribution at four scenarios (0, 50.0, 75.0, and 120.0 m³/min), and combustion occurred steadily at no ventilation to result in more smoke during the early period. This study employed a computer modeling to verify water mist system in a compartment space and determine how the water mist system could be optimized.
... Therefore, it is possible to improve the energy efficiency of air-cooled chillers by installing water mist system to pre-cool the outdoor air before entering condensers. The water mist pre-cooling system is not a new concept, and has been applied successfully in the industries (Cheung, Santos et al. 2006;Hsieh and Yao 2006;Zhang, Yongfeng et al. 2007). However, the application of water-mist system associated with a chiller system is not common, and a limited number of studies are found on the performance of chillers with water mist system . ...
This paper reports how the coefficient of performance (COP) of air-cooled chillers can be improved by adopting variable condensing setpoint temperature control and using mist evaporation to pre-cool ambient air entering the condensers to trigger a lower condensing temperature. Chiller models without and with water mist system were established, and the former was validated by using measured operating data of an installed screw chiller. With the validated model, the energy performance of air-cooled screw chillers with twin refrigeration circuits and water mist system serving a representative commercial building was studied. The results reveal that the chiller COP can be changed by various degrees from -0.3% up to +72% depending on the weather and load conditions, and the annual energy consumption can be reduced by 10.9% for a commercial building in subtropical climate.
Personnel inside health care facilities are mostly at a disadvantage during evacuation, therefore in the event of a fire, evacuation would possess certain difficulties and result in serious consequences. Use of conventional fire hydrants for fire extinction could damage equipment because of the amount of water used. To avoid this, the amount of water used was a key consideration during this study besides fire extinction performance. This research used newly developed mobile high pressure equipment and nozzle A with a K value of 3.7, and extinguished three standard wood cribs (7.5 MW), its performance being superior to that of the equipment used by the NRIFD (National Research Institute of Fire and Disaster).Using the equipment at a pressure of 49.3kgf/cm2 and discharge flow rate of 26 LPM, the time needed for extinction was 68s, 76s, and 60s,without any recrudescence within 2 min afterwards. Calculations showed that this system only required 33L of water for extinction, 27% less than the indoor hydrant, but was still effective, and it also showed no leakage of electricity under operation pressure and discharge flow rate. This research is a first to quantifiably analyze and compare the performance between mobile high pressure water mist equipment and indoor hydrants
Water mist, which is an alternative to halon fire-extinguishing agents, can maintain the clean environments and prevent the huge fire loss in diverse industrial fields. In the present experimental study, the spray characteristics of a twin-fluid nozzle for water mist and its heptane pool fire extinguishing performance were investigated. As the spray characteristics, the SMD (Sauter Mean Diameter) of water mist, discharged water flux distribution, downward air flow velocity, and inlet pressures of fluids were measured and analyzed. Subsequently, through the fire extinguishing experiments using three different heat release rate conditions, the fire extinguishing map, extinguishing time, water consumption, and water mist effect on the mass loss rate were examined in detail. In addition, the experimental data using the twin-fluid nozzle were compared and discussed with those using the single-fluid nozzle reported in a previous study. Based on the present experimental data of fire extinguishments, particularly under high air flow rate conditions, the twin-fluid nozzle showed high fire extinguishing performance. Moreover, compared with a previous study using the single-fluid nozzle, it was found that the twin-fluid nozzle can successfully extinguish liquid pool fire with shorter fire extinguishing times, lesser water consumption, and lower inlet pressures. Based on the present results, it was found that the air flow of the twin-fluid nozzle is an important factor that determines and affects its fire extinguishing performance. Further, the twin-fluid nozzle was found to possess a significant potential to considerably improve the performance of water mist fire suppression systems.
In an ISO 5660 Cone Calorimeter, heat fluxes were applied to a polyvinyl chloride–based floor covering to characterize their influence on the thermal decomposition parameters as well as on the concentrations of species emitted during the combustion process. Gas concentrations were quantified for identifying the fire behaviour and the decomposition chemistry. Thus, carbon monoxide, carbon dioxide, water, hydrogen chloride and oxygen with concentrations and emission yields of high consistency were encountered at all heat fluxes considered. Moreover, nitrogen monoxide, sulphur dioxide, hydrogen cyanide and lightweight hydrocarbons were observed with low concentrations and emission yields. Other species can be considered as negligible due to their concentrations close to zero at all heat fluxes studied. Furthermore, using the oxygen consumption method, heat release rate, total heat release and effective heat of combustion were also calculated for each irradiance level and were compared with data found in the literature.
Safety performance of straw powders, a primary component of biomass pellet fuel, remains challenging. In this work, three straw powders (soybean, peanut, and rape) were studied. Thermogravimetry and cone calorimetry were employed to investigate thermal oxidative decomposition characteristics and fire behaviors. Thermogravimetry (TG), micro-commercial thermogravimetry (DTG), and differential scanning calorimetry (DSC) curves showed that the thermal decomposition of the three samples proceeded in four stages. TG-DTG-DSC data also revealed that their ignition and burnout temperatures and mass loss rates were all distinct. Combustion indices of the three samples were ordered as RS > SS > PS. Based on the cone calorimetry results, critical heat fluxes for ignition were determined to be 25.31, 29.14, and 18.27 kW/m² for SS, PS, and RS, respectively. Critical fire properties such as ignition time, heat release rate intensity, and CO/CO2 ratio were influenced by biomass species and external heat fluxes. Compared with the other two samples, RS exhibited better burnout performance but was a greater fire hazard. Nevertheless, according to the hazard assessment, the three straw powder samples all had a high fire risk. Additional care must be taken in handling, storing, transporting, and utilizing straw powder in biomass pellet fuel processing.
This Study conducted a full-scale motorcycle fire experiment in it non- enclosed space with water mist nozzles variously located oil the ceiling at a height of 1-5 m. and oil the ground, and observed the effect of nozzle arrangement oil flame height and heat release rate The result,1; showed that the three nozzle arrangements all were able to reduce heat release rate and could effectively reduce the temperarture and height of flames One of them could extinguish the motorcycle fire. This indicated that water mist can work and the nozzle arrangement has it decisive influence Oil the performance of water mist Systems
Air-cooled chillers are widely used to provide space cooling in the subtropical regions at the expense of considerable energy. In order to improve the energy efficiency of the existing air-cooled chillers, installing water mist system coupled to these systems so as to add a spray of fine water droplets at the air inlet of the condenser seems to be a potential solution that deserves to be investigated and analyzed. Water mist pre-cooling allows the ambient air entering the condenser to cool from its dry bulb temperature to wet bulb temperature while the droplets are fully vaporized. There is a lack of detailed experimental studies on air-cooled chillers with water mist system. This paper aims to investigate how the energy performance of the air-cooled chillers can be improved by applying water mist to pre-cool ambient air entering the condenser coils under various operating conditions in Hong Kong via field measurements. The thermal properties of the air entering condenser coils at the different locations and the operating data related to chiller performance were measured. The energy effectiveness of water mist system for pre-cooling the air-cooled chillers under various operating conditions was assessed, the air-cooled chiller COP could be improved with water mist system by up to 29.5% in Hong Kong. © 2010 Faculty of Construction and Land Use, The Hong Kong Polytechnic University.
An analytical study has been conducted to investigate the effect of radiation heat loss on the spherical flame propagation in coal-dust clouds. This research can be valuable in the development of alternative fuels; and it can be used by the fire safety and control industry. The model includes the evaporation of the volatile matter of dust particles into a known gaseous fuel (methane) and the single-stage reaction of the gas-phase combustion. The radiation heat losses occur between the reaction zone and the surrounding environment (air). The study is within the framework of large activation energy and quasi-steady state assumptions. The theoretical predictions, including the burning velocity, are validated by the results presented in other works.
This paper investigates how water mist evaporative pre-cooling can be applied to air-cooled chillers to improve the chiller efficiency by on-site experimental studies. There is a lack of detailed experimental studies on the application of water mist system on air-cooled chillers. The experiment was conducted on a chiller plant with water mist system in a subtropical climate. The experimental results showed that the dry bulb temperature (DBT) of entering condenser air with water mist pre-cooling could drop by up to 9.4 K from the ambient air temperature, and the approach could be as low as 0.5 K. A thermal effectiveness of up to 0.91 was obtained in using the water mist system. The pre-cooled condenser air enabled a drop of the condensing temperature by up to 7.2 K, and the chiller coefficient of performance (COP) could be improved in varying degrees by up to 18.6%. This study demonstrates that the water mist system coupled to air-cooled chillers is an energy-efficient and environment friendly technique, which has significant potential to improve the efficiency of air-cooled chillers and reduce the electricity demand for the commercial and industrial sector.
A set of small-scale experiments was carried out to study the effect of a water spray on the re-ignition characteristics of solid fuels. The influence of other key parameters, such as the incident heat flux and pre-bum, was also investigated. The experiments were conducted on specimens of wood and PMMA using a cone calorimeter. A water spray was produced by a small commercial nozzle. As expected, the effect of water on the re-ignition time was found to be significant. It was also found that the re-ignition characteristics of charring materials, such as wood, are quite different from non-charring materials (e.g. PMMA) mainly due to the structural differences. Based on the experimental observations a set of empirical correlations was obtained for both wood and PMMA samples. Predictions of the re-ignition time made by these correlations agree well with the measurements. Simulations of the re-ignition times were also performed using a detailed mathematical model. Comparisons with the experimental data are provided.
Over the last 8 years there has been a great deal of activity in the field of "water mist" research anddevelopment. The term "water mist" is used here to refer to fine water sprays which have 99 percent ofthe volume of the spray in drops with diameters less than 1000 microns. In early 1996, the pace ofdevelopment continues to be rapid. Activities are occurring on a variety of fronts, ranging fromtheoretical investigations into extinguishing mechanisms, computational fluid dynamics modeling, andthe development, patenting and manufacturing mist-generating equipment. This review is intended toidentify the agencies involved in this effort, describe the work that is presently underway, and highlightthe major developments to date.
Few research papers have been published on the suppression of fire with water. This study reviews key studies reported in the literature. In the process, attempts are made to identify areas of future research which should contribute to valid prediction methods for suppression of real-world fires.
Fuel-spill, post-crash, and cabin fires account for 40% of fatalities occurring in aircraft accidents. Radiation is, by far, the single most dominating mode of heat transfer and hence, the severity of the accidents can be reduced through its attenuation. Water sprays have been considered useful in attenuating fire radiation. The present study characterizes the engineering aspects of the water droplet attenuation. The optimum and the most effective droplet sizes were determined using a simple radiation attenuation model and solving through an iteration method. Only infrared wavelengths (0·6 to 25 μM) have been considered in the study. The maximum attenuation factor was attained when the droplet radius was approximately equal to the wavelength. The results, which are presented graphically, also indicated optimum droplets of radius equal to the incident wavelength for minimum transmissivity. The effects of the path length and the volume of water on the transmissivity and target temperature are illustrated through a typical example.
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.
Turbulent, recirculating gas flows resulting from interactions of water droplet sprays with large-scale buoyancy sources are difficult to predict without the use of numerical techniques, especially when spray-induced gas motion is considered. One such flow occurs when a negatively buoyant methane cloud, generated during LNG spills in a wind, is dispersed by a line water spray. Numerical predictions of the ratio of average methane vapor concentration downwind of the line spray to the upwind value correlate as a function of the ratio of methane momentum in the vapor cloud to water momentum in the spray.
The feasibility of using water sprays for the control of offshore oil/gas well blowout fires has been addressed. Considering the sheer scale of the problem, knowledge from a fundamental viewpoint is going to be required in order to extrapolate laboratory-sized flame studies up to full scale. Available data and appropriate literature concerned with the application of water sprays as a jet diffusion flame suppression/extinguishment agent have been reviewed. Small pneumatic atomizing nozzles using H2 gas, both as the flame source as well as the atomizing driver, have been used to scale high momentum jet flames and to study the effect of water on the flame. Thermodynamic equilibrium was shown to be an effective guide in interpretating the results. The effect of flame temperature reduction due to water sprays has been observed to correlate with a single spray parameter—the median drop diameter. Directions for further study have been indicated.
The rate of heat release is the most important parameter for characterising an unwanted fire. The oxygen consumption principle has accelerated the development and use of equipment of measure rate of heat release. The Cone Calorimeter is the most significant of small scale instruments in this field. The paper describes the apparatus and theory. Applications including correlation with large scale fire tests are discussed.
Experiments were carried out on the extinguishment of burning slabs of three different thicknesses. The results are presented in terms of experimental correlations of the mass lost during control and time required for control of the fire as functions of the rate of water application. A simple power law with exponent in the range (− 1·5) –(− 1·75) was found for the dependence of the first two variables on the latter.The predictions of a theoretical scheme, based on a pyrolysis model for the solid, a simple estimate of the flame energy feedback and an extinguishment criterion for the flame, were found in good agreement with the experiment, The calculations confirmed the existence, already indicated by the experiment, of a minimum rate of water application ([mdot]w =0·19 –0·24 mg/ cm/s) below which no mass is saved.Furthermore, the theory indicated an upper limit, at [mdot]w = 0·8 – 1·0 mg/cm/s, above which the efficiency of the water spray decreases.
This paper reports a study of the interaction of a sprinkler water spray with the fire-induced hot layer using the field modelling technique. Data obtained in the large test room of the recent Swedish experiments reported by Ingason and Olsson (1992) are used to validate the results. The problem is divided into a gas phase and a liquid phase. For the gas phase, the set of conservation equations for mass, momentum and enthalpy of air flow induced by the fire is solved numerically using the Pressure Implicit Splitting Operator (PISO) algorithm. For the liquid phase, the sprinkler water spray is described by a number of droplets with initial velocity and diameter calculated by empirical expressions for the nozzle at different operating water pressures and flow rates. The trajectory of each droplet is calculated by solving the equation of motions, by including the dragging and heat transfer with the hot layer. The water droplet is assumed to be non-evaporating and only the source terms in the gas momentum and enthalpy equations of the air flow included the interaction effects with water droplets, i.e. the ‘Particle-Source-in-Cell’ method. The predicted results include the gas flow, temperature and smoke concentration field; the shape of the water spray; and some relevant macroscopic parameters such as amount of convective cooling, drag-to-buoyancy ratio, etc. The average smoke layer temperature and the smoke layer interface height are also calculated. The effect of the mean droplet size on those parameters is illustrated. Finally, a comparison of the water density received at floor level in cases with and without the fire is made.
This work describes observations and measurements from the interaction of a fine water spray from a hollow cone nozzle, with purely buoyant diffusion flames from a natural gas ceramic-plate burner located directly underneath the nozzle. The burner plate was instrumented with thermocouples cemented on its upper and lower surfaces to assess the influence of the spray on the burner temperature. A set of thermocouples was also used to measure plume centerline temperatures above the burner plate. An imaging system was used to record the presence of droplets near the burner surface, and a narrow angle total radiation detector was used to measure changes in local flame radiation. A limited number of measurements of the steady state O2 and CO concentrations along the plume centerline were also carried out.For the conditions tested, the plume-to-spray thrust ratio was large, resulting in negligible direct penetration of the droplets into the fire region. A consequence of the low spray thrust was an almost droplet-free region above the flame. The observed cooling of the ceramic burner when the spray was applied was due to decreased radiant emission from the flame as well as deposition and evaporation of droplets entrained into the plume near the burner. The centerline plume temperatures did not change significantly upon application of the spray, at least within the error limits of thermocouple measurements. However, there was a significant decrease in O2 and an increase in CO concentrations along the plume centerline upon application of the spray. An energy balance on the ceramic-plate burner, together with the experimental data, yielded estimates of the water deposition rate on the burner surface.
The present study investigates how water sprays affect fire intensity, the burning rate of fuel and the relationship between droplet size and degree of water penetration. Downward-directed sprays which interact with a small-scale opposed gasoline pool fire are experimentally investigated in an open environment. It is shown that the burning rate of fuel is always greater under this opposed spray-fire plume arrangement compared to the freely burning condition, i.e. without water sprays, when fire extinction does not arise. These results imply that water sprays are able to enhance an oil fire. Furthermore, very small droplets are shown to be ineffective for fire extinction by cooling because they do not reach the fuel surface through fire plumes. Therefore, within a small-scale gasoline pool fire in an open environment, the mechanism of the fire extinction by water sprays is concluded to act via the cooling of the fuel surface, which will lead to the suppression of fuel evaporation, rather than the cooling of the fire plume itself.
Recent experimental work on fine water sprays indicates that they may have a wider application in the fields of fire extinction and combustion suppression than previously anticipated. In this paper, the means of producing fine sprays are briefly examined and the major results of some case studies are reviewed. A few unexpected positive results have come to light, especially with regard to using fine mists to protect against fires involving live electrical equipment. However, it is still premature to advocate the use of fine sprays for many applications.
"Drysdale's book is by far the most comprehensive - everyone in the office has a copy...now including me. It holds just about everything you need to know about fire science." (Review of AnIntroduction to Fire Dynamics, 2nd Edition). After 25 years as a bestseller, Dougal Drysdale's classic introduction has been brought up-to-date and expanded to incorporate the latest research and experimental data. Essential reading for all involved in the field from undergraduate and postgraduate students to practising fire safety engineers and fire prevention officers, An Introduction to Fire Dynamics is unique in that it addresses the fundamentals of fire science and fire dynamics, thus providing the scientific background necessary for the development of fire safety engineering as a professional discipline. An Introduction to Fire Dynamics. Includes experimental data relevant to the understanding of fire behaviour of materials; Features numerical problems with answers illustrating the quantitative applications of the concepts presented; Extensively course-tested at Worcester Polytechnic Institute and the University of Edinburgh, and widely adopted throughout the world; Will appeal to all those working in fire safety engineering and related disciplines.
Cabin water sprays for fire suppression: an experi-mental evaluation. Civil Aviation Authority Paper 93009 (Fire Research Station, UK)
- S A Ames
Ames, S.A., 1993, Cabin water sprays for fire suppression: an experi-mental evaluation. Civil Aviation Authority Paper 93009 (Fire Research Station, UK).
Advances in spray drop size and velocity measurement capabilities for the characterization of fire protection systems
- Bachalo
Bachalo, W.D., 1993, Advances in spray drop size and velocity measurement capabilities for the characterization of fire protection systems. Proceedings of Water Mist Fire Suppression Workshop, 1 –2 March, Gaithersburg, MD, USA, 75– 92.
Suppression within a simulated computer cabinet using an external water spray. Annual Conference of Fire Research: Abstracts, NISTIR 5499
- W L Grosshandler
- D L Lowe
- K A Notarianni
- W J And Rinkinen
Grosshandler, W.L., Lowe, D.L., Notarianni, K.A., and Rinkinen, W.J., 1994, Suppression within a simulated computer cabinet using an external water spray. Annual Conference of Fire Research: Abstracts, NISTIR 5499, National Institute of Standards and Tech-nology, Gaithersburg, 75– 76.
Radiant heat attenuation in fire water sprays, Proceed-ings of the Seventh International Fire Science and Engineering Conference
- T Log
Log, T., 1996, Radiant heat attenuation in fire water sprays, Proceed-ings of the Seventh International Fire Science and Engineering Conference, 26–28 March, Cambridge, England, 425– 434.
Characteristics of water mists for fire sup-pression in enclosures A closer look at the fire extinguishing proper-ties of water mist
- J R Mawhinney
Mawhinney, J.R., 1993, Characteristics of water mists for fire sup-pression in enclosures, Proceedings of Halon Alternatives techni-cal Working Conference, 10– 11 May, Albuquerque, NM, USA. Mawhinney, J.R., 1994, A closer look at the fire extinguishing proper-ties of water mist, Proceedings of the 4th International Symposium on Fire Safety Science, 47–60.
CFD modeling of liquid pool fire suppression using fine water sprays. Annual Conference of Fire Research: Abstracts, NISTIR 5499, National Institute of Standards and Technology
- G Hadjisophocleous
- K Knill
Hadjisophocleous, G. and Knill, K., 1994, CFD modeling of liquid pool fire suppression using fine water sprays. Annual Conference of Fire Research: Abstracts, NISTIR 5499, National Institute of Standards and Technology, Gaithersburg, 71–72.
Experiment study on interaction of water with fires in a confined space
- Yao Bin
- Liao Guangxuan
- Fan Weicheng
Yao Bin, Liao Guangxuan and Fan Weicheng, 1997, Experiment study on interaction of water with fires in a confined space, Fire Safety Science, 6(2): 48– 52.
Incentive for use of misting sprays as a fire suppression flooding agent
- Alpert
Alpert, R.L., 1993, Incentive for use of misting sprays as a fire sup-pression flooding agent. Water Mist Fire Suppression Workshop Proceedings, NISTIR 5207, National Institute of Standards and Technology, Gaithersburg, 31– 35.
An Introduction to Fire Safety Science
- Fan Weicheng
Fan Weicheng, 1993, An Introduction to Fire Safety Science (Hubei Science and Technology Press, China).
The role of fire dynamics in design of water mist fire suppression systems
- International Association
- Fire Safety
- Science
- Boston
- Usa Ma
- J R Mawhinney
International Association for Fire Safety Science, Boston, MA, USA. Mawhinney, J.R., 1996, The role of fire dynamics in design of water mist fire suppression systems, Proceedings of the Seventh Inter-national Fire Science and Engineering Conference, 26–28
Basic research on fire suppression. Annual Conference of Fire Research: Abstracts, NISTIR 5499, National Institute of Standards and Technology
- A Atreya
- T Crompton
Atreya, A. and Crompton, T., 1994, Basic research on fire suppression. Annual Conference of Fire Research: Abstracts, NISTIR 5499, National Institute of Standards and Technology, Gaithersburg, USA, 167–170.
Experiment study on interaction of water with fires in a confined space
- Yao Bin
Basic research on fire suppression
- Atreya
Experimental study on the interaction of water mists with fires in the confined space
- Yao Bin
Cabin water sprays for fire suppression: an experimental evaluation
- S A Ames
Suppression within a simulated computer cabinet using an external water spray
- Grosshandler
The role of water in the suppression of fires
- Heskestad