Temperature and velocity correlations in room fires for estimating sprinkler actuation times

Automatic sprinklers are increasingly used in residential occupancies to provide active fire protection. These sprinklers, known as quick response and residential sprinklers, may be located either at the ceiling (pendent-style) or on a wall (sidewall-style). Though several fire models are available for estimating actuation times for sprinklers located under unobstructed ceilings, these use engineering correlations that do not apply to residential-sized rooms. Thus, data are needed for estimating sprinkler actuation times for residential occupancies.This paper reports on fire tests that were conducted in various sized rooms to obtain temperature and velocity data for 73 kW, 100 kW, and 147 kW fires. The data were then used to develop nondimensional correlations for temperature and velocity at the sprinkler locations. The temperature data revealed a significant temperature transient in the hot gas layer, and thus a nondimensional correlation describing the transient phenomenon was developed. These correlations compared reasonably well with experimental data, and they were used to estimate the sprinkler actuation times. The estimates were in reasonable agreement for the pendent sprinkler, except for the smallest fire in a 4.27 m by 4.27 m occupancy. The estimates for sidewall sprinkler acuation were significantly lower than experimental values. This may have been due to the sprinklers' heat losses, which were not accounted for in the calculation.     

Actuation of sprinklers at high ceiling clearance facilities

As buildings with a high ceiling clearance are becoming increasingly common, making proper assessments of whether or not the ceiling sprinklers would actuate becomes very critical to designing adequate fire protection systems for such buildings. Two sets of fire test data under high ceiling clearances pertinent to growing 3-dimensaional fires and steady plane pan fires were analyzed to estimate maximum ceiling heights from the given fire sources that would allow actuation of ceiling sprinklers. The threshold fire sizes that would actuate ceiling sprinklers at a given ceiling clearances were also computed for growing fires and steady pan fires. Comparisons of the estimated threshold fire sizes between the growing fires and the pan fires indicate that assessing sprinkler actuations based on pan fire tests, which is a commonly used practice, will be likely to lead to a wrong conclusion. The analysis shows that a much smaller fire size than what pan fire tests might indicate would be needed to actuate sprinklers on high ceilings.     

Automatic fire detection in road traffic tunnels

Fire detection experiments in a road traffic tunnel were performed in the Runehamar test tunnel 5th–8th March 2007. The Runehamar test tunnel is a full profile road traffic tunnel, 1.65 km long, located outside Åndalsnes, Norway. The goal was to examinate smoke and heat detection systems to determinate what kind of principle best suited for detecting a fire in an early stage. The systems were tested during small Heptane pool fires, varying between 0.16 m² and 1 m², giving heat release rates from 0.2 MW to 2.4 MW accordingly, and one car fire of about 3–5 MW, and with wind conditions varying from 1.1 m s^?1 to 1.6 m s^?1. The size of the fires, were designed to be in the range from impossible to difficult to detect. The results were conclusive. Earliest detection of a car fire, fire starts inside, was by smoke detection given fixed limits (3000 μg m^?3). With open pool fires, or immediate flames, continues fibre optical heat detection systems was faster given the limits 3 °C/4 min.     

Computational fluid dynamics studies on the effectiveness of sidewall sprinklers to suppress the fire at the undercarriage of mass rapid transit train

This paper reports the computational fluid dynamics (CFD) studies of sidewall automatic fire sprinklers installed adjacent to and in close proximity to the trains to suppress the fire at the undercarriage of the trains in the stabling yard, for the sake of protection of the train assets. Plume cooling due to water spray from fast response sprinklers is simulated with the sprinkler model available in Fire Dynamics Simulator (FDS). Concurrently, fire suppression due to the interaction between the water and fire source is simply modelled with the assumption of an exponential reduction of the prescribed burning/pyrolysis rate. The objective is to gain some insight about the effectiveness of sidewall sprinklers proposed to prevent the fire from spreading to adjacent trains. CFD simulation results demonstrate that it is highly likely that the undercarriage fire will spread to both the connected train-car and its adjacent train, if only overhead sprinklers are provided in the design. Due to the obstruction posed by the train, water cannot reach the fire source. Sidewall sprinklers are very effective to detect, control, suppress and even extinguish the fire, hence preventing the spread of fire. When sidewall sprinklers are installed on both sides of the trains, further asset protection may be extended successfully to the connected train cars. This study implies that the installation of sidewall sprinklers may be a practical solution for the protection of train assets in the stabling yard.     

Estimating effectiveness of state-of-the-art detectors and automatic sprinklers on life safety in residential occupancies

The report provides a qualitative assessment of the life safety impact of early warning fire detection and automatic sprinkler technology in residential occupancies. This assessment is based on the results of full-scale studies and statistics on residential fire fatalities from the NFIRS data base. Estimates of the impact of three alternatives, smoke detectors, standard automatic sprinklers, and residential sprinklers, are provided for major fire hazard scenarios in residential occupancies. The results of this study indicate that significant life safety benefits can be derived from broad application of detectors and sprinklers in all residential buildings. National Bureau of Standards Note: This is a condensed version of the more detailed document NBSIR 84-2819 bearing the same title as above. The document is available in limited quantities from the National Bureau of Standards or it may be purchased through National Technical Information Services (NTIS). Reference: Edward K. Budnick, “Estimating Effectiveness of State-of-the-Art Detectors and Automatic Sprinklers on Life Safety in Residential Occupancies.” Fire Technology, Vol. 20, No. 3, August 1984, p. 5.     

Experimental study of the effectiveness of a water system in blocking fire-induced smoke and heat in reduced-scale tunnel tests

A water system, consisting of several water mist nozzles, has been installed in a reduced-scale tunnel. Its effectiveness in blocking fire-induced smoke and heat is tested, with and without longitudinal ventilation. A total of 14 fire tests have been carried out, with 250 ml methanol in an iron tray (25 cm × 20 cm) as fuel. Temperatures have been measured by 30 thermocouples, located upstream and downstream of the fire location. The aim is to assess the effectiveness of the water system in preventing smoke spread and in reducing the temperature in the tunnel. Interaction of the water with the fire is avoided. The impact of water pressure, ventilation velocity and nozzle arrangement on the effectiveness in smoke blocking and temperature reduction is discussed. The result confirms that the water system effectively reduces the temperatures and prevents smoke spreading in the absence of longitudinal ventilation. However, strong longitudinal ventilation (0.8 m/s ventilation velocity in the reduced-scale tunnel, corresponding to critical velocity in full-scale (1:10) tunnel) reduces the effectiveness in blocking the smoke spreading by the water system, although the temperature reduction downstream the water system remains in place. Higher water pressure makes the cooling effect stronger, because more and smaller water droplets are injected into the tunnel. For a given level of water pressure level, the impact of the nozzle row configuration is small in the tests.     

Suppression of sodium fires with liquid nitrogen

Sodium has unusual fire hazards, including autoignition when heated in air or exposed to liquid water. Owing to limitations of existing suppression agents for sodium pool fires, suppression using liquid nitrogen (LN₂) is examined here. Sodium pools of 5–80 g were heated in stainless steel beakers. At about 290 °C, pool surface autoignition occurred and caused a rapid pool temperature increase. Vapor phase combustion occurred when the pools reached 320–450 °C, ultimately leading to pool temperatures up to 700 °C. For suppression tests, LN₂ delivery (at 2.7 g/s) began when the fires became fully-developed, near a pool temperature of 600 °C. Liquid nitrogen was found to be an effective suppression agent. The minimum amount of LN₂ required to suppress a fully-developed sodium pool fire was found to be about three times the initial sodium pool mass.     

Heat release characteristics of ethanol-water mixtures: Small-scale experiments

Small-scale pool fire tests of ethanol-water mixtures are described in this paper. The main goal of the tests was to obtain data on the heat release rate per unit area, the total heat release per unit area, and the effective heat of combustion of such mixtures with ethanol percentage of 20 vol% or more. The results can be utilised in the interpolation and extrapolation of these quantities for different ethanol percentages and irradiance levels. In addition, the results give information on the heat release of possible pool fires of alcoholic beverages in a retail store in the case of a fully developed fire. It was concluded that significant fire load is not formed until the ethanol percentage of the alcoholic beverage is ca. 20 vol% or more. The data reported can also be used as an input to simulations of ethanol-water mixture pool fires in the performance-based fire safety design.     

某高架仓库火灾风险数值模拟

利用FDS对某高架仓库火灾风险进行数值模拟,并分析快速响应早期抑制喷头的控火效果,探讨机械排烟形成的负压对火灾蔓延的影响。结果表明,运用快速响应早期抑制喷头可以有效地防止火灾蔓延,而布置货架喷头可以进一步提高仓库的安全性;布置货架喷头时,货架内喷头的动作温度应比顶板喷头动作温度低;加入机械排烟时必须合理计算机械排烟量,避免负压引起新鲜空气进入火场。     

The use of AFFF in sprinkler systems

This paper reports the results of a series of fire tests to measure the effectiveness of a 1% aqueous film forming foam concentrate against flammable hydrocarbon fires when applied through conventional, automatic, wet-pipe sprinkler systems using closed sprinklers. Note: The author presented this paper at the NFPA annual meeting held in Chicago, Illinois in May 1975.     

Scale similarity on ceiling jet flow

In this study, empirical formulae previously derived for describing the decrease in temperature rise, the decrease in velocity, the thermal boundary layer thickness, the momentum boundary layer thickness, the Gaussian thermal thickness, and the Gaussian momentum thickness of a ceiling jet flowing upward along the steepest run of an inclined ceiling were applied to a full-scale scenario. The coefficients in these formulae were determined through a series of pool fire tests conducted using a flat, unconfined model ceiling with dimensions of 2.5 m×3.0 m, and fixed ceiling clearance of 1.0 m. To verify the applicability of the developed formulae to actual fires, another series of pool fire tests were conducted using a flat, unconfined full-scale ceiling with dimensions of 7.0 m×14.0 m and a maximum ceiling clearance of 3.0 m. The proposed formulae were confirmed to be applicable to a full-scale scenario and to describe the ceiling jet flow accurately.     

The effect of fuel area size on behavior of fires in a reduced-scale single-track railway tunnel

A set of experiments was carried out in a 1/9 reduced-scale single-track railway tunnel to investigate the effect of fuel area size on the temperature distribution and behavior of fires in a tunnel with natural ventilation. Methanol pool fires with four different fuel areas 0.6 × 0.3 m² (1 pan), 1.2 × 0.3 m² (2 pans), 2.4 × 0.3 m² (4 pans) and 3.6 × 0.3 m² (6 pans), were used in these experiments. Data were collected on temperatures, radiative heat flux and mass loss rates. The temperature distribution and smoke layer in the tunnel, along with overflow dimensions and radiant heat at the tunnel entrance were analyzed. The results show that as the fuel area enlarges, the fire gradually becomes ventilation-controlled and the ceiling temperature over the center of fire source declines. Burning at the central region of fire source is depressed due to lack of oxygen. This makes the temperature distribution along the tunnel ceiling change from a typical inverted V-shape to an M-shape. As observed in the experiments, a jet flame appeared at tunnel entrances and both the size and temperature of the flame increased with the enlargement of fuel area leading to a great threat to firefighters and evacuees in actual tunnel fires.     

Time-dependent smoke yield and mass loss of pool fires in a reduced-scale mechanically ventilated compartment

Technical and pure grades of the combustibles heptane and dodecane were used in a series of small-scale fire tests conducted in a 1 m³ compartment that was mechanically ventilated at 5 and 8 air changes per hour (ACH). Combustible mass loss rates, soot mass concentrations, soot size distributions, several gas species concentrations, and compartment temperatures were measured during the fire. Results for the two pure-grade hydrocarbons were compared with results obtained for their respective technical grades. Technical-grade dodecane produced the highest soot emissions; pure n-heptane produced the lowest. Soot size distributions of all four combustibles attained a steady profile whose modal diameter was about 200 nm. Underventilated fires showed higher carbon monoxide yields than soot yields. Both compartment ventilation rates produced similar results, although the fire self-extinguished earlier for 5 ACH.     

Full-scale fire tests and the development of design criteria for sprinkler protection of mobile shelving units

In early 1991, a new sprinkler system was planned for the existing National Archives/National Library of Canada building in Ottawa. A major challenge in the design and installation of the sprinkler systems was to protect mobile compact shelving units located in the three levels below grade. Storage of documents in these shelving units is typically within 178 mm of the concrete slab ceiling. The minimum clearance permitted by the sprinkler system installation standard is 457 mm from the sprinkler deflector to the top of the storage. To conform with the sprinkler design standard, the top level or levels of storage would have had to be removed and additional storage space acquired. Because of the annual cost of this additional storage, an investigation was begun to determine feasible alternatives that would permit a reduction in clearances between sprinklers and storage, while maintaining an acceptable level of fire safety. This paper describes the series of five full-scale fire tests that were conducted to assess various fire protection options. Based on these tests, design criteria were developed for a sprinkler system using quick response horizontal sidewall sprinklers to protect the mobile shelving units. An overview of this technically based fire protection system for use in protecting shelving units with reduced clearance is also presented.     

Field test and evaluation of residential sprinkler systems: Part I

A series of full-scale fire tests involving sprinkler installations was conducted in 1979 and 1980 in a two-story residence in Los Angeles, CA, and in a mobile home in Charlotte, NC. Previous laboratory tests, including full-scale room fire tests, had indicated that a prototype “quick-response” sprinkler was effective in controlling residential home fires. More full-scale fire tests under less controlled and more operational conditions were considered necessary to confirm or deny these scientific and engineering judgments. The prime objective of the program was to test the performance of alternative sprinkler designs to “control” the development of fire in single-family dwellings and mobile homes. National Fire Protection Association Editor's Note: This paper is the first of three papers reporting on full-scale residential sprinker fire tests conducted under Grant 79027 for the U.S. Fire Administration by the National Fire Protection Association. In this paper, the objectives of the test program are outlined; the test facilities, Prototype sprinkler, water supplies, sprinkler system design, and instrumentation are described; and the scenarios for the total of seventy-six tests conducted are summarized. The second paper (February 1984 issue) will focus on the results of the test and the conclusions drawn from them and the third (May 1984 issue) will cover a study of the comparative activation times of sprinklers and smoke detectors in the mobile home tests. Mr. Cote is Assistant Vice President (Engineering & Technical Services) for the NFPA. He served as project manager for the test series insofar as the NFPA had overall management responsibilities for the program.     

Gas temperatures in heavy goods vehicle fires in tunnels

Large-scale fire tests were carried out with heavy goods vehicle (HGV) cargos in the Runehamar tunnel in Norway. The tunnel is a decommissioned, two-way-asphalted road tunnel that is 1600 m long, 6 m high and 9 m wide, with a slope varying between 0.5% uphill and 1% downhill. In total four tests were performed with fire in an HGV set-up and a longitudinal ventilation flow of approximately 3 m/s. In three tests, mixtures of different cellulose and plastic materials were used; in the fourth test a commodity consisting of furniture and fixtures was used. In all tests the mass ratio was approximately 82% cellulose and 18% plastic. A polyester tarpaulin covered the cargo.One purpose of the large-scale tests was to obtain new relevant gas temperature-time data from large-scale HGV fires in tunnels. There is presently a lack of such information for road tunnels. The maximum heat release rates produced by the four different fire loads varied between 66 and 202 MW resulting in maximum gas temperatures at the ceiling ranging between 1281 and 1365 °C. A comparison with literature values shows that the gas temperatures obtained here are uniformly higher than those obtained in other similar large-scale test series conducted using solid materials. A mathematical correlation of a temperature–time curve is given and this is the best representation of the measured temperature and a combination of frequently used temperature curves for tunnels (the HC curve and the RWS curve).     

住宅火灾解决方案

火灾统计数据表明家庭和其他类似居住空间的火灾死亡人数占建筑物火灾总死亡人数的70%.在住宅中使用家用喷头是解决该问题的理想途径.介绍家用喷头的特点和其系统设计的基本方法,同时也呼吁修订规范以便更好地保护人民的生命和财产.