| 1. |
- Andersson, Berit, et al.
(författare)
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Simulated Fires in Substances of Pesticide Type
- 1999
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In order to characterise fires in chemical warehouses, 38 medium scale experiments have been conducted. The experiments were performed in a 0.66m3 combustion chamber. On-line measurements were made of combustion gases (CO2, CO, HC and NOx), mass loss, smoke, temperatures, external radiation and phi-values. Intermittently gas and soot samples were collected and analysed for content of organic compounds and amount of soot produced. Main variables during the experiments were external radiation, fire diameter, opening configuration and ventilation condition. The medium scale was chosen in order to give a test method which is more convenient to work with, less expensive than full-scale experiments and still rather well simulates the conditions in a real fire.
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| 2. |
- Andersson, Petra, et al.
(författare)
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An instrument for determining the total water content in air when extinguishing fires
- 1999
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Ingår i: Fire and Materials. - 1099-1018. ; 23:4, s. 187-192
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Tidskriftsartikel (refereegranskat)abstract
- n instrument suitable for measuring the total water content both as small liquid droplets and as vapour in the air, in water mist total flooding extinguishing tests, is presented. The instrument consists of a heater and a Vaisala humidity meter. The Vaisala humidity meter is capable of measuring relative humidity at temperatures up to 180°C. The instrument has a measuring range of 0-600g/m3, a sample rate of 1 L/min, a time constant of 5-10 s and an accuracy of ±40 g/m3. Accurate results are obtained when used outside the direct spray from a nozzle. If the instrument is placed in the spray the total water content can be either over- or underdetermined, depending on which part of the instrument faces the spray.
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| 3. |
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| 4. |
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| 5. |
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| 6. |
- Andersson, Petra, et al.
(författare)
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Limitations of Water Mist as a Total Flooding Agent
- 1998
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Ingår i: Journal of Fire Protection Engineering. - : SAGE Publications. - 1042-3915. ; 9:4, s. 31-50
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Tidskriftsartikel (refereegranskat)abstract
- The limitations of water mist in acting as a total flooding agent are discussed in this paper. The paper focuses on water mist consisting of droplets 1-100 µm in diameter. Water mists are very efficient as an extinguishing media if they are present in the flame. There are, however, several problems associated with introducing the water mist into the flame: the spray reaches only a short distance; small water droplets have a very short lifetime; droplets coagulate into larger droplets; large droplets hit obstacles such as walls and therefore have difficulties in being dispersed throughout the protected volume.
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| 7. |
- Andersson, Petra, et al.
(författare)
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Small scale experiments and theoretical aspects of flame extinguishment with water mist
- 1996
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The present study focuses on extinction of flames with water mist where surface cooling effects are neglected i.e. water mist as a total flooding system where the direct spray cannot reach and cool all burning items in the protected volume. The study includes a survey of the production and properties of water mist such as different types of nozzles and means to describe droplet size distribution. Properties of jets and sprays are discussed as well as water droplet movement, fall and evaporation. Three different series of experiments were conducted with different hydraulic atomising nozzles. In the first series, droplet size distribution and water spray distribution measurements for the nozzles were conducted. The measurements showed that the droplet size distribution ranged from a Sauter Mean Diameter of approximately 35 - 85 µm, all dependent on the water pressure and the configuration of nozzles. The measurements show that considerably larger droplets are formed when individual nozzles are placed together. This can be explained by a coalescence effect when droplets from the sprays of the nozzles collide. The second series of experiments were done using a tubular propane gas bumer where water and propane were mixed prior to reaching the burner outlet. Based on the tests, the specific amount of extinguishing medium required (Required Extinguishing Medium Portion, REMP = m, / m, i.e. the ratio of the agent quantity to fuel quantity consumed) is given as a quantitative measure of the efficiency of the agent. The lower the REMP value, the more efficient the agent. The water pressure ranged between 40 and 80 bar which provided for droplet sizes with a Sauter Mean Diameter in the order of 35 pm. The results show that the amount of water needed for extinguishment by weight is between 1.2 - 2,2 times the amount of propane gas. The decrease in droplet sizes decreased the amount of water needed. Another observation was that the heat release rate of the fire is not affected until extinction occurs. A REMP-value of 1,2 - 2,2 corresponds to a water content of 100 – 200 g/m3 protected volume which is in agreement with theoretical values. Finally, a series of tests were conducted in a 113 scale room using a propane gas fire. Parameters such as location of the fire, the location of the nozzle, water flow rate and the size of the room opening were varied. In these tests the water content needed was in close agreement with the values obtained from the REh4P experiments and the theoretical values. These tests also highlighted the problem of delivering the droplets to the fire. To achieve "total flooding" in an actual situation, nozzles covering the complete protected compartment, with additional nozzles under obstructions would be needed. To make droplets follow the air flows inside a room and behave more like a gaseous total flooding agent, requires droplets of a size in the order of 1 - 20 µm.
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| 8. |
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| 10. |
- Karlsson, Björn, et al.
(författare)
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Flame Sizes in a Small Scale Stack: Pilot Experiments
- 1995
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- For the last many decades industry and insurance companies have been interested in protecting high racked goods from rapid fire growth. This has mainly been done by installing sprinklers of various types and designs in order to either extinguish the fire or control it. The efficiency of such protection measures is, however, very much dependant on the geometry of the stacks, their height, floor area, the flue spacing, etc. and the flammable characteristics of the stored goods. A research project was initiated by the Swedish Fire Research Board (BRANDFORSK) to throw some light on the aforementioned geometric aspects of the problem. The main part of the project is to be carried out at the Swedish National Testing and Research Institute (SP) but a pilot study was initiated at Lund University, with some participation from scientists at SP. The work carried out at Lund University consisted of two parts. Firstly, Thomas [l] carried out a litterature survey of earlier experiments and summarized the main findings. Secondly, some experiments were made on reduced scale to examine the effect of the geometry of a pile of inert goods on the flames from a burner. This report describes the work carried out in this second part of the pilot study.
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| 11. |
- Tuovinen, Heimo, et al.
(författare)
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Sensitivity calculations of tunnel fires using CFD
- 1996
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Ingår i: Fire Technology. - 0015-2684. ; 32:2, s. 99-119
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Tidskriftsartikel (refereegranskat)abstract
- Detailed numerical simulations of fires in road tunnels were carried out using the CFD code JASMINE. Fire tests performed in the Ofenegg tunnel have also been validated. A parametric study of fires in an arbitrary 300-m-long tunnel was made, in which the influence of fire size, tunnel width, ventilation and ground slope was investigated. The movement of hazardous temperature and smoke regions as a function of time was calculated to investigate escape possibilities from the tunnel in case of fire.
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| 12. |
- Yan, Zhenghua, et al.
(författare)
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A two-equation turbulence model and its application to a buoyant diffusion flame
- 1999
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Ingår i: International Journal of Heat and Mass Transfer. - 0017-9310. ; 42:7, s. 1305-1315
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Tidskriftsartikel (refereegranskat)abstract
- A modified k–ε two-equation turbulence model was developed to improve the consideration of the important buoyancy effect on turbulence and turbulent transport, which is a serious deficiency of the standard buoyancy-modified k–ε model. The present model was tested against both plane and axisymmetric thermal plumes and a buoyant diffusion flame. The model was found to be stable, computationally economic, promising and applicable to complex situations. The predicted plume spreading rates and velocity and temperature profiles agreed well with experimental measurements. When compared with the standard buoyancy-modified k–ε turbulence model, this model gives significantly improved numerical results.
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| 13. |
- Yan, Zhenghua, et al.
(författare)
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CFD and experimental studies of room fire growth on wall lining materials
- 1996
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Ingår i: Fire Safety Journal. - 0379-7112. ; 27:3, s. 201-238
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Tidskriftsartikel (refereegranskat)abstract
- CFD simulation and experimental tests have been carried out to study the room corner fire growth on combustible wall-lining materials. In the CFD simulation, the turbulent mass and heat transfer, and combustion were considered. The discrete transfer (DT) method was employed to calculate the radiation with an absorptivity and emissivity model employed to predict the radiation property of combustion products including soot, CO2 and H2O, which are usually the primary radiating species in the combustion of hydrocarbon fuels. The temperature of the solid boundary was determined by numerical solution of the heat conduction equation. A simple and practical pyrolysis model was developed to describe the response of the solid fuel. This pyrolysis model was first tested against the Cone Calorimeter data for both charring and non-charring materials under different irradiance levels and then coupled to CFD calculations. Both full and one-third scale room corner fire growths on particle board were modelled with CFD. The calculation was tested with various numbers of rays and grid sizes, showing that the present choice gives practically grid- and ray number-independent predictions. The heat release rate, wall surface temperature, char depth, gas temperature and radiation flux are compared with experimental measurements. The results are reasonable and the comparison between prediction and experiment is fairly good and promising.
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| 14. |
- Yan, Zhenghua, et al.
(författare)
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Fast, narrow-band computer model for radiation calculations
- 1997
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Ingår i: Numerical Heat Transfer Part B: Fundamentals. - : Informa UK Limited. - 1040-7790 .- 1521-0626. ; 31:1, s. 61-71
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Tidskriftsartikel (refereegranskat)abstract
- A fast, narrow-band computer model, FASTNB, which predicts the radiation intensity in a general nonisothermal and nonhomogeneous combustion environment, has been developed. The spectral absorption coefficients of the combustion products, including carbon dioxide, water vapor, and soot, are calculated based on the narrow-band model. FASTNB provides an accurate calculation at reasonably high speed. Compared with Grosshandler's narrowband model, RADCAL, which has been verified quite extensively against experimental measurements, FASTNB is more than 20 times faster and gives almost exactly the same results.
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| 15. |
- Yan, Zhenghua, et al.
(författare)
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Numerical investigations of rack storage fires
- 1999
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Ingår i: Fire Safety Science. - 0925223255 ; , s. 1075-1086
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A number of numerical simulations of rack storage fires have been carried out, with various fuel types and burner outputs. Both the standard buoyancy-modified k - turbulence model and a recently developed turbulence model which significantly improves the consideration of the buoyancy effect on turbulence and turbulent transport, were used to study the turbulence of the buoyant flow. The flamelet concept, coupled to a prescribed probability density function, was employed to model the non-premixed combustion process. Sooting was modeled by solving the balance equations for mass fraction and number density considering nucleation, surface growth, coagulation and oxidation. The discrete transfer method was used to calculate radiation, with the radiation properties of the main radiating species - carbon dioxide, water vapour and soot, provided by a fast, narrowband model. The results, including heat flux and gas temperature profile, were analyzed and compared with experimental measurements. The comparisons showed considerably improved agreement for the new model. Copyright International Association for Fire Safety Science.
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| 16. |
- Yan, Zhenghua, et al.
(författare)
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Numerical Prediciton of Heat Flux from Flame in Room Fire
- 1997
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A number of CFD (Computational Fluid Dynamics) calculations were carried out to simulate the large scale room corner fire, which is an important scenario for the evaluation of the fire performance of the surface lining material. Considered are turbulent gas flows, turbulent combustion, radiation and heat conduction inside solid boundary. Heat transfer from flame and hot gas is calculated, with the important radiation component presented by discrete transfer (DT) method and the convection heat transfer considered by the wall function. An absorptivity and emissivity model was employed to predict the radiation property of combustion products including soot, CO2 and H2O, which are usually the primary radiating species in the combustion of hydrocarbon fuels. Configurations are a square burner flame in the corner of the standard full scale fire room, with three different standoff distances: 0 cm, 5 cm and 10 cm, and two different burner outputs: 40 kW and 150 ItW. Totally, six cases were studied. The results, including the temperature and heat fluxes, are discussed and compared with experimental measurements.
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| 17. |
- Yan, Zhenghua, et al.
(författare)
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Three-dimensional computation of heat transfer from flames between vertical parallel walls
- 1999
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Ingår i: Combustion and Flame. - 0010-2180. ; 117:3, s. 574-588
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Tidskriftsartikel (refereegranskat)abstract
- The heat transfer from turbulent diffusion flames between vertical walls has been computed for different wall and burner configurations. The buoyancy-modified k- model was used to study the turbulent characteristics of the flow. The flamelet concept, coupled to a prescribed probability density function, was employed to model the nonpremixed combustion process. With the nucleation, surface growth, coagulation, and oxidation considered, sooting was modeled by solving the balance equations for mass fraction and number density. The radiation from the main radiating species - carbon dioxide, water vapor and soot - was calculated using the discrete transfer method. A recently developed fast, narrow-band model was adopted to provide the radiation properties of the radiating species. Computations were performed for different cases by varying the wall separation and burner output. The results were analyzed and compared with experimental measurements, with which they showed good agreement. The effects of wall separation and burner output on heat transfer were faithfully reproduced.
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