Minutes from the EUSAS-BRANDFORSK WORKSHOP on Smoke Detection, Sept 26-27 1994

Temperature and air speed values normally characteristic of a heated and ventilated room are compared with values for a fire in the room so that a first approximation can be calculated for size of fire overcoming the effects of the initial conditions

Numerical Prediciton of Heat Flux from Flame in Room Fire

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

Small scale experiments and theoretical aspects of flame extinguishment with water mist

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

Flame Sizes in a Small Scale Stack: Pilot Experiments

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

Risker vid naturgasuppvärmning i bostäder : Etapp 2: brandrisker och behovsbedömning av kontrollåtgärder

Naturgas är ett rent bränsle som endast innehåller små mängder föroreningar, [1]. Jämfört med kol är föekomsten av föroreningar i naturgas vanligen 1000 ggr mindre. Man får därför inga problem med svaveldioxid, tungmetaller, klorerade föroreningar etc i avgaserna. Vid normal drift bildas mycket lite sot och de huvudsakliga förbränningsprodukterna är vatten och koldioxid. Vatten ställer normalt inte till några problem om avgaskanalen är rätt utformad. Koldioxid betraktas som en miljögas men utsläppet från naturgas är per energienhet lägre än för andra bränslen, Tabell 1.1

Spridning av No₂ från en naturgaseldad väggpanna

I rapporten presenteras mätningarn, som har gjorts under perioden december 1987 till april 1988, av Nox-halten i luften i omgivningen av avgasutsläpp från en naturgaseldad villapanna. Bl.a. redovisas hur olika vindhastigheter och vindriktningar inverkar på Nox-halten i pannans omgivning

Computers in Physics Teaching at the University of Lund

We describe two completely different implementations of computers in teaching physics aimed at two very distinct target groups. First, a program with the aim to teach physics and analytical thinking to non-physics majors is described, and second a large-scale research school focusing on distance teaching at the graduate level is presented. Both are from the University of Lund, in Lund, Sweden

Combustion of Chemical Substances and the Impact on the Environment of the Fire Products: 1/3 Scale Room Furnace Experiments

This report describes the results obtained from fire tests in a 1/3-scale room. The aim of the study was to investigate how changes in external radiation and oxygen supply affect the production of smoke and toxic gases. The ventilation was varied to simulate under- and well-ventilated fires. The thermal exposure to the materials was varied to simulate fires of different sizes. Fifty-nine tests were performed, with polystyrene, FR polystyrene, polypropylene, nylon and PVC. Measurements were made of the contents of O2, CO2, CO, NOx, and HC in the exhaust gases. The impact of external radiation was mainly to increase the pyrolysis rate, and thus the rate of heat release, and to drive the fire into under-ventilation. The degree of ventilation proved to have the greatest impact on the combustion efficiency. The smoke production was almost constant for polypropylene and nylon. The CO production appeared to be the most complex of the parameters to describe, and the expected increase in CO yield at low yields of CO2 could not be seen. The generation of NOx was low for the two substances without chemically bound nitrogen, but for nylon, the generation was significant. The production of low molecular weight HC was essentially constant for all three materials. Almost all the carbon was recovered in wellventilated fires, but at under-ventilated conditions, only 30% of the carbon from the he1 was detected. The toxic potency of the exhaust gases was estimated using the N-gas model, and proved to be relatively low. Lack of oxygen and the production of carbon oxide had the greatest impact on the toxicity for polystyrene and polypropylene, while NO, represented the main part for nylon. The survival fraction and the decomposition products from the original materials are not considered in the model. It can therefore not be assumed that the model reflects all aspects of the toxicity problem

Naturgas Säkerhetsnivå Riskanalys

Denna rapport har tillkommit på uppdrag av NUTEK och avser att belysa riskerna med distribution och industriell användning av naturgas. Tidigare har en rapport avseende naturgasinstallationer i hemmen utgetts [1,2]. Rapporten inleds med en allmän diskussion om risker. Vidare tas frågan om lagstiftning, tillsyn, kontroll och utbildning för naturgasanvändning i olika lander upp. Dessutom har en retrospektiv sökning efter statistik om naturgasolyckor samt incidenter gjorts. En kort genomgång av hur man beräknar konsekvenser av naturgasutsläpp görs också