20Chapter1The Evolution of Fire ScienceTable 1-6Common conversionfactorsandsymbolslength1m=3.2808ftA1m2=10.7639ftareadensity1kg/m3=0.06243lb/ft3pQenergy1.kJ=0.94783Btuheatq1kJ=0.94783Btu9heatflowrate1W=3.4121Btu/hrQ1W=3.4121Btu/hrenergy release rateqheatflow rate1W/cm2=0.317Btu/hr-ft3per unit area,1W/cm2=10.kW/m2heatflux1kJ/kg-C=0.23884Btu.lb-oFcspecific heatk1W/m-C=0.5778Btu/hr-ft-oFthermal conductivity1m2/s=10.7639ftz/sαthermal diffusivity1atm=14.69595Ib/in?pressure=1.01325x105N/m2P1N/m2=1Pascal (Pa)Table1-7Scientificnotations,prefixesPrefixMuitiplierAbbreviationT1012tera109Ggiga106Mmega103kilokh102hecto10-2ccenti10-3millim10-6microH10-9nnano10-12ppico10-18aattoNote:Forexample,105=1000and10-=0.001
- ~-c_h_ap_te_r_1_Th_e_E_vo_1u_t_io_n_of_F_ir_e_sc_ie_nc_e Table 1-6 Common conversion factors and symbols. length 1 m = 3.2808 ft I area 1 m2 = 10.7639 ft2 A density 1 kg/m3 = 0.06243 lb/ft3 p energy 1 kJ = 0.94783 Btu Q heat 1 kJ = 0.94783 Btu q heat flow rate 1 W = 3.4121 Btu/hr q energy release rate 1 W = 3.4121 Btu/hr Q heat flow rate 1 W/cm2 = 0.317 Btu/ hr-ft2 q" per unit area, heat flux 1 W/cm2 = 10.kW/m2 specific heat 1 kJ/kg-°C = 0.23884 Btu.lb-°F C thermal conductivity 1 W/m-°C = 0.5778 Btu/hr-ft-°F k thermal diffusivity 1 m2/s = 10.7639 ft2/s a pressure 1 atm = 14.69595 lbf/in2 = 1.01325 x 105 N/ m2 1 N/ m2 = 1 Pascal (Pal p Table 1-7 Scientific notations, prefixes. Multiplier Prefix Abbreviation 1012 tera T 109 giga G 106 mega M 103 kilo k 102 hecto h 10-2 centi C 10-3 milli m 10-S micro µ 10-9 nano n 10-12 pico p 10-1s atto a Note: For example, 103 = 1000 and 10-3 = 0.001
Chapter1 The Evolution of FireScienceSummaryFire is a chemical reaction,usually involving oxygen from the air, that producesenoughenergytobeperceived.Typically,thatenergyreleaserateperunitvolumeis sufficient to cause a skin burn in seconds.The destruction byfire throughouthistory has been dramatic, from the possible cause of the dinosaur extinction toconflagrations in large cities into the twentieth century. Although, the UnitedStates has one of the highest per capita deaths due to fire, it is only approximate-ly one-tenth of the annual deathrate due tomotor vehicleaccidents.Conse-quently,there has notbeen a high incentiveto study uncontrolled fire.However,research in fire has progressed throughout the world,and its results canbeveryuseful tofire safety design andtofireinvestigation analysis.Visualizationoffirephenomena is a first step in understanding and in developing tools for fire pro-tection.Tobeableto usethesetools,the studentmustunderstand scientificunitsand terminology.A goal in understanding this book is to at least come to think offiresinterms ofkilowatts.Activities1.Find examples of the significance of fire in4.Examine the SFPEHandbook,theproceed-history,ings of the IAFSS (Fire Safety Science series)on topics of interest toyou.Discuss howyou2.Examine the statistics of fire and the attitudecan benefit from this science. Is it under-of society on fire safety.standable?3.Test the validity of fire statistics.For exam-5. Identify fire organizations and laboratoriesple,does the prevalence of electrical firearoundtheworld.causes at night suggest something else? Whatpercentage of fires are actually reported?Review Questionkw1.Convertthefollowing30,000BTU/hr℃85°F0.0015Wmw℃kw400°F1,385W℃kW/m2695°F6.5W/cm2
Chapter 1 The Evolution of Fire Science Aeti11ities summarv Fire is a chemical reaction, usually involving oxygen from the air, that produces enough energy to be perceived. Typically, that energy release rate per unit volume is sufficient to cause a skin burn in seconds. The destruction by fire throughout history has been dramatic, from the possible cause of the dinosaur extinction to conflagrations in large cities into the twentieth century. Although, the United States has one of the highest per capita deaths due to fire, it is only approximately one-tenth of the annual death rate due to motor vehicle accidents. Consequently, there has not been a high incentive to study uncontrolled fire. However, research in fire has progressed throughout the world, and its results can be very useful to fire safety design and to fire investigation analysis. Visualization of fire phenomena is a first step in understanding and in developing tools for fire protection. To be able to use these tools, the student must understand scientific units and terminology. A goal in understanding this book is to at least come to think of fires in terms of kilowatts. 1. Find examples of the significance of fire in history. 4. Examine the SFPE Handbook, the proceedings of the IAFSS (Fire Safety Science series) on topics of interest to you. Discuss how you can benefit from this science. Is it understandable? 2. Examine the statistics of fire and the attitude of society on fire safety. 3. Test the validity of fire statistics. For example, does the prevalence of electrical fire causes at night suggest something else? What percentage of fires are actually reported? Re11iew ouestion 1. Convert the following: 85°F oc 400°F oc 695°F oc 5. Identify fire organizations and laboratories around the world. 30,000 BTU/hr kW 0.0015 W mW 1,385 W kW 6.5 W/cm2 kW/m2
Chapter1 The Evolution of Fire ScienceReferences9.W.P.Meade,AFirst Pass at Computing the Costs of1.H.Rossotti,Fire(Oxford:Oxford UniversityPress,FireSafetyinaModernSociety,NIST-GCR-91-5921993),22(Gaithersburg,MD:National Instituteof Standards2. Accident Facts (ltasca, IL: National Safety Council.and Technology,March1991).1995).10. W.G. Berl, ed.,The Use of Models in Fire Research,3.R.C.Cochrane,Measures for Progress,AHistory ofPub.786 (Washington,DC:National Academy ofthe National Bureau of Standards (Washington, DC:Sciences,National Research Council,1961),U.S.DepartmentofCommerce,1974),131.11.P.J.DiNenno,ed.,The SFPEHandbookof FirePro-4.T.Wilmot,World Fire Statistics CentreBulletin12tection Engineering,2d ed.,(Quincy,MA:National(Geneva:The GenevaAssociation,1996).FireProtectionAssociation,June1995).5.N.N.Brushlinsky,A.P.Naumenko,and S.V12.J.G.Quintiere, B.J.McCaffrey,andW.Rinkinen,Sokolov,"Responseto QueryaboutFireDeathsin"Visualization of RoomFire Induced Smoke Move-Russia" (Letters tothe Editor),Fire Technology 31,mentand Flow in a Corridor,"Fireand Materials2,no.3, (August, 1995).no.1(1978):18-246.FireResearchonCellularPlastics:TheFinalReport13.M.Kokkala,andW.J.Rinkinen,Some ObservationsoftheProducts Research Committee,Library ofontheShapeof ImpingingDiffusionFlames,Res.Congress Cat.No.80-83306 (1980).Rep. 461 (Espoo,Finland: VTT, Technical Research7.H.W.Emmons, FireResearch Abstracts andCentre of Finland,1987)Reviews10,no.2 (1968):1338.W.Strunk, Jr., and E.B.White,The Elements ofStyle (NewYork:MacMillan,1979),47Additional ReadingLyons,J.W.,Fire,Scientific American Library (NewYork:Hemisphere Publishing Co.; Symposia three,London:Elsevier;Svmposium four,InternationalYork:ScientificAmericanBooks,1985)Association forFire Safety Science.Fire Safety Science, Proceedings of the First-FourthInternational Symposia.Symposia one andtwo,New
-.-¥.•L_ _ _ ~~~~~~ Chapter 1 The Evolution of Fire Science Re#erences 1. H. Rossotti, Fire (Oxford: Oxford University Press, 1993), 22. 2. Accident Facts (Itasca, IL: National Safety Council, 1995). 3. R. C. Cochrane, Measures for Progress, A History of the National Bureau of Standards (Washington, DC: U.S. Department of Commerce, 1974), 131. 4. T. Wilmot, World Fire Statistics Centre Bulletin 12 (Geneva: The Geneva Association, 1996). 5. N. N. Brushlinsky, A. P. Naumenko, and S. V. Sokolov, "Response to Query about Fire Deaths in Russia" (Letters to the Editor), Fire Technology 31, no. 3, (August, 1995). 6. Fire Research on Cellular Plastics: The Final Report of the Products Research Committee, Library of Congress Cat. No.80-83306 (1980). 7. H. W. Emmons, Fire Research Abstracts and Reviews 10, no. 2 (1968): 133. 8. W. Strunk, Jr. , and E. B. White, The Elements of Style (New York: MacMillan, 1979), 47. Additional Reading Lyons, J. W., Fire, Scientific American Library (New York: Scientific American Books, 1985). Fire Safety Science, Proceedings of the First-Fourth International Symposia. Symposia one and two, New 9. W. P. Meade, A First Pass at Computing the Costs of Fire Safety in a Modern Society, NIST-GCR-91-592 (Gaithersburg, MD: National Institute of Standards and Technology, March 1991). 10. W. G. Berl, ed., The Use of Models in Fire Research, Pub. 786 (Washington, DC: National Academy of Sciences, National Research Council, 1961), v. 11. P. J. DiNenno, ed., The SFPE Handbook of Fire Protection Engineering, 2d ed., (Quincy, MA: National Fire Protection Association, June 1995). 12. J. G. Quintiere, B. J. Mccaffrey, and W. Rinkinen, "Visualization of Room Fire Induced Smoke Movement and Flow in a Corridor," Fire and Materials 2, no. 1 (1978): 18-24. 13. M. Kokkala, and W. J. Rinkinen, Some Observations on the Shape of Impinging Diffusion Flames, Res. Rep. 461 (Espoo, Finland: VTT, Technical Research Centre of Finland, 1987). York: Hemisphere Publishing Co.; Symposia three, London: Elsevier; Symposium four, International Association for Fire Safety Science
Chapter2combustioninNaturaFiresLearning ObjectivesUponcompletionofthischapter,youshouldbeableto:Identify different forms of natural fire:diffusion flames,spontaneous ignition, smolder-ing,and premixed flames.Understand howa candleflame,abasicdiffusionflame,works.Understand,from a quantitative viewpoint,the naturalforms offire including aspects ofsize, shape, and speed.23
combustion in Natu•al Pi•es Upon completion of this chapter, you should be able to: ■ Identify different forms of natural fire: diffusion flames, spontaneous ignition, smoldering, and premixed flames. ■ Understand how a candle flame, a basic diffusion flame, works. ■ Understand, from a quantitative viewpoint, the natural forms of fire including aspects of size, shape, and speed. 2:S
Chapter2CombustioninNatural FiresINTRODUCTIONNaturalfireprocessescantakedifferentforms:diffusionflames,smoldering,spontaneous combustion,and premixed flames.Byexamining the candleflame withsimpleexperiments derived from Michael Faraday's 1850 work,you can deducehowadiffusionflameworks.Itisalsoshownthattheprocessofflamingignitioninvolves a premixedflame and a pilotflame.Spontaneous combustion requires nosuch pilot, but occurs because of itself and its environment. Spontaneous com-bustion can take either of two pathways:(1) flaming combustion-a diffusionflame or(2)smoldering combustion-aslow solid fuel oxidationattemperaturesas lowas 40o°C.We describe theseprocesses and presentquantitative information.FIREAND ITSINGREDIENTSCombustion orfire is a chemical reaction involving the release ofenergy,some ofwhich is in theform of light-aflame.Mostfuels are composed ofcarbon,hydro-gen,and oxygen,Somefuels,particularlyplastics,can contain otherelements suchasnitrogen,chlorine,andfluorine.Todefineachemical reactionasfire,sufficientperceptibleenergymustbereleased:Therateofenergyreleaseperunitvolumeofthe chemical reaction determines whether that reaction is fire.The size of theflame is not a factor.On the threshold of fire this incipient energy level might beabout1o3or1000kW/m,whichissufficienttoheatwater1°Cpersecond.Sus-tainedfirereactionscanpossessmanyymoretimesthisenergydensityasmuchas 1010kW/m3.The temperature in this reaction zone can reach 2,000°C forgaseous fuels and 1,ooo°C for solid fuel reactions (smoldering).fire triangleThe fire triangle, as shown in Figure 2-1, is a concept used to describe theaconceptdescribingfire processes.The elements of the fire triangle are essential to the existence of afireas consisting offire.Thetriangle consists of(1)fuel combining with (2)oxygen in a chemical reac-three ingredients: fuel,tion to release (3)energy and other chemical products.The energy causes heat tooxygen,andenergybe transferred to the solid or liquid fuel to maintain vaporization into gaseous fuelortomaintain thefuel temperature to ensurethe chemical reaction can persist.Ifwetake away sufficientfuel oroxygen,orreducethe energyby extinguishment orretardant agents,thefirewill notsurvive.FUELHEATCAUSES VAPORIZATIONANDMAINTAINSREACTIONCHEMICALREACTIONTEMPERATUREFigure2-1ThefireOXYGENENERGYtriangle.(21% IN AIR)
fire triangle a concept describing fire as consisting of three ingredients: fuel, oxygen, and energy Figure 2-1 The fire triangle. Chapter 2 combustion in Natural Fires INTRODUCTION Natural fire processes can take different forms: diffusion flames, smoldering, spontaneous combustion, and premixed flames. By examining the candle flame with simple experiments derived from Michael Faraday's 1850 work, you can deduce how a diffusion flame works. It is also shown that the process of flaming ignition involves a premixed flame and a pilot flame. Spontaneous combustion requires no such pilot, but occurs because of itself and its environment. Spontaneous combustion can take either of two pathways: (1) flaming combustion-a diffusion flame or (2) smoldering combustion-a slow solid fuel oxidation at temperatures as low as 400°C. We describe these processes and present quantitative information. FIRE AND ITS INGREDIENTS Combustion or fire is a chemical reaction involving the release of energy, some of which is in the form of light-a flame. Most fuels are composed of carbon, hydrogen, and oxygen. Some fuels, particularly plastics, can contain other elements such as nitrogen, chlorine, and fluorine. To define a chemical reaction as fire, sufficient perceptible energy must be released: The rate of energy release per unit volume of the chemical reaction determines whether that reaction is fire. The size of the flame is not a factor. On the threshold of fire this incipient energy level might be about 103 or 1000 kW/m3 , which is sufficient to heat water 1°C per second. Sustained fire reactions can possess many more times this energy density-as much as 1010 kW/m3 . The temperature in this reaction zone can reach 2,000°C for gaseous fuels and 1,000°c for solid fuel reactions (smoldering). The fire triangle, as shown in Figure 2-1, is a concept used to describe the fire processes. The elements of the fire triangle are essential to the existence of a fire. The triangle consists of (1) fuel combining with (2) oxygen in a chemical reaction to release (3) energy and other chemical products. The energy causes heat to be transferred to the solid or liquid fuel to maintain vaporization into gaseous fuel or to maintain the fuel temperature to ensure the chemical reaction can persist. If we take away sufficient fuel or oxygen, or reduce the energy by extinguishment or retardant agents, the fire will not survive. FUEL CHEMICAL REACTION HEAT CAUSES VAPORIZATION AND MAINTAINS REACTION TEMPERATURE OXYGEN - ENERGY (21% IN AIR)