Chapter1TheEvolutionofFireScienceHEATTRANSFERPRODUCTSTURBULENTTURBULENTMIXINGMIXINGONAIRFigure 1-5FUELPhenomena in aLOWSPEEDBUOYANTFLOWSroomfiregrowth.fire.12 The results were accurately established using a scalemodel withglass wallsand colored smoketo make the processes visible.Thesephotographs show theclassicalrepresentation ofanapparentuniform smokelayerfillingtheupperhalfof a compartment (Figure 1-6)and the complexrecirculating flows thatoccurbothinthesmokelaverandtherelativelyclearspacebelow(Figure1-7).Figure1-6also illustrates themixing of smokeintothelower clearspace (atthe right)asair enters throughawindowand entrains smoke.Figure1-8 shows fascinating flame patterns as aresult of flames impingingona ceiling.13Thepatterns depend on fuel type,fuel flowrate,and spacingtotheceiling.No form of computer modeling can anticipate these results.SCIENTIFIC NOTATIONIn order to relate concepts and principles behind fire phenomena,we must firstqualitativelyunderstand the behavior of fire.More importantly,we must under-International Systemofstand the information and methods used toquantitatively describe specificfireUnits or Standardphenomena.But someknowledge of physics and algebra is needed.Some basicsInternational (SI)Unitsofunitsofmeasure,symbols,and scientificnotationwill providethefoundationthesystemof unitsforforourquantitativeanalyses.measurementIn today's world,despitethe lagging of the United States,the InternationaladoptedbytheSystem of Units (SI) is in widespread use.The scientific community has univer-sciencecommunity
Chapter 1 The Evolution of Fire Science Figure 1-5 Phenomena in a room fire growth. International System of Units or standard International lSll Units the system of units for measurement adopted by the science community TURBULENT~.-+~ . MIXING FUEL LOW SPEED BUOYANT FLOWS fire. 12 The results were accurately established using a scale model with glass walls and colored smoke to make the processes visible. These photographs show the classical representation of an apparent uniform smoke layer filling the upper half of a compartment (Figure 1-6) and the complex recirculating flows that occur both in the smoke layer and the relatively clear space below (Figure 1-7). Figure 1-6 also illustrates the mixing of smoke into the lower clear space (at the right) as air enters through a window and entrains smoke. Figure 1-8 shows fascinating flame patterns as a result of flames impinging on a ceiling. 13 The patterns depend on fuel type, fuel flow rate, and spacing to the ceiling. No form of computer modeling can anticipate these results. SCIENTIFIC NOTATION In order to relate concepts and principles behind fire phenomena, we must first qualitatively understand the behavior of fire. More importantly, we must understand the information and methods used to quantitatively describe specific fire phenomena. But some knowledge of physics and algebra is needed. Some basics of units of measure, symbols, and scientific notation will provide the foundation for our quantitative analyses. In today's world, despite the lagging of the United States, the International System of Units (SI) is in widespread use. The scientific community has univer-
Chapter1 The Evolution of FireScience40.08m.057mFIREON35TEMP.&CORRIDORTEMP.TRAVERSETRAVERSEIk=1.30NOSOFFITWg/Wp=3.2W./W=1(a)(b)We/Wo=3.2We/Wo=1/2(c)(d)Figure1-6 Smokelayerinascalemodelcorridorsubjecttoa roomfire (Wp=11cm)atthe leftand exitsthroughdoorwayofwidth (W)atthe right.FromWe/Wp=2We/Wo=1/4Quintiere et al..(e)(f)Ref.12
_ L_ _ C11_ap_te_r_1_,_he_E_vo_1u_ti_·o_n_of_F_ir_e_sc_ie_nc_e Figure 1-6 Smoke layer in a scale model corridor subject to a room fire (Wv = 11 cm) at the left and exits through doorway of width (WE) at the right. From Quintiere et al., Ref. 12. ~ 0. I I I I I I I I TEMP.~ TRAVERSE! I - - NO SOFFIT WEIW0 = 3.2 <a> WEIW0 = 3.2 (Cl WEIW0 =2 <e> CORRIDOR -.-1 I I I ~- T 0.35 m I -., I ~ TEMP.& I VELOCITY I TRAVERSE I I ~ ~ !bl WEIW0 = 1/2 !dl WEIW0 = 1/4 (f)
Chapter1The Evolution of Fire ScienceROOMCORRIDOREXITVIEW4Sx2SSTRRT'LAER2MIXINGREGIONNOSOFFITWe/Wo=3.2We/Wo=3.2(b)(a)Figure1-7Smokestreaks showing thecomplexflowpattern in a scalemodel corridorsubjecttoaroomWe/Wo=2We/Wp=1fire,FromQuintiere(c)(d)et al.,Ref.12.sallyadopted this system in itspublications.Tounderstandarticles in firescienceitis essential tobeconversantwiththeSI units.Table1-3liststhe SI units foquantitiesrelevanttoourforthcomingdiscussion,Thequantitieslistedarisefromthecomponentdisciplinesoffireandcannotbedeveloped ingreatdepth,butwewillcometothemAs an example, let us consider energy.Table 1-4 is related to temperature,andintheUnitedStatesweshouldbefamiliarwithBTUunits(BritishThermalUnits)andperhapsW-s (Watt-second)whichisaJoule().Althoughtemperature ismorecommonlyexpressed inFahrenheit (°F),wecanreadilyconvertto otherunitsof temperature as shown inTable1-5.Celsius orCentigrade (°C) is based on water freezingand boiling at0 and 100 respectively,whereas 32and212arerespectivelyassignedon theFahrenheitscale.BoththeCand °F scales do not start their zero base where all thermal energy stops (absolute
Chapter 1 The Evolution of Fire Science Figure 1-7 Smoke streaks showing the complex flow pattern in a scale model corridor subject to a room fire. From Quintiere et al., Ref. 12. I I I <J :r I I I NO SOFFIT WEIW0 = 3.2 <al EXIT VIEW T 0 :r °NE ·., :r I sally adopted this system in its publications. To understand articles in fire science, it is essential to be conversant with the SI units. Table 1-3 lists the SI units for quantities relevant to our forthcoming discussion. The quantities listed arise from the component disciplines of fire and cannot be developed in great depth, but we will come to them. As an example, let us consider energy. Table 1-4 is related to temperature, and in the United States we should be familiar with BTU units (British Thermal Units) and perhaps W-s (Watt-second) which is a Joule (J). Although temperature is more commonly expressed in Fahrenheit (°F), we can readily convert to other units of temperature as shown in Table 1-5. Celsius or Centigrade (°C) is based on water freezing and boiling at O and 100 respectively, whereas 32 and 212 are respectively assigned on the Fahrenheit scale. Both the °C and °F scales do not start their zero base where all thermal energy stops (absolute
Chapter1TheEvolutionofFireScience100(a50OOMMVVV限The shapeof thepropanediffusionflamesasa functionof theheat releaserateQandtheceiling-burnerseparation.20Figure1-8 Flamepatterns of a ceiling10jet.FromKokkala0510and Rinkinen,Ref.13.ENERGYRELEASERATEQ(KW)zero).This is presented in alternative (absolute)scales of Rankinefor°F andKelvinforC.Temperaturesneedtobein"absolute"unitsforcertainformulas.Table1-6gives other conversionfactors thatmaybeuseful.In addition,typ-ically used symbols are assigned to the quantities,These symbols are used in thistext and are fairly common in the fire literature, but are not universal.Note thatthe dot overa symbol implies"rate"or“per unit time",and two accents impliesflux“per unit area."Rate per unit area is commonly called flux.Greek symbols arealsocommon,e.g.p (rho)for densityand α (alpha)forthermal diffusively.Wewill ex-pertains to mass orheatflowratesperplain the significance of these qualities as we encounter them in our study of fire.unitareaFinallyTable1-7 lists terminologyin scientificnotation which avoidsmanyzerosinexpressingnumbers.Forexample,kW(kilowatts)denotes10o0wattsor1o3watts.Similarly10-W is a thousandth ofone watt orone mW (milliwatt)
_ Ch_a_P_te_r_1_Th_e_E_vo_Iut_•_·o_n_of_F_ir_e_sc_ie_nce Figure 1-8 Flame patterns of a ceiling jet. From Kokkala and Rinkinen, Ref. 13. flux pertains to mass or heat flow rates per unit area 100 E 5 50 :t: .µ The shape of the .s::::. Ol propane diffusion ·a:; :r: flames as a function Ol C of the heat release ·a:; rate O and the u ceiling-burner separation. 20 10 0 5 10 ENERGY RELEASE RATE Q(kWl zero). This is presented in alternative (absolute) scales of Rankine for °F and Kelvin for 0 C. Temperatures need to be in "absolute" units for certain formulas. Table 1-6 gives other conversion factors that may be useful. In addition, typically used symbols are assigned to the quantities. These symbols are used in this text and are fairly common in the fire literature, but are not universal. Note that the dot over a symbol implies "rate" or "per unit time", and two accents implies "per unit area." Rate per unit area is commonly called flux. Greek symbols are also common, e.g. p (rho) for density and a (alpha) for thermal diffusively. We will explain the significance of these qualities as we encounter them in our study of fire. Finally Table 1-7 lists terminology in scientific notation which avoids many zeros in expressing numbers. For example, kW (kilowatts) denotes 1000 watts or 103 watts. Similarly 10- 3 Wis a thousandth of one watt or one mW (milliwatt)
119Chapter1The Evolution of Fire ScienceTable1-3SIquantities.QuantityUnit abbreviationForceN (newton)Masskg (kilogram mass)s(second)TimeLengthm (meter)oCorkTemperatureEnergyJ(oule)PowerW(watt)W/m.℃Thermal conductivityW/m2.°℃Heat-transfercoefficientJ/kg-°℃Specific heatW/m2HeatfluxTable 1-4Alternative energyunits.1Btuwill raise1Ibmofwater1Fat68F1calwill raise1gofwater1Cat20°C.1kcalwillraise1kgofwater1°Cat20°C.Some conversion factors for the various units of work and energy are1Btu=778.16lb,-ft1Btu=1055J1kcal=4182J1lb,-ft=1.356J1Btu=252calTable1-5Temperature conversions.FdegreeFahrenheit:T(F)=T(C)(1.8)+32RdegreeRankine:T(R)=T(F)+459.69CdegreeCelsiusorCentigrade:T(C)=(T(F)-32)/1.8oKdegreeKelvin:T(K)=T(C)+273.16
Chapter 1 The Evolution of Fire Science Table 1-3 SI quantities. Quantity Force Mass Time Length Temperature Energy Power Thermal conductivity Heat-transfer coefficient Specific heat Heat flux Unit abbreviation N (newtonl kg (kilogram massl s (secondl m (meterl °C or K J Uoulel W (wattl W/m - °C W/m2 - °C J/kg - °C W/m2 Table 1-4 Alternative energy units. 1 Btu will raise 1 lbm of water 1°F at 68°F. 1 cal will raise 1 g of water 1°c at 20°C. 1 kcal will raise 1 kg of water 1°c at 20°c. Some conversion factors for the various units of work and energy are 1 Btu= 778.16 lb1 -ft 1 Btu= 1055 J 1 kcal= 4182 J 1 lb1 -ft= 1.356 J 1 Btu = 252 cal Table 1-5 Temperature conversions. °F degree Fahrenheit: T(Fl = T(Cl (1.8l + 32 0 R degree Rankine: T(Rl = Tff) + 459.69 0 c degree Celsius or Centigrade: T(C) = (T(F)-321/1.8 °K degree Kelvin: T(Kl = T(Cl + 273.16