enclosure-fire-dynamics-c01

1©2000byCRCPressLLCIntroductionThischapterbeginswithabriefdescriptionofthestateoffiresafetyengineeringdesignandexplainsthecontextinwhichthistextbookwaswritten.Itdiscussesthecorecurriculumoffiresafetyengineeringandplacesthematerialpresentedinthebookintocontextwithothertopicswithinthefiresafetyengineeringdiscipline.Enclosurefiremodelscurrentlyusedinfiresafetyengineeringdesignarebrieflydiscussed.Finally,anoverviewofthecontentsofthebookispresentedandgeneralnotationsareexplained.CONTENTS1.1Background1.2CoreCurriculuminFireSafetyEngineering1.3EngineeringModelsforEnclosureFires1.3.1EnergyEvolvedandSpeciesGenerated1.3.2Fire-InducedEnvironment1.3.3HeatTransfer1.4ContentsofThisTextbook1.5ANoteonDimensions,Units,andSymbolsReferences1.1BACKGROUNDFiresafetyregulationscanhaveamajorimpactonmanyaspectsoftheoveralldesignofabuilding,includinglayout,aesthetics,function,andcost.Rapiddevelopmentsinmodernbuildingtechnologyinthelastdecadesoftenhaveresultedinunconventionalstructuresanddesignsolutions.Thephysicalsizeofbuildingsincreasescontinually;thereisatendencytobuildlargeundergroundcarparks,warehouses,andshoppingcomplexes.Theinteriordesignofmanybuildings—withlargelightshafts,patios,andcoveredatriumswithinbuildingsconnectedtohorizontalcorridorsormalls—introducesnewriskfactorsconcerningspreadofsmokeandfire.Pastexperiencesorhistoricalprecedents(whichformthebasisofcurrentprescriptivebuildingcodesandregulations)rarelyprovidetheguidancenecessarytodealwithfirehazardsinneworunusualbuildings.Atthesametimetherehavebeengreatstridesintheunderstandingoffireprocessesandtheirinterrelationshipwithhumansandbuildings.Advancementhasbeenparticularlyrapidintheareaofanalyticalfiremodeling.Severaldifferenttypesofsuchmodels,withvaryingdegreesofsophis-tication,havebeendevelopedinrecentyearsandareusedbyengineersinthedesignprocess.Asaresult,wehaveaworldwidemovementtoreplaceprescriptivebuildingcodeswithonesbasedonperformance.Insteadofprescribingexactlywhichprotectivemeasuresarerequired(suchasprescribinganumberofexitsforevacuationpurposes),theperformanceoftheoverallsystemispresentedagainstaspecifiedsetofdesignobjectives(suchasstatingthatsatisfactoryescapeshouldbeeffectedintheeventoffire).Firemodelingandevacuationmodelingcanoftenbeusedtoassesstheeffectivenessoftheprotectivemeasuresproposed.Theneedtotakeadvantageofthenewemergingtechnology,bothwithregardtodesignandregulatorypurposes,isobvious.Theincreasedcomplexityofthetechnologicalsolutions,however,©2000byCRCPressLLCrequireshigherlevelsofacademictrainingforfireprotectionengineersandahigherlevelofcontinuingeducationduringtheircareers.Someexcellenttextbooks,handbooks,anddesignguideshavebeenproducedforthispurpose,includingAnIntroductiontoFireDynamicsbyDrysdale,1TheSFPEHandbookofFireProtectionEngineering,2andDesignofSmokeControlSystemsbyKloteandMilke,3tonameonlyafew.ApartfromthebookbyDrysdaleandtheonebyShieldsandSilcock,4textbooksonfiresafetyengineeringspecificallywrittenforengineeringstudentshavebeenscarce.Designguidesandhandbooksgenerallylistengineeringproblemsandprovidemethodologiesbywhichtheseproblemscanbesolvedusingspecificcalculationalprocedures.Theequationsusedareseldomderivedfromfirstprinciples,andlittleinformationisgivenontheassumptionsmadeorthevalidityoftheapproach.Tofullyunderstandtheeffecttheseassumptionsmayhaveinaspecificdesignsituationandtobeconfidentofthevalidityofthechosencalculationalprocedure,theengineeratsomepointmusthavederivedtheequationsfromfirstprinciples.Thepurposeofthistextbookisnottoactasadesignguideoralistofequationsthatcanbeappliedtospecificscenarios,butrathertoshowhowengineeringequationsforcertainapplicationscanbearrivedatfromfirstprinciples,tostatetheassumptionsclearly,andtoshowhowtheresultinganalyticalequationscomparetoexperimentaldata.Inthiswaythereaderwillgetastrongfeelingforvalidityandapplicabilityofawiderangeofcommonlyusedengineeringequationsandmodels.Thistextbookspecificallyexaminesenclosurefiredynamics,thestudyofhowtheoutbreakofafireinacompartmentcauseschangesintheenvironmentoftheenclosure.Beforeintroducingthecontentsofthebookweshalldiscussthefiresafetyengineeringcorecurriculum.InSection1.4webrieflydiscussengineeringmodelscurrentlyusedforcalculatingtheenvironmentalconse-quencesofafireinanenclosure.Finally,wediscusssomesymbolsandunits.1.2CORECURRICULUMINFIRESAFETYENGINEERINGThefieldoffiresafetyengineeringencompassestopicsfromawiderangeofengineeringdisciplinesaswellasmaterialofuniqueinteresttofiresafetyengineering.Itisnotimmediatelyobviouswhichofthesetopicsofinterestshouldbeaddressedinatextbookforstudents.Whenidentifyingthesubjectareaofthecurrenttextbooktheauthorsweregreatlyassistedbythepublication“AProposalforaModelCurriculuminFireSafetyEngineering,”byMagnussonetal.5,whichidentifiesthecontentsofthebackground,fundamental,andappliedcoursesthatmaybetaughtwithinthedisciplineoffiresafetyengineering.Thefundamentalcoursesaredividedintofivemodules:•Firefundamentals•Enclosurefiredynamics•Activefireprotection•Passivefireprotection•InteractionbetweenfireandpeopleThistextbookdealsmainlywiththesecondmodule,enclosurefiredynamics