建筑给排水 外文文献翻译1.docx

建筑给排水 外文文献翻译1.docx

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建筑给排水外文文献翻译1

本科毕业设计

外文文献及译文

文献、资料题目：

Sealedbuildingdrainage

andventsystems

文献、资料来源：

国道数据库

文献、资料发表（出版）日期：

2005.9.12

院（部）：

市政与环境工程学院

专业：

给水排水工程

班级：

姓名：

学号：

指导教师：

翻译日期：

2012.06

外文文献：

Sealedbuildingdrainageandventsystems

—anapplicationofactiveairpressuretransientcontrolandsuppression

Abstract

Theintroductionofsealedbuildingdrainageandventsystemsisconsideredaviablepropositionforcomplexbuildingsduetotheuseofactivepressuretransientcontrolandsuppressionintheformofairadmittancevalvesandpositiveairpressureattenuatorscoupledwiththeinterconnectionofthenetwork'sverticalstacks.

Thispaperpresentsasimulationbasedonafour-stacknetworkthatillustratesflowmechanismswithinthepipeworkfollowingbothappliancedischargegenerated,andsewerimposed,transients.Thissimulationidentifiestheroleoftheactiveairpressurecontroldevicesinmaintainingsystempressuresatlevelsthatdonotdepletetrapseals.

Furthersimulationexerciseswouldbenecessarytoprovideproofofconcept,anditwouldbeadvantageoustoparallelthesewithlaboratory,andpossiblysite,trialsforvalidationpurposes.Despitethiscautiontheinitialresultsarehighlyencouragingandaresufficienttoconfirmthepotentialtoprovidedefinitebenefitsintermsofenhancedsystemsecurityaswellasincreasedreliabilityandreducedinstallationandmaterialcosts.

Keywords:

Activecontrol;Trapretention;Transientpropagation

Nomenclature

C+-——characteristicequations

c——wavespeed,m/s

D——branchorstackdiameter,m

f——frictionfactor,UKdefinitionviaDarcyΔh=4fLu2/2Dg

g——accelerationduetogravity,m/s2

K——losscoefficient

L——pipelength,m

p——airpressure,N/m2

t——time,s

u——meanairvelocity,m/s

x——distance,m

γ——ratiospecificheats

Δh——headloss,m

Δp——pressuredifference,N/m2

Δt——timestep,s

Δx——internodallength,m

ρ——density,kg/m3

ArticleOutline

Nomenclature

1.Introduction—airpressuretransientcontrolandsuppression

2.Mathematicalbasisforthesimulationoftransientpropagationinmulti-stackbuildingdrainagenetworks

3.Roleofdiversityinsystemoperation

4.Simulationoftheoperationofamulti-stacksealedbuildingdrainageandventsystem

5.Simulationsignconventions

6.Waterdischargetothenetwork

7.Surchargeatbaseofstack1

8.Sewerimposedtransients

9.Trapsealoscillationandretention

10.Conclusion—viabilityofasealedbuildingdrainageandventsystem

1.Airpressuretransientsgeneratedwithinbuildingdrainageandventsystemsasanaturalconsequenceofsystemoperationmayberesponsiblefortrapsealdepletionandcrosscontaminationofhabitablespace[1].Traditionalmodesoftrapsealprotection,basedontheVictorianengineer'sobsessionwithodourexclusion[2],[3]and[4],dependpredominantlyonpassivesolutionswhererelianceisplacedoncrossconnectionsandverticalstacksventedto

atmosphere[5]and[6].Thisapproach,whilebothprovenandtraditional,hasinherentweaknesses,includingtheremotenessoftheventterminations[7],leadingtodelaysinthearrivalofrelievingreflections,andthemultiplicityofopenrooflevelstackterminationsinherentwithincomplexbuildings.Thecomplexityoftheventsystemrequiredalsohassignificantcostandspaceimplications[8].

Thedevelopmentofairadmittancevalves（AAVs）overthepasttwodecadesprovidesthedesignerwithameansofalleviatingnegativetransientsgeneratedasrandomappliancedischargescontributetothetimedependentwater-flowconditionswithinthesystem.AAVsrepresentanactivecontrolsolutionastheyresponddirectlytothelocalpressureconditions,openingaspressurefallstoallowareliefairinflowandhencelimitthepressureexcursionsexperiencedbytheappliancetrapseal[9].

However,AAVsdonotaddresstheproblemsofpositiveairpressuretransientpropagationwithinbuildingdrainageandventsystemsasaresultofintermittentclosureofthefreeairpaththroughthenetworkorthearrivalofpositivetransientsgeneratedremotelywithinthesewersystem,possiblybysomesurchargeeventdownstream—includingheavyrainfallincombinedsewerapplications.

Thedevelopmentofvariablevolumecontainmentattenuators[10]thataredesignedtoabsorbairflowdrivenbypositiveairpressuretransientscompletesthenecessarydeviceprovisiontoallowactiveairpressuretransientcontrolandsuppressiontobeintroducedintothedesignofbuildingdrainageandventsystems,forboth‘standard’buildingsandthoserequiringparticularattentiontobepaidtothesecurityimplicationsofmultiplerooflevelopenstackterminations.Thepositiveairpressureattenuator（PAPA）consistsofavariablevolumebagthatexpandsundertheinfluenceofapositivetransientandthereforeallowssystemairflowstoattenuategradually,thereforereducingthelevelofpositivetransientsgenerated.

TogetherwiththeuseofAAVstheintroductionofthePAPAdeviceallowsconsiderationofafullysealedbuildingdrainageandventsystem.

Fig.1illustratesbothAAVandPAPAdevices,notethatthewaterlesssheathtrapactsasanAAVundernegativelinepressure.

Fig.1.Activeairpressuretransientsuppressiondevicestocontrolbothpositiveandnegativesurges.

Activeairpressuretransientsuppressionandcontrolthereforeallowsforlocalizedinterventiontoprotecttrapsealsfrombothpositiveandnegativepressureexcursions.Thishasdistinctadvantagesoverthetraditionalpassiveapproach.Thetimedelayinherentinawaitingthereturnofarelievingreflectionfromaventopentoatmosphereisremovedandtheeffectofthetransientonalltheothersystemtrapspassedduringitspropagationisavoided.

2.Mathematicalbasisforthesimulationoftransientpropagationinmulti-stackbuildingdrainagenetworks.

ThepropagationofairpressuretransientswithinbuildingdrainageandventsystemsbelongstoawellunderstoodfamilyofunsteadyflowconditionsdefinedbytheStVenantequationsofcontinuityandmomentum,andsolvableviaafinitedifferenceschemeutilizingthemethodofcharacteristicstechnique.Airpressuretransientgenerationandpropagationwithinthesystemasaresultofairentrainmentbythefallingannularwaterinthesystemverticalstacksandthereflectionandtransmissionofthesetransientsatthesystemboundaries,includingopenterminations,connectionstothesewer,appliancetrapsealsandbothAAVandPAPAactivecontroldevices,maybesimulatedwithprovenaccuracy.Thesimulation[11]provideslocalairpressure,velocityandwavespeedinformationthroughoutanetworkattimeanddistanceintervalsasshortas0.001 sand300 mm.Inaddition,thesimulationreplicateslocalappliancetrapsealoscillationsandtheoperationofactivecontroldevices,therebyyieldingdataonnetworkairflowsandidentifyingsystemfailuresandconsequences.Whilethesimulationhasbeenextensivelyvalidated[10],itsusetoindependentlyconfirmthemechanismofSARSvirusspreadwithintheAmoyGardensoutbreakin2003hasprovidedfurtherconfidenceinitspredictions[12].

Airpressuretransientpropagationdependsupontherateofchangeofthesystemconditions.Increasingannulardownflowgeneratesanenhancedentrainedairflowandlowersthesystempressure.Retardingtheentrainedairflowgeneratespositivetransients.Externaleventsmayalsopropagatebothpositiveandnegativetransientsintothenetwork.

Theannularwaterflowinthe‘wet’stackentrainsanairflowduetotheconditionof‘noslip’establishedbetweentheannularwaterandaircoresurfacesandgeneratestheexpectedpressurevariationdownaverticalstack.Pressurefallsfromatmosphericabovethestackentryduetofrictionandtheeffectsofdrawingairthroughthewatercurtainsformedatdischargingbranchjunctions.Inthelowerwetstackthepressurerecoverstoaboveatmosphericduetothetractionforcesexertedontheairflowpriortofallingacrossthewatercurtainatthestackbase.

Theapplicationofthemethodofcharacteristicstothemodellingofunsteadyflowswasfirstrecognizedinthe1960s[13].TherelationshipsdefinedbyJack[14]allowsthesimulationtomodelthetractionforceexertedontheentrainedair.Extensiveexperimentaldataallowedthedefinitionofa‘pseudo-frictionfactor’applicableinthewetstackandoperableacrossthewaterannularflow/entrainedaircoreinterfacetoallowcombineddischargeflowsandtheireffectonairentrainmenttobemodelled.

ThepropagationofairpressuretransientsinbuildingdrainageandventsystemsisdefinedbytheStVenantequationsofcontinuityandmomentum[9],

（1）

（2）

Thesequasi-linearhyperbolicpartialdifferentialequationsareamenabletofinitedifferencesolutiononcetransformedviatheMethodofCharacteristicsintofinitedifferencerelationships,Eqs.（3）–（6）,thatlinkconditionsatanodeonetimestepinthefuturetocurrentconditionsatadjacentupstreamanddownstreamnodes,Fig.2.

Fig.2.StVenantequationsofcontinuityandmomentumallowairflowvelocityandwavespeedtobepredictedonanx-tgridasshown.Note

.

FortheC+characteristic:

（3）

when

（4）

andtheC-characteristic:

（5）

when

（6）

wherethewavespeedcisgivenby

c=（γp/ρ）0.5.

（7）

Theseequationsinvolvetheairmeanflowvelocity,u,andthelocalwavespeed,c,duetotheinterdependenceofairpressureanddensity.Localpressureiscalculatedas

（8）

Suitableequationslinklocalpressuretoairflowortotheinterfaceoscillationoftrapseals.

Thecaseoftheappliancetrapsealisofparticularimportance.The