外文翻译--回到基本配管工程学概述.doc

BacktoBasics:AnOverviewofPlumbingEngineeringByJohnSwaffieldAnyoverviewmustbepersonal.Inthiscase,theperspectiveisbasedon25yearsofexposuretothewholegamutofplumbingissuesfromapplicationofmathematicalsimulationstotheeffortsnecessarytobringwatersupplytothelessprivilegedareasofdevelopingcountries；fromtheinvestigationofventingproblemsinundergroundstructurestothepoliticalandbusinessissuesinherentinthemannerinwhichcodesandregulationsarespecified.Thisperspectiveleadstocautioninaddressingthetitle“BacktoBasics.”IntheU.K.,andprobablyotherwesterndemocracies,thisphraserepresentsthegraveyardofmanypoliticalaspirations.Thefirststepinthisoverviewthereforeistodefine“basics”andprobablymoreimportantlytodeterminewhatisnotincludedunderthisheading.Thefundamentalrequirementofaplumbingsystem,includingbothwatersupplyanddrainage,isthatitdoesnoharm.Thepublichealthimperativeissupreme.Thisisoftenencapsulatedwithincodesthroughanapparentobsessionwithsuchissuesasback-siphonage.Drainagesystemsmustcarryawaywastewithoutposingahazardtotheuserorprovidinganylongtermhazardwithintheareasthroughwhichthedrainagesystempasses.Habitablespacemustbeprotectedfromtheincursionoffoulodorthroughtheprovisionofventingsystems.Theserequirementsarebasicandform,intheU.K.atleast,thebackboneoftheVictoriandrainageandventsystemsinstalledfromthe1880sandwhichbecametheprecursorofsimilarsystemswithinthedevelopingWesternworldatthattime.IntheU.K.inthemid19thcenturyChadwickandothersocialreformersintroducedmanyoftheurbanwatersupplyanddrainagesystemtechniquesnowtakenforgrantedeffectivelytheIndustrialRevolutionspawnedboththeproblemandthesociallyawaregroupsthatwouldprovideitssolution.Totheserequirementsmustnowalsobeaddedtheneedtoconservewater,notonlyasaneconomicandpoliticalimperative,butalsotomeetthedemandsbeingplacedonwatersupplysystemsbyincreasesinpopulation,particularlyinthecitiesofthedevelopingworld,andtherisingexpectationsofthosefortunatetoliveindevelopedcities.WhatsNotIncludedSomuchforthedefinitionof“basics.”Theconsiderationofwhatshouldnotbeincludedwithinthistitleismorecontroversial.“Backtobasics”doesnotmeanareturntosomegoldenagewhenruleofthumbwassupreme,whenventingwassoexcessivethattrapsneveroscillatedandflushvolumessogreatthatimperfectionsinsystemdesignandinstallationwentunnoticed,andeachcommunityapplieditsowncodesandstandardsdevelopedfromlimitedexperimentationandobservation,unsubstantiatedbyanydegreeofengineeringanalysisorrigor.IntheU.S.thedesignofwatersupplyanddrainagesystemsmaybetracedbacktothefundamentalworkofHunter.However,Hunterrecognizedinhisdefinitive1940paperthatthesolutionsheproposedwerelimitedbytheanalysistechniquesavailabletohim.Referringtothedesignofbuildingdrainagesystemsheobservedthat“.theconventionalpipeformulaeapplytotheirregularandintermittentflowsthatoccurinplumbingsystemsonlyduringthattime(usuallyveryshort)andthatsectionofpipeinwhichthevariablefactorsinvolved(velocityorvolumerateoffloworhydraulicgradientandhydraulicradius)areconstant.”Hunterrecognizedthatthebasicphysicsunderlyingwatersupplyanddrainage,and,inparticular,drainage,asthisarmofthesubjectoffersparticularchallengestotheanalysisduetothefreesurfacenatureoftheflow,whichmayalsobemulti-phaseduetothetransportofsolidmaterialandthepossibilityofentrainedair,isidenticalinSeattleandSydney,HobokenandHelsinkiorevenAlbuquerqueandAuchtermuchty.Yeteachofthestatesornationsrepresentedinthislisthasitsowncodeorstandard.TheEuropeanCommunityhasstruggledfornearly20yearstogenerateacommonplumbingcodeunsuccessfully.Thus,thepredominantissueforplumbingengineeringattheendofthe20thcenturyhastodowitheducationtheneedtostressthatphysicsdefinesoperationandmathematicalsimulationscanfunctionwithoutruleofthumboverrides.WaterConservationWaterconservationoffersanexamplefortheinteractionbetweenpractitionersandthoseinvolvedindevelopingbothproductsandsystemdesignsimulationprocesses.Areviewofthewaterusagewithindevelopedcountriesindicatessurprisingsimilaritiesinthepercentageuseofdomesticwaterforawholerangeofcommonrequirementsapproximately30to40%ofthedrinking-qualitywaterisusedtoflushtoilets.Similarfiguresarefoundintoiletandurinalusageincommercialbuildings.Carefulmonitoringofusagehasprovidedthisdata,andtointroduceeffectivewaterconservationmeasuresitisimperativethatwaterclosetflushvolumesdecrease.Thishasbeenacontinuingthrustforthewholeofthiscentury,acenturywhichopenedwithadisagreementbetweentheLondonMetropolitanWaterBoardandtheceramicindustryoverthe10.5gallonsproposedforwaterclosetflushingandclosedwithargumentsinsimilararenasastotheacceptabilityof1.6gallonsforflushingdevices.Similarly,thecenturyopenedintheU.K.withtheInstituteofHealthinLondonproposingadrainlinecarrytestusinghalf-inchdiameterballsandclosedwithanextremelysimilartestprobablyfacingdemisewithintheU.S.watercloset.Reducingwaterclosetflushvolumeisimperative.Gooddesigncandeliver.Theintroductionofdualflush(i.e.,alowerflushvolumeforurineremoval,particularlysignificantincommercialbuildingswithahighfemalepopulation),offersfurtheropportunitiesforconservation.DualflushwasfirstintroducedtotheU.K.inthe1980s,whereitwasunsuccessfulduetoalackofclarityinoperation.Itwillbereintroducedinthe1999WaterRegulations,encouragedtoalargeextentbythesuccessfuluseof1.6and0.8gallondualflushinAustralia.Theintroductionofnon-siphonicflushingdeviceswithintheU.K.WaterRegulationsfromJanuary1,2001,willallowasimplerandunambiguoustwo-buttonmechanismwhichwillensurethatthesysteminunderstoodbyallusers.DrainageSystemsHowever,thereisaneedtorecognizethatdrainagenetworksareasystem.Alterationtooneelementinisolationmayleadtopossibleproblems.Thereisaneedtorecognizethatreducingflushvolumeshouldbeaccompaniedbypossiblereductionsindrainagediameters,particularlyforisolatedwaterclosetsorincreasesinslope.Similarly,thedecayoftheflushwaveneedstoberecognizedandmodeled.Hunterrecognizedtheimportanceofwaveattenuationbutwasunabletomodelitduetothelackofcomputingpowerinthe1940s.Themodelingmethodtoensurethattheseconsiderationsarefullyinvestigatedatboththecodeanddesignstageexists,developedinitiallythroughinitiativesatNationalBureauofStandards,nowNIST,andpropagatedintheU.S.throughASPEconferencesoverthepast10years.Similarly,waterclosetdesigncan,andwill,benefitfromtheintroductionofmoderntechnology.TheapplicationofcomputationalfluiddynamicstotheflowregimewithinwaterclosetshasalreadybeendemonstratedbysuchindustrialorganizationsasTotoinJapan.WhilethereisaneedtoapproachwithcautiontheboundaryconditionswhichmustdeterminetheaccuracyofanysuchCFDmodel,theintroductionofsuchmodelsisamajorstepforwardinthedevelopmentofwaterclosets.Mathematicalsimulationscaninformthedesignerwhentheitemisacceptable.Mathematicalmodelscanprovidethetargetstowhichdesignshouldaspireorconfirmtheappropriatenessofagivensetofperformancecodecriteria.Thisapproachwouldbringtheplumbingengineeringindustryinitsbroadersenseinlinewiththoseotherindustrieswhichdependonafundamentalunderstandingoffluidmechanics.Thus,thisoverviewofplumbingengineeringstressestheimportanceofwaterconservationandhighlightsitsgrowingimportanceinthecomingcentury.Therewillbeaneedforthedevelopedworldtoreduceitsusageofwaterwhileatthesametimebeingabletoprovidelowwaterusesolutionstothosecountriesstilldevelopingandwhosecitiesareseverelytaxedbytheoveruseofwaterforpurposesthatcouldbeachievedatlowercost.Indefiningthebasicsofdrainagedesign,thepreventionofodoringresswashighlighted.TheVictorianconceptthatsmellequalleddiseaseledtoextremelycomplicatedventingsystems,knownintheU.K.astwo-pipenetworkswhereeachindividualappliancewasseparatelyventedtoaventstackandblackandgreywaterwereseparatelytakenawayfromthebuildingthroughtwoverticalwetstacks.Thedevelopmentinthe1930softheonepipesystemintheU.S.and,inparticular,theintroductionofthesinglestacksystemintheU.K.fromthe1950son,ledtoconsiderablesavingsintermsofthecostofplumbinginstallations.IntheU.K.inthe1950ssuchreductionswereimportantinthepost-warhousingrebuildingprocess.Howeverventingsystemsarestillover-provided.Moderntechnologyallowstheanalysisofventsystemoperationandallowstheidentificationofmeansbywhichpressureexcursionsmaybelimited.Theintroductionofpressurereliefvalvesorairadmittancevalvesandtheopportunityfordistributedventingupthewholeheightofamulti-storybuildingofferstremendousadvantagesandsavingsforventedsystemdesign.IntheU.K.thedevelopmentofwaterlesstrapsealsthatalsoactasairadmittancevalvesprovideexcitingpossibilitiesforsystemdesignersinthefuture.Inthiscontext“backtobasics”doesnotmeanadheringtocomplicatedventsystemswhenmoderntechnologycouldoffersimplerandmoreelegantdesignopportunities.Intheareaofrainwaterdrainage,whichvariesconsiderablyduetogeographiclocation,similaradvantagesmaynowobtainedthroughtheintroductionofsystemsrelyingonafundamentalunderstandingofsystemflow.Siphonicrainwatersystemsappliedtolargebuildings,suchasairportsandretailoutlets,offertremendouscostadvantages,attheexpenseofensuringthatthemechanismsnecessaryarefullyunderstood.Siphonicrainwatersystemsrequirethattherainwaterpipesrunfull,creatingsub-atmosphericpressurestoincreasethedrainageratefromtheroofduringdesignrainstorms.Systemdesignisrelatedtothedesignstormandthesemustbematched.Over-provisioninthedrainagesystemwillleadtounderusageasthedesignstormmaynotoccurforseveralhundredyears.Under-designofthenetworkmayleadtoexcessivesuctionpressuresasthedesignstormmayoccurandbeexceededonmanyoccasions.Thesiphonicnatureofthesystemmeansthatpipeworkisdepressurizedandthereisapossibilityofsystemcollapseunderparticularflowconditionsflowconditionsthatcanbeproperlyanalyzedandpredictedsothatthedangerscanbeminimized.Theseinnovationsemphasizetheneedforplumbingengineerstofullyunderstandthefluidmechanicsoftheirsubjectareaandconfirmthatdesignersandcodespecifiersunderstandthatru