文献翻译配管工程学概述Word下载.docx

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AnOverviewofPlumbingEngineering

ByJohnSwaffield

Anyoverviewmustbepersonal.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.inthemid19thcenturyChadwickandothersocialreformersintroducedmanyoftheurbanwatersupplyanddrainagesystemtechniquesnowtakenforgranted––effectivelytheIndustrialRevolutionspawnedboththeproblemandthesociallyawaregroupsthatwouldprovideitssolution.Totheserequirementsmustnowalsobeaddedtheneedtoconservewater,notonlyasaneconomicandpoliticalimperative,butalsotomeetthedemandsbeingplacedonwatersupplysystemsbyincreasesinpopulation,particularlyinthecitiesofthedevelopingworld,andtherisingexpectationsofthosefortunatetoliveindevelopedcities.

What’sNotIncluded

Somuchforthedefinitionof“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.TheEuropeanCommunityhasstruggledfornearly20yearstogenerateacommonplumbingcode––unsuccessfully.

Thus,thepredominantissueforplumbingengineeringattheendofthe20thcenturyhastodowitheducation––theneedtostressthatphysicsdefinesoperationandmathematicalsimulationscanfunctionwithoutruleofthumboverrides.

WaterConservation

Waterconservationoffersanexamplefortheinteractionbetweenpractitionersandthoseinvolvedindevelopingbothproductsandsystemdesignsimulationprocesses.Areviewofthewaterusagewithindevelopedcountriesindicatessurprisingsimilaritiesinthepercentageuseofdomesticwaterforawholerangeofcommonrequirements––approximately30to40%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.

DrainageSystems

However,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”doesnotmeanadheringtocomp