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BacktoBasicsAnOverviewofPlumbingEngineeringByJohnSwaffieldAnyoverviewmustbepersonal.Inthiscase,theperspectiveisbasedon25yearsofexposuretothewholegamutofplumbingissuesfromapplicationofmathematicalsimulationstotheeffortsnecessarytobringwatersupplytothelessprivilegedareasofdevelopingcountriesfromtheinvestigationofventingproblemsinundergroundstructurestothepoliticalandbusinessissuesinherentinthemannerinwhichcodesandregulationsarespecified.ThisperspectiveleadstocautioninaddressingthetitleBacktoBasics.IntheU.K.,andprobablyotherwesterndemocracies,thisphraserepresentsthegraveyardofmanypoliticalaspirations.Thefirststepinthisoverviewthereforeistodefinebasicsandprobablymoreimportantlytodeterminewhatisnotincludedunderthisheading.Thefundamentalrequirementofaplumbingsystem,includingbothwatersupplyanddrainage,isthatitdoesnoharm.Thepublichealthimperativeissupreme.Thisisoftenencapsulatedwithincodesthroughanapparentobsessionwithsuchissuesasbacksiphonage.Drainagesystemsmustcarryawaywastewithoutposingahazardtotheuserorprovidinganylongtermhazardwithintheareasthroughwhichthedrainagesystempasses.Habitablespacemustbeprotectedfromtheincursionoffoulodorthroughtheprovisionofventingsystems.Theserequirementsarebasicandform,intheU.K.atleast,thebackboneoftheVictoriandrainageandventsystemsinstalledfromthe1880sandwhichbecametheprecursorofsimilarsystemswithinthedevelopingWesternworldatthattime.IntheU.K.inthemid19thcenturyChadwickandothersocialreformersintroducedmanyoftheurbanwatersupplyanddrainagesystemtechniquesnowtakenforgranted––effectivelytheIndustrialRevolutionspawnedboththeproblemandthesociallyawaregroupsthatwouldprovideitssolution.Totheserequirementsmustnowalsobeaddedtheneedtoconservewater,notonlyasaneconomicandpoliticalimperative,butalsotomeetthedemandsbeingplacedonwatersupplysystemsbyincreasesinpopulation,particularlyinthecitiesofthedevelopingworld,andtherisingexpectationsofthosefortunatetoliveindevelopedcities.WhatsNotIncludedSomuchforthedefinitionofbasics.Theconsiderationofwhatshouldnotbeincludedwithinthistitleismorecontroversial.Backtobasicsdoesnotmeanareturntosomegoldenagewhenruleofthumbwassupreme,whenventingwassoexcessivethattrapsneveroscillatedandflushvolumessogreatthatimperfectionsinsystemdesignandinstallationwentunnoticed,andeachcommunityapplieditsowncodesandstandardsdevelopedfromlimitedexperimentationandobservation,unsubstantiatedbyanydegreeofengineeringanalysisorrigor.IntheU.S.thedesignofwatersupplyanddrainagesystemsmaybetracedbacktothefundamentalworkofHunter.However,Hunterrecognizedinhisdefinitive1940paperthatthesolutionsheproposedwerelimitedbytheanalysistechniquesavailabletohim.Referringtothedesignofbuildingdrainagesystemsheobservedthat...theconventionalpipeformulaeapplytotheirregularandintermittentflowsthatoccurinplumbingsystemsonlyduringthattimeusuallyveryshortandthatsectionofpipeinwhichthevariablefactorsinvolvedvelocityorvolumerateoffloworhydraulicgradientandhydraulicradiusareconstant.Hunterrecognizedthatthebasicphysicsunderlyingwatersupplyanddrainage,and,inparticular,drainage,asthisarmofthesubjectoffersparticularchallengestotheanalysisduetothefreesurfacenatureoftheflow,whichmayalsobemultiphaseduetothetransportofsolidmaterialandthepossibilityofentrainedair,isidenticalinSeattleandSydney,HobokenandHelsinkiorevenAlbuquerqueandAuchtermuchty.Yeteachofthestatesornationsrepresentedinthislisthasitsowncodeorstandard.TheEuropeanCommunityhasstruggledfornearly20yearstogenerateacommonplumbingcode––unsuccessfully.Thus,thepredominantissueforplumbingengineeringattheendofthe20thcenturyhastodowitheducation––theneedtostressthatphysicsdefinesoperationandmathematicalsimulationscanfunctionwithoutruleofthumboverrides.WaterConservationWaterconservationoffersanexamplefortheinteractionbetweenpractitionersandthoseinvolvedindevelopingbothproductsandsystemdesignsimulationprocesses.Areviewofthewaterusagewithindevelopedcountriesindicatessurprisingsimilaritiesinthepercentageuseofdomesticwaterforawholerangeofcommonrequirements––approximately30to40ofthedrinkingqualitywaterisusedtoflushtoilets.Similarfiguresarefoundintoiletandurinalusageincommercialbuildings.Carefulmonitoringofusagehasprovidedthisdata,andtointroduceeffectivewaterconservationmeasuresitisimperativethatwaterclosetflushvolumesdecrease.Thishasbeenacontinuingthrustforthewholeofthiscentury,acenturywhichopenedwithadisagreementbetweentheLondonMetropolitanWaterBoardandtheceramicindustryoverthe10.5gallonsproposedforwaterclosetflushingandclosedwithargumentsinsimilararenasastotheacceptabilityof1.6gallonsforflushingdevices.Similarly,thecenturyopenedintheU.K.withtheInstituteofHealthinLondonproposingadrainlinecarrytestusinghalfinchdiameterballsandclosedwithanextremelysimilartestprobablyfacingdemisewithintheU.S.watercloset.Reducingwaterclosetflushvolumeisimperative.Gooddesigncandeliver.Theintroductionofdualflushi.e.,alowerflushvolumeforurineremoval,particularlysignificantincommercialbuildingswithahighfemalepopulation,offersfurtheropportunitiesforconservation.DualflushwasfirstintroducedtotheU.K.inthe1980s,whereitwasunsuccessfulduetoalackofclarityinoperation.Itwillbereintroducedinthe1999WaterRegulations,encouragedtoalargeextentbythesuccessfuluseof1.6and0.8gallondualflushinAustralia.TheintroductionofnonsiphonicflushingdeviceswithintheU.K.WaterRegulationsfromJanuary1,2001,willallowasimplerandunambiguoustwobuttonmechanismwhichwillensurethatthesysteminunderstoodbyallusers.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.astwopipenetworkswhereeachindividualappliancewasseparatelyventedtoaventstackandblackandgreywaterwereseparatelytakenawayfromthebuildingthroughtwoverticalwetstacks.Thedevelopmentinthe1930softheonepipesystemintheU.S.and,inparticular,theintroductionofthesinglestacksystemintheU.K.fromthe1950son,ledtoconsiderablesavingsintermsofthecostofplumbinginstallations.IntheU.K.inthe1950ssuchreductionswereimportantinthepostwarhousingrebuildingprocess.Howeverventingsystemsarestilloverprovided.Moderntechnologyallowstheanalysisofventsystemoperationandallowstheidentificationofmeansbywhichpressureexcursionsmaybelimited.Theintroductionofpressurereliefvalvesorairadmittancevalvesandtheopportunityfordistributedventingupthewholeheightofamultistorybuildingofferstremendousadvantagesandsavingsforventedsystemdesign.IntheU.K.thedevelopmentofwaterlesstrapsealsthatalsoactasairadmittancevalvesprovideexcitingpossibilitiesforsystemdesignersinthefuture.Inthiscontextbacktobasicsdoesnotmeanadheringtocomplicatedventsystemswhenmoderntechnologycouldoffersimplerandmoreelegantdesignopportunities.Intheareaofrainwaterdrainage,whichvariesconsiderablyduetogeographiclocation,similaradvantagesmaynowobtainedthroughtheintroductionofsystemsrelyingonafundamentalunderstandingofsystemflow.Siphonicrainwatersystemsappliedtolargebuildings,suchasairportsandretailoutlets,offertremendouscostadvantages,attheexpenseofensuringthatthemechanismsnecessaryarefullyunderstood.Siphonicrainwatersystemsrequirethattherainwaterpipesrunfull,creatingsubatmosphericpressurestoincreasethedrainageratefromtheroofduringdesignrainstorms.Systemdesignisrelatedtothedesignstormandthesemustbematched.Overprovisioninthedrainagesystemwillleadtounderusageasthedesignstormmaynotoccurforseveralhundredyears.Underdesignofthenetworkmayleadtoexcessivesuctionpressuresasthedesignstormmayoccurandbeexceededonmanyoccasions.Thesiphonicnatureofthesystemmeansthatpipeworkisdepressurizedandthereisapossibilityofsystemcollapseunderparticularflowconditions––flowconditionsthatcanbeproperlyanalyzedandpredictedsothatthedangerscanbeminimized.Theseinnovationsemphasizetheneedforplumbingengineerstofullyunderstandthefluidmechanicsoftheirsubjectareaandconfirmthatdesignersandcodespecifiersunderstandthatruleofthumbsafetyfactorsmay,indrainagesystems,leadtofailure,ratherthansafety.WaterReuseWaterconservationmaybeviewedasasourceofnewsupply.Oneofthemosthopefulareasfordevelopmentisinthereuseofwastewaterorthecollection,orharvesting,ofrainwater.IntheU.K.thisisanareabeinggivenconsiderableattention.However,therearelegislativeareastobeaddressedconcerningthequalityofthecollectedwater.Whilerainwaterharvestingmaybeanattractivesolutioninsomeareas,asdemonstratedattheAWWAConserv99conference,waterqualitymustbesuitableandtheremustbenopossibilityofcrosscontaminationbetweenthecontributingwatersources,e.g.,waterclosetflushingwhererainwaterandreusedbathorsinkwatercouldbecollectedtogetherinoneholdingtankalsoprovidedwithamainstopupsupply.Theremayhavetobetreatmentifwaterresideswithinthesystemlongerthantheminimumperiodoftime.Developmentsinonlinecontrol,sensorsandtariffstructureswillallowthebenefitsofwaterreusetoberealized.RecurringIssuesAnumberofrecurringissuesareidentifiedbythisoverview.First,theneedtofullyunderstandthefluidmechanicsofplumbingsystemoperationwillrequireashiftin
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