Vacuum ejector - Wikipedia

In an ejector, a working fluid (liquid or gaseous) flows through a jet nozzle into a tube that first narrows and then expands in cross-sectional area. Vacuumejector FromWikipedia,thefreeencyclopedia Jumptonavigation Jumptosearch Typeofejector-jetpump Forotheruses,seeAspirator(disambiguation). AspiratorAbrassaspirator.Thewaterinletandoutletareatthetopandbottom,respectively;theairinletisontheside.OthernamesEductor-jetpump,injector/ejector,filterpump,VenturipumpUsesVacuumgeneration,suctionRelateditemsInjector,vacuumpump Avacuumejector,orsimplyejectorisatypeofvacuumpump,whichproducesvacuumbymeansoftheVenturieffect. Inanejector,aworkingfluid(liquidorgaseous)flowsthroughajetnozzleintoatubethatfirstnarrowsandthenexpandsincross-sectionalarea.ThefluidleavingthejetisflowingatahighvelocitywhichduetoBernoulli'sprincipleresultsinithavinglowpressure,thusgeneratingavacuum.Theoutertubethennarrowsintoamixingsectionwherethehighvelocityworkingfluidmixeswiththefluidthatisdrawninbythevacuum,impartingenoughvelocityforittobeejected,thetubethentypicallyexpandsinordertodecreasethevelocityoftheejectedstream,allowingthepressuretosmoothlyincreasetotheexternalpressure. Thestrengthofthevacuumproduceddependsonthevelocityandshapeofthefluidjetandtheshapeoftheconstrictionandmixingsections,butifaliquidisusedastheworkingfluidthestrengthofthevacuumproducedislimitedbythevaporpressureoftheliquid(forwater,3.2 kPaor0.46 psior32mbarat25 °Cor77 °F).Ifagasisused,however,thisrestrictiondoesnotexist. Ifnotconsideringthesourceoftheworkingfluid,vacuumejectorscanbesignificantlymorecompactthanaself-poweredvacuumpumpofthesamecapacity. Contents 1Commontypes 1.1Wateraspirator 1.2Steamejector 1.3Airejector 2Seealso 3References Commontypes[edit] Wateraspirator[edit] Thecheapandsimplewateraspiratoriscommonlyusedinchemistryandbiologylaboratoriesandconsistsofateefittingattachedtoatapandhasahosebarbatoneside.Theflowofwaterpassesthroughthestraightportionofthetee,whichhasarestrictionattheintersection,wherethehosebarbisattached.Thevacuumhoseshouldbeconnectedtothisbarb.Inthepast,wateraspiratorswerecommonforlow-strengthvacuumsinchemistrybenchwork.However,theyarewater-intensive,anddependingonwhatthevacuumisbeingusedfor(e.g.solventremoval),theycanviolateenvironmentalprotectionlawssuchastheRCRAbymixingpotentiallyhazardouschemicalsintothewaterstream,thenflushingthemdownadrainthatoftenleadsdirectlytothemunicipalsewer.Theirusehasdecreasedsomewhatassmallelectricvacuumpumpsarefarmoreeffective,environmentallysafe,andhavebecomemoreaffordable,buttheunmatchedsimplicityandreliabilityofthisdevicehavecausedittoremainpopularforsmalllabsorasabackup. Another,muchlargerversionofthisdeviceisusedinmaritimeoperationsasadevicetodewater(drain)areasinashipthathavebeenfloodedinemergencysituations.Typicallyreferredtoasaneductorintheseapplications,thisispreferredoverelectricalpumpsduetotheirsimplicity,compactsize,andgreatlymitigatedriskofexplosionintheeventthatflammableliquidsand/orvaporsarepresent.Additionally,unlikemanymechanicalpumps,theycanalsopassdebrisastheeductorhasnomovingpartsthatcanbefouled.Thismakesaneductorespeciallyusefulinsituationswherefittingadebrisstrainertothesuctionportwillpresentmoreissuesthanitresolves.Thesizeofthedebristhatcanbepasseddependsonthephysicalsizeoftheeductor.Sizes,flowratings,andapplicationsvary,includingeductorsthatarepermanentlyinstalled(typicallyusedinverylargespaces,suchasaship'smainengineroom),orportablemodelsthatcanbeloweredintospacesbyaropeandsuppliedanddrainedthroughfirefightinghoses.Mostaresuppliedthroughaship'sfirefightingmain,andportablemodelscanalsobesuppliedbyanemergencypump,provideditcansupplysufficientflowtooperatetheeductor. Steamejector[edit] Theindustrialsteamejector(alsocalledthe"steamjetejector","steamaspirator",or"evactor")usessteamasaworkingfluidandmultistagesystemscanproduceveryhighvacuums.Duetothelackofdelicatemovingpartsandtheflowofsteamprovidingsomewhatofcleaningaction,steamejectorscanhandlegasflowscontainingliquids,dust,orevensolidparticlesthatwoulddamageorclogmanyothervacuumpumps.EjectorsmadeentirelyfromspecialisedmaterialssuchasPTFEorgraphitehaveallowedusageofextremelycorrosivegasses,sincesteamejectorshavenomovingpartstheycanbeconstructedintheirentiretyfromalmostanymaterialthathassufficientdurability. Inordertoavoidusingtoomuchsteamorimpracticaloperatingpressures,asinglesteam-ejectorstageisgenerallynotusedtogeneratevacuumbelowapproximately10kPa(75mmHg).[1]Togeneratehighervacuum,multiplestagesareused;inatwo-stagesteamejector,forexample,thesecondstageprovidesvacuumforthewastesteamoutputbythefirststage.Condensersaretypicallyusedbetweenstagestosignificantlyreducetheloadonthelaterstages.Steamejectorswithtwo,three,four,fiveandsixstagesmaybeusedtoproducevacuumsdownto2.5kPa,300Pa,40Pa,4Pa,and0.4Pa,respectively.[1] Steamejectorsarealsosuitableforpumpingmanyliquidssinceifthesteamcanbeeasilycondensedintotheliquidthenthereisnoneedtoseparatetheworkingfluidormanageamistofliquiddroplets.Thisisthemannerinwhichasteaminjectoroperates. Anadditionalusefortheinjectortechnologyisinvacuumejectorsincontinuoustrainbrakingsystems,whichweremadecompulsoryintheUKbytheRegulationofRailwaysAct1889.Avacuumejectorusessteampressuretodrawairoutofthevacuumpipeandreservoirsofcontinuoustrainbrake.Steamlocomotives,withareadysourceofsteam,foundejectortechnologyidealwithitsruggedsimplicityandlackofmovingparts.Asteamlocomotiveusuallyhastwoejectors:alargeejectorforreleasingthebrakeswhenstationaryandasmallejectorformaintainingthevacuumagainstleaks.Theexhaustfromtheejectorsisinvariablydirectedtothesmokebox,bywhichmeansitassiststheblowerindraughtingthefire.Thesmallejectorissometimesreplacedbyareciprocatingpumpdrivenfromthecrossheadbecausethisismoreeconomicalofsteamandisonlyrequiredtooperatewhenthetrainismoving. Airejector[edit] Commonlycalledanairejector,Venturipump,orvacuumejector.Thisejectorissimilarinoperationtothesteamejectorbutuseshigh-pressureairastheworkingfluid.Multistageairejectorscanbeused,butsinceaircannoteasilybecondensedatroomtemperature,anairejectorisusuallylimitedtotwostagesaseachsubsequentstagewouldhavetobesignificantlylargerthanthelast.Thesearecommonlyusedinpneumatichandlingequipmentwhenasmallvacuumisrequiredtopickupobjectssincecompressedairisoftenalreadypresenttopowerotherpartsoftheequipment.Airejectorsusedtosuctionliquidsdirectlywillproduceafinemistofdroplets,thisishowairbrushesandmanyothersprayingsystemsoperate,butwhenasprayisnotrequireditistypicallyanundesirableeffectthatlimitstheapplicationstogassuction. Thebasicelementsofanejector Seealso[edit] Diffusionpump Injector Vacuumpump Watereductor References[edit] ^abHighVacuumPumpingEquipment,B.D.Power,NewYork:ReinholdPublishingCorporation,1966,chapter4. vteLaboratoryequipmentGeneralHeatersDryers Alcoholburner Bunsenburner Desiccator Heatingmantle Hotplate Laboven Kiln Meker–Fisherburner Striker Tecluburner Waterbath Vacuumdrybox MixersShakers Chemostat Homogenizer Liquidwhistle Magneticstirrer Mortarandpestle Shaker Sonicator Staticmixer Stirringrod Vortexmixer Washbottle StandsClampsHolders Beakerclamp Clampholder Tripod Buretteclamp Extensionclamp Flaskclamp Funnelsupport Ironring Pinchclamp Retortstand Screwclamp Testtubeholder Testtuberack Wiregauze Labdryingrack ContainersStorage Agarplate Cryogenicstoragedewar Incubator Laminarflowcabinet Microtiterplate Petridish Picotiterplate Refrigerator Weighingboat Weighingdish Otheritems Aspirator Autoclave Balancebrush Corkborer Crucible Filterpaper File Forceps Centrifuge Microscope Pipeclaytriangle Spectrophotometer Splint Stopper Scoopula Spatula Testtubebrush Wirebrush Inoculationneedle Inoculationloop GlasswareApparatus Dean–Stark Soxhletextractor Kipp's Bottles Bostonround Condensers Coldfinger Liebig Dishes Evaporating Petri Syracuse Watchglass Flasks Büchner Vacuum(Dewar) Erlenmeyer Fernbach Fleaker Florence Retort Round-bottom Schlenk Volumetric Funnels Büchner Hirsch Dropping Separatory Measuringdevices Burette Conicalmeasure Cuvette Eyedropper Eudiometer Graduatedcylinder Ostwaldviscometer Pipette Tubes Drying Cragie Nuclearmagneticresonance(NMR) Test Thiele Thistle Otheritems Beaker Belljar Gassyringe Vial AnalyticalchemistryCompositional AutoAnalyzer CHNanalyzer Colorimeter Inductivelycoupledplasma(ICP)device Gaschromatograph(GC) LiquidChromatograph(LC) Massspectrometer(MS) pHindicator pHmeter Microscopy Scanningelectronmicroscope(SEM) Transmissionelectronmicroscope(TEM) Thermochemistry Calorimeter differentialscanning Melting-pointapparatus Thermometer Thermogravimetricanalyzer(TGA) Otheritems Analyticalbalance Colonycounter Spiralplater Nuclearmagneticresonance(NMR)instrument Platereader ElectronicsControldevices Benchpowersupply Currentsource Voltagesource Functiongenerator Galvanostat Pulsegenerator Potentiostat Measurement Ammeter Logicanalyzer Multimeter Networkanalyzer Oscilloscope Spectrumanalyzer Time-domainreflectometer Transistortester Voltmeter Tools Heatgun Solderingiron Tweezers Wirestripper General Alligatorclip Testprobe SafetyPersonalprotectiveequipment(PPE) Labcoat Faceshield Respirator Rubberapron Safetyshower Eyeandhand Acid-resistantgloves Eyewashstation Glovebox Medicalgloves Nitrilegloves Safetyglasses Safetygoggles Otheritems Acid(solvent)cabinet Biosafetycabinet Fireblanket Fireextinguisher Fumehood Instrumentsusedinmedicallaboratories Retrievedfrom"https://en.wikipedia.org/w/index.php?title=Vacuum_ejector&oldid=1091117741" Categories:LaboratoryequipmentVacuumpumpsHiddencategories:ArticleswithshortdescriptionShortdescriptionmatchesWikidata Navigationmenu Personaltools NotloggedinTalkContributionsCreateaccountLogin Namespaces ArticleTalk English Views ReadEditViewhistory More Search Navigation MainpageContentsCurrenteventsRandomarticleAboutWikipediaContactusDonate Contribute HelpLearntoeditCommunityportalRecentchangesUploadfile Tools WhatlinkshereRelatedchangesUploadfileSpecialpagesPermanentlinkPageinformationCitethispageWikidataitem Print/export DownloadasPDFPrintableversion Inotherprojects WikimediaCommons Languages العربيةБългарскиCatalàDeutschEspañolفارسیFrançaisHrvatskiIdoBahasaIndonesiaҚазақшаNederlands日本語NorskbokmålPolskiPortuguêsРусскийSimpleEnglishСрпски/srpskiSrpskohrvatski/српскохрватскиSvenskaTürkçeУкраїнська中文 Editlinks