1600Lh牛奶单效蒸发器设计（含CAD图纸和说明书）
收藏
资源目录
压缩包内文档预览：
编号：207819986
类型：共享资源
大小：3.85MB
格式：ZIP
上传时间：2022-04-13
上传人：机****料
认证信息
个人认证
高**（实名认证）
河南
IP属地：河南
50
积分
- 关 键 词：
-
1600
Lh
牛奶
蒸发器
设计
CAD
图纸
说明书
- 资源描述：
-
1600Lh牛奶单效蒸发器设计（含CAD图纸和说明书）,1600,Lh,牛奶,蒸发器,设计,CAD,图纸,说明书
- 内容简介：
-
AirConditioningSystemsAirconditioninghasrapidlygrownoverthepast50years,fromaluxurytoastandardsystemincludedinmostresidentialandcommercialbuildings.In1970,36%ofresidencesintheU.S.wereeitherfullyairconditionedorutilizedaroomairconditionerforcooling(Blue,etal.,1979).By1997,thisnumberhadmorethandoubledto77%,andthatyearalsomarkedthefirsttimethatoverhalf(50.9%)ofresidencesintheU.S.hadcentralairconditioners(CensusBureau,1999).Anestimated83%ofallnewhomesconstructedin1998hadcentralairconditioners(CensusBureau,1999).Airconditioninghasalsogrownrapidlyincommercialbuildings.From1970to1995,thepercentageofcommercialbuildingswithairconditioningincreasedfrom54to73%(JacksonandJohnson,1978,andDOE,1998).Airconditioninginbuildingsisusuallyaccomplishedwiththeuseofmechanicalorheat-activatedequipment.Inmostapplications,theairconditionermustprovidebothcoolinganddehumidificationtomaintaincomfortinthebuilding.Airconditioningsystemsarealsousedinotherapplications,suchasautomobiles,trucks,aircraft,ships,andindustrialfacilities.However,thedescriptionofequipmentinthischapterislimitedtothosecommonlyusedincommercialandresidentialbuildings.Commercialbuildingsrangefromlargehigh-riseofficebuildingstothecornerconveniencestore.Becauseoftherangeinsizeandtypesofbuildingsinthecommercialsector,thereisawidevarietyofequipmentappliedinthesebuildings.Forlargerbuildings,theairconditioningequipmentispartofatotalsystemdesignthatincludesitemssuchasapipingsystem,airdistributionsystem,andcoolingtower.Properdesignofthesesystemsrequiresaqualifiedengineer.Theresidentialbuildingsectorisdominatedbysinglefamilyhomesandlow-riseapartments/condominiums.Thecoolingequipmentappliedinthesebuildingscomesinstandard“packages”thatareoftenbothsizedandinstalledbytheairconditioningcontractor.Thechapterstartswithageneraldiscussionofthevaporcompressionrefrigerationcyclethenmovestorefrigerantsandtheirselection,followedbypackagedChilledWaterSystems。1.1VaporCompressionCycleEventhoughthereisalargerangeinsizesandvarietyofairconditioningsystemsusedinbuildings,mostsystemsutilizethevaporcompressioncycletoproducethedesiredcoolinganddehumidification.Thiscycleisalsousedforrefrigeratingandfreezingfoodsandforautomotiveairconditioning.ThefirstpatentonamechanicallydrivenrefrigerationsystemwasissuedtoJacobPerkinsin1834inLondon,andthefirstviablecommercialsystemwasproducedin1857byJamesHarrisonandD.E.Siebe.Besidesvaporcompression,therearetwolesscommonmethodsusedtoproducecoolinginbuildings:theabsorptioncycleandevaporativecooling.Thesearedescribedlaterinthechapter.Withthevaporcompressioncycle,aworkingfluid,whichiscalledtherefrigerant,evaporatesandcondensesatsuitablepressuresforpracticalequipmentdesigns.Thefourbasiccomponentsineveryvaporcompressionrefrigerationsystemarethecompressor,condenser,expansiondevice,andevaporator.Thecompressorraisesthepressureoftherefrigerantvaporsothattherefrigerantsaturationtemperatureisslightlyabovethetemperatureofthecoolingmediumusedinthecondenser.Thetypeofcompressoruseddependsontheapplicationofthesystem.Largeelectricchillerstypicallyuseacentrifugalcompressorwhilesmallresidentialequipmentusesareciprocatingorscrollcompressor.Thecondenserisaheatexchangerusedtorejectheatfromtherefrigeranttoacoolingmedium.Therefrigerantentersthecondenserandusuallyleavesasasubcooledliquid.Typicalcoolingmediumsusedincondensersareairandwater.Mostresidential-sizedequipmentusesairasthecoolingmediuminthecondenser,whilemanylargerchillersusewater.Afterleavingthecondenser,theliquidrefrigerantexpandstoalowerpressureintheexpansionvalve.Theexpansionvalvecanbeapassivedevice,suchasacapillarytubeorshorttubeorifice,oranactivedevice,suchasathermalexpansionvalveorelectronicexpansionvalve.Thepurposeofthevalveistoregulatetheflowofrefrigeranttotheevaporatorsothattherefrigerantissuperheatedwhenitreachesthesuctionofthecompressor.Attheexitoftheexpansionvalve,therefrigerantisatatemperaturebelowthatofthemedium(airorwater)tobecooled.Therefrigeranttravelsthroughaheatexchangercalledtheevaporator.Itabsorbsenergyfromtheairorwatercirculatedthroughtheevaporator.Ifairiscirculatedthroughtheevaporator,thesystemiscalledadirectexpansionsystem.Ifwateriscirculatedthroughtheevaporator,itiscalledachiller.Ineithercase,therefrigerantdoesnotmakedirectcontactwiththeairorwaterintheevaporator.Therefrigerantisconvertedfromalowquality,two-phasefluidtoasuperheatedvaporundernormaloperatingconditionsintheevaporator.Thevaporformedmustberemovedbythecompressoratasufficientratetomaintainthelowpressureintheevaporatorandkeepthecycleoperating.Allmechanicalcoolingresultsintheproductionofheatenergythatmustberejectedthroughthecondenser.Inmanyinstances,thisheatenergyisrejectedtotheenvironmentdirectlytotheairinthecondenserorindirectlytowaterwhereitisrejectedinacoolingtower.Withsomeapplications,itispossibletoutilizethiswasteheatenergytoprovidesimultaneousheatingtothebuilding.Recoveryofthiswasteheatattemperaturesupto65C(150F)canbeusedtoreducecostsforspaceheating.Capacitiesofairconditioningareoftenexpressedineithertonsorkilowatts(kW)ofcooling.Thetonisaunitofmeasurerelatedtotheabilityofaniceplanttofreezeoneshortton(907kg)oficein24hr.Itsvalueis3.51kW(12,000Btu/hr).ThekWofthermalcoolingcapacityproducedbytheairconditionermustnotbeconfusedwiththeamountofelectricalpower(alsoexpressedinkW)requiredtoproducethecoolingeffect.2.1RefrigerantsUseandSelectionUpuntilthemid-1980s,refrigerantselectionwasnotanissueinmostbuildingairconditioningapplicationsbecausetherewerenoregulationsontheuseofrefrigerants.Manyoftherefrigerantshistoricallyusedforbuildingairconditioningapplicationshavebeenchlorofluorocarbons(CFCs)andhydrochlorofluorocarbons(HCFCs).Mostoftheserefrigerantsarenontoxicandnonflammable.However,recentU.S.federalregulations(EPA1993a;EPA1993b)andinternationalagreements(UNEP,1987)haveplacedrestrictionsontheproductionanduseofCFCsandHCFCs.Hydrofluorocarbons(HFCs)arenowbeingusedinsomeapplicationswhereCFCsandHCFCswereused.Havinganunderstandingofrefrigerantscanhelpabuildingownerorengineermakeamoreinformeddecisionaboutthebestchoiceofrefrigerantsforspecificapplications.Thissectiondiscussesthedifferentrefrigerantsusedinorproposedforbuildingairconditioningapplicationsandtheregulationsaffectingtheiruse.TheAmericanSocietyofHeating,RefrigeratingandAirConditioningEngineers(ASHRAE)hasastandardnumberingsystem,foridentifyingrefrigerants(ASHRAE,1992).ManypopularCFC,HCFC,andHFCrefrigerantsareinthemethaneandethaneseriesofrefrigerants.Theyarecalledhalocarbons,orhalogenatedhydrocarbons,becauseofthepresenceofhalogenelementssuchasfluorineorchlorine(King,1986).Zeotropesandazeotropesaremixturesoftwoormoredifferentrefrigerants.Azeotropicmixturechangessaturationtemperaturesasitevaporates(orcondenses)atconstantpressure.Thephenomenaiscalledtemperatureglide.Atatmosphericpressure,R-407Chasaboiling(bubble)pointof44C(47F)andacondensation(dew)pointof37C(35F),whichgivesitatemperatureglideof7C(12F).Anazeotropicmixturebehaveslikeasinglecomponentrefrigerantinthatthesaturationtemperaturedoesnotchangeappreciablyasitevaporatesorcondensesatconstantpressure.R-410Ahasasmallenoughtemperatureglide(lessthan5.5C,10F)thatitisconsideredanear-azeotropicrefrigerantmixture.ASHRAEgroupsrefrigerantsbytheirtoxicityandflammability(ASHRAE,1994).GroupA1isnonflammableandleasttoxic,whileGroupB3isflammableandmosttoxic.Toxicityisbasedontheuppersafetylimitforairborneexposuretotherefrigerant.Iftherefrigerantisnontoxicinquantitieslessthan400partspermillion,itisaClassArefrigerant.Ifexposuretolessthan400partspermillionistoxic,thenthesubstanceisgiventheBdesignation.Thenumericaldesignationsrefertotheflammabilityoftherefrigerant.ThelastcolumnofTable4.2.1showsthetoxicityandflammabilityratingofcommonrefrigerants.Refrigerant22isanHCFC,isusedinmanyofthesameapplications,andisstilltherefrigerantofchoiceinmanyreciprocatingandscrewchillersaswellassmallcommercialandresidentialpackagedequipment.ItoperatesatamuchhigherpressurethaneitherR-11orR-12.RestrictionsontheproductionofHCFCswillstartin2004.In2010,R-22cannotbeusedinnewairconditioningequipment.R-22cannotbeproducedafter2020(EPA,1993b). R-407CandR-410AarebothmixturesofHFCs.BothareconsideredreplacementsforR-22.R-407Cisexpectedtobeadrop-inreplacementrefrigerantforR-22.ItsevaporatingandcondensingpressuresforairconditioningapplicationsareclosetothoseofR-22(Table4.2.3).However,replacementofR-22withR-407Cshouldbedoneonlyafterconsultingwiththeequipmentmanufacturer.Ataminimum,thelubricantandexpansiondevicewillneedtobereplaced.Thefirstresidential-sizedairconditioningequipmentusingR-410AwasintroducedintheU.S.in1998.SystemsusingR-410Aoperateatapproximately50%higherpressurethanR-22(Table4.2.3);thus,R-410Acannotbeusedasadrop-inrefrigerantforR-22.R-410Asystemsutilizecompressors,expansionvalves,andheatexchangersdesignedspecificallyforusewiththatrefrigerant.Ammoniaiswidelyusedinindustrialrefrigerationapplicationsandinammoniawaterabsorptionchillers.ItismoderatelyflammableandhasaclassBtoxicityratingbuthashadlimitedapplicationsincommercialbuildingsunlessthechillerplantcanbeisolatedfromthebuildingbeingcooled(Toth,1994,Stoecker,1994).Asarefrigerant,ammoniahasmanydesirablequalities.Ithasahighspecificheatandhighthermalconductivity.Itsenthalpyofvaporizationistypically6to8timeshigherthanthatofthecommonlyusedhalocarbons,anditprovideshigherheattransfercomparedtohalocarbons.Itcanbeusedinbothreciprocatingandcentrifugalcompressors.Researchisunderwaytoinvestigatetheuseofnaturalrefrigerants,suchascarbondioxide(R-744)andhydrocarbonsinairconditioningandrefrigerationsystems(Bullock,1997,andKramer,1991).CarbondioxideoperatesatmuchhigherpressuresthanconventionalHCFCsorHFCsandrequiresoperationabovethecriticalpointintypicalairconditioningapplications.Hydrocarbonrefrigerants,oftenthoughtofastoohazardousbecauseofflammability,canbeusedinconventionalcompressorsandhavebeenusedinindustrialapplications.R-290,propane,hasoperatingpressuresclosetoR-22andhasbeenproposedasareplacementforR-22(Kramer,1991).Currently,therearenocommercialsystemssoldintheU.S.forbuildingoperationsthatuseeithercarbondioxideorflammablerefrigerants. 3.1ChilledWaterSystemsChilledwatersystemswereusedinlessthan4%ofcommercialbuildingsintheU.S.in1995.However,becausechillersareusuallyinstalledinlargerbuildings,chillerscooledover28%oftheU.S.commercialbuildingfloorspacethatsameyear(DOE,1998).Fivetypesofchillersarecommonlyappliedtocommercialbuildings:reciprocating,screw,scroll,centrifugal,andabsorption.Thefirstfourutilizethevaporcompressioncycletoproducechilledwater.Theydifferprimarilyinthetypeofcompressorused.Absorptionchillersutilizethermalenergy(typicallysteamorcombustionsource)inanabsorptioncyclewitheitheranammonia-waterorwater-lithiumbromidesolutiontoproducechilledwater.3.2OverallSystemAnestimated86%ofchillersareappliedinmultiplechillerarrangementslikethatshowninthefigure(BitondoandTozzi,1999).Inchilledwatersystems,returnwaterfromthebuildingiscirculatedthrougheachchillerevaporatorwhereitiscooledtoanacceptabletemperature(typically4to7C)(39to45F).Thechilledwateristhendistributedtowater-to-airheatexchangersspreadthroughoutthefacility.Intheseheatexchangers,airiscooledanddehumidifiedbythecoldwater.Duringtheprocess,thechilledwaterincreasesintemperatureandmustbereturnedtothechiller(s).Thechillersarewater-cooledchillers.Wateriscirculatedthroughthecondenserofeachchillerwhereitabsorbsheatenergyrejectedfromthehighpressurerefrigerant.Thewateristhenpumpedtoacoolingtowerwherethewateriscooledthroughanevaporationprocess.Coolingtowersaredescribedinalatersection.Chillerscanalsobeaircooled.Inthisconfiguration,thecondenserwouldbearefrigerant-to-airheatexchangerwithairabsorbingtheheatenergyrejectedbythehighpressurerefrigerant.Chillersnominallyrangeincapacitiesfrom30to18,000kW(8to5100ton).MostchillerssoldintheU.S.areelectricandutilizevaporcompressionrefrigerationtoproducechilledwater.Compressorsforthesesystemsareeitherreciprocating,screw,scroll,orcentrifugalindesign.Asmallnumberofcentrifugalchillersaresoldthatuseeitheraninternalcombustionengineorsteamdriveinsteadofanelectricmotortodrive thecompressor.Thetypeofchillerusedinabuildingdependsontheapplication.Forlargeofficebuildingsorinchillerplantsservingmultiplebuildings,centrifugalcompressorsareoftenused.Inapplicationsunder1000kW(280tons)coolingcapacities,reciprocatingorscrewchillersmaybemoreappropriate.Insmallerapplications,below100kW(30tons),reciprocatingorscrollchillersaretypicallyused.3.3ScrewCompressorsScrewcompressors,firstintroducedin1958(Thevenot,1979),arepositivedisplacement compressors.Theyareavailableinthecapacityrangesthatoverlapwithreciprocatingcompressorsandsmallcentrifugalcompressors.Bothtwin-screwandsingle-screwcompressorsareusedinchillers.Thetwin-screwcompressorisalsocalledthehelicalrotarycompressor.Acutawayofatwin-screwcompressordesign.Therearetwomainrotors(screws).Oneisdesignatedmaleandtheotherfemale.Thecompressionprocessisaccomplishedbyreducingthevolumeoftherefrigerantwiththerotarymotionofscrews.Atthelowpressuresideofthecompressor,avoidiscreatedwhentherotorsbegintounmesh.Lowpressuregasisdrawnintothevoidbetweentherotors.Astherotorscontinuetoturn,thegasisprogressivelycompressedasitmovestowardthedischargeport.Oncereachingapredeterminedvolumeratio,thedischargeportisuncoveredandthegasisdischargedintothehighpressuresideofthesystem.Atarotationspeedof3600rpm,ascrewcompressorhasover14,000dischargesperminute(ASHRAE,1996).Fixedsuctionanddischargeportsareusedwithscrewcompressorsinsteadofvalves,asusedinreciprocatingcompressors.Thesesetthebuilt-involumeratiotheratioofthevolumeoffluidspaceinthemeshingrotorsatthebeginningofthecompressionprocesstothevolumeintherotorsasthedischargeportisfirstexposed.Associatedwiththebuilt-involumeratioisapressureratiothatdependsonthepropertiesoftherefrigerantbeingcompressed.Screwcompressorshavethecapabilitytooperateatpressureratiosofabove20:1(ASHRAE,1996).Peakefficiencyisobtainedifthedischargepressureimposedbythe
- 温馨提示:
1: 本站所有资源如无特殊说明，都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
2: 本站的文档不包含任何第三方提供的附件图纸等，如果需要附件，请联系上传者。文件的所有权益归上传用户所有。
3.本站RAR压缩包中若带图纸，网页内容里面会有图纸预览，若没有图纸预览就没有图纸。
4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
5. 人人文库网仅提供信息存储空间，仅对用户上传内容的表现方式做保护处理，对用户上传分享的文档内容本身不做任何修改或编辑，并不能对任何下载内容负责。
6. 下载文件中如有侵权或不适当内容，请与我们联系，我们立即纠正。
7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
人人文库网所有资源均是用户自行上传分享，仅供网友学习交流，未经上传用户书面授权，请勿作他用。
川公网安备: 51019002004831号