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1600 Lh 牛奶 蒸发器 设计 CAD 图纸 说明书

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本科毕业设计（论文）任务书题目：1600Lh牛奶单效蒸发器设计学生姓名 届 学院 机械工程学院 专业 指导教师 职称 下达任务日期 年 月 日 一、毕业设计（论文）内容及要求1.设计内容：本设计主要是根据板式蒸发器的特点，总结之前设计过的人的经验，设计出新型的板式蒸发器，已达到牛奶浓缩的目的。 由于乳液为热敏性物料，所以蒸发过程中温度不能太高，在蒸发设备中乳液的停留时间也不能太长。为了满足这个要求，真空降膜蒸发设备经常被用来进行乳液的浓缩。多效降膜蒸发设备有很多优点，由于溶液在单程蒸发器中属于膜状流动，因而对流传热系数提高，使得溶液在加热室一次通过不在循环就能达到要求的浓度，因此比循环型蒸发器更有优点。溶液在蒸发器中停留时间很短，所以适用于如乳液等热敏性物料的蒸发。由于采用高压喷雾瞬间蒸发，使奶在不破坏有效营养成分下得到浓缩，提高了产品的物质含量。一定要：单效板式蒸发器研究步骤：(1)牛奶的生产工艺流程，蒸发系统流程的选取1)牛奶的生产工艺流程的确定2)蒸发器的选型3)蒸发器流程的选取4)蒸发器操作流程图的确定(2)工艺计算1)原始数据处理2)蒸发系统的物料衡算和热量衡算3)蒸发器传热面积计算4)蒸发器强度和效率的计算5)临界热负荷的校和6)管路的计算7)附属设备的设计和选型(3)结构设计与强度计算1)加热元件的结构设计2)布液装置的结构设计3)蒸发器各部件的强度计算4)气液分离器的设计与计算5)杀菌器、预热器的设计计算与选型6)法兰的选取7)其他零件的选取 2.设计要求： (1)外文翻译(2)填写设计任务书 (3)撰写毕业设计开题报告 (4)进行相关计算后绘制工艺流程图、零件图和装配图 (5)编写设计说明书二、毕业设计（论文）进度计划及检查情况记录表序号起止日期计划完成内容实际完成内容检查日期检查人签名12014.10.312015.3.12熟悉课题，收集资料，检索相关设计内容22015.03.122015.04.2毕业实习，英文翻译32015.04.32015.04.20方案设计（确定方案），完成设计必要的计算42015.04.212015.05.15详细的零件设计，论文的初步拟稿52015.05.162015.05.25结构设计，零件设计，工程图的绘制62015.05.262015.06.10整理设计资料，撰写论文，总结分析过程和结果72015.06.112015.06.15准备毕业答辩资料89注：（1）表中“实际完成内容”、“检查人签名”栏目要求用笔填写，其余各项均要求打印。 （2）毕业设计（论文）任务书一式二份，一份学院留存，一份发给学生，任务完成后装订在毕业设计说明书（毕业论文）内。3 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.Screwcompressorshavethecapabi