制冷机组的工作原理与选型（冷水机组系统）毕业论文外文翻译

1、外文文献theworkingprincipleofrefrigerationunitsandselection（chilledwatersystems）received:jamesb.bradfordetal.“hvacequipmentandsystems”.handbookofheating,ventilation,andair-conditioning.ed.janf.kreider.bocaraton,crcpressllc.2001.abstract:inthespaceoftheair-conditioning,refrigerationunitisnecessaryequipme

2、nt.refrigerationunitisthecoolingsystemofsomeoftheequipmentorallequipmentsupportinggroupassembledtogether,asawhole.thiscompactunit,theuseofflexible,easymanagement,installationsimple,someofwhichunitsimplyconnecttotheuseofwaterandpowerforrefrigerationandair-conditioningengineeringdesignandconstruction,

3、hesaid.thispaperdescribesthecoldwater-coolingunits,itisthecompressor,condenser,evaporator,cutexpenditure,controlcomponentsandauxiliaryequipment,suchasassemblyasawhole,andspecificallyfortheair-conditionedterminalorotherworksofthecoldtemperature（hot）water,accordingtotheenvironment,andspacerequirements

4、,andmaketheappropriatechoiceofthechiller.keywords:chiller,steamcompressionrefrigerator,reciprocatingcompressors,screw-typecompressors.chilledwatersystemswereusedinlessthan4%ofcommercialbuildingsintheu.s.in1995.however,becausechillersareusuallyinstalledinlargerbuildings,chillerscooledover28%oftheu.s.

5、commercialbuildingfloorspacethatsameyear（doe,1998）.fivetypesofchillersarecommonlyappliedtocommercialbuildings:reciprocating,screw,scroll,centrifugal,andabsorption.thefirstfourutilizethevaporcompressioncycletoproducechilledwater.theydifferprimarilyinthetypeofcompressorused.absorptionchillersutilizeth

6、ermalenergy（typicallysteamorcombustionsource）inanabsorptioncyclewitheitheranammonia-waterorwater-lithiumbromidesolutiontoproducechilledwater.overallsystemanestimated86%ofchillersareappliedinmultiplechillerarrangementslikethatshowninthefigure（bitondoandtozzi,1999）.inchilledwatersystems,returnwaterfro

7、mthebuildingiscirculatedthrougheachchillerevaporatorwhereitiscooledtoanacceptabletemperature（typically4to7c）（39to45f）.thechilledwateristhendistributedtowater-to-airheatexchangersspreadthroughoutthefacility.intheseheatexchangers,airiscooledanddehumidifiedbythecoldwater.duringtheprocess,thechilledwate

8、rincreasesintemperatureandmustbereturnedtothechiller（s）.incoldwaterintheunit,wateriscirculatedthroughthecondenserofeachchillerwhereitabsorbsheatenergyrejectedfromthehighpressurerefrigerant.thewateristhenpumpedtoacoolingtowerwherethewateriscooledthroughanevaporationprocess.coolingtowersaredescribedin

9、alatersection.chillerscanalsobeaircooled.inthisconfiguration,thecondenserwouldbearefrigerant-to-airheatexchangerwithairabsorbingtheheatenergyrejectedbythehighpressurerefrigerant.chillersnominallyrangeincapacitiesfrom30to18,000kw（8to5100ton）.mostchillerssoldintheu.s.areelectricandutilizevaporcompress

10、ionrefrigerationtoproducechilledwater.compressorsforthesesystemsareeitherreciprocating,screw,scroll,orcentrifugalindesign.asmallnumberofcentrifugalchillersaresoldthatuseeitheraninternalcombustionengineorsteamdriveinsteadofanelectricmotortodrivethecompressor.refrigeratorsystemplansandancillaryequipme

11、ntfigure4.2.2adualchillerapplicationwithmajorauxiliarysystems（courtesyofcarriercorporation）.thetypeofchillerusedinabuildingdependsontheapplication.forlargeofficebuildingsorinchillerplantsservingmultiplebuildings,centrifugalcompressorsareoftenused.inapplicationsunder1000kw（280tons）coolingcapacities,r

12、eciprocatingorscrewchillersmaybemoreappropriate.insmallerapplications,below100kw（30tons）,reciprocatingorscrollchillersaretypicallyused.vaporcompressionchillerstable4.2.5showsthenominalcapacityrangesforthefourtypesofelectricallydrivenvaporcompressionchillers.eachchillerderivesitsnamefromthetypeofcomp

13、ressorusedinthechiller.thesystemsrangeincapacitiesfromthesmallestscroll（30kw;8tons）tothelargestcentrifugal（18,000kw;5000tons）.chillerscanutilizeeitheranhcfc（r-22andr-123）orhfc（r-134a）refrigerant.thesteadystateefficiencyofchillersisoftenstatedasaratioofthepowerinput（inkw）tothechillingcapacity（intons）

14、.acapacityratingofonetonisequalto3.52kwor12,000btu/h.withthismeasureofefficiency,thesmallernumberisbetter.asseenintable4.2.5,centrifugalchillersarethemostefficient;whereas,reciprocatingchillershavetheworstefficiencyofthefourtypes.theefficiencynumbersprovidedinthetablearethesteadystatefull-loadeffici

15、encydeterminedinaccordancetoashraestandard30（ashrae,1995）.theseefficiencynumbersdonotincludetheauxiliaryequipment,suchaspumpsandcoolingtowerfansthatcanaddfrom0.06to0.31kw/tontothenumbersshown（smitetal.,1996）.chillersrunatpartloadcapacitymostofthetime.onlyduringthehighestthermalloadsinthebuildingwill

16、achilleroperatenearitsratedcapacity.asaconsequence,itisimportanttoknowhowtheefficiencyofthechillervarieswithpartloadcapacity.figure4.2.3showsarepresentativedatafortheefficiency（inkw/ton）asafunctionofpercentagefullloadcapacityforareciprocating,screw,andscrollchillerplusacentrifugalchillerwithinletvan

17、econtrolandonewithvariablefrequencydrive（vfd）forthecompressor.thereciprocatingchillerincreasesinefficiencyasitoperatesatasmallerpercentageoffullload.incontrast,theefficiencyofacentrifugalwithinletvanecontrolisrelativelyconstantuntiltheloadfallstoabout60%ofitsratedcapacityanditskw/tonincreasestoalmos

18、ttwiceitsfullyloadedvalue.figure4.2.3chillerefficiencyasafunctionofpercentageoffullloadcapacity.in1998,theairconditioningandrefrigerationinstitute（ari）developedanewstandardthatincorporatesintotheirratingspartloadperformanceofchillers（ari1998c）.partloadefficiencyisexpressedbyasinglenumbercalledtheint

19、egratedpartloadvalue（iplv）.theiplvtakesdatasimilartothatinfigure4.2.3andweightsitatthe25%,50%,75%,and100%loadstoproduceasingleintegratedefficiencynumber.theweightingfactorsattheseloadsare0.12,0.45,0.42,and0.01,respectively.theequationtodetermineiplvis:mostoftheiplvisdeterminedbytheefficiencyatthe50%

20、and75%partloadvalues.manufacturerswillprovide,onrequest,iplvsaswellaspartloadefficienciessuchasthoseshowninfigure4.2.3.figure4.2.4volume-pressurerelationshipsforareciprocatingcompressor.thefourcompressorsusedinvaporcompressionchillersareeachbrieflydescribedbelow.whilecentrifugalandscrewcompressorsar

21、eprimarilyusedinchillerapplications,reciprocatingandscrollcompressorsarealsousedinsmallerunitarypackagedairconditionersandheatpumps.reciprocatingcompressorsthereciprocatingcompressorisapositivedisplacementcompressor.ontheintakestrokeofthepiston,afixedamountofgasispulledintothecylinder.onthecompressi

22、onstroke,thegasiscompresseduntilthedischargevalveopens.thequantityofgascompressedoneachstrokeisequaltothedisplacementofthecylinder.compressorsusedinchillershavemultiplecylinders,dependingonthecapacityofthecompressor.reciprocatingcompressorsuserefrigerantswithlowspecificvolumesandrelativelyhighpressu

23、res.mostreciprocatingchillersusedinbuildingapplicationscurrentlyemployr-22.modernhigh-speedreciprocatingcompressorsaregenerallylimitedtoapressureratioofapproximatelynine.thereciprocatingcompressorisbasicallyaconstant-volumevariable-headmachine.ithandlesvariousdischargepressureswithrelativelysmallcha

24、ngesininlet-volumeflowrateasshownbytheheavyline（labeled16cylinders）infigure4.2.4.condenseroperationinmanychillersisrelatedtoambientconditions,forexample,throughcoolingtowers,sothatoncoolerdaysthecondenserpressurecanbereduced.whentheairconditioningloadislowered,lessrefrigerantcirculationisrequired.th

25、eresultingloadcharacteristicisrepresentedbythesolidlinethatrunsfromtheupperrighttolowerleftoffigure4.2.4.thecompressormustbecapableofmatchingthepressureandflowrequirementsimposedbythesystem.thereciprocatingcompressormatchestheimposeddischargepressureatanyleveluptoitslimitingpressureratio.varyingcapa

26、cityrequirementscanbemetbyprovidingdevicesthatunloadindividualormultiplecylinders.thisunloadingisaccomplishedbyblockingthesuctionordischargevalvesthatopeneithermanuallyorautomatically.capacitycanalsobecontrolledthroughtheuseofvariablespeedormulti-speedmotors.whencapacitycontrolisimplementedonacompre

27、ssor,otherfactorsatpart-loadconditionsneedtoconsidered,suchas（a）effectoncompressorvibrationandsoundwhenunloadersareused,（b）theneedforgoodoilreturnbecauseoflowerrefrigerantvelocities,and（c）properfunctioningofexpansiondevicesatthelowercapacities.withmostreciprocatingcompressors,oilispumpedintotherefri

28、gerationsystemfromthecompressorduringnormaloperation.systemsmustbedesignedcarefullytoreturnoiltothecompressorcrankcasetoprovideforcontinuouslubricationandalsotoavoidcontaminatingheat-exchangersurfaces.reciprocatingcompressorsusuallyarearrangedtostartunloadedsothatnormaltorquemotorsareadequateforstar

29、ting.whengasenginesareusedforreciprocatingcompressordrives,carefulmatchingofthetorquerequirementsofthecompressorandenginemustbeconsidered.screwcompressorsfigure4.2.5illustrationofatwin-screwcompressordesign（courtesyofcarriercorporation）.screwcompressors,firstintroducedin1958（thevenot,1979）,arepositi

30、vedisplacementcompressors.theyareavailableinthecapacityrangesthatoverlapwithreciprocatingcompressorsandsmallcentrifugalcompressors.bothtwin-screwandsingle-screwcompressorsareusedinchillers.thetwin-screwcompressorisalsocalledthehelicalrotarycompressor.figure4.2.5showsacutawayofatwin-screwcompressorde

31、sign.therearetwomainrotors（screws）.oneisdesignatedmale（4inthefigure）andtheotherfemale（6inthefigure）.thecompressionprocessisaccomplishedbyreducingthevolumeoftherefrigerantwiththerotarymotionofscrews.atthelowpressuresideofthecompressor,avoidiscreatedwhentherotorsbegintounmesh.lowpressuregasisdrawninto

32、thevoidbetweentherotors.astherotorscontinuetoturn,thegasisprogressivelycompressedasitmovestowardthedischargeport.oncereachingapredeterminedvolumeratio,thedischargeportisuncoveredandthegasisdischargedintothehighpressuresideofthesystem.atarotationspeedof3600rpm,ascrewcompressorhasover14,000dischargesp

33、erminute（ashrae,1996）.fixedsuctionanddischargeportsareusedwithscrewcompressorsinsteadofvalves,asusedinreciprocatingcompressors.thesesetthebuilt-involumeratiotheratioofthevolumeoffluidspaceinthemeshingrotorsatthebeginningofthecompressionprocesstothevolumeintherotorsasthedischargeportisfirstexposed.as

34、sociatedwiththebuilt-involumeratioisapressureratiothatdependsonthepropertiesoftherefrigerantbeingcompressed.screwcompressorshavethecapabilitytooperateatpressureratiosofabove20:1（ashrae,1996）.peakefficiencyisobtainedifthedischargepressureimposedbythesystemmatchesthepressuredevelopedbytherotorswhenthe

35、dischargeportisexposed.iftheinterlobepressureinthescrewsisgreaterorlessthandischargepressure,energylossesoccurbutnoharmisdonetothecompressor.capacitymodulationisaccomplishedbyslidevalvesthatprovideavariablesuctionbypassordelayedsuctionportclosing,reducingthevolumeofrefrigerantcompressed.continuously

36、variablecapacitycontrolismostcommon,butsteppedcapacitycontrolisofferedinsomemanufacturersmachines.variabledischargeportingisavailableonsomemachinestoallowcontrolofthebuilt-involumeratioduringoperation.oilisusedinscrewcompressorstosealtheextensiveclearancespacesbetweentherotors,tocoolthemachines,topr

37、ovidelubrication,andtoserveashydraulicfluidforthecapacitycontrols.anoilseparatorisrequiredforthecompressordischargeflowtoremovetheoilfromthehigh-pressurerefrigerantsothatperformanceofsystemheatexchangerswillnotbepenalizedandtheoilcanbereturnedforreinjectioninthecompressor.screwcompressorscanbedirect

38、drivenattwo-polemotorspeeds（50or60hz）.theirrotarymotionmakesthesemachinessmoothrunningandquiet.reliabilityishighwhenthemachinesareappliedproperly.screwcompressorsarecompactsotheycanbechangedoutreadilyforreplacementormaintenance.theefficiencyofthebestscrewcompressorsmatchesorexceedsthatofthebestrecip

39、rocatingcompressorsatfullload.highisentropicandvolumetricefficienciescanbeachievedwithscrewcompressorsbecausetherearenosuctionordischargevalvesandsmallclearancevolumes.screwcompressorsforbuildingapplicationsgenerallyuseeitherr-134aorr-22.references:1“hvacequipmentandsystems”.handbookofheating,ventil

40、ation,andair-conditioning.ed.janf.kreider.bocaraton,crcpressllc.2001.2ashrae.ashraehandbookfundamentals.americansocietyofheating,refrigeratingandair-conditioningengineersinc.;1997.3casciama.digitalcontrollerforacoolingandheatingplanthavingnear-optimalglobalsetpointcontrolstrategy.uspatents5963458,19

41、99.4sheltonsv,joycect.coolingtoweroptimizationforcentrifugalchillers.ashraej1991;33（6）:2836.5kreiderjf,rabla.heatingandcoolingofbuildingsdesignandefficiency.mcgraw-hill,inc.;1994.6huangw,lamhn.usinggeneticalgorithmstooptimizecontrollerparametersforhvacsystems.energybuildings1997;26:27782.7chowtt,zha

42、ngqg,linz,songcl.globaloptimizationofabsorptionchillersystembygeneticalgorithmandneuralnetwork.energybuildings2002;34:1039.8averyg.controllingchillersinvariableflowsystems.ashraej1998;40（2）:425.9hartmant.designissuesofvariablechilled-waterflowthroughchillers.ashraetrans1996;102（2）:67983.10j.mccormic

43、k,progressonthedevelopmentofminiatureturbomachinesforlowcapacityreversebraytoncryocooler,in:proc.9thint.cryocoolerconf.,1996,255267.11l.chen,c.wu,f.sun,finite-timethermodynamicperformanceofanisentropicclosedregeneratedbraytonrefrigerationcycle,int.j.energy,environment,economics4（4）（1997）261274.12s.h

44、ou,h.zhang,anaxial-flowairvaporcompressionrefrigeratingsystemforairconditioningcooledbycirculatingwater,ashraetransactions110（2）（2004）125129.译文制冷机组的工作原理与选型（冷水机组系统）出自：jamesb，bradford等人，暖通空调的设备和系统m，启联资源中心新闻llc公司，2001年摘要：在大空间的空气调节中，制冷机组是必须的设备。制冷机组就是将制冷系统中的部分设备或全部设备配套组组装在一起，成为一个整体。这种机组结构紧凑、使用灵活、管理方便、安装简

45、单，其中有些机组只需连接水源和电源即可使用，为制冷空调工程设计和施工提供了便利条件。本文介绍的是冷水型制冷机组，它是将压缩机、冷凝器、蒸发器、节流机构、辅助设备以及自动控制元件等组装成一个整体，专门为空调末端或其他工艺工程提供不同温度的冷（热）水，根据环境和空间要求，进行相应的冷水机组选择。关键词：冷水机组，蒸汽压缩式制冷机，往复式压缩机，螺杆式压缩机。冷水机组1995年，在美国，冷水机组应用在至少4的商用建筑中。而且，由于制冷机组通常安装在较大的建筑中，在同一年里，制冷机组冷却了多于28的商用建筑的地板空间（doe，1998）。在商用建筑中普遍采用五种型式的制冷机：往复式、螺杆式、旋涡式、离

46、心式和吸收式。前四种利用蒸汽压缩式循环来制得冷冻水。它们的不同主要在于使用的压缩机种类的不同。吸收式制冷机在吸收循环中利用热能（典型的是来自蒸汽或燃料燃烧）并利用氨水或水锂溴化物制得冷冻水。总的系统制冷机系统图及辅助设备大约86的制冷机和表所示的一样用在多台制冷机系统中（bitondo和tozzi，1999）。在冷冻水系统中，建筑物的回水通过每个蒸发器循环流动，在蒸发器中，回水被冷却到合意的温度（典型的为47）（3945）。然后，冷冻水通过各设备传送到水空气换热器。在换热器中，空气被冷冻水冷却和加湿。在这个过程中，冷水的温度升高，然后必须回送到蒸发器中。在冷水机组中，水通过每个机组的冷凝器循环

47、，在冷凝器中，水吸收了来自高压制冷剂的热量。接着，水用水泵打到冷却塔中，水通过蒸发而降温。冷却塔将在后一部分讲述。冷凝器也可以是空冷式的。在这种循环中，冷凝器应是制冷剂空气热交换器，空气吸收来自高压制冷剂的热量。制冷机组名义制冷量为3018000kw（85100tons）。在美国，出售的大部分制冷机组是用电的，利用蒸汽压缩制冷循环来制得冷冻水。在设计中，这种系统所使用的压缩机也有往复式、螺杆式、旋涡式和离心式。一小部分的离心式制冷机利用内燃机或蒸汽机代替电来启动压缩机。在建筑中所使用的制冷机组类型根据应用场所来确定。对于大的办公室建筑或制冷机组需服务于多个建筑时，通常使用离心式压缩机。在所需制

48、冷量小于1000kw（280tons）时，使用往复式或螺杆式制冷机组较合适。在小的应用场合，若低于100kw（30tons）时，使用往复式或旋涡式制冷机组。蒸汽压缩式制冷机图4.2.3制冷机在各种不同满负荷百分数时的效率表4.2.5表示了四种电启动的蒸汽压缩式制冷机组的名义制冷量范围。每种制冷机以所使用的压缩机类型来命名。各种系统的制冷能力范围从最小的旋涡式（30kw，8tons）到最大的离心式（18000kw，5000tons）。制冷机可使用hcfcs（r22，r123）或hfcs（r134a）制冷剂。制冷机的效率通常用输入功（用kw表示）与制冷量（用tons表示）的比值表示。1tons的制

49、冷量等于3.52kw或1200btuh。用这种方法衡量效率，其数值越小越好。从表4.2.5可以看出，离心式制冷机的效率最高。而往复式是这四种类型中效率最低的。表中所提供的效率是根据ashraestandard30（ashrae，1995）在稳定状态下测得满负荷时的效率，这些效率中不包括辅助设备的能耗，比如泵，冷却塔的风机，而这些设备可以增加0.060.31kw/ton（smitetal.，1996）。制冷机组在大部分时候是在部分负荷下运行的。只有在建筑物的最高热负荷时，制冷机才在额定制冷量附近运行。知道制冷机在部分负荷下效率是怎样变化的，这是很重要的。图4.2.3给出了往复式、螺杆式、旋涡式、

50、带叶片控制的离心式制冷机组、压缩机频繁启动的制冷机组在满负荷时的百分比下相应的效率（用kw/ton表示）。往复式制冷机在占满负荷较小的百分比运行时，效率增加。相反地，带叶片控制的离心式的效率在负荷为额定负荷的60以后是基本不变的,它的kw/ton值随百分数的减小而增加到满负荷时的两倍.1998年，空调制冷学会提出了一项新的标准，用来划归在部分负荷下制冷机组的运行情况。部分负荷时的效率用综合部分负荷值（iplv）这个简单的数值来表示。iplv在数值上和图4.2.3相似。用25%，50%，75%，100%负荷时的效率来计算这个简单的综合效率。在这些负荷下的度量值分别为0.12，0.45，0.42，

51、0.01。iplv的计算公式为：iplv=1/（0.01/a+0.42/b+0.45/c+0.12/d）其中a100%负荷时的效率b75%负荷时的效率c50%负荷时的效率待添加的隐藏文字内容3d25%负荷时的效率大多数的iplv由满负荷的50%，75%时的效率决定的，根据要求，制造商除了提供如图4.2.3所示部分负荷时的效率，还会提供iplv值。以下对使用在蒸汽压缩式制冷机中的四种压缩机做简要的讲述。离心式和螺杆式压缩机主要应用在制冷机组上。往复式和旋涡式压缩机应用在整体式空调和热泵中。往复式压缩机图往复式压缩机容积-压力的关系往复式压缩机是一种有确定排量的压缩机。在活塞的进气冲程时，一定量的

52、气体被吸进气缸。在压缩冲程时，气体被压缩直到排气阀打开。在每个冲程被压缩的气体数量等于气缸的体积。在制冷机中使用的压缩机根据压缩机制冷能力不同有不同个气缸的。往复式压缩机使用的制冷剂具有较小体积和相对较高的压力。使用在建筑上的往复式制冷机组目前大多采用r22。现在高速往复式压缩机所限制的压力比大约为9。往复式压缩机基本上是具有固定容积可变压力的机器。从图4.2.4所示的最粗的一条线（16个气缸）可以看出：内容积流量发生较小的变化，压缩机的排气压力会发生各种变化。在一些制冷机中的冷凝器的运行情况与周围环境有关。比如，在制冷时，通过冷却塔后，冷凝压力会降低。当空调负荷降低时，所需的循环制冷剂流量会

53、减少，这种结果负荷特性在图4.2.4中用实线表示了，从右上角指向左下角。压缩机必须要和系统压力和所需的流量相匹配。往复式压缩机在任何水平时会让排气压力达到它限定的压力比。不同制冷能力的需求可以通过卸载一个或多个气缸来实现。这种卸载又可通过阻止手动或自动开启的吸气和排气阀门来完成。制冷能力也可通过使用变速或多速电动机来控制。当控制好了压缩机的制冷能力，在部分负荷时的其他影响因素也应考虑，比如（a）压缩机震动的影响和卸载装置运行时的噪声；（b）较低的制冷剂流速需要较好的回油；（c）在较低制冷能力时膨胀装置正确的使用。在大多数往复式压缩机中，在正常运行时油从压缩机被打到制冷系统中。系统必须仔细设计使油能回到压缩机曲轴箱，以便连续润滑，同时也能避免对热交换器表面的污染。往复式压缩机通常是轻载启动的。一般转矩的电动机也能适用于启动。当蒸汽机用于往复式压缩机启动时，压缩机所需的转矩和蒸汽机的