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Lesson13marinerefrigeration船用制冷1.Refrigerationisaprocessinwhichthetemperatureofaspaceoritscontentsisreducedtobelowthatoftheirsurroundings.•1.制冷是把某个空间或其中的物品的温度降低到环境温度以下的过程。Marinerefrigerationemploysasystemofcomponentstoremoveheatfromthespacebeingcooled.•船用制冷利用包含许多部件的系统将热量从需被冷却的空间移出Thisheatistransferredtoanotherbodyatalowertemperature.Thecoolingofairforairconditioningentailsasimilarprocess.•这部分热量被传递给另一个温度较低的物体。空调对空气的冷却需要一个相似的过程(与此类似)。Theusualsystememployedformarinerefrigerationplantsisthevaporcompressioncycle.•船用制冷装置通常采用蒸汽压缩循环系统。2.Thebasiccomponentsofanyrefrigerationsystemworkingonthevaporcompressioncyclearethecompressor，condenser,expansionvalve,andevaporatororcoolingcoils.•2.采用蒸汽压缩循环的制冷系统的主要部件是压缩机、冷凝器、膨胀阀、蒸发器或冷却盘管。JimeiuniversityDrawingofcompressionrefrigerationsystemCompressorCondenserEvaporatororCoolingcoilsExpansionvalveLiquidreceiverTherefrigerationfluid,alsoknownasrefrigerant,isalternatelyvaporizedandliquefiedduringtherefrigerationcycle.•制冷液，也叫制冷剂，在制冷循环中交替地蒸发和液化。Thetemperature,atwhichafluidboilsorcondenses,isknownasthesaturationtemperatureandvarieswithpressure.•流体蒸发或冷凝的温度叫做饱和温度，随压力而变化。Thecompressorinarefrigerationsysteminraisingthepressureofthevaporizedrefrigerantcausesitssaturationtemperaturetorise,sothatitishigherthanthatoftheseawaterusedforcoolingthecondenser.•制冷系统中的压缩机使气化的冷剂压力升高，导致其饱和温度升高，高于用来冷却冷凝器的海水的温度。Thecompressoralsopromotescirculationoftherefrigerantbypumpingitaroundthesystem压缩机也能通过泵送来促进冷剂在系统中的循环3.Inthecondenser,therefrigerantisliquefiedbycirculatingseawater(orairfordomesticrefrigerators).Latentheat,originallyfromtheevaporator,isthustransferredtothecoolingmedium.•在冷凝器中，冷剂被循环的海水冷却液化(家用冰箱中是被空气液化)。最初从蒸发器中带来的潜热就这样被传递给冷却介质。Theliquidrefrigerant,stillatthepressureproducedbythecompressor，passestothereceiverandthentotheexpansionvalve.•液态冷剂，此时仍保持着压缩机出口的压力，通过储液器然后到达膨胀阀。4.Theexpansionvalveistheregulatorthroughwhichtherefrigerantflowsfromthehighpressuresideofthesystemtothelowpressureside.•膨胀阀是制冷剂流量的调节器，通过膨胀阀，冷剂从系统的高压侧流到低压侧。Itsthrottlingeffectdictatesthecompressordeliverypressurewhichmustbesufficienttogivetherefrigerantasaturationtemperaturewhichishigherthanthetemperatureofthecoolingmedium.•膨胀阀的节流作用要求压缩机的排出压力必须足够高以使冷剂的饱和温度高于冷却介质的温度5.Thepressuredropthroughtheregulatorcausesthesaturationtemperatureoftherefrigeranttofall,sothatitwillboilatthelowtemperatureoftheevaporator.•冷剂通过调节器后压力降低导致其饱和温度降低，于是冷剂就可以在温度较低的蒸发器里沸腾。Infact,astheliquidpassesthroughtheexpansionvalve,thepressuredropmakesitssaturationtemperaturefallbelowitsactualtemperature.•事实上，当冷剂液体通过膨胀阀时，压力降低使其饱和温度降低到低于它的实际温度。Someoftheliquidboilsoffattheexpansionvalve,takinglatentheatfromtheremainderandcausingitstemperaturetodrop.•部分液体在膨胀阀处沸腾，吸收剩余冷剂的潜热，导致其温度降低。6.Theexpansionvalvethrottlestheliquidrefrigerantandmaintainsthepressuredifferencebetweenthecondenserandtheevaporator,whilesupplyingrefrigeranttotheevaporatoratcorrectrate.•在以合适的量向蒸发器供冷剂的同时，膨胀阀对液态冷剂节流并保持冷凝器和蒸发器之间的压差。Itisthermostaticallycontrolledinmodernsystem.•现代制冷系统中采用热力膨胀阀来控制。7.Therefrigerantenteringtheevaporatorcoil,atatemperaturelowerthanthatofthesurroundingreceiveslatentheatandevaporates.•冷剂以低于环境的温度进入蒸发器盘管，吸收潜热并蒸发。Latertheheatisgivenupinthecondenser,whentherefrigerantisagaincompressedandliquefied.•当冷剂再次被压缩、液化时，热量在冷凝器里被释放。8.Duringoperation,anumberofparticularproblemscanoccurwhichwillaffecttheplantperformance.•工作中，可能会发生一系列问题，这将影响装置的性能。9.Anoverchargeorexcessrefrigerantinthesystemwillbeseenasahighcondenserpressure.Therefrigerantshouldbepumpedtothecondenserandtheexcessreleasedfromthere.•系统中加入过多的冷剂会观察到冷凝器的压力过高。冷剂应当被泵送到冷凝器里并回收多余的冷剂。10.Airinthesystemwillalsoshowasahighcondenserpressure.Withthecondenserliquidoutletclosedtherefrigerantchargeshouldbepumpedinandcooled.•系统中进气也会使冷凝器压力过高。关闭冷凝器液体出口阀，将冷剂泵入并冷却.Releasingthepurgevalvewillventofftheairwhichwillhavecollectedabovetherefrigerant.•打开放气阀，将聚集在冷剂上部的空气放掉。11.Under-chargewillalsoshowasalowcompressorpressureandlargebubblesintheliquidlinesightglass.•冷剂不足会表现为压缩机压力过低，从冷剂液体管路观察镜中能看到大量的气泡Aleaktestshouldthenbecarriedoutoverthesystemtodeterminethefaultandenableitsrectification.•此时应该对整个系统进行查漏灭漏。AquickerandmoresensitivemethodforFreonplantsistousealeakdetectorlamp.•对氟利昂装置更快速灵敏的检漏方法是使用检漏灯。Thefreonisdrawnintotheflameandtheflamewillchangecolor,goingfromgreentobluedependingontheconcentrationofthegas•氟利昂被吸入火焰时，火焰会变色，根据气体中氟利昂的浓度不同，火焰会从绿色到蓝色变化。12.Moistureinthesystemmaychangetoiceandcloseuptheregulatingvalve,resultinginadropinpressureontheevaporatorsideandariseinpressureonthecondenserside.•系统中含水会结冰堵塞膨胀阀，导致蒸发器一侧的压力降低，冷凝器一侧的压力升高。Thedriershouldbeexaminedandthedryingchemicalswillprobablyrequirereplacing.•应当检查干燥器，其化学干燥剂可能需要更换13.Refrigerationplantsareprotectedbyhighpressurecut-outs,lowpressurecut-outs,oilfailurecut-outsandsafetyvalveorburstingdiscs.•制冷装置具有高压保护，低压保护，和低油压保护，且装有安全阀或防爆盘。