Lesson-16-Marine-Refrigeration

动力工程系PowerEngineeringDepartmentWuhanInstituteofShipbuildingTechnologyPowerEngineeringDepartmentLuobin动力工程系PowerEngineeringDepartmentLesson16MarineRefrigeration第16课船舶制冷动力工程系PowerEngineeringDepartment•Thenaturaltransferofheat(热的自然传递)isfromahotbodytoacoldbody,thefunctionofarefrigerationplant(制冷装置)istoactasaheatpump(热泵)andreverse(逆向)thisprocesssothatroomscanbemaintained(保持)atlowtemperaturesforthepreservationoffoodstuffs(储存食物),oraircanbecooledfortheairconditioning(空调).•热的自然传递是由热的物体传向冷的物体。制冷装置的作用是像热泵一样，使上述热传递逆向进行，从而使冷却空间能保持低温以储存食物，或使空气冷却用于空调。动力工程系PowerEngineeringDepartment•Theusualsystememployed(应用)formarinerefrigerationplants(船舶制冷装置)isthevaporcompressioncycle(蒸气压缩式制冷循环),forwhichthebasicmarinevaporcompressionrefrigeratingsystemisshowninFig.16-1.•船舶制冷装置通常应用的是蒸气压缩式制冷循环，基本原理如图16-1所示。动力工程系PowerEngineeringDepartment制冷剂液体在蒸发器内以低温与被冷却对象发生热交换，吸收被冷却对象的热量并气化；•产生的低压蒸汽被压缩机吸入，经压缩后以高压排出；压缩机排出的高压气态制冷剂进冷凝器，被常温的冷却水或空气冷却，凝结成高压液体；•高压液体流经膨胀阀时节流，变成低压低温的气液两相混合物，进入蒸发器，其中的液态制冷剂在蒸发器中蒸发制冷，产生的低压蒸汽再次被压缩机吸入。•如此周而复始，不断循环。动力工程系PowerEngineeringDepartment•Thepressureoftherefrigerantgas(冷剂气体)isincreasedinthecompressor(压缩机)andittherebybecomeshot.•冷剂气体经压缩机压缩升压、升温。•Thishot,highpressuregasispassedthroughintoacondenser(冷凝器).•高温高压蒸气流入冷凝器。•Dependingon(根据)theparticularapplication(用途的不同),therefrigerantgaswillbecooledeitherbyairorwater,andbecauseitisstillatahighpressureitwillcondense(冷凝).•根据用途的不同，冷剂蒸气被空气或者水冷却，在高压下冷凝。动力工程系PowerEngineeringDepartment•Theliquidrefrigerant(液态冷剂)isthendistributedthroughapipenetwork(管网)untilitreachesacontrolvalve(控制阀)alongsideanevaporator(蒸发器)wherethecoolingisrequired.•然后液态冷剂流经管网到达蒸发器前的控制阀处。•Thisregulatingvalve(调节阀)meters(控制,测量)theflow(流量)ofliquidrefrigerantintotheevaporator,whichisatalowerpressure.•调节阀控制进入蒸发器的低压液态冷剂的流量。动力工程系PowerEngineeringDepartment•Airfromthecooledspace(制冷空间)orairconditioningsystemispassedovertheevaporatorandboilsoff(蒸发)theliquidrefrigerant,atthesametimecoolingtheair.•从制冷空间或空调装置出来的空气流经蒸发器使冷剂蒸发的同时自身也得到冷却。•Thedesignofthesystemandevaporatorshouldbesuchthattheentireliquidrefrigerantisboiledoffandthegasslightlysuperheated(过热)beforeitreturnsto(回到).thecompressorlowpressuretoberecompressed(重新压缩).•设计系统和蒸发器时要求满足液态冷剂在重新回到压缩机吸气口之前全部气化并且稍微过热。动力工程系PowerEngineeringDepartment•Thusitwillbeseen(由此可见)thatheatthatistransferred(传递)fromtheairtoevaporator(蒸发器)isthenpumped(泵送)roundthesystemuntilitreaches(到达)condenser(冷凝器)whereitistransferredorrejectedtotheambientair(外界环境)orwater.•由此可见，空气传给蒸发器的热量在系统中泵送至冷凝器并在冷凝器中传给外界环境或海水。动力工程系PowerEngineeringDepartment•Itshouldbenotedthat(需要注意的是)whereanaircooledcondenser(风冷的冷凝器)isemployedinverysmallplants,suchasprovisionstorerooms(备件库),adequateventilation(足够的通风)isrequiredtohelpremove(去除)theheatbeingrejectedbythecondenser.•需要注意的是当风冷的冷凝器用在小型装置上时，比如备件库，要用足够的通风来把冷凝器产生的热量带走。动力工程系PowerEngineeringDepartment•Also,inthecaseof(就...来说)watercooledcondensers(水冷的冷凝器),freshwaterorseawatermaybeemployed(使用).•而且对于水冷的冷凝器则要使用淡水或者海水。•Freshwaterisusualwhenacentralfreshwater/seawaterheatexchanger(淡水/海水换热器时)isemployedforallengineroom(机舱)requirements.•当有满足整个机舱用的淡水/海水换热器时，通常应用淡水冷却。动力工程系PowerEngineeringDepartment•Wherethisisthecase,becauseofthehighercoolingwatertemperaturetothecondenser,deliverytemperatures(出口水温)fromcondenserswillbehigherthanthatonaseawatercoolingsystem(海水冷却系统).•在这种场合，由于进口的冷却水温较高，冷凝器出口水温将比海水冷却系统的高。动力工程系PowerEngineeringDepartment•Refrigerants•冷剂动力工程系PowerEngineeringDepartment•Generallyspeaking(一般来说)thesearesub-dividedinto(细分)primary(制冷剂)andsecondaryrefrigerants(载冷剂).•一般来说，冷剂可以细分为制冷剂和载冷剂。•Primaryrefrigerants•制冷剂•Thisistherefrigerant(制冷剂)employedinthecompressor(压缩机),condenser(冷凝器)andevaporatorsystem(蒸发器系统)andcertainpropertiesareessentialrequirements(基本要求).•用在压缩机冷凝器和蒸发器系统中的制冷剂，需要满足一些基本要求。动力工程系PowerEngineeringDepartment•Forexampleitwillboiloff(蒸发)orevaporate(蒸发)atalowtemperatureandreasonablepressure(合适的压力)anditwillcondense(冷凝)atatemperaturenearnormalseawatertemperature(正常海水温度)atsreasonablepressure.•例如它需要在合适的压力下，能够在较低温度下蒸发而在接近正常海水温度时冷凝。•Therefrigerantmustalsobefreefrom(无)toxic(毒),explosive(易爆),flammable(易燃)andcorrosive(腐蚀性)propertieswherepossible.•冷剂还必须具有无毒、不易爆、不易燃的特性，同时尽可能无腐蚀性。动力工程系PowerEngineeringDepartment•Somerefrigerantshavecriticaltemperatures(临界温度)abovewhichtherefrigerantgaswillnotcondense(冷凝).•有些冷剂具有临界温度，在此之上蒸气不会冷凝。•Thiswasoneofthedisadvantages(缺陷)ofcarbondioxide(二氧化碳),whichwasusedformanyyearsonships.•船舶使用二氧化碳作为制冷剂有一个缺陷。动力工程系PowerEngineeringDepartment•Shipsoperating(航行)inareaswithveryhighseawatertemperatureshaddifficultyinliquefying(液化)thecarbondioxidewithoutsomeadditionalsub-coolingsystem(额外的制冷子系统).•当船舶在高温海域内航行时，如果没有额外的制冷子系统则无法使二氧化碳液化。•Afurtherdisadvantage(一个更严重的弱点)ofcarbondioxidewastheveryhighpressureatwhichthesystemoperated,resultinginlargeandheavymachinery.•二氧化碳的一个更严重的弱点是它要求系统在非常高的压力下工作，这样使得整个装置变得笨重。动力工程系PowerEngineeringDepartment•Secondaryrefrigerants•载冷剂•Bothlargeairconditioning(大型空调)andcargocoolingsystems(货物冷藏系统)mayemployasecondaryrefrigerant.•载冷剂应用在大型空调和货物冷藏系统中。•Inthiscasetheprimaryrefrigerantevaporator(制冷剂蒸发器)willbecirculated(循环)withthesecondaryrefrigerant(载冷剂),whichisthenpassedtothespacetobecooled.•