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`毕业设计学生姓名：学号：专业：热能与动力工程题目：50kW二氧化碳热泵指导教师：评阅教师：2016年6月`毕业设计中文摘要氯氟烃作为制冷工质对环境的破坏已经成为目前世界上显而易见的问题。大气中的中的氯和溴可以与臭氧在平流层中发生剧烈的化学反应，而这些氯和溴很大部分来自制冷和发泡工业排放的氟利昂物质。目前，世界各国已经开展了新型制冷剂的研究工作，主要有包括R134a在内的HFC及其混合物来代替R12、R502、R22等。又由于《蒙特利尔议定书》的签订，可以产生温室效应的工质也被逐渐代替。二氧化碳（CO2）以其无毒，对臭氧层无影响，不产生温室效应的环保性能和热力学性质等优点，受到了研究人员与环保人士的重视。CO2临界温度较低，只有当冷凝温度低于临界温度时才能采用一般的亚临界循环。在实际中，当热汇平均温度超过CO2的临界温度时，热泵系统必须采用跨临界循环。CO2跨临界制冷循环的放热过程有较大的温度滑移，在同样的蒸发温度下可以制备出温度较高的热水，且有相较于其他热水器有较高的COP。CO2热泵系统与其他热泵系统的部件没有很大的差别，主要是由压缩机、冷凝器/气体冷却器、蒸发器和节流装置组成，辅助设备有回热器与油分离器等。关键词二氧化碳热泵系统跨临界制冷剂`毕业设计外文摘要TitleDesignof50kWcarbondioxideairsourceheatpumpAbstractCFCsasrefrigerantsdamagetotheenvironmenthasbecometheworld'sproblemobviously.Thechemicalreactionintheatmosphereofchlorineandbrominecanbefierceandozoneinthestratosphereoccurred,andthechlorineandbromineismostfromrefrigerationandfoamindustrialemissionsofFreonsubstances.Atpresent,theworldhascarriedouttheresearchworkofnewrefrigerants,mainlyincludingHFC,R134aanditsmixtureinsteadofR12,R502,R22andsoon.AndbecauseofthesigningoftheMontrealprotocol,theworkingmediumofthegreenhouseeffecthasbeenreplacedgradually.Carbondioxide(CO2)withitsnon-toxic,noeffectontheozonelayer,nogreenhouseeffectofenvironmentalperformanceandthermodynamicproperties,suchastheadvantagesofresearchersandenvironmentalprotection.ThecriticaltemperatureofCO2islow,onlywhenthecondensingtemperatureislowerthanthecriticaltemperature,thecriticaltemperaturecanbeused.Inpractice,whentheaveragetemperatureofheatsinkexceedsthecriticaltemperatureofCO2,theheatpumpsystemmustadoptthecrosscriticalcycle.TheheattransferprocessoftheCO2transcriticalrefrigerationcyclehasalargetemperatureslip,whichcanproducehotwaterwithhightemperatureatthesameevaporatingtemperature,andhasahigherCOPthanotherwaterheaters.CO2heatpumpsystemandotherpartsoftheheatpumpsystemisnotmuchdifference,mainlybythecompressor,condenser/gascooler,evaporatorandthrottledevice,auxiliaryequipment,suchasheatexchangerandoilseparator,etc..KeyWordscarbondioxideheatpumpsystemcrosscriticalrefrigerant本科毕业设计第页共II页`I目录1绪论..............................................................................................................................................11.1简介...........................................................................................................................................11.1.1CO2的性质...........................................................................................................................11.2CO2作为制冷工质的历史.....................................................................................................11.2.1CO2首次辉煌.......................................................................................................................11.2.2CO2制冷剂的再受重视......................................................................................................22CO2热力学循环分析.................................................................................................................42.1经济性能分析..........................................................................................................................42.2跨临界分析..............................................................................................................................42.2.2CO2跨临界循环特点...........................................................................................................52.2.3CO2热泵最优压力...............................................................................................................62.2.4蒸发温度的影响..................................................................................................................82.2.5压缩机效率的影响..............................................................................................................82.2.6系统高压压力的影响..........................................................................................................92.2.7吸气过热度dtsh的影响.....................................................................................................92.2.8气体冷却器出口温度t3的影响.......................................................................................103系统的设计与计算...................................................................................................................113.1压缩机的选择及热力计算...................................................................................................113.1.1选取最优压力值与COP值..............................................................................................113.1.2压缩机的选择和确定........................................................................................................123.1.3压缩机的设计检测............................................................................................................133.1.4对压缩机进行热力计算....................................................................................................153.2冷凝器的设计计算...............................................................................................................153.2.1冷凝器的类型选择..................................................................................................