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1、www.kaobo100.com中国考博辅导首选学校中国政法大学考博英语模拟试题及其解析Theuseofheatpumpshasbeenheldbacklargelybyskepticismaboutadvertisers’claimsthatheatpumpscanprovideasmanyastwounitsofthermalenergyforeachunitofelectricalenergyused,thusapparentlycontradictingtheprincipleofenergyconservation.Heatpumpscirculateafluidr
2、efrigerantthatcyclesGengduoyuanxiaowanzhengkaoboyingyuzhentijiqijiexiqinglianxiquanguomianfeizixundianhua:silinglingliuliubaliujiuqiba,huojiazixunqq:qiqierliuqibawusanqialternativelyfromitsliquidphasetoitsvaporphaseinaclosedloop.Therefrigerant,startingasalow-temperature,low-pressurevapor,en
3、tersacompressordrivenbyanelectricmotor.Therefrigerantleavesthecompressorasahot,densevaporandflowsthroughaheatexchangercalledthecondenser,whichtransfersheatfromtherefrigeranttoabodyofair.Nowtherefrigerant,asahigh-pressure,cooledliquid,confrontsaflowrestrictionwhichcausesthepressuretodrop.Ast
4、hepressurefalls,therefrigerantexpandsandpartiallyvaporizes,becomingchilled.Itthenpassesthroughasecondheatexchanger,theevaporator,whichtransfersheatfromtheairtotherefrigerant,reducingthetemperatureofthissecondbodyofair.Ofthetwoheatexchangers,oneislocatedinside,andtheotheroneoutsidethehouse,s
5、oeachisincontactwithadifferentbodyofair:roomairandoutsideair,respectively.Theflowdirectionofrefrigerantthroughaheatpumpiscontrolledbyvalves.Whentherefrigerantflowisreversed,theheatwww.kaobo100.com中国考博辅导首选学校exchangersswitchfunction.Thisflow-reversalcapabilityallowsheatpumpseithertoheatorcool
6、roomair.Now,ifundercertainconditionsaheatpumpputsoutmorethermalenergythanitconsumesinelectricalenergy,hasthelawofenergyconservationbeenchallenged?No,notevenremotely:theadditionalinputofthermalenergyintothecirculatingrefrigerantviatheevaporatoraccountsforthedifferenceintheenergyequation.Unfo
7、rtunatelythereisonerealproblem.Theheatingcapacityofaheatpumpdecreasesastheoutdoortemperaturefalls.Thedropincapacityiscausedbythelesseningamountofrefrigerantmassmovedthroughthecompressoratonetime.Theheatingcapacityisproportionaltothismassflowrate:thelesst
