空调热水器系统研究毕业论文外文文献翻译Word文档下载推荐.docx
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water-heatingonly,space-coolingandwater-heating,space-heatingandwater-heating,space-cooling,space-heating.Comparatively,thesystemcanprovidemuchbetterenergyperformanceandhigherequipmentutilizationthroughoutayear,andcauselessthermalpollutionthanheatpumpwaterheaterandcommonairconditioner.Aprototypewithfivemodeswasassembledandtestedattheambienttemperaturefrom-7℃to43℃,especiallywhenfrosting.Whenitworksinthewater-heatingmode,itcansupply55℃hotwaterwithintwominutes,andthecondensingpressureisjustsamewithcommonairconditioner.Whensomemodesswitch,thetemperatureoftheoutlethotwaterisconstant.TheoreticalanalysisandexperimentalstudyweredonetotheACWHinthisthesis:
1.Theprototypewastestedintheair-conditionerlaboratoryofGREE.Thetestingdataindicatethattheprototypeaccordswellwiththenationalstandardsofairconditionerandheatpumpwaterheater.
2.Basedontheexperimentalresults,analysiswasdoneontheACWHinmainoperatingmodesandsomeimportantconclusionsweregiven,Theresultsindicatethatthenewsystemcansaveenergythroughmulti-duties,anditcanworkstablyinfiveworkmodeswithhighefficiency.Comparedwithothermodels,thenewsystemalsoincludesair-conditioningunitandwaterheaterunit,butwithfewercomponentsandhigherreliability.Basedoncommonairconditioner,thissystemcanofferapracticablesolutioncouplingairconditionerandwaterheater.Itmustbechangingthemarketsofbothairconditionerandwaterheater.
1.INTRODUCTION
Theheatpumpwaterheater(HPWH)hasbeenusedsince1950s,mainlyforhouseholdapplications.Itabsorbsheatenergyfromtheambientairtoacquirehotwater.Inthelast20years,thestudyintendstodesignheatpumpwaterheaterwithhighreliabilityandpracticability,andmanymanufacturersturntoofferthisproductionbasedonenvironmentalprotectionandenergysaving.InSouthAfrica,HPWHhaspenetrated16percentofthemarketshareforcommercialwaterheaters.Becauseofthehighlyprimarycost,itisdifficulttobecomethealternativetothecommonwaterheater.However,ifwecanofferanairconditionercoupledwithHPWHsystem,whichcanactasairconditionerandwaterheaterwith
themaincomponentssuchasheatexchangers,compressor,four-wayvalve,andcapillarytube,theprimarycostwillbereducedanditcanrealizemultifunctioneasily.Insummer,withtherecoveryofthewasteheatofcondensation,itcanoffer“free”hotwater,andalsocanimprovethecoefficientofperformance(COP)oftheairconditioner.Whenairconditionerisnotrequiredinspringandautumn,itcanoperateinHPWHmode.Astheenhancementoftheyearroundutilization,itcanbemoreefficientandisexpectedtobecomeastrategysolvingtheairconditioningandhotwaterapplications.Herewedemonstrateanairconditioningwaterheater(ACWH)system,andtheperformanceanalysisisdescribedinthisarticle.
1.THEPRINCIPLEOFACWH
TheschematicdiagramofairconditioningwaterheatersystemisshowninFigure1.Thesystemcanofferthefollowingfiveoperatingmodes.Mode1isonlyforheatingwater;
mode2canactasspace-coolingandwaterheating;
mode3canrealizebothspace-heatingandwater-heating;
theothertwomodesarethesamewiththecommonair-conditioningcircles.Theswitchingamongallthesemodesisbymeansofon-offcontrolsofthesolenoidvalvesandfour-wayvalve.Eachmodewillbedemonstratedasfollows.
1.1WaterHeatingMode
2.1WaterHeatingMode
Thesystemcanoperateintwoheatingmodes.Theoneisdirectheatingwater;
theotherisheatingwaterwithwaterrecycleintheadiabaticwatertank.Thecontrollercanadjusttheoperatingmodeaccordingtothewaterlevelsensorsinthetank.Awatervalveisplacedatthehotwateroutletwhichcanbeadjustedtocontrolthewaterflowandkeep
thecondensingpressureconstant.Whenthetapwatergoesintothewater-refrigerantheatexchanger(WRHE),itwillbeheatedto50-55directlywithintwominutes.Ifneeded,℃theoutletwatertemperaturecanbesetbyadjustingthewatervalve.AsshowninFigure1,whenthepowerison,thecompressorsuckslow-pressurerefrigerantgasandthendischargeshigh-pressuregasintowater-refrigerantheatexchanger(WRHE),whererefrigerantiscondensedandwaterisheated
directly.Afterheatexchanges,theliquidrefrigerantflowsacrossfour-wayvalve,thenitisthrottledtolowtemperatureandlow-pressureliquidandgasbyanelectronicexpansionvalve.Refrigerantflowsintooutdooraircooledcondenserwhereitisevaporatedandbecomeslow-pressuregas.Whenthelow-pressuregasreturnstothecompressor,thecirclebeginsagain.Inthismode,valve1isclosedandvalve2isopen.Whenheatingwater,theoutdoorair-cooledunitactsasevaporator,andtheindoorfandoesn’trun.TheCOPwispresentedasafunctionofpowerQwandtheelectricpowerWasshowninEquation
(1).
COPw=Qw/W=MC△T
(1)
WhereMisthemassflowofwater;
Cisthespecificheatofwater;
△Tisthewatertemperaturedifferencebetweenoutletandinletofthewater-refrigerantheatexchanger(WRHE).
1.2Space-coolingandWater-heating(SCWH)Mode
Insummer,withtherecoveryofcondensingheat,theindoorairiscooleddownatthesametime.Comparedwithwater-heatingmode,thehigh-temperaturerefrigerantisalsocondensedintheWRHEdirectly,andthengoesthroughtheair-cooledcondensertobesuper-cooledwheretheoutdoorfandoesn’trun.Itisthrottledbycapillary1tolow-temperatureliquidandgas,andtheindoorairexchangesheatwithreturnedrefrigerant.Inthismode,valve1isopenandvalve2isclosed.Thismodecanactasspacecoolingandwaterheatingatthesametime.However,itisnotnecessarytorecovertheentirecondensingheatwhichcanbereleasedintheair-cooledcondenser.ThetotalcapacityisthesumofcoolingcapacityQcandheatingcapacityQw,andthentotalCOPcwcanbeshownasthe
Equation
(2).
COPcw=(Qc+Qw)/W
(2)
2.3Space-heatingandWater-heatingMode
RefrigerantflowsacrossWRHE,evaporator,capillary2,capillary1,andair-cooledcondenserinturn.Space-heatingandWater-heatingcanrealizeintheory.Thismodesometimesmaynotmeetcustomers’expectations,sothatitmustoperatecombinedwiththewater-heatingmodeandspacing-heatingmode.Ifneeded,anelectricheaterisavailable
2.4Space-coolingModeandSpace-heatingMode
Inthesetwomodes,refrigerantdoesn’tflowacrossWRHEorthewaterpumpandinletvalveareclosed,andthecondensingheatiscompletelyreleasedbytheoutdoororindoorheatexchanger.Infact,itisthesamewithanormalairconditioner,andisnotdescribedanymoreasabove.Insummer,space-coolingmodecanbereplacedbytheSCWHmode,whichcanusethewater-cooledandair-cooledheatexchangersatthesametime.Theperformanceofthesystemwillbeimprovedsignificantlywiththeenhancementofheattransfer.
3.EXPERIMENTS
Experimentalresearchwasperformedatanair-enthalpytestlaboratorywhichcanalsosupplywaterwithrequiredtemperatureandmassflow.Thelaboratoryincludesoutdoorchamber,indoorchamberandcontrolroom.Itconsistsofinsulatedwalls,air-handlingequipments,temperatureandhumiditycollectionsystem,airvolumetestingequipment,electriccontrolsystemandcomputerhandlingunit.Thecoolingandheatingcapacitycanbetestedbyair-enthalpytest.Airhandlingequipmentsareprovidedinbothtestchamberstocontrolthedrybulbandwetbulbtemperatures,aswellashumidity.Theindoorunitofairconditioningwasplacedinonechamber;
theoutdoorunitandadiabaticstoragetankwereplacedinanotherchamber.T-typethermocoupleswereplacedateachtemperature
testpointandpressuresweretestedbythepressuresensors.Allthetestingdatacanbecollectedanddisplayedbythecomputerhandlingsystem.
3.1PrototypeDesign
Theprototypeincludesoutdoorunit,indoorunit,andanadiabaticstoragetank.Basedonacommonairconditioner,thesystemaddsawater-refrigerantheaterexchanger,astoragetank,severalsolenoidvalves,andwaterpump.Thestoragetankisaninsulatedcylinderandwatercapacityisabout800L.TheprototypewasdesignedbasedontheschematicdiagramshowninFigure
3.2ExperimentalTestConditions
Inmode1,theambienttemperaturewasfrom-7℃to43℃,andtheinflowwatertemperaturewasfrom9℃to30℃.Theoutletwatertemperaturewassetto55℃byadjustingthewatervalve.Theotherfourmodesoperatedonlyinthenominaltestconditionsaccordingtothenationalstandardsofairconditionerandheatpumpwaterheater.TheexperimentaltestconditionsareshowninTable
4.RESULTS
Thisstudyemphasizesonthedirectheatingwater.Mode1wastestedintemperatureconditions,whilemode2justoperatedinthestandardtestingconditionshownintable1.Theprototypeisdifferentfromacommonheatpumpwaterheater,whichcanofferhotwaterwithin2minutesbymeansofheattransferoflargetemperaturedifference.Theexperimentalresultswerediscussedcombinedwiththefirsttwomodesasfollows.
4.1HotWaterOutput
ThecurvesofhotwateroutputareshowninFigure2atdifferentinflowwaterandambienttemperatures.AsshowninFigure2,thehotwateroutputtendstorisemorerapidlyathigherambienttemperatureorinflowwatertemperature.Itcanofferabout400Lhotwatereachhourwhentheinflowwatertemperatureis15℃andambienttemperatureis20℃.Fromthisfigure,wecanknowthatthehotwateroutputisrelativetotheparametersoftheinflow