![专业英语高版本_第1页](http://file4.renrendoc.com/view/0111e9482ec570877ac92bf6a14f0fd4/0111e9482ec570877ac92bf6a14f0fd41.gif)
![专业英语高版本_第2页](http://file4.renrendoc.com/view/0111e9482ec570877ac92bf6a14f0fd4/0111e9482ec570877ac92bf6a14f0fd42.gif)
![专业英语高版本_第3页](http://file4.renrendoc.com/view/0111e9482ec570877ac92bf6a14f0fd4/0111e9482ec570877ac92bf6a14f0fd43.gif)
![专业英语高版本_第4页](http://file4.renrendoc.com/view/0111e9482ec570877ac92bf6a14f0fd4/0111e9482ec570877ac92bf6a14f0fd44.gif)
![专业英语高版本_第5页](http://file4.renrendoc.com/view/0111e9482ec570877ac92bf6a14f0fd4/0111e9482ec570877ac92bf6a14f0fd45.gif)
版权说明:本文档由用户提供并上传,收益归属内容提供方,若内容存在侵权,请进行举报或认领
文档简介
Numericalinvestigationonthermalperformanceofgroundheatexchangersusingphasechangematerials
asgroutforgroundsource
heatpumpsystem汇报人:张恒1.Introduction2.Methods3.Resultsanddiscussion4.Conclusions1.IntroductionThereisnodoubtthattheenergyshortagehasbecomeahugeproblem,bothlocallyandglobally.Groundsourceheatpumpsystemisoneofeffectiveandefficientwaytotackletheproblem.Theverticalboreholegroundheatexchanger(GHE)iswidelyutilizedinChina.GSHPsystemsneedalargeamountoflandarea,however,Chinesepracticalsituationsisalargepopulationwithrelativelylittleland.Inordertoreducethelandutilization,phasechangematerialswereproposedtouseasbackfillmaterialinsteadofcommonmaterials.ItcandecreaseboreholenumberforthefixedenergydemandUsingPCMisaneffectivemeasuretoreducethesuddenheatingorcoolingwaveuponthegroundandsmooththethermalwavegeneratedfromtheoperationofaGSHP.2.Methods2.1.Modeldomains2.MethodsAsshowninFig.2,itwasclearlyseenthatwhenthegridnumbercontinuestoincreaseabove750,000,thedeviationofresultsbetweenthelastthreemodelswerelessthan1%.ThemodelparametersarelistedinTable1indetails.2.Methods2.2.MathematicalmodelsTheliquidfraction
β,canbedefinedasleft.Liquidfractionisanotherparametertodescribephasechangerate.2.Methods2.3.ModelvalidationAsshowninFig.3,thetemperaturevariationtrendofr1,r2,r3withtimewasinagoodagreementwiththemeasuredvalues.Therefore,itcouldbedemonstratedthatthepresentsimulationmodelwassufficientlyaccuratetoanalyzethermalperformanceofgroundheatexchangersusingphasechangematerialsasgrout2.Methods2.4.Evaluationmethodologies2.4.1.Effectiveness2.4.2.Thermaleffectsradius3.ResultsanddiscussionThosePCMbackfillmaterialwereusedindiscontinuousairconditioningsystem,whichwasrunfor10handstopfor14h.TheGSHPoperationhoursareselectedtorepresenttypicalworkingconditionsattheofficebuilding:8am–18pmfromMondaytoFriday.
Thefollowingworkisappliedtothecoolingmode,whichthefluidiswarmerthanthesoilunderthesummercondition.BothofthemarefilledwiththesameflowrateintheU-tube.3.Resultsanddiscussion3.1.EffectsofbackfillmaterialsonthermalperformanceofGSHEFourdifferentmaterialswerechosenasthebackfillmaterialforGHEs.Soilisthecommonbackfillmaterial,andanotherthreematerialsarePCMs,suchasParaffinRT27,Acid
andEnhancedacid.3.ResultsanddiscussionTheheattransferratedropswiththeincreaseoftime.Itisunderstandablebecausethermalfluidinthetubereleasesheattothesoil.Thenthetemperatureofsoilincreasedwiththetime,whilethetemperaturedifferencebetweenthermalfluidandgroutdecreased
withtime.Theeffectivenessdroppedmonotonouslywithtimeinallcasedconsidered.ComparedtheeffectivenessofacidtothatofRT27,thehigherphasechangetemperaturebroughtthehighereffectiveness.3.ResultsanddiscussionLiquidfractionisanotherparametertodescribephasechangerate.OnecanseefromFig.4(c)thattheliquidfractiongrewmonotonouslywithtimeinallcasesconsideredIfcomparedtheliquidfractionofacidwiththatofRT27,thehigher
phasechangetemperaturebroughtthelower
liquidfraction.Moreover,comparedtheliquidfractionofacidwiththatofenhancedacid,thehigherthermalconductiveresultedinthehigherliquidfraction3.Resultsanddiscussion3.ResultsanddiscussionThethermaleffectsradiusofgroundsourceexchangersat1.5mdeepafterrunning10hwaspresentedinTable3.Inspiteoflowthermalconductivities,therearemanyadvantagesofPCM.Obviously,thePCMtemperaturekeepsconsistentinsolidificationandmeltingprocess,whichisbeneficialforstableoperationoftheGSHPsystem.Moreover,temperaturechangeofsurroundingsoilcanbereducedwithPCMsasbackfill.Thus,thespacingofboreholecanbelessened,andlanddemandcanbereducedeffectivelyaswell.Therefore,PCM,tosomeextent,wassuitableforuseasbackfillmaterialintheGSHPsystem.However,heattransferenhancementsmustbeadopted.(λ:0.2-0.5)3.Resultsanddiscussion3.2.EffectsofinitialgroundtemperatureonthermalperformanceofGSHEFig.6illustratestheeffectivenessofPCMsystemsandheattransferrateunderdifferentinitialgroundtemperatureconditions.Moreover,theeffectivenessofPCMsystemsincreasedasinitialgroundtemperaturedecreased,whichisconsistentwiththeheattransferrateinthisprocess.3.ResultsanddiscussionItmeansthattheproportionofliquidincreasedastheinitialtemperatureclosedtothephasechangetemperature.Specifically,theLiquidfractionincrementinthethreeinitialgroundtemperatureincreased
significantlyasinitialgroundtemperaturegrew,andthisincrementgrewovertime.3.ResultsanddiscussionTable4presentsthatthethermaleffectsradiusofgroundsourceexchangersat1.5
mdeepafterrunning10hunderthreeinitialgroundtemperatureconditions.Admittedly,lowerinitialgroundtemperaturecontributedtolargerheattransferrateandhighereffectiveness.Incontrast,theliquidfractionofPCMandthethermaleffectsradiussawanoppositetrend.Thatistosay,theheattransferrateandthethermaleffectsradiusvarytotheoppositedirectionwiththeinitialgroundtemperature.(undetermined)3.Resultsanddiscussion3.3.EffectsofpipespacingonthermalperformanceofGSHEAsFig.8(a)and(b)show,theheattransferrateandtheeffectivenesshavethesimilartrendsduringthese10h.Fig.9(a)and(b)presentthattheheattransferrateandtheeffectivenessincreasedaspipespacingrose.Especially,heattransferrateofthe60mmpipespacingcasedroppedquickerthanthatoftheothertwocases,whichmeansthattheheattransferconditiondeterioratedseriouslyunderthe60mmpipespacingcondition.3.ResultsanddiscussionFromFig.8(c),liquidfractionofPCMwith80mmpipespacingandthatwith60mmpipespacinghavethesimilartrendduringthe10h.However,liquidfractionofPCMwith100mmpipespacingwaslowerthanthosetwo.Thethermaleffectsradiusofgroundsourceexchangersat1.5mdeepafterrunning10hwerepresentedinTable5.Table5showsthatthethermaleffectsradiuswith100mmpipespacingislargestamongthethreecases.3.ResultsanddiscussionFromFig.9(a),thetemperatureofr0isconstant
inthefirstthreehours,andexperiencedadramaticgrowthinthenextsixhours.After10h,itdecreasedduetothestopofthesystem.Itisunderstandablethatthelatentheatplayedadominaterolewhentheacidwasmeltinginthefirstthreehours,andthenthesensibleheatplayedadominaterolewhenthematerialhadmelted.ThisphenomenoncanbeprovedbyFig.9(d)with60mmpipespacingU-tube.Therewasasharpincreaseintemperatureofr=0with80mmpipespacingU-tubeafter8h,asFig,9(b)shows.Itdelayed5hthanthatwith60mmpipespacingUtube,whichisbecausethemeltingtimeofthematerialbetweentwopipesislonger(Fig.9(d)).Incontrast,thetemperatureofr=0with100mmpipespacingU-tubekeptconstant
afterreachingthemelttemperature(seeFig.9(c)).Thematerialbetweenthetwopipesdidnotfullymelt,andtherewassomesolidacidbetweenthem,asshowninFig.9(d)100mm.Consequently,larger
pipespacingledtolargerheattransferrateandhighereffectiveness.Meanwhile,liquidfractionofPCMwith100
mmpipespacingU-tubewaslowerthantheothertwocases.In
contrast,thethermaleffectsradiusislargestamongthethreecases.Thatistosay,theheattransferrateandthethermaleffectsradiuschangeintheoppositedirection3.Resultsanddiscussion3.4.Combinedeffectsofpipespacingandinitialgroundtemperature4.ConclusionsInthepresentstudy,theprocessofmeltingofaPCMgroutinGSHPhasbeenexplorednumerically.TransientnumericalsimulationswereperformedusingANSYSFLUENT15.0software.Tobeginwith,thethermalperformancesoffourbackfillmaterialswereinvestigated.Furthermore,theinitialgroundtemperaturefactorandpipespacingfactorwerestudied,respectively.Finally,thecombinedeffectsofpipespacingfactorandinitialgroundtemperaturefactoronthethermalperformanceofGSHPwereanalyzed.4.ConclusionsThemainconclusionsaresummarizedasfollows:(1)Duetoitssmallthermaleffec
温馨提示
- 1. 本站所有资源如无特殊说明,都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
- 2. 本站的文档不包含任何第三方提供的附件图纸等,如果需要附件,请联系上传者。文件的所有权益归上传用户所有。
- 3. 本站RAR压缩包中若带图纸,网页内容里面会有图纸预览,若没有图纸预览就没有图纸。
- 4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
- 5. 人人文库网仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对用户上传分享的文档内容本身不做任何修改或编辑,并不能对任何下载内容负责。
- 6. 下载文件中如有侵权或不适当内容,请与我们联系,我们立即纠正。
- 7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
最新文档
- 大学生非物质遗产创业项目
- 训练退出申请书
- 大学生创业贷款项目及材料
- 小学四年级数学三位数除以两位数单元检测口算题
- 三年级数学因数中间或末尾有零的乘法综合考核练习题大全附答案
- Unit 2 语法填空同步练习(含解析)-七年级英语下册(沪教版2024)
- 专科教育解析
- 语法掌握之道
- 音乐鉴赏之道
- 艺术历史探秘
- 宁波2025年浙江宁波市鄞州区卫健系统其他事业单位招聘事业编制46人笔试历年参考题库附带答案详解
- 小学二年级数学上册口算题
- 2024-2025学年第二学期(2025春季学期)学校工作计划(附2月-6月安排表)
- 广东省佛山市禅城区2024-2025学年八年级上学期期末考试语文试题(含答案)
- 2025年中国山泉水市场前景预测及投资规划研究报告
- 第04课 输入输出与计算(说课稿)2024-2025学年六年级上册信息技术人教版
- 部编五下语文教学多元评价方案
- GB/T 18109-2024冻鱼
- 《榜样9》观后感心得体会二
- 《西安交通大学》课件
- 重庆市2024-205学年秋高二(上)期末考试历史试卷(含答案)康德卷
评论
0/150
提交评论