換熱器中英文對照外文翻譯文獻

中英文對照外文翻譯(文檔含英文原文和中文翻譯)換熱器的優(yōu)化選型【摘要】板式換熱器的優(yōu)化選型是根據(jù)換熱器的用途和工藝過程中的參數(shù)和NTU＝KA／MC＝△t／△tm，即傳熱單元數(shù)NTU和溫差比（對數(shù)平均溫差—換熱的動力）選擇板片形狀、板式換熱器的類型和結構?！娟P鍵詞】平均溫差NTU板式蒸發(fā)器冷凝器1平均溫差△tm從公式Q＝K△tmA，△tm＝1／A∫A（t1－t2）dA中可知，平均溫差△tm是傳熱的驅動力，對于各種流動形式，如能求出平均溫差，即板面兩側流體間溫差對面積的平均值，就能出換熱器的傳熱量。平均溫差是一個較為直觀的概念，也是評價板式換熱器性能的一項重要指標。1.1對數(shù)平均溫差的計算當換熱器傳熱量為dQ，溫度上升為dt時，則C＝dQ／dt，將C定義為熱容量，它表示單位時間通過單位面積交換的熱量，即dQ＝K（th－tc）dA＝K△tdA，兩種流體產生的溫度變化分別為dth＝－dQ／Ch，dtc＝－dQ／Cc，d△t＝d（th－tc）＝dQ（1／Cc－1／Ch）,則dA＝[1／k（1／Cc－1／Ch）]·（d△t／△t），當從A＝0積分至A＝A0時，A0＝[1／k（1／Cc－1／Ch）]·㏑[（tho－tci）／（thi－tco）]，由于兩種流體間交換的熱量相等，即Q＝Ch（thi－tho）＝Cc（tco－tci），經簡化后可知，Q＝KA0｛[（tho－tci）－（thi－tco）]／㏑[（tho－tci）／（thi－tco）]｝，若△t1＝thi－tco，△t2＝tho－tci，則Q＝KA0[（△t1－△t2）／㏑（△t1／△t2）]＝KA0△tm，式中的△tm＝（△t1－△t2）／㏑（△t1／△t2）。順流△tm＝[（thi－tci）－（tho－tco）]／㏑[（thi－tci）／（tho－tci）]逆流△tm＝[（thi－tco）－（tho－tci）]／㏑[（thi－tco）／（tho－tci）]對于各種流動型式，在相同的進口、出口溫度條件下，逆流的平均溫差最大。當板式換熱器入口和出口兩流體的溫差△t1和△t2之間的差不大時，可采用算術平均溫差（△t1＋△t2）／2，一般△t1／△t2小于1.5時，可采用，若△t／△t2為3時，則誤差約為10%。1.2傳熱單元數(shù)法在傳熱單元數(shù)法中引入一個無量綱參數(shù)NTU，稱為傳熱單元數(shù)，它表示板式換熱器的總熱導（即換熱器傳熱熱阻的倒數(shù)）與流體熱容量的比值NTU＝KA／MC，它表示相對于流體熱容流量，該換熱器傳熱能力的大小，即換熱器的無量綱“傳熱能力”。對于板式換熱器來說，KA／MC＝△t／△tm，式中△t／△tm稱為溫差比，上式中的右邊的工藝過程用NTUp表示，左邊的換熱設備的條件用NTUE表示。NTUp是流體溫度的變化與平均溫差的比值，表示的是用1℃△tm的變化引起幾度流體溫度變化的值，當△tm大時，NTUp則??；當△tm小時，它有變大的傾向。相反，在NTUp變大的過程中，△tm的溫度變化較大，NTUp較小時，其△tm的溫度變化較小（見表1）。表1△tm，NTUp的關系△tm大△tm小NTUp小NTUp大NTUp大NTUp小△tm的溫度變化大△tm的溫度變化小板式換熱器的優(yōu)化設計計算，就是在已知溫差比NTUE的條件下，合理地確定其型號、流程和傳熱面積，使NTUp等于NTUE。1.3換熱過程和NTU與供熱空調相關的換熱過程如下如示：⑴用蒸汽加熱水⑵水—水換熱a.蒸汽133→133℃c.一次水65→60℃水5→65℃（生活熱水）二次水45←40℃（采暖）b.蒸汽133→133℃d.一次水14→9℃水55→65℃（采暖）二次水13←7℃（制冷）e.一次水29→24℃二次水26←21℃（制冷機的冷卻）以上5例工藝過程的NTUp（見表2）表2供熱空調工藝過程的NTUp過程△tmNTUpa133→133℃5→65℃94.86（65－5）／94.86＝0.632b133→133℃55→65℃72.88（65－55）／72.88＝0.13c65→60℃45←40℃20.00（45－40）／20＝0.25d14→9℃13←7℃1.44（13－7）／1.44＝4.17e29→24℃26←21℃3.00（26－21）／3＝1.671.4板式換熱器和NTUENTUE表示板式換熱器的能力，換熱器的面積是具有一定傳熱長度的單位傳熱體的組合，總傳熱長度是單位長度和流程數(shù)的乘積。當NTUE是總數(shù)時，若每1流程數(shù)為NTUe時，則NTUE＝n·NTUe（其中n是流程數(shù)）。當NTUe＝NTUE＝NTUp時，換熱器為單程。若NTUe﹤NTUp時，則換熱器應為多流程，故設計時應先預定n。由于每種板片單程的NTUe值基本上是定值，如適合表2中e的流量為25m3／h的單程板式換熱器的NTUe為17㎡。從NTUe＝A·K／MC可知，當NTUe為定值時，A·K成反比，仍以e為例，當K＝500kcal／㎡·h·℃時，A＝1.67×25000／500＝83.5㎡，流程數(shù)n＝83.5／17≈5。當K＝2500kcal／㎡·h·℃時，A＝16.7㎡，流程數(shù)n＝1。每一流程的NTUe如下所示：K＝500，NTUe＝NTUE／n＝0.33，K＝2500時，NTUe＝1.67。由此可知，根據(jù)NTUe即可求出換熱器的流程數(shù)，傳熱系數(shù)和傳熱面積。從以上可知，若板式換熱器設計不合理，可能使換熱面積過大，也可能使板間流速太高，阻力過大。1.5板式換熱器制造技術的進步，板片種類的增加，提高了板式換熱器對各種工藝過程的適應性。⑴大NTU（∽8），小△tm（∽1～2）的板式換熱器滿足了區(qū)域供冷和熱泵機組蒸發(fā)器、冷凝器的要求。從以上分析可知，△tm是換熱的驅動力，若△tm小，即意味著驅動力小，要實現(xiàn)兩種流體之間的換熱，必須增大傳熱系數(shù)，增大傳熱面積，為了使傳熱面積不至過大，唯一的是增大傳熱系數(shù)K。①淺密波紋板片是北京市京海換熱設備制造有限責任公司開發(fā)的新型板片，它的傳熱系數(shù)約為7000W／㎡·K，是水平平直波紋板的2倍，是人字形波紋板的1.5倍，在區(qū)域供冷中時，檢測的△tm約為1.2。在作為冰蓄冷的乙二醇和冷凍水的換熱器使用中，△tm約為1.5。②板式蒸發(fā)器、板式冷凝器也是北京市京海換熱設備制造有限責任公司開發(fā)的適應于熱泵機組的新型換熱器。與管殼式蒸發(fā)器、冷凝器相比，它具有如下優(yōu)點：單位體積內板式蒸發(fā)器、板式冷凝器的傳熱面積約是管殼式換熱器的3倍；板式蒸發(fā)器的傳熱系數(shù)約為1000～1200W／㎡·K，板式冷凝器的傳熱系數(shù)約為1500～2000W／㎡·K均為管殼式換熱器的2～3倍；在板式蒸發(fā)器上采用了使制冷劑液體分布均勻的分配器裝置，當蒸發(fā)器板片數(shù)較多時，可能會出現(xiàn)制冷劑液體分配不均的，不能充分利用所有蒸發(fā)傳熱面積，使蒸發(fā)溫度低于設計計算溫度。采用分配器后即能克服上述問題。有關單位檢測數(shù)據(jù)說明，板式蒸發(fā)器、板式冷凝器的傳熱系數(shù)在△tm約為2.5～3℃時，在1500～2000W／㎡·K之間，且阻力小，滿足了熱泵機組的要求。⑵小NTU（∽0.3～2），大△tm（∽40～90℃）的板式換熱器滿足了熱回收工藝和工藝加熱、冷卻的要求。當工藝過程在大△tm的條件下進行換熱時，說明驅動力大，所需的傳熱面積較小，對傳熱系數(shù)要求也不高，但，這種工藝過程或者工作壓力高，或者工作溫度高，或者工藝加熱、冷卻過程的液體中含有纖維或直徑較大的顆粒，對板式換熱器的承壓、耐溫能力提出了要求，對換熱器的板間距提出了要求。①排（煙）氣—水板殼式換熱器（省能器），排（煙）氣—空氣板殼式換熱器（空氣預熱器）是北京市京海換熱設備制造有限責任公司和蘭石化共同開發(fā)出來的新型板式換熱器，全焊接板式換熱器中介質的換熱是通過板管束來實現(xiàn)的，組成板管束的板片由專用模具壓制成型，全焊接式板束裝在壓力殼內。波紋板片具有靜攪拌作用，能在很低的雷諾數(shù)下形成湍流，且污垢系數(shù)低，傳熱系數(shù)是管殼式換熱器的2～3倍。為了適應換熱量大，流體壓降小的要求，板間距大，當量直徑約為28㎜。為了滿足工藝的要求板束工作壓力（反壓）P≤4.5Mpa，板束工作壓力（正壓）同殼體工作壓力，不受限制；工作溫度t≤550℃。烏魯木齊石化分公司40萬噸／年連續(xù)重整采用了進料（冷介質）和出料（熱介質）的板殼式換熱器，進料流量50t／h，進、出口溫渡88℃，470℃。出料流量50t／h，進、出口溫度100℃，500℃，對數(shù)平均溫差約38℃，總傳熱系數(shù)約為380kcal／㎡·h·℃，熱負荷達23×106kcal／h，進料壓降20Kpa，出料壓降50Kpa。②多效蒸發(fā)板式加熱器（換熱器），這種換熱器既是工藝加熱裝置，又是重要的熱回收裝置。以前由于板式換熱器的流道小（板間距1.5～5.0㎜），不適宜于氣—氣換熱和蒸氣冷凝；且易堵塞，故不宜用于含懸浮物的流體。為了盡量地發(fā)揮板式換熱器的長處，克服存在問題，適應工藝的要求，北京市京海換熱設備制造有限責任公司開發(fā)出了新型的多效蒸發(fā)板式換熱器，這種板式換熱器屬寬流道型，其板間距為8.0㎜，適合于蒸氣冷凝，適合于含懸浮物的流體，且不易堵塞，最大處理量達1200m3／h。原文NewplateheatexchangeroptimizationSelectionAbstract:TheplateheatexchangerSelectionisbasedontheoptimizationoftheuseofheatexchangersandintheprocessoftheparametersandNTU=KA/MC=△t/△tm,thatis,transferunitsofNTUandthetemperaturedifferencethan(theaveragetemperaturedifference--Heattransferinpower)chooseplateshapes,plateheatexchangerandthetypeofstructure.

Keywords:theaveragetemperaturedifferencebetweenNTUplateevaporatorcondenser1averagetemperaturedifference△tm

Whentheheatexchangertoheat-dQ,whenthetemperaturerosetodt,C=dQ/dt,Cwillbedefinedasheatcapacity,itsaidunitsoftimethroughtheexchangeofheatperunitarea,dQ=K(th-tc)dA=K△tdA,twoofthefluidtemperaturechangesweredth=-dQ/Ch,dtc=-dQ/Cc,d△t=d(th-tc)=dQ(1/Cc-1/Ch),whiledA=[1/k(1/Cc-1/Ch)]?(d△t/△t),whentheA=0pointstoA=A0when,A0=[1/k(1/Cc-1/Ch)]?㏑[(tho-tci)/(thi-tco)],becauseoftwofluidexchangebetweentheheatequivalent,thatis,Q=Ch(thi-tho)=Cc(tco-tci),thesimplifiedKnow,Q=KA0([(tho-tci)-(thi-tco)]/㏑[(tho-tci)/(thi-tco)]),if△t1=thi-tco,△t2=tho-tci,Q=KA0[(△t1-△t2)/㏑(△t1/△t2)]=KA0△tm,in-△tm=(△t1-△t2)/㏑(△t1/△t2).Down△tm=[(thi-tci)-(tho-tco)]/㏑[(thi-tci)/(tho-tci)]Countercurrent△tm=[(thi-tco)-(tho-tci)]/㏑[(thi-tco)/(tho-tci)]Forvariousflowpatternsinthesameimport,exportundertheconditionsoftemperature,theaveragetemperaturedifferencebetweenthelargestcounter-current.Whentheplateheatexchangerimportandexportofthefluidtemperaturedifferencebetweenthetwo△t1andthedifferencebetween△t2notavailablewhenarithmeticaveragetemperature(△t1+△t2)/2,General△t1/△t2lessthan1.5,Maybe,if△t/△t2for3:00,theerrorisabout10percent.1.2thenumberoftransferunitsIntheheattransferunitoftheintroductionofafewdimensionlessparametersNTU,knownasthenumberoftransferunits,itsaidplateheatexchangerofthetotalthermalconductivity(heatexchangerheatresistanceofthecountdown)andtheratiooffluidheatcapacityNTU=KA/MC,itsaidinrelationtoheatfluidflow,heattransfercapacityoftheheatexchangerofthesizeoftheheatexchangerthatis,non-dimensional"heattransfercapability."Theplateheatexchangerfor,KA/MC=△t/△tm,where△t/△tmknownasthetemperaturedifferencethan,ontherightsideoftheprocessusedNTUpthatlefttheconditionsofheattransferequipmentusedNTUEsaid.NTUpisfluidtemperaturechangesintemperatureandtheaverageratiothatisused1℃△tmofseveralchangesinthevalueoffluidtemperaturechanges,when△tmlarge,NTUpissmallwhen△tmhours,ithasbecomebiggerThetendency.Onthecontrary,inNTUplargerintheprocess,△tmofthelargertemperaturechanges,NTUpsmaller,its△tmsmallchangesintemperature(seetable1).Table1△tm,NTUprelations△tmlarge△tmsmallNTUpsmallNTUplargeNTUplargeNTUpsmall△tmlargechangesintemperature△tmsmallchangesintemperaturePlateheatexchanger,theoptimaldesign,isknownNTUEtemperaturedifferencethantheconditions,todetermineareasonablemodel,processesandheattransferarea,equivalenttoNTUpNTUE.1.3heattransferprocessandtheNTUHeatingandair-conditioningrelatedtotheheattransferprocessiftheshowareasfollows:⑴steamheatingwater⑵water-waterheatexchangera.steam133→133℃c.awater65→60℃Water5→65℃(hotwater)Secondarywater45←40℃(heating)b.Steam133→133℃d.awater14→9℃Water55→65℃(heating)secondarywater13←7℃(refrigeration)e.awater29→24℃

Secondarywater26←21℃(refrigeratorcooling)MorethanfivecasesoftheprocessNTUp(seetable2)Table2heatingair-conditioningprocessofNTUpprocess△tmNTUpa133→133℃5→65℃94.86（65－5）／94.86＝0.632b133→133℃55→65℃72.88（65－55）／72.88＝0.13c65→60℃45←40℃20.00（45－40）／20＝0.25d14→9℃13←7℃1.44（13－7）／1.44＝4.17e29→24℃26←21℃3.00（26－21）／3＝1.671.4plateheatexchangerandNTUENTUEplateheatexchangerthatthecapacityofheatexchangeristhesizeofacertainlengthoftheheatandthecombinationofheattransferunits,thetotallengthofheattransferprocessisthelengthandnumberofunitsoftheproduct.WhenthetotalnumberofNTUEis,ifthenumberofprocessesforevery1NTUe,thenNTUE=n?NTUe(wherenisthenumberofprocesses).WhenNTUe=NTUE=NTUp,theheatexchangerforone-way.IfNTUe<NTUp,theheatexchangerformanyprocesses,itshouldbedesignedtotargetn.Aseachplateofone-wayNTUevalueisessentiallyfixedvalue,suchasineTable2fortheflowof25m3/hoftheone-wayNTUeplateheatexchangerfor17squaremeters.FromNTUe=A?K/MCtellsusthatwhenNTUetobeonduty,A?Kisinverselyproportional,stilleexample,whenK=500kcal/㎡?h?℃time,A=1.67×25000/500=83.5㎡,theprocessofn=83.5/17≈5.WhenK=2500kcal/㎡?h?℃time,A=16.7squaremeters,theflowofn=1.EachprocessNTUeasfollows:K=500,NTUe=NTUE/n=0.33,K=2500when,NTUe=1.67.So,canbeobtainedunderNTUetheflowofheatexchangers,heattransfercoefficientandheattransferarea.Fromtheabovewecanseethatiftheplateheatexchangerdesignunreasonableandlikelytoheattransferareaistoolarge,mayalsobepartitionedsothatflowistoohigh,toomuchresistance.1.5plateheatexchangermanufacturingandtechnologicalprogress,platetypeofincrease,raisingtheplateheatexchangerofthevariousprocessesofadaptation.⑴theNTU(∽8),small△tm(∽1~2)theplateheatexchangertomeetthedistrictcoolingandheatpumpunitsevaporator,condenserrequirements.Fromtheaboveanalysisknow,△tmisthedrivingforceofheattransfer,if△tmsmall,meansthatthedriverofsmall,toachievetheheattransferbetweenthetwofluid,wemustincreaseheattransfercoefficient,increasingheattransferarea,inordertoHeattomakeuptoolarge,istheonlyincreaseheattransfercoefficientK.

①shallowplateofcorrugatedBeijing,Beijingistheheattransferequipmentmanufacturerslimitedliabilitycompanydevelopedanewtypeofplate,theheattransfercoefficientofabout7000W/㎡?K,istheleveloftheflatcorrugatedboardtwotimes,ischevronCorrugatedsheetsof1.5times,intheregionalcooling,thedetectionof△tmisabout1.2.Asinicestorageofethyleneglycolandchilledwateruseintheheatexchanger,△tmisabout1.5.②plateevaporator,condenserplateBeijing,Beijingisalsotheheattransferequipmentmanufacturerslimitedliabilitycompaniesadapttothedevelopmentofanewtypeofheatpumpunitsintheheatexchanger.Andtheshell-and-evaporator,comparedtothecondenser,whichhasthefollowingadvantages:unitvolumeintheevaporatorplate,theplatecondenserisaheattransferareaofshellandtubeheatexchangerofthreetimestheplateevaporatorheattransfercoefficientAbout1000~1200W/㎡?K,thecondenserplateheattransfercoefficientofabout1500~2000W/㎡?KareshellheatexchangertwotothreetimestheplateontheevaporatorusedtoRefrigerantdistributorofliquidevenlydistributeddevices,whentheevaporatorplateafewmore,maybeunevendistributionofliquidrefrigerantandcannottakefulladvantageofalltheheatandevaporationarea,evaporationtemperaturelowerthanthecalculateddesigntemperature.Afteradistributorovercometheseproblems.Detectionofdataontherelevantunits,evaporatorplate,theplatecondenserintheheattransfercoefficient△tmabout2.5~3℃,in1500~2000W/㎡?Kbetweentheresistanceandsmall,satisfyingtheheatpumpunitsRequirements.⑵smallNTU(∽0.3~2),the△tm(∽40~90℃)oftheplateheatexchangertomeettheheatrecoveryprocessandtheprocessheatingandcoolingrequirements.Whentheprocessinthe△tmconductedunderconditionsofheattransfer,thatdrivingforce,theheatandthesmaller,theheattransfercoefficientdemandisnothigh,butthatthisprocessorhigh-pressurework,orworkHightemperature,orprocessheatingandcoolingprocessintheliquidcontainingfiberdiameterorlargerparticles,theplateheatexchanger,thepressure,temperatureandabilitytorequest,theheatexchangertotheplatespacingrequirements.

①Pai(breathing)gas-watershellheatexchanger(Provincecan),Pai(breathing)gas-shell-airheatexchangers(airpreheater)isaheatexchangerinBeijingBeijing-equipmentmanufacturerslimitedliabilityPortlandpetrochemicalcompaniesandco-developedanewtypeofplateheatexchanger,allweldedplateheatexchangerintheheattransferthroughthemediumtoachievethecontrolboard,composedofboardcontrolbytheplateforformingmoldsuppression,all-welded-Beaminstalledinthepressureshell.Corrugatedplatewithstaticmixing,inaverylowReynoldsnumberformedundertheturbulence,andlowcoefficientofdirt,theheattransfercoefficientistheshellandtubeheatexchangerofthetwoorthreetimes.Inordertoadapttotheheattransfer,fluidpressureontherequest,boardspace,equivalentdiameterofabout28mm.Inordertomeetthedemandsofworkpre