深冷液體存貯與輸送的實(shí)現(xiàn)

CryogenicStorageandDelivery

WhyitWorks

深冷液體存貯與輸送的實(shí)現(xiàn)

Jan.5th,2012CHTRAMAT-EN-003(2012)Overview概述Gassesarestoredasliquidforseveralreasons氣體之所以液化存貯Higherstoragedensity高存貯密度EasierDeliverylogistics容易輸送EasierPumping易泵輸送Useoftherefrigerationcontent制冷技術(shù)的使用WhatastorageTanksDoes貯罐可以做到StorestheLiquid,keepingitcold.貯存液體,使其保持低溫AllowsforRefilling可重新充裝MaintainsPressure保持壓力AllowsforLevelMeasurement保持液位AllowsforWithdrawal使用Gasapplications氣體使用LiquidApplications液體使用Protectsitselffromoverpressurization.防止罐體超壓UnderstandingaLiquefiedGas理解液化氣體Importantfluidpropertiesinclude重要的液體參數(shù)包括Pressure壓力Temperature溫度Density密度Energy能量Therelationshipbetweenthesepropertiesisfixedforafluid.Knowinganytwoallowsustopredicttherest.對(duì)任一液體而言,這些參數(shù)之間的關(guān)系是確定的,任何兩個(gè)已知的參數(shù)都可以推導(dǎo)出其他的參數(shù).Theleastintuitive,butmostinfluentialistheenergyofthefluid.最直接也是最有影響的參數(shù)是能量.UnderstandingtheInfluenceofenergyonthefluidiscriticaltounderstandwhycryogenicsystemsworkthewaytheydo.理解液體能量有助于理解深冷系統(tǒng)工作的原理Thermodynamicsisthestudyofhowenergyaffectsthestateofafluid.此處的熱力學(xué)是解釋能量如何影響液體狀態(tài)的學(xué)科Energy(heat)willmovefromonebodytothenextifthereisatemperaturedifferencebetweenthem.Thehigherthedifference,thefastertheenergyistransferred.Energyisalsointroducedwhenworkisdoneontheliquid.Anytimetheliquidistransferred,thereisanincreaseintheenergyoftheliquid.兩個(gè)物體之間存在溫差時(shí)即可產(chǎn)生傳熱.溫差越大,傳熱越快.對(duì)液體做功也能產(chǎn)生能量.輸送液體時(shí)液體的能量會(huì)增加.IntuitiveMaterialProperties物質(zhì)特性參數(shù)Property特性Description描述Units單位ExampleofInfluenceondesign設(shè)計(jì)相關(guān)示例Pressure壓力Force/UnitArea單位面積受力PSI,PSIA,PSIGPa,MpaInnerVesselThickness內(nèi)容器壁厚OuterVesselThickness外容器壁厚Temperature溫度Responsethatanamountofmaterialhasbasedontheenergyitiscarrying表示物體冷熱程度Fahrenheit,Rankine華氏度Celsius,Kelvin攝氏度MaterialSelection材料選擇Vaporizers汽化器PBCoils自增壓器Density密度Mass/UnitVolume單位體積的質(zhì)量SpecificVolume=1/Density#/Ft3#/Gal.Kg/literKg/NM^3Heat(Energy)Property能量參數(shù)Property特性Description描述Units單位ExampleofInfluenceondesign設(shè)計(jì)相關(guān)示例InternalEnergy內(nèi)能(U)Energymeasurethatincludesmolecularenergyatconstantvolume.物體在恒定體積下包括分子運(yùn)動(dòng)的能量總和dU/dT=CvBTU/lbJ/kgHoldTime壓力保持時(shí)間(analysiswherepressurechangeswithinacontrolmass研究在恒定質(zhì)量下壓力變化)Enthalpy焓(H)Energymeasurethatincludesmolecularenergyandworkenergyatconstantpressure.物體在恒壓下的能量和功的總和dH/dT=CpH=U+PVBTU/lbJ/kgPBCoilsizing自增壓器計(jì)算VaporizerSizing汽化器計(jì)算NERCalculation蒸發(fā)率計(jì)算(analysiswheremasschangeswithinacontrolvolume研究在恒定體積下質(zhì)量變化)Entropy熵(S)Energymeasurethatisusedtomeasurelostworkpotentialandenergyefficiency.Tds=dU=PdVTds=dH-VdPBTU/lb-RJ/kg-KUsedindesigningefficientliquefactionsystems.Helpfulinevaluatingtheenergyaddedbypumps.Page7名詞解釋Cryogenic深冷Abranch

ofengineeringthatrelatestotheproductionandeffectsofverylowtemperature,usually-230°Fandcolder.Heat

leak熱泄漏Cavitation氣穴PartialorfulllossofpumpprimeduetoinsufficientsubcoolingorNetPositiveSuctionHeadDepressurizationFlashLossVaporizationcausedbyreducingthegasphasepressuretosomethinglessthansaturatedvaporpressureoftheliquid.Page8Condensation冷凝The

conversionofvaporsintoliquidbycoolingthevapors.Equilibrium平衡Astatewheretheliquidandgasphasescoexistathesametemperatureandvaporpressure.Saturation飽和Astatewheretheliquidandgasphasescoexistin

equilibrium.名詞解釋Page9Subcooling過(guò)冷度RaisinggasspacepressureabovethenormalvaporpressureofasaturatedliquidcreatingNetPositiveSuctionHead(NPSH).Stratification分層Averticaltemperaturegradientwithcolderproductatthebottomandwarmerproductatthetop.Entrainment霧沫Liquiddropletscarriedalongwithaflowinggasstream.名詞解釋Page10三相點(diǎn)三相點(diǎn)triplepoint是指在熱力學(xué)里，可使一種物質(zhì)三相（氣相，液相，固相）共存的一個(gè)溫度和壓力的數(shù)值三相共存時(shí)具有固定的溫度和壓強(qiáng)氦，是唯一沒(méi)有三相點(diǎn)的物質(zhì)例：水的三相點(diǎn)在0.01℃（273.16K），611.73Pa..\LNGStation\Water_boil.wmv水的蒸發(fā)過(guò)程開(kāi)始水的溫度：78℉（25.5℃）飽和蒸汽壓：3.169x103Pa水開(kāi)始沸騰：79℉（26.1℃）飽和蒸汽壓：3.3x103PaPage11Page12臨界點(diǎn)臨界點(diǎn)criticalpoint一種熱力學(xué)狀態(tài)，此時(shí)在最高可能溫度下物質(zhì)的液態(tài)和氣態(tài)可以平衡共存臨界溫度criticaltemperature物質(zhì)處于臨界狀態(tài)時(shí)的溫度。物質(zhì)以液態(tài)形式出現(xiàn)的最高溫度。溫度不超過(guò)某一數(shù)值，對(duì)氣體進(jìn)行加壓，可以使氣體液化，而在該溫度以上，無(wú)論加多大壓力都不能使氣體液化，這個(gè)溫度叫該氣體的臨界溫度。在臨界溫度下，使氣體液化所必須的最小壓力叫臨界壓力。臨界壓力criticalpressure物質(zhì)處于臨界狀態(tài)時(shí)的壓力（壓強(qiáng)）。在臨界溫度時(shí)使氣體液化所需要的最小壓力。液體在臨界溫度時(shí)的飽和蒸氣壓。Page13飽和狀態(tài)、飽和蒸氣壓、飽和溫度飽和狀態(tài)saturationcondition液體汽化時(shí)，其分子不斷從液體中逸出，同時(shí)也有分子從蒸氣中進(jìn)入液體，當(dāng)達(dá)到同一時(shí)間進(jìn)出液體的分子數(shù)相等并平衡時(shí)的狀態(tài)。飽和蒸氣壓saturatedvaporpressure

在一定溫度下，與液體或固體處于相平衡的蒸氣所具有的壓力稱為飽和蒸氣壓。同一物質(zhì)在不同溫度下有不同的蒸氣壓，并隨著溫度的升高而增大。飽和溫度saturationtemperature是指液體和蒸氣處于動(dòng)態(tài)平衡狀態(tài)即飽和狀態(tài)時(shí)所具有的溫度ts。飽和狀態(tài)時(shí)，液體和蒸氣的溫度相等。飽和溫度一定時(shí)，飽和壓力也一定；反之，飽和壓力一定時(shí)，飽和溫度也一定。溫度升高，會(huì)在新的溫度下形成新的動(dòng)態(tài)平衡狀態(tài)。物質(zhì)的某一飽和溫度必對(duì)應(yīng)于某一飽和壓力。Page14蒸發(fā)、汽化、沸騰和沸點(diǎn)汽化vaporization物質(zhì)從液態(tài)轉(zhuǎn)變?yōu)槠麘B(tài)的過(guò)程蒸發(fā)evaporation物質(zhì)從液態(tài)轉(zhuǎn)化為氣態(tài)的相變過(guò)程沸騰boiling在液體表面和內(nèi)部同時(shí)發(fā)生的劇烈汽化現(xiàn)象沸點(diǎn)boilingpoint液體沸騰的溫度蒸發(fā)和沸騰的聯(lián)系它們都是液體汽化的方式，即都屬于汽化現(xiàn)象，液體在蒸發(fā)和沸騰的過(guò)程中，都需要吸收熱量。..\VCD\Nitrogen_boil.wmvPage15沸點(diǎn)、沸騰和蒸發(fā)蒸發(fā)和沸騰的區(qū)別蒸發(fā)是液體在任何溫度下都能發(fā)生的汽化現(xiàn)象，而沸騰是液體在一定溫度（沸點(diǎn)）下，并繼續(xù)加熱，才能發(fā)生的汽化現(xiàn)象。蒸發(fā)是只在液體表面發(fā)生的緩慢的汽化現(xiàn)象，而沸騰是在液體表面和內(nèi)部同時(shí)發(fā)生的劇烈的汽化現(xiàn)象。蒸發(fā)時(shí)液體溫度會(huì)下降，而沸騰中液體溫度保持不變（在液體表面上壓強(qiáng)不改變的前提下）。影響蒸發(fā)速度的因素是：液體的表面積，液體的溫度，液體表面附近的空氣流速；影響沸點(diǎn)的因素是：液體表面上的氣壓，液體的純凈程度。影響沸騰速度的因素：液體體積和原先的溫度沸騰時(shí)有氣泡產(chǎn)生，而蒸發(fā)時(shí)則無(wú)氣泡產(chǎn)生。蒸發(fā)的微觀本質(zhì)為：由于分子的熱運(yùn)動(dòng)，使液體表面的分子離開(kāi)液體，進(jìn)入空氣中。蒸發(fā)在任何溫度都會(huì)進(jìn)行，只是溫度越高越快，反之越慢。而沸騰必須溫度在沸點(diǎn)，且繼續(xù)吸熱。沸騰的微觀本質(zhì)為：由于汽化劇烈產(chǎn)生了氣泡，不僅液體表面的分子要離開(kāi)液體，液體內(nèi)部氣泡壁上的分子也要離開(kāi)液體，進(jìn)入空氣中。沸騰現(xiàn)象中包含了蒸發(fā)現(xiàn)象，但蒸發(fā)現(xiàn)象卻不包括沸騰現(xiàn)象。Page16汽化潛熱汽化潛熱latentheatofvaporization單位質(zhì)量的液體轉(zhuǎn)變?yōu)橄嗤瑴囟鹊恼魵鈺r(shí)吸收的熱量稱為汽化潛熱，簡(jiǎn)稱汽化熱它隨溫度升高而減小，因?yàn)樵谳^高溫度下液體分子具有較大能量，液相與氣相差別變小。在臨界溫度下，物質(zhì)處于臨界態(tài)，氣相與液相差別消失，汽化熱為零。PVT/PETSurface壓力/體積（能量）/溫度Thereisarelationshipbetweenthepropertiesofafluidthatisknownforeachtypeoffluid.Wecandesignequipmentbasedonthisrelationship對(duì)任意一種特定流體，其特性之間都存在固定關(guān)系，可以利用其進(jìn)行設(shè)備設(shè)計(jì)Anytwopropertieswilldictatethethird.Thiscreatesathreedimensionalpropertyrelationship任意兩個(gè)參數(shù)可以確定第三個(gè)，以此確定三者函數(shù)關(guān)系Thephysicalstateofthefluidisbasedonwhereweareonthissurfacerelationship流體的物理狀態(tài)是基于它處于關(guān)系函數(shù)中的位置Themostcriticalareaofthesurfaceisthevapordome.Inthisregionwedefinethetransitionfromliquidtogas.P-T曲線中關(guān)鍵區(qū)域是飽和區(qū)域（飽和液相線及飽和汽相線以下），此區(qū)域內(nèi)液體汽化為氣體。Abovethedome,thefluidactsinapredictablemannerandfollowsalinearrelationshipbetweenpressureanddensity.曲線以上，流體在壓力和密度之間存在線性關(guān)系Pureliquidisessentiallyincompressibleduetopressure,yetitsdensitywillchangewithincreasingenergy純液體是不可壓縮的，但隨著能量的變化它的密度會(huì)產(chǎn)生變化。PVT/PETSurface壓力/體積（能量）/溫度Saturation/Equilibrium飽和/平衡Fluidthatisonthedomespaceissaidtobeinequilibriumorsaturated飽和區(qū)內(nèi)的流體處于飽和或平衡狀態(tài)Asaturatedstateisoftenfurthernotedbythecoincidentcorrespondingpressureortemperaturetothisposition.飽和狀態(tài)下壓力或溫度可以維持不變.WhenSaturatedapressure,anyreductioninpressure,orincreaseinheatwillresultinthefluidchangingfromliquidtovapor.Vaporizationorboiling飽和壓力下，任何壓力的降低或能量的增加都導(dǎo)致液體的汽化（汽化或沸騰）Commensuratelyanyincreaseinpressureorreductioninheatwillresultinthefluidchangingfromvaportoliquid.Condensation相應(yīng)地，任何壓力的升高或能量的減少都會(huì)導(dǎo)致氣體的液化（冷凝）Afluidthatinliquidstateandmarginallyawayfromthedomebyvirtueofexcessivepressureissaidtobesub-cooled.Suchaliquidhascapacityabsorbheatand/orlosepressureandstillnotbegintovaporizeorboil液態(tài)的流體在增壓會(huì)形成過(guò)冷。它在吸熱并/或降壓的情況下并不汽化或沸騰。Saturation飽和IncreasingTemperature增壓IncreasingPressureRequiredtoKeepMoleculesfrombeingLiberated(Boiling)沸騰IncreasingDensity密度增加IncreasingHeatEnergy能量增加Sub-Cooled過(guò)冷Equilibrium平衡Boiling沸騰StorestheLiquid,keepingitcold液體存貯及保溫Heattransfersslowlyintothestoredliquid熱量會(huì)緩慢傳導(dǎo)給液體Liquidnearthewallheatsupbeforetheinternalliquid靠近筒壁的液體首先升溫Thereduceddensitycausetheliquidtomigratetothetopoftheliquid,separatinganddistributingtheheatunevenly升溫后的液體密度降低,向上移動(dòng),導(dǎo)致了熱量傳遞的不均勻Thesamehappensinthevaporsideofthetank罐的氣相存在同樣現(xiàn)象Thisunevendistributionoftheheatcreatessubcoolontheliquidandiscalledstratification熱量的不均勻分布導(dǎo)致液體的過(guò)冷,稱做分層Tostratify,thereneedstobeisolationbetweenthetemperatures.Horizontaltankswillstratifylessthanverticaltanks.Smalltankslessthanlargeones.Tanksinmotionwillnotstratifyatall.分層的形成需要溫度的不均勻不分布.臥罐分層少于立罐;罐體積越大分層越明顯;移動(dòng)罐不分層AllowsforRefilling重新充裝Asthetankislikelyattachedtoausedevice,interruptingtheuseofatankforfillingisundesirable,thereisaneedtomaintaintankpressurewhilerefilling罐總在使用當(dāng)中,為了充裝打斷使用是不可接受的.因此充裝時(shí)需要維持罐內(nèi)壓力Introductionofliquidtothetankwillcausethevaporinthetoptobecompressed.Thiswillraisethepressure充液時(shí)頂部液體汽化導(dǎo)致空間壓縮、壓力上升Introductionofliquidintothewarm,stratified,vaporspacewilltendtoremoveheatfromthevaporandinturncauseittocondense.Thiswillreducethepressureinthetank把液體注入暖的、分層的氣相空間將導(dǎo)致氣體的熱量傳到液體使之凝結(jié)。這將使罐的壓力降低。Havingbothatopandbottomfillvalvesallowforthetanktobeconnectedtoauseapplicationandbefilledwithoutinterruption.Thefillingoperatorwillmanipulatethetopandbottomfillvalvewhilemonitoringthetankpressure.頂充和底充同時(shí)使用使得充裝時(shí)不用停止罐的使用。操作者可以監(jiān)控壓力，選擇使用頂充或底充。MaintainsPressure壓力保持Inordertoincreasepressure,tanksareconfiguredwithapressurebuilding,orPB,circuit.貯罐配置PB來(lái)實(shí)現(xiàn)升壓Theforceoftheweightofliquidisallowedtodriveliquidoutofthetankandthroughanambientairheatexchanger.液體自身的重量使液體流入熱交換器Theliquidfirstabsorbsheatuntilitissaturatedatthetankpressure液體首先在貯罐壓力下吸熱至飽和Continuedheatingbeginstoboiltheliquid繼續(xù)吸熱至沸騰Someadditionalheatingofthevaporwilloccurbeforethegasisreturnedtothetopofthetank.氣體回到罐內(nèi)前將繼續(xù)吸收一部分熱量Themoreeasilythetankisstratified,themoreeffectivethePBsystemwillwork.Verticaltankshavetheadvantageofincreaseliquidhead(push)andmoreadvantageousdistributionofheat液體分層越容易，PB效率越高Somevapormaybereducedinvolumeonceitenterstheconfinesofthecoldtank進(jìn)入冷罐后部分蒸汽的體積會(huì)變小.PBCircuit增壓回路ThePBcircuitisintendedtoreplacethevolumeofliquidremovedwithgasatthesamepressure增壓循環(huán)的目的是在同壓下用氣體取代減少的液體Onlyliquidheadisavailabletodrivethemassthroughthecircuit只有液柱壓力能夠驅(qū)動(dòng)循環(huán)Liquidsideregulatorsdeliverhighercapacitiesbuttendtoovershootonrecovery液相調(diào)壓閥能夠提供更多的液體給氣相空間以補(bǔ)足失去的液體AllowsforLevelMeasurement液位測(cè)量ThesamepressurethatdrivesthePBalsoisusedtodriveadifferentialpressuregaugeforestimatingthelevelinthetank.驅(qū)動(dòng)增壓的壓力同樣能夠驅(qū)動(dòng)差壓式壓力計(jì)顯示貯罐內(nèi)的液位Thegaugewillshowthelevelbetweenthesurfaceinthetankandthesurfaceofliquidintheliquidphaseline.Thisapproximatesthelevelinthetank表頭能夠顯示罐內(nèi)液面和液相管內(nèi)液面之間的差值，近似于罐內(nèi)的差值。AllowsforLevelMeasurement液位測(cè)量Abruptchangesinpressurewilleitherexpandorcompressthevaporportionoftheliquidphaseline.ThiswillinturnmaketheDifferentialpressuregaugevary.突然的壓力變化將會(huì)導(dǎo)致液相管內(nèi)蒸汽的膨脹或壓縮，這將導(dǎo)致差壓式壓力表的變化Overtime,heatleakintotheliquidphaselinewillreturnthegaugetoanormalindication.Thishowevermaytakeseveralhours.Pressurechangesthatoccuroverminutescanresultinmisleadingindications.隨著時(shí)間的變化，進(jìn)入液相管的熱量將使得表頭回到正常的指示。然后需要也許幾個(gè)小時(shí)，壓力變化將很快導(dǎo)致不正確的指示Asimilarissuecanoccuriftheequalizationvalveisleftopenforaperiodoftime.Theequalizationvalveshouldonlybeopenedaftertheisolationvalvesareclosed當(dāng)平衡閥打開(kāi)時(shí)，類似情況也會(huì)出現(xiàn)。只有隔離閥關(guān)閉時(shí)才能打開(kāi)平衡閥AllowsforWithdrawalLiquidApplications液體使用Asliquidiswithdrawn,thevaporinthetopofthetankwillexpandtoaccommodatethemissingliquidvolume.取液時(shí)，罐頂蒸汽將膨脹以充填液相空間Ifthiscontinuesuntilthepressuredropstothesaturationpressureoftheliquid,theliquidwillbegintoboil.壓力將一直降低到液體的飽和壓力，液體開(kāi)始沸騰Liquidapplicationsthataredrivenbycryogenicpumpsareaspecialcase.Inefficienciesinpumpswilladdheattoandreducethepressureontheliquidthatisinthepump.Suchheatwillboiltheliquidinthepumpcausingthepumptostopworking.Excessiveboiling,orcavitation,inthepumpcancauseseveredamagetothepump.Maintainingsomesub-coolontheliquidisimportantforpumpperformance.Theliquidmusthavecapacitytoabsorbsomepressuredropandheatadditionwithoutboiling.用低溫泵驅(qū)動(dòng)的液體使用情況有所不同，泵做功會(huì)把熱量帶到泵里的液體使之壓力降低。這些熱量將會(huì)使液體沸騰并使泵停止工作。過(guò)度的沸騰或者氣穴使泵損壞，保持一定的過(guò)冷對(duì)泵有利。液體應(yīng)該有一定的吸納壓降和熱量而不導(dǎo)致沸騰的能力。Tomaintainsub-cool,aPBsystemisemployed.TheamountofflowthroughhePBisverysmall.TheliquidthroughthePBisexpandedfromtheliquiddensitytothevapordensity.TypicallythePBflowrateonlyneedstobeabout5%oftheliquidflowratefromthetank.使用增壓系統(tǒng)以維持過(guò)冷。通過(guò)增壓系統(tǒng)的流量極小，它從液體膨脹為氣體。一般而言通過(guò)增壓系統(tǒng)的流量?jī)H為液體使用流量的5%Athermo-Siphontankmaintainssub-coolattheinletofthepumpbycontinuouslyflowingcoldliquidfromthebottomofthetankacrossthepumpinletandbacktothebottomofthetank.Thisflowisinducedbytheinefficiencyheatofthepump.Astheheatwarmsthecoldliquid,itsdensityisreduced.Thisdifferenceindensitycreatesasmallpressuredifferenceandaconvectiveflow.Aslongastheconvectiveflowexceedsthepumpspeed,thetankswillkeepasmallamountofsubcoolontheliquidfromtheliquidheadofthetank.Ifthepumpspeedgreatlyexceedsthisconvectiveflow,aPBsystemmayneedtobeemployed.熱虹吸罐通過(guò)不斷地從罐底部抽取冷的液體通過(guò)泵入口并回到罐的底部來(lái)維持泵入口的過(guò)冷。泵的做功產(chǎn)生熱量使流量降低。熱量使冷的液體加熱導(dǎo)致了液體密度的降低，密度的差異造成了極小的壓力差異和對(duì)流。由于這一對(duì)流速度大于泵的速度，罐將保持液體一定的過(guò)冷度。如果泵速大于過(guò)渡，則需要使用增壓系統(tǒng)。AllowsforWithdrawalLiquidApplications液體使用AllowsforWithdrawal

Gasapplications氣體使用Gasapplicationsarethosewherethecustomerisgoingtousetheproductingaseousform.Thismeansthatthecryogenisgoingtobevaporizedtoagasbeforeitreachestheapplication.氣體使用用于客戶要求使用氣態(tài)產(chǎn)品的場(chǎng)合，這意味著在使用前深冷液體應(yīng)該已經(jīng)蒸發(fā)成氣體。Theliquidwithdrawnneedstohaveitsvolumereplacedasintheliquidwithdrawal,orthepressurewilldropandpotentiallydisrupttheenduser.提液后突出部分應(yīng)被填充，或意味著壓力將會(huì)降低并影響最終使用。Althoughmaintainingsub-coolisnotcritical,maintainingpressurefortheenduseapplicationis.HereagainthePBisusedtomaintainpressure.盡管維持過(guò)冷并不重要，但維持一定的壓力以確保最終應(yīng)用很重要。需要用增壓系統(tǒng)來(lái)維持壓力。.Agasuseapplicationalsoallowsustowithdrawfromthevaporphaseofthetankifdesired.如果有需要，同樣可能從氣相空間來(lái)提取氣體供使用。Doingsocreatestheopportunitytoquicklycorrectanyover-pressureissuesinthetank.如此，將有機(jī)會(huì)快速糾正罐內(nèi)的過(guò)高壓力。Thiscircuit,calledandeconomizercircuit,iscontrolledbyaregulatorthatopensataprescribedpointtypicallyabovethePBsetpoint.這一循環(huán)被稱為經(jīng)濟(jì)回路，它由一個(gè)在設(shè)定壓力高于增壓開(kāi)啟壓力的調(diào)壓閥控制。Vaporisdriventhroughthecircuitbytheliquidheadgeneratedinadiptubethatrunsthelengthofthetank.蒸汽由液柱靜壓力驅(qū)動(dòng)通過(guò)回路，此回路為一根與罐體高度相同的下行的管路Whenopen,amixtureofliquidfromthebottomandvaporfromthetopisdrawnintothefinalvaporizerandtothecustomer.Sincetheyareusinggasphaseproduct,suchamixtureisofnoconsequencetothecustomer.當(dāng)回路開(kāi)啟時(shí)，從底部的液體和頂部的氣體混后后進(jìn)入汽化器并供給用戶。由于客戶最終使用的是氣體，因此氣液混合物對(duì)用戶沒(méi)有影響。AllowsforWithdrawal

Gasapplications氣體使用Gas-Use/PB氣體使用/增壓

Gas-Use/Economizing氣體使用/經(jīng)濟(jì)回路P.B.Regulator增壓調(diào)壓閥EconomizerRegulator經(jīng)濟(jì)閥VaporizerDesign汽化器Vaporizersshouldbedesignedtoconsidericingeffectonefficiencies汽化器設(shè)計(jì)考慮結(jié)冰對(duì)效率的影響Excessivegasvelocitiescancreateentrainmentthatwilldecreaseexitgastemperatures過(guò)高氣體流速引起的夾帶會(huì)降低氣體溫度Exitgastemperaturescanonly“approach”ambient.(typically20degreeFisused)氣體溫度最高接近環(huán)境溫度Protectsitselffromoverpressurization過(guò)壓保護(hù)Asliquidabsorbsheat,itexpands.Ifthereisnoroomforsuchexpansion,thepressurewillrisequicklyinatank.液體吸熱后會(huì)膨脹，如果沒(méi)有可膨脹的空間，壓力會(huì)急劇上升。Thetankshavereliefvalvesthatwillopeninsuchaninstance.Sincethevolumetricflowrateofthereliefvalveismanytimelargerthanthevolumetricgrowthrate,thepressurewillquicklycorrectitself.Indoingso,therewillbeliquiddischargefromthereliefvalve.Thisisundesirablesinceithardonthelifeofthevalve,itejectscryogenictemperaturefromthetankandthevalvemaybemorelikelytostickopen.在此情況下，貯罐的安全閥會(huì)打開(kāi)。由于安全閥泄放量遠(yuǎn)大于壓力上升速率，壓