Numerical Simulation of Freezing Progress of Plasma

1、Numerical Simulation of Freezing Progress of PlasmaY+Yu-taoWANG+Chao【Abstract】Inthispaper，weusegambitandfluenttostudythetimeneededandthetemperaturedistributionoftheplasmainthethreefrozenmethodsofair-cooled，plate-contactandalcohol-immersionquickfreezing，thisnumericalsimulationwasusedtosolvethelimitat

2、ionoftheequipmentintheactualexperiment，soastoguidetheexperimentalwork.【Keywords】Component；Plasmafreezing；Coolingrate；Freezingmethods；TemperaturedistributionPlasmaqualityisaffectedbytherateofrapidfreezingofplasma1-3.Plasmamadefromwholebolddonations，inspiteofbeingdilutedwithanticoagulantsattherateof9：

3、1，centrifugedfilteredandfrozento-30andstoreat-30，usuallycontainslevelsofproteinsandcoagulationfactorswithinthenormalrangesseeninfreshlydrawnplasmafromhealthyindividuals【4】.Rapidfreezingisconsideredtobeimportantinassuringplasmaquality，althoughcleardataonanoptimumfreezingrateisstillinglacking.，rapidfr

4、eezingisalsologisticallyimportantforbloodbanks.Accordingtothewayoffreezing，theplasmaquickfreezing【5】machinemainlyincludesair-cooled，plate-contactandliquid-immersionwithusingdifferentquick-freezingmethods，thecostoftheequipmentisdifferent，thetimerequiredforfreezingandthequalityofthefrozenplasmaarediff

5、erent6-7.Inthispaper，themathematicalmodelofplasmawasestablishedforanalyzingtheheattransferprocessofthreeplasmaquick-freezingmethods.ByusingANSYS-FLUENT，theair-cooled，plate-contactandalcohol-immersionquickfreezingprogresswerestudied.Thesimulationresultswererecorded，analyzedandcompared.Theplasmamodelo

6、fplasmawassimplifiedasarectangularmodel，andthetemperaturefieldofthreedifferenttypesoffreezerwassimulated.Thecharacteristicsofthechangeanddistributionwereanalyzedanddiscussed，whichprovidedthetheoreticalbasisfortherapidfreezingprogressofplasmaThemathematicalmodelofplasmawasestablishedbyanalyzingtherap

7、idfreezingofplasma.Thetemperaturedistributionandvariationofthreedifferentfreezingmethodsweresimulated1NumericalSimulationofPlasmaFreezingUsingGambittostructurephysicalpackedplasmamodelbeforethenumericalsimulation，andmeshmodel，themodelwillbeimportedintotheFluenttosolvethemodel，andsetparameter，setregi

8、onal，setthreemethodsboundaryconditionsair-cooled，plate-contact，alcohol-immersion，settemperaturemonitoringpoints，thencarryoutiterativecalculationandanalysisthefinalresult.endprint1.11SolutionmethodThefreezingprogressforquick-frozenplasmaisnumericallyinvestigatedbyusingafinitevolumesolver，ANSYS-FLUENT

9、.Inthemathematicalmodel，thefollowingassumptionsareconsidered：Themodelisassumedtobeidealcuboidduetothebloodbankcommonlyuse200mlpackedplasma.Flowisturbulence.Thethermo-physicalpropertiesofthefluidareconstant.Themainmodetotransferheatfromfreezingmediumairoralcoholtoplasmaisconvectionheattransfer.Theini

10、tialplasmatemperatureofthefreezingprocessis277.15K，thefreezingpointtemperatureoftheplasmais265.15Kandwhenthecentraltemperatureis243.15K，thesimulationisended.Theinitialtemperatureofair，plateandalcoholis228.15KPlasmaconsistsof90%ofwaterand9%ofprotein，sotheplasmadensitywas1.025-1.030，andtheplasmaviscos

11、itywas0.0000142Pa·s.Thespecificheatcapacityofplasmais3000J/kg·K.Consequentlythecomplicatedheattransferproblemischangedtoanunsteadythree-dimensional，thermalproperty-variableconductiveheattransferproblemwiththefirstandthirdboundaryconditions.AccordingtheFourierslaw，theheatcanbeexpressedas：Q=

12、-S1Theheatgotthroughtheunitofvolumeintimeswas：Q1=-？蒽？鄣Vdsd2AccordingtheGausslaw：Q1=-？蒽？鄣V？犖2Tdxdydzd3Thereleasedheatbytheelementofvolumeduring1to2：cTx，y，z1-Tx，y，z，2dxdydz=-cdxdydz4Accordingtotheenergyconservationlaw：Q1=Q25Sothegoverningequationcanbewrittenas：c=？犖·？犖T6c=+7Theinitialconditionis：T

13、=T0=0Theboundaryconditionis：-=hT-Tf，x=x1-=hT-Tf，y=y18-=hT-Tf，z=z1Inthemobilephase-changeinterface，mustsatisfy：Tsxt，yt，zt，=T1xt，yt，zt，=Tp9s+-1+=sL+10Thethermalconductivitybeforefreezing：1=w+1-p11Thethermalconductivityafterfreezing：2=1+mi-w12WherTandrefertothetemperatureandtime，respectively，whilethesu

14、bscriptsfrepresentthefreezingmedium；，candstandforthedensity，specificheatandheatconductivity，respectively，whilethesubscriptsw，pandirepresentthewater，proteinandice，respectively；s，l，pandL，standforthesolidphase，liquidphase，phase-changeandlatentheat.endprintBecauseofthechangeofplasmathermalconductivity，U

15、DFisusedtosetthethermalconductivityofplasma.Theprogramisasfollows：#include“udf.hDEFINE_PROPERTYuser_thermal，cell，threadfloattemp，th；temp=C_Tcell，thread；Iftempth=5.5806-0.0122*temp；elseth=0.5592；returnth；2ResultsanddiscussionDifferentformsofplasmafreezerareusedinthemedicalfield，thecomparisonfactorbet

16、weenthemisthetimerequiredtocompletetherapidfreezing，thatis，whenthetemperatureofthecentralpointoftheplasmareaches-30.AndtheD-valuebetweenthesurfacetemperatureandthecentertemperatureisalsoanimportantfactor.2.1Air-cooledfrozenFromFig.1，wecandrawtheconclusions：whentheplasmacentertemperaturedownto-30，fre

17、ezingtimeis4143s，thatis69min，whentheplasmatemperaturemonitoringvertexdownto-30，freezingtimeis1380s，thatis23min，whentheplasmamonitoringmiddlepointtemperaturedroto-30，freezingtimeis3985s，itis66min.Therapidfreezingofplasmafromtheplasmasurfacetotheinterior，thesurfacetemperatureislow，wherthetemperatureat

18、theapexandattheedgeislowest，becausethedisturbanceofcoldairisstrengthenedattheapexandattheedges，whiletheboundarylayerisdestroyedandtheheattransferisenhancedhere.Fromtheangleofthecrosssectionnephogram，thetemperaturedistributionfromthecentertothecircumferenceisannular，thecentertemperatureisthehighest，t

19、hetemperatureneartheedgeisparalleltotheedgeofthelayer.Thetemperaturechangeofplasmacenterisdividedintothreesections，precooling，crystallizationandcryogenicsection，itisobviousthattheconstanttemperatureofcrystallizationphaseis265.15K，andaccountsforthetimeinthewholefrozenplasmain3/4，cryogenicsectionofthe

20、plasmaislargerthanprecoolingsection，2.2Plate-contactfrozenFromFig.2，wecandrawtheconclusionsthat，whentheplasmacentertemperaturedownto-30，freezingtimeis1461s，thatis24.4min；whentheplasmatemperaturemonitoringvertexdownto-30，freezingtimeis1415s，thatis23.6min，whentheplasmamonitoringmiddlepointtemperatured

21、roto-30，freezingtimeis1450s，itis24.2min.Thefreezingofplasmabeginswiththecontactsurfaceofplasmaandflatplate，andthetemperatureofthecontactsurfacebetweenplasmaandplateisthelowest.endprintFromtheangleofthecrosssectionnephogram，atthebeginningoffreezing，theplasmatemperaturedistributionisapproximatelyparal

22、lelwiththecontactsurface，andthecentertemperatureisthehighest.Withthequickfreezing，thetemperaturedistributiondevelopsgraduallyfromthecentertotheperiphery.Thetemperaturechangeofplasmacenterisdividedintothreesections，precooling，crystallizationandcryogenicsection，itisobviousthattheconstanttemperatureofc

23、rystallizationphaseis265.15K，andinthewholefrozenplasmaintimeisaboutthewholeprocessof4/7.Thetemperaturedrorateoftheprecoolingsectionislargerthanthatinthecryogenicstage，whichdoesnotseemtoaccordwiththelawoftheheatconductivityoftheplasmainthecryogenicsectionthanthatintheprecoolingsection.Thisisbecause，f

24、orcontactheatconduction，thetemperatureD-valuedrivingforceplaysamajorfactor，andthetemperatureD-valuebetweentheslabandtheplasmaintheprecoolingsectionislarger，sothetemperaturedroprateisgreater.2.3Alcohol-immersionfrozenFromFig.3，wecandrawtheconclusions：whentheplasmacentertemperaturedownto-30，freezingti

25、meis1235s，thatis20.6min，whentheplasmamonitoringmiddlepointtemperaturedroto-30，freezingtimeis1114s，itis18，6min.Therapidfreezingofplasmatakesplacefromtheplasmasurfacetotheinterior，andthesurfacetemperatureoftheplasmablockislowestduetothecontactofalcoholat-45，whichisclosetothetemperatureofthealcoholsolu

26、tion.Fromtheangleofthecrosssectionnephogram，withtherapidfreezingtime，thetemperaturedistributionisgraduallystratified，andthecentertemperatureisthehighest.Thetemperaturechangeofplasmacenterisdividedintothreesections，precooling，crystallizationandcryogenicsection，itisobviousthattheconstanttemperatureofc

27、rystallizationphaseis265.15K，andaccountsforthetimeinthewholefrozenplasmain3/4.3ConclusionsInthethreeforms，thefastestfreezingisalcoholimmersionfreezing，20.6min.Followedbyplatecontactplasmafastfreezing，24.4min；timefortheair-cooledplasmaisthelongest，69min.Theaircooledplasmaquickfreezingmachineisthefirs

28、tgenerationofplasmaquickfreezingmachine.Theplasmafreezingprocesscanbedividedinto3stages，theprecoolingsection，thecrystallizationsectionandthedeepfreezesection.Theplasmafreezingtimeinthecrystallizationsectionismorethanhalfofthewholefrozenprocess，andthetimeisthelongest.endprintTheair-cooledplasmafreezi

29、ngmethodiscarriedoutfromtheplasmasurfacetotheinterior；theplate-contactandalcohol-immersionfreezingiscarriedoutbycontactingtothecenter.Theplasmatemperaturedistributioninplate-contactplasmafreezingmethodismoreuniform；however，theD-valueofthesurfacetemperatureandinternaltemperatureofaircooledplasmarapid

30、freezingandalcoholimmersionplasmafreezingarelarger.Thetemperatureprofilesofaircooledplasmarapidfreezingandalcoholimmersionplasmafreezingaresimilar，andbothofthemareannularfromtheperipherytothecenter，thetemperatureinthecenteristhehighest.Thefrozenplasmabytheplate-contactfreezingisdistributedlikearugbywhichtheupanddowntemperaturesofplasma，theinterfacearethelowestwhilethecentertemperatureisthehighest.Thetemperatureinthecenteristhehighest，anditgraduallydevelopsintoalayereddistributionwhenitisclosetothecontactsurfacebetweentheplateandtheplasma.【References】【1】KumarMA.Coagulop