chemical engineering thermodynamics che 3062beaucag/classes/chethermobeaucage/che thermo... ·...

ChemicalEngineeringThermodynamics

ClassmeetsMTWRfrom12:20to1:15Baldwin755HelpsessionsW3-5405ERC

IntroductoryChemicalEngineeringThermodynamicsSecondEdi7onJ.RichardEllio;andCarlT.LiraISBN978-0-13-606854-9h;p://chethermo.net/

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Prof.GregBeaucagebeaucag@uc.eduh;p://www.eng.uc.edu/~beaucag/Classes/ChEThermoBeaucage.htmlTA:ZheZhangzhang2z5@mail.uc.edu670ERC513-x

CHE3062

ChemicalEngineeringThermodynamics

Quizzes:WeeklyquizcomposedofquesKonssimilartohomeworkandexampleproblems.~EveryThursdayGroupHomework:WeeklyGroupHomework.Wewillgothroughhomeworkinaworksession.~EveryWednesday.(HelpsessionWednesdays3-5405ERC.)HomeworkisdueWednesdaynightatmidnight.E-mailapdfofthehomeworktochethermouc@gmail.com(Youcanuseasmartphoneapplike“instapdf”tomakepdfofhomework.)Final:ComprehensiveFinalcomposedofquesKonsfromweeklyquizzes.(Weightedas8quizzes.)Gradeis90%AverageofFinalandQuizzesand10%Homework.

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CourseLogis7cs

ChemicalEngineeringThermodynamics

Finalle;ergradeswillbebasedonclassgradeusingthefollowingscale:Aisbetween90.0and100.0;Bisbetween80.0and89.9;Cisbetween70.0and79.9;Disbetween60.0and69.Onlywholegradeswillbegiven,i.e.thegradeisBfor80or89.Thosewitha"natural"90orabovefromquizgradesbeforethefinaldonotneedtotakethefinal.Thecomprehensivefinaliswortheightquizgrades.

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CourseLogis7cs

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PleasedothisbyTuesdayJanuary11.FirstHomeworkisdueWednesdayJanuary12atmidnight.

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PlantToursWewillhavenon-mandatoryplanttours.Thepurposeistoseesomeoftheprocesseswewillstudy.A;endanceataplanttourcountsfor50replacementpointsonaquiz,i.e.itreplacesyourlowgradeby½100.Ifyourlowgradeis30/100thisbecomesa65/100.Ifyouarrangeaplanttourfortheclassyougettwoquizgradesreplacedwith100plus50%ifyoua;end.The7mingforplanttoursisvariable.Fridayamernoonisagood7meforme.

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PlantToursLastYearRheingeistBreweryMillerBrewery(nearDayton)Nease(Harrison)ShepherdCatalysts(Norwood)SteamPlantWestCampusSteamPlantEastCampusKrausMaffei(Covington)Cincinna7WaterPlantEsteOleoChemicals(Ivorydale)

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OutlineofClass:

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Energyisthecapacitytodowork.PotenKal,kineKc,molecular,bond,nuclear,magneKc,Coloumbic.WorkistheintegralofforceKmeschangeindistance.SurfaceEnergy,itrequiresenergytomakeasurface.KineKcenergyofagasatomE=3/2kBT.(TisinabsoluteunitsotherwisewewouldhavenegaKvekineKcenergy.)

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Chapter1Background

Groundstateforenergy.WecouldconsiderT=0butthisisinconvenient(impossibletoachieve)andignoresatomicenergy,E=mc2,andchemicalbondenergy.OdenwedefinethegroundstateatSTP.IntheendweareonlyinterestedinchangesinenergyforaneventorprocesssothegroundstateisonlyimportantinsofarasweusethesamegroundstateforallcomponentsofacalculaKon.Foranyspontaneousprocessthetotalenergyisconstant.Thatis,inorderforenergytoincreasewerequireworkorheattobeaddedtothesystem.E=PVforagas,toincreasethepressureatconstantnumberofgasatomsrequiresforceandachangeindistance,compression,thatleadstoareducKoninvolume.Oryouneedtoheatthesystem.

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MoreDefini7ons:InternalEnergy,U.Thermalandrepulsive/airacKveenthalpyofmolecularinteracKon.Ignorescenterofmassenergy.Enthalpy,H.Energyrelatedtospecificbonding/reacKons,andPVwork.SothesumofinternalenergyandPV.Entropy,S.IfyoumixtwoidealgassesatconstantpressurethereisnoenthalpicinteracKonsotheenthalpyofthesystemdoesnotchange.However,thesystemhaschangedsinceitrequiresasignificantamountofworktoseparatethetwoidealgassesandreturntothepurestates.Thischangeisachangeinentropy.TheentropychangeinthiscaseisgivenbyΔS=nkB(φalnφa+φblnφb)andtheenergychangeΔE=-TΔS.

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MoreDefini7ons:

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MoreDefini7ons:

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PhilosophicallyHowThermodynamicsWorks:Weconsiderasubsetoftheuniversecalledthesystemorthecontrolvolume.Thesystemcontainsmanymolecularelementsthatareeachsubjectto3/2kBTkineKcenergy.Therearesomanyoftheseelementaryunitsthattheyarealmostuncountable.Themostimportantstepatthestartofsolvingaprobleminthermodynamicsistocarefullydefinethesystemboundaries.ClosedSystem:Thermaltransferbutnomasstransfer,sayanicecubemeltsintoapuddleandtheicecubeisthesystem.OpenSystem:Massandthermaltransferoccurs,asystemisasecKonofariver.IsolatedSystem:Noheatormasstransfer.Aperfectlyinsulatedboxinwhichamatchislit.

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FreeEnergy:Theenergythatisavailabletodowork.Equilibrium:Asystemisatequilibriumwhenthefreeenergyisataminimum.TwosystemsareatequilibriumwitheachotherwheneverycomponentofthetwosystemshavethesamechemicalpotenKal.(DynamicequilibriumindicatesthattherearealwaysfluctuaKonsaboutanequilibriumcomposiKonduetothermalmoKon.)Thechemicalpoten7alisthechangeinfreeenergywhenoneelement(moleculeormole)ofthatcomponentisintroducedtothesystem.HeatSink/HeatReservoir:Acomponentwithinfinitecapacitytoabsorborgenerateheat(transferofthermalenergy).Theheatsinkisataconstanttemperature.Thatis,itisisothermal

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Howisthermodynamicequilibriumachieved?

ThermodynamicsassumesthatlargepopulaKonofsmallobjects,eachofwhichhasenergy3kBT/2andmovesrandomlybythermaldiffusion,interactwitheachotherandtransferenergy.ThesystemisrandominspaceandKmesothatfluctuaKonsindensityandspeedoccuratrandominspaceandKme.TheserandomthermalfluctuaKonsallowthemoleculestoprobethecondiKonsathigherandlowerconcentraKon,tocomparethefavorabilityofcondiKonsatthesedifferentdensiKesandtofindthestatewiththelowestfreeenergy.ThermodynamicsreliesonrandomfluctuaKonsindensity,andmolecularmoKon.ThefirststageofconsideringrandomfluctuaKonsisthekineKctheoryofgasses

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IdealGasLaw

AgasisviewedasacollecKonofparKcleseachwithmomentump=mvinaboxofsizeL.Thex-componentofmomentumispx=mvx.Oncollisionwithawallthechangeinmomentumis2pxforawallnormaltothexdirecKon.TheparKcleimpactsthewalleveryΔt=2L/vx.TheforceisgivenbyF=Δpx/Δt=Nm<v2x>/LforNparKcles.Wehave<v2x>=<v2>/3forrandommoKons(x,y,andzareindisKnguishable).So,F=Nm<v2>/(3L).P=F/L2=Nm<v2>/(3V).Wehavem<v2>/2=KineKcEnergy=3kBT/2.So,PV=NkBT.

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IdealGasLaw

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F=ma=m(dv/dt)=dp/dtfrombeforeΔpis2pxAndΔt=2L/vxSoF=m<vx^2>/LFor3dandNatomsF=1/3Nm<v2>/LE=3/2kT=½m<v2>Som<v2>=3kTP=F/A=1/3Nm<v2>/(LA)=NkT/V

PhaseBehaviorforSingleComponent,C=1Waterforexample.

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GibbsPhaseRule

F=C–P+2

FfreeparametersCcomponentsPphasesSoforsaturatedwatervaporwehaveonecomponent,twophasesandonefreeparameter.ThatisifTisknownweknowthevaporpressure.Ifweknowthepressureweknowthetemperature.Forsupersaturatedsteamwehaveonecomponent,onephaseandwecanvaryPandTandthesewilldeterminethespecificvolumeordensity,internalenergy,enthalpy,etc.

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GibbsPhaseRule

F=C–P+2FfreeparametersCcomponentsPphases

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IntensiveProper7es:(Notunderlined,V)Pressure,Temperature,FreeEnergy,InternalEnergy,SpecificVolumeThingsthatdonotdependonsystemsize.StateProper7es:TheseareintensiveproperKesthatspecifythestateofthesystem.ThisisFintheGibbsPhaseRule.ExtensiveProper7es:(Underlinedinthebook,V)Volume,Mass,TotalEnergyThingsthataredeterminedbythesystemsize.

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“Quality,q”

Whenamixtureoftwophases(vapor/liquid)existthefrac7onvaporiscalledthe“quality”.TheintrinsicproperKes(M)suchasV,U,H,Scanbecalculatedforatwophasesinglecomponentsystemusingthe“quality”andthevaluesforthesaturatedliquidandvaporphases:M=(1-q)ML+qMVorM=ML+q(ΔM)=ML+q(MV-ML)

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SteamTables

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