ChemicalEngineeringThermodynamics

ClassmeetsMTWRfrom12:20to1:15Baldwin755HelpsessionsW3-5405ERC

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

1

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.

2

CourseLogis7cs

ChemicalEngineeringThermodynamics

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

3

CourseLogis7cs

HomeworkGroupOp7onsA)  Formyourowngroup

Sendanemailtochethermouc@gmail.comwithlistofhomeworkgroupmembersand7methatyoumeet.Putinsubjectofemail:HOMEWORKGROUPMeetsMondayat6pm.

B)NeedagroupSendanemailreques7ngagroupanda7methatyouareavailabletomeet.Putinsubject:REQUESTGROUPMondayat6pm.

C)Prefertoworkonyourown(notrecommended).Sendanemailtochethermouc@gmail.comSubject:WORKONOWN

PleasedothisbyTuesdayJanuary11.FirstHomeworkisdueWednesdayJanuary12atmidnight.

4

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

5

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

6

OutlineofClass:

7

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

8

Chapter1Background

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

9

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

10

MoreDefini7ons:

11

MoreDefini7ons:

12

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

13

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

14

Howisthermodynamicequilibriumachieved?

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

15

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.

16

IdealGasLaw

17

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.

18F=C–P+2

GibbsPhaseRule

F=C–P+2

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

19

GibbsPhaseRule

F=C–P+2FfreeparametersCcomponentsPphases

20

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

21

22

23

24

“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)

25

26

SteamTables

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

QuesKon4

42

43

QuesKon6

44

QuesKon10

45

46

47

48

49

50

51

52

53

54

55

56

57

58