07传质与分离工程期末考试题

07传质与分离工程期末考试题,考试作弊将带来严峻后果！

华南理工高校期末考试

2024《传质与分别工程英文》试卷A（含答案）

1.考前请将密封线内填写清晰；

全部答案请直接答在试卷上(或答题纸上)；

．考试形式：开（闭）卷；

SintheairisabsorbedbyNaOHsolutionis(A).

2

B.liquidfilm“controls”;

C.twofilm“controls”.

AB=1.When

C).

>xA;B.yAtd;B.t>tw=td;C.t=tw>td;D.t=tw=td

w

oC,(C)ofreadingisoCB.77oCC.77.01oC;D.77.010oC

B).

WhenthewatercontentofsomematerialisclosetoitsequilibriumwatercontentX*,itsdryingratewill___C_.

B.decrease;

C.beclosetozero;

D.beuncertain

Forthedesorption(stripping)process,when(B)increasesand(A)

A)increases,itisgoodfortheoperation.

D)decreases,itisgoodfortheoperation.

A.dry-bulbtemperatureofair;

B.wet-bulbtemperatureofair;

C.dewpointtemperatureofair;

D.sizeofmaterialtobedried

(9)Forabsorptionprocess,whenthecoefficientskxaandkyaareofthesameorderofmagnitudeandequilibriumconstantmismuchgreaterthan1,(B)issaidtobecontrolling.Inordertoincreasemasstransferrate,itisbettertoincrease(E).

A.gasfilm;

B.liquidfilm;

C.bothgasfilmandliquidfilm;

D.gasphaseflowrate;

E.liquidphaseflowrate;

F.bothgasphaseflowrateandliquidphaseflowrate;

(10)Forabsorptionprocess,ifitistheliquidfilmcontrol,(D)isfeasibletoincreasemasstransferrateofabsorption.

Atodecreasegasflowrate.

Btodecreaseliquidflowrate

Ctoincreasegasflowrate.

Dtoincreaseliquidflowrate.

(11)WhentherefluxratioRincreasesandotherconditionskeepthesame,overflowofvaporVwill(increase);theconcentrationofoverheadproductxDwill(increase);steamconsumptionofreboilerwill(increase),thetheoreticplatenumbersrequiredwill(decrease)forthesamerecoverypercentageofoverheadproduct.

(12)Thefactorstoinfluencemasstransfercoefficientsofgasphaseinclude(T,P,gasflowrate

).

(13)Whensomemoistairispreheatedinapreheater,itshumiditywill(bethesame),itsrelativehumiditywill(decrease),itsenthalpywill(increase),itsdewpointwill(bethesame),itswet-bulbtemperaturewill(increase).

(14)Whentheliquidfloodingatapackedtoweroccurs,(pressuredrop)increasesremarkablyandtheentiretowermayfillwith(liquid)..

(15)MathematicexpressionofFick’slawis(JA=-DdCA/dz).

(16)Therequirementstosatisfyconstantmolaloverfloware(vaporizationheatofdifferentponentswillbethesame,sensibleheatexchangeofliquidandgasphasesontheplatescanbeignored,heatlossofcolumncanbeigored.)

(17)SomewetsolidsaredriedbyairwithtemperaturetandhumidityH.（1)WhenairvelocityincreasesandairtemperaturetandhumidityHkeepconstant,thedryingrateatconstant-rateperiodwill(increase);Ifairvelocityandairconditionskeepunchanged,butthicknessofmaterialsincreases,thecriticalmoisturecontentofwetmaterialXcwill(decrease).

2.(20points)AtaconstantpressureoperationacontinuousdistillationcolumnwithrefluxisusedfortheseparationofabinarymixturewithfeedrateF=1000kmol/handconcentrationxF=0.36(molfractionofmorevolatileponent).Feedissaturatedvapor,therelativevolatilityof

mixtureαis3,indirectsteamheatingisusedatarebolier,andtotalcondenserandbubblepointrefluxatthetopofcolumnareemployedandtherefluxratioRis3.2,respectively.Itisrequiredthattherecoverypercentofmorevolatileponentatthetopofcolumnis92%,andthattheconcentrationofmorevolatileponentatthetopxDis0.9.Calculate:

（1）Operatinglineequationforrectifyingsection;

(2)OverheadproductflowrateD,vaporoverflowVforrectifyingsectionandvaporoverflowV’forstrippingsection,inkmol/h.

(3）Ifthepracticalliquidconcentrationleavingthefirstplate(x1)is0.825,whatisthisplateefficiencyofplate1LME,?

Solution(1)y=0.762x+0.214

(2)DxD/FxF=0.92,D=0.92(1000*0.36)/0.9=368kmol/h

V=(R+1)D=4.2*368=1545.6kmol/h

V’=V-F=1545.6-1000=545.6kmol/h

(3)EmL=(xD-x1)/(xD-x1*)=(0.9-0.825)/(0.9-0.75)=0.5

y1=xD=αx1*/(=0.9=3x1*/

x1*=0.75

3.(20points)Somegasmixturecontainsacetonevaporwith3％(molarfraction)whichisabsorbedbypurewateratacountercurrentoperationabsorber.98%acetoneofoutletgasisremoved.Ratioofliquidtogasflowrateis2andtheequilibriumrelationis=*y1.05xFind

(1）whatistheacetoneconcentrationofoutletwateratthetowerbottom?

(2)whatistheoverallmasstransferunitnumberofgasphase?

(3)iftheinletpositionsofgasandliquidphaseskeepthesameandtheratioofliquidtogasflowrateis1.04,where(inwhatpositionoftower)istheequilibriumofgasandliquidphaseswhenthepackinglayerheightisinfinite?Whatisthemaximumrecoverypercentageofacetone?Solution:(1)x1=V(y1-y2)/L=0.03*0.98/2=0.0147

(2)Noy=(y1-y1)/?ym=0.03*0.98/0.00438=6.71

?ym=/ln=0.00438

(3)since

104

.105.104.105.1='=='=V

LmSV

LmSotheequilibriumwillbereachedatthebottomoftower.Maxremovalefficiencyofacetoneis

1

21maxyyy'-=η

0286.005

.103.005.11*1===yx0297.00286.004.1*121=?=='-xV

Lyy%9903

.00297.0121max=='-=yyyη

4.(15points)Amoistmaterialistobedriedfromwatercontent25%to5%(wetbasis)inanadiabaticdryer(constantenthalpydryingprocess)underatmosphericpressure.Thefeedofmoistmaterialsolidintothedryeris1000kg/h.Aftersomefreshairwithadry-bulbtemperatureof25oCandahumidityof0.013kgwater/kgdryairispreheatedto100oC,itissenttothedryer.Andtheairtemperatureleavingthedryeris65oC.

(1)Whatarethebore-dryair(inkg/h)andthevolumeoffreshairrequiredperunittime(inm3/h)?

(2)Howmuchheatisobtainedbyairwhenitpassesthroughthepreheater(inkJ/h)?Solution:(1)W=Gc(X1-X2)=1000*0.75(1/3-5/95)=210.5kg/h

I1=I2

(1.01+1.88H1)t1+2492H1=(1.01+1.88H2)t2+2492H2

H1=0.013,t1=100,t2=65,H2=0.0268

L=W/(H2-H