化工原理Ⅰ习题及解答.docx

化工原理Ⅰ习题及解答.docx

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化工原理Ⅰ习题及解答

«化工原理

»习题

一、填空题

1.Whenthetemperatureofthegasincreases,theviscositiesofgaseswill（）,whiletheviscositiesofliquidswill（）.

2.Aturbulentflowisconsideredtoconsistofthreezones:

（），（），（）.

3.Twoclassesofmetersareusedtomeasuretheflowrateoffluid.Withtheincreaseofflowrate,thepressuredropof（）and（）willincrease,whilethepressuredropof（）willmaintainconstant.

4.Thegagepressureofanequipmentis100kPa，sotheabsolutepressureofitis（）kPa；Thevaccumpressureofanotherreactoris400mmHg，thentheabsolutepressureofthereactoris（）.（theatmosphericpressureis101.33kPa）

5.Basedonmechanicalconstruction,theimpellerofcentrifugalpumpscanbeclassifiedas（），（），andanenclosedimpeller.　

6.Generally,therearethreeperformancecurvesforacentrifugalpump,whichare（），（），（）.

7.Theoperatingpointofthecentrifugalpumpistheintersectionof（）and（）.

8.（）,（）and（）areexamplesofreciprocatingpumps.

9.Forthepumppriming,thedischargelineofa（）pumpcannotbeclosedwithoutstallingorbreakingthepump,whilethedischargelineof（）pumpscanbecompletelyclosedwithoutdamage.

10.Inordertoavoid（）,thecentrifugalpumpsshouldbefilledwithliquidsbeforepriming（启动）.

11.Inadouble–pipeheatexchanger,theairisheatedbysaturatedsteam.Thetemperatureoftheheat-exchangertubewallisclosetothetemperatureof（）andtheoverallcoefficientisclosetothefilmcoefficientof（）.（saturatedsteamorair）.

12.Manymetersareusedtomeasuretheflowrateoffluid,listthreetypesofmetersusedindustrially:

（）,（）,（）.

13.Ingravitationalsettling,theparticlequicklyreachesaconstantvelocity,whichisthemaximumattainableunderthecircumstancesandwhichiscalled（）.

14.Ifthevelocityofthedust-ladenairisincreased,theefficiencyofthecyclonewill（）,thepressuredropwill（）.

15.Intheory,thecapacityofthesettlingchamberisinrelationto（）,（）,andhasnothingtodowith（）.

16.Bythefiltrationoperations-basicequation.Listthemeasurementsofincreasingthecapacityofthefilters（atleastthreeitems）:

（），（），（）.

17.Whencurrentsinafluidresultfrombuoyancyforcescreatedbydensitydifferences,andthedensitydifferencesarecausedbytemperaturegradientsinthefluid,theactioniscalled（）.Whenthecurrentsareduetoapump,theflowiscalled（）.

18.Avapormaycondenseonacoldsurfaceinoneoftwoways,whicharewelldescribedbytheterms（）and（）.

19.Heatflowunaccompaniedbyanyobservablemotionofmatteriscalled（）,while（）canrefertotheflowofheatassociatedwiththemovementofafluid,（）isatermgiventothetransferofenergythroughspacebyelectromagneticwaves.

20.Atsteadystate,theheatflowratethroughacylinderis（）,theheatfluxis（）.（aconstant,notaconstant）

21.Theheattransferredaccompanyingcondensationis（）,andtheheattransferfromtheriseorfallinthetemperatureofafluidwithoutphasechangeis（）.

二、判断题

1.Fluidfrictionisinterconvertible（可互相转换的）withthemechanicalenergyquantities.（）

2.Thefluidisflowinginapipe.Ifitisturbulent,thevelocitydistributionwith

respecttotheradiusisaparabola（抛物线）.（）

3.Absolutepressuresarealwayspositive,butgagepressurecanbeeitherpositive（正的）ornegative（负的）.（）

4.Thefluidstreamcanbeconsideredastwoparts,theboundarylayerandtheremainingfluid.

5.Whenenerthevelocityofafluidischanged,formfrictionwillbegenerated.（）

6.Thethinnertheviscoussublayeris,thelowerthefrictionlossis.（）

7.Gasviscositiesaregenerallygreaterthanliquidviscosities.（）

8.Theflowwithoutlateralmixingislaminarflow.（）

9.Thethinnertheviscoussublayeris,thelowerthefrictionlossis.（）

10.Thedischargelineofacentrifugalpumpcanbecompletelyclosedwithoutdamage.（）

11.Anenclosedimpellerhasasolidspassingcapability.（）

12.Plungeranddiaphragmpumpsarewidelyusedas“meteringpump”.（）

13.Positive-displacementmachines,ingeneral,handlesmallerquantitiesoffluidsathigherdischargepressuresthandocentrifugalmachines.（）

14.Thevoluteistherotatingpartthatconvertsdriverenergyintothekineticenergy.（）

15.Inheatconvection,heatflowisassociatedwiththeflowofafluid.（）

16.Asforafluid,thefilmcoefficienthwithphasechangeisgreaterthanthatwithoutphasechange.（）

17.Gaseshavethesmallestthermalconductivities,soporousmaterialsbyentrappingaircanbeusedtoeliminateconvection.（）

18.Formostliquids,thethermalconductivitykishigherthanthatforsolids.（）

19.Inordertoobtainalargerfilmcoefficientontheshell-sidefluid,multipassheatexchangersshouldbeused.（）

20.Fourier’lawisthebasiclawofconvection.（）

21.Whenquenching（急冷）ahotfluidfromachemicalreactortostopfurtherreactions,parallelflowshouldbeused.（）

22.Inordertoobtainalargerfilmcoefficientonthetube-sidefluid,multipassheatexchangersshouldbeused.（）

23.Inconstant-pressurefiltration,boththepressuredropandtheflowrateallowedareheldconstant.（）

24.Bothhydrocloneandcycloneareusedtoseparatesolidsfromgases.（）

25.Inthegravitysedimentationprocess,iftheresidencetimeofasolidisgreaterthanitssedimentationtime,thesolidwillbeseparatedfromthegases.（）

26.Thelargertheparticlediameterandtheparticledensityare,thesamllertheterminalvelocityis.（）

27.Alarge-diametercyclonehasamuchlowerseparationfactoratthesamevelocity.（）

28.Thecakeresistanceincreaseswithtimeinbothconstant-ratefiltrationandconstant-pressurefiltration.（）

29.Inconstant-pressurefiltration,boththecakeresistanceandthepressuredropareheldconstant.（）

30.Inthesettleingchamber,thegasstreamshouldbelaminar,andReofwhichislessthan2100.（）

三、选择题

1.Waterwithρ=1000kg/m3,μ=0.001Pa.sflowingatanaveragevelocityof1m/sina200mmpipe,（）

ATheflowislaminar;BTheflowisturbulent;

CTheflowistransition;DTheflowisuncertain.

2.Incompressiblefluidsflowinahorizontalpipe（theflowissteady）,theenergyconsumedbyfrictioncomesfrom（）.

AkineticenergyBpotentialenergy

CpressureenergyDuncertain

3.Incompletelyturbulentflow（Re>106）throughasteelpipe,thefanningfrictionfactorisrelatedto（）.

AReonlyBReandk/DCk/DDReandk

4.Foradouble-pipeexchanger,thedimensionofinnertubeisΦ19×2.5mm,andthedimensionofoutertubeisΦ38×3mm,theequivalentdiameteroftheannularspaceDeqis（）.

A13mmB19mmC24mmD18mm

5.TheIntrinsicdistinctionbetweenthelaminarflowandtheturbulentflowis（）.

Avelocityofturbulentflowisgreaterthanthatoflaminarflow

BReoflaminarflowislessthanthatofturbulent

Clargercross-sectionalareaisturbulent,whilesamllercross-sectionalareaislaminar.

Dlaminarflowwithoutlateralmixing,whileturbulenthaslateralmixing.

6.Forarotameter,whentheflowrateofwateris1m3/h,thepressuredropthroughitis20Pa.Iftheflowratedoubles,thepressuredropthroughtherotameterwillbe（）.

A40PaB20PaC10PaD60Pa

7.Fluidsflowthroughtwoparallelpipes,flowsinbothpipesarelaminar.IfthelengthofthetwopipesL1=L2,innerdiameterd1=2d2，thevolumetricflowrateq2/q1willbe（）.

A1/2B1/4C1/8D1/16

8.Fluidflowsthroughastraightpipe,whentheflowiscompletelyturbulent,withtheincreaseofRethefrictioncoefficientλwill（）.

AincreaseBdecreaseCnearlyremainaconstantDuncertain

9.Ifthereadingsofavacuumgauge（真空表）atthesuctionconnectionofthecentrifugalpumpis700mmHg,andtheatmosphericpressure  is101.33kPa，thevaporpressureof42℃wateris8.2kPa,cavitation（）.

AmusthappenBisimpossible

CperhapshappenDuncertain

10.Twopumpsoperating（）willbemoreeffectivewithalowresistancepipesystem.

AinseriesBinparallel

CintheparallelpipesystemDinbranchingpipesystem

11.Inordertoavoid（）,thecentrifugalpumpshouldbefilledwithwaterbeforepumppriming.

AairboundBcavitation

CbeingbrokenDpipeblock（堵塞）

12.Efficincyofacentrifugalpumpwill（）withtheincreaseoftheflowrate,

AincreaseBdecrease

Cincreaseuntilreachingamaximumvalue,thendecrease

Ddecreaseuntilreachingaminimumvalue,thenincrease

13.（）cannotchangetheoperatingpointofthecentrifugalpump.

AchangingtheimpellerspeedBchangingtheimpellerdiameter

CoperatinginparallelDchangingthesuctionlift

14.Aflatwallisconstructedoftwolayers.Thethicknessesandareasofthetwolayersarethesame.Theaveragethermalconductivitiesarek1andk2respectivelyandthetemperaturedifferencesare

and

.Theheattransferissteady.Ifk1>k2，（）

A

>

B

<

C

=

Duncertain

15.Waterisflowinginapipe（Re>104）atanaveragevelocityV.Itsfilmcoefficentish1.Iftheaveragevelocityisincreasedto3V,assumingotherconditionsarenotchanged,itsfilmcoefficenth2=（）

A3h1B0.33h1C2.41h1D1.73h1

16.Inacondenser,acoldfluidisheatedbysaturatedstreamfrom15℃to40℃.Iftheflowiscountercurrent,theLMTD=

Iftheflowisparallel,theLMTD=

.（）

A

=

B

>

C

<

Duncertain

17.Thehotfluidiscooledby20℃waterfrom85℃to40℃.Ifthetemperatureoftheleavingwaterisrequirednottobehigherthan40℃,（）mustbeused.

AcountercurrentflowBbaffleflow（折流）

CparallelflowDcrossflow

18.Airisheatedbysaturatedsteaminashell-and-tubeexchanger,（）isthemosteconomicmethodtoincreasethe