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Chapter6.Fick’sfirstlawofdiffusionRelationsbetweendiffusivitiesChapter6.Fick’sfirstlawofEquimolaldiffusionForequimolaldiffusioningases,thenetvolumetricandmolarflowsarezeroEquimolaldiffusionForequimolTheconcentrationgradientforAislinearinthefilm,andthegradientforBhasthesamemagnitudebuttheoppositesignTheconcentrationgradientone-waydiffusiononlycomponentAistransferredthroughtheinterfaceorone-waydiffusiononlycomponen6.2PredictionofDiffusivitiesDiffusivitiesarebestestimatedbyexperimentalmeasurementstheyarealsoestimatedfrompublishedcorrelations6.2PredictionofDiffusivitieDiffusioningasesAsimpletheoryforgasesshowsthatDisproportionaltotheproductoftheaveragemolecularvelocityandthemeanfreepath.DiffusioningasesAsimpletheThemeanfreepathforidealgasesvariesinverselywithpressureandincreaseswithT1.0ThemeanmolecularvelocitydependsonT0.5Dforidealgases

varieswithT1.5andvariesinverselywithpressureThemeanfreepathforidealgTheChapman-EnskogequationforbinarydiffusionTheChapman-EnskogequationfDiffusioninliquidsThediffusivitiesinliquidsaregenerally4to5ordersofmagnitudesmallerthaningases,butthefluxesforagivenmolefractiongradientinliquidorgasmaybenearlythesamebecauseofthemuchgreaterliquiddensities.DiffusioninliquidsThediffusTwo-FilmTheoryInthetwo-filmtheory,equilibriumisassumedattheinterface,andtheresistancestomasstransferinthetwophasesareaddedtogetanoverallresistance,justasisdoneforheattransfer.Thereciprocaloftheoverallresistanceisanoverallcoefficient.Two-FilmTheoryInthetwo-filmChapter7.7.1EquilibriumRelationsEquilibriumdatacanbeshownintables,equations,orgraphs.Chapter7.7.1EquilibriumRela7.1.1gas-liquidequilibriumHenry'slawTheequilibriumrelationbetweenpartialpressureinthegasphaseandxATheequilibriumrelationbetweenmolefractioninthegasphaseandmolefractionintheliquid

xA7.1.1gas-liquidequilibriumHe7.1.2Vapor-LiquidEquilibriumRelationsRaoult'sLaw7.1.2Vapor-LiquidEquilibriumEquilibriumrelationAtlowpressurethevaporofmixtureapproachesidealbehaviorandfollowstheidealgaslaw.Raoult’slawappliestoeachcomponentoverentireconcentrationrange,suchmixturesarecalledideal.EquilibriumrelationAtlowpreRelativeVolatilityofVapor–LiquidSystemsDefinitionRelativeVolatilityofVapor–LForaseparationprocessinwhichα=1,thecompositionsofcomponentAwouldbethesameinbothphases,separationisnotpossiblewhenthisoccurssincethedrivingforceformasstransferiszero.Whenthevalueofαisabove1,aseparationispossible.Thevalueofαmaychangeasconcentrationandtotalpressurechange.

ForaseparationprocessinBoiling-PointDiagramsandx-yPlotstheboiling-pointdiagramx-ydiagramBoiling-PointDiagramsandx-ymaximumboilingazeotropeminimumboilingazeotropemaximumboilingazeotrope7.2.Equilibrium-StageOperationsrectifyingsectionStrippingReboilerandvaporstreamRefluxTotalcondenserandpartialcondenserVaporenrichedinboilerLiquidenrichedinheavierboiler7.2.Equilibrium-StageOperatiMaterialbalancesandoperatinglineTotalmaterialbalanceMaterialbalanceoncomponentOperatinglineMaterialbalancesandoperatinIdealcontactstagesInanidealstage,theVphaseleavingthestageisinequilibriumwiththeLphaseleavingthesamestage.IdealcontactstagesInanideaDeterminingthenumberofidealstagesDeterminingthenumberofideaAbsorptionfactormethodforcalculatingthenumberofidealstagesAbsorptionfactormethodforcWhentheoperatingandequilibriumlinesarebothstraightoveragivenconcentrationrangexa

toxb,thenumberofidealstagescanbecalculateddirectlyWhentheoperatingandequilib化工原理课件(7.2-22)(7.2-24)

(7.2-22)(7.2-24)Whentheoperatinglineandtheequilibriumlineareparallel,WhentheoperatinglineandthChapter88.1PrinciplesofAbsorptionChapter88.1PrinciplesofAbs8.1.1MaterialbalancesTotalmaterialbalanceMaterialbalanceoncomponentOperatinglines8.1.1MaterialbalancesTotalmInmanyinstancesmoreconvenientexpressionscanbederivedforevaluatingtheabsorptionprocessifasolute-freebasisisusedforcompositionsratherthanmolefractions.Inmanyinstancesmoreconveni8.1.2LimitingandOptimumGas-liquidRatioLimitingliquid-gasratio8.1.2LimitingandOptimumGasIngeneral,theliquidratefortheabsorbershouldbebetween1.1and2.0timestheminimumrate,unlesstheliquidistobediscardedandnotregeneratedIngeneral,theliquidratefo8.1.3.RateofabsorptioninpackedtowersIndividualcoefficientandoverallcoefficient8.1.3.Rateofabsorptionincontrollingresistancegasphaseiscontrollingliquidphaseiscontrollingcontrollingresistance8.2Calculationoftowerheight8.2Calculationoftowerheigh8.2.2

Numberoftransferunitsandheightofatransferunitheightofatransferunit

HOy8.2.2Numberoftransferunitsnumberoftransferunits

NOy.numberoftransferunitsNOy.Forstraightoperatingandequilibriumlines,thenumberoftransferunitsisthechangeinconcentrationdividedbythelogarithmicmeandrivingforce:ForstraightoperatingandequAdifferentformsoftheequationsforabsorptionwithNOyAdifferentformsoftheequat8.4Desorptionorstripping8.4DesorptionorstrippingChapter99.1FlashDistillationFlashdistillationconsistsofvaporizingadefinitefractionoftheliquidinsuchawaythattheevolvedvaporisinequilibriumwiththeresidualliquid,separatingthevaporfromtheliquid,andcondensingthevapor.Chapter99.1FlashDistillatioFlashdistillationisusedmostforseparatingcomponentsthatboilatwidelydifferenttemperatures.Flashdistillationisusedmos9.2.SimpleBatchorDifferentialDistillationIndifferentialdistillation,liquidisfirstchargedtoaheatedkettle.Theliquidchargeisboiledslowlyandthevaporsarewithdrawnasrapidlyastheyformtoacondenser,wherethecondensedvaporiscollected.9.2.SimpleBatchorDifferent9.4ContinuousDistillationwithReflux9.4.1ActiononanIdealPlatePartialvaporizationandpartialcondensation9.4ContinuousDistillationwi9.4.2CombinationRectificationandStripping9.4.2CombinationRectificatio9.4.3MaterialBalancesinPlateColumnsOverallmaterialbalanceandmaterialbalanceforthecomponent9.4.3MaterialBalancesinPlaOperatinglinestheoperatinglineforrectifyingsectionistheoperatinglineforrectifyingsectionisOperatinglinestheoperatingl9.4.4NumberofIdealPlates;McCabe-ThieleMethodConstantmolaloverflowThisresultsfromnearlyequalmolarlatentheatsofvaporization,heatlossandsensibleheatwereneglected,9.4.4NumberofIdealPlates;RefluxratioRefluxratioCondenserandtopplateTotalcondensercondensesallvaporfromthecolumnandsuppliesbothrefluxandproduct.Whenapartialcondenserisused,theliquidrefluxdoesnothavethesamecompositionastheoverheadproduct;thatis,xc

≠xD.ThepartialcondenseristhereforeequivalenttoanadditionaltheoreticalstageCondenserandtopplateTotalcBottomplateandreboilerThevaporleavingthereboilerisinequilibriumwiththeliquidleavingasbottomproduct.BottomplateandreboilerThevConditionoffeedEffectsofdifferentconditionsoffeedondistillationprocessConditionoffeedEffectsofdiThenqhasthefollowingnumericallimitsforthevariousconditions:Coldfeed,q>1Feedatbubblepoint(saturatedliquid),q=1Feedpartiallyvapor,0<q<1Feedatdewpoint(saturatedvapor),q=0Feedsuperheatedvaporq<0ThenqhasthefollowingnumerFeedlineFeedlineConstructionofoperatinglinesConstructionofoperatinglineFeedplatelocationTheoptimumpositionoffeedplate,thetrianglerepresentingthefeedplatestraddlestheintersectionoftheoperatinglines.FeedplatelocationTheoptimumMinimumnumberofplatesTotalrefluxandminimumnumberofplatesMinimumnumberofplatesTotalMinimumrefluxAtaminimumvalue,calledtheminimumrefluxratio,thenumberofplatesbecomesinfinite.ConcavedownwardConcaveupwardMinimumrefluxAtaminimumvalOptimumrefluxratioItisaminimumatadefiniterefluxrationotmuchgreaterthantheminimumreflux.Thisisthepointofmosteconomicaloperation,andthisratioiscalledtheoptimumrefluxratio.OptimumrefluxratioItisamiInordinarysituations,theminimumonthetotalcostcurvewillgenerallyoccuratanoperatingrefluxratiooffrom1.1to1.5timestheminimum.Inordinarysituations,themiNumberofidealplatesatoperatingrefluxNumberofidealplatesatoper9.4.5SpecialCasesforRectificationUsingMcCabe–ThieleMethodStrippingdistillationEnrichingdistillationRectificationwithdirectsteaminjectionMultiplefeedsandsidestreams9.4.5SpecialCasesforRectifAzeotropicDistillationDifferencesbetweentheazeotropicdistillationandextractivedistillationAzeotropicDistillationDiffere9.6PlateEfficienciesOverallplateefficiencyMurphreeefficiency9.6PlateEfficienciesOverallChapter11.11.1.1.PurposesofDrying11.1.2.GeneralMethodsofDrying11.2.EQUIPMENTFORDRYING11.2.1.TrayDryer11.2.2.Vacuum-ShelfIndirectDryers11.2.3.ContinuousTunnelDryers11.2.3.RotaryDryers11.2.4.DrumDryers11.2.5.SprayDryers11.2.6.FlashDryerChapter11.11.1.1.PurposesofVAPORPRESSUREOFWATERANDHUMIDITYHumidityandHumidityChartVAPORPRESSUREOFWATERANDHU1.Definitionofhumidity1.Definitionofhumidity2.Percentagehumidity2.Percentagehumidity3.PercentagerelativehumidityThepercentagehumidityisnearlyequaltotherelativehumidityifthepartialpressureofvaporinairisverylow3.Percentagerelativehumidit4.Dewpointofanair–watervapormixtureThetemperatureatwhichagivenmixtureofairandwatervaporwouldbesaturatediscalledthedew-pointtemperature4.Dewpointofanair–waterv5.Humidheatofanair–watervapormixture(11.3-6)

5.Humidheatofanair–water6.Humidvolumeofanair–watervapormixture6.Humidvolumeofanair–wate7.Totalenthalpyofanair–watervapormixture7.Totalenthalpyofanair–wa8.Humiditychartofair–watervapormixtures8.Humiditychartofair–waterAdiabaticSaturationTemperaturesThismeansthatthetotalenthalpyoftheenteringgasmixture=enthalpyoftheleavinggasmixture.AdiabaticSaturationTemperatuWetBulbTemperatureThismeansthattheadiabaticsaturationtemperatureisapproximatelyequaltowetbulbtemperature.

WetBulbTemperatureThismeansEQUILIBRIUMMOISTURECONTENTOFMATERIALSAfterexposureofthesolidsufficientlylongforequilibriumtobereached,thesolidwillattainadefinitemoisturecontent.EQUILIBRIUMMOISTURECONTENTOEffectoftemperatureOften,formoderatetemperatureranges,theequilibriummoisturecontentwillbeassumedconstantwhenexperimentaldataarenotavailableatdifferenttemperatures.EffectoftemperatureOften,foBoundandUnboundWaterinSolidsBoundwaterBoundandUnboundWaterinSolFreeandEquilibriumMoistureofaSubstanceFreemoisturecontentinasampleisthemoistureabovetheequilibriummoisturecontent.

FreeandEquilibriumMoistureFreeandEquilibriumMoistureofaSubstanceFreemoisturecontentinasampleisthemoistureabovetheequilibriummoisturecontent.

Freemoisturecanberemovedbydryingunderthegivenpercentrelativehumidity.FreemoisturecontentequilibriummoisturecontentFreeandEquilibriumMoistureRATE-OF-DRYINGCURVES11.5.2.RateofDryingCurvesforConstant-DryingConditionsRATE-OF-DRYINGCURVES11.5.2.RDryingintheConstant-RatePeriodIntheconstant-ratedryingperiod,thesurfaceofthesolidisinitiallyverywetandacontinuousfilmofwaterexistsonthedryingsurface.Thiswaterisentirelyunboundwateranditactsasifthesolidwerenotpresent.DryingintheConstant-RatePeTherateofevaporationunderthegivenairconditionsisindependentofthesolidandisessentiallythesameastheratefromafreeliquidsurface.TherateofevaporationunderThesurfacetemperatureisapproximatelythesameasthewetbulbtemperatureThesurfacetemperatureisappDryingintheFalling-RatePeriodDryingintheFalling-RatePer3.EffectofshrinkageItisdesirabletodrywithmoistair.todecreasethetemperatureofairThisdecreasestherateofdryingsothattheeffectsofshrinkageonwarpingorhardeningatthesurfacearegreatlyreduced.3.EffectofshrinkageItisCALCULATIONMETHODSFORCONSTANT-RATEDRYINGPERIODCALCULATIONMETHODSFORCONSTADryingtimeforconstantrateperiodDryingtimeforconstantrateEffectofProcessVariablesonConstant-RatePeriod1.Effectofairvelocity2.Effectofgashumidity3.Effectofgastemperature4.EffectofthicknessofsolidbeingdriedEffectofProcessVariablesonCALCULATIONMETHODSFORFALLING-RATEDRYINGPERIODCALCULATIONMETHODSFORFALLINRearrangingThedryingrateinthefalling-rateperiodiscontrolledbytherateofinternalmovementoftheliquidbyliquiddiffusionorbycapillarymovement.RearrangingThedryingrateinMaterialandHeatBalancesforContinuousDryersMaterialandHeatBalancesfor化工原理课件Awetmaterialcontainingmoisturecontentof50wt%onawetbasisisdriedto6wt%inacontinuouscountercurrentdrier.Themoistairleavesthedrieratt2=38℃andH2=0.034kgH2O/kgdryairandpartofitrecirculatedandmixedwiththefreshairhavingthetemperaturet0=25℃,humidityH0=0.005kgH2O/kgdryairbeforeenteringapreheater.Theratioofrecirculateddryairtothemixeddryairis0.8.Calculatetheamountoffreshairandrateofheattransferinthepreheaterwhenthewetmaterialisfedtothedryeratrateof1000kg/honassumptionthatthedryeroperatesundertheconditionofisenthalpicprocess.AwetmaterialcontainingChapter6.Fick’sfirstlawofdiffusionRelationsbetweendiffusivitiesChapter6.Fick’sfirstlawofEquimolaldiffusionForequimolaldiffusioningases,thenetvolumetricandmolarflowsarezeroEquimolaldiffusionForequimolTheconcentrationgradientforAislinearinthefilm,andthegradientforBhasthesamemagnitudebuttheoppositesignTheconcentrationgradientone-waydiffusiononlycomponentAistransferredthroughtheinterfaceorone-waydiffusiononlycomponen6.2PredictionofDiffusivitiesDiffusivitiesarebestestimatedbyexperimentalmeasurementstheyarealsoestimatedfrompublishedcorrelations6.2PredictionofDiffusivitieDiffusioningasesAsimpletheoryforgasesshowsthatDisproportionaltotheproductoftheaveragemolecularvelocityandthemeanfreepath.DiffusioningasesAsimpletheThemeanfreepathforidealgasesvariesinverselywithpressureandincreaseswithT1.0ThemeanmolecularvelocitydependsonT0.5Dforidealgases

varieswithT1.5andvariesinverselywithpressureThemeanfreepathforidealgTheChapman-EnskogequationforbinarydiffusionTheChapman-EnskogequationfDiffusioninliquidsThediffusivitiesinliquidsaregenerally4to5ordersofmagnitudesmallerthaningases,butthefluxesforagivenmolefractiongradientinliquidorgasmaybenearlythesamebecauseofthemuchgreaterliquiddensities.DiffusioninliquidsThediffusTwo-FilmTheoryInthetwo-filmtheory,equilibriumisassumedattheinterface,andtheresistancestomasstransferinthetwophasesareaddedtogetanoverallresistance,justasisdoneforheattransfer.Thereciprocaloftheoverallresistanceisanoverallcoefficient.Two-FilmTheoryInthetwo-filmChapter7.7.1EquilibriumRelationsEquilibriumdatacanbeshownintables,equations,orgraphs.Chapter7.7.1EquilibriumRela7.1.1gas-liquidequilibriumHenry'slawTheequilibriumrelationbetweenpartialpressureinthegasphaseandxATheequilibriumrelationbetweenmolefractioninthegasphaseandmolefractionintheliquid

xA7.1.1gas-liquidequilibriumHe7.1.2Vapor-LiquidEquilibriumRelationsRaoult'sLaw7.1.2Vapor-LiquidEquilibriumEquilibriumrelationAtlowpressurethevaporofmixtureapproachesidealbehaviorandfollowstheidealgaslaw.Raoult’slawappliestoeachcomponentoverentireconcentrationrange,suchmixturesarecalledideal.EquilibriumrelationAtlowpreRelativeVolatilityofVapor–LiquidSystemsDefinitionRelativeVolatilityofVapor–LForaseparationprocessinwhichα=1,thecompositionsofcomponentAwouldbethesameinbothphases,separationisnotpossiblewhenthisoccurssincethedrivingforceformasstransferiszero.Whenthevalueofαisabove1,aseparationispossible.Thevalueofαmaychangeasconcentrationandtotalpressurechange.

ForaseparationprocessinBoiling-PointDiagramsandx-yPlotstheboiling-pointdiagramx-ydiagramBoiling-PointDiagramsandx-ymaximumboilingazeotropeminimumboilingazeotropemaximumboilingazeotrope7.2.Equilibrium-StageOperationsrectifyingsectionStrippingReboilerandvaporstreamRefluxTotalcondenserandpartialcondenserVaporenrichedinboilerLiquidenrichedinheavierboiler7.2.Equilibrium-StageOperatiMaterialbalancesandoperatinglineTotalmaterialbalanceMaterialbalanceoncomponentOperatinglineMaterialbalancesandoperatinIdealcontactstagesInanidealstage,theVphaseleavingthestageisinequilibriumwiththeLphaseleavingthesamestage.IdealcontactstagesInanideaDeterminingthenumberofidealstagesDeterminingthenumberofideaAbsorptionfactormethodforcalculatingthenumberofidealstagesAbsorptionfactormethodforcWhentheoperatingandequilibriumlinesarebothstraightoveragivenconcentrationrangexa

toxb,thenumberofidealstagescanbecalculateddirectlyWhentheoperatingandequilib化工原理课件(7.2-22)(7.2-24)

(7.2-22)(7.2-24)Whentheoperatinglineandtheequilibriumlineareparallel,WhentheoperatinglineandthChapter88.1PrinciplesofAbsorptionChapter88.1PrinciplesofAbs8.1.1MaterialbalancesTotalmaterialbalanceMaterialbalanceoncomponentOperatinglines8.1.1MaterialbalancesTotalmInmanyinstancesmoreconvenientexpressionscanbederivedforevaluatingtheabsorptionprocessifasolute-freebasisisusedforcompositionsratherthanmolefractions.Inmanyinstancesmoreconveni8.1.2LimitingandOptimumGas-liquidRatioLimitingliquid-gasratio8.1.2LimitingandOptimumGasIngeneral,theliquidratefortheabsorbershouldbebetween1.1and2.0timestheminimumrate,unlesstheliquidistobediscardedandnotregeneratedIngeneral,theliquidratefo8.1.3.RateofabsorptioninpackedtowersIndividualcoefficientandoverallcoefficient8.1.3.Rateofabsorptionincontrollingresistancegasphaseiscontrollingliquidphaseiscontrollingcontrollingresistance8.2Calculationoftowerheight8.2Calculationoftowerheigh8.2.2

Numberoftransferunitsandheightofatransferunitheightofatransferunit

HOy8.2.2Numberoftransferunitsnumberoftransferunits

NOy.numberoftransferunitsNOy.Forstraightoperatingandequilibriumlines,thenumberoftransferunitsisthechangeinconcentrationdividedbythelogarithmicmeandrivingforce:ForstraightoperatingandequAdifferentformsoftheequationsforabsorptionwithNOyAdifferentformsoftheequat8.4Desorptionorstripping8.4DesorptionorstrippingChapter99.1FlashDistillationFlashdistillationconsistsofvaporizingadefinitefractionoftheliquidinsuchawaythattheevolvedvaporisinequilibriumwiththeresidualliquid,separatingthevaporfromtheliquid,andcondensingthevapor.Chapter99.1FlashDistillatioFlashdistillationisusedmostforseparatingcomponentsthatboilatwidelydifferenttemperatures.Flashdistillationisusedmos9.2.SimpleBatchorDifferentialDistillationIndifferentialdistillation,liquidisfirstchargedtoaheatedkettle.Theliquidchargeisboiledslowlyandthevaporsarewithdrawnasrapidlyastheyformtoacondenser,wherethecondensedvaporiscollected.9.2.SimpleBatchorDifferent9.4ContinuousDistillationwithReflux9.4.1ActiononanIdealPlatePartialvaporizationandpartialcondensation9.4ContinuousDistillationwi9.4.2CombinationRectificationandStripping9.4.2CombinationRectificatio9.4.3MaterialBalancesinPlateColumnsOverallmaterialbalanceandmaterialbalanceforthecomponent9.4.3MaterialBalancesinPlaOperatinglinestheoperatinglineforrectifyingsectionistheoperatinglineforrectifyingsectionisOperatinglinestheoperatingl9.4.4NumberofIdealPlates;McCabe-ThieleMethodConstantmolaloverflowThisresultsfromnearlyequalmolarlatentheatsofvaporization,heatlossandsensibleheatwereneglected,9.4.4NumberofIdealPlates;RefluxratioRefluxratioCondenserandtopplateTotalcondensercondensesallvaporfromthecolumnandsuppliesbothrefluxandproduct.Whenapartialcondenserisused,theliquidrefluxdoesnothavethesamecompositionastheoverheadproduct;thatis,xc

≠xD.ThepartialcondenseristhereforeequivalenttoanadditionaltheoreticalstageCondenserandtopplateTotalcBottomplateandreboilerThevaporleavingthereboilerisinequilibriumwiththeliquidleavingasbottomproduct.BottomplateandreboilerThevConditionoffeedEffectsofdifferentconditionsoffeedondistillationprocessConditionoffeedEffectsofdiThenqhasthefollowingnumericallimitsforthevariousconditions:Coldfeed,q>1Feedatbubblepoint(saturatedliquid),q=1Feedpartiallyvapor,0<q<1Feedatdewpoint(saturatedvapor),q=0Feedsuperheatedvaporq<0ThenqhasthefollowingnumerFeedlineFeedlineConstructionofoperatinglinesConstructionofoperatinglineFeedplatelocationTheoptimumpositionoffeedplate,thetrianglerepresentingthefeedplatestraddlestheintersectionoftheoperatinglines.FeedplatelocationTheoptimumMinimumnumberofplatesTotalrefluxandminimumnumberofplatesMinimumnumberofplatesTotalMinimumrefluxAtaminimumvalue,calledtheminimumrefluxratio,thenumberofplatesbecomesinfinite.ConcavedownwardConcaveupwardMinimumrefluxAtaminimumvalOptimumrefluxratioItisaminimumatadefiniterefluxrationotmuchgreaterthantheminimumreflux.Thisisthepointofmosteconomicaloperation,andthisratioiscalledtheoptimumrefluxratio.OptimumrefluxratioItisamiInordinarysituations,theminimumonthetotalcostcurvewillgenerallyoccuratanoperatingrefluxratiooffrom1.1to1.5timestheminimum.Inordinarysituations,themiNumberofidealplatesatoperatingrefluxNumberofidealplatesatoper9.4.5SpecialCasesforRectificationUsingMcCabe–ThieleMethodStrippingdistillationEnrichingdistillationRectificationwithdirectsteaminjectionMultiplefeedsandsidestreams9.4.5SpecialCasesforRectifAzeotropicDistillationDifferencesbetweentheazeotropicdistillationandextractivedistillationAzeotropicDistillationDiffere9.6PlateEfficienciesOverallplateefficiencyMurphreeefficiency9.6PlateEfficienciesOverallChapter11.11.1.1.PurposesofDrying11.1.2.GeneralMethodsofDrying11.2.EQUIPMENTFORDRYING11.2.1.TrayDryer11.2.2.Vacuum-ShelfIndirectDryers11.2.3.ContinuousTunnelDryers11.2.3.RotaryDryers11.2.4.DrumDryers11.2.5.SprayDryers11.2.6.FlashDryerChapter11.11.1.1.PurposesofVAPORPRESSUREOFWATERANDHUMIDITYHumidityandHumidityChartVAPORPRESSUREOFWATERANDHU1.Definitionofhumidity1.Definitionofhumidity2.Percentagehumidity2.Percentagehumidity3.PercentagerelativehumidityThepercentagehumidityisnearlyequaltotherelativehumidityifthepartialpressureofvaporinairisverylow3.Percentagerelativehumidit4.Dewpointofanair–watervapormixtureThetemperatureatwhichagivenmixtureofairandwatervaporwouldbesaturatediscalledthedew-pointtemperature4.Dewpointofanair–waterv5.Humidheatofanair–watervapormixture(11.3-6)

5.Humidheatofanair–water6.Humidvolumeofanair–watervapormixture6.Humidvolumeofanair–wate7.Totalenthalpyofanair–watervapormixture7.Totalenthalpyofanair–wa8.Humiditychartofair–watervapormixtures8.Humiditychartofair–waterAdiabaticSaturationTemperaturesThismeansthatthetotalenthalpyoftheenteringgasmixture=enthalpyoftheleavinggasmixture.AdiabaticSaturationTemperatuWetBulbTemperatureThismeansthattheadiabaticsaturationtemperatureisapproximatelyequaltowetbulbtemperature.

WetBulbTemperatureThismeansEQUILIBRIUMMOISTURECONTENTOFMATERIALSAfterexposureofthesolidsufficientlylongforequilibriumtobereached,thesolidwillattainadefinitemoisturecontent.EQUILIBRIUMMOISTURECONTENTOEffectoftemperatureOften,formoderatetemperatureranges,theequilibriummoisturecontentwillbeassumedconstantwhenexperimentaldataarenotavailableatdifferenttemperatures.EffectoftemperatureOften,foBoundandUnboundWaterinSolidsBoundwaterBoundandUnboundWaterinSolFreeandEquilibrium

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