第5章-水蒸氣和濕空氣課件

Thermodynamics---Chapter5TheWaterVaporandTheAir-Water-VaporMixture---Thermodynamics---Chapter5T1TheWaterVaporContentsTheheatingprocessofwateratconstantpressureThestatesofwatervaporThermodynamicprocessesofwatervaporSteamtablesTheWaterVaporContents25-1TheHeatingProcessofWateratConstantPressure

5-1-1BasicConceptions3.Boilingpoint（沸點(diǎn)）1.Vaporization（汽化）

2.Liquefaction（液化）5.Saturationstate（飽和狀態(tài)）saturatedliquidsaturatedvapor6.Wetvapor（濕飽和蒸汽）7.Superheatedvapor（過熱蒸汽）4.Subcooledliquid（過冷液體）5-1TheHeatingProcessofWat3

5-1-2TheHeatingProcessofWateratConstantPressure（水蒸氣的定壓產(chǎn)生過程）Theheatingprocessofwateratconstantpressureinapiston-cylinder（活塞式汽缸中水蒸氣的定壓產(chǎn)生過程）AnalysisAssumption：Considerapiston-cylinderdevicecontaining1kgliquidwaterat0oCUndertheseconditions,keeptheoutsidebarometricpressureandtheweightofthepistonareconstant.Heatisnowtransferredtothewater.

pHeat5-1-2TheHeatingProcesso4

1.Threestagesoftheheatingprocessofwater

（水蒸氣產(chǎn)生過程的三個(gè)階段）SubcooledliquidSaturatedliquid-vapormixtureSaturatedvaporSuperheatedvaporSaturatedliquid水定壓預(yù)熱飽和水定壓汽化干蒸汽定壓過熱pHeatpHeatpHeatpHeatpHeat1.Threestagesoftheheat5Heatistransferredtothewater,thetemperaturerises,theliquidwaterexpandsslightly,andsoitsspecificvolumeincreases,thepistonmoveupslightly.Asmoreheatistransferred,thetemperaturewillkeeprisinguntilitreachessaturationtemperaturecorrespondingtothesaturationpressure.Thewaterbewarmed-upatconstantpressure

（水定壓預(yù)熱）SubcooledliquidSaturatedliquidState2：psat，tsat，v’，h’，s’State1：psat，t，v，h，sHeatistransferredtothewa6Heatistransferredtothewater,theboilingstarts,thetemperaturewillremainconstantduringtheentirephase-changeprocess,thespecificvolumeincreaseslargely,theliquidleverdecreasesasaresultofmoreliquidturningtovapor.State3：psat，tsat，vx，hx，sxContinuetransferringheat,thevaporizationprocesswillcontinueuntilthelastdropofliquidisvaporized,Theentirecylinderisfilledwithvapor.State4：psat，tsat，v”，h”，s”Saturatedliquid-vapormixtureSaturatedvaporSaturatedliquidState2：psat，tsat，v’，h’，s’

Thesaturatedwaterevaporateatconstantpressure（水定壓汽化）Heatistransferredtothewat7Thesaturatedvaporoverheatatconstantpressure

（干蒸汽定壓過熱）Furthertransferofheatwillresultinanincreaseinboththetemperatureandthespecificvolume.Thevalueoftemperatureismorethanthatofsaturationtemperature.SaturatedvaporSuperheatedvaporState4：psat，tsat，v”，h”，s”State5：psat，t，v，h，sThesaturatedvaporoverheat8

abcdepWarm-upvaporationoverheating

vv’vxv”vvTsabcdes’sxs”s

Atcertainpressure

2.P-vandT-sdiagrams

abcdep9

Quality（干度）TheratioofthemassofvaportothetotalmassofthemixtureQualityhassignificanceforsaturatedmixtureonly

Forsaturatedliquidx=0,saturatedvaporx=1Notes

Tsabcdes’sxs”sTSQuality（干度）Qualityhassign10

5-1-3TheP-vandT-sDiagramsa1a2a3a4b4b2b3b1d4d3d2d1e4e3e2e1CTcrTABpcr0svppcra1a2a3a4b1e1d1b4b3b2d4d3d2e4e3e2BCATcr05-1-3TheP-vandT-sDiagra11criticalpoint（臨界點(diǎn)）saturationliquidline（下臨界線）saturationvaporline（上臨界線）liquidregion（液相區(qū)）saturatedliquid-vaporregion（汽液兩相區(qū)）vaporregion（汽相區(qū)）subcooledliquid（未飽和液體）saturatedliquid（飽和液體）saturatedliquid-vapormixture（濕蒸汽）saturatedvapor（干飽和蒸汽）superheatedvapor（過熱蒸汽）TwolinesThreeregionsFivestatesOnepoint是否有400oC的水？0oC或-10oC的水蒸氣criticalpoint（臨界點(diǎn)）saturation125-2PropertiesofWaterVapor

5-2-1ReferenceStateandreferencevaluesThedifferencebetweenidealgasesandrealgasesContrastReferenceState:thestateofsaturatedwaterat0.01oC.Theinternalenergyandentropyareassignedzerovaluesatthatstate.ThenEnthalpy5-2PropertiesofWaterVapor13

5-2-2PropertyTables（水與水蒸氣表）

Propertytablesofsaturatedliquidandsaturatedvapor(table5,6)

Propertytableofsubcooledliquidandsuperheatedvapor(table7)

Propertiesarelistedundertemperature（table5）

Propertiesarelistedunderpressure（table6）Aboveblackline:propertiesofsubcooledliquidUnderblackline:propertiesofsuperheatedvaporSteamtables:5-2-2PropertyTables（水與水蒸14Propertytableofsaturatedliquidandsaturatedvapor----listedundertemperature(table5)Propertytableofsaturatedl15Propertytableofsaturatedliquidandsaturatedvapor----listedunderpressure(table6)Propertytableofsaturatedl161.Saturatedliquidandsaturatedvaporstates壓力溫度比體積比焓汽化潛熱比熵液體蒸汽液體蒸汽液體蒸汽ptv’v‘’h’h’’γs’s’’0.00106.94910.0010001129.18529.212513.292484.10.10568.9735PressurepsortemperaturetsSaturatedliquid：Known:ps/ts

,Determine:v’,h’,s’,u’=h’-psv’Saturatedvapor：Known:ps/ts，Determine:v’’,h’’,s’’,u”=h”-psv”1.Saturatedliquidandsatu172.Saturatedliquid-vapormixture壓力溫度比體積比焓汽化潛熱比熵液體蒸汽液體蒸汽液體蒸汽ptv’v‘’h’h’’γs’s’’0.00106.94910.0010001129.18529.212513.292484.10.10568.9735Saturatedmixture1kgsaturatedliquid-vapormixtureconsistsofxkgsaturatedvaporand(1-x)kgsaturatedliquid.Pressureps(ortemperaturets)andqualityx2.Saturatedliquid-vapormi18Propertytableofsubcooledliquidandsuperheatedvapor(table7)Propertytableofsubcooledl193.Subcooledliquidandsuperheatedvapor8.34222648.916.2688.66392649.732.5669.40802650.3162.956808.23132610.815.3368.55372611.830.7129.29842612.7153.717600.5723167.510.00100798.43662574.028.8549.18232575.2144.475400.296383.870.00100180.296383.870.00100189.05882537.7135.226200.151042.010.00100030.151042.010.00100038.99382519.0130.59810-0.0002-0.040.0010002-0.0002-0050.0010002-0.0002-0.050.0010020shvshvshv溫度t0.010MPa0.005MPa0.001MPa壓力pPressurepandtemperaturet3.Subcooledliquidandsupe201.Determinethestateofwaterfromthesteamtables（1）t=45oC,v=0.00100993m3/kg;（2）t=200oC,x=0.9;（3）p=0.5MPa,t=165oC;（4）p=0.5MPa,v=0.545m3/kgExamples1.Determinethestateofwate21解：（1）

t=45oC,v=0.00100993m3/kg;由已知溫度，查飽和水與飽和水蒸氣表（附表5）。知：

確定該狀態(tài)為飽和水，查飽和水與飽和蒸汽表得：

分析求解過程（2）

t=200oC,x=0.9;該狀態(tài)為濕蒸汽，查飽和水與飽和水蒸汽表，得：解：（1）t=45oC,v=0.0010099322現(xiàn)

所以為過熱蒸汽狀態(tài)。查未飽和水和過熱水蒸氣表得：焓和熵可從上面兩者之間按線性插值求得：（3）

p=0.5MPa,t=165oC;當(dāng)對(duì)于現(xiàn)所以為過熱蒸汽狀態(tài)。焓和熵可從上面兩者之間按線性插值求得23所以該狀態(tài)為過熱蒸汽狀態(tài)。查未飽和水和過熱蒸汽表得：按線性插值求得：

（4）p=0.5MPa,v=0.545m3/kg當(dāng)時(shí)，飽和蒸汽的比體積所以該狀態(tài)為過熱蒸汽狀態(tài)。按線性插值求得：（4）p=0.524Conclusion

HowtojudgethestateofsubstanceIfknowpandt,checkpropertytablesofsaturatedliquidandsaturatedvapor.When:Ifknowp(ort),aswellaspropertyv（orh,ors）,lookuppropertytablesofsaturatedliquidandsaturatedvapor

first,determinethestateofvapor.When:SubcooledliquidSaturatedstate，stillgivenqualityxSuperheatedvaporSubcooledliquidSaturatedstateSuperheatedvaporThenlookuppropertytableofsubcooledliquidandsuperheatedvapor.Determinethestateofvapor.ConclusionHowtojudgethest25思考題1.臨界點(diǎn)時(shí)，飽和液體的焓等于干飽和蒸汽的焓。2.某液體的溫度為T，若其壓力大于T對(duì)應(yīng)的飽和壓力，則該液體一定處于未飽和液體狀態(tài)。3.干飽和蒸汽被定熵壓縮，將變?yōu)椋ǎ?.知道了溫度和壓力，就可以確定水蒸氣的狀態(tài)。5.水蒸氣的定溫膨脹過程滿足Q=W。Tps(T)實(shí)際氣體過熱蒸汽（）（）（x）（x）思考題1.臨界點(diǎn)時(shí)，飽和液體的焓等于干飽和蒸汽的焓。Tps265-3Basicprocessesofwatervapor（水蒸氣的基本熱力過程）

Basicprocessesofwatervapor:

ProcessesofIsochoric,Isobaric,Isothermal,adiabatic.

Calculationcontents:（1）Propertiesoftheinitialandfinalstates:（2）Heatandwork.

Methods：Bymeansoftables,graphs,andequations,aswellasauxiliarycalculationofcomputer.

Principles：1stand2ndlawsofthermodynamicsExpressionofreversible5-3Basicprocessesofwaterv27Howtofindthepropertiesofaninitialandfinalstatesforanidealgas?

Steps：Accordingtothepropertiesofinitialstate,usually(p,t)/(p,x)/(t,x),findtherestpropertiesatthisinitialstatebymeansofthesteamtables/graphs.Accordingtoonepropertyoffinalstateandthecharacteristicoftheprocess,findtherestpropertiesofthefinalstatebymeansofthesteamtables/graphs.Calculationq,u,w

Howtofindthepropertiesof282.水蒸氣由p1=1MPa,t1=300oC可逆絕熱膨脹到

p2=0.1MPa,求1kg水蒸氣所作的膨脹功和技術(shù)功。例題思路：（1）確定初態(tài)，及初態(tài)參數(shù)；（2）確定終態(tài)，及終態(tài)參數(shù)；（3）根據(jù)過程特點(diǎn)和能量守恒，計(jì)算功量。Steamtables2.水蒸氣由p1=1MPa,t1=300oC可逆絕熱膨脹293.Volumeandenergychangeduringevaporation

Amassof200gofsaturatedliquidwateriscompletelyvaporizedatconstantpressureof100kPa.Determine(a)thevolumechangeand(b)theamountofenergyaddedtothewater.例題3.Volumeandenergychangedu304.

Pressureandvolumeofamixture

Arigidtankcontains10kgofwaterat90℃.If8kgofthewaterisintheliquidformandrestisinthevaporform.Determine(a)thepressureinthetankand(b)thevolumeofthetank.例題4.Pressureandvolumeofami31例題5.

Propertiesofsaturatedliquid-vapormixtureAn80-Lvesselcontains4kgofrefrigerant-134aatapressureof160kPa.Determine(a)thetemperatureoftherefrigerant,(b)thequality,(c)theenthalpyoftherefrigerant,and(d)thevolumeoccupiedbythevaporphase.例題5.Propertiesofsaturated32TheAir-Water-VaporMixtureContentsThesaturatedairandunsaturatedairTheconceptionsofrelativehumidityandspecifichumidityTheAir-Water-VaporMixtureCon33

5-4TheAir-Water-VaporMixture（濕空氣）

AtmosphericAir（濕空氣）：Airthatcontainssomewatervapor(ormoisture).

DryAir（干空氣）：Airthatcontainsnowatervapor.

Assumption：

Atmosphericaircanbetreatedasanidealgasmixture.

水蒸氣分壓力很小，多處過熱狀態(tài)，v較大。ThetotalpressureisthesumofthepartialpressureofdryairPaandthatofwatervaporPv

濕空氣的總壓力：p=pv+pa

Theamountofdryairintheair-water-vapormixtureremainsconstant,buttheamountofwatervaporchanges.濕空氣來自環(huán)境大氣(pb)5-4TheAir-Water-VaporMix34

5-4-1TheSaturatedAirandUnsaturatedAirThepartialpressureofthewatervapor（水蒸氣分壓力）——theamountofwatervaporintheair1.TheUnsaturatedAirUnsaturatedairisamixtureofdryairandsuperheatedvapor.Ifpv<ps,thewatervaporisinthesuperheatedstate.Assume:airtemperatureT(correspondingtoitssaturatedpressureps),partialpressureofthewatervaporpv.Analysis“Unsaturated”means:thevalueofpartialpressureofwatervaporislessthanthatofsaturatedpressureatairtemperatureT.5-4-1TheSaturatedAirand35CAvp0pvpsTpvcanincreaseuptops(T)theamountsofwatervaporcanincreaseunsaturatedaircanabsorbwaterT0sAPSPVTC如何將過熱蒸汽轉(zhuǎn)變?yōu)轱柡驼羝?/p>

Method1:T一定時(shí)，增加水蒸氣含量，使pv不斷增大。當(dāng)pv=ps(T)，濕空氣中水蒸氣達(dá)到飽和，過熱蒸汽——干飽和蒸汽，不再具有吸收水分的能力。CAvp0pvpsTpvcanincreaseup36“Saturated”means：pv=pvmax=ps(T)，thevalueofthepartialpressureofwatervaporgetsmaximumvalue.AtthistemperatureT,theaircannotabsorbwater.Addwatervaportotheair,somevaporcondensesout.

2.TheSaturatedAir：Saturatedairisamixtureofdryairandsaturatedwatervapor.Assume:airtemperatureT(correspondingtoitssaturatedpressureps),partialpressureofthewatervaporpv.Analysis“Saturated”means：pv=pvmax=37

HowtochangetheunsaturatedairtothesaturatedairAnalysisC

法1：T一定時(shí)，增加pv=pvmax=ps（T）,A—C。

法2：保持水蒸氣含量（pv）不變，降低濕空氣溫度T=TS（PV），A—B。BCBDDAvp0pvpsTT0sAPSPVTTdHowtochangetheunsaturat38

5-4-2Dew-PointTemperature（露點(diǎn)溫度）

1.

DewFormation（結(jié)露）：保持濕空氣中水蒸氣的分壓力不變，對(duì)飽和濕空氣繼續(xù)冷卻降溫，則其中的部分水蒸氣將凝結(jié)為水.這種現(xiàn)象稱為結(jié)露。

2.Dew-PointTemperature

Tdisthesaturatedtemperatureofwatercorrespondingtothevaporpressure.（濕空氣中水蒸氣的分壓力pv所對(duì)應(yīng)的飽和溫度）T0sAPSPVTTdNotesIfTd<0oC,

就會(huì)出現(xiàn)結(jié)霜。

析濕過程

C5-4-2Dew-PointTemperature39

5-4-3SpecificandRelativeHumidityofAir

（相對(duì)濕度和含濕量）

Humidity（濕空氣的濕度）

Theamountofwaterintheair（濕空氣中水蒸氣的含量）

1.AbsoluteHumidity（絕對(duì)濕度）（1）Themassofwatervaporpresentin1m3ofair.

（1m3的濕空氣中所含水蒸氣的質(zhì)量）（2）Expression（3）Forsaturatedair

水蒸氣的體積5-4-3SpecificandRelative40

2.RelativeHumidity（相對(duì)濕度）（1）Definition：Theratiooftheamountofmoisturetheairholdsrelativetothemaximumamountofmoisturetheaircanholdatthesametemperature.（濕空氣的絕對(duì)濕度與同溫度下濕空氣的最大絕對(duì)濕度之比）（2）Notes：相對(duì)濕度φ越小，濕空氣中水蒸氣偏離飽和狀態(tài)越遠(yuǎn)，空氣越干燥，吸濕能力越強(qiáng)。

Fordryair:φ=0；Forsaturatedairφ=1，2.RelativeHumidity（相對(duì)濕度）（1413.SpecificHumidity（含濕量/比濕度）（1）Definition:Themassofwatervaporpresentinaunitmassofdryair.（在濕空氣中，與單位質(zhì)量干空氣共存的水蒸氣含量）（2）Expression（3）TheRelationshipofPV,dandφAccordingtoideal-gas

equationofstate3.SpecificHumidity（含濕量/比濕度42So：

5-4-4

濕空氣的相對(duì)分子質(zhì)量，氣體常數(shù)及密度1.濕空氣的相對(duì)分子質(zhì)量：說明So：5-4-4濕空氣的相對(duì)分子質(zhì)量，氣體常數(shù)及密度432.濕空氣的氣體常數(shù)：說明Rg隨水蒸氣分壓力

pv的提高而增大。3.濕空氣的密度：說明濕空氣的密度永遠(yuǎn)小于干空氣的密度。2.濕空氣的氣體常數(shù)：說明Rg隨水蒸氣分壓力pv的提44思考題1.相對(duì)濕度為=0時(shí)，說明空氣中完全沒有水蒸氣。2.相對(duì)濕度為=1時(shí)，說明空氣中都是水蒸氣。3.空氣的相對(duì)濕度越大，其含濕量越高。4.對(duì)未飽和濕空氣，露點(diǎn)溫度即水蒸氣分壓力所對(duì)應(yīng)的水的飽和溫度。思考題1.相對(duì)濕度為=0時(shí)，說明空氣中完全沒有水蒸氣。455.pV=nRT公式適用于：（1）水蒸氣（2）濕空氣（3）理想氣體6.濕空氣的d一定時(shí)，溫度越高，其吸濕能力：（1）越強(qiáng)（2）越弱（3）相等7.濕空氣壓力一定時(shí)，其中水蒸氣的分壓力取決于（1）含濕量（2）相對(duì)濕度（3）露點(diǎn)思考題5.pV=nRT公式適用于：思考題46問答題1.冬季，室內(nèi)玻璃窗內(nèi)側(cè)為什么會(huì)結(jié)霜？為什么陰天晾衣服不宜干，而晴天易干？冬季室內(nèi)供暖，為何要加濕？霉季時(shí)，冷水管的表面常有水滴出現(xiàn)，為什么？問答題1.冬季，室內(nèi)玻璃窗內(nèi)側(cè)為什么會(huì)結(jié)霜？473.房間的容積為50m3,室內(nèi)空氣溫度為30oC，相對(duì)濕度為60%，大氣壓力為0.1013MPa，求：濕空氣的露點(diǎn)溫度td，含濕量d，空氣的質(zhì)量ma，水蒸氣質(zhì)量mv。例題總結(jié)：要確定濕空氣的狀態(tài)，除壓力p，溫度t外，還需知道濕空氣中水蒸氣的含量，即知道ρv,φ,d,pv,td中的一個(gè)。3.房間的容積為50m3,室內(nèi)空氣溫度為30oC，例題48Thermodynamics---Chapter5TheWaterVaporandTheAir-Water-VaporMixture---Thermodynamics---Chapter5T49TheWaterVaporContentsTheheatingprocessofwateratconstantpressureThestatesofwatervaporThermodynamicprocessesofwatervaporSteamtablesTheWaterVaporContents505-1TheHeatingProcessofWateratConstantPressure

5-1-1BasicConceptions3.Boilingpoint（沸點(diǎn)）1.Vaporization（汽化）

2.Liquefaction（液化）5.Saturationstate（飽和狀態(tài)）saturatedliquidsaturatedvapor6.Wetvapor（濕飽和蒸汽）7.Superheatedvapor（過熱蒸汽）4.Subcooledliquid（過冷液體）5-1TheHeatingProcessofWat51

5-1-2TheHeatingProcessofWateratConstantPressure（水蒸氣的定壓產(chǎn)生過程）Theheatingprocessofwateratconstantpressureinapiston-cylinder（活塞式汽缸中水蒸氣的定壓產(chǎn)生過程）AnalysisAssumption：Considerapiston-cylinderdevicecontaining1kgliquidwaterat0oCUndertheseconditions,keeptheoutsidebarometricpressureandtheweightofthepistonareconstant.Heatisnowtransferredtothewater.

pHeat5-1-2TheHeatingProcesso52

1.Threestagesoftheheatingprocessofwater

（水蒸氣產(chǎn)生過程的三個(gè)階段）SubcooledliquidSaturatedliquid-vapormixtureSaturatedvaporSuperheatedvaporSaturatedliquid水定壓預(yù)熱飽和水定壓汽化干蒸汽定壓過熱pHeatpHeatpHeatpHeatpHeat1.Threestagesoftheheat53Heatistransferredtothewater,thetemperaturerises,theliquidwaterexpandsslightly,andsoitsspecificvolumeincreases,thepistonmoveupslightly.Asmoreheatistransferred,thetemperaturewillkeeprisinguntilitreachessaturationtemperaturecorrespondingtothesaturationpressure.Thewaterbewarmed-upatconstantpressure

（水定壓預(yù)熱）SubcooledliquidSaturatedliquidState2：psat，tsat，v’，h’，s’State1：psat，t，v，h，sHeatistransferredtothewa54Heatistransferredtothewater,theboilingstarts,thetemperaturewillremainconstantduringtheentirephase-changeprocess,thespecificvolumeincreaseslargely,theliquidleverdecreasesasaresultofmoreliquidturningtovapor.State3：psat，tsat，vx，hx，sxContinuetransferringheat,thevaporizationprocesswillcontinueuntilthelastdropofliquidisvaporized,Theentirecylinderisfilledwithvapor.State4：psat，tsat，v”，h”，s”Saturatedliquid-vapormixtureSaturatedvaporSaturatedliquidState2：psat，tsat，v’，h’，s’

Thesaturatedwaterevaporateatconstantpressure（水定壓汽化）Heatistransferredtothewat55Thesaturatedvaporoverheatatconstantpressure

（干蒸汽定壓過熱）Furthertransferofheatwillresultinanincreaseinboththetemperatureandthespecificvolume.Thevalueoftemperatureismorethanthatofsaturationtemperature.SaturatedvaporSuperheatedvaporState4：psat，tsat，v”，h”，s”State5：psat，t，v，h，sThesaturatedvaporoverheat56

abcdepWarm-upvaporationoverheating

vv’vxv”vvTsabcdes’sxs”s

Atcertainpressure

2.P-vandT-sdiagrams

abcdep57

Quality（干度）TheratioofthemassofvaportothetotalmassofthemixtureQualityhassignificanceforsaturatedmixtureonly

Forsaturatedliquidx=0,saturatedvaporx=1Notes

Tsabcdes’sxs”sTSQuality（干度）Qualityhassign58

5-1-3TheP-vandT-sDiagramsa1a2a3a4b4b2b3b1d4d3d2d1e4e3e2e1CTcrTABpcr0svppcra1a2a3a4b1e1d1b4b3b2d4d3d2e4e3e2BCATcr05-1-3TheP-vandT-sDiagra59criticalpoint（臨界點(diǎn)）saturationliquidline（下臨界線）saturationvaporline（上臨界線）liquidregion（液相區(qū)）saturatedliquid-vaporregion（汽液兩相區(qū)）vaporregion（汽相區(qū)）subcooledliquid（未飽和液體）saturatedliquid（飽和液體）saturatedliquid-vapormixture（濕蒸汽）saturatedvapor（干飽和蒸汽）superheatedvapor（過熱蒸汽）TwolinesThreeregionsFivestatesOnepoint是否有400oC的水？0oC或-10oC的水蒸氣criticalpoint（臨界點(diǎn)）saturation605-2PropertiesofWaterVapor

5-2-1ReferenceStateandreferencevaluesThedifferencebetweenidealgasesandrealgasesContrastReferenceState:thestateofsaturatedwaterat0.01oC.Theinternalenergyandentropyareassignedzerovaluesatthatstate.ThenEnthalpy5-2PropertiesofWaterVapor61

5-2-2PropertyTables（水與水蒸氣表）

Propertytablesofsaturatedliquidandsaturatedvapor(table5,6)

Propertytableofsubcooledliquidandsuperheatedvapor(table7)

Propertiesarelistedundertemperature（table5）

Propertiesarelistedunderpressure（table6）Aboveblackline:propertiesofsubcooledliquidUnderblackline:propertiesofsuperheatedvaporSteamtables:5-2-2PropertyTables（水與水蒸62Propertytableofsaturatedliquidandsaturatedvapor----listedundertemperature(table5)Propertytableofsaturatedl63Propertytableofsaturatedliquidandsaturatedvapor----listedunderpressure(table6)Propertytableofsaturatedl641.Saturatedliquidandsaturatedvaporstates壓力溫度比體積比焓汽化潛熱比熵液體蒸汽液體蒸汽液體蒸汽ptv’v‘’h’h’’γs’s’’0.00106.94910.0010001129.18529.212513.292484.10.10568.9735PressurepsortemperaturetsSaturatedliquid：Known:ps/ts

,Determine:v’,h’,s’,u’=h’-psv’Saturatedvapor：Known:ps/ts，Determine:v’’,h’’,s’’,u”=h”-psv”1.Saturatedliquidandsatu652.Saturatedliquid-vapormixture壓力溫度比體積比焓汽化潛熱比熵液體蒸汽液體蒸汽液體蒸汽ptv’v‘’h’h’’γs’s’’0.00106.94910.0010001129.18529.212513.292484.10.10568.9735Saturatedmixture1kgsaturatedliquid-vapormixtureconsistsofxkgsaturatedvaporand(1-x)kgsaturatedliquid.Pressureps(ortemperaturets)andqualityx2.Saturatedliquid-vapormi66Propertytableofsubcooledliquidandsuperheatedvapor(table7)Propertytableofsubcooledl673.Subcooledliquidandsuperheatedvapor8.34222648.916.2688.66392649.732.5669.40802650.3162.956808.23132610.815.3368.55372611.830.7129.29842612.7153.717600.5723167.510.00100798.43662574.028.8549.18232575.2144.475400.296383.870.00100180.296383.870.00100189.05882537.7135.226200.151042.010.00100030.151042.010.00100038.99382519.0130.59810-0.0002-0.040.0010002-0.0002-0050.0010002-0.0002-0.050.0010020shvshvshv溫度t0.010MPa0.005MPa0.001MPa壓力pPressurepandtemperaturet3.Subcooledliquidandsupe681.Determinethestateofwaterfromthesteamtables（1）t=45oC,v=0.00100993m3/kg;（2）t=200oC,x=0.9;（3）p=0.5MPa,t=165oC;（4）p=0.5MPa,v=0.545m3/kgExamples1.Determinethestateofwate69解：（1）

t=45oC,v=0.00100993m3/kg;由已知溫度，查飽和水與飽和水蒸氣表（附表5）。知：

確定該狀態(tài)為飽和水，查飽和水與飽和蒸汽表得：

分析求解過程（2）

t=200oC,x=0.9;該狀態(tài)為濕蒸汽，查飽和水與飽和水蒸汽表，得：解：（1）t=45oC,v=0.0010099370現(xiàn)

所以為過熱蒸汽狀態(tài)。查未飽和水和過熱水蒸氣表得：焓和熵可從上面兩者之間按線性插值求得：（3）

p=0.5MPa,t=165oC;當(dāng)對(duì)于現(xiàn)所以為過熱蒸汽狀態(tài)。焓和熵可從上面兩者之間按線性插值求得71所以該狀態(tài)為過熱蒸汽狀態(tài)。查未飽和水和過熱蒸汽表得：按線性插值求得：

（4）p=0.5MPa,v=0.545m3/kg當(dāng)時(shí)，飽和蒸汽的比體積所以該狀態(tài)為過熱蒸汽狀態(tài)。按線性插值求得：（4）p=0.572Conclusion

HowtojudgethestateofsubstanceIfknowpandt,checkpropertytablesofsaturatedliquidandsaturatedvapor.When:Ifknowp(ort),aswellaspropertyv（orh,ors）,lookuppropertytablesofsaturatedliquidandsaturatedvapor

first,determinethestateofvapor.When:SubcooledliquidSaturatedstate，stillgivenqualityxSuperheatedvaporSubcooledliquidSaturatedstateSuperheatedvaporThenlookuppropertytableofsubcooledliquidandsuperheatedvapor.Determinethestateofvapor.ConclusionHowtojudgethest73思考題1.臨界點(diǎn)時(shí)，飽和液體的焓等于干飽和蒸汽的焓。2.某液體的溫度為T，若其壓力大于T對(duì)應(yīng)的飽和壓力，則該液體一定處于未飽和液體狀態(tài)。3.干飽和蒸汽被定熵壓縮，將變?yōu)椋ǎ?.知道了溫度和壓力，就可以確定水蒸氣的狀態(tài)。5.水蒸氣的定溫膨脹過程滿足Q=W。Tps(T)實(shí)際氣體過熱蒸汽（）（）（x）（x）思考題1.臨界點(diǎn)時(shí)，飽和液體的焓等于干飽和蒸汽的焓。Tps745-3Basicprocessesofwatervapor（水蒸氣的基本熱力過程）

Basicprocessesofwatervapor:

ProcessesofIsochoric,Isobaric,Isothermal,adiabatic.

Calculationcontents:（1）Propertiesoftheinitialandfinalstates:（2）Heatandwork.

Methods：Bymeansoftables,graphs,andequations,aswellasauxiliarycalculationofcomputer.

Principles：1stand2ndlawsofthermodynamicsExpressionofreversible5-3Basicprocessesofwaterv75Howtofindthepropertiesofaninitialandfinalstatesforanidealgas?

Steps：Accordingtothepropertiesofinitialstate,usually(p,t)/(p,x)/(t,x),findtherestpropertiesatthisinitialstatebymeansofthesteamtables/graphs.Accordingtoonepropertyoffinalstateandthecharacteristicoftheprocess,findtherestpropertiesofthefinalstatebymeansofthesteamtables/graphs.Calculationq,u,w

Howtofindthepropertiesof762.水蒸氣由p1=1MPa,t1=300oC可逆絕熱膨脹到

p2=0.1MPa,求1kg水蒸氣所作的膨脹功和技術(shù)功。例題思路：（1）確定初態(tài)，及初態(tài)參數(shù)；（2）確定終態(tài)，及終態(tài)參數(shù)；（3）根據(jù)過程特點(diǎn)和能量守恒，計(jì)算功量。Steamtables2.水蒸氣由p1=1MPa,t1=300oC可逆絕熱膨脹773.Volumeandenergychangeduringevaporation

Amassof200gofsaturatedliquidwateriscompletelyvaporizedatconstantpressureof100kPa.Determine(a)thevolumechangeand(b)theamountofenergyaddedtothewater.例題3.Volumeandenergychangedu784.

Pressureandvolumeofamixture

Arigidtankcontains10kgofwaterat90℃.If8kgofthewaterisintheliquidformandrestisinthevaporform.Determine(a)thepressureinthetankand(b)thevolumeofthetank.例題4.Pressureandvolumeofami79例題5.

Propertiesofsaturatedliquid-vapormixtureAn80-Lvesselcontains4kgofrefrigerant-134aatapressureof160kPa.Determine(a)thetemperatureoftherefrigerant,(b)thequality,(c)theenthalpyoftherefrigerant,and(d)thevolumeoccupiedbythevaporphase.例題5.Propertiesofsaturated80TheAir-Water-VaporMixtureContentsThesaturatedairandunsaturatedairTheconceptionsofrelativehumidityandspecifichumidityTheAir-Water-VaporMixtureCon81

5-4TheAir-Water-VaporMixture（濕空氣）

AtmosphericAir（濕空氣）：Airthatcontainssomewatervapor(ormoisture).

DryAir（干空氣）：Airthatcontainsnowatervapor.

Assumption：

Atmosphericaircanbetreatedasanidealgasmixture.

水蒸氣分壓力很小，多處過熱狀態(tài)，v較大。ThetotalpressureisthesumofthepartialpressureofdryairPaandthatofwatervaporPv

濕空氣的總壓力：p=pv+pa

Theamountofdryairintheair-water-vapormixtureremainsconstant,buttheamountofwatervaporchanges.濕空氣來自環(huán)境大氣(pb)5-4TheAir-Water-VaporMix82

5-4-1TheSaturatedAirandUnsaturatedAirThepartialpressureofthewatervapor（水蒸氣分壓力）——theamountofwatervaporintheair1.TheUnsaturatedAirUnsaturatedairisamixtureofdryairands