第5章-水蒸气和湿空气课件

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

5-1-1BasicConceptions3.Boilingpoint（沸点）1.Vaporization（汽化）

2.Liquefaction（液化）5.Saturationstate（饱和状态）saturatedliquidsaturatedvapor6.Wetvapor（湿饱和蒸汽）7.Superheatedvapor（过热蒸汽）4.Subcooledliquid（过冷液体）5-1TheHeatingProcessofWat3

5-1-2TheHeatingProcessofWateratConstantPressure（水蒸气的定压产生过程）Theheatingprocessofwateratconstantpressureinapiston-cylinder（活塞式汽缸中水蒸气的定压产生过程）AnalysisAssumption：Considerapiston-cylinderdevicecontaining1kgliquidwaterat0ºCUndertheseconditions,keeptheoutsidebarometricpressureandtheweightofthepistonareconstant.Heatisnowtransferredtothewater.

pHeat5-1-2TheHeatingProcesso4

1.Threestagesoftheheatingprocessofwater

（水蒸气产生过程的三个阶段）SubcooledliquidSaturatedliquid-vapormixtureSaturatedvaporSuperheatedvaporSaturatedliquid水定压预热饱和水定压汽化干蒸汽定压过热pHeatpHeatpHeatpHeatpHeat1.Threestagesoftheheat5Heatistransferredtothewater,thetemperaturerises,theliquidwaterexpandsslightly,andsoitsspecificvolumeincreases,thepistonmoveupslightly.Asmoreheatistransferred,thetemperaturewillkeeprisinguntilitreachessaturationtemperaturecorrespondingtothesaturationpressure.Thewaterbewarmed-upatconstantpressure

（水定压预热）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（水定压汽化）Heatistransferredtothewat7Thesaturatedvaporoverheatatconstantpressure

（干蒸汽定压过热）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（临界点）saturationliquidline（下临界线）saturationvaporline（上临界线）liquidregion（液相区）saturatedliquid-vaporregion（汽液两相区）vaporregion（汽相区）subcooledliquid（未饱和液体）saturatedliquid（饱和液体）saturatedliquid-vapormixture（湿蒸汽）saturatedvapor（干饱和蒸汽）superheatedvapor（过热蒸汽）TwolinesThreeregionsFivestatesOnepoint是否有400ºC的水？0ºC或-10ºC的水蒸气criticalpoint（临界点）saturation125-2PropertiesofWaterVapor

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

5-2-2PropertyTables（水与水蒸气表）

Propertytablesofsaturatedliquidandsaturatedvapor(table5,6)

Propertytableofsubcooledliquidandsuperheatedvapor(table7)

Propertiesarelistedundertemperature（table5）

Propertiesarelistedunderpressure（table6）Aboveblackline:propertiesofsubcooledliquidUnderblackline:propertiesofsuperheatedvaporSteamtables:5-2-2PropertyTables（水与水蒸14Propertytableofsaturatedliquidandsaturatedvapor----listedundertemperature(table5)Propertytableofsaturatedl15Propertytableofsaturatedliquidandsaturatedvapor----listedunderpressure(table6)Propertytableofsaturatedl161.Saturatedliquidandsaturatedvaporstates压力温度比体积比焓汽化潜热比熵液体蒸汽液体蒸汽液体蒸汽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压力温度比体积比焓汽化潜热比熵液体蒸汽液体蒸汽液体蒸汽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温度t0.010MPa0.005MPa0.001MPa压力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;由已知温度，查饱和水与饱和水蒸气表（附表5）。知：

确定该状态为饱和水，查饱和水与饱和蒸汽表得：

分析求解过程（2）

t=200ºC,x=0.9;该状态为湿蒸汽，查饱和水与饱和水蒸汽表，得：解：（1）t=45ºC,v=0.0010099322现

所以为过热蒸汽状态。查未饱和水和过热水蒸气表得：焓和熵可从上面两者之间按线性插值求得：（3）

p=0.5MPa,t=165ºC;当对于现所以为过热蒸汽状态。焓和熵可从上面两者之间按线性插值求得23所以该状态为过热蒸汽状态。查未饱和水和过热蒸汽表得：按线性插值求得：

（4）p=0.5MPa,v=0.545m3/kg当时，饱和蒸汽的比体积所以该状态为过热蒸汽状态。按线性插值求得：（4）p=0.524Conclusion

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

first,determinethestateofvapor.When:SubcooledliquidSaturatedstate，stillgivenqualityxSuperheatedvaporSubcooledliquidSaturatedstateSuperheatedvaporThenlookuppropertytableofsubcooledliquidandsuperheatedvapor.Determinethestateofvapor.ConclusionHowtojudgethest25思考题1.临界点时，饱和液体的焓等于干饱和蒸汽的焓。2.某液体的温度为T，若其压力大于T对应的饱和压力，则该液体一定处于未饱和液体状态。3.干饱和蒸汽被定熵压缩，将变为（）。4.知道了温度和压力，就可以确定水蒸气的状态。5.水蒸气的定温膨胀过程满足Q=W。Tps(T)实际气体过热蒸汽（）（）（x）（x）思考题1.临界点时，饱和液体的焓等于干饱和蒸汽的焓。Tps265-3Basicprocessesofwatervapor（水蒸气的基本热力过程）

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.水蒸气由p1=1MPa,t1=300ºC可逆绝热膨胀到

p2=0.1MPa,求1kg水蒸气所作的膨胀功和技术功。例题思路：（1）确定初态，及初态参数；（2）确定终态，及终态参数；（3）根据过程特点和能量守恒，计算功量。Steamtables2.水蒸气由p1=1MPa,t1=300ºC可逆绝热膨胀293.Volumeandenergychangeduringevaporation

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

Pressureandvolumeofamixture

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

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

5-4TheAir-Water-VaporMixture（湿空气）

AtmosphericAir（湿空气）：Airthatcontainssomewatervapor(ormoisture).

DryAir（干空气）：Airthatcontainsnowatervapor.

Assumption：

Atmosphericaircanbetreatedasanidealgasmixture.

水蒸气分压力很小，多处过热状态，v较大。ThetotalpressureisthesumofthepartialpressureofdryairPaandthatofwatervaporPv

湿空气的总压力：p=pv+pa

Theamountofdryairintheair-water-vapormixtureremainsconstant,buttheamountofwatervaporchanges.湿空气来自环境大气(pb)5-4TheAir-Water-VaporMix34

5-4-1TheSaturatedAirandUnsaturatedAirThepartialpressureofthewatervapor（水蒸气分压力）——theamountofwatervaporintheair1.TheUnsaturatedAirUnsaturatedairisamixtureofdryairandsuperheatedvapor.Ifpv<ps,thewatervaporisinthesuperheatedstate.Assume:airtemperatureT(correspondingtoitssaturatedpressureps),partialpressureofthewatervaporpv.Analysis“Unsaturated”means:thevalueofpartialpressureofwatervaporislessthanthatofsaturatedpressureatairtemperatureT.5-4-1TheSaturatedAirand35CAvp0pvpsTpvcanincreaseuptops(T)theamountsofwatervaporcanincreaseunsaturatedaircanabsorbwaterT0sAPSPVTC如何将过热蒸汽转变为饱和蒸汽？

Method1:T一定时，增加水蒸气含量，使pv不断增大。当pv=ps(T)，湿空气中水蒸气达到饱和，过热蒸汽——干饱和蒸汽，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一定时，增加pv=pvmax=ps（T）,A—C。

法2：保持水蒸气含量（pv）不变，降低湿空气温度T=TS（PV），A—B。BCBDDAvp0pvpsTT0sAPSPVTTdHowtochangetheunsaturat38

5-4-2Dew-PointTemperature（露点温度）

1.

DewFormation（结露）：保持湿空气中水蒸气的分压力不变，对饱和湿空气继续冷却降温，则其中的部分水蒸气将凝结为水.这种现象称为结露。

2.Dew-PointTemperature

Tdisthesaturatedtemperatureofwatercorrespondingtothevaporpressure.（湿空气中水蒸气的分压力pv所对应的饱和温度）T0sAPSPVTTdNotesIfTd<0ºC,

就会出现结霜。

析湿过程

C5-4-2Dew-PointTemperature39

5-4-3SpecificandRelativeHumidityofAir

（相对湿度和含湿量）

Humidity（湿空气的湿度）

Theamountofwaterintheair（湿空气中水蒸气的含量）

1.AbsoluteHumidity（绝对湿度）（1）Themassofwatervaporpresentin1m3ofair.

（1m3的湿空气中所含水蒸气的质量）（2）Expression（3）Forsaturatedair

水蒸气的体积5-4-3SpecificandRelative40

2.RelativeHumidity（相对湿度）（1）Definition：Theratiooftheamountofmoisturetheairholdsrelativetothemaximumamountofmoisturetheaircanholdatthesametemperature.（湿空气的绝对湿度与同温度下湿空气的最大绝对湿度之比）（2）Notes：相对湿度φ越小，湿空气中水蒸气偏离饱和状态越远，空气越干燥，吸湿能力越强。

Fordryair:φ=0；Forsaturatedairφ=1，2.RelativeHumidity（相对湿度）（1413.SpecificHumidity（含湿量/比湿度）（1）Definition:Themassofwatervaporpresentinaunitmassofdryair.（在湿空气中，与单位质量干空气共存的水蒸气含量）（2）Expression（3）TheRelationshipofPV,dandφAccordingtoideal-gas

equationofstate3.SpecificHumidity（含湿量/比湿度42So：

5-4-4

湿空气的相对分子质量，气体常数及密度1.湿空气的相对分子质量：说明So：5-4-4湿空气的相对分子质量，气体常数及密度432.湿空气的气体常数：说明Rg随水蒸气分压力

pv的提高而增大。3.湿空气的密度：说明湿空气的密度永远小于干空气的密度。2.湿空气的气体常数：说明Rg随水蒸气分压力pv的提44思考题1.相对湿度为=0时，说明空气中完全没有水蒸气。2.相对湿度为=1时，说明空气中都是水蒸气。3.空气的相对湿度越大，其含湿量越高。4.对未饱和湿空气，露点温度即水蒸气分压力所对应的水的饱和温度。思考题1.相对湿度为=0时，说明空气中完全没有水蒸气。455.pV=nRT公式适用于：（1）水蒸气（2）湿空气（3）理想气体6.湿空气的d一定时，温度越高，其吸湿能力：（1）越强（2）越弱（3）相等7.湿空气压力一定时，其中水蒸气的分压力取决于（1）含湿量（2）相对湿度（3）露点思考题5.pV=nRT公式适用于：思考题46问答题1.冬季，室内玻璃窗内侧为什么会结霜？为什么阴天晾衣服不宜干，而晴天易干？冬季室内供暖，为何要加湿？霉季时，冷水管的表面常有水滴出现，为什么？问答题1.冬季，室内玻璃窗内侧为什么会结霜？473.房间的容积为50m3,室内空气温度为30ºC，相对湿度为60%，大气压力为0.1013MPa，求：湿空气的露点温度td，含湿量d，空气的质量ma，水蒸气质量mv。例题总结：要确定湿空气的状态，除压力p，温度t外，还需知道湿空气中水蒸气的含量，即知道ρv,φ,d,pv,td中的一个。3.房间的容积为50m3,室内空气温度为30ºC，例题48Thermodynamics---Chapter5TheWaterVaporandTheAir-Water-VaporMixture---Thermodynamics---Chapter5T49TheWaterVaporContentsTheheatingprocessofwateratconstantpressureThestatesofwatervaporThermodynamicprocessesofwatervaporSteamtablesTheWaterVaporContents505-1TheHeatingProcessofWateratConstantPressure

5-1-1BasicConceptions3.Boilingpoint（沸点）1.Vaporization（汽化）

2.Liquefaction（液化）5.Saturationstate（饱和状态）saturatedliquidsaturatedvapor6.Wetvapor（湿饱和蒸汽）7.Superheatedvapor（过热蒸汽）4.Subcooledliquid（过冷液体）5-1TheHeatingProcessofWat51

5-1-2TheHeatingProcessofWateratConstantPressure（水蒸气的定压产生过程）Theheatingprocessofwateratconstantpressureinapiston-cylinder（活塞式汽缸中水蒸气的定压产生过程）AnalysisAssumption：Considerapiston-cylinderdevicecontaining1kgliquidwaterat0ºCUndertheseconditions,keeptheoutsidebarometricpressureandtheweightofthepistonareconstant.Heatisnowtransferredtothewater.

pHeat5-1-2TheHeatingProcesso52

1.Threestagesoftheheatingprocessofwater

（水蒸气产生过程的三个阶段）SubcooledliquidSaturatedliquid-vapormixtureSaturatedvaporSuperheatedvaporSaturatedliquid水定压预热饱和水定压汽化干蒸汽定压过热pHeatpHeatpHeatpHeatpHeat1.Threestagesoftheheat53Heatistransferredtothewater,thetemperaturerises,theliquidwaterexpandsslightly,andsoitsspecificvolumeincreases,thepistonmoveupslightly.Asmoreheatistransferred,thetemperaturewillkeeprisinguntilitreachessaturationtemperaturecorrespondingtothesaturationpressure.Thewaterbewarmed-upatconstantpressure

（水定压预热）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（水定压汽化）Heatistransferredtothewat55Thesaturatedvaporoverheatatconstantpressure

（干蒸汽定压过热）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（临界点）saturationliquidline（下临界线）saturationvaporline（上临界线）liquidregion（液相区）saturatedliquid-vaporregion（汽液两相区）vaporregion（汽相区）subcooledliquid（未饱和液体）saturatedliquid（饱和液体）saturatedliquid-vapormixture（湿蒸汽）saturatedvapor（干饱和蒸汽）superheatedvapor（过热蒸汽）TwolinesThreeregionsFivestatesOnepoint是否有400ºC的水？0ºC或-10ºC的水蒸气criticalpoint（临界点）saturation605-2PropertiesofWaterVapor

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

5-2-2PropertyTables（水与水蒸气表）

Propertytablesofsaturatedliquidandsaturatedvapor(table5,6)

Propertytableofsubcooledliquidandsuperheatedvapor(table7)

Propertiesarelistedundertemperature（table5）

Propertiesarelistedunderpressure（table6）Aboveblackline:propertiesofsubcooledliquidUnderblackline:propertiesofsuperheatedvaporSteamtables:5-2-2PropertyTables（水与水蒸62Propertytableofsaturatedliquidandsaturatedvapor----listedundertemperature(table5)Propertytableofsaturatedl63Propertytableofsaturatedliquidandsaturatedvapor----listedunderpressure(table6)Propertytableofsaturatedl641.Saturatedliquidandsaturatedvaporstates压力温度比体积比焓汽化潜热比熵液体蒸汽液体蒸汽液体蒸汽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压力温度比体积比焓汽化潜热比熵液体蒸汽液体蒸汽液体蒸汽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温度t0.010MPa0.005MPa0.001MPa压力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;由已知温度，查饱和水与饱和水蒸气表（附表5）。知：

确定该状态为饱和水，查饱和水与饱和蒸汽表得：

分析求解过程（2）

t=200ºC,x=0.9;该状态为湿蒸汽，查饱和水与饱和水蒸汽表，得：解：（1）t=45ºC,v=0.0010099370现

所以为过热蒸汽状态。查未饱和水和过热水蒸气表得：焓和熵可从上面两者之间按线性插值求得：（3）

p=0.5MPa,t=165ºC;当对于现所以为过热蒸汽状态。焓和熵可从上面两者之间按线性插值求得71所以该状态为过热蒸汽状态。查未饱和水和过热蒸汽表得：按线性插值求得：

（4）p=0.5MPa,v=0.545m3/kg当时，饱和蒸汽的比体积所以该状态为过热蒸汽状态。按线性插值求得：（4）p=0.572Conclusion

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

first,determinethestateofvapor.When:SubcooledliquidSaturatedstate，stillgivenqualityxSuperheatedvaporSubcooledliquidSaturatedstateSuperheatedvaporThenlookuppropertytableofsubcooledliquidandsuperheatedvapor.Determinethestateofvapor.ConclusionHowtojudgethest73思考题1.临界点时，饱和液体的焓等于干饱和蒸汽的焓。2.某液体的温度为T，若其压力大于T对应的饱和压力，则该液体一定处于未饱和液体状态。3.干饱和蒸汽被定熵压缩，将变为（）。4.知道了温度和压力，就可以确定水蒸气的状态。5.水蒸气的定温膨胀过程满足Q=W。Tps(T)实际气体过热蒸汽（）（）（x）（x）思考题1.临界点时，饱和液体的焓等于干饱和蒸汽的焓。Tps745-3Basicprocessesofwatervapor（水蒸气的基本热力过程）

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.水蒸气由p1=1MPa,t1=300ºC可逆绝热膨胀到

p2=0.1MPa,求1kg水蒸气所作的膨胀功和技术功。例题思路：（1）确定初态，及初态参数；（2）确定终态，及终态参数；（3）根据过程特点和能量守恒，计算功量。Steamtables2.水蒸气由p1=1MPa,t1=300ºC可逆绝热膨胀773.Volumeandenergychangeduringevaporation

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

Pressureandvolumeofamixture

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

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

5-4TheAir-Water-VaporMixture（湿空气）

AtmosphericAir（湿空气）：Airthatcontainssomewatervapor(ormoisture).

DryAir（干空气）：Airthatcontainsnowatervapor.

Assumption：

Atmosphericaircanbetreatedasanidealgasmixture.

水蒸气分压力很小，多处过热状态，v较大。ThetotalpressureisthesumofthepartialpressureofdryairPaandthatofwatervaporPv

湿空气的总压力：p=pv+pa

Theamountofdryairintheair-water-vapormixtureremainsconstant,buttheamountofwatervaporchanges.湿空气来自环境大气(pb)5-4TheAir-Water-VaporMix82

5-4-1TheSaturatedAirandUnsaturatedAirThepartialpressureofthewatervapor（水蒸气分压力）——theamountofwatervaporintheair1.TheUnsaturatedAirUnsaturatedairisamixtureofdryairands