第七章湿空气ppt课件.ppt

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1、Chapter7.MoistAir(第７章　湿空气）7.1Introduction(介绍)7.2PropertiesofMoistAir（湿空气的参数）7.3H-dDiagramofMoistAir（湿空气的H-d图)7.4ThermodynamicProcessofMoistAir（湿空气的热力过程）湿空气＝（干空气＋水蒸气）空调、通风、烘干、冷却塔、储存湿空气与一般理想混合气体的最大区别是：水蒸气的成分可能变化。分压低理想混合气体DryairAtmosphericair7.1Introduction(介绍)１．DefinitionofAtmosph

2、ericAir（湿空气的定义）Dryair+Watervapor(Moisture)=AtmosphericAir(含有水蒸汽的空气称为湿空气。)Airthatcontainsnowatervaporiscalleddryair.(完全不含水蒸汽的空气称为干空气。)2.CharacteristicsofMoistureAir(湿空气的特点)Atmosphericaircontainsaverysmallamountofwatervapor.Thepartialpressureofwatervaporisverylowsothatwatervaporint

3、heatmosphericairisalwaysatsuperheatedstate.Thus,watervaporcanbetreatedasidealgas.(湿空气中水蒸汽含量很小，分压力很低，常处于过热状态，可以当作理想气体来处理。)Atmosphericaircanbetreatedasabinarymixture(二元混合物）ofidealgases,dryairandmoistureRda=8314.41/28.9645=287.055J/(kg·K)Rw=8314.41/18.01528=461.520J/(kg·K)Dryair:pda

4、V=mdaRdaTWatervapor:pwV=mdaRwT饱和蒸汽(1)未饱和湿空气(UnsaturatedAir):Dryair+Superheatedwatervapor过热蒸汽水蒸气干空气＋过热水蒸气pv

5、和饱和水蒸汽的混合物。)饱和湿空气(3)从未饱和到饱和的途径TspvpsA.T加水蒸气,pvabC.pv不变，TabaddcB.pv，TacD.vaee结露Td露点温度7.2湿空气的参数PropertiesofMoistAirThebarometricpressureofatmosphericairvaryconsiderablywithaltitudeaswellaswithlocalgeographicandweatherconditions.1.Pressureofatmosphericair-500107.4780101.32550095.461

6、100089.875150084.556200079.495250074.682300070.108400061.640500054.020600047.181700041.061800035.600900030.7421000026.4361200019.2841400013.786160009.632180006.556200004.328Thepartialpressureofwatervaporisalsocalledvaporpressure.2.干球温度(Dry-bulbtemperature)Itisthetemperatureofmois

7、tair.Thedry-bulbtemperatureofwatervaporanddryairisthesame.Itisdenotedas‘t’.3.露点温度(Dew-pointTemperature)Itisdefinedasthetemperatureatwhichcondensationbeginswhentheairiscooledatconstantpressure.Inotherwords,itisthesaturationtemperatureofwatercorrespondingtothevaporpressure.结露:A点表示未

8、饱和湿空气中水蒸汽的状态，若保持空气中水蒸汽的含量（pv）不变，降低温度，使之达