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1、Definition of Atmospheric Air（湿空气的定义）Dry air+Water vapor(Moisture)=Atmospheric Air(含有水蒸汽的空气称为湿空气。)Air that contains no water vapor is called dry air.(完全不含水蒸汽的空气称为干空气。)2.Characteristics of Moisture Air(湿空气的特点)Atmospheric air contains a very small amount of water vapor.The partial pressure of water va
2、por is very low so that water vapor in the atmospheric air is always at superheated state.Thus,water vapor can be treated as ideal gas.(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。)第1页/共41页 Atmospheric air can be treated as a binary mixture(二元混合物）of ideal gases,dry air and moisture Rda=8314.41/28.9645=287
3、.055J/(kgK)Rw=8314.41/18.01528=461.520J/(kgK)Dry air:pdaV=mdaRdaTWater vapor:pwV=mdaRwT第2页/共41页饱和蒸汽(1)未饱和湿空气(Unsaturated Air):Dry air+Superheated water vapor过热蒸汽水蒸气干空气过热水蒸气pv ps(T)Tspvps加入水蒸气，pv3.Saturated Air and Unsaturated Air(未饱和空气和饱和空气)未饱和湿空气第3页/共41页(2)饱和湿空气(Saturated air)干空气饱和水蒸气pv ps(T)Tsps温度
4、一定，不能再加入水蒸气Saturated Air:Dry air+Saturated water vapor(饱和湿空气：干空气和饱和水蒸汽的混合物。)饱和湿空气第4页/共41页(3)从未饱和到饱和的途径TspvpsA.T 加水蒸气,pvabC.pv 不变，Ta ba ddcB.pv ，Ta cD.va ee结露Td 露点温度露点温度第5页/共41页7.2 湿空气的参数Properties of Moist Air The barometric pressure of atmospheric air vary considerably with altitude as well as with
5、 local geographic and weather conditions.1.Pressure of atmospheric air第6页/共41页-500107.4780101.32550095.461100089.875150084.556200079.495250074.682300070.108400061.640500054.020600047.181700041.061800035.600900030.7421000026.4361200019.2841400013.786160009.632180006.556200004.328第7页/共41页lThe partial
6、pressure of water vapor is also called vapor pressure.2.干球温度 (Dry-bulb temperature)It is the temperature of moist air.The dry-bulb temperature of water vapor and dry air is the same.It is denoted as t.3.露点温度(Dew-point Temperature)It is defined as the temperature at which condensation begins when the
7、 air is cooled at constant pressure.In other words,it is the saturation temperature of water corresponding to the vapor pressure.第8页/共41页结露:A点表示未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，使之达到pv对应的饱和温度ts，则湿空气成为饱和湿空气，为点B。若继续降温，水分析出，称为结露。露点:B点所对应的pv下的饱和温度成为露点，用td表示。第9页/共41页4.相对湿度(Relative Humidity of Air)定义
8、：湿空气中实际包含的水蒸汽量与同温度下最多能包含的水蒸汽量的百分比。The relative humidity is defined as the ratio of the amount of moisture in the air to the maximum amount of moisture the air can hold at the same temperature.If we use“a”、“v”、“s”denoting dry air,water vapor and saturated water vapor respectively,then(若用下标“a”、“v”、“s”
9、表示干空气、水蒸汽和饱和水蒸汽的参数，则有：)第10页/共41页 1 饱和湿空气(Saturated Moist Air)在相同的温度下：0 干空气(dry air)0 tw tdDry-bulb,Wet-bulb and Dew Point temperature第20页/共41页7.3 湿空气的焓湿图The Psychrometric Chart(h-d图)Saturation Line(饱和湿空气线）In addition,there are other lines(还有下列曲线：）1.Lines of constant enthalpy(定焓线，与y轴成45oC角向下)2.Lines
10、of constant humidity ratio(定含湿量线，垂直直线)3.Lines of constant temperature (定温线)4.Lines of constant volume(定容线)5.Lines of constant relative humidity line(定相对湿度线。)6.Lines of constant pv和d.(水蒸汽分压力pv和d关系曲线)第21页/共41页1.1.焓湿图焓湿图的的结构结构d=0 干空气dh(2)h 线(1)d 线 人为将 h 旋转135度 h135度第22页/共41页1.1.焓湿图焓湿图的的结构结构dh(3)t 线 正斜率
11、的直线 h等干球温度线t第23页/共41页1.1.焓湿图焓湿图的的结构结构dhht(4)线ts=99.63oCd第24页/共41页1.1.焓湿图焓湿图的的结构结构dhht(5)线d第25页/共41页1.1.焓湿图焓湿图的的结构结构dhht(6)露点 tdpv下饱和湿空气td第26页/共41页1.1.焓湿图焓湿图的的结构结构dhht(7)湿球温度tw绝热饱和温度tdtwt第27页/共41页(8)等热湿比线Process Line for Air Conditioned SpaceThe room process line,known also as room ratio line(RRL)is
12、defined by the condition of supplied air and the desired air condition in the space.The RRL is dependent on both sensible and latent heat load.1.焓湿图的结构第28页/共41页dhht热湿比h-d图上为直线:角系数：过程方向与特征第29页/共41页dhht12已知初态1过程斜率已知可确定终态第30页/共41页twtd不同的B不同的h-d图第31页/共41页7.4 湿空气的热力过程（Thermodynamic Process of Moist Air）1
13、.Sensible Heating Process(单纯单纯加热过程)Sensible Heating Process is a process during which Sensible Heating Process is a process during which the dry-bulb the dry-bulb temperature of air is increasedtemperature of air is increased.The process occurs The process occurs at constant moisture contentat const
14、ant moisture content.The air passes over a hot and dry surface which might be pipe The air passes over a hot and dry surface which might be pipe coil using steam or hot water,electrical resistance or an air-to-air coil using steam or hot water,electrical resistance or an air-to-air heat recovery uni
15、t.heat recovery unit.The load on the heater is:The load on the heater is:BA 加热过程第32页/共41页2.Sensible Cooling Process at Constant Moisture Content(单纯冷却过程)Sensible cooling process at constant moisture content is aprocess during which the dry-bulb temperature of air is decreased.If the temperature of th
16、e cooling medium is still above its dew point temperature,then(若冷却介质温度没有降到露点以下，则过程前后)：AB冷却过程The air passes over a cooling coil which uses chilled water or direct expansion of some refrigerant into the pipe coil.第33页/共41页If the air is continuously cooled to a temperature which below its dew-point tem
17、perature,then water vapor will condense.(温度下降到露点以后，继续降温，析出水分，减小含湿量。)CAB3.Sensible Cooling with Dehumidification(冷却去湿)第34页/共41页4.Humidification Process(加湿过程)由于水的焓值很小，可以忽略不计，所以可以看作加湿之后焓不变，在h-dh-d图上是沿着定焓线向d d增大的方向进行（过程1-21-2）。(1)Adiabatic Humidification Process(绝热加湿过程)第35页/共41页(2)Isothermal Humidificat
18、ion Process(等温加湿)第36页/共41页5.Mixing of Two Air Streams(混合过程)第37页/共41页例题例题(Example)dh12已知空气的t1=20oC，p1=0.1MPa将其加热至t2=50oC，后送入干燥室，从干燥室排出时t3=30oC，求：1）2）从干燥室每吸收1kg水分所需空气量和加热量h2h13第38页/共41页Solution:dh12h2h13根据t1=20oC，p1=0.1MPa，查图d1=8.9g水蒸气/kg(d.a.)h1=42.8kJ/kg(d.a.)根据d2=d1,t2=50oC查图h2=73.5kJ/kg(d.a.)根据h3=h2,t3=30oC查图d3=17.0g水蒸气/kg(d.a.)第39页/共41页dh12h2h13含1kg干空气的湿空气所吸收水分每吸收1kg水分所需干空气每吸收1kg水分所需湿空气每吸收1kg水分所需加热量第40页/共41页感谢您的观看！第41页/共41页