3 ThermodynamicProperty of Gas &VaporObjective·ldeal-Gas Equation of StateHeat Capacity, Specific Heat, Internal Energy &Enthalpy: Property of Ideal-Gas and Its Mixture·Real-Gas&Derivation from ldeal-Gas· Property Diagrams of Phase-Change process forPure SubstancesThermodynamic property of humidity air (moisture)1
1 3 Thermodynamic Property of Gas & Vapor Objective •Ideal-Gas Equation of State •Heat Capacity, Specific Heat, Internal Energy & Enthalpy • Property of Ideal-Gas and Its Mixture • Real-Gas & Derivation from Ideal-Gas • Property Diagrams of Phase-Change process for Pure Substances •Thermodynamic property of humidity air (moisture)
Ideal-Gas Equation of StateFrom a molecular standpoint, an ideal gas moleculeis a completely elastic, point particle (no volume)withno molecule-molecule interaction forcesECondition:GASIDEAIoto·lowpressure10MP30060.05MP·high temperature00MP:100PO10kP0.skPs200040.0100.1tmks100
2 Ideal-Gas Equation of State From a molecular standpoint, an ideal gas molecule is a completely elastic, point particle (no volume) with no molecule-molecule interaction forces. Condition: • low pressure • high temperature
Ideal-Gas Equation of StateAn equation of state is...- ...a mathematical expression that definesthe thermodynamic state of a substance andrelates volume, pressure, and temperatureThere are several equations of state. The ideal-gas equation is the simplest and best-known one.It predicts the P-v-T behavior of agas quiteaccurately within some properly selected region.3
3 Ideal-Gas Equation of State An equation of state is. – .a mathematical expression that defines the thermodynamic state of a substance and relates volume, pressure, and temperature. There are several equations of state. The idealgas equation is the simplest and best-known one. It predicts the P-v-T behavior of a gas quite accurately within some properly selected region
Ideal-Gas Equation of Statep- Absolute Pressure, kPapV= RTv- Specific Volume, m"/kgT- Absolute Temperature, KpV = mRTV-Volume, m3pV = NR.TN - Mole Number, kmolmR, -Universal Gas ConstantR, = 8.314kJ/(kmol .K)R8.314R:kJ/(kg ·K)一MMM - Molar Mass4
4 Ideal-Gas Equation of State pV NR T pV mRT pv RT = m = = 3 3 ,kPa ,m /kg ,K , m ,kmol 8.314kJ/(kmol K) 8.314 kJ/(kg K) m m m p Absolute Pressure v Specific Volume T Absolute Temperature V Volume N Mole Number R Universal Gas Constant R R R M M M Molar Mass − − − − − − = = = −
2.鼓风机需要输运2900kg/h空气，输运时空气温度为30℃，其管道上压力表读数0.3MPa，当时当地大气压力为0.1MPa，求实际送风量(m3/h)为多少？解：根据理想气体状态方程pV =NR.Tm绝对压力p = 0.3+0.1=0.4MPaT =30+273.15 =303.15KNR.T:Vp2900×8.314×303.15= 630m3/h29×4005
5 2. 鼓风机需要输运2900kg/h空气，输运时空气温度为30℃，其管道上压力表 读数0.3MPa，当时当地大气压力为0.1MPa，求实际送风量(m3 /h)为多少？ 解：根据理想气体状态方程 m pV NR T = 0.3 0.1 0.4MPa 30 273.15 303.15K p T = + = = + = 2900 8.314 303.15 3 630m /h 29 400 NR Tm V p = = = 绝对压力