大连理工大学：《工程热力学》课程教学资源（PPT课件）4 气体与蒸汽的热力过程 Thermodynamic Process of Gas & Vapor

4 Thermodynamic Process of Gas & VaporObjectiveThermodynamic Process of Ideal-GasThermodynamic Process of Vapor and HumidityAirThrottlingProcessAnalysisThermodynamic Process for Typical Devices

4 Thermodynamic Process of Gas & Vapor Objective •Thermodynamic Process of Ideal-Gas •Thermodynamic Process of Vapor and Humidity Air • Throttling Process Analysis • Thermodynamic Process for Typical Devices

Thermodynamic Process of Ideal-GasObjective·Process Equation: Given Initial PropertiesOtherFinalOnes· Process Equation + Given Final Properties→OtherFinal Ones·EnergyTransfer During Process

Thermodynamic Process of Ideal-Gas Objective • Process Equation • Given Initial Properties Other Final Ones • Process Equation + Given Final Properties Other Final Ones • Energy Transfer During Process

Thermodynamic Process of Ideal-GasReview: 1st Law of Thermodynamicsq= u+wq = △h + w,w= w, +△(pv) w :W.=*1=W.+=△c-g4z一W.S2 State Equation of Ideal-GaspV=RT

Thermodynamic Process of Ideal-Gas Review • 1st Law of Thermodynamics 2 2 1 1 2 ( ) d d 1 2 t t t t s q u w q h w w w pv w p v w v p w w c g z                    • State Equation of Ideal-Gas pv  RT

ThermodynamicProcessAnalysisIsovolumetricProcessThe Volume of gas is unchanged during processProcessEquationdv=0v = ConstV = ConstRelationshipBetweenInitial&FinalStateP2 _ TpiTc,dTh, -h :.C.dT-=dTST

Thermodynamic Process Analysis • Isovolumetric Process The Volume of gas is unchanged during process. Process Equation d Const V Const v 0 v    Relationship Between Initial & Final State 2 2 1 1 2 2 1 1 2 2 1 1 2 2 1 1 d d d p v v p T p T h h c T u u c T T s s c T          

Thermodynamic Process AnalysisIsovolumetric Processp2out1Lout22'EnergyTransfer1q= u+w= u=uz-u,定容过程中工质不做膨胀功，它吸收的热量全部用于增加其内能

Thermodynamic Process Analysis • Isovolumetric Process p v 1 2 2’ Qin Qout T s 1 2 2’ Qin Qout Energy Transfer d 2 1 2 1 w p v q u w u u u          定容过程中工质不做膨胀功，它吸收的热量全部用于 增加其内能

Thermodynamic Process AnalysisIsotonicProcessThe Pressureof gas is unchanged during processProcessEquationp=ConstRelationship Between Initial & Final State2_TyTc,dTc,dTuz.-u=dTCpT

• Isotonic Process The Pressure of gas is unchanged during process. Process Equation Relationship Between Initial & Final State Thermodynamic Process Analysis p  Const 2 2 1 1 2 2 1 1 2 2 1 1 2 2 1 1 d d d p v p v T v T h h c T u u c T T s s c T          

Thermodynamic Process AnalysisIsovolumetricIsotonic ProcessLineTp2'21IsotonictoutQinLineD12SIsovolumetricProcessTdTdTds = cdsTCv定压线斜率小于IsotonicProcess定容线斜率TdTdTds =CPdsTCP

Thermodynamic Process Analysis • Isotonic Process p v 2’ 1 2 Qout Qin T s 1 2 2’ Q Qin out Isovolumetric Line Isotonic Line Isovolumetric Process d d v T s c T  d d v T T s c  Isotonic Process d d p T s c T  d d p T T s c  定压线斜率小于 定容线斜率

ThermodynamicProcessAnalysisIsotonic ProcessEnergyTransfer pdv= p(v2 -v) = R(T, - T)W=, vdp = 0二q= △u + w= h + w, = h, - h定压过程中，气体的技术功为零；其膨胀功全部用于维持流动所必须的流动净功；工质吸收的热量等于其烩增量

Thermodynamic Process Analysis • Isotonic Process Energy Transfer 2 2 1 2 1 1 2 1 2 1 d ( ) ( ) d 0 t t w p v p v v R T T w v p q u w h w h h                  定压过程中，气体的技术功为零；其膨胀功全部用于 维持流动所必须的流动净功；工质吸收的热量等于其 焓增量

ThermodynamicProcessAnalysisIsothermalProcessThe Temperatureof gas is unchanged during processProcessEquationT = ConstRelationshipBetweenInitial&FinalStatePiV = p2V2h, =huz =uiS2 - S; = Rln 2 = -R ln P2PiV1

Thermodynamic Process Analysis • Isothermal Process The Temperature of gas is unchanged during process. Process Equation Relationship Between Initial & Final State 1 1 2 2 2 1 2 1 2 2 2 1 1 1 ln ln p v p v h h u u v p s s R R v p        T  Const

Thermodynamic Process AnalysisIsothermalProcessp2Qout2QinQinQLout2

Thermodynamic Process Analysis • Isothermal Process p v 2’ 1 2 Qout Qin T s 1 2 2’ Qin Qout