山东大学：《工程热力学》课程PPT教学课件（双语）第三章 Properties of Pure Substances

Chap.2 SummaryTotal Energy.EIntemal Energy.UPotential Energy,PEKineticEnergy.KEForms of EnergyEnergyE=U+KE+PE=U+mV2/2+mgzMechanical energy,Nuclear energy,Chemical Energy,Sensible energyLatent energy,Thermal energy, Heat, Work, Flow workConvectionTemperature diffBy Heat,QConductionRadiationEnergyTransfer,Force*distanceBy Work, wForms of work:mechanical;shaft,spning,electrical,etcByMass,m=0,foraclosedsystemclosed systemQ=△U+ WEin-Eout=AEsystem1stLawofThermodynamicsEnergybalance:Ein-Eout-(Qin-Qout)+(Win-Wout)+(Emassin-Emass,out)=AEsystemEnergyChangeEffciency=desiredoutputl required inputEnergyConversionEfficiencyCombustion efficiency.Overall efficiency.effciency ofgenerator,motor,pump,turbine,etcEnergyand Environment

E=U+KE+PE=U+mV2 /2+mgz Chap.2 Summary 1 Forms of Energy Energy Transfer, E Total Energy, E Kinetic Energy, KE Potential Energy, PE Conduction Convection Radiation Effciency =desired output/ required input Ein-Eout= ∆Esystem Internal Energy,U 1st Law of Thermodynamics Energy balance: Ein-Eout=(Qin-Qout)+(Win-Wout)+(Emass,in-Emass,out)= ∆Esystem Energy Conversion Efficiency Energy and Environment Mechanical energy, Nuclear energy, Chemical Energy, Sensible energy, Latent energy, Thermal energy, Heat, Work, Flow work Energy By Heat , Q Temperature diff Forms of work: mechanical, shaft, spring,electrical, etc By Work, W Force*distance By Mass, m =0, for a closed system closed system Q=∆U+ W Energy Change: Combustion efficiency, Overall efficiency, efficiency of generator, motor, pump, turbine, etc

Chap.3 SummaryAsinglechemicalelementorcompoundAsubstancethat hasPure substanceHomogeneousmixtureofvariouschemicalelementsorcompoundsafixedchemicalcompositionmixtureoftwoormorephasesapuresubstanceCompressed liguid orsubcooled liquidliquidSaturated liquidSatruated liquid-vapor mixturePhase changeprocessSatruated vaporvaporSuperheatedvapor+Psat,Tsat,Latentheatoffusion/vaporization,sublimationsolidCritical pointSaturated liquid/vapor lineSuperheatedvaporregionT-v,P-v,P-T, P-v-T diagramsTripple pointCompressedliquid regionSaturated liquid-vapor region1Enthalpy/焰:acombinationpropertyh=u+Pv(kJ/kg);Entropy/PropertiestablesSaturated liguid/vaporormixture.ht,ha,haQualityx=[0.1]SuperheatedvaporCompressedliquid P,TReferencestatevalues1PV=RTPV=mRTR,RuIdeal gasequationofstateIdeal-gas/realgasZ=Pv/RTCompressibilityfactorReducedPReducedTequationofstateGeneralizedVanderwallsPrincipleofcorresponding statescompressibility chartequationofstate2

Chap.3 Summary 2 A substance that has a fixed chemical composition Phase change process A single chemical element or compound Enthalpy/焓: a combination property h=u+Pv (kJ/kg); Entropy/熵 Critical point T-v, P-v,P-T, P-v-T diagrams Properties tables Ideal-gas / real gas equation of state Pure substance liquid vapor solid Homogeneous mixture of various chemical elements or compounds mixture of two or more phases a pure substance Saturated liquid Satruated liquid-vapor mixture Satruated vapor Superheated vapor Compressed liquid or subcooled liquid Psat, Tsat, Latent heat of fusion/vaporization, sublimation Tripple point Saturated liquid/vapor line Superheated vapor region Compressed liquid region Saturated liquid-vapor region Saturated liquid/vapor or mixture. hf ,hg,hfg Quality x=[0,1] Superheated vapor Compressed liquid P, T Reference state/values Ideal gas equation of state Pv=RT PV=mRT R, Ru Compressibility factor Z=Pv/RT Reduced P Reduced T Principle of corresponding states Generalized compressibility chart Van der walls equation of state

Chapter 3 Properties of Pure SubstancesConcept of Pure substancePhysics of phase-change processesP-v, T-v, P-T, P-v-T diagramspropertytablesideal gas, ideal-gas equation of state

Chapter 3 Properties of Pure Substances • Concept of Pure substance • Physics of phase-change processes • P-v, T-v, P-T, P-v-T diagrams • property tables • ideal gas, ideal-gas equation of state 3

3-1 Pure Substance(纯物质): Pure Substance definition: a substance that hasafixed chemical composition.-Asinglechemicalelementorcompound:Water,nitrogen,helium, carbon dioxideHomogeneousmixtureofvariouschemicalelementsorcompounds:air (uniformchemicalcomposition)mixtureoftwoormorephasesofapuresubstance:iceandliquidwater.Mixture of liquidair and gaseous airisnot

3-1 Pure Substance (纯物质) • Pure Substance definition: a substance that has a fixed chemical composition. – A single chemical element or compound: Water, nitrogen, helium, carbon dioxide – Homogeneous mixture of various chemical elements or compounds: air (uniform chemical composition) – mixture of two or more phases of a pure substance: ice and liquid water. • Mixture of liquid air and gaseous air is not 4

3-2 Phases of a pure substance. 3 principal phases: solid, liquid, gasLiquid: groups ofSolid:moleculesatGas:moleculesmovemoleculesmovefixed positionsaboutatrandomabouteach otherC(a)0

3-2 Phases of a pure substance • 3 principal phases: solid, liquid, gas Solid: molecules at fixed positions Liquid: groups of molecules move about each other Gas: molecules move about at random 5

3-3. Phase-Change processes of pure substance Two phase processes are very popularWater in boiler: liquid and vaporWaterincondenser:liquid and vaporWaterinwinter:liquid andsolid Phase change process: Water is used to showthe basic principle.Compressedliquid-subcooledliquid（过冷液体）Saturatedliquid（饱和液体）（湿饱和蒸汽）saturatedliquid-vapor mixtureSaturatedvapor(干饱和蒸汽）Superheatedvapor(过热蒸汽）

3-3. Phase-Change processes of pure substance • Two phase processes are very popular – Water in boiler: liquid and vapor – Water in condenser: liquid and vapor – Water in winter: liquid and solid • Phase change process: Water is used to show the basic principle. – Compressed liquid –subcooled liquid (过冷液体) – Saturated liquid(饱和液体) – saturated liquid-vapor mixture （湿饱和蒸汽) – Saturated vapor(干饱和蒸汽) – Superheated vapor(过热蒸汽) 6

Heating the water at 1atm and 20°CState 1:- Water at 1atm and 20 C, only liquidState 1,compressedliquid:not aboutto vaporizeSTATE1STATE 1P=latmP=latmT=20°CT=20°CDHeat仰

Heating the water at 1atm and 20℃ • State 1: – Water at 1atm and 20 ℃, only liquid – State 1, compressed liquid: not about to vaporize 7

Heating the waterState 2:-Water at 1atm and 100 c,only liquid- State 1→ state 2.Temperatureisrisingfrom20to 100,P=1atm=c:Specific volume increases slightly,water expands slightlyState2,saturated liquid:isabouttovaporize.STATE 2STATE1P=1atmP=1atmT=100°CT=20°CAHeatAHeat4仰

Heating the water • State 2: – Water at 1atm and 100 ℃, only liquid – State 1→ state 2 • Temperature is rising from 20 ℃ to 100 ℃, P=1atm=c • Specific volume increases slightly, water expands slightly – State 2,saturated liquid: is about to vaporize. 8

Heating the waterState 3, state 4:-Waterat1atmand1o0C,phase-changeprocessState 2→ state 4,:Temperature=100℃=c,pressure=1atm=c,phase-changeprocess:saturated liquidvaporizestosaturatedvaporState4,Saturatedvapor:vaporisabouttocondenseSTATE3STATE2STATE4-SaturatedP=latmvaporP=1atmP=LatmT=100°℃SaturateT=100°T=100°Cliqui0HeatHeatHeat价0saturatedliquid-vapormixture:liquidandvaporphasescoexistinequilibrium

Heating the water • State 3, state 4: – Water at 1atm and 100 ℃, phase-change process – State 2→ state 4, • Temperature=100℃ =c, pressure =1atm=c, • phase-change process: saturated liquid vaporizes to saturated vapor – State 4, Saturated vapor: vapor is about to condense saturated liquid-vapor mixture: liquid and vapor phases coexist in equilibrium 9

Heating the waterState 5:- Water at 1atm and 300 °C, vapor only- State 4→ state 5,:Temperature is risingfrom100cto 300℃,pressure=1atm=c,·SpecificvolumeincreasesState5,superheatedvapor:vaporisnotaboutto condenseSTATESSTATE4P=1atmP=1atmT=300°CT=100°CHeatHeat010

Heating the water • State 5: – Water at 1atm and 300 ℃, vapor only – State 4→ state 5, • Temperature is rising from 100℃ to 300℃, pressure =1atm=c, • Specific volume increases – State 5, superheated vapor: vapor is not about to condense 10