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