Process in T-v diagramP=c:T=20→>300C;vis increasingState1:subcooledliquid（过冷液体，未饱和液体）（liquid，P=const,T<Tsat)State2:saturatedliquid（饱和液体）（liquid,P=const,T=Tsat）State3:saturatedliquid-vapormixture（湿饱和蒸汽）（liquid+vapor,P=const,T=Tsat）State4:saturatedvapor（干饱和蒸汽）（vapor,P=const,T=Tsat)State5:superheatedvapor（过热蒸汽）(vapor,P=const,T>Tsat)T,℃300Superheatedvapor3100SaturatedmixtureSubcooledliquid20
Process in T-v diagram • P=c; T=20℃→300℃; v is increasing – State 1: subcooled liquid (过冷液体，未饱和液体) (liquid, P=const, T<Tsat) – State 2: saturated liquid（饱和液体）(liquid, P=const, T=Tsat) – State 3: saturated liquid-vapor mixture （湿饱和蒸汽）(liquid+vapor, P=const,T=Tsat) – State 4: saturated vapor（干饱和蒸汽）(vapor, P=const, T=Tsat) – State 5: superheated vapor （过热蒸汽）(vapor, P=const, T>Tsat) 20- 100- 300- T, ℃ v . 1 2 . 3 . . 4 . 5 Subcooled liquid Saturated mixture Superheated vapor 11
TABLE3-1Saturation(boiling)pressureofwateratvarioustemperaturesP sa(饱和压力)and Tsat(饱和温度)SaturationTemperature,pressure,T,℃Psat, kPa-100.26-50.40Saturationtemperature:temperature00.6150.87startingto changephase at given P101.23151.71Saturationpressure:pressurestarting202.34253.17to changephaseatgivenT304.25407.39all know:水的沸点是100℃,在一个大5012.35100101.4气压下;150476.2155520099.97C@101.325kPa25039763008588100@101.42kPaTABLE3-2Boiling temperature of water on theVariation of the standardatmosphericpressureand themountainis < 100 C , because of P<boiling (saturation)temperature ofwater with altitude1atmAtmospheric BoilingElevation,tempera-pressure,kPamture,"C0101.33100.01,00089.5596.5Saturationtablesforwaterare2,00079.5093.35,00054.0583.3available. (A-4,A-5)10,00026.5066.35.5320.00034.71270.22884832.85
Psat(饱和压力) and Tsat(饱和温度) • Saturation temperature: temperature starting to change phase at given P • Saturation pressure: pressure starting to change phase at given T. • all know: 水的沸点是100℃, 在一个大 气压下; – 99.97℃@101.325kPa – 100℃@101.42kPa • Boiling temperature of water on the mountain is < 100 ℃ , because of P< 1atm • Saturation tables for water are available. (A-4, A-5) 12 8848 32.85 70.22
Latent heat during phase changeLatent heat(潜热): energy absorbed or releasedduring a phase-change process. Latent heat of fusion: melting and freezing. E.g:333.7kJ/kg forwater @1atm Latent heat of vaporization (hfq) : vaporizationandcondensation.E.g:2256.5kJ/kgforwater@1atm
Latent heat during phase change • Latent heat(潜热): energy absorbed or released during a phase-change process • Latent heat of fusion: melting and freezing. E.g: 333.7kJ/kg for water @1atm • Latent heat of vaporization (hfg) : vaporization and condensation. E.g: 2256.5kJ/kg for water @1atm 13
（饱和曲线）Saturation CurveLiquid-vapor saturation curve- Tsat=f(Psat)This curve can be made from data inPar,kPatable 3-1, or Table A-4,A-5600Higher pressure, higher temperature400200Pressure cooker(高压锅)。Psat个200...C50100150Tsat ↑, Time ↓, Energy ↓, ￥ ↓放气孔和安全韵易塔片a锅身特熟食物高压锅的结构
Saturation Curve （饱和曲线） • Liquid-vapor saturation curve – Tsat=f(Psat) • This curve can be made from data in table 3-1, or Table A-4, A-5 • Higher pressure, higher temperature • Pressure cooker(高压锅) 。Psat ↑, Tsat ↑, Time ↓, Energy↓, ￥↓ 14
Some examples of Tsat=f(Psat)R134a: Tsat=-26C@1atm。Used in refrigerators.·Nitrogen: Tsat=-196 C @1atm。N,vapor-196°℃CTestchamhe196°℃25°℃LiquidN,196°InsulationVacuum cooling/freezing:: Tsat=0 C @0.61kPaPackage icing: absorb the latent heat of fusion15
Some examples of Tsat=f(Psat) • R134a: Tsat=-26℃@1atm。 Used in refrigerators。 • Nitrogen: Tsat=-196 ℃ @1atm。 • Vacuum cooling/freezing：Tsat=0 ℃ @0.61kPa • Package icing: absorb the latent heat of fusion 15