Psychrometric-Chart-中文讲义

4.PsychrometricChart:1weekCompositionofHumidAir()DryAir()andWaterVapor()TW250C,50%度W=0.01kgH2O/kgdryair250C,50%度W=0.01kgH2O/kgdryairHumidityRatio(度,W)„度=W=ms/ma=kgofwatervapor/kgofdryair=(psV/RsT)/(paV/RaT)=(ps/pa)/(Rs/Ra)=[ps/(pt-ps)]/(Rs/Ra)=[ps/(pt-ps)]/(Ma/Ms)=(0.622)[ps/(pt-ps)]Note:理pV=(m/M)RuT=m(Ru/M)T=mRTRu=8.3143(J/gmole-K)=數Ma=28.97(g/gmole)=量Ms=18.015(g/gmole)=量pt==101.325kpa(ps)t(0.622)()(0.622)()101.325wherep=101.325kpa=atmospheri()()()(101.325)0.6220.6cpressure,22sststssWWpppWpppHencepWW===+−+=−度冷„度=φ=/度力=ps/ps,sat:W=(0.622)[ps/(pt-ps)]Wsat=(0.622)[ps,sat/(pt-ps,sat)]„度=φ=[W(pt-ps)]/[Wsat(pt-ps,sat)]≈(W/Wsat)Note:ptps,satRelativeHumidity(度,φ)SpecificEnthalpyofHumidAir(h)h=cpt+Whgwherehg=specificenthalpyofsaturatedwatervaporattcp=1.0kJ/kg-Kdryairt=dry-bulbtemperature(度)不!TWLinesofconstantspecificenthalpySpecificVolume(v)-101.325aaaatssRTRTRvppTpp===−−Wet-Bulbtemperature(度)度sumpSump(度-t2)量(Basedon):h2=h1+hf(W2-W1)hf=(h2-h1)/(W2-W1)hf度(t2)(state”1”度Straight-LineLaw–律Whenairistransferringheatandmass(water)toorfromawettedsurface,theconditionoftheairshownonapsy-chrometricchartdrivestowardthesaturationlineatthetemperatureofthewettedsurface.wettedsurface!!冷Lewisrelationship度異ApproachII:h1=h2-hf(W2-W1)=89.7–(117.3)(0.0241-0.019)=89.1(kJ/kg)ApproachI:h1=89(kJ/kg)Wet-BulbThermometer(度)律TWWetted-surfacetemperature量:h2=h1+hf(W2-W1)wet-bulbtemperature!Wetted-surfacetemperaturewet-bulbtemperature!Processes–SensibleHeatingorCooling(冷)冷Processes–Humidification()Processes–CoolingandDehumidificationProcesses–ChemicalDehumidification()Processes–Mixing()量::w1h1+w2h2=(w2+w1)h3量::w1W1+w2W2=(w2+w1)W3量kg/sDryAirHomework2(2)„3-4„3-6„3-8