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1、Chapter8Steamandcondensatesystems￠p=C￠1=2?v2(22)a;p3l0￠p=k?U2(1+nM)(23)b;ppll￠p=3￠1=2?U2(1+M)(1+nM)(24)c;pllC=1+M[1+E2ln(1+1=E2)](25)1+nME=Ul(1+nM)(26)v0whereΔppispressurelossinarotarysiphonΔpa,ppressurelosscausedbycentrifugalforceΔpb,ppressurelosscausedbyaccelerationofconde
2、nsateΔpc,ppressurelosscausedbyflowresistancenρl/ρhM_mh/_mlρldensityofcondensateρhdensityofsteamm_lmassflowofcondensatem_hmassflowofsteamUlcondensatespeedinthesiphon,if_mh=0v0circumferentialspeedofdryerkpexperimentalcoefficient(kp>>ks>1)ζresistancecoefficientofthesiphon.Thisa
3、pproachiscomplicatedandhastobecombinedwithexperimentalvalues(Fig.20).Asimplifiedapproachusingtwocomponentsdescribethepressureloss7:￠pp=￠pf+￠pc(27)whereΔpfispressurelossinarotarysiphonΔpfpressurelosscausedbyflowresistanceΔpcpressurelosscausedbycentrifugalforce.Equations28and2
4、9cancalculatethepressurelosscausedbyflowresistance7:?￠￠p=￠p1+C1+1(28)flXX2qX=￠pl(29)￠phwhereΔpfispressurelosscausedbyflowresistanceΔplpressurelossifonlycondensateflowsinthepipeΔphpressurelossifonlysteamflowsinthepipeXtheMartinellinumber.Calculationofthepressurelossofahomogen
5、eousflowusesthefollowingformula9:￠p=31=2?U2(30)whereΔpispressurelossPapermakingPart2,Drying-Page150Chapter8SteamandcondensatesystemsζresistancecoefficientρdensityofflowingliquidUflowspeed.Sinceonecanassumethatcentrifugalforceprimarilyaffectsthecondensatedrops,knowingthemasso
6、fwaterinthesiphonisnecessary.Thisisobviouslynotthesameasthemassofwaterinentryandexit.Estimationusesthefollowingformula/7/:3′2?￠1=1+C1+1(31)RlXX2Thisgivesthepressurelosscausedbythecentrifugalforceasfollows:￠p=R1/2?v2(32)cll0Figure20.Characteristiccurveofarotarysiphondependson
7、machinespeedaccordingtoEqs.21?26.Figure21.Dependenceofthecharacteristiccurveofarotatingsiphononcondensateload.Figure22.Dependenceofthecharacteristiccurveofarotatingsiphononmachinespeed.Thefollowingformulathengivesthetotalpressureloss:?￠￠p=￠p1+9:3+1+R1/2?v2(33)plXX2ll0whereΔp
8、pistotalpressurelossΔplpressurelossifonlycondensateflowsinthepipeRlshareofc
