Solutions to 2传质与分离工程(双语)考试题

《传质与分离工程《传质与分离工程（双语）》试卷A第#页共7页x=0y=0.016aby=0.004aV=0.062x=0y=0.016aby=0.004aV=0.062kmol/hL=2.2kmol/hByamaterialbalance,L(x-x)=V(y-y)babatx=0.000338by*a•/y*b・•・y*b=mxa=mxb=35.48x0.000338=0.01199...S=罕=血4：：062=1,AT=(y-y*)=(y-y*)=0.004L22Lbbaa2.2N=儿-L二…二3oyAyL(b)FromZ=HNToyoyZ=HNTHToyoyoy=厶=35=1.167mN3oy(c)口V/S(c)•/H=oyKay“V/S0.062/3600nO/1inz”Ka===9.84x10-6kmol/m3-syH1.5x1.167oy(18points)Somekindofwetsolidsisdriedinacontinuousdryerunderatmosphericpressure.Theoperationconditionsaregivenasfollows:Statesofair:Attheinletofthepre-heater,Airtemperatureandhumidityare:t=20。C,and0H0=0.01kgwatervapor/kgdryair,respectively.Attheinletofthedryer,t=120。C.1

Attheoutletofthedryer,t=70oC,H=0.05kgwatervapor/kgdryair.

22Statesofwetsolids:Attheinletofthedryer,0=3OoC,w=20%(wetbasis).11Attheoutletofthedryer,0=500C,w=5%(wetbasis).22Specificheatofbone-drysolids,C=1.5kJ/kg-0C.sThemassflowrateoffinalmoistsolids(product)is53.5kg/h.Calculate:MassflowrateofdryairL,kgdryair/h;HeattransferrateinputintothepreheaterQP,kJ/h;SupplementaryheattransferrateintothedryerQD,kJ/h.Assumethatheatlossesofthedryingequipmentcanbeomitted.Solution.(1)x10.21-0.2=0.251-(1)x10.21-0.2=0.251-~20.051-0.05=0.0526G2=53.5kg/hG=G(1-w)22W=L(H-H)=G(X-X)20c12:.L=250.75kgdryair/hQ=L(I-I)=LC(t-t)P10H010I=(1.01+1.88H)t+2490H0000I=(1.01+1.88H)t+2490H1111H=H10:Q=25797.16kJ/hP(3)20Q=Q+Q=L(I-1)+G(I'-1')+Q20PDTakeQ=0L•••I=C0,I'