流体力学与传热习题参考解答(英文).doc

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1、.1.Waterispumpedataconstantvelocity1m/sfromlargereservoirrestingonthefloortotheopentopofanabsorptiontower.Thepointofdischargeis4meterabovethefloor,andthefrictionlossesfromthereservoirtothetoweramountto30J/kg.Atwhatheightinthereservoirmustthewaterlevelbekeptifthep

2、umpcandeveloponly60J/kg?U1=0W=60j/kg2.Thefluid(density1200kg/m3)ispumpedataconstantrate20m3/hfromthelargereservoirtotheevaporator.Thepressureabovethereservoirmaintainsatmospherepressureandthepressureoftheevaporatorkeeps200mmHg(vacuum).Thedistancebetweenthelevelof

3、liquidinthereservoirandtheexitofevaporatoris15meterandfrictionallossinthepipeis120J/kgnotincludingtheexitofevaporator,whatisthepumpeffectiveworkandpowerifthediameterofpipeis60mm?Word资料.3.Watercomesoutofthepipe(Φ108x4mm),asshowninFig.Thefrictionlossofthepipelinewh

4、ichdoesnotcoverthelossattheexitofpipecanbecalculatedbythefollowingequation:hf=6.5U2whereUisthevelocityinthepipe,finda.watervelocityatsectionA-A'.b.waterflowrate,inm3/h.4.Waterpassesthroughthevariablepipe.Thevelocityinthesmallpipeis2.5m/s.Theverticalglasstubesarei

5、nsertedrespectivelyatthesectionAandBtomeasurethepressure(seefig.)Ifthefrictionlossbetweentwosectionis15J/kg,whatisthewatercolumndifferencebetweentwoglasstubes?Bytheway,drawtherelativeliquidcolumnheightoftwotubesintheFig.Word资料.5.Acentrifugalpumptakesbrine(density

6、1180kg/m3,viscosity1.2cp)fromthebottomofasupplytankanddeliversitintoanothertank.Thelinebetweenthetanksis300mof25mmdiameterpipe(innerdiameter).Theflowrateis2m3/h.Inthisline,therearetwogatevalves,fourelbows(90o)andonereturnbend,whatisthefrictionlossiftheroughnessof

7、pipeis0.025mm?Word资料.6.Theorificemeter(diameteroforifice0.0001m)isinstalledformeasuringtheflowrate.TheindicatingliquidoforificeismercuryifUshapepressuregaugereadingis0.6meterandorificecoefficientcanbetakenas0.61,whatistheflowrateofwater?7.Waterflowsthroughapipewi

8、thadiameterdi100mmasshowninfigure.a.whenthevalveisclosed,Ris600mmandhequals1500mm.Whilethevalveopenspartially,R=400mmandh=1400mm,f=0.00625(Finningfactor)andkc=