有机无机化学化工热力学教学课件流体输送

18.Multistagecentrifugalpumps

9.Leakproofpumps

10.Pumppriming泵的起动注水(affusion)**11.Pipingsystemcharacteristiccurve**12.Operatingpoint(Dutypoint)**13.Flowratecontrol**14.PumpSelection第一页，共47页。2qH(a)(b)pP:operatingpoint(a)Ｈe＝K＋Bqe2(b)H=A-Bq212.Operatingpoint(Dutypoint)第二页，共47页。313.FlowratecontrolUsuallythevalveonthedischargelineisusedtocontrolcapacityofacentrifugalpump.Themethodofadjustmenttheflowrate:(1)Changecharacteristiccurveofflowsystem.(2)Changecharacteristiccurveofthepump.(3)Connecttwopumps第三页，共47页。4(1)Changecharacteristiccurveofflowsystem.KBqe2第四页，共47页。5Exercise1:200Cwaterispumpedfromanopentanktoaclosedvesselwithflowrate45m3/h.Thewaterleveldifferencebetweenthetankandthevesselis14m.Thegaugepressureinvesselis49kPa.ThesizeofthepipelineisФ140×4.5mmdiameterand200mlength(allkindsoffrictionlossareincluded),thefrictionfactorλis0.02.(1)Calculatetheequationofpipelinehead-capacitycurve.第五页，共47页。6(2)

Ifacentrifugalpump,whichhashead-capacitycurve:H=26-5.6×10－4Q2(Qisin‘m3/h’,andHisin‘m’.)isusedinthesystem,andthevalveonthedischargelineneedtobepartiallyclosedtomaintaintheflowrateat45m3/h.Calculatethenewhead-capacitycurveequationofpipelineafterthevalveispartiallyclosed.(3)Calculatethepowerlossduetothepartiallyclosingvalve(assumepumpefficiencyis70%).

第六页，共47页。7(2)Changecharacteristiccurveofthepump.第七页，共47页。8(3)Connecttwopumps----inparallel第八页，共47页。9第九页，共47页。10(3)Connecttwopumps----inseries第十页，共47页。11第十一页，共47页。12ComparethetwokindofconnectingmannerLowfrictionlossHighfrictionloss第十二页，共47页。13Exercise2.Thecharacteristiccurveequationsofakindofcentrifugalpumpsis:Thepipelinecharacteristiccurveequationis:Twosamepumpisusedinordertomaketheflowrateasmoreaspossible.Calculate:howtoconnectthetwopumps(parallelorseriesconnecting)isbetter?(Q:m3/h,H:m)（Qe:m3/h,He:m）第十三页，共47页。1414.PumpSelectionSelectfrommanufacturers'catalogs.TypeofpumpTypeofpumpisselectedaccordingtothepropertiesoffluid.(b)SizeofpumpDeterminedbydevelopedheadandcapacityrequirements.(c)Checkpower第十四页，共47页。15第十五页，共47页。16第十六页，共47页。17第十七页，共47页。18第十八页，共47页。19Anexampleofmanufacturers'catalogs第十九页，共47页。20Howtostartingandstoppingapumpproperly?第二十页，共47页。21第二十一页，共47页。22Primethepumporconfirmthatthepumpcasingisfulloftheliquid.2.Startpumpwithdischargevalveclosed.Statingapump:Stoppingapump:Closethedischargevalve,whilethepumpisinoperation.2.Stopthepumpimmediatelyafterclosingthedischargevalve.第二十二页，共47页。23Review1.Centrifugalpump2.Performancecharacteristicsandcharacteristiccurves3.Variationofpumpcharacteristiccurves4.PipingsystemcharacteristiccurveandOperatingpoint(Dutypoint)5.Flowratecontrol6.Howtoselectapumpandoperatethepumpcorrectly.(airbound,cavitation)第二十三页，共47页。248.4Fans,Blowersandcompressors1.Fans2.Blowersandcompressors3.Comparisonofdevicesformovingfluids第二十四页，共47页。25Fans(通风机):lowpressuresontheorderof0.04atmBlowers(鼓风机):amaximumpressureofabout2atmCompressors(压缩机):from2atmtoseveralthousandatmospheresVacuumpumps(真空泵)Thedevicesusedtotransportandcompressgases.第二十五页，共47页。261.Fans(a)StructureofafanCentrifugalfan2-13第二十六页，共47页。27Impellerofthefan第二十七页，共47页。28(b)Characteristicparametersofafan(1).Standardcubicfeet,q,ft3/horm3/h风量Themostcommonstandard:Pressureof30in.Hg(762mmHg)Temperatureof60F(15.56℃)Correspondingamolalvolumeof378.7ft3/lbmol中文教材：进口状态。第二十八页，共47页。29(2).Fantotalhead(fantotalpressure),HT,J/m3,PaorN/m2.全风压BernoulliequationusuallyexpressasfollowingJ/m3,PaFantotalpressureisafunctionofdensity.第二十九页，共47页。30(3).Shaftpower,WorkW轴功率(4).Efficiency,效率η第三十页，共47页。31第三十一页，共47页。32(c)Fanselection(1)Typeoffan(2)Sizeoffan(3)Checkpowerifgasdensityislargerthan1.2kg/m3.EXAMPLE8.2.第三十二页，共47页。332.BlowersandCompressor☆(1).Positive-displacementblower☆(2).Centrifugalblower(3).Positive-displacementcompressor☆(4).Centrifugalcompressor(5).Equationforblowersandcompressors(6).Vacuumpumps第三十三页，共47页。34(3).Positive-displacementcompressor第三十四页，共47页。35(5).Equationsforblowersandcompressors(a)theworkofcompressionofanidealfrictionlessgas

理想压缩循环：吸气阶段：4——1压缩阶段：1——2排气阶段：2——3第三十五页，共47页。36Adiabaticcompression(绝热压缩）(8.27)Compressionratio第三十六页，共47页。37Isothermalcompression（等温压缩）

k=1(8.29)第三十七页，共47页。38Polytropiccompression（复杂压缩）

k=nUsingEq.(8.27)withthereplacementofbyn

Usually1<n<γ（8.27）第三十八页，共47页。39(b)Actualcompressionprocess实际压缩循环：吸气阶段：4——1压缩阶段：1——2排气阶段：2——3膨胀阶段：3——4第三十九页，共47页。40Clearancefactor余隙系数Capacityfactor容积系数Compressionratio第四十页，共47页。41(c)Compressorefficiency

Theratioofthetheoreticalwork(orfluidpower)totheactualwork(ortotalpowerinput)

第四十一页，共47页。42(d)PowerequationAnadiabaticcompressor

WherePB=power,kWqo=volumeofgascompressed,stdm3/s,evaluatedat0