南师大锅炉原理课件3-3 锅炉热平衡的组成及锅炉效率.pptx

2025/6/2113.3Boilerheatbalanceandboilerefficiency

§3-3锅炉热平衡的组成及锅炉效率锅炉热平衡是研究燃料的热量在锅炉中利用的情况，有多少被有效利用，有多少变成了热量损失，这些损失又表现在哪些方面以及它们产生的原因。热平衡目的是为了有效地提高锅炉热效率。锅炉热效率是锅炉的重要技术经济指标，它表明锅炉设备的完善程度和运行管理的水平。提高锅炉热效率以节约燃料，是锅炉运行管理的一个重要方面。锅炉的热平衡(或热效率)试验是为了全面评定锅炉的工作状况。通过测试分析影响锅炉热效率的因素，得出较先进的运行经验数据，作为设计锅炉和改进运行的可靠依据。

2025/6/212Boilerefficiencyistheratioofenergyoutputtoenergyinputandisusuallyexpressedasapercentage.Theoutputtermforasteamgeneratoristheenergyabsorbedbytheworkingfluidthatisnotrecoveredwithinthesteamgeneratorenvelope.Itincludestheenergyaddedtothefeedwateranddesuperheatingwatertoproducesaturated/superheatedsteam,reheatsteam,auxiliarysteamandblowdown.Itdoesnotincludetheenergysuppliedtopreheattheenteringairsuchasairpreheatercoilsteamsuppliedbythesteamgenerator.Theenergyinputtermisthemaximumenergyavailablewhenthefueliscompletelyburned,i.e.,themassflowrateoffuel,MRF,multipliedbythehigherheatingvalueofthefuel.Thisisconventionallyexpressedas:3.3Boilerheatbalanceandboilerefficiency

§3-3锅炉热平衡的组成及锅炉效率(p10-17)

2025/6/213IntheU.S.,itiscustomarytoexpresssteamgeneratorefficiencyonahigherheatingvaluebasis.Steamgeneratorefficiencymayalsobeexpressedonalowerheatingvaluebasis(commoninEurope).Forthesamemassflowrateoffuel,theLHVefficiencymaybe3to10percentagepointshigherthantheHHVefficiency,dependingupontheamountofH2andH2Ointhefuel.Whencomparingsteamgeneratorefficiencyand/orplantheatrate,theymustbeonthesamebasis,i.e.,HHVorLHV.Efficiencymaybedeterminedbymeasuringthemassflowrateoffuelandsteamgeneratoroutput,whichisreferredtoastheinput-outputmethod(正平衡)theenergybalancemethod(反平衡).Theenergybalancemethodisgenerallythepreferredmethod.Itisusuallymoreaccuratethantheinput-outputmethod.3.3Boilerheatbalanceandboilerefficiency

§3-3锅炉热