2025/6/211BeforestudyingSteamgeneration蒸汽的产生Boiling沸腾Circulation循环Steam-waterflowsystem汽水系统Steam-waterseparation汽水分离S-Wsystemarrangement汽水系统布置Watercirculation水循环Naturalcirculation自然循环Forcedflow强制流动

2025/6/212Theprocessofboilingwatertomakesteamisafamiliarphenomenon.Thermodynamically,insteadofincreasingthewatertemperature,theenergyusedresultsinachangeofphasefromaliquidtoagaseousstate,i.e.,watertosteam.Asteamgeneratingsystemshouldprovideacontinuousprocessforthisconversion.Thesimplestcaseforsuchadeviceisakettleboilerwhereafixedquantityofwaterisheated(Fig.6).1.Boiling沸腾

2025/6/213Theappliedheatraisesthewatertemperature.Eventually,forthegivenpressure,theboiling(saturation)temperatureisreachedandbubblesbegintoform.在给定压力下，达到饱和温度，产生汽化现象Asheatcontinuestobeapplied,thetemperatureremainsconstant,andsteamescapesfromthewatersurface.Ifthesteamiscontinuouslyremovedfromthevessel,thetemperaturewillremainconstantuntilallofthewaterisevaporated.温度一定直到所有水汽化Toprovideacontinuousprocess,allthatisneededisaregulatedsupplyofwatertothevesseltoequalthesteambeinggeneratedandremoved.水的供应1.Boiling沸腾

2025/6/214Technicalandeconomicfactorsindicatethatthemosteffectivewaytoproducehighpressuresteamistoheatrelativelysmalldiametertubescontainingacontinuousflowofwater.小管径管子更有效Regardlessofwhethertheenergysourceisnuclearorfossilfuel,twodistinctboilingsystemsareusedtoaccomplishthistask:thosethatincludeasteamdrum(seeFig.7a),orfixedsteam-waterseparationpoint,汽水分离thosethatdonot(seeFig.7b),termedonce-throughsteamgenerators(OTSG).直流1.Boiling沸腾

2025/6/215Themostcommonandsimplesttocontrolisthesteamdrumsystem.Inthissystem,thedrumservesasthepointofseparationofsteamfromwater(lessthanboilingtemperature)entersthetubetowhichheat