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时间:2020-03-28
《水平翅片管外凝结液膜分布及换热特性影响研究.pdf》由会员上传分享,免费在线阅读,更多相关内容在行业资料-天天文库。
1、第41卷第4期华北电力大学学报V01.41.NO.42014年7月JournalofNorthChinaElectricPowerUniversityJu1.,2014doi:10.3969/j.ISSN.1007—2691.2014.04.15水平翅片管外凝结液膜分布及换热特性影响研究李慧君,董楠(华北电力大学能源动力与机械工程学院,河北保定071003)摘要:肋片管换热技术被广泛应用于工程实践,当有凝结现象发生时,液膜对换热产生热阻,因此,为强化换热有必要对液膜分布进行研究。建立了水平翅片管的物理模型,基于Nus
2、seh理论及修正的膜理论,推导出了肋片侧壁以及肋间基管的凝结液膜厚度和换热系数计算式,并对模型进行了验证。通过对水平梯形肋片管的计算,结果表明:在非淹没区,肋片侧壁的凝结液厚度沿圆周方向不断增厚,沿肋高方向变薄,局部凝结换热系数沿圆周向减小,沿肋高方向增加;基管上圆周角0。一范围内液膜不断增厚,并在靠近淹没区急剧增厚,局部凝结换热系数减小;肋片间距的大小对换热性能有较大的影响,因此,通过优化最佳肋片间距可以提高肋片管的换热性能,为设计出高效换热器提供一定的参考。关键词:凝结换热;肋片管;液膜厚度;换热特性中图分类号:
3、TK124文献标识码:A文章编号:1007—2691(2014)O4—0095—06StudyofthecondensateheattransferandthecondensatemmdistributionoutsidehorizontalfinnedtubeLIHui-jun,DongNan(SchoolofEnergyPowerandMechanicalEngineering,NorthChinaElectricPowerUniversity,Baoding071003,China)Abstract:Fin—t
4、ubeasaheattransferenhancementtechnologyhasbeenwidelyusedinengineeringpractice,whencondensationoccursthecondensationfilmisheattransferresistance,SOitisnecessarytoresearchfilmdistributionforheattransferenhancement.BasedontheNussehtheoriesandmodifiedfilmtheorythep
5、aperestablishesthephysicalmodelonhorizontalfinnedtube,andcalculatesthethicknessoffilmandheattransfercoefficientonthefinflankandthechannelbetweenfins.Thenthepaperverifiesthemode1.Resultsshowthatintheunfloodedregionthethicknessoffilmonfinflankconstantlythickening
6、followstheangleofcircumferenceandconstantlythinningfollowsthedirectionofribheight,andthelocalheattransfercoefficientonfinflankdecreasesinthecircumferentialdirectionandincreasesinthedirectionoftheribheight.Onthechannelbetweenfinsthethicknessoffilmincreasesandthe
7、heattransfercoem·cientdecreasesfromtheangle0。t。,ofcircumference,whenitarrivesatthefloodedregionthethicknesssharplyincreasesandtheheattransfercoefficientsharplydecreases.Thesizeoffinpitchinfluencestheheattransferperform—ance.Therefore,thepaperprovidesareferencef
8、ordesigningthehighefficientheatexchangerbyoptimizingthefinpitchtoimprovetheheattransfercharacteristics.Keywords:condensationheattransfer;finnedtube;filmthickness;heattransfe
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