• CN:11-2187/TH
  • ISSN:0577-6686

›› 2007, Vol. 43 ›› Issue (8): 224-228.

• 论文 • 上一篇    下一篇

低压条件下紧凑叉排管束沸腾换热特性试验

刘振华;杨荣华   

  1. 上海交通大学机械与动力工程学院
  • 发布日期:2007-08-15

EXPERIMENTAL RESEARCH ON BOILING HEAT TRANSFER CHARACTERISTICS OF COMPACT STAGGERED TUBE BUNDLES IN REDUCED PRESSURES

LIU Zhenhua; YANG Ronghua   

  1. School of Mechanical Engineering, Shanghai Jiaotong University
  • Published:2007-08-15

摘要: 针对传统的满液型蒸发换热器,将蒸发器中的水平加热管束按叉排方式紧凑排列形成窄缝空间,在大气压和低压运行条件下,利用窄缝空间沸腾强化换热机理,可以将在低壁温/低热负荷条件下的自然对流换热转化为核态沸腾换热,能有效提高满液式蒸发器的换热性能。和传统的满液型蒸发换热器相比,这种紧凑式蒸发器平均换热系数能提高一倍以上。紧凑蒸发器的管距、管位置,工作压力都对蒸发器的换热性能有显著影响,管距的影响是最大的。不同的压力条件下存在一个对应的最佳管距。在此管距下,蒸发换热器的强化换热性能达到最大。最佳管距对应的管束水力当量直径近似等于池内沸腾时的气泡脱离直径。随着压力减小,最佳管距逐渐增大。同时,紧凑式管束布置引起的窄缝空间内沸腾强化换热强化效果也逐步降低。

关键词: 沸腾, 管束, 紧凑式换热器, 强化换热

Abstract: For common flooded type evaporators, since heat fluxes and wall temperatures of heated tubes are generally quite low, the nucleate boiling heat transfer cannot generate on the heated tubes. However, when the distance between tubes is very small,the nucleate boiling in restricted spaces can generate at low heat flux or low wall temperature conditions easily and it can effectively enhance the heat transfer performance of the evapo-rators. The boiling heat transfer enhancement of water on plane tubes in compact, staggered tube-bundle evaporators under atmospheric and reduced-pressure conditions is investigates experimentally. The experiment investigates the effects of the tube spacing sizes, the positions of tubes and the test pressures on the boiling heat transfer characteristics in restricted spaces of compact tube bundles. The experimental results indicate that for the compact tube bundles, the effect of the tube spacing is very significant on the boiling heat transfer. The boiling heat transfer has a maximum enhancement when the tube spacing corre-sponds to an optimum value. The optimum tube spacing equals approximately to the departure diameter of the bubbles during a pool boiling. The enhanced heat transfer effect from the com-pact bundles would gradually decease with the decrease in the test pressures.

Key words: Boiling, Bundle, Compact heat exchanger, Enhanced heat transfer

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