| 摘要: |
| 为了研究管型对汽-气凝结换热的影响和强化汽-气凝结换热过程，建立了汽-气在液滴形管与圆管外凝结换热所形成的气液膜的厚度及换热系数沿管壁分布的综合数学模型。通过有限差分的方法，以天然气燃烧产生的烟气为例对两种管型进行了计算比较。在有效换热面积相等的情况下，与圆管相比，液滴形管上半部分管径小，压力梯度大，有利于排液,下半部分表面曲率大，亦有利于排液；液滴形管表面形成的气膜薄，液膜亦薄，珠状凝结区域大，液珠尺寸小，凝结换热系数大；液滴形管对显热传递亦有一定的强化作用。通过实验对计算结果进行了比较验证，结果表明该模型亦适用于椭圆管和其它汽-气混合流体种类。 |
| 关键词: 强化换热 凝结换热 有限差分 液滴形管 气液膜厚度 |
| DOI： |
| 投稿时间：2012-12-07
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| 基金项目: |
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| The Research on Vapor-gas Condensation Heat Transfer over a Drop-shaped or Circular Tube |
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Li Huijun, Peng Wenping
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| (School of Energy Power and Mechanical Engineering, North China Electric Power University) |
| Abstract: |
| In order to study the effects of tube type on vapor-gas condensation heat transfer and strengthen vapor-gas condensation heat transfer, the present paper establishes the integrated model of gas liquid film thickness and heat transfer coefficient along the wall when vapor-gas mixed fluid crosses vertically both circular tube and drop-shaped tube and condensation occurred. Through the finite difference method, the calculation and comparison are carried out with flue gas from natural gas combustion as an example. In the circumstance that the effective heat transfer area is same, compared with circular tube, diameter is smaller on upper half of drop-shaped tube and pressure gradient is greater, which is helpful for drainage; surface curvature is larger on lower half of drop-shaped tube, which is also helpful for drainage. Gas film on surface of drop-shaped tube is thinner, and liquid film is also thinner; drop-wise condensation area is larger and droplet size is smaller, so condensation heat transfer coefficient is greater. Besides, drop-shaped tube also has certain enhancement to sensible heat transfer. The calculation results are compared and verified by experiment, and this model is also suitable for oval tube and other kinds of vapor-gas mixed fluid. |
| Key words: heat transfer enhancement Condensation Heat Transfer finite difference drop-shaped tube gas liquid film thickness |
