垂直纵槽管强化膜状冷凝换热研究

Analysis of enhanced heat transfer of film condensation on vertical fluted tubes

用数值方法对饱和蒸汽在纵槽管表面的冷凝换热性能进行了研究。以发展段为主要研究对象,对模型进行了适当的简化,建立了液膜的基本方程,并与二维导热方程耦合,用Runge-Kutta法和有限元法解方程,通过迭代,分别得到了传热量以及最大液膜厚度与坐标z的关系式。最后用文中的分析方法,研究了制冷剂R-113在余弦形纵槽管上的冷凝,并与文献中的实验值做了对比。结果表明,纵槽管的长度(无除液盘时)或除液盘间距应小于最大有效管长,以便纵槽管在温差较大时仍具有较好的换热效果;在温差较小时,数值分析结果与文献中的实验数据吻合较好,证明本文的分析方法具有可行性。

The heat transfer performance of condensation of saturated vapor on the fluted tube was investigated with numerical method. The developing portion was analyzed in details. The basic equations of liquid film were established and coupled with two-dimensional thermal conduction equation. The equations were solved iteratively using Runge -Kutta method and the finite element method. The formula for heat transfer, maximum liquid film thickness and z coordinate was obtained. The condensation of refrigerant R- 113 on the cosine fluted tube was analyzed with the present analytical method, and the calculations were compared with the experimental data from reference. It is shown that the length of fluted tube （ no condensate drainage skirts） or the distance between condensate drainage skirts should be less than the maximum effective length so that a better performance of heat transfer is realized at high temperature difference. The calculations are in good agreement with experimental data from reference, therefore the present analysis is feasible.