垂直三角形纵槽管的膜状冷凝传热最大有效管长与管长设计

在纵槽表面膜状冷凝传热中,其传热量几乎仅由波峰区域形成。作者以该域为传热面,进行了传热分析与计算。计算结果表明,管长对平均传热膜系数影响很小。这一结果与Ozgen对有关实验现象的解释基本一致,可在一定程度上证实他的看法。对波谷区冷凝液流动做了数值解。对该区液膜厚度与管长做了数值关联,进而得到了三角形纵槽管最大有效管长及波峰区域面积计算公式。 本文方法与结果,为三角形槽管的管长设计提供了一种简便可行的方法。同时,该类纵槽管的传热计算也因之易于进行。

An Analysis of Film Condensation Heat Transfer on the Surface of a Vertical Triangular Flute and Tube a New Method for Designing the Tube Length

The process of film condensation heat transfer on the surface of a vertical flute tube is analyzed based on that each part of the flute has different contribution to the heat transfer. Owing to the decisive contribution of the wave crest tegion, the calculation of heat transfer was carried out by choosing the area of this region as the heat transfer area of the whole tube. Calculated results show that the average coefficient of heat transfer is nearly constant along the tube,and is consistent with Ozgen' s explanation for his experiments. A numerical solution to the governing equation for the flow of condensed liquid in the wave valley region was developed by the finite element method. The thickness of the liquid film in this region was interrelated to the length of the tube in the vertical direction, and a formula for the maximum effective tube length and the area of the wave crest region for a triangular flute tube was deduced thereby. By applying the above results, the calculation of heat transfr and the design of tube length for vertical fluted tubes are greatly simplified.