直接空冷凝汽器扁平管含不凝结气体的凝结换热

Condensation with Non-condensable Gas Inside Flat Tube of Air-cooling Condenser

为深入了解直接空冷火电机组凝汽器的冬季运行特性,针对含有不凝结气体的扁平管内蒸汽顺流凝结传热过程,考虑了汽液两相流动的相界面剪切应力、相界面表面张力,以及相界面的扩散传质,建立了物理数学模型。改变扁平管出口不凝结气体的浓度、改变冷却能力,通过对数学模型的数值求解,得到冬季运行不同工况条件下,凝结温度和液膜厚度的空间分布。研究结果表明:在凝结过程的末端,出口不凝结气体含量对蒸汽冷凝温度的降低有显著的影响;可将出口不凝结气体含量作为直接空冷凝汽器提高防冻能力的重要控制变量。研究结果为直接空冷火电机组凝汽器防冻问题的解决提供了理论参考。

To have a deep understanding of the air-cooling condenser unit＇s operating characteristics in winter,steam condensation heat transfer process with non-condensable gas inside the flat tube is modeled by considering vapor-liquid two-phase interfacial shear stress,interfacial surface tension and mass diffusion of the interface.Then based on the model,by changing both the concentration of non-condensable gas at the exit and the heat exchange capability,a series of work were conducted.Thus a series of calculation results for the spatial distribution of condensate film and condensation temperature were obtained and analyzed.The results indicate that the concentration of non-condensable gas at the exit has a significant impact on the condensation temperature and the parameters should be utilized as the important control variables to improve the anti-freezing ability of the air-cooling condenser.The above results may supply some theoretical fundamentals for further solving the anti-freezing problem of air-cooling condenser.