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针对空冷凝汽器上的逆流凝结管,用扩散层模型模拟管内空气–蒸汽的组分输运,用多相流理论中的VOF方法建立管内两相流的控制方程,分别用Lee模型与CSF模型计@算方程中的质量与动量源项.在一根仿真样管(长宽高尺寸:1000mm×5mm×50mm,倾斜角:60°)上,运行9个算例,对管内两相流的凝结换热与流动进行数值模拟.数值结果表明,在样管出口管段,管壁上的热流密度波动较大;当样管入口的空气含量超过1.0%时,不可凝气体对管内蒸汽凝结的影响不可忽略.获得了管内气相组分浓度的标量场,发现,扩散层内存在的空气浓度梯度是管内蒸汽凝结性能恶化的原因.利用瞬态计算,捕捉到管内复杂的动力学特性,包括液膜悬空、液膜爬坡与液滴夹带,发现这些特性会破坏管内扩散层的稳定与完整,增强蒸汽凝结;用可视化的两相流体积分数云图,表现液膜悬空、爬坡溢出以及液滴从形成到抛起的连续过程,并分析这些现象发生时,两相流的速度特征;数值计算还得到了管壁上液膜的流型,将其定性为溪状流.“,”The diffusion layer was applied to model the species transport of air and vapour in the reflux-flow condensation tube equipped on the air cooled condenser, and the VOF approach in multiphase flow was implemented to solve the governing equations, with the mass and momentum source term calculated using Lee model and CSF model respectively. Nine computational cases were accomplished for the two-phase flow in a prototype tube (1000mm length, 5mm width, 50mm altitude, in 60° inclination to horizontal). The numerical results show that, the heat flux through the condensation wall fluctuates at the tube outlet zone, and the influence of the non-condensable gas to the vapour condensation cannot be ignored when inlet mass fraction of the air is more than 1.0%. From the numerical scalar field of species concentration, it is found that the vapour condensation performance deteriorates in prototype tube thanks to the air concentration gradient in the diffusion layer. The transient computed results are shown to effectively capture the observed complex flow characteristics including film dangling, climbing and droplet entrainment, which enhance vapour condensation by destroying the stability and integrity of the diffusion layer. Furthermore, the predicted gas-liquid velocity profiles in these conditions are analyzed. The flow pattern of the condensate film on tube wall is also successfully predicted, which is good agreement with the rivulet flow.