基于多孔介质模型的电厂凝汽器汽侧流动特性

Steam flow characteristics of shell side of condenser based on porous medium model

针对凝汽器管束区的分形及其分布阻力特性,建立基于凝汽器管束区乏汽流动多孔隙率的多孔介质模型,并分析管束区乏汽的速度、流量及压力的变化。研究结果表明:在均匀管内换热条件下,该结构类型的凝汽器中的凝结效果主要取决于管板外边界附近的冷却管束的换热,而且上管束区域的冷凝效果比下管束区的冷凝效果差;在空冷区中,对称分布的高动压区使得流入空冷区中的乏汽转向流入凝结管束区中,一方面避免了工质直接通过排汽口排放的损失,另一方面,该动压区所处的位置以及动压随负荷发生变化,尤其是在240 MW负荷附近的工况条件下变化显著,将导致排气口带走更多的工质。

With regard to the characteristics of fractal and distribution resistance of the condenser tube bundle, a porous medium model with three kinds of porosity was established based on the steam exhaust flow in condenser tube bundle area, and the characteristics of speed, rate of flow and pressure of steam exhaust were analyzed. The results show that under the conditions of different loads and uniform tube heat transfers, the condensation effect of condenser relates to the heat exchange of the cooling tube bundle near outside border of the tube plate, and the condensation effect of lower tube bundle is the best among three tube bundles. The high dynamic pressure with symmetrical distribution in air cooled zone makes the steam exhaust steering into the tube bundle zone, which prevents the medium from being discharged directly through the exhaust port, but the position and the dynamic pressure will change with the load, especially when near 240 MW. The significant change will lead to more medium loss.