Abstract
In order to explore the influence mechanisms of ambient wind speed on the performance of indirect air-cooled system, SCAL indirect air-cooled towers of a 600MW supercritical unit was taken as an example, and the corresponding calculation model was established. By the ways of CFD numerical simulation and field test, the variations along with ambient velocity of airflow field inside and outside the tower were simulated and the thermal performance of those towers under different ambient velocity was studied. The results showed that, the outlet resistance of air-cooled tower increased in pace with ambient velocity. Both temperature field inside the tower and pressure field inside and outside the tower were influenced by the ambient velocity to a large extent, while flow trajectory of flue gas inside the tower was basically similar. Moreover, the trends and changing laws of performance parameters from the level of segments and the tower were achieved. The conclusions would be of some reference significance for the optimal operation and design of indirect air-cooled system.
Highlights
The results showed that, the outlet resistance of air⁃cooled tower increased in pace with ambient velocity
中国电机工程学报,2015,35 ( 23) : 6089⁃6098 Xi Xinming, Wang Mengjie, Du Xiaoze, et al Airflow Field Characteristics in Indirect Dry Cooling Tower of Three Incorporate Towers System[ J]
Summary
摘 要:为探究环境风速对间接空冷系统性能影响机理,以某 600 MW 超临界机组 SCAL 空冷塔为对 象,建立相应的计算模型,采用 CFD 数值模拟与现场试验相结合的方式,模拟了空冷塔内、外流场随 环境风速的变化情况,研究了不同环境风速下空冷塔的热力性能。 结果表明,随着环境风速的增加, 空冷塔出口阻力增大,塔内温度场、塔内外压力场受风速影响较大,塔内烟气流动轨迹基本保持相似; 并得到了各扇段及塔整体性能参数随环境风速的变化趋势和规律,为间接空冷系统的运行和设计提 供一定的参考。 电力工业的快速发展在消耗大量一次能源的同 时,也消耗了大量的水资源[1] 。 空冷技术以空气取 代水作 为冷却介质, 直接或间接地冷却汽轮机排汽[2] ,在我国北方富煤缺水地区得以大规模应用。 直接空冷系统对于外界环境大风的敏感性要高于间 接空冷系统[3] ,日常检修维护工作量大,且在夏季 高温条件下运行背压高,冬季极寒条件下防冻压力 大。 间接空冷系统在上述方面有更大的优势,目前 国内设计和应用较多的是表面式凝汽器及散热器塔 外垂直布置的 SCAL 型间接空冷系统[4⁃5] 。 在此基 础上,考虑利用空冷塔自抽吸力抬升烟气,将脱硫塔 及烟囱修建在间接空冷塔内,简称“ 三塔合一” [6] 。 本文以某 2×600 MW 等级的 SCAL 型空冷塔为 研究对象,采用 CFD 数值模拟计算了不同环境风速 条件下间冷系统的热力性能,并与现场试验对比,验 证计算准确性;分析了空冷塔的主要性能参数如总 阻力、进塔风量、出塔水温、散热效率等的变化规律, 归纳总结了环境风速对空冷塔整体性能的影响机 理,为空冷塔科学经济运 行和工程设计提供技术 参考。 本文数值计算所选取的结构模型为实际尺寸的 结构,对该结构模型进行网格划分。 因散热器的尺 寸与整个计算区域差别比较大,且散热器附近处于 对流传热的中心区域,需要足够密而多的网格来捕 捉流场信息,而外围的大空间处于次要地位,可减少 网格数量,所以在计算中实体网格的划分采用了分 区划分网格的技术。 1.4 区域命名
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