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Journal of Zhejiang University SCIENCE A
ISSN 1673-565X(Print), 1862-1775(Online), Monthly
2023 Vol.24 No.12 P.1140-1146
A novel approach for the optimal arrangement of tube bundles in a 1000-MW condenser
Abstract: As shown in Figs. 1a and 1c, the pressure at the inlet increases by about 50 Pa due to the blocking of the first few rows of tube bundles. To better discuss the heat transfer of each tube, the tube bundle is divided into 10 zones (Condensation01–Condensation10) from top to bottom, among which Condensation10 is the air-cooling zone. Detailed description can be seen in Section S2 of the ESM. The air-cooling zone is the last section where the water vapor flows out of the tube bundle, and the air extraction port is located in it. Directly upon entering the Condensation01 zone, some of the steam drops in pressure due to condensation. Another part of the steam enters the channels on both sides, and gradually enters the Condensation02–Condensation08 zones obliquely downward to condense; then, the pressure gradually decreases by about 100 Pa. Due to the bottom wall being blocked, the pressure in the lower half of the Condensation09 zone is slightly increased, and this phenomenon is more significant for non-uniform tube-bundle arrangements. In the air-cooling zone (Condensation10), the air and uncondensed steam are drawn out at the outlet by the exhaust fan, and the pressure drop is relatively large (about 200 Pa). Regarding the velocity distribution shown in Figs. 1b and 1d, the highest velocity is located at the central channel with different tube-bundle arrangements. Specifically, the highest velocity for the uniform tube-bundle arrangement is about 170 m/s, while it is about 180 m/s for the non-uniform tube-bundle arrangement. The velocity in the channels on both sides decreases gradually and decreases further once the steam passes through the microchannel. The velocity decreases again to 40 m/s at the bottom of the condenser (Condensation09), and the velocity between the tubes in Condensation01–Condensation09 zones is about 30 m/s. The velocity at Condensation10 in the air-cooling zone is about 70 m/s.
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机构：1浙江大学，能源清洁利用国家重点实验室，中国杭州，310027；2浙江大学上海高等研究院，中国上海，200120；3中国电力工程顾问集团中南电力设计院有限公司，中国武汉，430071；4黄冈大别山发电有限责任公司，中国黄冈，438300；5中能建数字科技集团有限公司，中国北京，100022
目的：针对大型凝汽器，提出一种新的方法来解决传统多孔介质模型的缺点，优化冷凝器管束布局。
创新点：流场被分为两个区域，即凝结区和非凝结区。在凝结区使用相对较细的网格，并分析蒸汽凝结过程中的热阻，在质量输运方程中加入一个源项来描述蒸汽凝结量。与多孔介质模型相比，这种方法能更好地反映不同管束布置下的流场特征，同时与直接建模相比大大降低计算成本。
方法：1.研究凝汽器壳侧流场的流动和传热规律，将其划分为管束区域和非管束区域。2.在冷凝发生的区域即管束区域，通过物理规律分析与理论计算推导出冷凝的质量源项，并将该质量源项通过用户自定义函数加载于管束区域，构成新的蒸汽冷凝模型。3.以某1000MW级凝汽器为例，使用新的蒸汽冷凝模型模拟壳侧流场，与其设计参数对比并验证该方法的有效性。4.使用该方法，对1000MW级凝汽器两种不同管束布置及三种工况下的壳侧流场进行数值模拟，进一步验证该方法的可行性和必要性。
结论：1.本文提出的数值模拟方法，在模拟流动动力学以及1000MW冷凝器内的冷凝过程方面表现出合理的精度。2.当空气质量分数达到约0.001的临界值时，实现气流中空气层的动平衡；低于该临界值，传热系数从4250 W/(m2·K)至155 W/(m2·K)，相当于下降96.35%；高于该临界值的区域称为空气积聚区域。3.在额定漏气条件下，均匀管束布置的压降比非均匀管束布置低51.73%；此外，随着空气浓度的增加，传热效率随着空气泄漏量的增加而降低，导致传热系数降低。
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DOI:
10.1631/jzus.A2300183
CLC number:
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On-line Access:
2023-12-29
Received:
2023-02-17
Revision Accepted:
2023-04-23
Crosschecked:
2024-01-04