不同管束布置方式下含有空气的蒸汽自然对流冷凝换热特性分析

Analysis of Heat Transfer Characteristics of Natural Convection Condensation of Steam Containing Air under Different Tube Bundle Arrangements

为研究非能动安全壳冷却系统(PCCS)热交换器管束布置对自然对流条件下含有空气的蒸汽冷凝换热特性的影响,采用气体组分输运方程和冷凝模型耦合,对单管、单排到五排管束通道内冷凝换热过程进行数值研究。研究发现,管束区内存在由于管间高浓度空气层干扰使冷凝换热能力减弱的“抑制效应”,以及由于水蒸气壁面冷凝导致气体横向流动使壁面冷凝能力强化的“抽吸效应”。对不同管束结构下2种效应对冷凝换热的影响进行分析,结果表明,随着管束排数的增加,2种效应对冷凝换热的影响逐渐增强,导致冷凝管周向局部冷凝换热能力不均匀性增加,其中五排管束周向局部冷凝换热系数(HTC)最大值为单管的2.3倍,最小值仅为单管的44.7%。在双排、三排和四排管束中,正四边形布置管束的冷凝换热能力优于正三角形布置,而五排管束中,正三角形布置的冷凝换热能力更强。本研究可对PCCS热交换器管束布置优化提供参考。

In order to study the effect of tube bundle arrangement of heat exchanger in passive containment cooling system(PCCS)on the condensation heat transfer characteristics of steam containing air under natural convection conditions,the condensation heat transfer process in channels of single tube,single-row to five-row tube bundles is numerically studied by coupling gas component transport equation and condensation model.It is found that there is a“inhibiting effect”that reduces the condensation heat transfer capacity due to the interference of high-concentration air layers between tube bundles,and a“suction effect”that strengthens the condensation capacity on the wall due to the transverse flow of gas caused by water vapor wall condensation.The influence of such two effects on condensation heat transfer under different tube bundle structures is analyzed.The results show that with the increase of the number of rows of tube bundles,the influence of the two effects on the condensation heat transfer gradually increases,leading to the increase of non-uniformity of circumferential local condensation heat transfer capacity of condensing tubes.Among them,the maximum circumferential local condensation heat transfer coefficient(HTC)of five-row tube bundles is 2.3 times that of single tube,and the minimum is only 44.7%of that of single tube.In the double-row,three-row and four-row tube bundles,the condensation heat transfer capacity of the regular quadrilateral arrangement is better than that of the regular triangle arrangement,while in the five-row tube bundle,the condensation heat transfer capacity of the regular triangle arrangement is stronger.This study can provide a technical reference for the optimization of the tube bundle arrangement of the PCCS heat exchanger.