【作者】 周力；

【导师】 吴幸慈；

【作者基本信息】 华中科技大学 ， 能源动力（专业学位）， 2022， 硕士

【摘要】 水蒸气在安全壳表面冷凝是非能动冷却的一个重要环节,在核电站发生失水事故且丧失外来电力的情况下,可以及时将安全壳内的热量导出,避免超温超压而使安全壳的完整性被破坏,同时,由于安全壳内存在大量不凝性气体,故为了强化存在不凝性气体时蒸汽的冷凝,本文提出在安全壳穹顶表面安置凝水点,并进行冷凝换热优化设计,主要结果如下:鉴于安全壳内流动复杂,本文选择平行和垂直于表面两个流向进行研究。选择安置球形和锥形凝水点的表面与平面进行对比。当混合气体平行于安置凝水点的穹顶表面流动时,相比于平面,安置锥形凝水点的表面总换热速率提高了 7.3%左右,安置球形凝水点的表面提高了 11.7%左右,强化换热效果更好。冷凝液大多集中在凝水点上且部分冷凝液会被气流冲走;当混合气体垂直于表面流动时,比起平面,安置锥形凝水点的表面总换热速率提高了 1.3%左右,安置球形凝水点的表面提高了 5.3%左右,强化换热效果更好,冷凝液大多集中在凝水点上,有利于形成液滴然后滴落。基于强化换热效果较好的球形凝水点,对其进行进一步的尺寸优化设计。在两种流向下,随着凝水点高度-底面半径比的增大,总换热速率均变化不大,随着凝水点尺寸的增大,单位面积上的换热速率明显下降。当凝水点高3.2mm、底面半径为1.6 mm时,在两种流向下表现的强化换热效果较好。基于该强化换热效果较好的球形凝水点尺寸,对其进行进一步的分布间距优化设计。在两种流向下,随着凝水点分布间距的增大,总换热速率均变化不大。通过对单个或两个凝水点附近流域的分析,考虑了平行和垂直于表面两种流动方向以及特定的边界条件,计算结果表明,在安全壳穹顶表面上安置高3.2 mm、底面半径为1.6 mm且分布间距为5 mm时的球形凝水点对冷凝换热的强化效果较好。更多还原

【Abstract】 The condensation of vapor on containment plays an important role in nuclear passive safety.In the event of a loss-of-coolant accident in a nuclear power plant and the loss of external power,the heat in the containment can be dissipated in time to avoid overtemperature and over-pressure that would damage the integrity of the containment.This dissertation proposes to place picots on the surface of the containment dome to enhance the condensation of vapor in the presence of non-condensable gas.The main results are as follows:In this dissertation,parallel and perpendicular flows to the surface are discussed.The computational results show that when the mixture gas flows parallel to the surface with a picot,compared with the flat surface,the total heat transfer rate of the surface with a conical picot is increased by about 7.3%,the total heat transfer rate of the surface with a spherical picot is increased by about 11.7%.Most of the condensate is concentrated on the picot and part of it is washed away by the flow.When the mixture gas flows perpendicular to the surface with a picot,compared with the flat surface,the total heat transfer rate of the surface with a conical picot is increased by about 1.3%,the total heat transfer rate of the surface with a spherical picot is increased by about 5.3%.Most of the condensate is concentrated on the picot,which is conducive to the formation and dripping of droplet.Size sensitivity analysis on spherical picot is performed because of better heat transfer enhancement effect.In the both two flow directions,with the increase of the height-tobottom radius ratio,there is no significant change in total heat transfer rate.With the increase of the size of the picot,the heat transfer rate per unit area decreases significantly.When the height of the picot is 3.2 mm and the bottom radius of the picot is 1.6 mm,the heat transfer enhancement effect is better in the both two flow directions.Spacing analysis on spherical picots with a radius of 1.6 mm and a height of 3.2 mm is performed because of better heat transfer enhancement effect.In the both two flow directions,with the increase of spacing,there is no significant change in heat transfer rate.Through the analysis of the watershed near a single or two picots,two flow directions parallel and perpendicular to the surface and specific boundary conditions are considered,and the calculation results show that,the heat transfer enhancement effect is better with spherical picots with a height of 3.2 mm,a bottom radius of 1.6 mm and a spacing of 5 mm are placed on the inner surface of the containment dome.更多还原