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81.
Sang-Nyung?KimEmail author Yeon-Sik?Cho 《Journal of Mechanical Science and Technology》2004,18(1):74-81
The KSNP Steam Generators (Youngkwang Unit 3 and 4, Ulchin Unit 3 and 4) have a problem of U-tube fretting wear due to Flow
Induced Vibration (FIV). In particular, the wear is localized and concentrated in a small area of upper part of U-bend in
the Central Cavity region. The region has some conditions susceptible to the FIV, which are high flow velocity, high void
fraction, and long unsupported span. Even though the FIV could be occurred by many mechanisms, the main mechanism would be
fluid-elastic instability, or turbulent excitation. To remedy the problem, Eggcrate Flow Distribution Plate (EFDP) was installed
in the Central Cavity region of Ulchin Unit 5 and 6 steam generators, so that it reduces the flow velocity in the region to
a certain level. However, the cause of the FIV and the effectiveness of the EFDP was not thoroughly studied and checked. In
this study, therefore the Stability Ratio (SR), which is the ratio of the actual velocity to the critical velocity, was compared
between the value before the installation of EFDP and that after. Also the possibility of fluid-elastic instability of KSNP
steam generator and the effectiveness of EFDP were checked based on the ATHOS3 code calculation and the Pettigrew’ s experimental
results. The calculated results were plotted in a fluid-elastic instability criteria-diagram (Pettigrew, 1998, Fig. 9). The
plotted result showed that KSNP steam generator with EFDP had the margin of Fluid-Elastic Instability by almost 25%. 相似文献
82.
Duk-Sang?KimEmail author Yong-Seok?Cho 《Journal of Mechanical Science and Technology》2004,18(11):2032-2041
Results from an experimental study of flow distribution in a close-coupled catalytic converter (CCC) are presented. The experiments
were carried out with a flow measurement system specially designed for this study under steady and transient flow conditions.
A pitot tube was a tool for measuring flow distribution at the exit of the first monolith. The flow distribution of the CCC
was also measured by LDV system and flow visualization. Results from numerical analysis are also presented. Experimental results
showed that the flow uniformity index decreases as flow Reynolds number increases. In steady flow conditions, the flow through
each exhaust pipe made some flow concentrations on a specific region of the CCC inlet. The transient test results showed that
the flow through each exhaust pipe in the engine firing order, interacted with each other to ensure that the flow distribution
was uniform. The results of numerical analysis were quali-tatively accepted with experimental results. They supported and
helped explain the flow in the entry region of CCC. 相似文献
83.
武汉市居住空间分异特征初探 总被引:1,自引:0,他引:1
自改革开放以来,现在社会实体的分化在城市社会地理格局中在一定程度上通过居住空间的分异予以表征。通过对空间分异的研究表明,武汉市7大群体聚居的居住空间的分异格局已经出现。 相似文献
84.
85.
上海城市外环线是上海市域快速路网的重要一环。文章重点介绍了外环线(浦东段)二期工程的道路设计中线形设计、立体交叉和路基设计的设计特色及技术措施,可供道路专业工程设计与施工人员参考。 相似文献
86.
对房地产开发中的老年人公共空间人性化问题进行了探讨,从房地产开发中的老年人公共空间研究的必要性出发,针对老年人的生理和心理特点,总结出老年人公共空间人性化设计的要点,以提高房地产开发的社会效益和经济效益。 相似文献
87.
浅谈水环热泵空调系统 总被引:1,自引:0,他引:1
介绍了水环热泵空调系统的原理及其特点,阐述了水环热泵中央空调系统的优点,分析了该系统的缺点,并提出了相应的解决措施,指出水环热泵系统具有良好的节能效果,同时具有巨大的节能潜力和广阔的应用前景。 相似文献
88.
Factors affecting bulk to total bacteria ratio in drinking water distribution systems 总被引:1,自引:0,他引:1
Bacteria in drinking water systems can grow in bulk water and as biofilms attached to pipe walls, both causing regrowth problems in the distribution system. While studies have focused on evaluating the factors influencing the bacteria in bulk water and in biofilms separately, there is a need for understanding biofilm characteristics relative to the bulk water phase. The current study evaluated the effects of chlorine and residence time on the presence of culturable bacteria in biofilms relative to that in bulk water. The results showed that when no chlorine residual was present in the system, the median ratio of bulk to total bacteria was 0.81, indicating that 81% of the bacteria were present in bulk water, whereas only 19% were present in the biofilm. As chlorine concentration increased to 0.2, 0.5, and 0.7 mg/L, the median percentage of bacteria present in bulk water decreased to 37, 28, and 31, respectively. On the other hand, as the residence times increased to 8.2, 12, 24, and 48h, the median percentage of bacteria present in bulk water increased to 7, 37, 58, and 88, respectively, in the presence of a 0.2mg/L chlorine residual. The common notion that biofilms dominate the distribution system is not true under all conditions. These findings suggest that bulk water bacteria may dominate in portions of a distribution system that have a low chlorine residual. 相似文献
89.
文章通过对一例少见的混凝土病害调查、检测、分析,排除了碱-集粹反应、水泥安定性不合格等因素导致混凝土起鼓、开裂、剥落的可能性,认为混凝土中因疏忽而混入了过烧CaO是该工程混凝土出现病害症状的原因,本文所述的工程调查、检测、分析可供同行对类似工程的检测与分析和处理作参考. 相似文献
90.
从宏现角度介绍奥林匹克公园中心区,解析奥林匹克公园中心区的空间结构特点,阐述中国传统文化元素的研究与运用,总结环境设计理论及控制方法.以期提供大型城市中心规划及景观设计的经验. 相似文献