支承板支撑多跨管束流致振动试验研究

本文针对支承板支撑4跨传热管直管束开展流致振动基础试验。试验件由49根旋转正三角形布置的模拟传热管组成,传热管两端固定,中间3处采用支承板支撑。试验测量获得了单向横流冲刷和双向横流冲刷下不同进口流速传热管束的振动特性,获得振幅、频率、临界雷诺数等关键信息。结果表明,双向横流冲刷下的传热管较单向横流冲刷下的在更低雷诺数下发生失稳,两种流动方式下传热管发生失稳时加速度峰值频率均为104Hz,该值与单跨两端固支模型的理论计算固有频率非常接近。研究结果可为传热管束流致振动数值模拟分析提供验证。     

换热器传热管与支承板碰撞力的数值模拟

在流动诱发振动的作用下,传热管的微振磨损,是导致换热器损坏的重要原因之一.预测管子微振磨损率的一个关键参数是管子-支承碰撞力.本文利用有限元模型计算了单跨悬臂管作平面运动时的管子-支承振动碰撞力.数值模拟的结果与实验数据作了比较,实验数据与分析的结果是相符的.     

换热器传热管微振磨损的实验研究

在室温下的空气和水中实验研究了激励力幅比、激励力幅值、激励频率、支承间隙和支承板厚度对传热管碰撞力和磨损率的影响,建立了微振磨损率与碰撞力均方根值之间的实验关系式。     

换热器管子自振频率的研究

本文提出一种计算换热器管子自振频率的新方法。把换热器管子当作连续梁,中间折流板视为简支,两端视为固定端(由管板固定)。本文所述方法可用于计算多跨不等跨长管子的自振频率。     

蒸汽发生器用栅格型管子支承板研究

通过研究栅格型管子支承结构的特点,对目前处于主流应用地位的拉削型管子支承板进行改进,提出一种新的管子支承结构方案,使其在具备栅格型支承结构要素的同时又不失拉削支承板的优点。与BabcockWilcox公司的栅格型支承结构相比,本文的方案性能更佳,具有潜在应用前景。     

换热器传热管与支承板间碰撞力的分析和实验研究

由于流致振动而产生的传热管微振磨损,已构成核电站蒸汽发生器故障的主要原因之一。影响管子磨损的因素很多,关键参数之一是管子一支承板间的碰撞力。本文用非线性间歇碰撞的有限元模型,编制了平面横向和空间横向碰撞力计算程序。在室温空气条件下进行的单跨管微振实验表明,平面和空间横向碰撞力的计算值与实验数据二者的符合程度是满意的。     

蒸汽发生器二次侧硬性沉积物清洗技术

硬性沉积物可能挤压传热管并导致管壁腐蚀,大修期间可通过柔性冲洗或化学清洗的技术清除管板上的硬性沉积物。我国近年来新投产的核电机组也在管板上开始发现了硬性沉积物的情况,硬性沉积物可能对传热管造成挤压,对传热管造成点蚀的风险也远高于粉状沉积物,因此加强对硬性沉积物的清洗技术研究具有重要意义。本文介绍了硬性沉积物的形成机理,并介绍了柔性冲洗和化学清洗技术及其应用情况。     

反应堆热交换器模拟体振动试验研究

本文用热交换器的模拟体对传热管的振动进行了试验研究。首次用非接触式传感器(即电涡流探头)直接在水下测得了管子的振幅、自振频率等,并分析了流动参数及结构参数对振动的影响。根据试验结果推荐了可供计算时参考的经验公式。     

不可压缩粘性流中板状梁的振动附加质量及阻尼

采用小参数展开法研究水口水槽中板状多跨梁与水槽底形成小间隙对梁的固有动特性，导出了梁振动时流体的附加质量系数和附加阻尼系数的解析表达式，并通过对频率的计算值与实验值的比较，间接验证了本文结果的正确性，得到了静水中多跨梁的固有频率随间隙值的变化规律。     

核电厂蒸汽发生器设计中的安全问题

介绍了核电厂蒸汽发生器设计中应考虑的安全问题，包括传热管材料的选择、支撑板材料与结构设计、防振架材料与结构设计、管子与管板的连接和热工水力结构的改进设计。最后还介绍了ALWR—URD对蒸汽发生器设计的要求。     

Crossflow-induced vibrations of heat exchanger tube banks

This paper presents a mathematical model for crossflow-induced vibration of tube banks. Motion-dependent fluid forces and various types of flow noises are incorporated in the model. An analytical solution for the fluid inertia force, hydrodynamic damping force, and fluid elastic force is given for tube banks arranged in an arbitrary pattern. Based on the model, a better understanding of the vibrations of heat exchanger tube banks subjected to various flow excitations can be developed.     

非均匀两相流传热管流致振动中阻尼模拟研究

In the flow-induced vibration analysis of the heat exchanger tube of the stream generator, the damping of each position on the tube is different, since the secondary side of the tube is the two-phase flow (stream-water) and the void-fraction is gradually increased from bottom to top. It is necessary to study the simulation of the tube damping in non-uniform two-phase flow. The study is based on the Pettigrew's damping formula of tube in two-phase flow and the void-fraction distribution along the tube in the typical example. For the two-phase damping component of the tube damping, the disadvantage of damping overestimation of void-fraction processing method in common engineering software are analyzed. The reason is the nonlinearity of the void-fraction influence coefficient. The method of segmentation weighting void-fraction is developed. The effects of different segment lengths are studied, indicating that the section lengths should be minimized. For the subsequent segmentation damping weighting problem, the effects of different weighting factors in engineering methods and standards are compared, and the difference is small. The results of flow-induced vibration analysis with different damping inputs were compared to judge the applicability of Pettigrew's damping formula. From the above four researches, the recommended simulation method of the tube damping in non-uniform two-phase flow is given to more accurately carry out the flow-induced vibration analysis of heat exchanger tube.     

非均匀两相流传热管流致振动中阻尼模拟研究

在蒸汽发生器传热管流致振动分析时，由于传热管二次侧为汽水两相流，且空泡份额从下到上逐步增加，使得传热管上各位置的阻尼不同，需开展非均匀两相流中传热管的阻尼模拟研究。使用Pettigrew的两相流中管阻尼公式，结合典型实例中空泡份额沿传热管分布情况开展后续分析。传热管阻尼中的两相阻尼分量，分析了常用工程软件空泡份额处理方法阻尼高估的弊端，原因在于空泡份额影响系数的非线性。引入分段加权的方法，研究了不同分段长度的影响，表明应尽量减小分段长度。针对后续的分段（非均匀）阻尼加权等效问题，对比了工程方法和规范中不同加权因子的影响，彼此差异较小。开展了不同阻尼输入的流致振动分析结果比较，判断Pettigrew阻尼公式的适用性。由上述4个问题的研究给出推荐的非均匀两相流中传热管阻尼模拟方法，以更准确地开展传热管流致振动分析。      

Modeling and analysis of thermal damping in heat exchanger tube bundles

Most structures and equipment used in nuclear power plant and process plant, such as reactor internals, fuel rods, steam generator tubes bundles, and process heat exchanger tube bundles, are subjected to flow-induced vibrations (FIV). Costly plant shutdowns have been the source of motivation for continuing studies on cross-flow-induced vibration in these structures. Damping has been the target of various research attempts related to FIV in tube bundles. A recent research attempt has shown the usefulness of a phenomenon termed as ‘thermal damping’. The current paper focuses on the modeling and analysis of thermal damping in tube bundles subjected to cross-flow. It is expected that the present attempt will help in establishing improved design guidelines with respect to damping in tube bundles.     

Liquid metal heat transfer in heat exchangers under low flow rate conditions

The present paper describes the liquid metal heat transfer in heat exchangers under low flow rate conditions. Measured data from some experiments indicate that heat transfer coefficients of liquid metals at very low Péclet number are much lower than what are predicted by the well-known empirical relations. The cause of this phenomenon was not fully understood for many years. In the present study, one countercurrent-type heat exchanger is analyzed using three, separated countercurrent heat exchanger models: one is a heat exchanger model in the tube bank region, while the upper and lower plena are modeled as two heat exchangers with a single heat transfer tube. In all three heat exchangers, the same empirical correlation is used in the heat transfer calculation on the tube and the shell sides. The Nusselt number, as a function of the Péclet number, calculated from measured temperature and flow rate data in a 50 MW experimental facility was correctly reproduced by the calculation result, when the calculated result is processed in the same way as the experiment. Finally, it is clarified that the deviation is a superficial phenomenon which is caused by the heat transfer in the plena of the heat exchanger.     

After heat removal by a closed secondary cooler circuit on the example of the advanced high temperature reactor AHTR 500 with central graphite column

The application of natural convection in connection with an after heat removal concept in general supports the claim for an inherent safety concept for advanced high temperature reactors (HTR). The effectivity of such an after heat removal (AHR) concept will be explored exemplarily for the process-heat reactor AHTR 500 with central graphite column by a thermohydraulic simulation of a secondary cooler circuit which is thermally connected with the primary circuit. This coupling is undertaken by an AHR-cooler located in the upper part of the graphite column. The heat removal from the secondary circuit is taking place outside of the reactor by a secondary heat exchanger under the assumption that the latter is cooled by a water capacity flow on an ambient temperature level. The developed calculation model determines iteratively the dynamic and thermal positions of equilibrium in the primary and secondary circuit which in the after heat removal mode of operation are exclusively run by natural convection. Different types of design for the central column heat exchanger (coaxial tube, U-tube and helically coiled tube heat exchanger) have been compared. For the secondary heat exchanger a parallel tube design has been supposed. The choice of the secondary flow medium as well as the most important limiting quantities influencing the transmission of heat via the secondary circuit during the after heat removal mode of operation are subject of a parameter study.     

欠热条件下非能动余热排出热交换器传热试验数值模拟

针对大型先进压水堆非能动余热排出热交换器设计和安全分析计算模型存在的重要缺陷,以AP1000的非能动余热排出热交换器为原型,采用3根C型管进行了非能动余热排出热交换器传热试验。然后采用流体计算软件对欠热试验工况进行了数值模拟,通过多次计算得到了传热管外传热计算可采用的传热关系式,选取的传热模型下的计算结果与试验结果符合较好。利用传热模型验证了AP1000的设计工况,发现AP1000非能动余热排出热交换器的设计能带走堆芯余热。本文研究可为大型先进压水堆设计和安全分析提供技术支撑。     

板式换热器在CARR中的应用

着重介绍了CARR工程中重水换热器、主换热器的选型及设计过程。通过安全性和经济性等方面的对比,可以看出板式换热器比套管式换热器更具有优越性。板式换热器在系统中的应用对今后的设计具有一定的参考价值。     

快堆钠-空气热交换器翅片管传热及阻力特性试验研究

钠-空气热交换器是钠冷快堆事故余热排出系统的重要设备之一，与外界环境一起构成事故下反应堆余热的最终热阱。由于钠-空气热交换器的换热管采用垂直布置的翅片管结构，空气在不同位置处冲刷换热管的流速以及角度不同，导致其传热特性及阻力特性与传统翅片管换热器有很大不同。本文以钠-空气热交换器工程设计需求为研究背景，设计了两种试验件分别进行空气冲刷角度为90°和30°时翅片管束传热与流动阻力特性试验研究。试验结果表明：对于相同管排，空气冲刷角度为90°时的翅片管的换热系数及阻力系数明显大于空气冲刷角度为30°时的翅片管；对于相同空气冲刷角度下的不同换热管排，第2排翅片管的换热系数最大。本文研究为钠-空气热交换器的设计及优化提供了理论依据。     

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

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。