共查询到17条相似文献,搜索用时 764 毫秒
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针对立式倒U型管自然循环蒸汽发生器传热管内的两相倒流现象,基于均相流模型,建立了U型管内低含气率两相流动传热理论模型,给出了U型管的进出口压降-质量流量曲线,分析了U型管内出现两相倒流现象的机理,研究了二次侧流体温度和入口含气率对倒流现象的影响规律,并与单相倒流进行了对比。利用RELAP5/MOD 3.3程序对相同条件下的倒流问题进行了计算。研究表明,提高蒸汽发生器二次侧工作压力可减少倒流,两相流入口含气率越高,倒流越易发生,两相流较单相流在U型管内更易倒流。 相似文献
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自然循环蒸汽发生器并联倒U型管流量分配计算 总被引:3,自引:3,他引:0
针对自然循环工况下蒸汽发生器部分倒U型管内存在倒流现象,通过对倒U型管内流动传热特性进行分析,获得了倒流发生的判断依据,从而编制了流量分配计算程序。采用该程序对某型蒸汽发生器并联倒U型管流量分配进行了计算,通过将结果与实验值进行对比分析,对程序可信度进行了验证,并采用该程序对蒸汽发生器并联倒U型管主要热工参数随进出口压降变化情况进行了计算分析。结果表明,倒流现象发生在短管内,倒流的发生使得蒸汽发生器一次侧净流量和单位时间输热呈阶梯下降,对反应堆安全产生较大的影响。 相似文献
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自然循环条件下,蒸汽发生器并联U型管束内存在单相流动不稳定性,部分U型管内存在倒流现象,对反应堆非能动安全产生负面影响。本文通过对基本守恒方程无量纲处理,采用线性扰动分析理论,获得了U型管内流动不稳定性判断准则(特征格拉晓夫数)。结果表明,当U型管格拉晓夫数高于特征格拉晓夫数时,管内流动是不稳定的,会出现倒流现象。以某型蒸汽发生器为对象,对U型管束流动不稳定性进行判断,通过与现有判别方法进行对比,验证了建立的U型管内流动不稳定性的判别方法。在此基础上,分析了蒸汽发生器一次侧流体入口密度对倒流现象的影响,发现当入口密度降低时,倒流现象更容易发生。本文结论可为蒸汽发生器优化设计提供一定的理论支持。 相似文献
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《Journal of Nuclear Science and Technology》2013,50(12):1252-1260
In this paper, we report on the analysis of reverse flow in inverted U-tubes of a steam generator under natural circulation condition. The mechanism of reverse flow in inverted U-tubes of the steam generator with natural circulation is graphically analyzed by using the full-range characteristic curve of parallel U-tubes. The mathematical model and numerical calculation method for analyzing the reverse flow in inverted U-tubes of the steam generator with natural circulation have been developed. The reverse flow in an inverted U-tube steam generator of a simulated pressurized water reactor with natural circulation is analyzed. Through the calculation, the mass flow rates of normal and reverse flows in individual U-tubes are obtained. The predicted sharp drop of the fluid temperature in the inlet plenum of the steam generator due to reverse flow agrees very well with the experimental data. This indicates that the developed mathematical model and solution method can be used to correctly predict the reverse flow in the inverted U-tubes of the steam generator with natural circulation. The obtained results also show that in the analysis of natural circulation flow in the primary circuit, the reverse flow in the inverted U-tubes of the steam generator must be taken into account. 相似文献
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自然循环U型管蒸汽发生器(UTSG)在一次侧处于自然循环工况下其部分U型管可能会出现倒流现象,这对自然循环带来不利影响。本文通过理论分析UTSG的U型管的水动力学曲线,获得U型管内发生流动不稳定时的临界压降与管长的关系,并利用系统分析程序RELAP5进行数值验证,验证结果表明:当管长增加时,临界压降呈先减后增的趋势,即小型的UTSG的最短U型管先出现倒流,而大型的UTSG最长管先出现倒流。所得结论解释了不同的仿真模拟研究得到的倒流管的分布不同的现象,为UTSG管内倒流及其管空间分布的预测提供理论依据。 相似文献
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蒸汽发生器(SG)倒U型管束内倒流问题增大了自然循环条件下SG的流动阻力,降低了系统自然循环能力,对反应堆安全产生了负面影响。针对上述问题,以船用SG为研究对象,分别采用理论分析和计算流体动力学(CFD)数值模拟方法,通过修圆并联倒U型管束内管板开孔,研究了采用改进方案前后管板的流量分配和倒流特性。结果表明,通过修圆短管管板开孔,在自然循环工况下能有效降低SG流动阻力,增大短管的流量分配,从而降低倒流临界流量,延缓倒流现象的发生。研究结论为SG倒U型管束内倒流问题提供了一种可行的解决方案,可以为解决倒流问题研究提供支持。 相似文献
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对浮动式核电站中一类具有倾斜热管段的低压低高差自然循环系统的两相流动特性进行了实验研究,分析了加热功率对两相流动特性的影响。结果表明,不同功率条件下系统存在两相稳定冷凝和伴随蒸汽冷凝诱发水锤两相振荡2种流动模式,热管段内过冷水倒流和蒸汽与低温过冷水直接接触冷凝是导致2种流动模式的内在机制。此外,蒸汽冷凝诱发水锤的发生会产生较大压力脉冲,并导致过冷水倒流长度显著增加,进而加剧系统流动不稳定。进一步研究表明,加热段出口含气率可以作为流动不稳定判断依据。 相似文献
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以欧洲压水堆热工实验装置(PWR PACTEL)一回路系统蒸汽发生器为研究对象,首先,基于流体一维流动模型的质量、动量和能量守恒方程建立管道进出口压降以及传热与流体流量之间的关系;其次,以遗传算法为基础开发倒U型管蒸汽发生器流量分配计算程序,采用基准实验对程序正确性和可靠性开展验证;最后,利用流量分配程序计算蒸汽发生器倒U型管管组的流量分布情况,研究管高、管长以及一/二次侧换热系数对蒸汽发生器内流量分配的影响。结果表明,所开发流量分配程序计算结果与实验吻合良好;在选定的自然循环工况下,该蒸汽发生器中长管更易发生倒流,且倒流现象呈现分布范围广、单管流量低的特点;倒U型管内正流流速与管长成反比,与管高成正比,倒流流速随着管长的增加保持不变,与管高呈反比关系;传热系数较低时,总流量与传热系数成反比关系,当传热系数高于特定值后部分管内发生倒流,总流量骤降。 相似文献
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Conclusions The large hydraulic nonuniformity of steam generator pipes operating in parallel in the natural coolant circulation regime
results in a lower efficiency of the heat-transfer surface during emergency cooldown of the reactor plant, and it limits the
operational possibilities, specifically, for using this regime at partial power levels. It is obvious that circulation reversal
in the pipes of steam generators in the natural circulation regime can have an unfavorable influence on individual structural
elements of steam generators as a result of additional temperature stresses appearing in the metal.
As one can see from Eq. (6), the conditions of the distribution of the coolant flow rate over pipes in a steam generator can
be improved at the design stage. Specifically, they can be realized as an efficient ratio of the “macrogeometric” characteristics
of the first loop ΔH and Hsgp as well as by the influence on the ratio of the hydraulic resistance of individual sections of the loop, which determine
the numerical value of the parameter m. As m increases, other conditions remaining the same, the character of the distribution
of the coolant flow rate in the pipes of a horizontal steam generator improves. Thus, designers of a nuclear power plant have
ways to search for optimal solutions. It is obvious that the interrelations of the conditions of operation of a steam generator,
examined above, and the natural circulation in the loop require that the distribution of the flow rate in a pipe bundle be
taken into account in the physical simulation using special thermohydraulic stands.
St. Petersburg State Technical University. Translated from Atomnaya énergiya, Vol. 83, No. 3, pp. 169–174, September, 1997. 相似文献