蒸汽发生器二次侧两相流传热特性数值研究

以AP1000核电站蒸汽发生器为原型,建立蒸汽发生器二次侧"平均通道"模型,利用计算流体动力学软件ANSYS CFX,基于相界面模型对蒸汽发生器二次侧两相流流动和沸腾换热过程进行研究。结果表明:数值模拟计算方法能准确模拟蒸汽发生器二次侧汽液两相流沸腾和传热过程;满负荷运行时,流体由预热区经过泡核沸腾区过渡到稳定沸腾区,含汽率和传热系数沿流动方向逐渐增大,出口含汽率与该型号蒸汽发生器设计值符合较好,平均传热系数的模拟结果和JensLottes经验关联式的预测值基本一致。     

蒸汽发生器二次侧汽液两相流数值模拟

以大亚湾核电站蒸汽发生器为原型,在相似原理的指导下,建立了蒸汽发生器“单元管”三维物理模型,采用Particle模型和热力学相变模型,并基于CFX软件实现了蒸汽发生器二回路侧两相流流动与沸腾换热特性数值模拟。计算结果表明：满负荷运行时,沿传热管高度升高,蒸汽发生器的传热系数及截面含汽率均呈上升趋势,其平均传热系数的数值模拟结果与Rohsenow经验关联式计算结果间的误差为8.4%,出口质量含汽率与大亚湾核电站实际运行参数相符。热相变模型在蒸汽发生器两相流数值模拟中的成功应用,可为蒸汽发生器热工水力的准确分析提供参考。     

不同运行工况下蒸汽发生器热工水力稳态特性数值研究

基于相似模化理论建立了蒸汽发生器一、二回路流体及传热管流 固耦合传热的单元管三维物理模型,对大亚湾核电厂蒸汽发生器不同工况下的热工水力稳态特性进行了数值模拟研究。采用热相变模型描述二回路汽液两相流动与换热、流-固耦合模型描述一回路冷却剂借助U型管与二回路流体换热。数值计算结果表明：满负荷运行时,传热管内壁温度变化趋势与一次侧流体基本一致,外壁温度与二次侧流体温度变化趋势相同;截面平均含汽率沿传热管高度的升高呈上升趋势,出口质量含汽率与大亚湾核电厂实际运行参数相符;随负荷降低一回路出口温度基本不变,二回路出口温度升高,质量含汽率及传热系数下降,平均传热系数与Rohsenow经验关联式的计算结果基本吻合。     

蒸汽发生器传热管束过冷沸腾区两相流动数值模拟

基于两流体欧拉数学模型结合RPI壁面沸腾模型,利用大型商用CFD软件ANSYS CFX 12.0对蒸汽发生器传热管束过冷沸腾区一次侧、壁面和二次侧耦合传热过程进行了数值模拟。研究了三叶梅花孔支撑板和不同入口过冷度条件下蒸汽发生器传热管束内的流动沸腾现象,得到一、二次侧流场与温度场,二次侧空泡份额分布,支撑板梅花孔局部的流动状况及不同入口过冷度对蒸汽发生器热工水力特性的影响。数值模拟结果表明,三叶梅花孔支撑板的存在及不同入口过冷度对蒸汽发生器传热管束过冷沸腾区域的热工水力特性影响显著。     

螺旋管蒸汽发生器三维热工水力程序HeTAF开发

针对核动力系统螺旋管蒸汽发生器,本文采用多孔介质方法对具有复杂换热组件区域多层螺旋套管结构进行简化,构建了壳侧工质流动换热特性数学物理模型,并基于均相流假设建立了管侧水-水蒸气两相流动沸腾换热特性分析模型,采用网格-节点映射方法实现了管壳两侧耦合传热计算,基于开源OpenFOAM平台开发了适用于螺旋管蒸汽发生器的三维全尺寸热工水力特性分析程序HeTAF。基于螺旋管两相流动沸腾换热实验开展了模型验证,并以高温气冷堆示范工程中螺旋管直流式蒸汽发生器为分析对象开展了单换热组件模拟,获得的氦气和蒸汽出口温度计算结果与设计值符合较好,表明HeTAF能有效预测换热组件内管壳两侧流动换热特性。本文的研究对螺旋管蒸汽发生器的设计和安全分析具有参考意义。     

基于流热固耦合的核电蒸汽发生器传热管热应力数值模拟

以大亚湾核电站蒸汽发生器为原型,基于相似模化原理建立了蒸汽发生器简化物理模型。采用两流体模型及热弹性力学基本关系式分别描述气液两相流沸腾相变过程和热应力变化规律。利用CFX对一、二回路侧流体流动传热及与传热管的耦合换热过程进行了数值模拟,并在ANSYS WORKBENCH中实现了流体温度场载荷向结构的传递,进而对传热管进行稳态热分析和热应力分析。计算结果表明：二回路出口质量含汽率为24.5%,冷却剂出口温度为296.2 ℃,均与大亚湾蒸汽发生器实际运行参数相符;传热管热应力与其壁面温差分布一致,且沿壁厚方向先减小后增大,并存在中性层,传热管最大热应力为54.5 MPa。研究结果为蒸汽发生器的优化设计及安全运行提供了一定的理论支撑。     

螺旋管内热质传输行为与全工况预测模型研究

螺旋管式直流蒸汽发生器结构紧凑、传热高效、可靠性强,在先进小型堆中具有广泛应用,然而其管侧螺旋管内过冷水受热变为过热蒸汽,覆盖全部传热区域,且受螺旋几何、离心力及二次流影响,流动传热行为演化机制复杂,现有模型限制了高性能螺旋管式蒸汽发生器的进一步发展。本文针对螺旋管内热质传输行为开展了系统性实验和理论研究,建立了几何尺寸和热工参数范围最广泛的螺旋管传热、阻力基础热工实验数据库,明确了周向非均匀传热与沿程传热机制转变规律。基于机理分析,构建了高精度全工况的预测模型库,提出了三区干涸点、基于干度梯度的干涸后传热、宽范围两相摩擦倍增因子等模型,实现了全传热区域高精度预测。本文结果可满足先进反应堆螺旋管式蒸汽发生器设计需求。     

快堆蒸汽发生器沸腾传热恶化引起的热应力计算和分析

快堆管壳式直流蒸汽发生器发生沸腾传热恶化是不可避免的,由此引起的传热管管壁温度波动会使传热管受到疲劳破坏。研究蒸汽发生器的沸腾传热恶化及热疲劳破坏的实验昂贵,难度较大。本文依据国外已发表的实验结果,建立蒸汽发生器沸腾传热恶化发生时传热管管壁温度及热应力的分析模型,应用数值方法求解,对蒸汽压力、质量流速、钠汽温差变动的影响进行了讨论并给出了主要结论。     

快堆钠-水直流蒸汽发生器七管样机热工水力特性分析

钠-水直流蒸汽发生器是钠冷快堆主热传输系统的关键设备之一,其结构及内部的传热现象是十分复杂的。管内外侧的介质及压力不同,管内侧为高温高压的水/蒸汽,存在复杂的两相流动传热传质现象;管外侧为高温液态金属钠,沿换热管高度方向存在较大的钠温变化。本文以钠-水直流蒸汽发生器七管样机为研究对象,对其热工水力特性进行了CFD分析和实验研究,CFD分析结果和实验结果吻合较好,验证了CFD分析所采用的数学模型和数值方法的可靠性。结果表明,钠-水直流蒸汽发生器七管样机的传热面积是足够的,达到了设计指标要求,其界限质量含汽率约为0.42,临界热流密度约为451.98 kW/m²,从而确定了蒸干点的位置。     

沸腾传热数值模拟方法及多管耦合应用特性研究

针对直流蒸汽发生器（OTSG）中全流型沸腾传热及一、二次侧耦合换热等复杂物理现象,计算流体动力学（CFD）数值分析普遍面临计算难度大、计算效率低及不确定性大等问题。基于欧拉两流体多相流模型与临界热流密度（CHF）壁面沸腾模型,建立了管内全流型流动沸腾传热数值分析模型,并验证了模型的有效性。基于所验证的模型,开展了数值模型在多管耦合传热下的应用特性研究,明确了该数值模拟方法在多管耦合下的可靠性,并对温度与相分布计算结果对相间作用力模型的敏感性进行了数值分析。研究结果表明：基于欧拉两流体多相流模型与CHF壁面沸腾模型,能够较准确地预测管内水介质由过冷到过热的全流型流动沸腾传热过程,计算的“干涸”点位置及壁面峰值温度与实验值符合较好,最大误差小于10%;基于欧拉两流体多相流模型与CHF壁面沸腾模型的数值方法对多管耦合工况有较好的适用性,计算的二次侧温度与实验结果吻合良好;两相间曳力对壁面温度及空泡份额的计算结果有较明显的影响,但非曳力对壁面温度的影响较小,因此对于大规模工程应用计算,可在分析中不考虑部分相间非曳力的影响。本文研究结果可为OSTG的三维精细化数值分析的模型选择提供有益参考。     

盘管直流蒸汽发生器两相段计算模型

文章构造盘管直流蒸汽发生器（SG）两相段计算模型。采用四方程漂移流模型，对盘管直流SG的两相段传热进行进一步划分。选用适当的结构关系式和传热关系式，用数值方法进行了盘管SG的稳态分析。     

Experiment and Verification Test of the Once-through Steam Generator of the 10 MW High-temperature Gas-cooled Reactor Flow Stability of the Once-through Steam Generator

In January 2003, the 10MW High-temperature Gas-cooled Reactor (HTR-10) reached its full power for continuous operation of seventy-two hours in the Institute of Nuclear Energy Technology, Tsinghua University. The reactor operated smoothlyqbthe design parameters were successfully attained.

The once-through steam generator (SG) is one of key equipments of the HTR-10 reactor. The SG includes 30 modular heating helical tube assemblies. There are two thermal hydraulic requirements to be satisfied for the once-through steam generator: (1) enough heat transfer surface; (2) qualified steam can be produced under rated electrical generation power, and water-steam two phase flow un-stability can be avoided. In order to obtain the thermal hydraulic characteristics of the SG reliably, before design, a numerical code was developed for the design, and a full-scale test loop with two heating tubes as model was established, and series experiments had been carried out.

The purpose of this paper is to introduce the design of SG and researches on the stability of small bending radius helical coil-pipe used in HTR-10, for exempla, the effects of outlet steam pressure, inlet water sub-cooling degree, thermal power and inlet throttling degree. Up to now, the SG has experienced full power operation smoothly, and approvingly reached its original design requirements.

In the paper, some operational experimental data of the HTR-10 S.G have been presented.     

自然循环条件下蒸汽发生器倒U型管流量分配特性研究

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。      

Investigation of Pre- and Post-Dryout Heat Transfer in Upward Steam-Water Two-Phase Flow at Low Flow Rate

A heat transfer experiment was performed on steam-water two-phase flow in an annular flow path with a uniformly heated rod under the conditions of the mass flow rates from 0.2xlO⁶ to l.Ox 10⁶ kg/m²-h, inlet qualities from 0.5 to 1.0, heat fluxes below 4.7x 10⁵ W/m² and pressure of 31 bar. Dryout of the heater rod surface was observed resulting in the sharp rise of the heater rod surface temperature. Measured heat transfer coefficients were compared with the several empirical and semi-empirical correlations with the emphasis on the applicability of the correlations to the present test conditions being important in the analysis of the thermal hydraulic behavior during a LOCA of a nuclear reactor. The measured heat transfer coefficient in the pre-dryout region is lower than the existing correlations. The cooling of the heat transfer surface by the liquid phase in the post-dryout region is significant, which is neglected in the existing correlations. The heat transfer coefficients calculated for the post-dryout region by the Groeneveld correlation show good agreement with the presently measured results within the accuracy of 0~27%.     

Experimental and Operational Verification of the HTR-10 Once-Through Steam Generator (SG)

In January 2003, the 10MW High-temperature Gas-cooled Reactor (HTR-10) reached its full power for continuous operation of seventy-two hours in the Institute of Nuclear Energy Technology, Tsinghua University. The reactor was operated smoothly at the designated parameters. The once-through steam generator (SG) is one of key equipments of the HTR-10 reactor. The SG includes 30 modular heating helical tube assemblies. Design of the SG includes hydraulics, heat transfer and stability designs. Based on the design requirement, it is necessary to ensure sufficient heat removal from the reactor in order to maintain stable operation. In order to confirm the thermal hydraulic reliability of the SG, a series of experiments had been carried out. The purpose of this paper is to introduce the design features and experimental verification of HTR-10 SG, and the research results of small bending radius helical coil-pipe used in HTR-10, for example, the heat transfer coefficient of water, superheat steam and the two phase flow in the helical tube, the heat transfer coefficient of the He flow across the helical tube, and the centrifugal force effect on the heat transfer for the helical tube. In the paper, some operational experimental data of the HTR-10 SG have been presented.     

液态金属螺旋管式直流蒸汽发生器数值模拟研究

螺旋管式直流蒸汽发生器(HCOTSG)是一种蒸汽发生器常用形式。得益于其特殊的优势,HCOTSG被广泛用于各类反应堆动力系统中。本文提出了利用计算流体力学软件（FLUENT）对液态金属HCOTSG的壳侧液态铅铋、管侧两相流体进行耦合流动传热计算的CFD方法,并通过与相关实验研究结果的对比验证了数值模拟方法的正确性。在此基础上,本文对HCOTSG在典型工况下开展了数值模拟计算,得到蒸汽发生器内部的热工水力参数分布情况,并对其内部的流动换热特性进行分析。本研究为液态金属HCOTSG流动换热特性研究及结构设计优化提供新的思路方法。