带喷射泵系统中自然循环过渡特性实验研究

将喷射泵引入与反应堆一回路系统相似的自然循环系统中，进行了实验研究，研究结果表明：安装喷射泵不仅可以提高系统自然循环能力。而且还可以改善系统自然循环过渡特性，系统初始流量和喷射泵的带流比对过渡过程的初期影响较大，加热段加热功率对整个过渡过程的影响都很显著，但加热段入门温度的影响并不明显。     

摇摆对自然循环传热特性影响的实验研究

对摇摆情况下单相自然循环流动的传热特性进行了实验研究.试验结果表明,摇摆运动下,自然循环的换热能力得到了加强,摇摆的频率和振幅增加,换热系数也相应增加.针对摇摆运动下换热系数经验公式的适用性进行了分析,并通过实验数据的拟合得出了适用于摇摆运动下的自然循环换热经验关系式.     

一体化小型堆主回路自然循环稳态特性实验研究

在模拟一体化小型堆主回路的自然循环试验台架上,进行了小型堆主回路自然循环稳态流动特性的实验研究。结果表明:在输入的外部条件保持一致的情况下,实验本体内的自然循环流动保持了很好的对称性;影响自然循环流量的主要因素是加热功率,入口温度、系统压力等参数的影响较小;提出了一个表征系统自然循环能力的综合特征参数k,可当作指标参数来衡量不同的自然循环回路或不同的运行工况下的自然循环能力,对进一步优化一体化自然循环反应堆的参数设计具有重要指导意义。     

自然循环系统中喷射泵特性的实验研究

在自然循环系统中安装喷射泵并进行了实验研究，研究结果表明，强迫循环时，喷射泵工作特性受回路影响较大，同时，调节冷，热段密度差可改变喷射泵在回路中的工作范围。为避免引射支路出现倒流现象，在实验及分析基础上提出自然循环系统中设计安装喷射泵的一些建议。     

自然循环流动阻力系统特性研究

研究了闭式自然循环实验回路单相流动阻力的系统特性。结果表明：在本文的实验参数范围内，以一维充分发展强迫流动关系式为基础的计算结果与实验结果相比有一定的偏离，这与ＲＦＬＡＰ５／ＭＯＤ２程序对ＬＳＴＦ等装置及ＤｏｅｌＰｌａｎｔ的分析结果基本一致。建立了自然循环流动阻力系统特性的归一化分析数学模型对实验数据进行归一化分析，得到了一组新的自然循环系统等效摩擦阻力系数的经验关系式。本文较大地拓宽了该基础研究领域的实验数据范围，从系统的角度确证了自然循环与强制流动存在的差别并分析其机理成因，结论可供先进反应堆的研究和设计参考。     

闭合回路单相自然循环稳态特性研究

针对闭合回路单相自然循环的特点,对回路流动的基本方程进行简化,得出稳态自然循环流量Ｇｓｔ与热功率Ｑ的１／（ｍ＋１）次方成正比,原流体进出口温差△Ｔｓｔ与加热功率Ｑ之间的ｍ／（ｍ＋１）次方成正比。     

稳态自然循环特性计算分析

在高温高压立式回路实验研究的基础上,利用RETRAN02 程序进行了稳态自然循环特性的验证性计算,计算结果与实验数据符合较好;利用该计算模型对某些参数作了敏感性研究,拓展了实验研究内容,加深了对系统自然循环特性的认识。     

自然循环静态流动不稳定研究

研究了发生静态流量漂移时自然循环系统中流量和加热段进出口温度的变化规律及静态流漂移过程中发生的动态流量振荡现象。研究结果表明：在发生静肪流量漂移时,系统循环流量下降,、加热段的进口温度下降而出口温度上升;当静态流量漂移一段时间后,伴随着静态流量漂移,系统内同时发生动态流量振荡。在对现象描述的基础上,阐述了静态流量漂移发生的机理。     

沸腾两相自然循环回路静态不稳定性的无量纲研究

定义了无量纲分析的参考尺度 ,采用无量纲分析的方法 ,运用一维均相模型 ,从理论上研究了两相自然循环系统的静态不稳定特性 ,总结出了影响两相自然循环系统静态稳定性的几个重要的无量纲参数。运用分岔理论及其DERPAR数值算法 ,得到了由无量纲量Npch m+表示的沸腾两相自然循环系统的静态分岔图 ,详细分析了由浮力和阻力随无量纲的加热功率的非线性的变化特性。并且给出了几个重要系统参数的效应图。     

喷射泵对自然循环过渡特性影响分析

分析了喷射泵在压水堆－回路自然循环过渡过程中的作用以及在不同流动条件下的阻力特性。分析结果表明：选择结构合理的喷射泵，可以改善压水堆一回路的过渡特性和自然循环能力；强迫循环条件下；压水堆一回路主循环泵有效压的损失随喷射泵阻力系数的增加而增加；自然循环条件下，喷射泵流动阻力系数影响压水堆一回路过度过程时间及自然循环流量的大小。为了改善压水堆一回路过度特性和提高一回路自然循环能力，可以采用无扩散段形式     

Non-dimensional analysis of static bifurcation in a natural circulation loop

The steady-state characteristics of a two-phase natural circulation loop were investigated based on the homogenous model. Transcendental equations of non-dimensional loop mass flow rate under various conditions were also derived. The static bifurcation diagram of a two-phase natural circulation described with non-dimensional variables Npch-m^＋ was obtained. In addition, various steady-state characteristics of a natural circulation loop were analyzed and discussed. These characteristics include the existence of multiple solutions under certain conditions, and the maximum mass flow rate. The authors also examined the effects of important parameters such as sub-cooling number, riser-to-heated-region length ratio, and riser-to-heated-region diameter ratio.     

Theoretical investigation on the steady-state natural circulation characteristics of a new type of pressurized water reactor

1 Introduction With respect to the inherent safety of nuclear re- actors, application of passive systems/components including natural circulation phenomena as the main mechanism is intended to simplify the safety-related systems and to improve their reliability, to reduce the effect of human errors and equipment failures, and to provide more time to enable the operators to prevent or mitigate serious accidents. Natural circulation is the main mode of heat removal for removing decay heat from t…     

核动力装置强迫循环与自然循环过渡过程特性研究

针对某型压水堆核动力装置,建立反应堆及一回路系统强迫循环与自然循环的计算分析模型,并与试验值进行比较,验证了建立的模型计算精度高,满足工程分析的要求.利用建立的数学模型,对自然循环与强迫循环过渡过程进行分析计算,结果表明:强迫循环向自然循环转换过程中冷却剂流量、蒸汽发生器压力、反应堆出口温度是几个约束参数;自然循环向强迫循环的转换过程中反应堆功率变化与周期变化幅度较大.     

Experimental investigation of natural circulation in a symmetrical loop under large scale rolling motion conditions

In ocean environment, the ship motion significantly affects the natural circulation behavior in ship-based integrated-type reactor. This paper theoretically and experimentally investigated natural circulation characteristics in symmetrical loops under rolling condition. Experiments were carried out on a test loop with a symmetrical configuration by simulating the structure of an accrual reactor. The theoretical results revealed that only angular acceleration contributes to the resultant force under zero power rolling condition. In a closed circuit with a uniform cross-section area, the angular acceleration force integral is proportional to the angular acceleration and the area enclosed by the circuit. The integral value varies over time and causes flow oscillations. However, the angular acceleration force does not influence the flow status in the shared part of the two symmetrical neighbor circuits due to force interactions. Rolling experiments with a zero power load confirmed these results. Full power experiments under rolling condition exhibited observable flow rate and temperature oscillations in each branch of the flow channel. The oscillations in the side flow channels had the same values for both the period and the phase with the variation of rolling angle. The angular acceleration force was the main cause of this. The oscillations in the middle channel had a period half the value of the rolling period. The periodical variation of the vertical component of gravity caused this. The horizontal component of gravity was out-phasing with angular acceleration. Therefore, it alleviated oscillation in the side channels. The experimental results showed that for the same rolling period, as the rolling angle increased, the average flow rate decreased and oscillation amplitudes increased. Also, as the power load increased, the oscillations in the middle channel increased and the oscillation in the side channel decreased.     

An analytical investigation of role of expansion tank in semi-closed two-phase natural circulation loop

Role of the expansion tank in a semi-closed two-phase natural circulation loop was examined analytically with the emphasis placed on the flow instability. Loopwise steady circulation rate was obtained, and conditions for flow instability were examined by using the method of the linear stability analysis with perturbations. The homogeneous two-phase model was adopted for the analysis. As well as the pressure at the expansion tank, the length and the cross-sectional area of the tube connected to the expansion tank appeared to be the important parameters determining the flow instability. The system was predicted to be stable with the longer length and the smaller cross-sectional area of the expansion-tank line and also with the higher expansion-tank pressure.     

Experimental investigation of natural circulation instability in a BWR-type small modular reactor

The Purdue NMR (Novel Modular Reactor) represents a BWR-type small modular reactor with a significantly reduced reactor pressure vessel (RPV). Specifically, the NMR is one third the height and area of a conventional BWR RPV with an electrical output of 50 MWe. Experiments are performed in a well-scaled test facility to investigate the thermal hydraulic flow instabilities during the startup transients for the NMR. The scaling analysis for the design of natural circulation test facility uses a three-level scaling methodology. Scaling criteria are derived from non-dimensional field and constitutive equations. Important thermal hydraulic parameters, e.g. system pressure, inlet coolant flow velocity and local void fraction, are analyzed for slow and fast normal startup transients. Flashing instability and density wave oscillation are the main flow instabilities observed when system pressure is below 0.5 MPa. And the flashing instability and density wave oscillation show different type of oscillations in void fraction profile. Finally, the pressurized startup procedure is recommended and tested in current research to effectively eliminate the flow instabilities during the NMR startup transients.     

低流速自然循环过冷沸腾汽泡脱离点实验研究

针对低流速环形通道中自然循环过冷沸腾汽泡脱离点特性进行了实验研究,运用Saha-Zuber模型、Bowring模型、Forster模型和Levy模型测算汽泡脱离点的位置,与实验值进行比较,发现由于流速较低,上述模型不适用于计算本实验条件下的汽泡脱离点。以Levy模型为基础,修正了浮力项的影响系数,修正后的模型与实验结果符合良好。     

Theoretical and experimental study on single-phase natural circulation under inclined conditions

The natural circulation reactor is widely used in marine environments where thermo-hydraulic performance is heavily affected by the heaving, pitching, and inclining of a ship. This paper theoretically and experimentally investigated steady-state single-phase natural circulation under inclined conditions. Results showed that energy transported by natural circulation was proportional to 1.5 times the power of the temperature difference between the hot leg and the cold leg. Furthermore, a parameter, k, was presented that revealed the comprehensive influence of working fluid properties, resistance characteristics, gravity fields, and loop configurations. k was treated as the criterion for the circulation ability of a loop and it also acted as the basis for evaluating and optimizing different designs. Analysis under the guidance of k was confirmed by a series of experiments performed on a symmetrical two-circuit loop. Both theoretical and experimental results showed that the inclination restrained overall circulation due to the decrease in average altitude difference between the steam generators and the electric heater. The disparity in branch circulations increased with the increase in the inclined angle. A loop design consisting of a large altitude difference and a small width was preferable to confine the influence of inclination. However, if the loop width was too small, it caused a severe reduction in the circulation ability for large angle inclinations.     

Bifurcation and hysteresis phenomena in the two－phase natural circulation system

The static bifurcation of the two-phase natural circulation (TPNC) system was studied theoretically and numerically.By the DERPAR algorthm the solution diagram was calculated,which shows that the static bifurcation occurs under some conditions in the TPNC systems.Also,it shows that the static bifurcation occurs under some conditions in the TPNC systems.Also,it shows that,in a region of multiple solutions.the static instability may occur.It is defined as a region of thermal-siphon instability induced flow rate jumping.By means of the solution diagram,the stability margin can be determined in this region.Furthermore.the heat input at the peak of the solution diagram is defined as the maximum capacity of heating load that can be used to judge the capacity of the TPNC of a given geometry topological structure,Meanwhile,it is interesting that the TPNC systems have the hystersis phenomenon defined as thermal-siphon hysteresis.Some parametric effects related were also studied.