Mathematical modeling and transient thermal-hydraulic analysis of boiling water reactors

This paper presents the development and practical application of a dynamic mathematical model for the simulation of the transient thermal-hydraulic analysis of Boiling Water Reactors (BWRs). In the development of the mathematical model, the reactor core thermal-hydraulic model for the coolant flow along the fuel pin channel is based on the moving boundary concept. Some results from the transient analysis are examined to evaluate the thermal-hydraulic performance of the mathematical model using moving boundaries. These analyses show that the predictions of the mathematical model based on the moving boundary formulation provide a suitable analytical tool for the transient thermal-hydraulic analysis of BWRs.     

Mathematical dynamic modeling and thermal-hydraulic analysis of HANARO

This paper describes the development of a dynamic model of HANARO (High-Flux Advanced Neutron Application Reactor), an open tank in pool type research reactor. The reliable dynamic model of the reactor and its cooling systems is developed to perform the thermal-hydraulic analysis for transients. The developed dynamic model is properly implemented in the transient simulation code, H-SIM, which is compiled and executed on a personal computer (PC) using the DESIRE simulation language. The H-SIM is intended for simulating efficiently the operational characteristics and the thermal-hydraulic behavior of HANARO for many transients. The simulation for HANARO transients shows a proper thermal-hydraulic behavior trend for the power step change. Results from the H-SIM with reference calculations are found in general to be very encouraging and the dynamic model is judged to be versatile to fulfill its intended purpose.     

Numerical analysis of flow instability in the water wall of a supercritical CFB boiler with annular furnace

In order to expand the study on flow instability of supercritical circulating fluidized bed (CFB) boiler, a new numerical computational model considering the heat storage of the tube wall metal was presented in this paper. The lumped parameter method was proposed for wall temperature calculation and the single channel model was adopted for the analysis of flow instability. Based on the time-domain method, a new numerical computational program suitable for the analysis of flow instability in the water wall of supercritical CFB boiler with annular furnace was established. To verify the code, calculation results were respectively compared with data of commercial software. According to the comparisons, the new code was proved to be reasonable and accurate for practical engineering application in analysis of flow instability. Based on the new program, the flow instability of supercritical CFB boiler with annular furnace was simulated by time-domain method. When 1.2 times heat load disturbance was applied on the loop, results showed that the inlet flow rate, outlet flow rate and wall temperature fluctuated with time eventually remained at constant values, suggesting that the hydrodynamic flow was stable. The results also showed that in the case of considering the heat storage, the flow in the water wall is easier to return to stable state than without considering heat storage.     

某410t/h锅炉水冷壁爆管的分析及对策

燃煤锅炉水冷壁爆管严重影响锅炉的运行,严重的爆管直接导致锅炉灭火.本文通过对某锅炉的运行分析,了解了水冷壁爆管的主要和次要因素,并提出一些可以解决的办法.     

Fluid-to-fluid modeling of supercritical water loops for stability analysis

The use of supercritical water as coolant/moderator may induce oscillations in the supercritical light water reactor similar to the density wave oscillations observed in boiling water reactors (BWRs). In order to experimentally investigate the stability of supercritical reactors, a fluid-to-fluid downscaled facility is proposed. It is found that with an appropriate mixture of refrigerants R-125 and R-32, the dimensionless enthalpy and density of the supercritical water can be accurately matched for all relevant operational conditions of the reactor. Moreover, the inertia distribution, the friction factor distribution and the heat transfer mechanism are taken into account in the modeling. As a result of the proposed downscaling, the operational pressure, temperature and power are considerably smaller than those of a water-based system, which in turn helps reducing the construction and operational costs of a test facility. Finally, it is found that the often used modeling fluid supercritical CO₂ cannot accurately represent supercritical water at reactor conditions.     

Near-wall modeling of an isothermal vertical wall using one-dimensional turbulence

One-dimensional turbulence (ODT) modeling approaches are considered for describing the heat transfer from a vertical isothermal wall. In this approach, near wall gas-phase conduction processes are treated exactly while the effect of turbulent mixing is accounted for using triplet mapping stirring events. A new buoyancy generation production term is proposed, based on the vorticity transport scaling arguments, to account for the generation of large scale eddy mixing events. Both temporal and spatial implementations of ODT are explored and compared to the experimental data of Tsuji and Nagano. Comparisons of velocity, temperature, and Nusselt number show overall excellent agreement of simulation results to experimental data and to established inner and outer scaling laws for buoyancy driven boundary layers.     

660MW超超临界机组循环水系统节能优化分析

冷端系统是火电厂发电机组重要的辅助系统,它的工作状态和运行特性对整个电站机组的稳定性、安全性和经济性都有较大的影响。对某660 MW超超临界机组两台循环水泵电机进行改造,增加了循环水泵运行方式(单机运行时一小、一大、一大一小;双机运行时二小、一大一小、二大、二大一小);建立了机组冷端性能分析计算模型,结合实际运行状况,给出了不同负荷、不同温升等工况下循环水泵组合优化运行方式;针对机组频繁启停状况,通过合理利用运行机组循环水,达到降低开停机过程循环水泵耗电量的目的。研究为同类机组冷端系统运行方式提供借鉴。     

某350 MW超临界锅炉前包墙边管泄露原因分析及处理

本文介绍了国内某350 MW超临界锅炉在机组运行期间,2#炉后烟道前包墙边管多次泄露并吹损集箱的原因分析,问题处理及后续改进措施。     

自然循环锅炉水冷壁温度计算方法及影响因素分析

研究了自然循环锅炉膜式水冷壁管的传热，采用编制程序对水冷壁进行温度场分布的计算，在研究方法上考虑了欠热沸腾起始点的问题，探讨了入口工质状态、炉内热流密度、质量流量、质量舍汽率等对水冷壁温度的影响。计算结果表明，入口水温的变化会影响欠热沸腾起始点的高度，但对温度的影响较小；炉内热流密度、质量流量和质量舍汽率的波动都会对温度产生影响，这主要是由于它们影响了换热系数的大小。     

1000 MW超超临界锅炉尾部烟道入口集箱引入管设计优化

本文介绍了1 000 MW超超临界锅炉尾部烟道入口集箱引入管的设计优化     

600MW超超临界锅炉最佳运行氧量试验研究

以国内某电厂600MW超超临界锅炉为研究对象,对其进行了变氧量试验研究,通过测量不同工况下锅炉运行各项热损失并计算热效率,进而结合辅机电耗计算供电煤耗,分析运行氧量对锅炉热效率、辅机电耗及供电煤耗的影响,得到最佳运行氧量值以使机组经济运行。结果表明,在600MW、500MW、360MW电负荷下,最佳运行氧量分别是将锅炉表盘氧量值偏置1.0(即3.82%附近)、偏置0.4(即4.16%附近)、偏置0.4(即5.49%附近)。研究结果可为运行人员调整运行方式提供参考。     

浅谈超超临界锅炉安装过程内部异物检查及清理措施

本文对超超临界锅炉安装过程中内部清洁度控制措施进行探讨,并对设备存放、安装施工,锅炉吹管等过程中,锅炉设备内部异物的检查、清理提出建议。     

2953t/h超临界锅炉垂直水冷壁水动力特性研究

建立超临界锅炉垂直水冷壁水动力特性计算模型,首先按出口工质温度相等的原则计算节流补偿压降,再以给定热的负荷以及节流方式进行了流量分配和压降特性校核计算,并研究了2953t/h超临界锅炉垂直水冷壁水动力特性。研究结果表明:以50%锅炉最大连续出力工况为基准来设计水冷壁入口节流压降是合理的,该方法可以使各负荷下的回路特性均趋于理想回路特性,能够获得较均匀的出口工质温度分布,热力偏差小并能够维持合适的水冷壁金属温度。水冷壁总压降的变化趋势与锅炉负荷变化相符。对于弱受热回路,重位压降所占总压降比例大于摩擦压降,因而弱受热具有自然循环特性;对于强受热回路,重位压降所占总压降比例小于摩擦压降,因而强受热回路具有直流特性。100%BMCR工况下,最高金属壁温为497℃,低于管材规定的580℃,因此锅炉机组的运行安全性可以得到保证。     

Mathematical modeling of an anion-exchange membrane water electrolyzer for hydrogen production

A mathematical model that considers coupled mass transport, charge transport, and electrochemical reactions in an anion-exchange membrane (AEM) water electrolyzer is developed. Validations against the literature experimental data show that the present model can accurately predict the performance of the water electrolyzer. Numerical results show that the voltage loss in the electrolyzer is majorly due to the activation polarizations of hydrogen and oxygen evolution reactions. The effects of the exchange current density, the membrane thickness, and the liquid saturation on the performance are also studied; it is shown that the performance of the water electrolyzer improves with an increase in the exchange current density and liquid saturation, but with a decrease in the membrane thickness.     

1000MW机组锅炉水冷壁泄漏原因分析

介绍了1000MW机组锅炉水冷壁泄漏时异常现象,并根据爆管的特征分析泄漏的原因.同时根据泄漏管运行工况、设备结构、金相分析查找裂纹的来源,制定出相应的防范措施.     

Mathematical modeling and simulation for external electrothermal characteristics of an alkaline water electrolyzer

The water electrolyzer is a key device in the direct energy interaction between the hydrogen production system and the fluctuation power supply. Therefore, to understand its external electrothermal characteristics and modeling, an efficient simulation method is not only theoretically significant but also of great value in engineering applications for the key techniques, such as the study of control strategy and optimum configuration of renewable energy generation. Currently, research studies on the electrothermal characteristics of the alkaline water electrolyzer (AWE) are focused mainly on the microcosmic mechanism, without sufficient emphasis on the modeling and simulation technique of the external macroscopic electrothermal characteristics. Based on relevant theories in electrochemistry and test results of the electrothermal characteristics, this paper establishes a mathematical model of the equivalent impedance characteristics, electrothermal characteristics, and power regulation characteristics of AWE. Then, a simulation model of the external electrothermal characteristics is built with Matlab/Simulink. Finally, the accuracy of the established mathematical model and the functionality of the simulation model are verified. The research can provide some reference for the modeling and simulation of the electrical characteristics of AWE.     

Development of a supercritical and an ultra-supercritical circulating fluidized bed boiler

The supercritical circulating fluidized bed (CFB) boiler, which combines the advantages of CFB combustion with low cost emission control and supercritical steam cycle with high efficiency of coal energy, is believed to be the future of CFB combustion technology. It is also of greatest importance for low rank coal utilization in China. Different from the supercritical pulverized coal boiler that has been developed more than 50 years, the supercritical CFB boiler is still a new one which requires further investigation. Without any precedentor engineering reference, Chinese researchers have conducted fundamental research, development, design of the supercritical CFB boilers independently. The design theory and key technology for supercritical CFB boiler were proposed. Key components and novel structures were invented. The first 600 MWe supercritical CFB boiler and its auxiliaries were successfully developed and demonstrated in Baima Power Plant, Shenhua Group as well as the simulator, control technology, installation technology, commissioning technology, system integration and operation technology. Compared with the 460 MWe supercritical CFB in Poland, developed in the same period and the only other supercritical one of commercial running in the word beside Baima, the 600 MWe one in Baima has a better performance. Besides, supercritical CFB boilers of 350 MWe have been developed and widely commercialized in China. In this paper, the updated progress of 660 MWe ultra-supercritical CFB boilers under development is introduced.     

350MW超临界直流锅炉结焦原因分析与改进

针对超临界直流锅炉水冷壁严重结焦、机组不能维持额定负荷连续运行的问题,通过优化燃烧控制策略,结焦问题得到有效缓解,机组能够满负荷连续稳定运行,机组运行安全性和经济性提高。     

转炉余热锅炉炉膛水冷壁泄漏案例分析

结合转炉余热锅炉运行工况,针对炉膛内水冷壁泄漏实际,综合分析缺陷产生原因和机理。     

1000MW超超临界二次再热机组热经济学分析

以1000MW超超临界二次再热机组为热经济学研究对象,将热力系统划分成若干个子系统,并绘制出机组热力系统的物理结构图和生产结构图,然后对其进行火用经济学分析,并指出了系统需要优化改进的组件。对设计条件下的单位热经济学成本构成计算,热力过程的成本形成和分布规律进行了深入的分析,揭示了能量损失具有不等价性。结果表明:该方法与传统分析方法相比,能够更加准确合理的评价机组的节能潜力,为其他大型火电机组及相关的复杂能量系统运行的经济性分析和优化改造提供了更加有效的方法。