Di Wang, Ren Liang, Zhikang Lin, Yong Ouyang, Yonggang Shen, Xianghui Lu, S. Qiu
In hypothetical steam generator tube rupture (SGTR) accident scenario of pool-type liquid metal cooled fast breeder reactor, water is injected from SG into primary circuit through the break and flash. The injected steam bubbles may transport into the core region and insert positive reactivity, which threaten the reactor safety. To accurately predict the void fraction for evaluation of accident consequence, drift flux model applied to gas-liquid metal two-phase flow is useful and need to be developed. In this contribution, an algebraic model aimed at bubble induced turbulence (BIT) is introduced to improve the underestimation of turbulent viscosity calculated by Clark’s force balance model to accurately predict the one-dimensional liquid velocity distribution along radial direction in flow channel. On this basis, the distribution parameter is calculated. Analysis result shows that distribution parameter is assuming very high values at low Re number. With Froude number increase, distribution parameter tends to decrease. At lower void factions, distribution parameter is also assumed to be high values. It indicates that the pipe size, flow rate and void fraction can all influence distribution parameter. Considering the quantitative laws of above influence factors obtained by theoretical analysis and fitting test data, a new correlation for gas-liquid metal two-phase flow is developed and evaluated.
{"title":"Development of Drift Flux-Type Correlations Considering Bubble Induced Turbulence in Vertical Gas-Liquid Metal Two-Phase Flow","authors":"Di Wang, Ren Liang, Zhikang Lin, Yong Ouyang, Yonggang Shen, Xianghui Lu, S. Qiu","doi":"10.1115/icone29-93078","DOIUrl":"https://doi.org/10.1115/icone29-93078","url":null,"abstract":"\u0000 In hypothetical steam generator tube rupture (SGTR) accident scenario of pool-type liquid metal cooled fast breeder reactor, water is injected from SG into primary circuit through the break and flash. The injected steam bubbles may transport into the core region and insert positive reactivity, which threaten the reactor safety. To accurately predict the void fraction for evaluation of accident consequence, drift flux model applied to gas-liquid metal two-phase flow is useful and need to be developed. In this contribution, an algebraic model aimed at bubble induced turbulence (BIT) is introduced to improve the underestimation of turbulent viscosity calculated by Clark’s force balance model to accurately predict the one-dimensional liquid velocity distribution along radial direction in flow channel. On this basis, the distribution parameter is calculated. Analysis result shows that distribution parameter is assuming very high values at low Re number. With Froude number increase, distribution parameter tends to decrease. At lower void factions, distribution parameter is also assumed to be high values. It indicates that the pipe size, flow rate and void fraction can all influence distribution parameter. Considering the quantitative laws of above influence factors obtained by theoretical analysis and fitting test data, a new correlation for gas-liquid metal two-phase flow is developed and evaluated.","PeriodicalId":325659,"journal":{"name":"Volume 7B: Thermal-Hydraulics and Safety Analysis","volume":"71 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123830970","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. Yuan, Jian Deng, Z. Qiu, Qinglan Xu, D. Zhu, Tao Huang, Zhongchun Li, Peng Du
Loss of coolant accident (LOCA) is one of the most important accidents in thermal hydraulic design of nuclear power plant. The traditional analysis method is difficult to realize the rapid prediction of the size and location of the break in the LOCA, while machine learning provides an idea for the rapid diagnosis of the initial cause of LOCA. In this paper HPR1000 which is independently designed by China was taken as the object, the process of LOCA under various break location and sizes is studied by using the advanced reactor system analysis code ARSAC (Advanced Reactor System Analysis Code). The key thermal hydraulic parameters including temperature, pressure, flow rate and water level in the transient process of LOCA are analyzed, and a series of data sets are generated. Based on convolution neural network algorithm of deep learning, the transient thermal hydraulic parameters of HPR1000 under different working conditions are learned and the accident diagnosis model is obtained. By comparing with the test data, the trained model can quickly and accurately predict the size and location of LOCA, which can be subsequently extended to the diagnosis of other kinds of accidents in nuclear power plants and has certain application prospects.
失冷剂事故是核电站热工水力设计中最重要的事故之一。传统的分析方法难以实现对LOCA断裂的大小和位置的快速预测，而机器学习为LOCA的初始原因的快速诊断提供了思路。本文以中国自主设计的HPR1000为研究对象，采用先进反应堆系统分析规范ARSAC (advanced reactor system analysis code)，研究了不同破断位置和破断尺寸下的失稳过程。分析了LOCA瞬态过程中温度、压力、流量、水位等关键热工参数，生成了一系列数据集。基于深度学习卷积神经网络算法，学习了HPR1000在不同工况下的瞬态热液参数，建立了事故诊断模型。通过与试验数据的对比，训练后的模型能够快速准确地预测出事故的大小和位置，并可推广到核电厂其他类型事故的诊断中，具有一定的应用前景。
{"title":"Data Driven Methods for Break Size and Location Estimation in LOCA Based on Deep Learning","authors":"P. Yuan, Jian Deng, Z. Qiu, Qinglan Xu, D. Zhu, Tao Huang, Zhongchun Li, Peng Du","doi":"10.1115/icone29-92380","DOIUrl":"https://doi.org/10.1115/icone29-92380","url":null,"abstract":"\u0000 Loss of coolant accident (LOCA) is one of the most important accidents in thermal hydraulic design of nuclear power plant. The traditional analysis method is difficult to realize the rapid prediction of the size and location of the break in the LOCA, while machine learning provides an idea for the rapid diagnosis of the initial cause of LOCA. In this paper HPR1000 which is independently designed by China was taken as the object, the process of LOCA under various break location and sizes is studied by using the advanced reactor system analysis code ARSAC (Advanced Reactor System Analysis Code). The key thermal hydraulic parameters including temperature, pressure, flow rate and water level in the transient process of LOCA are analyzed, and a series of data sets are generated. Based on convolution neural network algorithm of deep learning, the transient thermal hydraulic parameters of HPR1000 under different working conditions are learned and the accident diagnosis model is obtained. By comparing with the test data, the trained model can quickly and accurately predict the size and location of LOCA, which can be subsequently extended to the diagnosis of other kinds of accidents in nuclear power plants and has certain application prospects.","PeriodicalId":325659,"journal":{"name":"Volume 7B: Thermal-Hydraulics and Safety Analysis","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121562849","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jinsong Guo, Xueyuan Zhang, Haiqi Zhao, D. Lu, Yuhao Zhang
The passive decay heat removal system based on natural circulation can passively remove the heat from the core, which greatly improves the safety of the nuclear reactor. The Plant Dynamics Test Loop (PLANDTL-DHX) experimental facility can simulate the flow and heat transfer characteristics of the pool-type sodium-cooled fast reactor with an independent decay heat removal system in a natural circulation state. However, the natural circulation experiments based on the PLANDTL-DHX facility are difficult to present the detailed flow characteristics in the core completely. So it is necessary to adopt numerical simulation analysis to obtain the flow characteristics in the core. While due to the complex structure of the core with wrapped wire bundles, the modeling and calculation of the pool-type fast reactor need very rich computing resources. To reduce the demand for computing resources, the model can be simplified to some extent. In this study, two modeling methods are adopted for the core: 1. The model of the rod bundles and wrapped wires are simplified by the porous media model; 2. The wrapped wires are simplified by the porous media model, while the rod bundles are retained. The PLANDTL-DHX experimental facility modeled by two different core modeling methods is numerically simulated. By analyzing and comparing the experimental data of PLANDTL-DHX, the feasibility of two different modeling methods for numerical simulation research is verified. By analyzing and comparing the calculation results of two different modeling methods, the flow characteristics in the core during natural circulation are also obtained, and the characteristics of different modeling methods are summarized. This work can provide a reference for the safety analysis and simulation calculation of pool-type sodium-cooled fast reactor.
基于自然循环的被动衰变排热系统可以被动地将堆芯的热量排出，大大提高了核反应堆的安全性。Plant Dynamics Test Loop (PLANDTL-DHX)实验装置可以模拟具有独立衰变排热系统的池式钠冷快堆在自然循环状态下的流动和传热特性。然而，基于PLANDTL-DHX设备的自然循环实验难以完整地呈现岩心内的详细流动特征。因此，有必要采用数值模拟分析来获得岩心内的流动特性。而池型快堆由于堆芯包线束结构复杂，其建模和计算需要非常丰富的计算资源。为了减少对计算资源的需求，可以对模型进行一定程度的简化。在本研究中，对核心采用了两种建模方法:采用多孔介质模型简化了杆束和绕丝的模型;2. 多孔介质模型简化了包裹导线，同时保留了杆束。采用两种不同的堆芯建模方法对PLANDTL-DHX实验装置进行了数值模拟。通过对PLANDTL-DHX实验数据的分析比较，验证了两种不同建模方法进行数值仿真研究的可行性。通过分析比较两种不同建模方法的计算结果，得出了岩心自然循环过程中的流动特性，总结了不同建模方法的特点。该工作可为池式钠冷快堆的安全性分析和仿真计算提供参考。
{"title":"Three-Dimensional Numerical Simulation of the Natural Circulation Characteristics Based on PLANDTL-DHX for Different Modeling Methods of the Core","authors":"Jinsong Guo, Xueyuan Zhang, Haiqi Zhao, D. Lu, Yuhao Zhang","doi":"10.1115/icone29-92364","DOIUrl":"https://doi.org/10.1115/icone29-92364","url":null,"abstract":"\u0000 The passive decay heat removal system based on natural circulation can passively remove the heat from the core, which greatly improves the safety of the nuclear reactor. The Plant Dynamics Test Loop (PLANDTL-DHX) experimental facility can simulate the flow and heat transfer characteristics of the pool-type sodium-cooled fast reactor with an independent decay heat removal system in a natural circulation state. However, the natural circulation experiments based on the PLANDTL-DHX facility are difficult to present the detailed flow characteristics in the core completely. So it is necessary to adopt numerical simulation analysis to obtain the flow characteristics in the core. While due to the complex structure of the core with wrapped wire bundles, the modeling and calculation of the pool-type fast reactor need very rich computing resources. To reduce the demand for computing resources, the model can be simplified to some extent. In this study, two modeling methods are adopted for the core: 1. The model of the rod bundles and wrapped wires are simplified by the porous media model; 2. The wrapped wires are simplified by the porous media model, while the rod bundles are retained. The PLANDTL-DHX experimental facility modeled by two different core modeling methods is numerically simulated. By analyzing and comparing the experimental data of PLANDTL-DHX, the feasibility of two different modeling methods for numerical simulation research is verified. By analyzing and comparing the calculation results of two different modeling methods, the flow characteristics in the core during natural circulation are also obtained, and the characteristics of different modeling methods are summarized. This work can provide a reference for the safety analysis and simulation calculation of pool-type sodium-cooled fast reactor.","PeriodicalId":325659,"journal":{"name":"Volume 7B: Thermal-Hydraulics and Safety Analysis","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115663556","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In order to better understand the heat transfer performance of shell and tube heat exchanger (STHE) with Fluoride salt as the heat transfer fluids, the steady-state heat transfer process of STHE with segmental baffles (STHE-SBs) in Fluoride-salt High Temperature Test Loop (FHTL) has been studied experimentally and numerically. Firstly, the Computational Fluid Dynamics (CFD) model was established to simulate the thermal performance of STHE-SBs. Then, thermal performance data such as temperature and heat transfer power were experimentally obtained under steady-state conditions of STHE-SBs at higher temperature (550–600°C), and to further verify the reliability of the simulation. The results show that the temperature distribution obtained by CFD is in good agreement with the experimental results, which indicates that the CFD program is reliable to describe the thermal performance of the STHE-SBs. On this basis, the effect of segmental baffles on the heat transfer enhancement of molten salt in shell side of STHE was discussed. The results show that the heat transfer enhancement effect of molten salt on the shell side of STHE-SBs is better than that of STHE without segmental baffles, and the increment of Nusselt number is about 64–73% during the low Reynolds number region. Finally, the heat transfer coefficient of molten salt in the shell side of STHE-SBs are fitted, which can be used in relatively wide ranges of Reynolds number and temperature.
{"title":"Experimental and Numerical Study on Convective Heat Transfer Characteristic in the Turbulent Region of Molten Salt in Shell-Side of Shell and Tube Heat Exchanger","authors":"Meng-Ting Ding, Yu-Shuang Chen, Yuan Fu","doi":"10.1115/icone29-92752","DOIUrl":"https://doi.org/10.1115/icone29-92752","url":null,"abstract":"\u0000 In order to better understand the heat transfer performance of shell and tube heat exchanger (STHE) with Fluoride salt as the heat transfer fluids, the steady-state heat transfer process of STHE with segmental baffles (STHE-SBs) in Fluoride-salt High Temperature Test Loop (FHTL) has been studied experimentally and numerically. Firstly, the Computational Fluid Dynamics (CFD) model was established to simulate the thermal performance of STHE-SBs. Then, thermal performance data such as temperature and heat transfer power were experimentally obtained under steady-state conditions of STHE-SBs at higher temperature (550–600°C), and to further verify the reliability of the simulation. The results show that the temperature distribution obtained by CFD is in good agreement with the experimental results, which indicates that the CFD program is reliable to describe the thermal performance of the STHE-SBs. On this basis, the effect of segmental baffles on the heat transfer enhancement of molten salt in shell side of STHE was discussed. The results show that the heat transfer enhancement effect of molten salt on the shell side of STHE-SBs is better than that of STHE without segmental baffles, and the increment of Nusselt number is about 64–73% during the low Reynolds number region. Finally, the heat transfer coefficient of molten salt in the shell side of STHE-SBs are fitted, which can be used in relatively wide ranges of Reynolds number and temperature.","PeriodicalId":325659,"journal":{"name":"Volume 7B: Thermal-Hydraulics and Safety Analysis","volume":"2017 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114764911","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wire Mesh Sensor (WMS) is an advanced two-phase flow measurement device, which has been widely applied in experimental research and industrial production. Previous research has shown that the measurement uncertainty of the WMS increases with the increase of the axial distance between the two layers of the electrode wires. Moreover, the structure of dual layers of wire mesh limits the application of WMS in complex flow channels. For example, the structure of the rod bundle channel needs to be carefully designed to install WMS. Thus, a novel WMS with only a single layer of electrode mesh was proposed. The transmitter wires and the receiver wires were intertwined with each other to increase the stability. The signal response of the single-layer WMS was investigated by the potential field simulation. For the bubble with a diameter of two times the mesh size passing through the WMS, the signal response of the single-layer WMS is closer to the ideal signal compared with the two-layer WMS. For the bubble with a diameter of one time the mesh size, the single-layer WMS overestimates the void fraction. Near the intersection, the distance between the receiver and the transmitter is small, more currents would be received by the per length receiver wire. When the bubble contacts the single-layer WMS, it first wraps the highly sensitive wires, which leads to the void fraction being overestimated.
{"title":"Numerical Simulation of Single-Layer Wire-Mesh Sensor","authors":"Hengwei Zhang, Yao Xiao","doi":"10.1115/icone29-93487","DOIUrl":"https://doi.org/10.1115/icone29-93487","url":null,"abstract":"\u0000 Wire Mesh Sensor (WMS) is an advanced two-phase flow measurement device, which has been widely applied in experimental research and industrial production. Previous research has shown that the measurement uncertainty of the WMS increases with the increase of the axial distance between the two layers of the electrode wires. Moreover, the structure of dual layers of wire mesh limits the application of WMS in complex flow channels. For example, the structure of the rod bundle channel needs to be carefully designed to install WMS. Thus, a novel WMS with only a single layer of electrode mesh was proposed. The transmitter wires and the receiver wires were intertwined with each other to increase the stability. The signal response of the single-layer WMS was investigated by the potential field simulation. For the bubble with a diameter of two times the mesh size passing through the WMS, the signal response of the single-layer WMS is closer to the ideal signal compared with the two-layer WMS. For the bubble with a diameter of one time the mesh size, the single-layer WMS overestimates the void fraction. Near the intersection, the distance between the receiver and the transmitter is small, more currents would be received by the per length receiver wire. When the bubble contacts the single-layer WMS, it first wraps the highly sensitive wires, which leads to the void fraction being overestimated.","PeriodicalId":325659,"journal":{"name":"Volume 7B: Thermal-Hydraulics and Safety Analysis","volume":"143 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122079364","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Helical tube bundles are usually used for intermediate heat exchangers (IHXs) of High Temperature Gas-cooled Reactors (HTGRs) due to its compactness and low thermal stresses. To clarify the influences of smaller tube pitches, experiments of cross flow over tube bundle with pitch to diameter ratio (P/D) of 1.4 were carried out in a wind tunnel. The time-averaged pressure, pressure fluctuations, and velocity distributions were measured in the fully developed region of the tube bundle. The flow pattern in tube bundles will vary with the Reynolds number. The flow field tends to show an oblique flow phenomenon when Re = 10285, 18000, 44571 and 52500. The turbulent wakes over left four tube layers tend to flow left while the turbulent wakes over right four tube layers tends to flow right. When Re = 36000, the oblique flow phenomenon of the flow field diminished. When Re = 25285, two obvious quasi-stable flow patterns were observed according to the measured surface pressure and the velocity distributions measured by Particle Image Velocimetry (PIV).
{"title":"Experimental Study of the Bistable Phenomenon in Cross Flow Over Inline Tube Bundle With P/D = 1.4","authors":"Xiaoyang Xie, Anxiang Ma, Houjian Zhao, Xiaowei Li, Xin-xin Wu","doi":"10.1115/icone29-92456","DOIUrl":"https://doi.org/10.1115/icone29-92456","url":null,"abstract":"Helical tube bundles are usually used for intermediate heat exchangers (IHXs) of High Temperature Gas-cooled Reactors (HTGRs) due to its compactness and low thermal stresses. To clarify the influences of smaller tube pitches, experiments of cross flow over tube bundle with pitch to diameter ratio (P/D) of 1.4 were carried out in a wind tunnel. The time-averaged pressure, pressure fluctuations, and velocity distributions were measured in the fully developed region of the tube bundle. The flow pattern in tube bundles will vary with the Reynolds number. The flow field tends to show an oblique flow phenomenon when Re = 10285, 18000, 44571 and 52500. The turbulent wakes over left four tube layers tend to flow left while the turbulent wakes over right four tube layers tends to flow right. When Re = 36000, the oblique flow phenomenon of the flow field diminished. When Re = 25285, two obvious quasi-stable flow patterns were observed according to the measured surface pressure and the velocity distributions measured by Particle Image Velocimetry (PIV).","PeriodicalId":325659,"journal":{"name":"Volume 7B: Thermal-Hydraulics and Safety Analysis","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132231512","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The thermophysical properties of supercritical fluids (SCF) will change drastically in the narrow range of thermodynamic conditions near the pseudo-critical line, and this narrow region of thermodynamic parameters is named the pseudo-critical region. The complex fluctuation of thermophysical properties in the pseudo-critical region makes SCF’s thermal-hydraulic characteristics very different from that of subcritical fluids. Therefore, the normal flow and heat transfer prediction models are no longer applicable among this region. From the perspective of engineering application, it is very necessary to determine the pseudo-critical line and pseudo-critical region as a reference point for adjusting thermodynamic parameters and improving the processing efficiency in the application of SCF. In the paper, supercritical carbon dioxide is taken as the research object. First, the pseudo-critical lines were obtained respectively according to three different equations of state. Then, based on the continuous phase transition theory, the pseudo-critical region was determined by the Ehrenfest equation. Finally, the occurrence area of heat transfer deterioration was in alignment with the proposed pseudo-critical region, and the mechanism that affects the heat transfer deterioration behavior was analyzed.
{"title":"Simulation of Pseudo-Critical Line Based on Different Equation of State and Definition of Pseudo-Critical Region","authors":"Xuebin Zhao, Suhao Wang, Rui-long Liu, Xiuting Liu, Yan-ping Huang","doi":"10.1115/icone29-94432","DOIUrl":"https://doi.org/10.1115/icone29-94432","url":null,"abstract":"\u0000 The thermophysical properties of supercritical fluids (SCF) will change drastically in the narrow range of thermodynamic conditions near the pseudo-critical line, and this narrow region of thermodynamic parameters is named the pseudo-critical region. The complex fluctuation of thermophysical properties in the pseudo-critical region makes SCF’s thermal-hydraulic characteristics very different from that of subcritical fluids. Therefore, the normal flow and heat transfer prediction models are no longer applicable among this region. From the perspective of engineering application, it is very necessary to determine the pseudo-critical line and pseudo-critical region as a reference point for adjusting thermodynamic parameters and improving the processing efficiency in the application of SCF. In the paper, supercritical carbon dioxide is taken as the research object. First, the pseudo-critical lines were obtained respectively according to three different equations of state. Then, based on the continuous phase transition theory, the pseudo-critical region was determined by the Ehrenfest equation. Finally, the occurrence area of heat transfer deterioration was in alignment with the proposed pseudo-critical region, and the mechanism that affects the heat transfer deterioration behavior was analyzed.","PeriodicalId":325659,"journal":{"name":"Volume 7B: Thermal-Hydraulics and Safety Analysis","volume":"81 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134140420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
During the reflooding process after a loss-of-coolant-accident (LOCA) scenario, the highly superheated fuel surface of the reactor core will undergo a quenching process. The temperature of the fuel element surface drops sharply during the quenching process, because large droplets can pass through the vapor film to re-wet the wall surface, and the boiling mechanism is transformed from film boiling to nucleate boiling, the boiling heat transfer perfomance is greatly improved. But the transition of the boiling mechanism is closely related to the initial velocity of the droplet, the size of the droplet, and the wall temperature. At the same time, after the droplets hit the wall surface, dynamic wetting behaviors such as deposition, vibration, rebound, or splashing will occur. Unfortunatly, the mechanism of droplet wetting behavior on boiling heat transfer is not clear, so it is necessary to carry out a fundamental research. In this study, the droplet size, initial droplet velocity, substrate’s temperature and surface tilt angle were precisely controlled. The images were captured by a high-speed camera to obtain a dynamic wetting image of the droplets impacting the wall from room temperature to 400°C. Finally, based on the image analysis method, a simple analysis of the three-phase contact line movement and the droplet dynamic wetting behavoir is performed.
{"title":"Dynamic Wetting Behavior During Droplet Impacting on a Superheated Surface","authors":"Mingjing Chen, D. Chen, Hanzhou Liu","doi":"10.1115/icone29-93252","DOIUrl":"https://doi.org/10.1115/icone29-93252","url":null,"abstract":"\u0000 During the reflooding process after a loss-of-coolant-accident (LOCA) scenario, the highly superheated fuel surface of the reactor core will undergo a quenching process. The temperature of the fuel element surface drops sharply during the quenching process, because large droplets can pass through the vapor film to re-wet the wall surface, and the boiling mechanism is transformed from film boiling to nucleate boiling, the boiling heat transfer perfomance is greatly improved. But the transition of the boiling mechanism is closely related to the initial velocity of the droplet, the size of the droplet, and the wall temperature. At the same time, after the droplets hit the wall surface, dynamic wetting behaviors such as deposition, vibration, rebound, or splashing will occur. Unfortunatly, the mechanism of droplet wetting behavior on boiling heat transfer is not clear, so it is necessary to carry out a fundamental research. In this study, the droplet size, initial droplet velocity, substrate’s temperature and surface tilt angle were precisely controlled. The images were captured by a high-speed camera to obtain a dynamic wetting image of the droplets impacting the wall from room temperature to 400°C. Finally, based on the image analysis method, a simple analysis of the three-phase contact line movement and the droplet dynamic wetting behavoir is performed.","PeriodicalId":325659,"journal":{"name":"Volume 7B: Thermal-Hydraulics and Safety Analysis","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129326193","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Large-scale separate heat pipe is widely used in various applications, such as waste heat recovery, passive cooling of Spent Fuel Pool (SFP) and so on. The evaporator and condenser of the heat pipe can be installed in different places with long distance. Working fluid circulates in the heat pipe due to static pressure difference between the evaporator and condenser. The separate heat pipe is a high efficiency heat transfer device which can transport heat for a long distance without considerable losses. A numerical model of separate heat pipe is established and verified according to the experimental data. The model agrees reasonably well with experimental data. The Mean Absolute Error (MAE) is 7.22%. According to the model, vapor quality at the evaporator exit in the separate heat pipe is analyzed. It is found that, vapor quality varies with heat pipe filling ratio and thermal loads. At low filling ratios, fluid at evaporator exit is overheated. While at high ones, it is in two-phase state. Vapor quality at evaporator exit decreases with the filling ratio. When the vapor quality is bit lower than 1, separate heat pipe comes to its maximum heat transfer capacity. It is also found that there is a minimum condenser height to activate the large-scale separate heat pipe. When the downcomer is full of liquid, elevating the condenser can increase the heat pipe performance. But when the condenser is high enough, the downcomer will be partially liquid filled, elevation of condenser provides little benefit.
{"title":"Modeling and Analysis of Two-Phase Distribution in Large-Scale Separate Heat Pipe","authors":"Yiwu Kuang, X. Jin, Rui Zhuan, Fang Xie, Kaidi Chen, Fei Han, Xiting Chen, Wen Wang","doi":"10.1115/icone29-93438","DOIUrl":"https://doi.org/10.1115/icone29-93438","url":null,"abstract":"\u0000 Large-scale separate heat pipe is widely used in various applications, such as waste heat recovery, passive cooling of Spent Fuel Pool (SFP) and so on. The evaporator and condenser of the heat pipe can be installed in different places with long distance. Working fluid circulates in the heat pipe due to static pressure difference between the evaporator and condenser. The separate heat pipe is a high efficiency heat transfer device which can transport heat for a long distance without considerable losses. A numerical model of separate heat pipe is established and verified according to the experimental data. The model agrees reasonably well with experimental data. The Mean Absolute Error (MAE) is 7.22%. According to the model, vapor quality at the evaporator exit in the separate heat pipe is analyzed. It is found that, vapor quality varies with heat pipe filling ratio and thermal loads. At low filling ratios, fluid at evaporator exit is overheated. While at high ones, it is in two-phase state. Vapor quality at evaporator exit decreases with the filling ratio. When the vapor quality is bit lower than 1, separate heat pipe comes to its maximum heat transfer capacity. It is also found that there is a minimum condenser height to activate the large-scale separate heat pipe. When the downcomer is full of liquid, elevating the condenser can increase the heat pipe performance. But when the condenser is high enough, the downcomer will be partially liquid filled, elevation of condenser provides little benefit.","PeriodicalId":325659,"journal":{"name":"Volume 7B: Thermal-Hydraulics and Safety Analysis","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115786769","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ruiqi Kang, Z. Xiong, Zhuguo Li, Shuo Ouyang, J. Liu
The separation performance of swirl-vane separators, including pressure drop and separation efficiency, is closely related to the two-phase flow pattern and the liquid film breakup behavior. In the swirling-swirl-vane separators, the droplets collision and film breakup happen. Influenced by the spiral blade structure and the central hub, the swirl-vane outlet region is prone to the formation of churn flow. Due to the complex and variant thickness of the liquid film in churn flow, it is extremely difficult to visually observe the generation and development process of the droplet entrainment from the side or the top under normal working conditions. Data on the phenomenon of droplet entrainment under the rotating flow field are rare, resulting in the entrainment mechanism of droplets under the rotating flow field is unclear. In this paper, investigations on the entrainment of droplets downstream of the swirl-vane has been carried out for a small liquid flow rate. A rotary flow field visualization experimental device has been developed. The churn flow is formed under the condition of near-zero liquid flow. The motion characteristics of the droplets in the churn flow are extracted by observing the movement of a small number of droplets in a rotating flow field. The rotational churn flow and droplet entrainment process are obtained through visual photography. The liquid film ligament and bag breakup characteristics under the rotating flow field are obtained, as well as the particle size characteristics of the entrainment droplets.
{"title":"Experimental Study on Droplets Entrainment and Film Breakup Characteristics Under in Rotating Churn Flow","authors":"Ruiqi Kang, Z. Xiong, Zhuguo Li, Shuo Ouyang, J. Liu","doi":"10.1115/icone29-92960","DOIUrl":"https://doi.org/10.1115/icone29-92960","url":null,"abstract":"\u0000 The separation performance of swirl-vane separators, including pressure drop and separation efficiency, is closely related to the two-phase flow pattern and the liquid film breakup behavior. In the swirling-swirl-vane separators, the droplets collision and film breakup happen. Influenced by the spiral blade structure and the central hub, the swirl-vane outlet region is prone to the formation of churn flow. Due to the complex and variant thickness of the liquid film in churn flow, it is extremely difficult to visually observe the generation and development process of the droplet entrainment from the side or the top under normal working conditions. Data on the phenomenon of droplet entrainment under the rotating flow field are rare, resulting in the entrainment mechanism of droplets under the rotating flow field is unclear. In this paper, investigations on the entrainment of droplets downstream of the swirl-vane has been carried out for a small liquid flow rate. A rotary flow field visualization experimental device has been developed. The churn flow is formed under the condition of near-zero liquid flow. The motion characteristics of the droplets in the churn flow are extracted by observing the movement of a small number of droplets in a rotating flow field. The rotational churn flow and droplet entrainment process are obtained through visual photography. The liquid film ligament and bag breakup characteristics under the rotating flow field are obtained, as well as the particle size characteristics of the entrainment droplets.","PeriodicalId":325659,"journal":{"name":"Volume 7B: Thermal-Hydraulics and Safety Analysis","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122211178","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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