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Transient gas/liquid two-phase flow in a pipeline-riser system after the change of inlet flow rates

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multiphase Science and Technology 2020年第2期32卷 25-46页

作者： Zou, Suifeng Liu, Weizhi Xu, Qiang Xie, Xiangdong Guo, Liejin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China Wuhan Second Ship Design and Research Institute Wuhan China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

Transient gas/liquid two-phase flow caused by the change of inlet gas and/or liquid flow rates was experimentally studied in a 380-meter-long pipeline-riser system with a vertical riser of 21.5 meters in height. Results showed that, for the transient processes with the same median flow rates, the rise of flow rates was likely to result in shorter duration time compared to the fall of flow rates. Apart from the manner of change, the duration time was also closely related to the flow mechanism, which varied with the global flow regime. As a consequence, the transient process lasted a longer time around the transition boundary of stable regime and the severe slugging regime;whereas, the transient process would be shorter if the regime was an irregular oscillation;and the longest transient process was found at very low gas and liquid flow rates. As for the prediction of duration time of both the entire transient process and the transition to undesirable flow regimes, the support vector machine turned out to be much more suitable than the log-linear regression. In addition, some similarities of pressure drop signals were found between the transition to unstable and irregular flow regimes and the steady state of these regimes. Since the method for fast recognition of a steady global flow regime has already been developed, it becomes possible to forecast the transition to these undesirable flow regimes through the modification of the recognition method. © 2020 Begell House Inc.. All rights reserved.

关键词： flow rate

Thermodynamic Performance of Cacl2 Absorption Heat Pump Thermal Energy Storage System with Triple Storage Tanks

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SSRN 2023年

作者： Chen, Jinsen Zhou, Yuan Liu, Jiping Zhao, Yongliang Zhang, Shunqi Yan, Junjie MOE Key Laboratory of Thermal Fluid Science Engineering Xi'an Jiaotong University Xi’an710049 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi’an710049 China

Absorption thermal energy storage has the characteristics of high thermal energy storage density (ESD) and low heat loss for long-term storage. To solve the coal-fired combined heat and power plant heat-power-coupling problem, in this work, an absorption heat pump thermal energy storage system (AHPTES) using CaCl2-water solution as the working fluid is proposed. A steady-state thermodynamic model of the system was constructed using Aspen Plus. Under the design conditions, the AHPTES system requires a tank volume of 464.61 m3 for one hour of operation, an ESD of 29.81 kW·h/m3, a thermal energy storage ratio of 46.50%, and a heating ratio of 53.54%. Compared to the dual-tank thermal energy storage system with H2O and CaCl2-water solutions as working fluids, the AHPTES system has 1.43 and 1.25 times higher ESD and 0.7 and 0.8 times lower tank volume, respectively. Then, the effects of CaCl2 mass fraction, driving pressure, evaporator outlet temperature, preheating temperature, and condensing temperature on the system performance are simulated. Improving the CaCl2 mass fraction, lowering the evaporator outlet temperature, and raising the condensing temperature and preheating temperature can boost the system's performance. At the optimal system performance, the required tank volume for one hour of system operation is 439.56m3, ESD can reach up to 37.39 kW·h/m3, heating ratio to 44.83%, and the energy storage ratio to 55.17%. Besides, raising the mass fraction of CaCl2 to 52% and decreasing the evaporator outlet temperature to 30 °C at 50% mass fraction resulted in crystallization of the system. © 2023, The Authors. All rights reserved.

关键词： Thermal energy

Large eddy simulation on the wake characteristics of linearly stratified flow past a sphere

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Scientific Reports 2025年第1期15卷 1-13页

作者： Xia, Tianci Wei, Na Shi, Liuliu School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai 200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai 200093 China Key Laboratory of Power Machinery and Engineering of Ministry of Education Shanghai Jiao Tong University Shanghai 200240 China

In this study, Large Eddy Simulation (LES) has been employed to examine the influence of the Froude number (Fr) on the linearly stratified wake and internal waves behind a sphere at a subcritical Reynolds number of Re = 3700. Six distinct sets of models with varying Fr (Fr = 0.05, 0.25, 0.5, 1, 2, ∞) have been chosen to establish density linear stratification through the use of a User Defined Function (UDF). The analysis focuses on the impact of stratification on wake characteristics, velocity distribution, and the structure of internal waves within stratified flow. It is evident that density stratification plays a pivotal role in shaping wake structure. Notably, in stratified flows, wakes exhibit unique characteristics including the generation of internal waves, suppression of vertical velocity, and the emergence of oscillating wake patterns. The study reveals that a decrease in the Froude number leads to heightened vertical suppression of the wake and increased anisotropy of the velocity distribution. Furthermore, as the Froude number ascends from 0.05 to 2, the wake undergoes a transition from quasi-two-dimensional vortex shedding to three-dimensional turbulence. © The Author(s) 2025.

关键词： Froude number Internal wave Linearly stratified flow Wake

Study on the Safety Characteristics of Fluoride-Salt-Cooled High-Temperature Advanced Reactor

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SSRN 2023年

作者： Lv, Xindi Zhang, Dalin Li, Xinyu Zhou, Xingguang Jiang, Dianqiang Su, Guanghui Tian, Wenxi Qiu, Suizheng State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China

FuSTAR is a small, modular fluoride-salt-cooled high-temperature advanced reactor, proposed by Xi'an Jiaotong University (XJTU), aiming at fulfilling the requirements of Gen IV nuclear system and meanwhile ensuring the inherent safety and economics. In order to evaluate the safety performance of FuSTAR, five typical design basis accidents are selected for safety analysis with different initial events. The sensitivity analysis is also performed. The results of transient accidents indicate that safety of FuSTAR has been guaranteed in URIA and ULOF. Meanwhile, the maximum limit of external parameters causing ULOHS and UOC are obtained by sensitivity analysis. In the ULOF and ULOHS, the peak of fuel temperature, cladding surface temperature and core outlet temperature of coolant are below their safety limits. Therefore, FuSTAR exhibits acceptable safety under design basis accidents. This study will provide supports in verifying the rationality of the design and the subsequent optimization of FuSTAR. © 2023, The Authors. All rights reserved.

关键词： Sensitivity analysis

Transient Thermoelectric Characteristics of the Principle Prototype for the Heat Pipe Cooled Nuclear Silent Themoelectirc Reactor (Nuster)

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SSRN 2023年

作者： Guo, Kailun Zhang, Yin Lin, Xingyang Huang, Jinlu Wang, Chenglong Qiu, Suizheng Tian, Wenxi Su, Guanghui School of Nuclear Science and Technology Shaanxi Key Laboratory of Advanced Nuclear Energy And Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

This paper proposes an optimized design for the Heat Pipe ThermoElectric Generator(HPTEG) principle prototype. The refined scheme adopts high-temperature sodium heat pipes as heat transfer elements to enhance the overall operating temperature of the device. It adopts Half-Hessler(HH) alloy ThermoElectric Generator(TEG) arranged on the upper and lower sides of the heat exchanger to enhance the thermoelectric conversion efficiency of the device. A heat pipe dynamic conduction model is established to simulate the start-up process of the sodium heat pipe. A TEG model is developed, which is able to simulate the three-dimensional thermoelectric properties of the TEG. The numerical simulation platform is used to analyze the steady-state and transient thermoelectric properties of the refined HPTEG prototype. This study provides data support for the subsequent design modification of the future HPTEG principle prototype and provides ideas for the 3D transient calculations of the solid-state heat pipe reactors. © 2023, The Authors. All rights reserved.

关键词： Heat pipes

Electromagnetic Effects and Accurate Wall-Temperature Measurement Method Under Directly Electric Heating Mode

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SSRN 2022年

作者： Lei, Xianliang Liu, Yunfan Liu, Shuhan Li, Debiao Gou, Lingtong Li, Yusheng State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

By directly imposed electrical energy on metal materials with low voltage but high current to generate Joule heat is an effective energy conversion method. The corresponding temperature will quickly reach the predetermined value. It is also an effective way to achieve homogeneous heating or local non-uniform heating in the heterogeneous conductive elements, thus directly electric heating is widely used in scientific experiments and industrial practices. However, different direct Electrical heating method (i.e., Direct-Current or Alternating Current heating) will lead to different power losses and the interference on the sensor, results in inconsistent temperature distribution or inaccurate temperature, even under the condition with power frequency (f= 50 Hz or 60 Hz). In the present paper, the skin effect and eddy current in different metal materials with variable frequency and different section-shapes have been analyzed by electromagnetic coupling simulation. Meanwhile, two comparative experimental investigations on temperature measurement methods with DC and AC heating have been implemented. It is found that the measured temperature by AC heating is always lower than that of DC heating effected by skin effect and mutual inductance effect, the skin depth in four common used materials is: Iron © 2022, The Authors. All rights reserved.

关键词： Temperature measurement

Sensitively Detection of Ascorbic Acid in Orange Samples with Ionic Liquid Functionalized Carbon Dots and Lanthanide Complexes

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SSRN 2024年

作者： Li, Ying Xia, Ji-Ji Lu, Jia-Zhen Wang, Zi-Long Wang, Mi-Tang School of Materials and Chemistry University of Shanghai for Science and Technology Shanghai200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China

In the food industry, ascorbic acid (AA) is widely used as an antioxidant. However, the concentration of AA is influenced by various factors, including temperature, time, and pH value during food preparation and storage, leading to its instability in content. This makes the accurate detection of AA content particularly important. Precise determination of AA content in food and pharmaceuticals is crucial for ensuring the adequate intake of essential vitamins and maintaining good health. Herein, we have developed a successful preparation method of an imidazole-based ionic liquid functionalized CDs hybrids APM-CDs. A novel photo functional hybrid probe Eu3+@APM-CDs was obtained via an ion-exchange reaction between APM-CDs and lanthanide complex Eu(DPA)3. The obtained hybrid probe was extensively characterized in detail. What’s more, the results show that the FL intensity of Eu3+@APM-CDs has a good linear response to AA concentrations in the range of 0-500 μM (R2 = 0.99), with a detection limit of 80 nM. The fluorescence probe demonstrates good selectivity and sensitivity toward AA and has the potential for significant application in AA detection by simplifying procedures and reducing interference from impurities. © 2024, The Authors. All rights reserved.

关键词： Probes

Thermal-Hydraulic Characteristics of Helical Cruciform Single Rod Based on Cfd Investigation

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SSRN 2023年

作者： Chen, Yiwen Zhang, Dalin Jiang, Dianqiang Wang, Xinan Tian, Wenxi Qiu, Suizheng Su, Guanghui State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China

The helical cruciform fuel (HCF) takes advantages of strong mixing effects, self-supporting features, and strengthened heat transfer, potential to increase the fuel performance in nuclear reactors. In this work, hydraulic resistance and heat transfer characteristics of an HCF single rod cooled by water were studied based on CFD simulation. Various turbulent models were compared based on experimental data. The velocity field, transverse velocity, wall temperature, and fluid temperature distribution were obtained to discuss influences of geometric sizes on the fuel performance. After 3/8 of the pitch, flow was fully developed. The friction factor and surface heat transfer coefficient were higher with a shorter twist pitch owing to stronger mixing effect while they kept unchanged with variable cross-section sizes but a fixed equivalent diameter. Correlations of friction factor and surface heat transfer coefficient were proposed considering geometric modified coefficients based on a geometric dimensionless number, which were validated with new geometric cases. © 2023, The Authors. All rights reserved.

关键词： Heat transfer coefficients

Depth from Defocus Technique for High Number Densities and Non-Spherical Particles

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SSRN 2024年

作者： Xu, Rixin Huang, Zuojie Gong, Wenchao Zhou, Wu Tropea, Cameron School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer for Power Engineering Shanghai China Institute for Fluid Mechanics and Aerodynamics Technical University of Darmstadt Darmstadt Germany

The Depth from Defocus (DFD) imaging technique for measuring the size and number concentration of particles in a dispersed two-phase flow has up to now been restricted to relatively sparse particle densities and to identifying only spherical particles. The present study examines two advancements to the technique, widening its range of application significantly. The first advancement introduces an image processing procedure which can identify and size particle images which are overlapping. This increases the tolerable number concentration of particles which can be identified and processed within the measurement volume. The second advancement explores the possibility of determining the size and position of non-spherical particles within an observation volume. These enhancements are experimentally validated using a dedicated apparatus in which particles of known size, shape and degree of overlapping images can be systematically varied. This experimental setup provides benchmark data to quantify the accuracy and limitations of the processing algorithms. © 2024, The Authors. All rights reserved.

关键词： Two phase flow