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Capillary Limit of a Sodium Screen-Wick Heat Pipe

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SSRN 2022年

作者： Ma, Yugao Wang, Xueqing Yu, Hongxing Huang, Shanfang Zhang, Yingnan Huang, Jian Su, Guanghui Deng, Jian Chai, Xiaoming Hu, Wenzhen School of Nuclear Science and Technology Xi’an Jiaotong University Shanxi Xi’an710049 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610213 China Department of Engineering Physics Tsinghua University Beijing100084 China State Key Laboratory of Multiphase Flow in Power Engineering China

High-temperature alkali-metal heat pipes are passive heat transfer devices, where the capillary pressure created by the menisci in the wick pumps the condensed fluid back to the evaporator. Thus, the heat pipe heat transfer capacity is limited by the maximum capillary pressure at high heat fluxes. This work presents a two-dimensional heat and mass transfer model that includes the capillary and gravitational forces that are used to predict the capillary limit which is then validated by experimental data. The predicted critical heat flux temperature has an error of less than 20℃ and a relative error of 6%. The predicted transient sequences are consistent with the measurements. The model shows that capillary limit is affected by inclination angle, heat flux, and wick structure. For inclinations, the critical heat flux at the capillary limit is linearly related to the inclination angle with the predicted temperature rising 2 ~10℃/s during the early stage of the capillary limit critical heat flux condition. The evaporator temperature oscillates before the capillary limit with positive inclinations. For heat fluxes, increasing the heat flux by 17% increases the temperature increase rate 10 fold with a longer dryout length. The evaporator exhibits hysteresis after the capillary limit due to partial dryout of evaporator. For wick structures, reducing the mesh screen pitch from 80 μm to 15 μm reduces the critical heat flux to 10% of the CHF at 80 μm. This model can accurately predict the heat pipe temperature variations at the capillary limit and can explain the physical mechanisms for the dryout oscillations and recovery hysteresis at the capillary limit. Thus, the measurements and model provide analytical guidelines for designing heat pipe cooling systems. © 2022, The Authors. All rights reserved.

关键词： Heat flux

Influence of Salts on Morphology of Structures in Surfactant-Polymer Solutions Explored by Coarse Grained Dynamic Simulation

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Influence of Salts on Morphology of Structures in Surfactant...

作者： Liu, Dongjie Liu, Fei Zhou, Wenjing Chen, Fei Wei, Jinjia State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China School of Chemical Engineering and Technology Xi’an Jiaotong University Xi’an710049 China

In this study, a coarse-grained molecular dynamic simulation was employed to test the influence of salts in morphology of structures in surfactant-polymer solutions. The surfactant was cetyltrimethyl ammonium chloride (CTAC) and the polymer was polyacrylamide (PAM). Six different salt concentrations were studied in the mixed surfactant-polymer solutions, and pure surfactant solutions with salts were also tested as control groups. By analyzing the shapes of micelles and the CTA+ aggregation number of micelles, we noted that the proper salt concentration can facilitate the formation of large micelles. In too high or too low salt concentration solutions only spherical or short rodlike micelles exist. The existence of PAM can also facilitate the formation of large micelles because polymers act as "bridges" and increase the probability of touch and coalescence of micelles. © Springer Nature Switzerland AG 2020.

关键词： Morphology

Ethylene Oxidation with Ce-Modified Fe-Based Oxygen Carrier: Fuel Combustion Efficiency Improvement

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SSRN 2022年

作者： Sun, Tianli Wu, Ye Mei, Jian Han, Yinghui Cai, Tianyi Liu, Dong MIIT Key Laboratory of Thermal Control of Electronic Equipment School of Energy and Power Engineering Nanjing University of Science and Technology Nanjing210094 China Advanced Combustion Laboratory School of Energy and Power Engineering Nanjing University of Science and Technology Nanjing210094 China College of Resources and Environment University of Chinese Academy of Sciences Beijing100049 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

Improving combustion efficiency of diesel engine is very important in the current background of carbon neutralization because sufficient combustion means low pollutant emission and little energy waste. In past studies, catalytic coatings were used in diesel engine to speed up fuel-burning rates and reduce emissions caused by insufficient combustion. Insufficient combustion mainly in high temperature and low oxygen area, using oxygen carrier as the coating material for the combustor surface to support additional –O and regulate the combustion process also is a promising strategy. A desired Fe-based oxygen carrier with excellent redox capability and stability was fabricated to convert fuel pyrolysis products into CO2, H2O and extra heat to improve the fuel combustion efficiency. A range of cerium modified Fe2O3 oxygen carriers were prepared and tested with ethylene as a representative fuel to investigate the redox capability and stability during fuel pyrolysis process. In addition, the gas-solid surface reaction of ethylene and iron oxide was studied by density functional theory (DFT) to illustrate their good reactivity and the mechanism of doping optimization. It was found that when using the FeCe-2 oxygen carrier with the mole ration of Fe and Ce is 9:1 during ethylene pyrolysis process, the ethylene was oxidized most sufficiently (CO2 yield>92%). DFT simulation showed that Ce doping improved the reactivity of surface oxygen. Experimental data and characterization analysis showed that the addition of Ce improved oxygen vacancy capacity to enhance the oxidation for the pyrolysis products. Due to the role of both, the ethylene and its pyrolysis products were converted into CO2 and H2O quickly and effectively. The obtained results indicate that FeCe-2 is the potential oxygen carrier coating material for combustion efficiency improvement. © 2022, The Authors. All rights reserved.

关键词： Carbon dioxide

Numerical Investigations for the Pcm and Liquid Immersion Cooling Effects on Lithium Ion Battery Thermal Runaway Mitigation

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SSRN 2023年

作者： Liu, Xinyu Zhou, Zhifu Wu, Wei-Tao Wei, Lei Wu, Weixiong Li, Yang Gao, Linsong Li, Yubai Song, Yongchen Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education Dalian University of Technology Dalian116024 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi’an710049 China School of Mechanical Engineering Nanjing University of Science and Technology Nanjing210094 China Department of Mechanical and Energy Engineering Southern University of Science and Technology Shenzhen518055 China Energy and Electricity Research Center Jinan University Zhuhai519070 China

In this study, a three-dimensional (3D) thermal runaway (TR) model with conjugate heat transfer submodel is adopted. TR behaviors for a battery pack with 12 prismatic LIBs are then simulated. Three thermal safety measures of TR protection from internal shorting in Cell 1 to pack level configuration are compared and evaluated. Paraffin phase change material (PPCM) is firstly proposed to delay the TR propagation between LIBs with solid-liquid phase change as heat transfer mechanism. Different thicknesses of PPCMs are compared to verify the TR mitigation performance of the PPCM under thermal abuse condition. The TR time for the Cell 2 is delayed to be 64 s, 266 s and 414 corresponding to PPCM thickness of 1.8 mm, 3.6 mm and 5.4 mm. As the simulation results shows, this TR time can be further delayed to 798 s by a strategy with combing PPCM with insulation. In addition, this work proposes a novel thermal safety protection based on immersion cooling with pool boiling of fluorinated liquid as heat transfer mechanism. We observe that the average temperature of Cell 2 - Cell 12 tends to be within 34oC under immersive cooling condition, which indicates the possibility to prevent the TR. © 2023, The Authors. All rights reserved.

关键词： Lithium-ion batteries

Cascade co-optimization of the load ramp-down capability considering the transient stored energy of subcritical CFB power units

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Energy 2025年 332卷

作者： Chenyu Zhao Chaoyang Wang Ming Liu Jiping Liu Junjie Yan MOE Key Laboratory of Thermal Fluid Science Engineering Xi'an Jiaotong University Xi'an 710049 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Coal-fired power plants (CFPPs) play a crucial role in ensuring a stablepower supply and maintaining stability within China's evolving electricity system. As one type of CFPP, subcritical circulating fluidized bed (CFB) power units face challenges in improving their operational flexibility. However, constraints on load regulation in subcritical CFB boilers due to inertia. By studying the transient status of internally stored energy, this paper finds that the compensation phenomenon of drum-stored energy, the insufficient difference between the thermal and chemical energy density of bed materials, and the slow variation of stored energy on the furnace side all restrict load ramp-down. Based on this evidence, this study adopts transient stored energy as a feedforward input, in addition to the passive control of water, air, and slag, to achieve active regulation of the stored energy status. Considering the adverse effect of rapid slag discharge on boiler thermal efficiency, priority is given to the active control of water and air, thereby improving the ultimate load ramp-down rate to 3 % Pe/min. With the further addition of active slag discharge control, the load ramp-down rate reaches 5 % Pe/min, although the unit's energy efficiency is reduced by approximately 0.8 %.

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Supercritical Water Gasification of Phenol with Metal Cations-A Way to Degrade Coal Industrial Wastewater and Metal-Contaminated Wastewater Simultaneously

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SSRN 2022年

作者： Cao, Wen Wang, Shaoqi Ma, Lujing Liu, Shi Jin, Hui Wei, Wenwen Guo, Liejin State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xianning West Road Xi’an710049 China Suzhou Academy of Xi’an Jiaotong University No.99 Ren’ai Road Jiangsu Suzhou215123 China

Phenol is a representative compound in coal industrial wastewater. Metal cations are the main harmful components in the wastewater of the electroplating and dyeing industries. Supercritical water gasification (SCWG) of phenol with metal cations could provide a promising way to degrade coal chemical wastewater and metal-containing wastewater simultaneously. In this study, SCWG of phenol with Mg2+, Mn2+, and Ni2+ was carried out to investigate the effect of metal cations on gasification results. Results showed that gaseous product was mainly composed of H2, CO, CH4 and CO2, and CO2 was the dominant one. Prolonging residence time and increasing the concentration of metal cations significantly increased the gas yield of CO2 and carbon gasification efficiency. Higher concentrations of metal cations facilitated methane-reforming reaction and water-gas shift reaction. Metal cations promoted the generation of 1-Ethoxybutane by the ring-breaking reaction and prevented the polymerization reaction. The order of catalytic effect was ranked as Ni2+>Mn2+>Mg2+. Mg2+, Mn2+ and Ni2+ were finally transformed into the corresponding metal hydroxides and metal oxides which could be recycled for reutilization. NiO could be reduced into metallic Ni, which consumed the H2 but effectively catalyzed SCWG of phenol. © 2022, The Authors. All rights reserved.

关键词： Phenols

Evaluation of stability and catalytic activity of Ni catalysts for hydrogen production by biomass gasification in supercritical water

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Carbon Resources Conversion 2019年第1期2卷 95-101页

作者： Youjun Lu Hui Jin Rui Zhang State Key Laboratory of Multiphase Flow in Power Engineering(SKLMFPE) Xi’an Jiaotong UniversityXi’an 710049ShaanxiChina

Supercritical water gasification is a promising technology for wet biomass *** this paper,Ni and other metal catalysts were synthesized by wet *** stability and catalytic activities of Ni catalysts were ***,catalytic activities of Ni,Fe,Cu catalysts supported on MgO were tested using wheat straw as raw material in a batch reactor at 723 K and water density of 0.07 cm^(3)/*** results showed that the order of metal catalyst activity for hydrogen generation was Ni/MgO>Fe/MgO>Cu/***,the influence of different supports on Ni catalysts performance was *** results showed that the order of the Ni catalysts’activity with different supports was Ni/MgO>Ni/ZnO>Ni/Al_(2)O_(3)>Ni/ZrO_(2).Finally,the effects of Ni loading and the amount of Ni catalyst addition on hydrogen production,and the stability of Ni/MgO catalyst were *** was found that serious deactivation of Ni catalyst in the process of supercritical water gasification took *** if carbon deposited on the catalyst surface was removed by high temperature calcination and the catalyst was reduced with hydrogen,the activity of used catalyst was only partially restored.

关键词： Ni catalyst Deactivation Biomass gasification Supercritical water Hydrogen production

Neural network-based interface reconstruction algorithm for two-phase fluid flow

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Fundamental Research 2025年

作者： Gong, Junhua Chen, Yujie Yu, Bo Sun, Dongliang Wang, Bohong Shi, Guoyun Chen, Bin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China School of Mechanical Engineering Beijing Institute of Petrochemical Technology Beijing 102617 China School of Petroleum Engineering Yangtze University Wuhan 430100 China National & Local Joint Engineering Research Center of Harbor Oil & Gas Storage and Transportation Technology/Zhejiang Key Laboratory of Pollution Control for Port-Petrochemical Industry Zhejiang Ocean University Zhoushan 316022 China Kunlun Digital Intelligence Technology Company Beijing 102266 China

In two-phase fluid flow, the vapor-liquid interface tends to behave as a curved shape under the influence of surface tension. Curve reconstruction favors improving the resolution of bubbles or droplets in numerical studies. Based on artificial neural network (ANN) and convolutional neural network (CNN), two curve reconstruction algorithms, namely CIR-ANN and CIR-CNN, are proposed in this study. Both algorithms can achieve high-precision prediction of the center and radius when reconstructing interfaces using a portion of a standard circle, especially for the CIR-CNN algorithm. A strict mass conservation strategy is also proposed to ensure the reliability of the neural network predictions. In comparison with interface reconstruction algorithms such as piecewise linear interface construction (PLIC) algorithm, efficient least squares volume-of-fluid interface reconstruction algorithm (ELVIRA), quadratic spline based interface (QUASI) reconstruction algorithm after the first interface correction, Circle-based Interface Reconstruction (CIR), and CIR-ANN algorithm, the proposed CIR-CNN demonstrates good advantages in static interface reconstruction, with average accuracy ratios of 48.40, 86.69, 26.34, 4.07 and 2.26. However, when capturing the bubble under a complex rotation and shear recovery flow field, the advantage of the proposed algorithms decreases due to the increased complexity of the fluid volume fraction distributions. Regarding the computational time cost of reconstructing random circular interfaces, the proposed algorithms achieve average reduction ratios of 4.16, 7.86, and 34.14, respectively, compared to the CIR, ELVIRA, and QUASI algorithms. © 2025

关键词： ANN CNN Curve reconstruction Neural network Two-phase flow

Analysis of Frequent Tube Burst of High Temperature Reheater in 600 MW Unit

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Analysis of Frequent Tube Burst of High Temperature Reheater...

2020 IEEE Sustainable power and Energy Conference, iSPEC 2020

作者： Sun, Ke Wang, Jiaan Yan, Yu Jiang, Jiahao Deng, Lei Che, Defu China Huadian Electric Power Research Institute Co. Ltd. Hangzhou310030 China State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'An Jiaotong University Xi'an710049 China

ISBN: (纸本)9781728191645

The reasons of frequent tube burst of the high temperature reheater in a supercritical 600 MW unit were systematically investigated via the examination of macroscopic inspection, chemical composition, mechanical properties, microstructures, scanning electron microscope and energy disperse spectroscopy detection. It is demonstrated that the tube burst of the high temperature reheater results from not only design factors, but also manufacture quality. Due to the absence of solid solution treatment in spare elbow, the inner dislocations and residual stress increase obviously, which accelerates the precipitation of carbide containing Cr and the formation of Cr depleted zone on grain boundary(GB) subsequently, leading to the decrease of GB corrosion resistance and the final leakage of high temperature reheater tube induced by intergranular corrosion. © 2020 IEEE.

关键词： Carbides