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SSRN 2024年

作者： Yang, Yunjie Bai, Minli Zhou, Zhifu Wu, Wei-Tao Wei, Lei Lv, Jizu Hu, Chengzhi Li, Yang 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 School of Mechanical Engineering Guangdong Ocean University Zhanjiang524088 China

While reducing the size and Pt loading can achieve a lower proton exchange membrane fuel cell (PEMFC) stack cost, it is also very important to focus on the performance changes of the PEMFC stack during the long-term operation. A 3D PtCo catalysts long-term performance model is established in this study, and PEMFC stacks with one cooling unit per cell (1-cell stack) and three cells (3-cell stack) are employed as the computational domains, respectively. The effective area of each cell is 50 cm2, and the changes in current density as well as effective catalytic area of PEMFC stacks with two cooling strategies before and after long-term operation under different humidity conditions are investigated at low Pt loadings. The results show that there are large differences in the output voltage and current density distributions between the three cells due to the poor membrane hydration affected by the non-uniform temperature distribution, although the 3-cell stack can significantly reduce the size. Localized catalyst degradation in both 3-cell and 1-cell stacks is closely related to the geometry of the cathodic flow field, and non-uniform catalyst degradation is found to increase the activation and mass transfer losses and change the distribution of current density within the membrane. In addition, the 3-cell stack is found to perform even better in terms of durability, especially under high humidity conditions, which provides a potential solution to improve the durability of PEMFC stacks operating in harsh conditions. © 2024, The Authors. All rights reserved.

关键词： Durability

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Synthesis of Fe3o4@Sio2@C/Ni Microspheres for Enhanced Electromagnetic Wave Absorption

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SSRN 2023年

作者： Zhang, Jingyun Jia, Zhen Lv, Fanglin Hou, Yunxi Liu, Jianfeng Yu, Shitao Jiang, Long Liu, Yue Liu, Shiwei Li, Lu Key Laboratory of Multiphase Flow Reaction and Separation Engineering of Shandong Province State Key Laboratory Base of Eco-chemical Engineering College of Chemical Engineering Qingdao University of Science and Technology Qingdao266042 China AVIC Research Institute for Special Structures of Aeronautical Composites 19 Jiqi Road Jinan250000 China Qingdao University of Science and Technology China

With the rapid development of electromagnetic technology and radar, military stealth technology was an important indicator to measure the country's military, and wave-absorbing materials had emerged. In this paper, the absorbing material with a bilayer core-shell structure of Fe3O4@SiO2@C/Ni was prepared and characterized for its structure, composition electromagnetic, etc. The analysis showed that the double-layer core-shell structure was clearly visible and had excellent electromagnetic properties. By varying the thickness of carbon layer and SiO2 layer, the absorption performance of the prepared samples could be adjusted to achieve the best impedance matching. The sample had a minimum reflection loss of-38.5 dB and a maximum effective bandwidth of 7 GHz when its thickness was 4.5 mm, making it a promising choice for absorbing material applications. © 2023, The Authors. All rights reserved.

关键词： Magnetite

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Novel Solid-state Hydrolysis Kinetics of Nabh4 for Stable and High-Capacity On-Line Hydrogen Production

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SSRN 2024年

作者： Chen, Jiawei Wu, Zhen Zheng, Jie Shi, Yu Xie, Lei Yang, Fusheng Wang, Yuqi Zhang, Zaoxiao School of Chemical Engineering Northwest University Xi’an710069 China School of Chemical Engineering and Technology Xi’an Jiaotong University Xi’an710049 China College of Chemistry and Molecular Engineering Peking University Beijing100871 China Sunan Institute for Molecular Engineering Peking University Jiangsu 215500 China State Key Laboratory of Multiphase Flow for Power Engineering Xi’an Jiaotong University Xi’an710049 China

Solid-state hydrolysis of NaBH4 could achieve high-capacity on-line hydrogen production. However, the stability of hydrogen production in the solid-state hydrolysis process has been questioned. In this paper, a novel kinetics is proposed for the solid-state hydrolysis behavior. The acceleration factor β is introduced into the traditional shrinking core model to reveal the relationship between "dissolution" and "catalytic hydrolysis" in the solid-state hydrolysis process. The comparison results show a good agreement between the model and experiment in the temperature range of 303.15-348.15 K. Meanwhile, the kinetics conclusions and product characterization indicated that the "excessive dissolution" of NaBH4 and the "dehydration of by-products" are two important factors contributing to the uncontrolled reaction. Based on the parametric analysis and experimental verification, the optimum temperature for solid-state hydrolysis is approximately 323.15 K. Besides, the adjustment of the water intake strategy to intermittent intake reduced water consumption by 36.6%. As a result, the hydrogen release capacity could be increased to as high as 5.49 wt.% (close to the U.S. Department of Energy 2025 gravimetric hydrogen storage capacity of 5.5 wt.%), even though the weight of water is taken into account as reactant. © 2024, The Authors. All rights reserved.

关键词： Hydrolysis

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Xct Images-Based Pore-Scale Numerical Investigation for Heat Transfer Using Copper Foam Filled with Paraffin Phase Change Material

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SSRN 2024年

作者： Liu, Xinyu Zhou, Zhifu Wu, Wei-Tao Wei, Lei Hu, Chengzhi Lyu, Jizu Huang, Heng 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 School of Mechanical Engineering Guangdong Ocean University Zhanjiang524088 China

The principle of phase change heat transfer using copper foam in the paraffin phase change material (PPCM) are not well understood. In this study, based on X-ray computed tomography (XCT), three dimensional (3D) geometric model of copper foam was established, including PPCM domain. We developed a coupled fluid-solid model to explore phase change for heat transfer in the composite phase change material (CPCM) with copper foam and PPCM. The effects of phase change melting behavior, heat transfer characteristics and homogeneity of temperature were considered. Results of numerical simulation demonstrated that the CPCM had completely melted at 669.8 s. Here the melting time decreased by 45%, compared with the pure PPCM at 1218 s. The extensive heat transfer contact area was offered by the copper foam skeleton. Meanwhile, the melting durations of the CPCM ranged from 4368 s, 2236.3 s, 509.4 s, and 284.6 s corresponding to the heat fluxes with 500 W/m2, 1000 W/m2, 5000 W/m2, and 10000 W/m2. The melting process correlated directly with the heat flux, making it adaptable to the operational demands of diverse electronic components. © 2024, The Authors. All rights reserved.

关键词： Heat flux

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Modeling of water and temperature distribution in PEM fuel cell

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2010年第12期31卷 2051-2056页

作者： Ma, Li-Zhong Shen, Shuang-Lin Jia, Fei Liu, Hong-Tan Guo, Lie-Jin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Dept. of Mechanical and Aerospace Engineering University of Miami Coral Gables FL 33124 United States

A two-phase flow, non-isothermal, three dimensional model was developed to study the transport phenomena in proton exchange membrane (PEM) fuel cell. Modeling results of water distribution and temperature distribution are presented in this paper. The modeling results show that water and temperature distributions are non-uniform. Along the flow direction, water concentration in anode is decreasing while that in cathode is increasing which liquid water present in cathode;in the cross section perpendicular to the flow direction, both water concentration and liquid water saturation under the shoulder are higher than that under the channel;liquid water distribution across cathode GDL is different at different discharging voltages. Local temperature is decreasing along the flow direction, with even higher gradient when the reactant gas is insufficient;temperatures under the shoulder are lower than those under the channel;in the direction across MEA, the highest temperature is in cathode catalyst layer, and temperature gradient increases as the discharging voltage decreases;at the same discharging voltage, the thicker the PEM is, the lower the local temperatures and the temperature gradient across MEA are.

关键词： Temperature distribution

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Simulations on Hybrid Thermal Management of Mini-Channel Cold Plate and Pcm for Lithium-Ion Batteries Under Discharging and Thermal Runaway Conditions

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SSRN 2024年

作者： Liu, Yang Zhou, Zhifu Wu, Wei-Tao Wei, Lei Lyu, Jizu Li, Yang Liu, Xinyu Li, Yubai Song, Yongchen Key Laboratory of Ocean Energy Utilization and Energy Conservation 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 School of Mechanical Engineering Guangdong Ocean University Zhanjiang524088 China

In this study, we compared the performance of different structures of mini-channel cold plate (MCP)- phase change material (PCM) hybrid thermal management on discharge and thermal runaway. The heat transfer structures for them can be categorized into three types: (a) uncoupled, (b) semi-coupled, and (c) fully coupled. Among these, the semi-coupled design B exhibits the best performance. Specifically, in the high rate discharge condition, the structure can control the battery temperature at 44.37°C at low coolant mass flow rate, and the temperature at 36.47°C at high mass flow rate, while the temperature difference (TD) of a single cell does not exceed 2.01°C. In a low-multiplier discharge zero-energy system, the pack temperature rise can be limited to no more than 10°C in 35°C environment. Under external short-circuit conditions, a lower coolant mass flow rate is sufficient to keep the pack temperature at 43.22°C. Under internal short-circuit thermal runaway (TR), lower coolant mass flow rate can prolong the TR of the adjacent cell up to 521 s, and higher mass flow rate can completely inhibit the occurrence of TR. The objective of this study is to offer valuable references for the design and implementation of hybrid MCP-PCM cooling systems. © 2024, The Authors. All rights reserved.

关键词： Phase change materials

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Corrigendum to ‘Numerical simulation on sonic steam jet condensation in subcooled water through a double-hole nozzle’ [Int. J. Heat Mass Transfer 115 (2017) 143–147]

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International Journal of Heat and Mass Transfer 2017年 115卷 1360-1360页

作者： Lutao Wang Daotong Chong Lun Zhou Weixiong Chen Junjie Yan State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an 710049 PR China

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Regulation Mechanism Study of Intermediate Products During Supercritical Water Gasification

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SSRN 2024年

作者： Wang, Cui Feng, Huifang Jin, Hui School of Water and Environment Chang’an University Xi’an710054 China Key Laboratory of Subsurface Hydrology and Ecological Effect in Arid Region of the Ministry of Education Chang’an University Xi’an710054 China Key Laboratory of Eco-hydrology and Water Security in Arid and Semi-arid Regions of Ministry of Water Resources Chang’an University Xi’an710054 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi'An710049 China

Supercritical water (SCW) gasification technology can realize efficient utilization of coal, which can convert coal to hydrogen-rich gas. But polycyclic aromatic hydrocarbons and heavy components, intermediates of supercritical water gasification, are easy to form char, preventing complete gasification of coal. In this paper, phenol is recycled to reduce the formation of these intermediates during SCW gasification, and the regulation mechanism is investigated. The results illustrate that the organics removal rate reaches about 98% with the effect of phenol. Phenol can improve the gasification performance by promoting the conversion of heavy components to lightweight components. The transient reactivity of coal in the polycondensation stage is enlarged about 50 times with phenol. The regulation mechanism of phenol on the polycondensation stage during coal gasification is investigated by analyzing the evolution of microstructure in coal. Decomposition of SCW forms hydroxyl radicals, which replaces the substituents on benzene ring, making the benzene ring dissociate into small molecules that are easy to polymerize. The interacting force between phenol and multi-rings disrupts the conjugate structure, promoting the organics with multi-ting decomposed into small molecules. © 2024, The Authors. All rights reserved.

关键词： Coal

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Experimental Study on Liquid Immersion Preheating of Lithium-Ion Batteries Under Low Temperature Environment

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SSRN 2024年

作者： Bao, Jiakang Zhou, Zhifu Wu, Wei-Tao Wei, Lei Jizu, Lyu Li, Yang Huang, Heng 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 School of Mechanical Engineering Guangdong Ocean University Zhanjiang524088 China

In this paper, a single-phase immersion preheating experimental test platform is constructed to analyze the immersion preheating, the preheating performance, and the energy consumption. Immersion preheating has a major improvement on the low-temperature performance of the lithium cell, and the warming rate during preheating varies depending on the temperature (-25°C, -15°C, -5°C, 5°C, 15°C, 25°C) is very close to each other. The inlet temperature has a greater influence on the preheating performance than other factors, increasing the inlet temperature is favorable to rate of warming, but will increase the cell safety risks. flow rate and battery spacing increases on the rate of increase in temperature of the impact is gradually weakened, the rising inlet flows on the battery pack module temperature difference has a greater impact, the spacing increases on the battery cell and the battery pack temperature difference is gradually reduced, even so the maximum battery temperature difference is still controlled to 6℃ or less. In addition, immersion preheating has lower utilization of heat and higher energy consumption, and the preheating energy consumption at ambient temperature -25℃ has exceeded 80 % of the rated capacity of experimental battery packs. © 2024, The Authors. All rights reserved.

关键词： Energy utilization

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Experimental study on the submerged steam jet through side hole nozzle

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IOP Conference Series: Materials Science and engineering 2015年第1期88卷

作者： W Wang F Yuan Q B Zhao D T Chong W X Chen J J Yan State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 PR China

In this paper, the steam shape parameters and the condensation oscillation characteristics of the direct contact condensation of submerged steam jet into subcooled water were investigated through a side hole nozzle. Meanwhile, the dimensionless jet length and the expansion ratio versus pool water temperature and steam mass flux were obtained by measuring the photographs taken by a high speed camera. Both of them increased gradually with rise of pool water temperature and steam mass flux. A comparison of the shape parameters of three different style nozzles was also achieved. And a correlation of the dimensionless jet length was obtained, the predicted data agreed well with the experimental data, while the discrepancy was within ±5%. For the pressure oscillation versus steam mass flux, the peaks and the root mean square value of pressure oscillation were almost consistent in the range of 150-400 kgm-2s-1, while both of them increase in the range of 400-800 kgm-2s-1. The positive peak and negative peak were completely symmetrical.

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