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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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Research on the Solution of the Thermo-Hydro-Mechanical-Chemical Coupling Model Based on the Unified Finite Volume Method Framework

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SSRN 2024年

作者： Zhang, Weitao Han, Dongxu Wang, Bohong Chen, Yu-Jie Jiao, Kaituo Gong, Liang Yu, Bo Qingdao266580 China School of Mechanical Engineering Beijing Key Laboratory of Pipeline Critical Technology and Equipment for Deepwater Oil and Gas Development Beijing Institute of Petrochemical Technology Beijing102617 China National-Local Joint Engineering Laboratory of Harbour Oil and Gas Storage and Transportation Technology Zhejiang Key Laboratory of Petrochemical Environmental Pollution Control Zhejiang Ocean University No.1 Haida South Road Zhoushan316022 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

Most existing thermo-hydro-chemical-mechanical (THMC) coupling models for enhanced geothermal systems (EGS) employ a combination of finite volume method (FVM) and extended finite element method (XFEM), facing challenges in framework integration, programming complexity, and solution efficiency. To overcome these limitations, this study develops an innovative FVM-XFVM model based on the embedded discrete fracture model (EDFM) that significantly enhances the THMC coupling modeling process for fractured reservoirs with simplicity and efficiency. Rigorous comparative verification demonstrates the new model maintains accuracy while improving computational performance. For EGS applications, this model effectively captures spatiotemporal dynamics of coupled THMC processes with multi-component water-rock reactions. The approximately 3°C temperature deviation between multi-component and single-component models after long-term operation demonstrates the necessity of incorporating multi-component reactions into THMC models for accurate forecasts. This work substantially improves the predictability and efficiency of long-term heat production forecasts for EGS reservoirs. © 2024, The Authors. All rights reserved.

关键词： Finite volume method

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Effects of velocity ratio on turbulent mixing layer at high Reynolds number

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Journal of Physics: Conference Series 2009年第1期147卷

作者： Fude Guo Bin Chen Liejin Guo Ximin Zhang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

In this paper the effect of velocity ratio on plane mixing layer was experimentally investigated by Particle Image Velocimetry (PIV). The velocity ratio between low and high speed side are 0.25 and 0.50, respectively. The Reynolds number based on the velocity difference of two streams and hydraulic diameter of the channel is 66000. The results indicate that the maximum mean Reynolds stress on the same cross section is decreasing with the velocity ratio increasing. The maximum dimensionless mean vorticity is decreasing according to an exponential law along the stream-wise direction and the decreasing speed of dimensionless mean maximum vorticity is increasing with the velocity ratio increasing. The dimensionless vorticity caused by plate wake is decreasing sharply in a very short distance along the down stream wise direction and the decreasing speed is faster when the velocity ratio is larger.

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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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Drop deformation and breakup with diffuse interface method

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AIP Conference Proceedings 2010年第1期1207卷

作者： S. L. Chen C. Z. Lin L. J. Guo Y. S. Wang State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an 710049 China

Two‐dimensional numerical simulation of the deformation and breakup of an isolated liquid drop suspended in immiscible viscous fluid under shear flow was performed with the diffuse interface method. The governing equations of the model were described by Navier—Stokes—Cahn—Hilliard equations. The surface tension was treated as a modified stress. In the paper, the critical Capillary number was plotted as a function of viscosity ratios with the method of approximation. Besides, From the numerical observations, the breakup of the droplets occurred by three mechanisms, namely, necking, end pinching, and capillary instability. Quantitative results for the deformation and breakup of drop are presented.

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Light-Enhanced Thermochemical Production of Solar Fuels from Methane Via Nickel-Based Redox Cycle

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SSRN 2022年

作者： Liu, Mingkai Zhang, Jinrui Yang, Tianlong Rao, Qiong Gai, Zhongrui Zhao, Jianxiong Pan, Ying Su, Dong Jin, Hongguang Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing100190 China University of Chinese Academy of Sciences Beijing100049 China International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University 710049 China Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing100190 China

Thermochemical methane reforming driven by solar energy is one of the efficient ways to store the renewable energy and to simultaneously reduce greenhouse gas emission. We report reaction reactivity of steam reforming of methane using nickel-based oxygen carrier driven by pure thermal heating and direct light irradiation in the same reactor. We find that the light-driven steam methane reforming system show improved conversion and reaction rate compared to that driven by pure thermal heating. We observed that illuminated NiO/NiAl2O4 achieved the same methane conversion rates and the H2 production rate comparable to those obtained on the same samples operated with only a thermal energy input, but at temperatures up to ~50 K lower. Based on in situ diffuse reflectance Infrared Fourier transform spectroscopy (DRIFTs) experiments, we postulate that light on the nickel oxide surface act to activate CH4 desorption and facilitate CHxO species evolution. By the combined effects of selection of chemical looping reactions and operation conditions, the solar-to-fuel efficiency of 16% was achieved. The results showcase the design of more energy-efficient chemical processes with a significant fraction of energy input provided in the form of direct sunlight irradiation as a potent pathway that can complement extremely high-temperature thermochemistry efforts in the quest for more efficient solar fuel production. © 2022, The Authors. All rights reserved.

关键词： Fourier transform infrared spectroscopy

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The Interaction and Activation of Fe2o3/Ceo2 Oxygen Carrier in Chemical Looping Dry Reforming of Methane

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SSRN 2024年

作者： Zhang, Jinrui Liu, Xiaozhi Pan, Yue Wang, Yuhan Yang, Tianlong Li, Peng Shen, Yuanhui Su, Dong Pan, Ying Jin, Hongguang Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing100190 China University of Chinese Academy of Sciences Beijing100049 China Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing100190 China International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University 710049 China

Chemical looping dry reforming of methane (CL-DRM) holds great promise for both CO2 utilization and syngas production with high efficiencies. The structure and component of oxygen carriers (OCs) are critical factors that influence the CL-DRM performances, such as reaction activity and production selectivity. Incorporating CeO2 is known to enhance the reactivity and stability of Fe2O3 for chemical looping reforming. However, the underlying mechanism of how CeO2 synergistically interact with Fe2O3 to enhance performances is still not clear. In this work, we comparatively investigate CeO2 supported Fe2O3 OCs in interfacial and physical Fe-Ce contact modes. The OC with sol-gel method achieves 80% CH4 conversion and 96% CO selectivity, significantly improved from OC with the mechanically mixed sample. Additionally, we found a strong interaction between Fe2O3 and CeO2 components, resulting in the formation of CeFeO3 after the first cycle. Our in-situ environmental transmission electron microscopy study shows that the Fe2O3-CeO2 interaction promotes the oxygen release during the reduction. Iron exhibited significant activity with ceria under CO2, dissolving into CeO2 lattice and forming CeFeO3. Density function theory results suggest that the improved reactivity of Fe2O3/CeO2 OC results from the enhanced oxygen ion migration in CeFeO3 © 2024, The Authors. All rights reserved.

关键词： Sol-gels

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Degradation of Polystyrene to Aromatic Oils with Nio@C Catalyst in Supercritical Co2

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SSRN 2024年

作者： Liu, Yanbing Mao, Liuhao Kang, Xing Li, Yi Zhao, Qiuyang Jin, Hui Meng, Wei Shi, Jinwen Guo, Liejin International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University 28 West Xianning Road Shaanxi Xi’an710049 China Hunan Provincial Key Lab of Dark Tea and Jin-Hua Departmet of Material & Chemical Engineering Hunan City University 518 East Yingbin Road Hunan Yiyang413000 China

One of the most promising ways to dispose of plastic pollution in the future is chemical recycling of plastic, and in particular supercritical fluids with excellent fluidity and transferability have shown great attraction in the disposal of plastic. Herein, catalytic degradation of polystyrene (PS) plastic in supercritical carbon dioxide (Sc-CO2) was realized with high yield of aromatic oils. NiO with simple preparation process, and high catalytic activity and stability in Sc-CO2 was doped with carbon material to prepare NiO@C catalyst with improved catalytic performance. Compared with NiO, NiO@C catalyst had rich porous structure and strong acidic sites, resulting in higher catalytic activity. The NiO@C catalyzed degradation of PS in Sc-CO2 yielded aromatic oils as high as 89.3 ± 0.6 wt% at 300oC with a reaction time of 2 h and a catalyst loading amount of 10 wt%. Moreover, the NiO@C catalyst degraded PS in Sc-CO2 for three cycles without obvious change in the catalytic performance. Sc-CO2 not only played a favorable role in swelling PS, but also inhibited the formation of coke, beneficial for the degradation of PS. Furthermore, CO2 was be consumed as an oxidant to generate new products and reduce greenhouse gas emission. The highly efficient catalytic conversion of PS to aromatic oils in Sc-CO2 via NiO@C catalyst provides a potential route for simultaneously recycling plastic and sequestering carbon. © 2024, The Authors. All rights reserved.

关键词： Carbon dioxide

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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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PIV measurement of turbulent mixing layer flow with polymer additives

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Journal of Physics: Conference Series 2009年第1期147卷

作者： T Ning F Guo B Chen X Zhang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Turbulent mixing layer flow with polymer additives was experimentally investigated by PIV in present paper. The velocity ratio between high and low speed is 4:1 and the Reynolds number for pure water case based on the velocity differences of two steams and hydraulic diameter of the channel ranges from 14667~73333. flow field and turbulent quantities of turbulent mixing layer with 200ppm polymer additives were measured and compared with pure water mixing layer flow. It is shown that the dynamic development of mixing layer is greatly influenced by polymer addictives. The smaller vortices are eliminated and the coherent structure is much clearer. Similar with pure water case, Reynolds stress and vorticity still concentrate in a coniform area of central part of mixing layer and the width will increase with the Reynolds number increasing. However, compared with pure water case, the coniform width of polymer additives case is larger, which means the polymer additives will lead to the diffusion of coherent structure. The peak value of vorticity in different cross section will decrease with the development of mixing layer. Compared with pure water case, the vorticity is larger at the beginning of the mixing layer but decreases faster in the case with polymer additives.

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