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A mixed discontinuous Galerkin method with symmetric stress for Brinkman problem based on the velocity-pseudostress formulation

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arXiv

arXiv 2019年

作者： Qian, Yanxia Wu, Shuonan Wang, Fei Wang, Fei School of Mathematics and Statistics Xi'An Jiaotong University Xi'an Shaanxi710049 China School of Mathematical Sciences Peking University Beijing100871 China School of Mathematics and Statistics State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an Shaanxi710049 China

The Brinkman equations can be regarded as a combination of the Stokes and Darcy equations which model transitions between the fast flow in channels (governed by Stokes equations) and the slow flow in porous media (governed by Darcy?fs law). The numerical challenge for this model is the designing of a numerical scheme which is stable for both the Stokes-dominated (high permeability) and the Darcy-dominated (low permeability) equations. In this paper, we solve the Brinkman model in n dimensions (n = 2, 3) by using the mixed discontinuous Galerkin (MDG) method, which meets this challenge. This MDG method is based on the pseudostress-velocity formulation and uses a discontinuous piecewise polynomial pair PSk+1.Pk(k ≥ 0), where the stress field is symmetric. The main unknowns are the pseudostress and the velocity, whereas the pressure is easily recovered through a simple postprocessing. A key step in the analysis is to establish the parameter-robust inf-sup stability through specific parameter-dependent norms at both continuous and discrete levels. Therefore, the stability results presented here are uniform with respect to the permeability. Thanks to the parameter-robust stability analysis, we obtain optimal error estimates for the stress in broken H(div)-norm and velocity in L2-norm. Furthermore, the optimal L2 error estimate for pseudostress is derived under certain conditions. Finally, numerical experiments are provided to support the theoretical results and to show the robustness, accuracy, and flexibility of the MDG method. Copyright © 201., The Authors. All rights reserved.

关键词： Stability

Zero-Energy Nonlinear Temperature Control of Lithium-Ion Battery Based on a Shape Memory Alloy

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SSRN 2024年

作者： Li, Yang Bai, Minli Zhou, Zhifu Wu, Wei-Tao Wei, Lei Hu, Chengzhi Liu, Xinyu Gao, Shuai Li, Yubai Song, Yongchen Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education Dalian University of Technology Dalian116023 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

Improving the poor performance of lithium-ion battery (LIB) in extreme temperatures is essential to promoting electric vehicles (EVs) into wider application. The most severe challenge for the existing battery thermal management systems (BTMSs) is to overcome the contradiction between excellent heat dissipation at high temperatures and effective insulation at low temperatures. Here, we propose a zero-energy nonlinear temperature control strategy based on thermal regulator. The designed thermal regulator based on shape memory alloy (SMA) can switch the heat flux on the battery surface according to its temperature without any power supply or logic control and provide the desirable thermal functions. This thermal regulator increases the battery capacity by 55.44% in the cold environment of -20℃ compared to the baseline BTMS with superior heat dissipation. Simultaneously, it can limit the battery peak temperature to near the FS49 boiling point (49℃) in the hot environment of 45℃ to ensure safety. Furthermore, we demonstrate that the thermal regulator enables thermal runaway to be effectively suppressed inside the battery, reducing the emission of combustible or toxic gases by 72.26%, which is reported for the first time. Finally, we simplify the design of the thermal regulator from the perspective of system integration and demonstrate the feasibility of the thermal regulator at the battery pack level. © 2024, The Authors. All rights reserved.

关键词： Lithium-ion batteries

A Piv Measurement and Numerical Simulation of Gas‐Liquid Two‐Phrase flow in An Aeration Tank

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AIP Conference Proceedings 2007年第1期914卷 453-457页

作者： Wen Cheng Chun‐Di Yang Yuichi Murai Fujio Yamamoto 1State Key Laboratory of Multiphase Flow in Power Engineerig Xi’ann Jiaotong University Xi’an 710049 China 2Environment Research Institute Xian University of Technology Xian 710048 China 3Div. of Mec. Science Graduate School of Engineering Hokkaido University Japan 4Graduate School of Engineering University of Fukui Bunkyo 3‐9‐1 Fukui 910‐8507 Japan

Aeration plays an important role in the treatment of activated sludge. The aeration performance is deeply affected by the movement law of bubble liquid flow in aeration tank. In order to discuss the influence of gas‐phase, liquid‐phase motions in an aeration tank on the sewage disposal, three kinds of boundaries and initial conditions were applied in the experiment to study the law of two‐phase flow. A developed two‐equation turbulence model was employed in this paper. Results obtained by experiment are compared with those from the mathematical model. It is found that the results of measurement and simulation agree with each other.

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Thermal Management for the Prismatic Lithium-Ion Battery Pack by Immersion Cooling with Fluorinated Liquid

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SSRN 2024年

In this study, a novel FS49-based battery thermal management system (BTMS) was proposed and tested for cooling the prismatic lithium-ion battery (LIB) module. The boiling of dielectric refrigerant occurred at the battery surface, which provided strong and uniform cooling for each battery cell. The results show that the peak temperature difference of liquid immersion cooling (LIC) module during 1. rate discharging and charging was reduced by 91.3% and 94.44%, respectively, compared to the natural convection (NC) module. The reduction of temperature nonuniformity greatly reduced the state of charge (SOC) inhomogeneity of different cells within the module. Moreover, the energy density of LIC module can be optimized by reducing the cell spacing and liquid filling ratio. Comparing with 1.0% filling rate, the module maximum temperature corresponding to 25% filling rate (with wick) during 2C rate discharging is only increased by 1.6°C, however, the module peak temperature difference is reduced by 53.3%, and the energy density is increased by 1..1.%. In addition, Equivalent circuit model (ECM) and volume of fluid (VOF) model were used to simulate the LIC module, and the numerical results are in good agreement with the experimental data. This study provides a systematic design plan and numerical method for the {1. application of LIC in the field of BTMS. © 2024, The Authors. All rights reserved.

关键词： Lithium-ion batteries

Atomic Nickel on Graphitic Carbon Nitride as a Visible Light-Driven Hydrogen Production Photocatalyst Studied by X-ray Spectromicroscopy

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ACS Sustainable Chemistry and engineering 2023年第14期11卷 5390-5399页

作者： Huang, Yu-Cheng Li, Yanrui Arul, K. Thanigai Ohigashi, Takuji Nga, Ta Thi Thuy Lu, Ying-Rui Chen, Chi-Liang Chen, Jeng-Lung Shen, Shaohua Pong, Way-Faung Dong, Chung-Li Chou, Wu-Ching Department of Electrophysics National Yang Ming Chiao Tung University Hsinchu30010 Taiwan Research Center for X-ray Science & Department of Physics Tamkang University New Taipei City25137 Taiwan International Research Center for Renewable Energy State Key laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China Photon Factory Institute of Materials Structure Science High Energy Accelerator Research Organization Tsukabu305-0801 Japan UVSOR Synchrotron Facility Institute for Molecular Science Okazaki444-8585 Japan National Synchrotron Radiation Research Center Hsinchu30010 Taiwan

The photocatalytic production of solar hydrogen through water splitting by graphitic carbon nitride (g-C3N4) has gained substantial interest due to its advantageous characteristics, such as eco-friendliness, wealth on the earth, favorable bandgap, and easy preparation. Nevertheless, the performance for photocatalytic overall water splitting has been significantly restricted owing to the rapid recombination of charge carriers and slow catalytic kinetics. This investigation demonstrates the utilization of a single-atom Ni-terminating agent to coordinate with the heptazine moieties of g-C3N4, resulting in the formation of a new electronic orbital. g-C3N4 with single-atom Ni-termination can achieve highly efficient photocatalytic overall water splitting into H2 and H2O2 upon visible light irradiation, without requiring the use of any additional cocatalysts. The underlying cause of the enhanced photocatalytic performance of single-atom Ni-incorporated g-C3N4 in hydrogen evolution reaction is identified using synchrotron X-ray spectroscopy and microscopy. The X-ray spectro-microscopic results discover that the new hybrid orbital that is critical for optimizing photocatalysis is associated with carbon defects. The atomic and electronic structures and the band gap of g-C3N4 are adjusted by the new hybrid orbital. Moreover, it synergistically enhances visible light absorption, thereby promoting the separation and transfer of photogenerated charge carriers. The single-atom Ni and the adjacent C atom are recognized as the active sites for water oxidation and reduction, respectively, supporting the efficient photocatalytic splitting of water via a two-electron transfer pathway. This study demonstrated a promising material design for promoting photocatalytic activity in solar energy conversion applications. © 2023 American Chemical Society

关键词： Electronic structure

Unveiling the Unexpected C-C Dissociation Capacity and Intrinsic Mechanism of Undercoordinated Pd Cluster/Ceo2 for the Efficient and Stable Catalytic Mineralization of Propane

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SSRN 2022年

作者： Xia, Lianghui Jian, Yanfei Wang, Jingjing Wang, Yao Chai, Shouning Liu, Yujie Li, Lu Yu, Yanke Albilali, Reem He, Chi State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Shaanxi Xi’an710049 China Department of Chemistry College of Science Imam Abdulrahman Bin Faisal University P.O. Box 1982 Dammam31441 Saudi Arabia National Engineering Laboratory for VOCs Pollution Control Material & Technology University of Chinese Academy of Sciences Beijing101408 China

Light alkanes extensively presented in industrial exhausts have led tremendous harm to the atmospheric environment and human health. However, their stable molecule structure and inferior adsorption and activation efficiency make them as one category of the most intractable pollutants to be efficient controlled. Herein, we developed a Pd single cluster/CeO2 catalyst (Pd/CeO2-SCC-R) by a scalable deposition precipitation strategy, which demonstrates unexpected activity (propane total destructed below 300 oC) and thermal stability (even dramatically treated at 800 oC for multiple cycles) attributed to the strong metal-support interaction (SMSI) and unsaturated Pd metal sites caused by the shorter Pd-O distance. Mechanism studies determine that the Pd/CeO2-SCC-R possesses highly-efficient C-C cleavage ability owing to the persistent formation of large amounts of oxygen vacancies and low-coordinated Pd species, and the addition of H2O intrinsically accelerates propane activation and intermediate mineralization attributed to suppression of by-products by OH species. In comparison, the Pd single atom/CeO2 catalyst is preferentially for C-H bonds cleavage and inactive for C-C bonds cracking due to the saturated Pd sites anchored to the oxygen of supports directly, which generates more non-oxidation by-products as propyne and propylene, inhibiting the continuous decomposition of propane due to the retardatory oxidation of pyruvate species. The present work sheds critical insight to the production of fulfilling products through the directional cleavage of C-C/C-H bonds in the activation of light alkane molecules. © 2022, The Authors. All rights reserved.

关键词： Oxygen vacancies

Pattern and Dynamics of Methane/Water Two-Phase flow in Deep-Shale Illite Nanoslits

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SSRN 2024年

作者： Wang, Rui Yang, Xu Li, Gao Zheng, Wenxiu Zou, Zhenhai Sun, Chengzhen State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China State Key Laboratory of Oil and Gas Reservoir Geology and Exploration Southwest Petroleum University Sichuan Chengdu610500 China Air and Missile Defense College Air Force Engineering University Shaanxi Xi’an710051 China Wuhan Second Ship Design and Research Institute Wuhan430202 China

Developing deep shale gas is crucial for the sustainable development of unconventional energy sources. Deep shale has a high illite content, and understanding the structure and flow behaviors of methane and water coexisting in deep shale illite nanoslits is essential for methane transport and production in deep shale reservoirs. Here, molecular dynamics simulations were performed to investigate the methane and water flow characteristics in slit-shaped illite nanopores. The effects of water saturation, acceleration, and pore size on two-phase flow are elucidated. The results show that water molecules preferentially adsorb on the surface of the illite channel. As the water saturation increases, the water phase gradually forms a water film, water bridge, and water lock, ultimately creating methane nanobubbles surrounded by the water phase. The existence of the water phase compresses the methane flow space. With increasing water saturation, the peak methane density near the channel wall gradually disappears, and the density distribution curves show parabolic shapes. The methane flow flux decreases with the increase of water saturation, mainly when the water saturation increases from 0% to 40%. In illite slits with pore sizes ranging from 2 to 4 nm, the flow rates of water and methane increase with increased pore size. These results are expected to provide insights into developing deep shale gas reservoirs, such as optimizing hydraulic fracturing design and reliably predicting production performance. © 2024, The Authors. All rights reserved.

关键词： Methane

Multi-source driven capillary plane radiation air conditioning system

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AIP Conference Proceedings 2017年第1期1864卷

作者： Juanjuan Hu Mofeng Qu Huasheng Wang Shiyao Ni State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an China

A new absorption refrigeration system, which is driven by solar energy, biomass energy and geothermal energy simultaneously, was designed with capillaries as its radiation surface. Likewise, variations of water temperature in the capillaries with the change in both time and its flow rate were experimentally researched as well as how COP of the system varies with the surrounding temperature. The following conclusions have been obtained: Common refrigeration demand can be met by the system after its operation in 1.hour; with the increase in water flow rate in the capillaries, its temperature, which drops down after an increase, gets its peak value at the flow rate of 4.5-5.5 L/min; COP of the system decreases with the rise of surrounding temperature, thus it’s better to keep it from direct sunlight. With the utilization of natural energy and the structure of capillaries, the system’s advantages in simple structure, low cost, environment-friendly working process and nice performance lead to promising application prospects, especially in residence refrigeration in countryside.

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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