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Effects of Hydrothermal and Hydrothermal Oxidation Pretreatments on Physicochemical Properties of High Value-Added Biochar Fuel Pellets and Activated Carbon Materials

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SSRN 2023年

作者： Lang, Sen Zhang, Shouyu Yang, Jifan Zhou, Yi Liu, Simeng Xu, Zihang Han, Xiuyuan Huang, Jiantian School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai200093 China Huazhan Aerospace Electric Appliance Co. LTD Aerospace Science and Industry Corporation Suzhou215129 China

In this paper, cotton stalk (CS) and Chinese fir sawdust (FS) were treated for hydrothermal pretreatment with or without H2O2, and then respectively pyrolyzed and activated to prepare biochar pellets and activated carbon materials. The results show that compared with hydrothermal pretreatment (HT), hydrothermal oxidation (HTO) pretreatment has stronger degradation ability of hemicellulose and cellulose. With the increase of pretreatment temperature, some decomposed substances repolymerize to form lignin-like substances. In the 160-260oC temperature range, the physical properties of biochar pellets prepared under HT 230oC and HTO 200oC are the best, and crystalline cellulose plays a key role in it. The calorific value and energy density of the biochar pellets obtained after pretreatment were consistent with the variation trend of their physical properties. The combustion characteristics of treated CS/FS biochar pellets gradually decreased with the increase of temperature. Compared with CS, FS biochar have better energy density and physical properties due to high cellulose content. The CS-HTO200-A has the highest specific surface area and pore volume, which is 118.1% and 111.7% higher than that of raw materials, and mainly consists of micropores. Cellulose is beneficial to increase the specific surface area of activated carbon, while lignin has the opposite effect. © 2023, The Authors. All rights reserved.

关键词： Physicochemical properties

Experimental and Kinetic Modeling Study on the Oxidation and Laminar Combustion Characteristics of Natural Gas

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SSRN 2023年

作者： Chen, Xiaoxiao Zeng, Wen Zheng, Weilin Hu, Erjiang Ma, Hongyu Liaoning Key Lab of Advanced Test Technology for Aerospace Propulsion System Shenyang Aerospace University Liaoning Shenyang110136 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shanxi Xi'An710049 China AECC Shenyang Engine Research Institute Shenyang110015 China

The oxidation process in the flow tube reactor at the conditions of P=0.1 MPa, T=500-1850 K, f=0.5, 1.0, 3.5, and the laminar combustion process in the constant volume combustion bomb at the conditions of P=0.1, 0.2, 0.3 MPa, T=300, 350, 400 K, f= 0.7-1.4, the O2 contents of 15%, 18% and 21%, the CO2 and H2O contents of 0%, 10%, and 20% of natural gas (0.9 methane/0.07 ethane/0.03 propane, mole fraction) were experimental tested. In the oxidation process of natural gas, with the equivalence ratio increasing, the starting and ending temperatures for oxidation reaction of natural gas are increased, the reaction temperatures corresponding to CO generation and consumption are higher, and the amount of NO production is decreased. In the the laminar combustion process of natural gas, at the conditions of higher pressure, equivalence ratio, CO2 and H2O contents, the flame front is not smooth as a large number of cracks and cell structures appear, and the flame is unstable. Moreover, with the initial temperature and oxygen content increasing or the initial pressure, CO2 and H2O contents decreasing, the laminar flame speed is increased. Furthermore, combined the path sensitivity analysis, rate of production analysis, reaction path analysis and the decoupling method, a reduced reaction mechanism (including 40 species and 189 reactions) of natural gas was developed. Through comparing with the calculated results by the Aramco 2.0 mechanism and the corresponding test data, the reduced reaction mechanism can well predict the oxidation, ignition delay and laminar combustion characteristics of natural gas under various conditions. © 2023, The Authors. All rights reserved.

关键词： Sensitivity analysis

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

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SSRN 2024年

作者： Chen, Yiwen Zhang, Dalin Jiang, Dianqiang Deng, Jian Zhang, Xisi 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 Nuclear Power Institute of China 328 Changshun Avenue Chengdu610213 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610213 China China Institute of Atomic Energy Beijing611731 China

To increase power density in nuclear reactors, the helical cruciform fuel (HCF) is designed as a fundamental element. 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 paper, friction factor and heat transfer coefficient empirical correlations of HCF single rod cooled by water were proposed using a geometric dimensionless number based on numerical simulation. The velocity field, and temperature distribution were obtained to discuss influences of geometric sizes on the fuel performance. Finally, correlations with a geometric dimensionless number were validated with various cases, whose application conditions were also proposed and discussed. This paper provides a guide for study of heat transfer and fluid flow in helical structures, and a reference for establishment of reactor system model using helical cruciform fuels. © 2024, The Authors. All rights reserved.

关键词： Heat transfer coefficients

Synthesis of Co3o4@C/Ti3c2tx Mxene-Type Composites for Enhanced Electromagnetic Wave Absorption

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SSRN 2024年

作者： Hou, Yunxi Jia, Zhen Zheng, Hanli Hu, Zewei Shen, Lu Liu, Dongyu Li, Lu Liu, Shiwei Liu, Yue Yu, Shitao 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 A VIC Research Institute for Special Structures of Aeronautical Composites 19 Jiqi Road Jinan250000 China

Highly efficient microwave absorbing materials have attracted widespread attention due to the harmful effects of electromagnetic pollution on the human body and electronic equipment. In this paper, Co3O4@C composites with core-shell structure were prepared by hydrothermal method using a simple strategy, and then Ti3C2Tx was assembled with core-shell Co3O4@C by electrostatic self-assembly method, which resulted in the successful attachment of Co3O4@C to the lamellar structure of Ti3C2Tx and the formation of MXene-based composite wave-absorbing Co3O4@C/Ti3C2Tx material. The composites exhibit strong electromagnetic wave absorption when the mass ratio of Co3O4@C to Ti3C2Tx was 1:2, with a minimum reflection loss of -35.2 dB at a matched thickness of only 4.5 mm. Excellent electromagnetic wave absorption performance Co3O4@C/Ti3C2Tx composite material was mainly attributed to the synergistic effect of the multiple reflection absorption of the core-shell structure and the high conductivity and large specific surface area of MXene material. These results indicate that Co3O4@C/Ti3C2Tx composites were promising candidates for electromagnetic absorption and provide new ideas for the design of MXene-based magnetic absorption materials. © 2024, The Authors. All rights reserved.

关键词： Composite materials

Study on the Flame Structure and flow Field of Hydrogen-Enriched Combustion in Array Micro-Tube

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SSRN 2024年

作者： Tian, Liang Feng, Wenbin Han, Xiao Liu, Yuzhi Liu, Hongfang Cai, Xiao School of Energy and Environmental Engineering Hebei University of Technology Tianjin300401 China National Key Laboratory of Science and Technology on Aero-Engine Aero thermodynamics Research Institute of Aero-Engine Collaborative Innovation Center for Advanced Aero-Engine Beihang University Beijing100191 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi’an710049 China

Addressing climate change and reducing greenhouse gas emissions are critical priorities. Utilizing hydrogen-rich methane or pure hydrogen as fuels within gas turbines, facilitated by array micro-tube premixed combustion technology, is anticipated to markedly accelerate the decarbonization process of the energy sector. In this study, the flame structure of the array micro-tube premixed burner under various fuel compositions was examined using OH-Planar Laser-Induced Fluorescence (OH-PLIF) and Particle Image Velocimetry (PIV) measurement techniques. The effects of the equivalence ratio (φ) and the hydrogen power ratio (HPR) on the characteristics of the flame front, including its curvature, density, volume, and the associated flow field properties, were discussed. As φ and HPR increase, the wrinkled structure of the flame front is significantly enhanced, with a more pronounced effect on smaller scales. This enhancement leads to the separation of the unburned pockets from the main flame. Concurrently, both the flame length and flame area decrease with the augmentation of φ and HPR, indicating a more concentrated combustion process and increased combustion intensity under hydrogen-enriched and pure hydrogen conditions. The study also observed a slight increase in both the negative and positive curvatures of the flame front, with a more notable increase in negative curvature. The increased negative curvature results in an elevated degree of wrinkling and a higher value of Σ (flame surface density), reaching a maximum of 0.876 mm-1 under the conditions where φ is 0.8 and (mean progress variable) is 0.5, resulting in the smallest observed flame volume of 100.6 mm3. Upon coupling the flame with the flow field, it was discovered that the exit flow field of the array micro-tube exhibits symmetry and a characteristic conical flame shape. The burning velocity of the side flame brushes increases, and the velocity peak shifts upstream. The above findings confirms that the additio

关键词： flow fields

Ab initio investigation of defect formation at ZrO2-CeO2 interfaces

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Physical Review B 2012年第8期86卷 085407-085407页

作者： Marco Fronzi Silvia Cereda Yoshitaka Tateyama Alessandro De Vita Enrico Traversa International Center for Materials Nanoarchitectonics (MANA) National Institute for Materials Science (NIMS) Tsukuba Japan Physics Department King's College London Strand London United Kingdom International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xian Jiaotong University Xian Shaanxi China

The structural and electronic properties of low index (100) and (111) ZrO2-CeO2 interfaces are analyzed on the basis of density functional theory calculations. The formation energy and relative stability of substitutional defects, oxygen vacancies, and vacancy-dopant complexes are investigated for the (100) orientation. By comparing these results with the ones obtained in bulk structures, we provide a possible explanation for the higher experimental ionic conductivity measured at the interface.

关键词： ZIRCONIUM oxide CERIUM oxides INTERFACES (Physical sciences) CRYSTAL defects ELECTRONIC structure

Numerical Simulations on Hybrid Thermal Management of Mini-Channel Cold Plate and Pcm for Lithium-Ion Batteries

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SSRN 2024年

作者： Liu, Yang Zhou, Zhifu Wu, Wei-Tao Wei, Lei Li, Yang Liu, Xinyu 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

In this study, a novel battery thermal management system (BTMS), combining phase change material (PCM) and mini-channel cold plates (MCPs), was modeled and analyzed. First, the effects on single cell cooling using MCPs and PCM alone are investigated at different coolant rates, temperatures, and PCM thicknesses. Then, the hybrid thermal management system (HTMS) is developed with the aim of reducing the cooling load of the PCM through hybridization with MCPs and the optimal combination of them is investigated. At the end of this work, the thermal performance of a battery pack with a hybrid thermal management structure has been analyzed, where the cold plate can take away the heat from the PCM to restore its thermal storage capacity. The results show that the combination of 3 channel and 10 mm PCM with 0.1 m/s coolant velocity and 20°C coolant temperature is the quit suitable regarding the cooling performance. Under 2C discharging rate, this design reduces the maximum battery temperature to 40°C, which is 32.5% lower, and the average temperature to 35℃, which is 41% lower than it without cooling. The study's findings offer potential new strategies and predictions for hybrid thermal management that utilize MCPs and PCM. © 2024, The Authors. All rights reserved.

关键词： Lithium-ion batteries

Curvature Adaptive Voxel-Based Monte Carlo Method with Application for Customized Retinal Laser Surgery

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SSRN 2024年

作者： Zhang, Hao Li, Dong Chen, Bin Zhang, Hanfeng Liang, Yao Zheng, Yuping Wang, Guoxiang State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Department of Ophthalmology 2nd affiliated hospital Medical School Xi’an Jiaotong University Xi’an710049 China Department of Mechanical Engineering The University of Akron AkronOH44325 United States

Accurate prediction of light propagation and energy deposition in biological tissues is crucial for the success of laser-based medical treatments. We propose a novel Curvature Adaptive Voxel-based Monte Carlo method (CAVMC) to correct for light reflection and refraction at curved interfaces by introducing coordinate transformation with an artificial surface parallel to the curved interface. This approach achieves an optimal balance between simulation accuracy and efficiency. Our study demonstrates that for small optical mismatches, the relative error can be reduced significantly, with the energy deposition error dropping from 34.7% to 6.6%. For large optical mismatches, CAVMC substantially improves accuracy, reducing computational errors by more than 50%. We validated CAVMC in a customized retinal laser therapy scenario for diabetic retinopathy, demonstrating its ability to accurately predict laser energy deposition and thermal effects, which is crucial for avoiding tissue damage during treatments. The efficiency and accuracy of the CAVMC method make it valuable for personalized retinal laser surgery and potentially other medical applications. Overall, CAVMC offers a robust tool for simulating light propagation in heterogeneous biological tissues, enhancing the precision and safety of medical treatments. © 2024, The Authors. All rights reserved.

关键词： Laser surgery

Numerical Simulations for Comparison of Cold Plate Cooling and Hfe-7000 Immersion Cooling in Lithium-Ion Battery Thermal Management

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SSRN 2024年

作者： Liu, Xinyu Zhou, Zhifu Wu, Wei-Tao Wei, Lei Hu, Chengzhi 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

In this work, fluorinated liquids can be used as a new immersion coolant for effective battery thermal management (BTM) because of their insulating and non-flammable inert characteristics. In this research, the liquid chosen for immersion cooling is HFE-7000, characterized by a boiling point of 34°C. The analysis of bubble kinetics is employed to investigate the heat transfer mechanism in two-phase immersion cooling by examining the behavior of bubbles during the boiling process. The square ternary Li-ion batteries are subjected under loads of 2C and 3C cooled by immersion cooling and a mini-channel cold plate as a comparison. It turns out that immersion liquid cooling modules offer superior thermal performance. Under constant current (CC), the peak temperature is reduced by 4.89°C and 9.31°C compared with the mini-channel cold plate cooling (CPC). Under dynamic load conditions, the maximum temperature rise of the battery is reduced by 29.89% and 43.89% compared to CPC. As a passive heat dissipation method, two-phase immersion cooling reduces the design requirements for active control. Also, it delivers an efficient battery thermal management system (BTMS) designed for upcoming electric vehicles (EVs). © 2024, The Authors. All rights reserved.

关键词： Lithium-ion batteries