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Dynamics and Structure Formation of Confined Polymer Thin Films Supported on Solid Substrates

POLYMERS 2021年第10期13卷 1621-1621页

作者： Rahman, Mujib Ur Xi, Yonghao Li, Haipeng Chen, Fei Liu, Dongjie Wei, Jinjia Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Xi An Jiao Tong Univ Sch Chem Engn & Technol Xian 710049 Peoples R China

The stability/instability behavior of polystyrene (PS) films with tunable thickness ranging from higher as-cast to lower residual made on Si substrates with and without native oxide layer was studied in this paper. For further extraction of residual PS thin film (h(resi)) and to investigate the polymer-substrate interaction, Guiselin's method was used by decomposing the polymer thin films in different solvents. The solvents for removing loosely adsorbed chains and extracting the strongly adsorbed irreversible chains were selected based on their relative desorption energy difference with polymer. The PS thin films rinsed in chloroform with higher polarity than that of toluene showed a higher decrease in the residual film thickness but exhibited earlier growth of holes and dewetting in the film. The un-annealed samples with a higher oxide film thickness showed a higher decrease in the PS residual film thickness. The effective viscosity of PS thin films spin-coated on H-Si substrates increased because of more resistance to flow dynamics due to the stronger polymer-substrate interaction as compared to that of Si-SiOx substrates. By decreasing the film thickness, the overall effective mobility of the film increased and led to the decrease in the effective viscosity, with matching results of the film morphology from atomic force microscopy (AFM). The polymer film maintained low viscosity until a certain period of time, whereupon further annealing occurred, and the formation of holes in the film grew, which ultimately dewetted the film. The residual film decrement, growth of holes in the film, and dewetting of the polymer-confined thin film showed dependence on the effective viscosity, the strength of solvent used, and various involved interactions on the surface of substrates.

关键词： polymer thin film solvent rinsing viscosity dewetting

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Kinetic modeling of carbon monoxide oxidation and water gas shift reaction in supercritical water

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JOURNAL OF SUPERCRITICAL FLUIDS 2021年 171卷 105165-105165页

作者： Li, Guoxing Fan, Mingjing Lu, Youjun Glarborg, Peter Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China Tech Univ Denmark Dept Chem & Biochem Engn DK-2800 Lyngby Denmark

Carbon monoxide is a primary intermediate in supercritical water oxidation (SCWO) processes. A validated chemical kinetic model for hydrogen oxidation in supercritical H2O/CO2 mixtures was expanded to describe carbon monoxide oxidation and water gas shift reaction in supercritical water (SCW). The model performance was evaluated against experimental data in literature. Data for carbon monoxide oxidation were well reproduced by the model. Underprediction of hydrogen formation was attributed mostly to hydrolysis reactions occurring on the reactor surface. The rate of water gas shift reaction observed experimentally under SCW conditions strongly exceeds that predicted by the model. Analysis indicates that the observed WGS reaction is largely due to catalytic effects on the reactor surface, even though trace impurities of oxygen present in the experiments may also enhance reaction. Pressure corrections on thermodynamic properties and inclusion of HOCHO subset were found to have negligible influence on modeling results. CO + OH = CO2 + H, HO2 + H2O - OH + H2O2 and OH + HO2 - O-2 + H2O were identified as the most important elementary reactions by sensitivity analysis.

关键词： Kinetic modeling Carbon monoxide oxidation Water gas shift reaction Supercritical water

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CFD simulation on the transient process of coolant mixing phenomenon in reactor pressure vessel

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ANNALS OF NUCLEAR ENERGY 2021年 153卷 108045-108045页

作者： Li, Jun Wang, Mingjun Fang, Di Wang, Jie Liu, Dong Tian, Wenxi Qiu, Suizheng Su, G. H. Xi An Jiao Tong Univ Sch Nucl Sci & Technol State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Nucl Power Inst China Sci & Technol Reactor Syst Design Technol Lab Chengdu Peoples R China

The emergency coolant cooling system (ECCS) is designed to inject coolant into reactor pressure vessel (RPV) during loss of coolant accidents, ensuring the sufficient coolant inventory in the nuclear reactor core. During this process, the cold water mixes with high temperature coolant in the primary loop, making the wall of RPV and cold legs suffer severe pressurized thermal shock (PTS) and threatens the integrity of primary loop. In this study, coolant mixing phenomena in the experiment UPTF, which is a 1/1 full-scale model of the PWR with four coolant loops in Germany, was studied numerically using the CFD software Fluent. The best practice guideline for coolant mixing study using CFD method in the reactor primary loop and RPV, including the suitable turbulent model, geometry simplification and mesh conditions, was concluded. The detailed three dimensional thermal hydraulic parameter distributions were achieved and the effect of coolant injection rates on the mixing process is also obtained. Results show that the mixing effect is enhanced due to the existence of reverse flow at the core entrance sections. The high injection rate provides more timely coolant supplement and reduces the possible core exposure time. However, as the injection rate increases, more intensive disturbance on the temperature and velocity fields appear, which is more likely to cause the thermal fatigue. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： CFD Coolant mixing RPV Pressurized thermal shock Best practice guideline

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MOF-Derived CoSe2 Nanoparticles/Carbonized Melamine Foam as Catalytic Cathode Enabling Flexible Li-CO2 Batteries with High Energy Efficiency and Stable Cycling

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SMALL 2024年第27期20卷 2310530-2310530页

作者： Wang, Ke Liu, Limin Liu, Dongyu Wei, Yuantao Liu, Yanxia Wang, Xinqiang Vasenko, Andrey S. Li, Mingtao Ding, Shujiang Xiao, Chunhui Pan, Hongge Xian Technol Univ Inst Sci & Technol New Energy 2 Xuefuzhonglu Rd Xian 710021 Shaanxi Peoples R China Xi An Jiao Tong Univ Sch Chem Xian Key Lab Sustainable Energy Mat Chem 28 Xianning West Rd Xian 710049 Shaanxi Peoples R China HSE Univ 20 Myasnitskaya St Moscow 101000 Russia Xi An Jiao Tong Univ Int Res Ctr Renewable Energy IRCRE State Key Lab Multiphase Flow Power Engn MFPE 28 Xianning West Rd Xian 710049 Shaanxi Peoples R China

Rechargeable aprotic Li-CO2 batteries have aroused worldwide interest owing to their environmentally friendly CO2 fixation ability and ultra-high specific energy density. However, its practical applications are impeded by the sluggish reaction kinetics and discharge product accumulation during cycling. Herein, a flexible composite electrode comprising CoSe2 nanoparticles embedded in 3D carbonized melamine foam (CoSe2/CMF) for Li-CO2 batteries is reported. The abundant CoSe2 clusters can not only facilitate CO2 reduction/evolution kinetics but also serve as Li2CO3 nucleation sites for homogeneous discharge product growth. The CoSe2/CMF-based Li-CO2 battery exhibits a large initial discharge capacity as high as 5.62 mAh cm(-2) at 0.05 mA cm(-2), a remarkably small voltage gap of 0.72 V, and an ultrahigh energy efficiency of 85.9% at 0.01 mA cm(-2), surpassing most of the noble metal-based catalysts. Meanwhile, the battery demonstrates excellent cycling stability of 1620 h (162 cycles) at 0.02 mA cm(-2) with an average overpotential of 0.98 V and energy efficiency of 85.4%. Theoretical investigations suggest that this outstanding performance is attributed to the suitable CO2/Li adsorption and low Li2CO3 decomposition energy. Moreover, flexible Li-CO2 pouch cell with CoSe2/CMF cathode displays stable power output under different bending deformations, showing promising potential in wearable electronic devices.

关键词： carbonized melamine foam flexible electronics free-standing electrode lithium-CO2 batteries transition metal selenides

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Green hydrogen economy: Prospects and policies in Vietnam

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INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 2023年第80期48卷 31049-31062页

作者： Hoang, Anh Tuan Pandey, Ashok Lichtfouse, Eric Bui, Van Ga Veza, Ibham Nguyen, Huu Luong Nguyen, Xuan Phuong HUTECH Univ Inst Engn Ho Chi Minh City Vietnam CSIR Indian Inst Toxicol Res Ctr Innovat & Translat Res Lucknow 226001 India Kyung Hee Univ 26 Kyungheedae Ro Seoul 02447 South Korea Univ Petr & Energy Studies Sustainabil Cluster Sch Engn Dehra Dun 248007 Uttarakhand India Ctr Energy & Environm Sustainabil Lucknow 226029 India Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China Univ Danang Univ Sci & Technol Danang Vietnam Univ Teknol PETRONAS Dept Mech Engn Seri Iskandar 32610 Malaysia Vietnam Petr Inst Hanoi Vietnam Ho Chi Minh City Univ Transport PATET Res Grp Ho Chi Minh City Vietnam

Hydrogen (H2) plays an important role in the energy transition toward a zero-carbon economy, in which green H2 could replace fossil fuels in the refining, petrochemical, fer-tilizer, steel, cement, electricity, and transportation sectors. More importantly, the deployment of green H2 strategies could ensure energy security and create an efficient way of using national resources. Vietnam has been considered as a country with abundant resources to produce green H2 but several limitations slow down the transition to a green H2 economy. Therefore, this article reviews the progress and potential of green H2 pro-duction using solar and wind energy in Vietnam. In addition, the article analyzed the roadmaps and policies of various countries worldwide for the green H2 economy comprehensively aiming to make policy recommendations for Vietnam. Overall, the green H2 economy could promote Vietnam's stabilized socio-economic development according to the expected goals of the new era. Moreover, developing a green H2 economy could contribute to building the image of Vietnam as a green country, attracting foreign investment and sustainable development.& COPY;2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Hydrogen economy Green hydrogen Policy recommendation Sustainable development Net-zero goal Vietnamese policy

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A porous medium model for simulating conjugate heat transfer between wire-wrapped fuel bundles under forced and mixed convection

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ANNALS OF NUCLEAR ENERGY 2021年 151卷 107906-107906页

作者： Chen, Yutong Liang, Yu Zhang, Dalin Wang, Shibao Wang, Chenglong Deng, Jian Tian, Wenxi Qiu, S. Z. Su, G. H. Xi An Jiao Tong Univ Sch Nucl Sci & Technol Shaanxi Key Lab Adv Nucl Energy & Technol State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Nucl Power Inst China 328 Changshun Ave Chengdu 610213 Peoples R China

Wire-wrapped fuel bundles have been widely used in SFRs, and the conjugate heat transfer between wire-wrapped fuel bundles plays a key role in safety characteristics of SFRs. However, due to the existence of helical wire spacers, the geometry of fuel bundle becomes quite complicated, bringing challenges to realistic CFD modeling. A porous medium model for simulating conjugate heat transfer between fuel bundles have been proposed in this study. The geometries of fuel rods and wrapper tubes are preserved and helical wire spacers are treated as solid body of porous medium in this model. The flow resistance induced by helical wire spacers is considered by adding additional flow resistance source terms to momentum equation and the transverse mixing effects caused by wire spacers and thermal plumes are accounted by modifying diffusion terms in energy equation of porous medium model. The sodium experiment of 19-pin wire-wrapped fuel bundle under forced convection performed by ORNL and sodium experiments of multi-bundle systems named CCTL-CFR and PLANDTL-DHX under mixed convection conducted by JNC were selected as benchmark. Comparison results show that under both forced and mixed convection, this model could attain considerable accuracy in the prediction of conjugate heat transfer between fuel bundles with relatively low computational cost and have the potential to simulate core-wide temperature distribution of SFR. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： SFR Wire-wrapped fuel bundle Conjugate heat transfer Porous medium model CFD

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A Subchannel Analysis Code Star for Sodium-Cooled Fast Reactor

SSRN

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SSRN 2022年

作者： Liang, Yu Zhang, Dalin Zhang, Jing Liu, Xiao Liu, Yapeng Zhou, Lei Chen, Yutong Mikityuk, Konstantin Wang, Xiaoyu Tian, Wenxi Qiu, Suizheng Su, Guanghui School of Nuclear Science and Technology Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'An710049 China Nuclear Power Institute of China 328 Changshun Avenue Chengdu610213 China Paul Scherrer Institute Villigen PSI5232 Switzerland

The strong coupling heat transfer between subassemblies and inter-wrapper gaps is closely related to the safety of the sodium-cooled fast reactor (SFR). Therefore, it is very important to carry out a detailed thermal hydraulic analysis of the core. In this paper, the inter-wrapper channel is modeled using the subchannel method, and a two-fluid subchannel analysis model is developed based on the staggered grid method. The core thermal-hydraulic analysis code STAR (Subchannel Thermal-hydraulic Analysis code for SFR) is developed by using SIMPLE algorithm. © 2022, The Authors. All rights reserved.

关键词： Sodium-cooled fast reactors

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Ag-Modified g-C3N4 Prepared by a One-Step Calcination Method for Enhanced Catalytic Efficiency and Stability

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ACS OMEGA 2020年第31期5卷 19615-19624页

作者： Liu, Runxue Yang, Wanliang He, Guiwei Zheng, Wei Li, Maokun Tao, Wenliang Tian, Mengkui Guizhou Univ Coll Chem & Chem Engn Guiyang 550025 Guizhou Peoples R China Xi An Jiao Tong Univ Int Res Ctr Renewable Energy State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

Ag-decorated g-C3N4 (denoted as Ag/CN-x) was prepared by a one-step calcination method, and the influences of calcination time on structure, morphology, surface composition, photocatalytic performance, and catalytic reduction activity of the prepared Ag/CN-x samples were investigated. The tests showed that the Ag/CN-8 prepared through by calcination for 8 h exhibited the best photocatalytic degradation efficiency of methyl orange (98.7% within 2 h) and the best catalytic reduction property of 4-nitrophenol (100% within 70 s). Meanwhile, these Ag/CN-x samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectra (DRS), photoluminescence (PL), photocurrent response, and electrochemical impedance spectroscopy (EIS) Nyquist plots. It was found that the Ag/CN-8 prepared through calcination for 8 h had a higher specific surface area, higher dispersibility of silver nanoparticles (Ag NPs), the widest range of visible light response, and the lowest photogenerated electron-hole recombination rate. The results of the trapping experiments indicated that a superoxide radical plays a major role. Moreover, a possible mechanism of photocatalytic degradation in methyl orange and catalytic reduction 4-nitrophenol was proposed.

关键词： Photocatalysis Metal nanoparticles Photocatalysts Physical and chemical processes Catalytic reactions

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Experimental Investigations of Liquid Immersion Cooling for 18650 Lithium-Ion Battery Pack Under Fast Charging Conditions

SSRN

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SSRN 2022年

作者： Li, Yang Bai, Minli Zhou, Zhifu Wu, Wei-Tao Lv, Jizu Gao, Linsong Huang, Heng Li, Yulong 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

In this study, a novel battery thermal management system (BTMS) based on FS49 is proposed and tested for cooling the cylindrical lithium-ion battery (LIB) module under fast charging conditions. Firstly, the temperature response of the battery module under 3 C rate charging with forced air cooling (FAC) and liquid immersion cooling (LIC) is compared. The results indicate that the LIC has excellent heat dissipation performance, and the peak temperature and peak temperature difference of the module are reduced by 19.6 °C and 8.99 °C, respectively, compared with the FAC, while the cooling energy consumption of LIC is only 40.4% of the FAC. It is found that the LIC embraces advantages of efficient cooling and minimizing the temperature non-uniformity in battery pack. Subsequently, the thermal management performance of the proposed LIC is investigated under conventional C rate discharging and different fast charging schemes. Finally, effect of condenser flow rate and cooling water temperature were investigated. This study demonstrates the application prospect of the LIC in the field of LIB fast charging. © 2022, The Authors. All rights reserved.

关键词： Lithium-ion batteries

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Numerical Analysis of the Coupling between Heat Transfer and Deformation in Rotary Air Preheater

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INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2021年第PartA期165卷 120625-120625页

作者： Bu, Yufan Wang, Limin Zhu, Hua Pu, Henglin Wei, Yonggui Che, Defu Xi An Jiao Tong Univ Sch Energy & Power Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Eastern Elect Corp Dongfang Boilers Co Ltd Chengdu 611731 Peoples R China

The rotary air preheater is one of the leading heat exchangers to be employed in steam power plants. However, thermal stress induced deformation of the rotor significantly decreases the efficiency of preheating system. The countercurrent arrangement of hot flue gas and cold air is the direct cause of greater temperature difference across the rotor, which leads to a mushroom deformation, and then serious problems of air leakage and mechanical friction. In this study, a numerical investigation was newly performed by the analysis modules of Fluid flow (FLUENT) and Static Structural through ANSYS Workbench to couple heat transfer and thermal stress deformation in the rotary air preheater. Porous media method along with the local non-equilibrium thermal model was adopted to accurately obtain the temperature distributions of both matrix and gas. Good agreements were yielded by comparing the simulation results and experimental data. The effects of operational and structural parameters, i.e., the temperature difference between the hot and the cold ends, the rotation angle, the height, and the radius on thermal deformation behavior of the entire rotor were investigated in detail. The droopy deformation at the hot and the cold ends increases with the temperature difference and radius, whereas increasing the height of rotor has the opposite influence. With the rotation of matrix, the maximum droopy deformation is located at the entrance of flue gas section and the minimum occurs when reaching the air section. Furthermore, a series of formulas were presented with nonlinear curve fitting to evaluate the deformation amount, which were proved to be of excellent accuracy and can be a better guidance for the seal system of the preheater. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： Heat transfer Non-equilibrium thermal model Thermal stress deformation Temperature distribution Rotary air preheater

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