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Manipulating metal-oxygen local atomic structures in singlejunctional p-Si/WO_(3) photocathodes for efficient solar hydrogen generation

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Nano Research 2021年第7期14卷 2285-2293页

作者： Wu Zhou Chung-Li Dong Yiqing Wang Yu-Cheng Huang Lingyun He Han-Wei Chang Shaohua Shen International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi’an Jiaotong UniversityShaanxi 710049China Department of Physics Tamkang UniversityTamsui 25137TaiwanChina

Self-passivation in aqueous solution and sluggish surface reaction kinetics significantly limit the photoelectrochemical(PEC)performances of silicon-based ***,a WO_(3) thin layer is deposited on the p-Si substrate by pulsed laser deposition(PLD),acting as a photocathode for PEC hydrogen *** to bare p-Si,the single-junctional p-Si/WO_(3) photoelectrodes exhibit excellent and stable PEC performances with significantly increased cathodic photocurrent density and exceptional anodic shift in onset potential for water *** is revealed that the WO_(3) layer could reduce the charge transfer resistance across the electrode/electrolyte interface by eliminating the effect of Fermi level pinning on the surface of *** importantly,by varying the oxygen pressures during PLD,the collaborative modulation of W–O bond covalency and WO6 octahedral structure symmetry contributes to the promoted charge carrier transport and ***,a large band bending at the p-Si/WO_(3) junction,induced by the optimized O vacancy contents in WO_(3),could provide a photovoltage as high as~500 mV to efficiently drive charge transfer to overcome the water reduction ***,by manipulating W–O local atomic structures in the deposited WO_(3) layer,a great improvement in PEC performance could be achieved over the singlejunctional p-Si/WO_(3) photocathodes for solar hydrogen generation.

关键词： silicon local atomic structure water splitting photocathodes hydrogen generation

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Enhancing thin film boiling heat transfer through electric field and surface Macro-Structure Synergy: Insights from bubble dynamics modulation

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International Journal of Heat and Mass Transfer 2025年 249卷

作者： He, Changqiu Tian, Jiameng Chen, Yiqi Zhu, Yuchen Liu, Xin Wang, Hai Wang, Zhentao Cai, Benan Wang, Changqing Wang, Junfeng Zhou, Zhifu Chen, Bin School of Energy and Power Engineering Jiangsu University Zhenjiang212013 China School of Energy and Power Engineering Chongqing University Chongqing 400044 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Laboratory of Thermo-fluid Science and Nuclear Engineering School of Energy and Power Engineering Northeast Electric Power University Jilin 132012 China National Key Laboratory of Marine Engine Science and Technology Shanghai 201108 China

Improving boiling heat transfer in thin liquid films by employing external electrical fields and macro-structured surfaces presents promising for tackling the growing difficulties related to high-heat-flux thermal management in electronic devices. In this study, six distinct macro-structured surfaces are designed and fabricated to gain insight into how liquid film thickness, structural parameters, and applied voltage affect the efficiency of boiling heat transfer with ethanol as the coolant. High-speed imaging and precise heat transfer measurements are employed to characterize the boiling performance, providing insights into the underlying fundamentals driving the observed enhancements. Results reveal that applying a 4-kV voltage increases departure frequency of bubble by 86 % and a 28 % reduction in diameter, causing a 20 % improvement in critical heat flux (CHF). CHF is positively correlated with liquid film thickness and pin height, but negatively with pin spacing, achieving a 139 % increase under optimal conditions. Liquid film thickness was found to have the most significant impact on CHF, followed by pin spacing and applied voltage. By simplifying the void fraction equation, a new CHF correlation is proposed that introduces a dimensionless characteristic length, representing the relative effects between bubble size and film thickness, while accounting for the synergy between the electric field and surface macro-structure. © 2025 Elsevier Ltd

关键词： Electric heating

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Rapid Methane Hydrate Formation in Open-Cell Copper Foam 4th

Rapid Methane Hydrate Formation in Open-Cell Copper Foam

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4th International Technical Symposium on Deepwater Oil and Gas engineering and 3rd International Youth Forum on Gas Hydrate, DWOG-Hyd 2021

作者： Wang, Jiajie Yang, Liang Shao, Xinxin Zhang, Hao 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 University of Shanghai for Science and Technology Shanghai200093 China

ISBN: (纸本)9789811909597

Rapid methane hydrate formation with high gas storage capacity is very important for the application of natural gas hydrates technology. Three pieces of open-cell copper foam (CF) with different pore densities (or pores per inch, PPI) herein were immersed in sodium dodecyl sulfate (SDS) solution for enhancing methane storage in solid hydrate. The promotion effects of CF on the methane hydrate formation in the metal-embedded systems were investigated via an unstirred tank reactor. The results demonstrated that the surface of CF skeleton is covered with abundant micro holes and micro grooves, which can provide many metal nuclei for gas-water crystallization. The nest-like metal skeleton acts as crisscross "highway" for the crystallization heat transfer. Methane hydrate was quickly formed in the SDS/CF systems, but CF with the pore densities of 5 and 30 PPI was not favorable for conversion of more water to hydrate. Compared with these two composite systems, the SDS solution with the 15 PPI CF were able to store more methane at a faster formation rate. A theoretical model based highly porous two-phase systems was used to predict the effective thermal conductivity (ETC) of the metal foam filled with hydrate. It was found that the ETC of the hydrate/CF composite was significantly enhanced by employing CF matrix, and the low pore density CF had a more positive impact on improving the ETC of the composite. Further comparative experiments conducted at various pressures indicated that the solutions with 15 PPI CF exhibited higher methane storage capacities and larger hydration rates than the simple SDS solution, especially at the low pressure. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

关键词： Sodium dodecyl sulfate

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Effect of Blade Gap Angle on Performance of Gas–Liquid multiphase Pump

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International Journal of Fluid Machinery and Systems 2024年第3期17卷 178-191页

作者： Li, Rennian Xing, Yifan Han, Wei Zhang, Wanyu Dang, Shujuan Qiang, Yan College of Energy and Power Engineering Lanzhou University of Technology Lanzhou730050 China Key Laboratory of Ministry of Education Special Pumps Valves and Flow Control Systems Lanzhou730050 China West Pipeline Company National Petroleum and Natural Gas Pipeline Network Group Co. Ltd. Xinjiang830013 China

This study investigates the impact of blade gap angle on spiral axial flow gas–liquid multiphase pump performance. Using five numerical models and the shear stress transport k-omega (SST k-ω) turbulence model, we incorporated gas compressibility to analyze the influence of blade gap angle on pump performance. Results revealed alterations in the gap angle affected gas–liquid slip velocity distribution, turbulence eddy frequency within the impeller region, and the distribution of gas separation areas at the gap inlet and outlet. Increasing the gap deflection angle inhibited gas flow separation at the hub-side inlet while simultaneously enlarging separation area at the outlet of the gap, with the optimal gap angles enhancing flow separation in a helicoaxial gas–liquid multiphase pump. © 2024, Turbomachinery Society of Japan. All rights reserved.

关键词： Turbulence models

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Novel Catalyst Coatings on Gas Diffusion Layers for Improved Proton Exchange Membrane Water Electrolysis: A Microscopic Analysis of D-Orbital Electron Interactions in Co0.75Ru0.21Ir0.04O0.9

SSRN

引用

SSRN 2024年

作者： Wang, Weiding Wang, Hao Zhang, Yan Yang, Suyi Wang, Baoyuan Dong, Wenxuan Li, Lubing Zhang, Lei Su, Jinzhan Guo, Liejin International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering School of Energy & Power Engineering Xi’an Jiaotong University Xi’an710049 China

Proton exchange membrane water electrolysis (PEMWE) has emerged as a reliable water splitting technology in recent years. The oxygen evolution reaction (OER) at the anode, is the rate-determining step in water electrolysis, and therefore, the kinetic and mass transfer performance of the oxygen evolution reaction should be further studied. Efficient electron and water transfer between the catalyst layer (CL) and gas diffusion layer (GDL) is crucial for optimizing PEMWE performance. In this work, Ru-core modified materials were successfully synthesized via a hydrothermal method and then spray-coated onto the surface of the gas diffusion layer. Physical and electrochemical characterization showed that 0.10 mg cm-2 was the optimal dosage of the coating. The single cell with this optimal coating exhibited a well-promoted and outstanding performance that a cell voltage of 1.71 V@1 A cm-2 and an overpotential of 222 mV@10 mA cm-2. This enhancement was primarily attributed to the improved ohmic and mass transfer properties. Specifically, the promotion of kinetic and mass transfer performance was due to the attraction of the empty d-orbitals of Ru, Co, and Ir, which enhanced electron transmission between the catalyst layer (CL) and gas diffusion layer. Physical analysis revealed that the reductive gaseous products caused Co (Ⅲ) to transform to Co (Ⅱ) and the formation of Co3O4 and RuO2 was well-protected by the Co (II)-rich Co3O4 phase due to its reductivity nature. Additionally, the effusion of gaseous products from the solid phase accelerated pore formation, thereby increasing the specific surface area of the material. © 2024, The Authors. All rights reserved.

关键词： Electrolysis

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A Numerical Study on Convective Condensation of Flue Gas in Tubular Heat Exchangers

SSRN

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SSRN 2023年

作者： Yang, Kaixuan Yang, Jiahui Da, Yaodong Han, Lei Deng, Lei Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China

Accurate calculation of heat transfer process in condensing heat exchanger plays a crucial role in the waste heat recovery. In this study, the convective-condensation heat transfer process in a condensing heat exchanger with five small heat exchangers is analyzed through utilizing a new numerical simulation model. The method that loads the latent heat of vaporization as heat generation rate is adopted. Under the two working conditions in this study, the deviations of outlet temperature between numerical and experimental results are 1.3 and 2.2 K, respectively, while the deviations of total condensate water flow are 8.5% and 5.5%, respectively. Under the drier working condition, the average temperature reduction per row of tubes in the first small heat exchanger where is no condensation is significantly higher than that in the third small heat exchanger where vapor starts to condense, 5.8 and 2.6 K, separately. It indicates that the release of latent heat of vaporization slows down the cooling rate of the flue gas. In the small heat exchanger where vapor starts to condense, the amount of condensate water on the wall of each row of tubes increases first and then decreases slowly along the flow direction of flue gas. © 2023, The Authors. All rights reserved.

关键词： Heat exchangers

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Reduction kinetics of SrFeO_(3−δ)/CaO∙MnO nanocomposite as effective oxygen carrier for chemical looping partial oxidation of methane

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Frontiers of Chemical Science and engineering 2022年第12期16卷 1726-1734页

作者： Xinhe Wang Liuqing Yang Xiaolin Ji Yunfei Gao Fanxing Li Junshe Zhang Jinjia Wei State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China School of Chemical Engineering and Technology Xi’an Jiaotong UniversityXi’an 710049China Institute of Clean Coal Technology East China University of Science and TechnologyShanghai 200237China Department of Chemical and Biomolecular Engineering North Carolina State UniversityRaleighNC 27695USA

Chemical looping reforming of methane is a novel and effective approach to convert methane to syngas,in which oxygen transfer is achieved by a redox *** lots of efforts have been made to develop high-performance redox materials,a few studies have focused on the redox *** this work,the kinetics of SrFeO_(3−δ)–CaO∙MnO nanocomposite reduction by methane was investigated both on a thermo-gravimetric analyzer and in a packed-bed *** the methane reduction,combustion occurs before the partial oxidation and there exists a transition between *** weight loss due to combustion increases,but the transition region becomes less inconspicuous as the reduction temperature *** weight loss associated with the partial oxidation is much larger than that with *** rate of weight loss related to the partial oxidation is well fitted by the Avrami–Erofeyev equation with n=3(A3 model)with an activation energy of 59.8 kJ∙mol^(‒1).The rate law for the partial oxidation includes a solid conversion term whose expression is given by the A3 model and a methane pressure-dependent term represented by a power *** partial oxidation is half order with respect to methane *** proposed rate law could well predict the reduction kinetics;thus,it may be used to design and/or analyze a chemical looping reforming reactor.

关键词： chemical looping reforming SrFeO_(3−δ) CaO·MnO nanocomposite reduction kinetics Avrami–Erofeyev model pressure-dependent term

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Experimental Investigation of the Photovoltaic Thermal (Pvt) Integrated with Ground Heat Exchanger (Ghe) Using Volcanic Tuff Stones

SSRN

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SSRN 2024年

作者： Alqatamin, Ahmad Jinzhan, S.U. International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China

This study investigates the combination of photovoltaic thermal (PVT) and ground heat exchanger (GHE) using volcanic tuff stones as a heat storage material if the combination of PVT and GHE technologies provides the potential for energy generation increased efficiency and performance. Volcanic tuff stones known for their high thermal conductivity and heat retention, act as an effective means of heat exchange in the system. The objective of the study is to investigate the electrical, thermal performance and efficiency of this integrated system. Where the ground heat exchanger comprises a single hole filled with volcanic tuff stones arranged strategically, featuring gaps between them to facilitate heat exchange. The hole dimensions are specified as 2.5 meters in length, 2 meters in width, and 3 meters in depth. A fan is situated at the exit square duct (400*400 mm) to extract ambient air. Experimental data was collected from the PVT-GHE system to evaluate its efficiency in harnessing solar energy and providing space heating or other heating applications and compared it with a traditional PVT system. The results show that integrating GHE into PVT systems dramatically decreases solar cell temperature and improves electrical efficiency. A PVT system with GHE had the maximum electrical efficiency at 17.99%, compared to 17.52% in a PVT system without GHE. In addition, the greatest possible electrical power in a PVT system with GHE was 65 W, but in a PVT system without GHE, it was 61W. Also, the outlet air temperature from GHE was consistently higher than the ambient temperature throughout the days of the experiment, with an average difference of about 10 ºC. © 2024, The Authors. All rights reserved.

关键词： Solar energy

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A framework of the transport model for high-order eddy viscosity tensor in two-dimensional turbulent flow

arXiv

引用

arXiv 2023年

作者： Zhou, Xingguang Zhang, Dalin Tian, Wenxi Su, Guanghui Qiu, Suizheng State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Shaanxi Xi'An710049 China

Motivated by the concept of eddy viscosity tensor in improved Boussinesq hypothesis, a transport model of high-order eddy viscosity tensor in 2D-3C turbulence structure is derived from the second-order moment model by tensorial analysis. Compared with the previous high-order eddy viscosity tensor mathematical model [1-3] for turbulent flow under special operating conditions, we have obtained a general high-order eddy viscosity tensor transport model, which can show the anisotropy and transport characteristics of Reynolds stress. The transport equation of a high-order eddy viscosity tensor includes the transient term, convection term, production term, diffusion term, positive-definite source term, and dissipation term. In addition, when the components of high-order eddy viscosity tensor are positive or negative, the physical meaning of the source terms is also discussed. Two numerical simulation cases are also interpreted to verify the model. First, we apply the transport model of high-order eddy viscosity to the numerical calculation analysis of two-dimensional straight channel turbulent flow, and the results show that this model can effectively characterize the anisotropy of Reynolds stress. With a combination of analytical and numerical methods, we analyze the flow fields and the components of high-order eddy viscosity tensor to investigate the evolution law of high-order eddy viscosity tensor. The characteristics of the principal components and tensorial invariance of dimensionless Reynolds stress anisotropy tensor of two-dimensional straight channel turbulent flow also have been investigated with the Lumley triangle [4,5]. The results show that this model has a good agreement with the DNS calculation results for the characteristics of dimensionless Reynolds stress anisotropy tensor. Then, we make the numerical investigation for a two-dimensional planar asymmetric diffuser and compare the results with the experiments of Obi *** [6]. The transport model can reso

关键词： Tensors

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Study on the thermal and geometrical parameters of helical coil once-through steam generator system

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International Journal of Advanced Nuclear Reactor Design and Technology 2021年 3卷 80-96页

作者： Yao, Hao Chen, Guo Lu, Kailin Liao, Haoyu Wu, Yingwei Tian, Wenxi Su, Guanghui Qiu, Suizheng School of Nuclear Science and Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Nuclear Power Institute of China Chengdu610226 China

Due to the special structure, helical coil once-through steam generators (HCOTSGs) can withstand greater thermal expansion stress, have a larger heat exchange area, and cause the secondary flow phenomenon to improve the heat transfer capacity. Thus, it is inevitable to further study the thermal-hydraulic characteristics of the HCOTSG, a vital component of reactors. The optimal physical models were selected for different heat transfer areas by detailed investigation and comparison, to adopt in the TACS, a self-developed thermal-hydraulic analysis code that is accurate and widely-used in HCOTSG simulation. After verification with experiments of Santini, taking the IRIS reactor as the object, the TACS was employed to briefly study the thermal-hydraulic performances of the HCOTSG system at first, and then discuss the influences of thermal and geometric parameters on the HCOTSG. The analysis results showed that: the variation of the primary flow rate greatly affects the heat transfer coefficient of the primary side, while the maximum value of the heat transfer coefficient of the secondary side only changes drastically with the secondary flow rate;when the primary side flow drops to 70%, superheated steam is not generated on the secondary side;when the secondary mass flow rate decreases to a certain extent, the steam superheat degree increases by a small amplitude;the primary side inlet temperature has a little influence on the primary temperature difference, but significant influence on the two-phase zone length of the secondary side;the secondary inlet temperature has very little influence on the HCOTSG system;the inner diameter and the outer diameter of helical tubes have obvious influences, while the helical diameter has not. © 2021 Xi'an Jiaotong University

关键词： Heat transfer coefficients

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