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Irreversibility Analysis of a Recuperative Heater during Undergoing the flowrate Impulsive Disturbance Transient Processes

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Energy Procedia 2019年 158卷 5311-5316页

作者： Chaoyang Wang Yongliang Zhao Zhu Wang Ming Liu Junjie Yan State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an 710049 China

The recuperative heater is widely used in the industrial production processes, and the irreversibility analysis on the heater during transients is scarce but necessary. Numerical method was adopted to model the recuperative heat exchanger to exhibit its dynamic behaviors during transient processes. The difference between the transient and stationary irreversibility can be called additional irreversibility. In this paper, the dynamic behaviors of the recuperative heater during transients are presented. With these thermal parameters, the irreversibility of a recuperative heater during hot and cold fluid flow rates impulsive disturbance transient processes was calculated and analyzed in detail. The calculation results show that: compared with steady-state corresponding value, the real-time irreversibility rate of the heater during transients is different. The total additional irreversibility values with impulsive disturbance in hot and cold fluid flow rates are obtained separately.

关键词： Recuperative heaters Irreversibility analysis Dynamic modeling Transisent processes

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Tapered optical fiber photocatalysis enhances hydrogen production

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Nano Energy 2025年 142卷

作者： Wenshuo Yao Xueli Yan Feng Liu Shidong Zhao Zhongyuan Li Yi Wang Yitao Si Maochang Liu International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an Shaanxi 710049 P R China School of Chemistry and Chemical Engineering Southeast University Nanjing Jiangsu 211189 P R China Suzhou Academy of Xi’an Jiaotong University Suzhou Jiangsu 215123 P R China

Optical fibers offer a promising platform for photocatalytic reactions owing to their low resistance to light-mass transfer. However, light energy diminishes during propagation, leading to uneven catalyst interaction along the fiber surface. Here, we report a photocatalytic water splitting system using a tapered optical fiber coated with Cd 0.5 Zn 0.5 S as a model photocatalyst. Tapering the fiber intensifies light distribution, primarily directing it from the sides, thereby significantly enhancing light-catalyst interaction. Compared to conventional optical fiber, the tapered fiber leads to an obvious enhancement towards hydrogen production. This work demonstrates the effectiveness of tapered optical fiber photocatalysis, providing a novel proof-of-concept for photocatalytic hydrogen production.

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Single-atom cobalt-incorporating carbon nitride for photocatalytic solar hydrogen conversion: An X-ray spectromicroscopy study

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Journal of Electron Spectroscopy and Related Phenomena 2023年第1期264卷

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

The use of carbon nitride-based materials and light to drive catalytic water splitting has enormous potential for the production of hydrogen. Revealing the processes of molecular conjugation, nucleation, and crystallization in crystalline carbon nitride is expected to enhance the photocatalytic activity through the creation of isotype heterojunctions and active sites. In this work, the addition of cobalt salts in ionothermal synthesis was found to promote the phase transition of heptazine-based crystalline carbon nitride (CCN) to triazine-based poly (triazine imide) (PTI), resulting in the formation of a single-atom cobalt-doped coordinated isotype CCN/PTI heterojunction. The new hybrid orbital modulates the atomic/electronic structure and the band gap of the CCN/PTI heterojunction, and synergistically increases the absorption of visible light, accelerating the separation and transfer of photoexcited electrons and holes. Synchrotron-based X-ray spectroscopy and microscopy are used to identify the origin of the improved performance of the single-atom cobalt-doped CCN/PTI heterojunction in the photocatalytic hydrogen evolution reaction. This work demonstrates that synchrotron X-ray spectroscopy is a promising tool for designing materials aimed at enhancing photocatalytic activity in solar energy conversion applications. © 2023 Elsevier B.V.

关键词： Carbon nitride

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A review on thermohydraulic and mechanical-physical properties of SiC, FeCrAl and Ti 3 SiC 2 for ATF cladding

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Nuclear engineering and Technology 2020年第1期52卷 1-13页

作者： Bowen Qiu Jun Wang Yangbin Deng Mingjun Wang Yingwei Wu S.Z. Qiu Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology Shaanxi Engineering Research Center of Advanced Nuclear Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an City 710049 China University of Wisconsin-Madison Madison WI United States College of Physics and Optoelectronic Engineering Shenzhen University Shenzhen 518060 China

At present, the Department of Energy (DOE) in Unite State are directing the efforts of developing accident tolerant fuel (ATF) technology. As the first barrier of nuclear fuel system, the material selection of fuel rod cladding for ATFs is a basic but very significant issue for the development of this concept. The advanced cladding is attractive for providing much stronger oxidation resistance and better in-pile behavior under sever accident conditions (such as SBO, LOCA) for giving more coping time and, of course, at least an equivalent performance under normal condition. In recent years, many researches on in-plie or out-pile physical properties of some suggested cladding materials have been conducted to solve this material selection problem. Base on published literatures, this paper introduced relevant research backgrounds, objectives, research institutions and their progresses on several main potential claddings include triplex SiC, FeCrAl and MAX phase material Ti3SiC2. The physical properties of these claddings for their application in ATF area are also reviewed in thermohydraulic and mechanical view for better understanding and simulating the behaviors of these new claddings. While most of important data are available from publications, there are still many relevant properties are lacking for the evaluations.

关键词： ATF SiC f /SiC cladding FeCrAl cladding Ti3SiC2 cladding Physical properties

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Polymeric Carbon Nitride for Photocatalytic Overall Water Splitting: Modification Strategies and Recent Advances

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Chinese Journal of Structural Chemistry 2025年

作者： Anna Dai Zhenxiong Huang Li Tian Zheng Zhang Xiangjiu Guan Liejin Guo International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University No. 28 Xianning West Road Xi’an Shaanxi 710049 P. R. China Jiangxi Provincial Key Laboratory of Greenhouse Gas Accounting and Carbon Reduction Institute of Energy Research Jiangxi Academy of Sciences No. 7777 Changdong Avenue Nanchang 330096 P. R. China

Solar-driven photocatalytic overall water splitting (POWS) has emerged as a sustainable pathway for hydrogen production, yet faces intrinsic challenges in developing robust catalysts that balance efficiency, stability, and cost-effectiveness. Polymeric carbon nitride (PCN) represents as a promising metal-free photocatalyst for hydrogen production, due to the merits of unique electronic structure and exceptional thermal stability. Nevertheless, limited by rapid charge recombination and insufficient oxidative capability, little success has been achieved on pristine PCN photocatalyst in POWS. In this context, recent advances have demonstrated multi-dimensional modification strategies for improved POWS performance. Based on the fundamental principles of photocatalysis, this review discusses the advantages and challenges of PCN-based photocatalysts in POWS systems. With critical evaluation on one-step excitation systems and Z-scheme two-step excitation systems, modification strategies including crystallinity engineering, supramolecular precursor design, cocatalyst modulation, and construction of PCN-based heterojunctions and homojunctions were highlighted by introducing representative advances in POWS application over the past five years. Future perspectives for PCN-based photocatalysts are proposed, aiming to provide new insights for the design of advanced photocatalytic system for efficient POWS.

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A bundle CHF mechanism model and its preliminary verification under PWR conditions 18

A bundle CHF mechanism model and its preliminary verificatio...

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18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2019

作者： Liu, Yang Shan, Jianqiang Zhang, Bo Liu, Wei State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University No. 28 Xianning West Road Xi'an Shaanxi Province710049 China Nuclear Power Institute of China State Key Laboratory of System Desgin Technology Chengdu Sichuan Province610213 China

A bundle mechanistic model to predict critical heat flux (CHF) over a pressurized water reactor (PWR) operating range in flow boiling has been proposed based on a concept of the bubble crowding in the wall bubbly layer. The new bundle mechanistic model has the following differences with the original tube model proposed by Weisman & Pei. Firstly,the radial velocity distribution within the bundle was used to derive the radial turbulence intensity factor ib instead of the velocity distribution inside the tube. Secondly, a grid enhancement factor was introduced to quantify the effect of grid on CHF enhancement, based on the measurement experiment of the turbulence intensity factor ib with grid. Thirdly, for the turbulence intensity factor ib, the new model considers the influence of pressure and mass flow rate under two phases, and the original ib only considers the influence of mass flow rate. Finally, the new established bundle CHF mechanism model was verified by comparing with the typical PWR CHF data. © 2019 American Nuclear Society. All rights reserved.

关键词： Heat flux

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Thermodynamic and safety analysis for hydrogen production in a supercritical water gasification system of coal by multi-oxidizers distribution

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Energy 2025年 331卷

作者： Kui Luo Runqiu Dong Xujun Li Zhiyong Peng Libo Lu Jialing Xu Hui Jin Liejin Guo State Key Laboratory of Multiphase Flow in Power Engineering (SKLMF) Xi'an Jiaotong University NO.28 Xianning West Road Xi'an 710049 Shaanxi Province China Dongfang Steam Turbine Co. Ltd. Deyang 618000 China Jiangxi Provincial Key Laboratory of Particle Technology Jiangxi University of Science and Technology Ganzhou 341000 China School of Smart Energy Shanghai Jiao Tong University Shanghai 201100 China

Coal supercritical water gasification (SCWG) for hydrogen production technology is highly prospective due to the clean and efficient treatment process. A single oxidation reactor heating method is usually used in existing work limiting the efficient and stable operation of the system due to high component temperatures. This paper proposed the heat supply strategy of multi-oxidation reactor and heat exchanger layout to improve the system performance for the realization of reasonable matching of material flow and energy flow in each stage of the system. The improved system reduced the maximum temperature of the oxidation reactor from 1550 °C to 850 °C, and the system exergy efficiency and H 2 yield reached 49.30 % and 101 kg/h (at the mass ratio of coal to water of 1:10), respectively. The exergy flow results showed that the improved system exergy loss was concentrated in the oxidation reactor (34.00 %) heat exchanger (28.86 %), cooler (19.07 %), and gasification reactor (9.70 %). Exergy efficiency increased as the mass ratio of coal to water increased to the maximum exergy efficiency of 53.50 %. As the temperature increased from 600 °C to 675 °C, the exergy efficiency decreased from 53.10 % to 48.70 %. System adjustability analysis showed that the system can be stabilized over a 40 %–100 % range of feed fluctuations. This work may provide an optimization strategy for efficient operation and dynamic safety regulation of H 2 production by SCWG technology.

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Flocculation of suspended cohesive particles in homogeneous isotropic turbulence

arXiv

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arXiv 2021年

作者： Zhao, K. Pomes, F. Vowinckel, Bernhard Hsu, T.-J. Bai, B. Meiburg, E. Department of Mechanical Engineering UC Santa Barbara Santa BarbaraCA93106 United States State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Leichtweiß-Institute for Hydraulic Engineering and Water Resources Technische Universität Braunschweig Braunschweig38106 Germany Center for Applied Coastal Research Department of Civil & Environmental Engineering University of Delaware NewarkDE19716 United States

We investigate the dynamics of cohesive particles in homogeneous isotropic turbulence, based on one-way coupled simulations that include Stokes drag, lubrication, cohesive and direct contact forces. We observe a transient flocculation phase characterized by a growing average floc size, followed by a statistically steady equilibrium phase. We analyze the temporal evolution of floc size and shape due to aggregation, breakage, and deformation. Larger turbulent shear and weaker cohesive forces yield elongated flocs that are smaller in size. Flocculation proceeds most rapidly when the fluid and particle time scales are balanced and a suitably defined Stokes number is O(1). During the transient stage, cohesive forces of intermediate strength produce flocs of the largest size, as they are strong enough to cause aggregation, but not so strong as to pull the floc into a compact shape. Small Stokes numbers and weak turbulence delay the onset of the equilibrium stage. During equilibrium, stronger cohesive forces yield flocs of larger size. The equilibrium floc size distribution exhibits a preferred size that depends on the cohesive number. We observe that flocs are generally elongated by turbulent stresses before breakage. Flocs of size close to the Kolmogorov length scale preferentially align themselves with the intermediate strain direction and the vorticity vector. Flocs of smaller size tend to align themselves with the extensional strain direction. More generally, flocs are aligned with the strongest Lagrangian stretching direction. The Kolmogorov scale is seen to limit floc growth. We propose a new flocculation model with a variable fractal dimension that predicts the temporal evolution of the floc size and shape. © 2021, CC BY.

关键词： Flocculation

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Correction to: Modification of a first‑generation solid oxide fuel cell cathode with Co3O4 nanocubes having selectively exposed crystal planes

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Materials for Renewable and Sustainable Energy 2022年第3期11卷 299-299页

作者： Xu, Xi Wang, Chao Fronzi, Marco Liu, Xuehua Bi, Lei Institute of Materials for Energy and Environment College of Materials Science and Engineering Qingdao University Qingdao China State Key Laboratory of Multiphase Flow in Power Engineering International Research Centre for Renewable Energy Xi’an Jiaotong University Xi’an China

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Two-dimensional self-adapting fast Fourier transform algorithm for nanoparticle sizing by ultrafast image-based dynamic light scattering

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Particuology 2018年第6期16卷 74-84页

作者： Dechuan Zhang Xiaoshu Cai Wu Zhou Institute of Particle and Two-Phase Flow Measurement University of Shanghai for Sdence and TechnologyShanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering (University of Shanghai for Sdence and Technology)Shanghai 200093China

In nanoparticle sizing using the ultrafast image-based dynamic light scattering (UIDLS)method,larger impurities and dark noise from the complementary metal-oxide-semiconductor (CMOS)detector affect measurement *** solve this problem,a two-dimensional self-adapting fast Fourier transform (2D-SAFFT)algorithm is proposed for *** light scattering images of nanoparticles are processed using 2D fast Fourier transforms,and a high-frequency threshold and a low-frequency threshold are then set using the self-adapting algorithm to eliminate the effects of the dark noise of the CMOS detector and the *** signals caused by the dark noise of the CMOS detector and the impurities are cut off using the high-frequency threshold and the low-frequency *** signals without the high- and low-frequency components are then processed again using an inverse Fourier transform to obtain new images without the dark noise and impurities *** mean diameters of the measured nanoparticles can be obtained from images obtained using *** standard latex nanoparticles (46,100, 203,508,994nm)and commercial nanoparticles (antimony-doped tin oxide,indium tin oxide,TWEEN- 80,nano-Fe,and nano-Al2O3)were measured using this new *** show that 2D-SAFFT can effectively eliminate the effects of dark noise from the CMOS detector and the impurities.

关键词： Dynamic light scattering Nanoparticle size Fast Fourier transform algorithm Spectrum segmentation

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