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Influence of special water properties variation on the heat transfer of supercritical water flow around a sphere

CHEMICAL engineering SCIENCE 2020年 222卷

作者： Wu, Zhenqun Ren, Yifei Ou, Guobiao Jin, Hui Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

Supercritical water gasification (SCWG) technology shows a promising future due to its high efficiency and low emissions. Influenced by special water properties variation near the pseudocritical point, well-established heat transfer correlations are ill-suited for SCWG reactor design. To solve the problems caused by heat transfer, particle-resolved simulations were conducted to study the heat transfer characteristics of supercritical water (SCW) flow around a spherical particle, which served as a basic reacting unit. Through varying the temperature difference between the inflow and particle surface, heat transfer characteristics with different water properties variation tendencies were studied. Detailed analyses of the velocity and temperature boundary layers, and flow field around the particle were also presented to gain greater understanding. Furthermore, heat transfer characteristics under different pressures were studied. Based on the simulated results, a new correlation applicable for SCW flow around a sphere for the Reynolds number range 10–200 was obtained.

关键词： Supercritical water Special properties variation Sphere Heat transfer

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Special Section Guest Editorial: Advanced Materials and Devices for Solar Driven Liquid Fuel and Hydrogen Production

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JOURNAL OF PHOTONICS FOR ENERGY 2020年第2期10卷

作者： Guo, Liejin Burda, Clemens Liu, Maochang Xi An Jiao Tong Univ Int Res Ctr Renewable Energy State Key Lab Multiphase Flow Power Engn Xian Peoples R China Case Western Reserve Univ Dept Chem Ctr Chem Dynam & Nanomat Res Cleveland OH 44106 USA

Guest editors provide an introduction to the special section on Advanced Materials and Devices for Solar Driven Liquid Fuel and Hydrogen Production.

关键词： Solar energy Liquids Hydrogen production Renewable energy Nanomaterials Thermal engineering Carbon Chemistry Physics Industrial chemicals

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Defective ceria created by oxy-hydrogen flame and its influences on Pt dispersion, Pt-ceria interaction and catalytic hydrogenation

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MOLECULAR CATALYSIS 2023年 551卷

作者： Kamali, Ali Zhang, Yuan Liu, Zixiao Schulman, Emily Almafrachi, Mohammed Zhang, Sheng Wang, Tong Gonzalez-Lopez, Lorelis Zhao, Xinpeng Zhang, Wenfei Zhou, Qulan Al-Sheikhly, Mohamad Hu, Liangbing Liu, Dongxia Univ Maryland Dept Chem & Biomol Engn College Pk MD 20742 USA Univ Delaware Dept Chem & Biomol Engn Delaware DE 19716 USA CUNY Adv Sci Res Ctr Grad Ctr New York NY 10031 USA Univ Maryland Mat Sci & Engn Dept College Pk MD 20742 USA Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

We employed an oxy-hydrogen flame to create defective ceria and studied the consequent changes in the physiochemical properties of ceria and ceria-supported platinum (Pt) catalysts. The defective ceria is more reduced and has greater redox capabilities than the pristine sample. The defective ceria supported Pt catalysts have stronger metal-support interactions that lead to higher Pt dispersion and chemoselectivity in 3-nitrostyrene hydrogenation compared to ceria-supported platinum catalysts. The chemoselectivity increases and then decreases with decrease in metal loadings in defective ceria supported Pt catalysts, while it monotonically increases with decreasing metal loadings in ceria-supported catalysts. The diminishing chemoselectivity of defective ceria supported catalysts can be attributed to the more reduced nature of the defective ceria that leads to metal nanoclusters with less positive charge, disfavoring adsorption of the negatively charged nitro-groups in 3-nitro-styrene in the reaction. Such effect is not obvious in the defective ceria supported catalysts with higher Pt loadings (i.e., larger Pt particle sizes).

关键词： Cerium oxide Defects Oxygen vacancy Pt/ceria catalyst 3-nitrostyrene hydrogenation Oxy-hydrogen flame treatment

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Thermal error controlling for the spindle in a precision boring machine with external cooling across coated joints

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PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART C-JOURNAL OF MECHANICAL engineering SCIENCE 2020年第2期234卷 658-675页

作者： Lei, Mohan Jiang, Gedong Zhao, Liang Wang, Jinshi Li, Ben Q. Xia, Ping Yang, Jun Mei, Xuesong Xi An Jiao Tong Univ State Key Lab Mfg Syst Engn Xian Shaanxi Peoples R China Huazhong Univ Sci & Technol State Key Lab Digital Mfg Equipment & Technol Wuhan Hubei Peoples R China Xi An Jiao Tong Univ Shaanxi Key Lab Intelligent Robots Xian Shaanxi Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian Shaanxi Peoples R China Univ Michigan Dept Mech Engn Coll Engn & Comp Sci Ann Arbor MI 48109 USA

Spindles in precision boring machines usually operate without internal cooling, and thermal error in such spindles is nonnegligible and can severely affect the end-processing quality of the machines. This study aims to investigate the effects that external cooling exerts on the thermal behavior of such spindles. A helical tube cooler is taken for external cooling. An analytical thermal resistance model for the grease-coated cooler-housing joint surface, which considers the pressured cambered-flat contact pair and rough metal surface-grease contact, is presented and validated, and a numerical thermal-fluid-solid coupling model for the cooler-spindle system is then established. An evaluation method is put forward to obtain the stability of the thermal error, which determines the boring processing accuracy and thermal equilibrium time, from experimental data. Then, the external cooling was optimally designed based on the simulation results from the numerical model. Experiments show that the designed cooler reduced the thermal equilibrium time by 47.13% and the maximum thermal error by 81.7%, and the proposed model can accurately predict the cooling effect on the spindle thermal behavior. This study not only provides a thermal error control method for the spindle but is expected to advance the theoretical basis of cooling design for complex electromechanical systems.

关键词： Precision boring machine helical tube thermal error stabilization thermal equilibrium grease-coated joint

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Development of mechanistic cladding rupture model for integrated severe accident code ISAA. Part II: DVI line small-break LOCA in CAP1400

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ANNALS OF NUCLEAR ENERGY 2021年 164卷

作者： Gao, Pengcheng Zhang, Bin Li, Jishen Tang, Shaowei Shan, Jianqiang Xi An Jiao Tong Univ Sch Nucl Sci & Technol Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

Cladding ballooning and rupture are the important phenomena at the early stage of a severe accident (SA). For example, the SA caused by the loss of coolant accident (LOCA), the decrease in primary loop pressure and the increase in core temperature will lead to the cladding ballooning and rupture. The clad-ding deformation affects the flow distribution and causes local flow blockage. Meanwhile, water vapor will enter the fuel gap from the rupture, thereby increasing the surface area of cladding that is oxidized by the steam. At present, the widely used integrated severe accident analysis codes cannot analyze fuel rods thermal-mechanical behavior at the early SA stage, and the judgment of cladding rupture is only based on simple parameter model. This paper integrates the developed FRTMB (core Fuel Rod Thermal-Mechanical Behavior analysis module) module into the integrated severe accident analysis code ISAA, so that the coupled system ISAA-FRTMB can analyze fuel rods thermal-mechanical behavior and judge cladding rupture. Part I introduces the need of developing the FRTMB module, verification of the module, and how the module interactively works in the severe accident analysis code. And evaluates the steady-state fuel rods thermal-mechanical behavior at different enrichment areas of the CAP1400 reactor. Part II focuses on analyzing fuel rods behavior during a hypothetical DVI Line (Direct Vessel Injection line) small break-out accident (break diameter d = 4 in.) of the CAP1400, and predicts the clad-ding rupture time and the corresponding failure temperature. Due to failure of components of the emer-gency core cooling system and assumed unavailability of several preventive and mitigative accident management measures (AMM), the accident develops into a severe accident scenario with core melt and reactor pressure vessel failure. The mechanical analysis results show the top of the fuel rod is the first to rupture, rather than the peak node. The primary factor affecting th

关键词： ISAA-FRTMB SBLOCA Severe accident Fuel behavior Cladding rupture CAP1400 reactor

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Experimental investigation on the condensation regime and pressure oscillation characteristics of vertical upward steam jet condensation with low mass flux

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EXPERIMENTAL THERMAL AND FLUID SCIENCE 2020年 111卷

作者： Yang, Qingchuan Qiu, Binbin Chen, Weixiong Chong, Daotong Liu, Jiping Yan, Junjie Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

An experimental study was conducted to investigate the condensation regime and pressure oscillation characteristics of vertical upward steam jet condensation with low mass flux. Steam mass flux and water temperature were 8.34-16.71 kg/(m(2).s) and 40-85 degrees C, respectively. Steam bubble behavior, pressure oscillation amplitude and frequency were recorded and analyzed. Four typical regimes were found, namely, chugging, detached oscillatory, detached cracked and secondary bubble impinged regimes. A bubble condensation region map was developed by considering the effects of steam mass flux and water temperature. The average amplitude of pressure oscillation initially increased, and then decreased as water temperature increased. It reached its maximum value when water temperature was approximately 60-65 degrees C, which was the transition temperature range from the chugging regime to the detached oscillatory regime. Meanwhile, the frequency of pressure oscillation was within the range of 12-28 Hz. These values were higher than those for a vertical downward steam jet with the same steam mass flux and water temperature. A dimensionless correlation was obtained to predict the Strouhal number of pressure oscillation frequency. The predicted values corresponded well with the experimental data. The deviation was within the range of -9.12% to + 8.30%.

关键词： Direct contact condensation Pressure oscillation Condensation regime Bubble condensation

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Redox-inactive metal single-site molecular complexes: a new generation of electrocatalysts for oxygen evolution?

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CATALYSIS SCIENCE & TECHNOLOGY 2021年第19期11卷 6411-6424页

作者： Benko, Timea Lukacs, David Frey, Krisztina Nemeth, Miklos Moricz, Marta M. Liu, Dongyu Kovats, Eva May, Nora V. Vayssieres, Lionel Li, Mingtao Pap, Jozsef S. Ctr Energy Res Inst Energy Secur & Environm Safety Surface Chem & Catalysis Dept Konkoly Thege St 29-33 H-1121 Budapest Hungary Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn MFPE Int Res Ctr Renewable Energy IRCRE Xian 710049 Shaanxi Peoples R China Wigner Res Ctr Phys Inst Solid State Phys & Opt POB 49 H-1525 Budapest Hungary Res Ctr Nat Sci Ctr Struct Sci Magyar Tudosok Korutja 2 H-1117 Budapest Hungary

A molecular pre-catalyst complex, [Cu-II(indH)(OClO3)(NCCH3)](ClO4)center dot CH3CN (1 center dot CH3CN) with the 3N pincer ligand 1,3-bis(2 '-pyridyl)iminoisoindoline (indH) was immobilized on indium tin oxide (ITO) transparent conducting substrate to generate O-2 electrocatalytically for over 20 hours at pH 10 in a carbonated buffer, reaching a turnover of 139 with no signs of CuOx/Cu(OH)(2) formation at the surface. Further electrolysis experiments revealed that the catalyst was present in the aqueous phase, despite the poor initial solubility of the pre-catalyst (1). In order to identify the actual form responsible for this important catalytic reaction, the aquo complex [Cu-II(ind)(OClO3)(OH2)]center dot CH3OH (2 center dot CH3OH) was structurally characterized. Spectroscopic investigations of a solid isolated from the buffer used in the electrolysis reaction and solution equilibrium studies using 2 indicated that the [Cu-II(ind)(OH)] form occurs at pH 10. Electron paramagnetic resonance (EPR) spectroscopy and DFT calculations confirmed a distorted {3N,O}(eq) coordination plane in solution, as found in 2. The buffer (i.e. bicarbonate/carbonate) may affect reactivity in two ways: as an external base facilitating the proton-coupled electron transfer steps;and/or displacing the inner-sphere solvent molecules from the favourable quasi-equatorial position, thus inhibiting the catalysis. Structural features of a tri-nuclear cluster [Cu-3(II)(ind)(3)(mu(3)-CO3)(CH3OH)(OClO3)] (3) isolated under basic conditions confirmed that beside acting as an external base, the inhibiting effect of carbonate anions may also play a role. In acetonitrile-water solutions, where both 1 and 2 exhibit reasonable solubility, experimental findings supported by DFT calculations suggest that it is the ind(-) ligand which is being oxidized while the cupric ion remains redox-inactive which is very unusual yet of great significance for the creation of a new generation of low-cost Cu-based water

关键词： Solubility

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Nitrogen-Doped Hierarchical Porous Carbon-Promoted Adsorption of Anthraquinone for Long-Life Organic Batteries

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ACS APPLIED MATERIALS & INTERFACES 2020年第31期12卷 34910-34918页

作者： Zhu, Tianxiang Liu, Dongyu Shi, Lei Lu, Shiyao Gao, Yiyang Zhang, Dongyang Mao, Heng Sun, Zehui Lao, Cheng-Yen Li, Mingtao Xi, Kai Ding, Shujiang Xi An Jiao Tong Univ Int Res Ctr Renewable Energy State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ MOE Key Lab Nonequilibrium Synth & Modulat Conden Xian Key Lab Sustainable Energy Mat Chem Dept Appl ChemSch ChemState Key Lab Elect Insul Xian 710049 Shaanxi Peoples R China Univ Cambridge Dept Mat Sci & Met Cambridge CB3 0FS England

Organic quinone molecules are attractive electrochemical energy storage devices because of their high abundance, multielectron reactions, and structural diversity compared with transition metal-oxide electrode materials. However, they have problems like poor cycle stability and low rate performance on account of the inherent low conductivity and high solubility in the electrolyte. Solving these two key problems at the same time can be challenging. Herein, we demonstrate that using a nitrogen-doped hierarchical porous carbon (NC) with mixed microporous/low-range mesoporous can greatly alleviate the shuttle effect caused by the dissolution of organic molecules in the electrolyte through physical binding and chemisorption, thereby improving the electrochemical performances. Lithium-ion batteries based on the anthraquinone (A electrode exhibit dramatic capacity decay (5.7% capacity retention at 0.2 C after 1000 cycles) and poor rate performance (14.2 mA h g(-1) at 2 C). However, the lithium-ion battery based on the NC@AQ cathode shows excellent cycle stability (60.5% capacity retention at 0.2 C after 1000 cycles, 82.8% capacity retention at 0.5 C after 1000 cycles), superior rate capability (152.9 mA h g(-1) at 2 C), and outstanding energy efficiency (98% at 0.2 C). Our work offers a new approach to realize the next-generation organic batteries for long life and high rate performance.

关键词： organic cathode ultralong cycles lithium-ion batteries hierarchical porous nitrogen-doped carbon chemisorption

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Techno-economic analysis of a novel hybrid heat pump system to recover waste heat and condensate from the low-temperature boiler exhaust gas

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INTERNATIONAL JOURNAL OF ENERGY RESEARCH 2020年第5期44卷 3821-3838页

作者： Jamil, Shah Rukh Wang, Limin Che, Defu Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Sch Energy & Power Engn Xian 710049 Peoples R China

This paper is based on the proposal of a new waste heat recovery (WHR) system, which can be utilized to heat the boiler return water, boiler supply air, and building heating air. The system is the combination of an indirect contact condensing unit (IDCCU), a mechanical compression heat pump, and two air preheaters. The system is modeled on the basis of mass and energy balance and then thermodynamically analyzed. Improved performance results were obtained in the form of an increase in the boiler's energy efficiency of about 10.47%, with 4.87% increase in exergy efficiency. The coefficient of performance (COP) of the heat pump was increased from 1.23 to 1.45 by the addition of an air heater in the conventional heat pump. The exergy destruction in each component is calculated. Sensitivity analysis was performed to check the influence of different operating parameters on the performance of the WHR system and boiler. It can be observed from the results that for a specific refrigerant temperature and a calculated amount of mass, flow rate can maximize the condensation efficiency of IDCCU by decreasing the flue gas temperature, while the use of the air heater can further reduce the flue gas temperature, and a stream of hot air can be utilized for space heating. A comparison is made with the other system on a performance basis. The results shows a clear difference in efficiencies and profit earned.

关键词： flue gas condensation gas boiler hybrid heat pump indirect contact condensing economizer thermo-economic analysis waste heat recovery

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Strain-Stabilized Metastable Face-Centered Tetragonal Gold Overlayer for Efficient CO₂ Electroreduction

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NANO LETTERS 2021年第2期21卷 1003-1010页

作者： Yu, Dan Gao, Lei Sun, Tulai Guo, Jingchun Yuan, Yuliang Zhang, Jiawei Li, Mengfan Li, Xingxing Liu, Maochang Ma, Chao Liu, Qinghua Pan, Anlian Yang, Jinlong Huang, Hongwen Hunan Univ Coll Mat Sci & Engn Adv Catalyt Engn Res Ctr Minist Educ Changsha 410082 Hunan Peoples R China Zhejiang Univ Technol State Key Lab Breeding Base Green Chem Synth Tech Ctr Electron Microscopy Hangzhou 310014 Zhejiang Peoples R China Zhejiang Univ Technol Coll Chem Engn Hangzhou 310014 Zhejiang Peoples R China Univ Sci & Technol China Dept Chem Phys Hefei Natl Lab Phys Sci Microscale Natl Synchrotron Radiat Lab Hefei 230026 Anhui Peoples R China Xi An Jiao Tong Univ Int Res Ctr Renewable Energy State Key Lab Multiphase Flow Power Engn Xian 710049 Shanxi Peoples R China

Synthesis of the unconventional phase of noble metal nanocrystals may create new opportunities in exploring intriguing physicochemical properties but remains challenging. In the research field of thin film growth, the interface strain offers a general driving force to stabilize the metastable phase of epitaxial film. Herein we extend this concept to the field of noble metal nanocrystals and report the solution synthesis of metastable face-centered tetragonal Au that has not been discovered before. The successful synthesis relies on the formation of intermetallic AuCu3@Au core-shell structure, where the interface strain stabilizes the metastable fct Au overlayer. Compared with the face-centered cubic Au counterpart, the metastable fct Au shows greatly improved catalytic activity toward CO2 reduction to CO. The density functional theory calculations and spectroscopic studies reveal that the metastable fct Au upshifts the d-band center, which lowers the energy barrier of key intermediate COOH* formation and thus facilitates the reaction kinetics.

关键词： face-centered tetragonal gold metastable phase interface strain CO2 electroreduction

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