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Experimental study on the effect of non-condensable gas dissolved in sub-cooled water on steam jet condensation in a rectangular channel

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INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2019年 134卷 668-679页

作者： Fu, Pengfei Zhou, Yao Yang, Xiaoping Yan, Junjie Liu, Jiping Xi An Jiao Tong Univ MOE Key Lab Thermal Fluid Sci & Engn Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ Shaanxi Key Lab Energy Chem Proc Intensificat Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ Sch Chem Engn & 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

An experimental study was performed to investigate the effect of non-condensable gas dissolved in sub cooled water on steam-water direct contact condensation (DCC). Non-condensable gas dissolved in the sub-cooled water was removed mostly by a degassing membrane device, and the mass fraction of dissolved oxygen was reduced from 7.6 mg/L to 4.6 mg/L and 1.1 mg/L respectively by degassing. Before and after degassing, the flow patterns, thickness of the mixture layer, temperature and pressure distributions, as well as average volumetric heat transfer coefficient were discussed respectively. The visualization results proved that the mixture layer between the water region and steam region mainly consisted of steam, hot water and a small amount of non-condensable gas dissolved out from water at saturated state. Furthermore, the formation mechanism of the mixture layer was qualitatively discussed. Besides, the temperature and pressure distributions on upper and bottom wall were hardly affected by the non-condensable gas dissolved in sub-cooled water. Moreover, the average volumetric heat transfer coefficient was investigated before and after degassing, and it was concluded that the dissolved non-condensable gas had a slight effect on the heat and mass transfer characteristic of DCC process. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Direct contact condensation Non-condensable gas Mixture layer Temperature distribution Pressure distribution Heat transfer

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Photocatalytic coupling of methane and CO2 into C2-hydrocarbons over Zn doped g-C3N4 catalysts

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APPLIED SURFACE SCIENCE 2019年 498卷 143861-000页

作者： Li, Naixu Li, Yao Jiang, Rumeng Zhou, Jiancheng Liu, Maochang Southeast Univ Sch Chem & Chem Engn Nanjing 211189 Jiangsu 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 Jiangsu Key Lab Biomass Energy & Mat Nanjing 210042 Jiangsu Peoples R China Xi An Jiao Tong Univ Suzhou Acad Suzhou 215123 Jiangsu Peoples R China

Methane conversion into ethanol and associated derivates under mild reaction conditions is of great significance, yet remains a challenge to date. Herein, we report efficient photocatalytic methane conversion into C2-hydrocarbons by using CO2 as a soft oxidant over a series of Zn-doped g-C3N4 composites. The results indicate that Zn atoms enter the lattice of g-C3N4 and are chemically coordinated therein in the form of ZneN bonds. The integration of Zn, on one hand, could increase the specific surface area thus surface alkaline sites, and broaden the light response ability as well, promoting the dehydrogenation of methane into methyl. One the other hand, it is found that the ZneN bonds could serve as electron channels, accelerating the charge separation inside g-C3N4 and enabling rapid electron transfer from g-C3N4 to surface photodeposited Ru cocatalyst. This unique behavior changes the photocatalytic pathway and promotes the formation of CH3CHO and CH3CH2OH, as demonstrated by our in-situ infrared spectroscopy. Our photocatalytic tests indicate that the 0.5% Ru/Zn-g-C3N4-1/20 composite possesses the best activity, with the yields of CO, CH3CHO, and CH3CH2OH up to 865.25, 330.38, and 1442.88 mu mol/g in 3 h, respectively. A proposed reaction mechanism based on the experimental results and above characterizations was finally deliberated.

关键词： Photocatalytic CH4 and CO2 C2-hydrocarbons Zn doped g-C3N4 Ru

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Experimental study of liquid sodium flow and heat transfer characteristics along a hexagonal 7-rod bundle

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APPLIED THERMAL engineering 2019年 149卷 578-587页

作者： Hou, Yandong Wang, Liu Wang, Mingjun Zhang, Kui Zhang, Xisi Hu, Wenjun Wu, Yingwei Tian, Wenxi Qiu, Suizheng Su, G. H. Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn 28 Xianning West Rd Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ Sch Nucl Sci & Technol Shaanxi Key Lab Adv Nucl Energy & Technol 28 Xianning West Rd Xian 710049 Shaanxi Peoples R China China Inst Atom Energy POB 27595 Beijing 102413 Peoples R China

The single-phase thermal hydraulic characteristics of liquid metal sodium are very essential for the design and safety analysis of sodium-cooled fast reactor (SFR). In this paper, the pressure drop and heat transfer features of single-phase liquid sodium were experimentally investigated in a 7 rod bundle with the velocity range of 0-4 m/s, heat flux up to 120 kW/m(2) and the absolute pressure range of 0-0.2 MPa. The corresponding Reynolds number ranges from 4000 to 40,000, and the Pe number varies from 0 to 340. It was found that the critical Re number for transition-turbulent flow of single-phase liquid sodium is 13,500 in the hexagonal 7-rod bundle. Then the effects of relative axial position, wall heat flux and Re number on the heat transfer were discussed, respectively. Some existing correlations in the literatures were assessed and compared with the experimental data. Results indicated that these correlations could not predict the current experiments well because of the different geometries and working fluids. The new correlations for the friction factor and Nu number calculations were proposed based on the current experimental data. For 98.5% of heat transfer data produced by the other researchers, the prediction error of the new correlation is less than 30%. For most of the experimental data, it is less than 20%, which sufficiently proves that the correlation developed in this paper could give a good prediction of the experimental data obtained by other researchers.

关键词： Liquid sodium Pressure drop Heat transfer Rod bundle

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CFD investigation on thermal hydraulics of the passive residual heat removal heat exchanger (PRHR HX)

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NUCLEAR engineering AND DESIGN 2018年第Feb.期327卷 139-149页

作者： Ge, Jian 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 Shaanxi Peoples R China

Passive residual heat removal (PRHR) system is a very important component of the passive safety systems in advanced passive safety pressurizer water reactors (PWRs) such as AP1000. The passive residual heat removal heat exchanger (PRHR HX) is a C-shape tube bundle heat exchanger immerged in the In-containment refueling water storage tank (IRWST) which removes the core decay heat during the accident transients. The performance of the PRHR HX is significant for the safety of the nuclear power plant (NPP). In this paper, the thermal hydraulics characteristics of the PRHR HX in the IRWST is analyzed using computational fluid dynamics (CFD). The tube region is modeled by the porous media approach along with the distributed resistance method. Heat transfer from the primary side fluid inside the tube to the secondary side fluid in the IRWST is considered. The simulation is carried out by the commercial CFD package FLUENT. The calculation of the flow resistance and heat transfer in the tube region is implemented using the User Defined Functions (UDF) in FLUENT based on the local flow conditions. Three dimensional distributions of the fluid velocity and temperature in the IRWST are obtained and thermal stratification is observed. The PRHR HX heat transfer capacity and the primary side fluid temperature distribution inside tubes are analyzed.

关键词： CFD PRHR HX Porous media approach Passive heat removal

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Catalytic cracking of n-hexane to light alkene over ZSM-5 zeolite: Influence of hierarchical porosity and acid property

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MOLECULAR CATALYSIS 2018年 448卷 91-99页

作者： Ji, Yajun Yang, Honghui Yan, Wei Xi An Jiao Tong Univ Dept Environm Sci & Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

ZSM-5 is active in n-hexane cracking to light alkenes, but with the disadvantage of fast deactivation. A long lifetime ZSM-5 with high activity and anti-carbon deposition performance was of great concern for industrial application. The hierarchical ZSM-5 zeolites (xHF-ZSM5) were obtained by chemical etching with fluoride ions and characterized by XRD, FTIR, NH3-TPD, SEM, TEM, N-2 adsorption-desorption. They showed higher BET surface area, larger mesoporous volume, less defect zones, commensurable microporous structure and acid property compared with that of the parent ZSM-5. The defects were dissolved resulting in higher crystallinity zeolite. They showed better catalytic performance with less carbon deposition in catalytic cracking of n-hexane due to superior channel structure, large mesoporous and macroporous structure. In order to reduce the amount of carbon deposition further, 0.5HF-ZSM5 was selected and made phosphorus modification. After phosphorus modification, the catalytic activity and stability was maintained at a high level, and the carbon deposition of n hexane cracking was restrained due to the gradual decreasing of acid amount with the increase of phosphorus content. The amount of carbon deposition decreased and reached the minimum of 23 mg g(-1) for 0.5HF-ZSM5-1P, which was four times less than that of the parent ZSM-5.

关键词： Hierarchical ZSM-5 zeolite Fluoride etching Phosphorus modification Catalytic activity Carbon deposition

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Electrocatalytically Activating and Reducing N2Molecule by Tuning Activity of Local Hydrogen Radical

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Angewandte Chemie 2023年第20期135卷

作者： Yuanyuan Yang Cejun Hu Dr. Jieqiong Shan Chuanqi Cheng Prof. Lili Han Prof. Xinzhe Li Ruguang Wang Prof. Wei Xie Prof. Yao Zheng Prof. Tao Ling Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education Tianjin Key Laboratory of Composite and Functional Materials School of Materials Science and Engineering Tianjin University Tianjin 300072 China Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education) Tianjin Key Lab of Molecular Recognition & Biosensing Renewable Energy Conversion and Storage Center College of Chemistry Nankai University Tianjin 300071 China School of Chemical Engineering The University of Adelaide Adelaide SA 5005 Australia State Key Laboratory of Structural Chemistry Fujian Institute of Research on the Structure of Matter Chinese Academy of Sciences Fuzhou 350002 China State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi An Shi Xi'an 710049 China

Decarbonizing N 2 conversion is particularly challenging, but essential for sustainable development of industry and agriculture. Herein, we achieve electrocatalytic activation/reduction of N 2 on X/Fe−N−C (X=Pd, Ir and Pt) dual-atom catalysts under ambient condition. We provide solid experimental evidence that local hydrogen radical (H*) generated on the X site of the X/Fe−N−C catalysts can participate in the activation/reduction of N 2 adsorbed on the Fe site. More importantly, we reveal that the reactivity of X/Fe−N−C catalysts for N 2 activation/reduction can be well adjusted by the activity of H* generated on the X site, i.e., the interaction between the X−H bond. Specifically, X/Fe−N−C catalyst with the weakest X−H bonding exhibits the highest H* activity, which is beneficial to the subsequent cleavage of X−H bond for N 2 hydrogenation. With the most active H*, the Pd/Fe dual-atom site promotes the turnover frequency of N 2 reduction by up to 10 times compared with the pristine Fe site.

关键词： Carbon Materials Electrocatalysis Metal-Free Catalysts Nitrogen Reduction Reaction

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Low-cost zinc-oxide nanoparticles for solar-powered steam production: Superficial and volumetric approaches

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JOURNAL OF CLEANER PRODUCTION 2021年第Part1期280卷 124261-124261页

作者： Ghafurian, Mohammad Mustafa Dastjerd, FatemeTavakoli Afsharian, Ali Esfahani, Faraz Rahimpour Niazmand, Hamid Behzadnia, Hadi Wongwises, Somchai Mahian, Omid Ferdowsi Univ Mashhad Dept Mech Engn Renewable Energy & Micro Nano Sci Lab Mashhad Razavi Khorasan Iran Xi An Jiao Tong Univ Sch Chem Engn & Technol Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China King Mongkuts Univ Technol Thonburi Fac Engn Dept Mech Engn Bangkok 10140 Thailand Natl Sci & Technol Dev Agcy NSTDA Pathum Thani 12120 Thailand

Using renewable energy, especially solar energy, is an essential requisite for preventing global warming and climate change. Solar-powered steam generation is one of the recent solutions to the problem of environmental pollution and can be a promising way to generate clean energy. In this study, the superficial and volumetric approaches of the zinc oxide nanoparticles (ZnO) in solar vapor generation have been compared experimentally. For the volumetric approach, the nanofluid performance at different mass concentrations (0.001%, 0.002%, and 0.004%) on the solar vapor generation was examined. For the superficial approach, the evaporative performance of delignified mulberry wood coated by ZnO nanoparticles as an absorbent (ZnO-Wood) was investigated. Moreover, the effect of nanoparticle size on optical and evaporative properties was evaluated. Finally, the economic performance of the ZnO nanofluid was compared to the other nanofluids. The results indicated that the evaporative efficiency of the nanofluids containing Zn0(50 nm) nanoparticles at 3 suns (3 kW/m(2)) was approximately two times greater than that of water (18%). However, the evaporative efficiency of ZnO-Wood was 3.15 (56%) times greater than that of water. In addition, the results of the nanoparticle size effect showed that increasing the size of nanoparticles from 20 nm to 50 nm in the superficial and volumetric approaches increases the evaporative efficiency by roughly 10% and 3%, respectively. Finally, the cost analysis of nanofluid for solar vapor generation illustrated that ZnO nanoparticles are cost-effective compared to other nanoparticles presented in the literature. (C) 2020 Published by Elsevier Ltd.

关键词： Clean steam generation Nanofluid Zinc oxide Nanoparticle Wood

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Mechanisms of pressure pulse for condensing supersonic steam jet in a rectangular channel

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EXPERIMENTAL THERMAL AND FLUID SCIENCE 2019年 105卷 223-233页

作者： Yang, Xiaoping Fu, Pengfei Chen, Nana Liu, Jiping Wei, Jinjia Xi An Jiao Tong Univ Sch Chem Engn & Technol Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ Shaanxi Key Lab Energy Chem Proc Intensificat Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ MOE Key Lab Thermal Fluid Sci & Engn Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

Pressure pulse is a potential risk during the application of condensing supersonic vapor jet in various industrial areas, particularly in a confined space, such as a pipe system. However, the source of pressure pulse remains unknown. In this work, experimental study on the dynamics of condensing supersonic steam jet in a rectangular channel was performed. Interface dynamics were captured by high-speed photography and quantitatively studied via an image-processing technique. The pressure pulse characteristics inside the channel were investigated using dynamic pressure transducers. Results proved that pressure pulse was caused by the growth, propagation, and detachment of interface wave induced by Kelvin-Helmholtz instability for the first time. In addition, the interface wave was proved to grow exponentially by experimental and theoretical methods. The dominant frequency was negative related, whereas its amplitude was positive related to the interface penetration length, which could be explained well by the growth, propagation, and detachment of interface wave. Finally, a prediction model for the dominant frequency was proposed on the basis of the propagation characteristics of interface wave. The proposed model could predict the dominant frequency at a maximum deviation of +/- 30%.

关键词： Supersonic steam jet Condensation Interface wave Pressure pulse

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The effect of cycA overexpression on hydrogen production performance of Rhodobacter sphaeroides HY01

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INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 2018年第30期43卷 13842-13851页

作者： Zheng, Xiaojing Ma, Hongyu Yang, Honghui Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Dept Environm Sci & Engn Xian 710049 Shaanxi Peoples R China

The gene cycA encodes a periplasmic protein, cytochrome c(2) (cyt c(2)), which dominates electron transfer from the membrane-bound ubiquinol: cyt c(2) oxidoreductase (cyt bc(1)) to the photosynthetic reaction center, contributing to the production of transmembrane proton potential and then the synthesis of ATP. For photosynthetic bacteria, the total energy supply for light anaerobic growth and hydrogen production comes from photophosphorylation. As a result, the key protein encoding gene plays an important role in hydrogen production. To figure out the specific effect of cycA expression level on H-2 production ability of Rhodobacter sphaeroides HY01, cycA-expression plasmids derived from pRK415 and pBBR1MCS-2 were constructed and then crossed into the parent strain R. sphaeroides HY01 for H-2 production test. And further verification by RT-PCR suggested that there was about 20% enhancement of cycA expression level by pBBR1MCS-2 where the H-2 production performance of corresponding strain was improved by 6-8% compared with blank control. In contrast, cycA expression level was about 3.4 folds by vector pRK415 compared with control strain, but corresponding strains showed slightly depressed H-2 production performance. Besides, the mutant XJ01 with cycA gene overexpressing by 70% in the genome of HY01(hupSL:cycA) also showed positive effect on hydrogen production performance. The results demonstrated that slightly overexpression of cycA could enhance the hydrogen production rate, but too much higher level of cycA-expression could show negative effect on H-2 production performance of R. sphaeroides HY01. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

关键词： cycA gene Overexpression level Rhodobacter sphaeroides Hydrogen production

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Simultaneous production of electricity and hydrogen from methanol solution with a new electrochemical technology

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INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 2019年第30期44卷 15766-15770页

作者： Fang, Xiao-Wen Wang, Lili Cai, Wen-Fang Jing, Deng-Wei Chen, Qing-Yun Wang, Yun-Hai Xi An Jiao Tong Univ Dept Environm Sci & Engn Xian 710049 Shaanxi Peoples R China Changqing Oilfield Co Oil & Gas Technol Res Inst Xian 710018 Shaanxi Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

It is known that the reaction from methanol to hydrogen has a positive Gibbs free energy and therefore cannot occur spontaneously. In the present work, by utilizing the chemical energy of neutralization, a new electrochemical technology was developed to produce hydrogen and electricity from methanol solution simultaneously, without needing external energy input. In our designed electrochemical cell, hydrogen can be produced on cathode while methanol can be oxidized on anode with additional electricity production. The effect of anode surface area on hydrogen production rate and power output was also investigated. With anode apparent surface area of 6.15 cm(2), initial hydrogen production rate can reach up to 1.07 m(3) H-2 m(-3) d(-1) and the maximum power density output of 1.26 W m(-2) can be achieved, at the same time. Although it is only a preliminary work, our work is supposed to provide a new approach for the on-board hydrogen production for the application of various fuel cell technologies, which is urgently needed nowadays. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Bipolar membrane Electrochemical Fuel cell Hydrogen Methanol

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