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Optimum output temperature setting and an improved bed structure of metal hydride hydrogen storage reactor for thermal energy storage

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INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 2019年第35期44卷 19313-19325页

作者： Feng, Penghui Zhu, Luying Zhang, Yang Yang, Fusheng Wu, Zhen Zhang, Zaoxiao 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

As the well-known solid hydrogen storage materials, metal hydrides (MHs) have been developed systematically for decades. During recent years, due to the development of thermal energy storage (TES) market, they have also received much attention gradually as the excellent TES materials because of the high energy density, low cost, and good reversibility. In this study, the stabilized discharging performance of an MH reactor for TES was investigated by numerical simulation. A mathematical model combining multi physics and proportional-integral controller was established. Based on finite-time thermodynamics, gravimetric exergy-output rate (GEOR) considering the control requirement, finite-material, and finite-time constraints was defined. For a given reactor, the output temperature setting could be optimized based on GEOR. Besides, the effects of the reactor parameters on the optimum output temperature setting were systematically studied. The heat transfer analysis indicated the occurrence of the axial non-uniform reaction in the bed due to the inherent increase in the temperature of heat transfer fluid, resulting in the decrease of both GEOR and material availability. Accordingly, a new tapered bed structure (L/D-o = 600/50 mm) was proposed to effectively improve the discharging efficiency from 76 to 90% and GEOR from 65 to 120 W kg(-1), which provides a helpful guidance for the advanced designing and construction of MH reactor for the practical TES applications. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Metal hydride Thermal energy storage Finite-time thermodynamics Optimum output temperature setting Non-uniform reaction Improved bed structure

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The Influence of Internal Heat Exchanger on the Performance of Transcritical CO2 Water Source Heat Pump Water Heater

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ENERGIES 2020年第7期13卷 1787页

作者： Feng, Fan Zhang, Ze Liu, Xiufang Liu, Changhai Hou, Yu Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Zhengzhou Univ Sch Civil Engn Zhengzhou 450001 Peoples R China

The characteristics of the transcritical CO2 heat pump water heater (HPWH) system are;a lower inlet hot water temperature (Ti-hw) (sometimes this is lower than the water source temperature), and an outlet gas cooler temperature (To-gc) which is affected by the Ti-hw and often lower than the critical temperature. In order to study the effects of the internal heat exchanger (IHX) on the operational performance of the transcritical CO2 HPWH when To-gc is low, a transcritical CO2 water source HPWH experiment platform is established to conduct experimental research and comparative analysis on the operational performance of the transcritical CO2 water source HPWH, with or without IHX. It is found that, if only the coefficient of performance (COP) and heating at the optimal exhaust pressure of the transcritical CO2 water source HPWH were considered, COP and the heating of the non-IHX system would be slightly higher than those of the IHX system at the lower hot water flow and water source temperature, and this increase was not obvious. At the higher hot water flow rate and water source temperature, COP and the heating of the non-IHX system were also higher than those of the IHX system, and the increase was obvious. The experiment results showed that, near the optimal exhaust pressure, the variation range of COP and heating of the IHX system is relatively small, and the system has a relatively high stability.

关键词： transcritical CO2 heat pump water heater internal heat exchanger

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Mastering the surface strain of platinum catalysts for efficient electrocatalysis

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NATURE 2021年第7879期598卷 76-81页

作者： He, Tianou Wang, Weicong Shi, Fenglei Yang, Xiaolong Li, Xiang Wu, Jianbo Yin, Yadong Jin, Mingshang Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian Peoples R China Xi An Jiao Tong Univ Frontier Inst Sci & Technol Xian Peoples R China Shanghai Jiao Tong Univ Sch Mat Sci & Engn State Key Lab Met Matrix Composites Shanghai Peoples R China Chongqing Univ Coll Phys Chongqing Peoples R China Chongqing Univ Ctr Quantum Mat & Devices Chongqing Peoples R China Xian Technol Univ Sch Mat & Chem Engn Xian Peoples R China Shanghai Jiao Tong Univ Ctr Hydrogen Sci Shanghai Peoples R China Shanghai Jiao Tong Univ Mat Genome Initiat Ctr Shanghai Peoples R China Univ Calif Riverside Dept Chem Riverside CA 92521 USA

Platinum (Pt) has found wide use as an electrocatalyst for sustainable energy conversion systems(1-3). The activity of Pt is controlled by its electronic structure (typically, the d-band centre), which depends sensitively on lattice strain(4,5). This dependence can be exploited for catalyst design(4,6-8), and the use of core-shell structures and elastic substrates has resulted in strain-engineered Pt catalysts with drastically improved electrocatalytic performances(7,9-13). However, it is challenging to map in detail the strain-activity correlations in Pt-catalysed conversions, which can involve a number of distinct processes, and to identify the optimal strain modification for specific reactions. Here we show that when ultrathin Pt shells are deposited on palladium-based nanocubes, expansion and shrinkage of the nanocubes through phosphorization and dephosphorization induces strain in the Pt(100) lattice that can be adjusted from -5.1 per cent to 5.9 per cent. We use this strain control to tune the electrocatalytic activity of the Pt shells over a wide range, finding that the strain-activity correlation for the methanol oxidation reaction and hydrogen evolution reaction follows an M-shaped curve and a volcano-shaped curve, respectively. We anticipate that our approach can be used to screen out lattice strain that will optimize the performance of Pt catalysts-and potentially other metal catalysts-for a wide range of reactions.

关键词： Electrocatalysis Nanoparticles Science Humanities and Social Sciences multidisciplinary

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Microwave dielectric properties of temperature-stable zircon-type (Bi, Ce)VO4 solid solution ceramics

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JOURNAL OF THE AMERICAN CERAMIC SOCIETY 2020年第1期103卷 423-431页

作者： Guo, Huan-Huan Zhou, Di Liu, Wen-Feng Pang, Li-Xia Wang, Da-Wei Su, Jin-Zhan Qi, Ze-Ming Xi An Jiao Tong Univ Sch Elect Sci & Engn Minist Educ Elect Mat Res LabKey Lab Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ Sch Elect Sci & Engn Int Ctr Dielect Res Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ State Key Lab Elect Insulat & Power Equipment Xian Shaanxi Peoples R China Xian Technol Univ Microoptoelect Syst Labs Xian Shaanxi Peoples R China Univ Sheffield Dept Mat Sci & Engn Sheffield S Yorkshire England Xi An Jiao Tong Univ Int Res Ctr Renewable Energy State Key Lab Multiphase Flow Power Engn Xian Shaanxi Peoples R China Univ Sci & Technol China Natl Synchrotron Radiat Lab Hefei Anhui Peoples R China

In the (Bi1 - xCex)VO4 (0 <= x <= 1) system, we found that the (Bi1 - xCex)VO4 (0 <= x <= 0.1) belongs to the monoclinic scheelite phase and the (Bi1 - xCex)VO4 (0.7 <= x <= 1) belongs to the tetragonal zircon phase, while the (Bi1 - xCex)VO4 (0.1 x < 0.7) belongs to the mixed phases of both monoclinic scheelite and tetragonal zircon structure. Interestingly, two components with near-zero temperature coefficient of resonant frequency (TCF) appeared in this system. In our previous work, a near-zero TCF of similar to+15 ppm/degrees C was obtained in a (Bi0.75Ce0.25)VO4 ceramic with a permittivity (epsilon(r)) of similar to 47.9 and a Qf (Q = quality factor = 1/dielectric loss;f = resonant frequency) value of similar to 18 000 GHz (at 7.6 GHz). Furthermore, in the present work, another temperature-stable microwave dielectric ceramic was obtained in (Bi0.05Ce0.95)VO4 composition sintered at 950 degrees C and exhibits good microwave dielectric properties with a epsilon(r) of similar to 11.9, a Qf of similar to 22 360 GHz (at 10.6 GHz), and a near-zero TCF of similar to+6.6 ppm/degrees C. The results indicate that this system might be an interesting candidate for microwave device applications.

关键词： dielectric properties low temperature solid solutions X-ray methods

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Thermodynamic, life cycle, and techno-economic assessment of an autothermal supercritical water gasification system for direct processing raw pig manure: Hydrogen generation and ammonia recovery

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Energy 2025年 330卷

作者： Mingming Du Fan Liu Haoran Yuan Yu-nan Chen Jing Gu Guangzhou Institute of Energy Conversion Chinese Academy of Sciences (CAS) Guangzhou 510640 PR China State Key Laboratory of Multiphase Flow in Power Engineering (SKLMF) Xi'an Jiaotong University Xi'an Shaanxi 710049 PR China Guangdong Provincial Key Laboratory of Renewable Energy Guangzhou 510640 PR China

Supercritical water gasification (SCWG) exhibits an excellent potential for the conversion from pig manure (PM) to H 2 . However, the low solid content characteristic of raw PM and ammonia discharge significantly constrain the thermodynamic efficiency of SCWG. To address these limitations, a novel SCWG system was designed for simultaneous autothermal H 2 production and ammonia recovery from raw PM. Thermodynamic analysis, life cycle, and techno-economic were carried out to assess system performance. Results indicated that the novel system exhibited exceptional adaptability to variations in concentration and mass flow of raw PM, with autothermal H 2 production achieved even at low concentration of 10 %. Raw PM was converted into high-concentration slurries through pulping operations, thereby reducing exergy losses of gasification, heat exchange, and cooling units. Further, the system implemented an efficient ammonia recovery utilizing steam generated during the pulping stage. Under a typical scenario, energy efficiency, exergy efficiency, GWPs, and EP of the novel system reached 50.34 %, 45.99 %, 0.005 kgCO 2 -eq/kgH 2 , and 0.07 kgNO 3 - -eq/kg H 2 , respectively. The levelized hydrogen cost of the new system was 15.81 CNY/kg. This study provides a valuable solution for autothermal SCWG of low-solid-content and high-nitrogen-content feedstocks to produce H 2 and recover ammonia.

关键词： Ammonia recovery Autothermal hydrogen generation Raw pig manure Supercritical water gasification Thermodynamic analysis

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CO2 capture intensified by solvents with metal hydride

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FUEL PROCESSING TECHNOLOGY 2021年 218卷 106859-106859页

作者： Zhou, Chenyang Yu, Yunsong Zhang, Chen Zhang, Jingfeng Zhang, Zaoxiao Wang, Geoff G. X. Xi An Jiao Tong Univ Sch Chem Engn & Technol 28 Xianning West Rd Xian 710049 Peoples R China XianJiaotong Univ State Key Lab Multiphase Flow Power Engn 28 Xianning West Rd Xian 710049 Peoples R China Univ Queensland Sch Chem Engn St Lucia Qld 4072 Australia

Carbon dioxide capture significantly helps achieve the carbon neutral goal. Chemical absorption of CO2 by the solvent meets the bottleneck of the high energy consumption. An advanced solvent of CuH/PANI/TEMPO has been developed to reduce the energy consumption. The metal hydride CuH decomposes into the Cu atom to intensify the thermoelectric effect between PANI and TEMPO. The strong thermoelectric effect has the potential to enhance the CO2 desorption. DFT model and mass and energy transfer model in the nano-scale are developed accurately to quantify the system of CO2 and CuH/PANI/TEMPO. The CO2 fraction, electron density and velocity in the nano-domain are studied. It is found that the symmetrical electron density zone is produced. The mass transfer coefficient is improved by 2.15 times with 4.65 x 10(-6)m/s and the energy consumption is reduced to 1.02GJ/tCO(2). The thermoelectric conversion accounts for 31.4%-43.5% of the overall energy transfer.

关键词： Solvent Carbon dioxide Thermoelectric effect Energy consumption

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Investigation of operation parameters on the removal efficiency of methyl orange pollutant by cellulose/zinc oxide hybrid aerogel

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CHEMOSPHERE 2021年 284卷 131320-131320页

作者： Hasanpour, Maryam Motahari, Siamak Jing, Dengwei Hatami, Mohammad Univ Tehran Coll Engn Sch Chem Engn Dept Polymer Engn Tehran 111554563 Iran Xi An Jiao Tong Univ Int Res Ctr Renewable Energy State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Ferdowsi Univ Mashhad Dept Mech Engn Mashhad 917751111 Razavi Khorasan Iran

In this study, Cellulose/Zinc Oxide-x (CA/ZnO-x) hybrid aerogel with various concentrations of Zn2+ ion is synthesized through the hydrothermal method and used for organic pollutant removal. The CA/ZnO-x hybrid aerogel was characterized by XRD, UV-Visible, DRS, FTIR, FESEM, EDS, BET, LC-MS-MS analyses. In the present study, CA/ZnO-x hybrid aerogel as photocatalyst was used to investigate the influence of the photocatalytic degradation of methyl orange (MO) from an aqueous solution under UV irradiation. The morphology of CA/ZnO-x hybrid aerogels exhibited that the ZnO rice grain-like shape were successfully synthesized on the cellulose aerogel matrix. Also, the influence of various factors such as photocatalyst dosage, pH, initial concentration of MO, and irradiation intensity was investigated on the photocatalytic degradation rate of MO. The results revealed that the highest degradation efficiency and mineralization rate of MO were about 99.02% and 51.68%, respectively, after 90 min under UV irradiation using CA/ZnO-0.4 photocatalyst when pH = 3, C-0 = 10 ppm, photocatalyst dose = 9 g L-1 under the 300 W UV light irradiation. Furthermore, the synthesized photocatalyst exhibited a considerable firmness and easily separated from an aqueous solution for reuse.

关键词： Cellulose Zinc oxide Three-dimensional aerogel Photocatalyst degradation Hydrothermal treatment Reusability

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Novel scheelite-type [Ca0.55(Nd1-xBix)0.3]MoO4 (0.2 ≤ x ≤ 0.95) microwave dielectric ceramics with low sintering temperature

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JOURNAL OF THE AMERICAN CERAMIC SOCIETY 2020年第12期103卷 7259-7266页

作者： Hao, Shu-Zhao Zhou, Di Hussain, Fayaz Su, Jin-Zhan Liu, Wen-Feng Wang, Da-Wei Wang, Qiu-Ping Qi, Ze-Ming Xi An Jiao Tong Univ Elect Mat Res Lab Key Lab Minist Educ Xian 710049 Peoples R China Xi An Jiao Tong Univ Int Ctr Dielect Res Sch Elect & Informat Engn Xian 710049 Peoples R China NED Univ Engn & Technol Dept Mat Engn Karachi Pakistan Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Int Res Ctr Renewable Energy Xian Peoples R China Xi An Jiao Tong Univ State Key Lab Elect Insulat & Power Equipment Xian Peoples R China Univ Sheffield Dept Mat Sci & Engn Sheffield S Yorkshire England Xian Polytech Univ Sch Sci Xian Peoples R China Univ Sci & Technol China Natl Synchrotron Radiat Lab Hefei Peoples R China

Novel scheelite-type [Ca-0.55(Nd1-xBix)(0.3)]MoO4(0.2 <= x <= 0.95) ceramics were prepared using the solid-state reaction method. According to the X-ray diffraction data, a solid solution was formed in 0.2 <= x <= 0.95 and all the samples belong to pure scheelite phase with the tetragonal structure. As revealed by Raman spectroscopy, the number of vibrational modes decreased with the increase inxvalue, which further indicated that Bi(3+)ions occupied A-site of scheelite structure. As thexvalue increased, the sintering temperature decreased from 740 degrees C to 660 degrees C;the permittivity increased from 12.6 to 20.3;the Qf value first decreased slightly and gradually remained stable. Based on the infrared reflectivity spectrum analysis, the calculated permittivity derived from the fitted data shared the same trend with the measured value. The [Ca-0.55(Nd0.05Bi0.95)(0.3)]MoO(4)ceramic sintered at 660 degrees C attained a near-zero value temperature coefficient similar to tau(f)(-7.1 ppm/degrees C) and showed excellent microwave dielectric properties with ae(r) similar to 20.3 and a Qf similar to 33 860 GHz, making this system a promising candidate in the ultralow temperature cofired ceramic (ULTCC) technology.

关键词： infrared spectra low-sintering LTCC Raman spectra

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The mechanism of carbon-addition-enhanced electrochemical kinetics

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CHEMICAL PHYSICS LETTERS 2019年 732卷 136665-000页

作者： Zheng, Yao-Ting He, Min Cheng, Guang-xu Zhang, Zaoxiao Xuan, Fu-Zhen Wang, Zhengdong Xi An Jiao Tong Univ Sch Chem Engn & Technol State Key Lab Multiphase Flow Power Engn Xian Shaanxi Peoples R China East China Univ Sci & Technol Minist Educ Key Lab Pressure Syst & Safety Shanghai Peoples R China

The lithiation process of carbon coated silicon nanoparticles is simulated using molecular dynamics simulation in order to unveil the kinetics mechanism. The simulation shows that lithium ions are activated by charged carbon coating under coulombic and Van der Waals force. The lithiation reaction is determined by the activation degree of Li ions which varies on the carbon density, not by the diffusion amount of Li ions. It can interpret well the abnormal phenomenon that bigger diffusion flux of lithium ions does not bring about faster lithiation reaction rate and reveals the shortcoming of Butler-Volmer model describing the charge-transfer/ions-diffusion-controlled electrochemical kinetics.

关键词： Electrochemical kinetics Carbon Activation Energy barrier Molecular dynamics simulation

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Effects of ash parameters and fluxing agent on slag layer behavior in cyclone barrel

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FUEL 2019年 253卷 1140-1148页

作者： Tang, Chunli Zhu, Tao Wang, Limin Deng, Lei Che, Defu Liu, Yanhua Xi An Jiao Tong Univ Sch Human Settlements & Civil Engn Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ Sch Energy & Power Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

The behavior of the slag layer is very important for the safe and efficient operation of the cyclone barrel of cyclone-fired boiler. Ash parameters are the key factors affecting the formation and evolution of the slag layer. In order to figure out whether a stable slag layer could be formed when the cyclone-fired boiler burns the coal with low ash content or burns the coal with high ash melting point mixed with various contents of fluxing agent, the effects of ash content and fluxing agent on slag layer behavior are numerically examined for a vertical cyclone barrel. The decrease in the ash content can significantly reduce the mass flux of the captured particles as well as the velocity of the liquid slag layer. However, a stable slag layer can still be formed on the internal surface of the cyclone barrel even when the coal with a low ash content of 6.77% is burned. When the mass ratio of the fluxing agent is increased, the area of the internal surface covered with slag layer expands, whereas the solid slag layer becomes thinner. The amount of the fluxing agent has an optimal value. For the studied coal, when the mass ratio of the fluxing agent is 2.8%, the area of the internal surface covered with the slag layer expanded by about 37%, compared with the case without fluxing agent.

关键词： Cyclone barrel Slag layer behavior Ash content Fluxing agent Numerical investigation

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