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Oriented thermal etching of hollow carbon spheres with delicate heat management for efficient solar steam generation

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INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2021年 178卷 121579-121579页

作者： Tan, Yubo Liu, Maochang Wei, Daixing Ren, Jun Wang, Yechun Jin, Hui Shen, Shaohua Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Int Res Ctr Renewable Energy Xian Peoples R China North Univ China Sch Chem Engn & Technol Taiyuan 030051 Shanxi Peoples R China

Hollow carbon spheres (HCSs) with controllable morphology and structure have received considerable attention in the field of energy conversion and storage. Herein, monodispersed HCSs with cavity sizes tuned from 100 nm to 800 nm and shell thickness from 450 nm to 50 nm were successfully synthe-sized through a unique template-free thermal-etching method. It was evidenced that the dynamically controllable synthesis of HCSs was attributed to the "inside-out" oriented thermal oxidation etching of carbon spheres (CSs) induced by the differentiated "core-shell" chemical structures. Comparing to CSs, the obtained HCSs exhibited much increased efficiency for solar-driven interfacial steam generation (SISG), reaching as high as 88.9%, which outperforms most of the previously reported carbon-based materi-als. It was then demonstrated that the rational heat management for both photothermal and thermal-evaporation conversion is essential to achieve satisfying SISG efficiency. Depending on the increasing cav-ity sizes, HCSs presented gradual increases in both photothermal conversion and thermal-evaporation performances, mainly attributed to the improved light absorption and the delicate heat management, respectively. However, the further increase in cavity size resulted in excessive heat loss and presented decreased thermal-evaporation performance. This work provides an alternative and promising approach to the reasonable design of hollow nanostructures with delicate heat management for efficient SISG as well as other solar energy conversion applications. (c) 2021 Elsevier Ltd. All rights reserved.

关键词： Hollow carbon spheres Solar steam generation Heat management Photothermal conversion Thermal-evaporation conversion

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Thermodynamic Analysis and Case Study of a New Lignite-Fired power Plant Using Solar Energy as Drying Heat Source

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JOURNAL OF ENERGY engineering 2020年第3期146卷

作者： Wang, Chang'an Zhu, Xin Yuan, Maobo Che, Defu Xi An Jiao Tong Univ Sch Energy & Power Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

Lignite usually has a high moisture content and low calorific value, and should be predried before combustion to enhance power generation efficiency. Steam extracted from steam turbine and boiler exhaust gas are often applied in lignite predrying systems. However, the bleeding gas from the steam turbine reduces its output, and the exhaust gas originating from the boiler has insufficient drying capacity. In the present work, a new lignite power plant integrated with a solar drying system is proposed. A solar energy collection and storage tank system were employed to solve the problem of low heat density and instability of solar energy. Thermodynamic analysis results show that the area of reflectors declines at a decreasing rate with an increase in the direct normal irradiation (DNI). The power generation efficiencies of a solar drying lignite power plant (SDPP) and steam extraction drying power plant (SEDPP) can be increased by 0.68% and 0.33% for every 0.1 kg/kg rise in the drying degree. When the drying degree is 0.3 and DNI is 0.5 kW/m2, the economic analysis indicates that the simple payback periods for a conventional lignite power plant, SDPP, and SEDPP are 2.38, 3.20, and 2.53 years, respectively. In addition, the solar-to-electricity efficiency declines at a decreasing rate with increasing drying degree. The power generation efficiency of SDPP with dryer exhaust recovery is increased by 0.83% for each 0.1 kg/kg increase in the drying degree.

关键词： Lignite power plant Solar drying Thermodynamic analysis Energy recovery

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Measurements of isochoric specific heat capacity for 3,3,3-trifluoroprop-1-ene (R1243zf) at temperatures from (250 to 300) K and pressures up to 10 MPa

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JOURNAL OF CHEMICAL THERMODYNAMICS 2021年 161卷 106494-106494页

作者： Ding, Li Sheng, Bowen Hou, Yu Dong, Xueqiang Zhao, Yanxing Xu, Hongbo Shen, Jun Gong, Maoqiong Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Chinese Acad Sci Tech Inst Phys & Chem Key Lab Cryogen Beijing 100190 Peoples R China Univ Chinese Acad Sci Beijing 100049 Peoples R China

In this paper, a total of 86 isochoric specific heat capacity (c(v)) data of 3,3,3-trifluoroprop-1-ene (R1243zf) at temperatures from (250 to 300) K and pressures up to 10 MPa were measured using an adiabatic batch calorimeter. The standard uncertainties of temperature, pressure and isochoric specific heat capacity were estimated to be 12 mK, 5 kPa and 0.95%, respectively. A comparison was conducted between the experimental c(v) data and values calculated by three equations including the Helmholtz energy EOS (Akasaka and Lemmon, 2019) in REFPROP 10.0, the generalized equation (Zhong et al., 2019) and the corresponding states equation (Sheng et al., 2020) with the average absolute relative deviations (AARDs) of 2.43%, 0.91% and 0.84%, respectively. Among three equations, the corresponding states equation developed by Sheng et al. gives the best predictive performance for the liquid heat capacity of R1243zf. (C) 2021 Elsevier Ltd.

关键词： Adiabatic calorimeter R1243zf Isochoric specific heat capacity Compressed liquid

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Effects of electric field on pool boiling heat transfer over microstructured surfaces under different liquid subcoolings

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INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2022年第PartB期183卷 122154-122154页

作者： Liu, Bin Garivalis, Alekos Ioannis Cao, Zhizhu Zhang, Yonghai Wei, Jinjia Di Marco, Paolo Xian Jiantong Univ Sch Chem Engn & Technol 28 Xianning West Rd Xian 710049 Shaanxi Peoples R China Univ Pisa DESTEC Largo Lucio Lazzarino 1 I-56122 Pisa Italy Xian Jiantong Univ State Key Lab Multiphase Flow Power Engn 28 Xianning West Rd Xian 710049 Shaanxi Peoples R China

The uniform electric field is an effective method to improve boiling heat transfer performances, especially via breaking the mushroom bubbles and preventing dry-out;microstructured surfaces remarkably enhance both heat transfer coefficients and critical heat flux in boiling process. In the present study, the coupling effect of a uniform electric field and the microstructured surfaces on pool boiling in FC-72 at the liquid subcoolings ( xe002;T sub ) of 5 K, 15 K, 25 K, and 35 K was studied. Four kinds of the microstructured surfaces with different sizes of micro-pin-fins were fabricated and tested, and compared with a reference smooth surface. It was found that the critical heat flux (CHF) enhancement of the smooth surface due to the electric field ranges from 15.2% to 22.5% and increases with liquid subcooling. For the microstructured surfaces, the effects of electric field on CHF are closely related to the liquid subcooling and size of micro-pin-fins. For the surfaces with fin width of 30 mu m, the increase of CHF due to the electric field is not sensitive to the liquid subcooling;rather, for the surfaces with fin width of 50 mu m, the electric field CHF enhancement decreases with the liquid subcooling. The enhancement of CHF due to the electric field can be explained by the competition of a reduction of the Taylor length and the break of the vapor layer (beneficial to the CHF enhancement) and the field trap effect (not conducive to CHF improvement). The field trap effect on the surface with fin width of 50 mu m becomes very strong at xe002;T sub = 25 and 35 K;as a result, under these two conditions the CHF is reduced under the action of the electric field. (c) 2021 Published by Elsevier Ltd.

关键词： Pool boiling Electric field Microstructures Heat transfer Critical heat flux Subcooling

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High-Resolution Mapping of Winter Cereals in Europe by Time Series Landsat and Sentinel Images for 2016-2020

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REMOTE SENSING 2022年第9期14卷 2120-2120页

作者： Huang, Xiaojuan Fu, Yangyang Wang, Jingjing Dong, Jie Zheng, Yi Pan, Baihong Skakun, Sergii Yuan, Wenping Sun Yat Sen Univ Sch Atmospher Sci Zhuhai 519082 Peoples R China Xi An Jiao Tong Univ Dept Environm Sci & Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Zhejiang Univ Water Resources & Elect Power Coll Geomat & Municipal Engn Hangzhou 310018 Peoples R China Univ Maryland Dept Geog Sci College Pk MD 20742 USA

Winter cereals, including wheat, rye, barley, and triticale, are important food crops, and it is crucial to identify the distribution of winter cereals for monitoring crop growth and predicting yield. The production and plating area of winter cereals in Europe both contribute 12.57% to the total global cereal production and plating area in 2020. However, the distribution maps of winter cereals with high spatial resolution are scarce in Europe. Here, we first used synthetic aperture radar (SAR) data from Sentinel-1 A/B, in the Interferometric Wide (IW) swath mode, to distinguish rapeseed and winter cereals;we then used a time-weighted dynamic time warping (TWDTW) method to discriminate winter cereals from other crops by comparing the similarity of seasonal changes in the Normalized Difference Vegetation Index (NDVI) from Landsat and Sentinel-2 images. We generated winter cereal maps for 2016-2020 that cover 32 European countries with 30 m spatial resolution. Validation using field samples obtained from the Google Earth Engine (GEE) platform show that the producer's and user's accuracies are 91% +/- 7.8% and 89% +/- 10.3%, respectively, averaged over 32 countries in Europe. The winter cereal map agrees well with agricultural census data for planted winter cereal areas at municipal and country levels, with the averaged coefficient of determination R-2 as 0.77 +/- 0.15 for 2016-2019. In addition, our method can identify the distribution of winter cereals two months before harvest, with an overall accuracy of 88.4%, indicating that TWDTW is an effective method for timely crop growth monitoring and identification at the continent level. The winter cereal maps in Europe are available via an open-data repository.

关键词： winter cereals vegetation index time-weighted dynamic time warping Landsat Sentinel Google Earth Engine

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Chlorine-promoted perovskite nanocomposite as a high-performance oxygen transfer agent for chemical looping methane-assisted CO2 splitting

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CHEMICAL engineering JOURNAL ADVANCES 2020年 4卷

作者： Chen, Cunzhuang Yu, Wenbo Duan, Yifei Wang, Xinhe Zhang, Junshe Xian Jiaotong Univ Xian 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

Metal oxide-mediated CO2 splitting with the assistance of methane (aka chemical looping dry reforming of methane) is a novel and attractive approach for CO2 utilization. Herein, we demonstrate that doping and tai-loring the redox window of strontium ferrite (SrFeO3-8)-calcium oxide nanocomposites are effective strategies to improve the performance of chemical looping reforming. The oxygen storage capacity of this redox material is about 0.82 mol O/kg. Chlorine promotes coking in the reduction step;the tailored window not only suppresses complete oxidation of methane but also enhances CO2 transformation in a fixed-bed reactor. At 980 degrees C, the carbon efficiency is as high as 99%, very close to the equilibrium value. In this case, no recycling or downstream separa-tion is needed, making the proposed scheme more efficient. In addition, both the yield of CO and the productivity of syngas remain stable over 10 redox cycles. This exceptional redox performance makes the chloride-promoted SrFeO3-8-based nanocomposites a highly competitive and cost-effective chemical looping material.

关键词： Perovskite nanocomposite CO 2 splitting Methane Chemical looping

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Thermodynamic analysis and optimization of a dual-pressure Allam cycle integrated with the regasification of liquefied natural gas

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ENERGY CONVERSION AND MANAGEMENT 2021年 246卷 114660-114660页

作者： Li, Bo Wang, Shun-sen Qiao, Jiafei Wang, Bingbing Song, Liming Xi An Jiao Tong Univ Inst Turbomachinery Sch Energy & Power Engn State Key Lab Multiphase Flow Power Engn 28 Xianning West Rd Xian 710049 Peoples R China GUONENG GUOHUA BEIJING Elect Res Inst CO LTD Beijing Peoples R China

A novel dual-pressure Allam cycle integrated with the cold energy recovery of liquefied natural gas is proposed and analyzed in this paper. The feature of this system is that the cold energy of liquefied natural gas is successively utilized in two condensers with different condensing pressures, thereby reducing the heat transfer temperature difference in the condensation process and improving the system performance. The proposed system is discussed in detail based on the results of thermodynamic analysis and optimization. According to the simulation results, the largest exergy destruction belongs to the combustion chamber. Moreover, the exergy destruction in the condenser is greatly reduced owing to the dual-pressure condensation process. The system exergy efficiency first increases and then decreases with the increment of combustor temperature and main turbine inlet pressure. However, the system performance would deteriorate as the main turbine outlet pressure and bottom turbine outlet pressure increase. According to the results of single-objective optimization, the electricity efficiency and specific work of the dual-pressure Allam cycle are 15.76% and 68.75% higher than the classical Allam cycle, respectively. In addition, the exergy efficiency of the dual-pressure Allam cycle is up to 51.88%, which is improved by 1.57% compared with the single-pressure Allam cycle.

关键词： Dual pressure Allam cycle Liquefied natural gas Thermodynamic analysis Optimization

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Distinct point defect behaviours in body-centered cubic medium-entropy alloy NbZrTi induced by severe lattice distortion

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ACTA MATERIALIA 2022年第0期229卷

作者： Shi, Tan Su, Zhengxiong Li, Jing Liu, Chenguang Yang, Jinxue He, Xinfu Yun, Di Peng, Qing Lu, Chenyang Xi An Jiao Tong Univ Sch Nucl Sci & Technol Xian 710049 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Yantai Univ Coll Nucl Equipment & Nucl Engn Yantai 264005 Peoples R China China Inst Atom Energy Beijing 102413 Peoples R China Chinese Acad Sci Inst Mech State Key Lab Nonlinear Mech Beijing 100190 Peoples R China

The point defect properties of body-centered cubic medium-entropy alloy NbZrTi were studied by first-principles calculations. Due to severe lattice distortion, a significant portion of conventional vacancy and interstitial structures are unstable and require large structural relaxation, indicating an irregular energy landscape with large site-to-site variations. The average vacancy and interstitial formation energy are 0.95 eV +/- 0.34 eV and 1.92 eV +/- 0.39 eV, respectively, much lower than that of Nb (2.77 eV and 4.38 eV). The vacancy migration energy exhibits a wide distribution extending to 0 eV, resulting in preferential vacancy migration through low barrier sites. The interstitial diffusion is slower than that of pure Nb due to the reduction of long < 111 > diffusion induced by the site-to-site variations in stable interstitial orienta-tions. Ti atoms diffuse much faster than Nb and Zr atoms due to the preferential interstitial binding with Ti. The effect of atomic composition and short-range order on elemental and total interstitial diffusion was also investigated. The obtained first-principles results are important for the development of inter-atomic potentials for radiation damage studies. When irradiated with 3-MeV Fe ions at 675 & DEG;C to a peak dose of-100 dpa, NbZrTi reduced the void formation at high temperature compared to Nb owing to its higher equilibrium vacancy concentration and closer mobility between vacancies and interstitial atoms.& nbsp;(C) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

关键词： Medium-entropy alloys Point defect properties First-principles calculations Ion irradiation Radiation resistance

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Enhanced Ni/W/Ti Catalyst Stability from Ti-O-W Linkage for Effective Conversion of Cellulose into Ethylene Glycol

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ACS SUSTAINABLE CHEMISTRY & engineering 2020年第26期8卷 9650-9659页

作者： Li, Naixu Liu, Xu Zhou, Jiancheng Ma, Quanhong Liu, Maochang Chen, Wenshuai Southeast Univ Sch Chem & Chem Engn Nanjing 211189 Peoples R China Jiangsu Key Lab Biomass Energy & Mat Nanjing 210042 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Int Res Ctr Renewable Energy Xian 710049 Shaanxi Peoples R China Northeast Forestry Univ Key Lab Biobased Mat Sci & Technol Minist Educ Harbin 150040 Peoples R China

Direct conversion of cellulose into ethylene glycol is a promising route for transforming sustainable biomass resources into high-value chemicals. Although numerous attempts have been made to exploit tungsten-based hydrogenolysis catalysts in the catalytic conversion of cellulose to ethylene glycol for high conversion rate and selectivity, maintaining catalyst stability remains challenging. Herein, we have developed a Ni-W/M catalyst with good catalytic performance and stability, which were obtained by calcining Ni-W/MIL-125(Ti) precursor. The synthesized catalyst showed good cellulose conversion rate (100%) and ethylene glycol yield (68.7%). The tungsten species was linked to the TiO2 support by Ti-O-W bonds to reduce loss of the active tungsten component. The formation of new bonds enhanced the catalyst stability and durability, enabling the catalysts to retain high catalytic activity during recycling.

关键词： cellulose ethylene glycol MIL-125(Ti) stability catalysis

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Ultrastructure of Critical-Gel-like Polyzwitterion-Polyoxometalate Complex Coacervates: Effects of Temperature, Salt Concentration, and Shear

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MACROMOLECULES 2020年第24期53卷 10972-10980页

作者： Jing, Benxin Ferreira, Manuela Lin, Kehua Li, Ruipeng Yavitt, Benjamin M. Qiu, Jie Fukuto, Masafumi Zhu, Yingxi Wayne State Univ Dept Chem Engn & Mat Sci Detroit MI 48202 USA Brookhaven Natl Lab Natl Synchrotron Light Source 2 Upton NY 11973 USA Xi An Jiao Tong Univ Sch Nucl Sci & Technol Xian 710049 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

The structure of unconventional complex coacervates, such as polymer-nonpolymer complex coacervates, remains less investigated than that of the conventional coacervates formed between oppositely charged polyelectrolytes with symmetric charge species. Yet, their microscopic structural organization is important to further elucidate the mechanism of liquid-liquid-phase separation processes upon complexation. In this work, we characterize the microstructural organization of complex coacervates formed between inorganic polyoxometalate (POM) and polyzwitterion by small-angle X-ray scattering (SAXS) with in situ temperature and shear control. Despite the apparent transparent and homogeneous morphology of dense coacervates as observed by optical microscopy, our previous results (Macromolecules 2018, 51, 22, 9405-9411) suggest that dense polyzwitterion-POM coacervates exhibit critical-gel-like networks containing both complex-poor region (mesh pore) and complex-rich region (connective network). SAXS results as reported in this work support that the complex-rich region is actually in the form of loosely packed POM aggregates linked by polyzwitterion, designated as complex particles. The structure of aggregating complex particles is further examined against varied composition and salt concentrations, temperature, and shear, thanks to the high X-ray scattering contrast of POMs from that of other components in the coacervates. The complex particles in the dense coacervates appear to grow with more tightly packed POM aggregates with increasing POM-to-polyzwitterion concentration ratio, in contrast to more loosely packed POM aggregates with decreasing salt concentration. Conversely, increasing temperature could result in smaller complex particles containing more loosely packed POM aggregates, consistent with temperature-dependent viscoelasticity of dense coacervates. Furthermore, such POM-based hybrid dense coacervates exhibit intriguing strain-hardening behavior, resulting from s

关键词： Scattering Chemical structure Anions Solution chemistry X-ray scattering

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