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CO_(2) Diffusivity in H_(2)O for Supercritical Conditions:A Molecular Dynamics Study

Journal of Thermal Science 2022年第5期31卷 1407-1415页

作者： chen longfei LIU Dong LI Qiang School of Energy and Power Engineering Nanjing University of Science and TechnologyNanjing210094China

Supercritical H_(2)O/CO_(2) mixtures(650 K–973 K and 25 MPa,not far away from the critical temperature and pressure of water)have recently been used as the working fluid for a novel power generation system with higher efficiency and zero pollutant emission compared to conventional coal-fired power *** knowledge of the diffusion of these mixtures is important for efficient design of the system ***,both experimental and theoretical data are scarce for typical working conditions in the ***,we investigated both the self-diffusion and the mutual diffusion of the supercritical H_(2)O/CO_(2) mixtures using molecular dynamics(MD)*** show that the mixture diffusion coefficients for supercritical conditions are more than one order of magnitude larger than those in the sub-critical *** results reveal that H_(2)O molecules prefer to gather with themselves rather than with CO_(2) molecules in the near-critical region,while there is no featured molecular structure for higher temperatures in the supercritical ***,the self-diffusion of CO_(2) in H_(2)O in the infinite-dilution regime features Arrhenius temperature dependent behavior in the supercritical region excluding the near-critical-temperature *** molecular interaction mechanisms also provide insights into the mutual diffusion behavior of CO_(2) in H_(2)O,which is well described by the Darken equation in the supercritical ***,engineering equations,namely the Speedy-Angell power-law equation and the Vignes equation,can reproduce MD simulated infinite-dilution self-diffusion coefficients and Maxwell-Stefan mutual diffusion coefficients,respectively,of the supercritical H_(2)O/CO_(2) mixtures.

关键词： supercritical fluid H_(2)O/CO_(2)mixture diffusion molecular dynamics

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Theoretical investigations on heat transfer to H2O/CO2 mixtures in supercritical region

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Science China(Technological Sciences) 2020年第6期63卷 1018-1024页

作者： chen longfei LIU Dong ZHANG HanLin LI Qiang MIIT Key Laboratory of Thermal Control of Electronic Equipment School of Energy and Power EngineeringNanjing University of Science and TechnologyNanjing 210094China

The supercritical H2O/CO2 mixture is the working fluid to drive a turbine in a novel power generation system with coal gasified in supercritical *** system is promising because of zero pollution emission in contrast to the conventional coal-fired power *** transfer coefficients of the supercritical H2O/CO2 mixtures are important to design heat transfer devices in this system,which is similar to the role of heat transfer to supercritical water in conventional ***,heat transfer to supercritical mixtures has received less ***,we show that the supercritical mixtures with H2O being one of the components,have similar convection heat transfer behavior to supercritical pure fluids for temperatures and pressures above the critical point of *** phenomenon was demonstrated from two ***,the forced convection heat transfer coefficients of supercritical mixtures were numerically calculated using the simulation model for supercritical pure fluids and using the thermophysical properties(density,heat capacity,thermal conductivity and viscosity)of supercritical mixtures as *** calculated results agree well with experimental data in the supercritical ***,the calculated results also agree well with the correlations for supercritical pure *** mechanisms were investigated by molecular dynamics simulations on the diffusion of supercritical *** results lay the foundation for predicting convection heat transfer coefficients of supercritical mixtures and for designing heat transfer devices with supercritical mixtures as heat transfer fluids.

关键词： supercritical fluid H2O/CO2 mixture forced convection molecular dynamics

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Analysis of a 1 kW organic Rankine cycle using a scroll expander for engine coolant and exhaust heat recovery

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Frontiers in Energy 2017年第4期11卷 527-534页

作者： Yiji LU Anthony Paul ROSKILLY Long JIANG longfei chen Xiaoli YU Sir Joseph Swan Centre for Energy Research Newcastle University Newcastle NE1 7RU UK Institute of Refrigeration and Cryogenics Shanghai Jiao TongUniversity Shanghai 200240 China School of Energy and Power Engineering Beihang University Beijing 100191 China Department of Energy Engineering Zhejiang University Hangzhou310027 China

The development of engine waste heat recov- ery technologies attracts ever increasing interests due to the rising strict policy requirements and environmental con- cerns. This paper presented the study of engine coolant and exhaust heat recovery using organic Rankine cycle （ORC）. Eight working fluids were selected to evaluate and compare the performance of the integrated waste heat recovery system. Rather than the conventional engine ORC system mainly focusing on the utilization of exhaust energy, this work proposed to fully use the engine coolant energy by changing the designed parameters of the ORC system. The case study selected a small engine as the heat source to drive the ORC system using a scroll expander for power production. The evaluation results suggest that under the engine rated condition, the solution to fully recover the engine coolant energy can achieve a higher power generation performance than that of the conven- tional engine ORC system. The results suggest that adding a recuperator to the ORC system can potentially improve the system performance when the working fluids are dry and the overall dumped heat demand of the system can be reduced by 12% under optimal conditions. When the ORC evaporating and condensing temperature are respectivelyset at 85℃ and 30℃, the integrated engine waste heat recovery system can improve the overall system efficiency by 9.3% with R600, R600a or n-Pentane as the working fluid.

关键词： organic Rankine cycle scroll expander cool-ant and exhaust recovery internal combustion engine

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Influence of geometry on the thermal performance of water pit seasonal heat storages for solar district heating

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Building Simulation 2021年第3期14卷 579-599页

作者： Yakai Bai Ming Yang Jianhua Fan Xiaoxia Li longfei chen Guofeng Yuan Zhifeng Wang Key Laboratory of Solar Thermal Energy and Photovoltaic Systems Chinese Academy of SciencesBeijing 700190China Institute of Electrical Engineering Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Department of Civil Engineering Technical University of DenmarkBrovej 1182800 Kgs.LyngbyDenmark Joint Laboratory Institute of Electrical EngineeringChinese Academy of Sciences and Guangdong Five Star Solar Energy Co.Ltd.Beijing 100190China Lanzhou University of Technology Gansu 730050China

The aim of the study is to investigate the influence of geometry on the thermal capacity and stratifications of a water pit heat storage for solar district heating.A TRNSYS component model for a truncated cone water pit was developed based on the coordinate transformation method and validated by experimental results from the water pit heat storage in Huangdicheng in *** thermal performance of 26 water pits with different heights and side wall slopes was calculated for 10 consecutive *** takes four to six years for the water pit to reach steady-state *** operation data from the tenth year was selected to evaluate the thermal performance of each *** results show that because of the thermal insulation on top of the water pit,the height to diameter ratio of a water pit with minimum annual heat loss was always smaller than *** annual storage efficiency of a water pit increases with side wall slope due to the reduced side wall *** is an almost linear increase in the thermal stratification number of a water pit with *** an increase in the height,thermal stratification in water pits with a steeper slope increased more gradually than water pits with a lower *** findings in this paper are relevant for the design optimization of water pits as seasonal thermal energy storages.

关键词： water pit seasonal heat storage truncated cone storage capacity thermal stratification coordinate transformation

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Thermal Analysis of a Volumetric Solar Receiver

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Journal of Thermal Science 2019年第6期28卷 1176-1185页

作者： chen longfei YANG Ming LI Jinping BAI Yakai LI Xiaoxia TANG Wenxue YANG Nancong WANG Zhifeng Lanzhou University of Technology Lanzhou 730050China Key Laboratory of Solar Thermal Energy and Photovoltaic Systems Chinese Academy of SciencesBeijing 100190China Institute of Electrical Engineering Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Beijing Engineering Research Center of Solar Thermal Power Beijing 100190China Beijing CSP International Cooperation Centre Beijing 100190China Joint Laboratory Institute of Electrical EngineeringChinese Academy of Sciences and Guangdong Five Star Solar Energy Co.Ltd.Beijing 100190China Guangdong 5 Star Solar Energy CO.LTD Dongguan 523051China

The volumetric receiver has received wide attention due to its high thermal efficiency. This paper studied a new type of a solid-liquid composite volumetric receiver. The heat transfer in a solid-liquid composite volumetric solar receiver was analyzed using a one-dimensional unsteady simulation model of the solid-liquid receiver. The model included absorption of the incident solar radiation by the glass window, the silicon carbide porous ceramic heat absorber panel and the water. The results were verified against experimental data for a volumetric receiver and the error did not exceed 10%. It can be used to predict the heat transfer in solid-liquid composite volumetric receivers.

关键词： solar receiver solid-liquid composite absorber silicon carbide porous ceramic volumetric solar collector

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Efficient epoxidation of propylene over non-noble nickel-based catalyst promoted by alkali metals

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Science China Chemistry 2024年第11期67卷 3697-3705页

作者： Wenqian Li Wanting Li Xinxin Cao longfei chen Yibo Qin Yanfeng Zhu Yanfei Zhang Gai Miao Lingzhao Kong Jiong Li Xinqing chen State Key Laboratory of Low Carbon Catalysis and Carbon Dioxide Utilization CAS Key Laboratory of Low-carbon Conversion Science and EngineeringShanghai Advanced Research InstituteChinese Academy of SciencesShanghai 201210China University of Chinese Academy of Sciences Beijing 100049China School of Environmental Science and Engineering Suzhou University of Science and TechnologySuzhou 215009China Shanghai Synchrotron Radiation Facility Zhangjiang National LabShanghai Advanced Research InstituteChinese Academy of SciencesShanghai 201210China

The application of non-noble metal catalysts in the catalytic direct gas-phase epoxidation of propylene with H2and O2to produce propylene oxide is valuable and challenging. The introduction of alkali metal promoters is one of the effective methods to improve the catalytic activity of catalysts. Herein, a series of alkali metal(Li, Na, K, Rb, and Cs)-promoted Ni/TS-1 catalysts were prepared to deeply understand the effect of alkali metals on the structure-activity relationship for gas-phase epoxidation of propylene. Among them, the Na-Ni/TS-1 catalyst exhibits the highest catalytic activity(propylene conversion of 7.35% and PO formation rate of 157.9 g h^(-1)kg_(cat)^(-1)) and the best stability(long-term stability exceeding 140 h at 200 ℃). X-ray absorption and photoelectron spectroscopy revealed that the electronic structure of Ni can be tuned by the addition of alkali metal ***3-TPD-MS, CO_(2)-TPD-MS, and C_(3)H_(6)-TPD-MS results indicate that the acidity of the catalyst can also be adjusted by the introduction of alkali metal, whereas the Na-Ni/TS-1 catalyst exhibits the strongest C_(3)H_(6) adsorption capacity. Thus, the suitable acid-base properties, unique electronic properties of Ni species, and the strongest propylene adsorption capacity resulted in improved propylene gas-phase epoxidation activity of Na-Ni/TS-1 catalyst. This study not only provides a new strategy for the practical application of nickel-based catalysts in the gas-phase epoxidation of propylene but also provides insights into the promoting effect of alkali metals.

关键词： propylene epoxidation Ni/TS-1 catalyst alkali metal precipitating agents

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A meta-analysis of the impacts of forest logging on soil CO2 efflux

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Research in Cold and Arid Regions 2020年第3期12卷 165-179页

作者： longfei chen YangZhou Xiang ZhiBin He Jun Du PengFei Lin Xi Zhu Linze Inland River Basin Research Station Chinese Ecosystem Research NetworkKey Laboratory of Eco-hydrology of Inland River BasinNorthwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhouGansu 730000China School of Geography and Resources Guizhou Education UniversityGuiyangGuizhou 550018China

Soil CO2 efflux,the second largest flux in a forest carbon budget,plays an important role in global carbon *** logging is expected to have large effects on soil CO2 efflux and carbon sequestration in forest ***,a comprehensive understanding of soil CO2 efflux dynamics in response to forest logging remains elusive due to large variability in results obtained across individual ***,we used a meta-analysis approach to synthesize the results of 77 individual field studies to determine the impacts of forest logging on soil CO2 *** results reveal that forest logging significantly stimulated soil CO2 efflux of the growing season by 5.02%.However,averaged across all studies,nonsignificant effect was detected following forest *** large variation among forest logging impacts was best explained by forest type,logging type,and time since *** CO2 efflux in coniferous forests exhibited a significant increase(4.38%)due to forest logging,while mixed and hardwood forests showed no significant *** type also had a significant effect on soil CO2 efflux,with thinning increasing soil CO2 efflux by 12.05%,while clear-cutting decreasing soil CO2 efflux by 8.63%.The time since logging also had variable effects,with higher soil CO2 efflux for 2 years after logging,and lower for 3-6 years after logging;when exceeded 6 years,soil CO2 efflux *** significantly negative impacts of forest logging were detected on fine root biomass,the general positive effects on soil CO2 efflux can be explained by the accelerated decomposition of organic matter as a result of elevated soil temperature and organic substrate *** results demonstrate that forest logging had potentially negative effects on carbon sequestration in forest ecosystems.

关键词： soil respiration forest ecosystem thinning clear-cutting time since logging

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Long-term thinning decreases the contribution of heterotrophic respiration to soil respiration in subalpine plantations

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Journal of Forestry Research 2024年第3期35卷 189-204页

作者： longfei chen Zhibin He Wenzhi Zhao Xi Zhu Qin Shen Mingdan Song Zhengpeng Li Junqia Kong Shuping Yang Yuan Gao Northwest Institute of Eco-Environment and Resources Chinese Academy of SciencesLanzhou 730000People's Republic of China State Forestry Administration Key Laboratory of Forest Resources and Environmental Management Beijing Forestry UniversityBeijing 100083People's Republic of China Academy of Agriculture and Forestry Sciences Qinghai UniversityXining 810000People's Republic of China College of Landscape Architecture Zhejiang A&F UniversityHangzhou 310000People's Republic of China

Interest in the dynamics of soil respiration(R_(S))in subalpine forest ecosystems is increasing due to their high soil carbon density and potential sensitivity to environmental ***,as a principal silvicultural practice,the long-term impacts of thinning on R_(S) and its heterotrophic and autotrophic respiration components(R_(h) and Ra,respectively)in subalpine plantations are poorly understood,espe-cially in winter.A 3-year field observation was carried out with consideration of winter CO_(2) efflux in middle-aged sub-alpine spruce plantations in northwestern China.A trench-ing method was used to explore the long-term impacts of thinning on Rs,Rn and R_(a).Seventeen years after thinning,mean annual Rs,Rn and R_(a) increased,while the contribu-tion of R_(h) to R_(s) decreased with thinning *** significantly decreased winter R,because of the reduction in R_(n) but had no significant effect on *** temperature sensitivity(Q_(10))of R_(h) and R_(a) also increased with thinning intensity,with lower Q_(10) values for R_(h)(2.1-2.6)than for Ra(2.4-2.8).The results revealed the explanatory variables and pathways related to R_(n) and R_(a) *** increased soil moisture and nitrate nitrogen(NO_(3)^(-)-N),and the enhanced nitrogen and water availability promoted R_(h) and R_(a) by improving fine root biomass and microbial *** results highlight the positive roles of NO_(3)^(-)-N in stimulating R_(s) components following long-term ***,applications of nitrogen fertilizer are not recommended while thinning subalpine spruce plantations from the perspective of reducing soil CO_(2) *** increased Q_(10) values of R_(s) components indicate that a large increase in soil CO_(2) emissions would be expected following thinning because of more pronounced climate warming in alpineregions.

关键词： Heterotrophic respiration Autotrophic respiration Long-term thinning impacts Cold seasons Subalpine plantations Temperature sensitivity

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The TMRT K band observations towards 26 infrared dark clouds:NH_3, CCS, and HC_3N

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Science China(Physics,Mechanics & Astronomy) 2021年第7期64卷 126-136页

作者： Jinjin Xie Gary A.Fuller Di Li longfei chen Zhiyuan Ren Jingwen Wu Yan Duan Junzhi Wang Juan Li Nicolas Peretto Tie Liu Zhiqiang Shen National Astronomical Observatories Chinese Academy of SciencesBeijing100101China University of Chinese Academy of Sciences Beijing100049China Jodrell Bank Centre for Astrophysics Department of Physics and AstronomyUniversity of ManchesterManchesterM139PLUK Intituto de Astrofísica de Andalucia(CSIC) Granada18008Spain I.Physikalisches Institute University of CologneKöln50937Germany NAOC-UKZN Computational Astrophysics Centre University of KwaZulu-NatalDurban4000South Africa Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai200030China School of Physics&Astronomy Cardiff UniversityCardiffCF243AAUnited Kingdom

We present one of the first Shanghai Tian Ma Radio Telescope (TMRT) K Band observations towards a sample of 26 infrared dark clouds (IRDCs).We observed the (1,1),(2,2),(3,3),and (4,4) transitions of NH_(3) together with CCS (2_(1)–>1_(0)) and HC_(3)NJ=2-1,*** survey dramatically increases the existing CCS-detected IRDC sample from 8 to 23,enabling a better statistical study of the ratios of carbon-chain molecules (CCM) to N-bearing molecules in *** the newly developed hyperfine group ratio (HFGR) method of fitting NH_(3) inversion lines,we found the gas temperature to be between 10 and18 *** column density ratios of CCS to NH_(3) for most of the IRDCs are less than 10^(-2),distinguishing IRDCs from low-mass star-forming *** carried out chemical evolution simulations based on a three-phase chemical model *** measurements of the column density ratios between CCM and NH_(3) are consistent with chemical evolutionary ages of 10^(5) yr in the *** of the data and chemical models suggest that CCS,HC_(3)N,and NH_(3) are sensitive to the chemical evolutionary stages of the sources.

关键词： star formation infrared dark clouds chemical evolution

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In silico Analysis of the Potential Infection Mechanisms of Magnaporthe grisea from Horizontal Gene Transfer Hypothesis

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Genomics, Proteomics & Bioinformatics 2009年第3期7卷 77-86页

作者： Chunyang Li Ying Wang Hao Peng Hejiao Bian Mingwei Min longfei chen Qian Liu Jinku Bao School of Life Sciences Sichuan University Chengdu 610064 China China National Center for Biotechnology Development Beijing 100081 China

Horizontal gene transfer （HGT） has long been considered as a principal force for an organism to gain novel genes in genome evolution. Homology search, phylogenetic analysis and nucleotide composition analysis are three major objective approaches to arguably determine the occurrence and directionality of HGT. Here, 21 genes that possess the potential to horizontal transfer were acquired from the whole genome of Magnaporthe grisea according to annotation, among which three candidate genes （corresponding protein accession numbers are EAA55123, EAA47200 and EAA52136） were selected for further analysis. According to BLAST homology results, we subsequently conducted phylogenetic analysis of the three candidate HGT genes. Moreover, nucleotide composition analysis was conducted to further validate these HGTs. In addition, the functions of the three candidate genes were searched in COG database. Consequently, we conclude that the gene encoding protein EAA55123 is transferred from Clostridium perfringens. Another HGT event is between EAA52136 and a certain metazoan＇s corresponding gene, but the direction remains uncertain. Yet, EAA47200 is not a transferred gene.

关键词： Magnaporthe grisea infection mechanism horizontal gene transfer homology phylogenetic analysis nucleotide composition

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