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Molecular dynamics simulations of the effects of metal nanoparticles on methane hydrate formation

JOURNAL OF MOLECULAR LIQUIDS 2022年 356卷 118962-118962页

作者： Liu, Ni Li, Tanyu Liu, Tingsong Yang, Liang Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

Understanding the properties of methane hydrate formation is important for the storage and transport of methane in the form of gas hydrates. In this study, nanosecond simulations were performed to investigate the formation of methane hydrates in the presence of Fe, Cu, Ag and their corresponding oxide nanoparticles. The effects of different nanoparticle and nanoparticle concentration on the rate and amount of CH4 hydrate formation were explored. The simulation results show that metal nanoparticles have a mixed effect on the kinetic improvement of methane hydrate generation process, which varies with the type and concentration of metal nanoparticles. Compared to the pure water system, the formation of methane hydrate was promoted to different degrees in the metal nanoparticle system, in the order of nano-Ag > nano-Cu > nano-Fe, which is mainly attributed to the excellent thermal conductivity of the metal itself. For the single metal oxide nanoparticle system, the promotion effect of nano-Ag2O was not obvious, while the promotion effect of nano-CuO was the best, and the promotion degree is in the order of nano-CuO > nano-FeO > nano-Ag2O. For the multiple metal oxide nanoparticle systems, the two nano-FeO system showed faster growth rate and more hydrate cages formed, which was better than the single nano-FeO and nano-Fe systems. The nano-CuO system showed the same results. However, the promotion effect of nano-Ag2O was slightly smaller than that of nano-Ag at the particle size and concentration studied in this work. (c) 2022 Elsevier B.V. All rights reserved.

关键词： Molecular dynamics simulation Methane hydrate Metal nanoparticles Formation rate

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Modeling Study of the Slag Behaviors Based on Temperature-Time-Viscosity of Crystalline Slag in an Entrained-flow Gasifier

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ACS OMEGA 2022年第14期7卷 11799-11808页

作者： Zhang, Binbin Jin, Jing Zhang, Nan Liu, Haifeng Shi, Huancong Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China East China Univ Sci & Technol Inst Clean Coal Technol Shanghai Engn Res Ctr Coal Gasificat Shanghai 200237 Peoples R China Zhejiang Univ Huzhou Inst Huzhou 31300 Zhejiang Peoples R China Univ Shanghai Sci & Technol Dept Environm Sci & Engn Shanghai 200093 Peoples R China

The crystal growth process has an important influence on the viscosity of the slag, which affects the characteristics of the slag layer on the wall of the gasifier. The slag flow and heat transfer model based on temperature-time-viscosity of crystalline slag were established, to predict the slag behaviors and protect gasifier. The results showed the overall viscosity of the slag after considering the residence time effect was higher than that when using the measured viscosity-temperature curve value. The liquid slag thickness, solid slag thickness, and residence time increased after the slag viscosity amendment, while the slag flow velocity and heat flux density decreased. Moreover, several types of crystallized slag were constructed to study the effects of crystal morphology and degree of crystallization difficulty on slag behaviors. The result indicated that the difficulty and crystal morphology of the slag crystallization cannot be ignored when using crystallized slag in gasification.

关键词： Thickness Crystals Liquids Layers Viscosity

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Study on the effect of circulating air volume on the performance of closed loop heat pump drying system

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APPLIED THERMAL engineering 2022年 210卷 118362-118362页

作者： Ren, Yan Chen, Zhongwei Wu, Weidong Wang, Hao Yang, Yingying Yang, Qiguo Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

Considering the fact that high energy consumption and low drying temperature of current drying system was not appropriate for the high temperature industrial drying, a closed loop heat pump drying system with high drying temperature was designed, established and explored. As a key operation parameter, the circulating air volume was closely related to the drying temperature and could affect the system performance. The effect of circulating air volume on the circulating air temperature, coefficient of performance (COP), moisture extraction rate (MER) and specific moisture extraction rate (SMER) were all experimentally investigated in this study. The results showed that with the increase of circulating air volume, the circulating air temperature was gradually decreased, while the system COP was oppositely increased. And both the system MER and SMER firstly increased and then decreased with increasing air volume. The drying temperature could exceed 70 ? when the circulating air volume was below 539.8 m(3)/h, and reach its maximum value 71.11 ? when the circulating air volume was 388.5 m(3)/h, meeting the high drying temperature requirement. At the same time, both the system MER and SMER could reach their maximums (i.e., 3.27 kg/h and 1.40 kg/(kW.h)), showing the excellent dehumidification performance of this system. Besides, when the circulating air volume was 736.1 m(3)/h, the system COP could reach its maximum 6.56, indicating high energy efficiency. These results can provide guidance for the popularization and application of heat pump drying technology in the industrial drying field.

关键词： heat pump drying system industrial drying circulating air volume coefficient of performance (COP) moisture extraction rate (MER)

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Effects of carbon nanotube on methane hydrate formation by molecular dynamics simulation

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JOURNAL OF MOLECULAR LIQUIDS 2022年第PartA期368卷

作者： Li, Tanyu Liu, Ni Huang, Jialei Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

The development of gas hydrate technology is beneficial to achieve efficient storage and transportation of methane. The formation of methane hydrate in the presence of single and multiple CNTs was simulated by molecular dynamics applying NPT and NVE ensemble in this study. The cage identification method was applied to detect the number of simulated generated cages. Due to their unique tubular structure, high specific surface area, excellent thermal conductivity and their own activity, the addition of CNTs promoted the formation of hydrates, increased the generation rate and the number of generations, and reduced the nucleation time compared to the pure water system. Triple CNTs showed the best promotion effect under NVE ensemble, and the order of promotion was double CNTs (1.8 wt%) > single CNT (0.9 wt% ) > triple CNTs (2.7 wt%) under NPT ensemble. The results show that CNTs facilitate the growth of methane hydrate and the promotion effect varies with concentration and temperature, which provides a functional microcosmic implication for future studies on methane storage and transportation.(c) 2022 Elsevier B.V. All rights reserved.

关键词： Molecular dynamics simulation CH 4 hydrate Carbon nanotubes Formation rate

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Energy and exergy analysis of supercritical/transcritical CO2 cycles for water injected hydrogen gas turbine

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ENERGY 2022年第0期260卷

作者： Qi, Yinke Huang, Diangui Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

This paper investigated the supercritical/transcritical carbon dioxide cycles for water injected hydrogen gas turbine with the advantages of zero carbon emission, low pollution, high efficiency, low cost and so on. This paper selected several typical combined cycles from more than a dozen layouts studied by our team. We con-structed a thermodynamic energy and exergy analysis model and verified it with the experimental models from GE. The maximum energy efficiency and its corresponding exergy efficiency that each layout can achieve are obtained after parameter sensitivity analysis, water mixing research and exergy analysis. It can be found that the combined cycle energy efficiency decreases as the water-hydrogen ratio increases. The component with the largest exergy loss is the combustor, accounting for 23.58%. And the transcritical CO2 dual recuperated com-bined cycle is the best layout with the combined cycle energy efficiency of 64.39% and the combined cycle exergy efficiency of 62.96%. The research done in this paper can provide a basis for the design of next-generation gas turbine.

关键词： Gas turbine Waste heat recovery Supercritical/transcritical CO2 cycle Thermodynamic energy analysis Thermodynamic exergy analysis Zero carbon emission

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The collocation spectral method with domain decomposition for radiative heat transfer in two-dimensional enclosures

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COMPUTERS & MATHEMATICS WITH APPLICATIONS 2022年第0期123卷 204-215页

作者： Zhou, Rui-Rui Sun, Ya-Song Li, Ben-Wen Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Northwestern Polytech Univ Sch Power & Energy Shaanxi Key Lab Thermal Sci Aeroengine Syst Xian 710072 Peoples R China Yangtze River Delta Res Inst NPU Ctr Computat Phys & Energy Sci Taicang 215400 Peoples R China Dalian Univ Technol Sch Energy & Power Engn Key Lab Ocean Energy Utilizat & Energy Conservat Minist Educ Dalian 116024 Peoples R China

In this paper, the collocation spectral method (CSM) combined with domain decomposition method is developed to solve the radiative transfer equation in two-dimensional irregular domains. Three benchmark problems consist of the square enclosure, the L-shaped enclosure and the square enclosure with a centered obstruction are solved and compared with the published data to validate the ability of present developed method. The comparison shows good agreements and indicates that the method has a good accuracy for all problems. Then, the performances of influence matrix technique and iterative substructuring technique to exchange the radiative information between subdomains are compared. It is found that, in the serial computations, the computational cost of influence matrix technique is hundreds of times more expensive than that of iterative substructuring technique. The high cost of influence matrix technique is due to that the radiative intensity is a high dimensional variable with angular dependence, and tremendous subproblems have to be solved to construct the influence matrix. Finally, the modified CSM with domain decomposition, in which the radiative intensity is decomposed into three components, the real wall-related one, the virtual shared interface-related one, and the medium-related one, is proposed. The first two components are solved analytically, and the last one is still solved by the CSM. With such treatments, the computational cost is slightly increased, but the ray effect originated from step-change temperature of medium or step-change optical parameters can be effectively mitigated. Besides, the modified CSM with domain decomposition can also avoid the ray effect due to shadowing singularities. But it should be noted that, in such case, the ray effect due to inhomogeneous spatial distribution of source term may emerge. In conclusion, the CSM combined with domain decomposition is a good alternative method for thermal radiation calculation in complex geome

关键词： Radiative heat transfer Domain decomposition method Spectral methods Ray effect

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Intercomparison of photoacoustic and cavity attenuated phase shift instruments: laboratory calibration and field measurements

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GEOSCIENTIFIC INSTRUMENTATION METHODS AND DATA SYSTEMS 2021年第2期10卷 245-255页

作者： Zhang, Jialuo Chen, Jun Wang, Meng Su, Mingxu Zhou, Wu Varma, Ravi Lou, Shengrong Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China Natl Inst Technol Calicut Dept Phys Calicut 673601 Kerala India Shanghai Acad Environm Sci State Environm Protect Key Lab Cause & Prevent Ur Shanghai 200070 Peoples R China

The study of aerosol optical properties is essential to understand its impact on the global climate. In our recent field measurement carried out in the Gehu area of southwest Changzhou City, a photoacoustic extinctiometer (PAX) and a cavity attenuated phase shift albedo monitor (CAPS-ALB) were used for online aerosol optical properties measurement. laboratory calibration with gas and particle samples were carried out to correct disagreements of field measurements. During particle calibration, we adopted ammonium sulfate (AS) samples for scattering calibration of nephelometer parts of both the instruments, then combined these with number-size distribution measurements in the MIE model for calculating the value of the total scattering (extinction) coefficient. During gas calibration, we employed high concentrations of NO2 for absorption calibration of the PAX resonator and then further intercompared the extinction coefficient of CAPS-ALB with a cavity-enhanced spectrometer. The correction coefficient obtained from the laboratory calibration experiments was employed on the optical properties observed in the field measurements correspondingly and showed good results in comparison with reconstructed extinction from the IMPROVE model. The intercomparison of the calibrated optical properties of PAX and CAPS-ALB in field measurements was in good agreement with slopes of 1.052, 1.024 and 1.046 for extinction, scattering and absorption respectively, which shows the reliability of measurement results and verifies the correlation between the photoacoustic and the cavity attenuated phase shift instruments.

关键词： Calibration

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Effect of flow-deflecting-gap blade on aerodynamic characteristic of vertical axis wind turbines

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RENEWABLE ENERGY 2020年 158卷 370-387页

作者： Zhu, Haitian Hao, Wenxing Li, Chun Ding, Qinwei Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai Peoples R China

In order to improve stall characteristics more effectively or eliminate dynamic stall in a revolution of vertical axis wind turbine, three kinds of novel flow-deflecting-gap (FDG) blade were designed and investigated numerically, including two-side FDG blade, toward-outside FDG blade and toward-inside FDG blade. Firstly, the aerodynamic characteristics of isolated flow-deflecting-gap blade were obtained and its effect was illustrated. Then, the investigation on aerodynamic characteristic of novel SB-VAWT was conducted. The obtained results indicated that compared to clean airfoil, FDG enhances the stalling angle of attack (AOA) by 2 degrees and increases lift-drag ratio at high AOA. Furthermore, FDG significantly decreases the frequency of vortex shedding and greatly reduces amplitude of lift oscillation. Fora vertical axis wind turbine, toward-inside FDG can efficiently decrease the optimal tip-speed ratio and improve the aerodynamic performance at low tip-speed ratio. Additionally, an increase of 10.21% of torque coefficient is caused by toward-inside FDG. Jet flow in FDG towards leading edge offsets the swirling flow over the suction surface and the trailing-edge vortex produced by bluff edge is also weakened or even eliminated by FDG. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： Multi-element airfoil Gap Vertical axis wind turbine Aerodynamic characteristics Computational fluid dynamics

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Reduction kinetics of SrFeO_(3−δ)/CaO∙MnO nanocomposite as effective oxygen carrier for chemical looping partial oxidation of methane

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Frontiers of Chemical Science and engineering 2022年第12期16卷 1726-1734页

作者： Xinhe Wang Liuqing Yang Xiaolin Ji Yunfei Gao Fanxing Li Junshe Zhang Jinjia Wei State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China School of Chemical Engineering and Technology Xi’an Jiaotong UniversityXi’an 710049China Institute of Clean Coal Technology East China University of Science and TechnologyShanghai 200237China Department of Chemical and Biomolecular Engineering North Carolina State UniversityRaleighNC 27695USA

Chemical looping reforming of methane is a novel and effective approach to convert methane to syngas,in which oxygen transfer is achieved by a redox *** lots of efforts have been made to develop high-performance redox materials,a few studies have focused on the redox *** this work,the kinetics of SrFeO_(3−δ)–CaO∙MnO nanocomposite reduction by methane was investigated both on a thermo-gravimetric analyzer and in a packed-bed *** the methane reduction,combustion occurs before the partial oxidation and there exists a transition between *** weight loss due to combustion increases,but the transition region becomes less inconspicuous as the reduction temperature *** weight loss associated with the partial oxidation is much larger than that with *** rate of weight loss related to the partial oxidation is well fitted by the Avrami–Erofeyev equation with n=3(A3 model)with an activation energy of 59.8 kJ∙mol^(‒1).The rate law for the partial oxidation includes a solid conversion term whose expression is given by the A3 model and a methane pressure-dependent term represented by a power *** partial oxidation is half order with respect to methane *** proposed rate law could well predict the reduction kinetics;thus,it may be used to design and/or analyze a chemical looping reforming reactor.

关键词： chemical looping reforming SrFeO_(3−δ) CaO·MnO nanocomposite reduction kinetics Avrami–Erofeyev model pressure-dependent term

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Numerical Simulation of Unsteady flow Control Mechanism of Attached Stationary Or Vibrating Small Cylinder On a Main Cylinder

SSRN

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SSRN 2022年

作者： Huang, Shengxian Hu, Yu Wang, Ying Shanghai key laboratory of multiphase flow and heat transfer of power engineering School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai China National Key Laboratory of Science and Technology on Aerodynamic Design and Research Xi’an710072 China

The phenomena of flow separation and vortex shedding after bluff body are the key to the safety of offshore engineering. To deepen the understanding of the relevant physical mechanism of wake vortex control of the non-equal diameter double cylinder model, simulation was conducted when Re=200 using the SST k-ω turbulence model. The effects of different diameter ratios, position angle, and gap ratio between the double cylinder model on the flow pattern, surface pressure, and wake characteristics of the main cylinder are investigated. Four different forced vibration forms are applied to the small cylinder with the optimum arrangement area, and their influence on the hydrodynamic characteristics of the main cylinder is analyzed. The results show that the main cylinder's vortex shedding and aerodynamic characteristics can be effectively improved by the small auxiliary cylinder arranged in the near wake region of the main cylinder, and there is an optimal position for the small cylinder. In addition, the vibration of the small auxiliary cylinder in the wake area will cause the locking area of the main cylinder and the side vortex shedding on the main cylinder can be better suppressed by using the auxiliary vibration small cylinder with a suitable frequency ratio. © 2022, The Authors. All rights reserved.

关键词： Vortex shedding

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