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The Mechanism of CO2 Hydrate Formation by the Synergistic Effect of Kinetic Promoters

ENERGY & FUELS 2024年第21期38卷 20851-20860页

作者： Liu, Ni Leng, Jing Cui, Mengxue 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

CO2 hydrate technology holds immense promise for advancing carbon neutrality through effective carbon capture. In this paper, different mass concentrations of fullerene C- 60 and Sodium Lignosulfonate (SL), two potential kinetic hydrate promoters, were investigated. Operating at 3.5 MPa and 273.65 K, the investigation reveals intriguing findings. C- 60, as a nanoparticle, showed the best promotion effect at a low concentration (0.01 wt %), with a gas storage capacity of 50.63 V/V. SL, as a macromolecular material, was best promoted at a moderate concentration (0.1 wt %) with a gas storage capacity of 86.92 V/V. Notably, the combination of C- 60 and SL demonstrated a powerful synergistic effect. The best combination was 0.01 wt % C- 60 with 0.1 wt % SL experimental group. The induction time was significantly shortened to 60 min, and the gas storage capacity was enhanced to 110.80 V/V, which markedly enhanced the promotion effect. At the same time, the nature of the solution and the principles of its formation were explored, opening up new possibilities for the practical use of carbon capture.

关键词： Carbon capture and utilization

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Performance and Sizes of sCO_(2)Multistage Axial Compressors at Various power Capacities

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Journal of Thermal Science 2025年第2期34卷 352-373页

作者： WANG Tianze XU Jinliang ZHENG Haonan QI Jianhui Beijing Key Laboratory of Multiphase Flow and Heat Transfer for Low Grade Energy Utilization North China Electric Power UniversityBeijing100026China Key Laboratory of Power Station Energy Transfer Conversion and System(North China Electric Power University) Ministry of EducationBeijing102206China School of Energy and Power Engineering Shandong UniversityJi’nan250061China

The supercritical carbon dioxide(sCO_(2))cycle can be powered by traditional as well as clean *** help users obtain more accurate results than the literatures with pre-set compressor efficiency,we proposed a complete model to establish a link between the performance,sizes of compressors and parameters such as power W_(C),inlet temperature T_(in),inlet pressure P_(in)and pressure ratioε.Characteristic sizes of compressors l_(c),profile loss Y_(p)and clearance loss Ycl are all proportional to powers of W_(C)with powers of 0.5,-0.075 and-0.5 to 0 respectively;the scaling laws are constant in the range of capacities from 20 MW to 200 *** compressor isentropic efficiencyη_(tt)grows as the W_(C)increases,and the curves become *** efficiency improves over the full power range when the speed is changed from standard speed to the optimal speed;theη_(tt)curves turn soft as the n *** the P_(in)and T_(in)approach the critical point,theη_(tt)*** efficiency follows a parabolic curve as theεincreases,this parabolic distribution results from the tradeoff between the change in losses and the pressure distribution of ***η_(tt)versus P_(in),T_(in)andεrelations are similar at various capacities because of insignificant changes in the distribution of *** efficiency maps facilitate the estimation of system performance,while scaling law for irreversible losses and characteristic lengths,along with constant criterion analyses,aid in comprehending the characteristics of compressors across various capacities.

关键词： sCO_(2)cycle compressor efficiency irreversible losses scaling laws

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Enhancing aerodynamic performance of vertical axis wind turbines using bionic airfoils inspired by swordfish tail

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MECCANICA 2024年第11期59卷 2059-2080页

作者： Song, Hui Ye, Zhou Wang, Ying Li, Chun 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

In this work, a pioneering approach is proposed to enhance the efficacy of vertical axis wind turbines within the aerodynamic field. This innovative method involves integrating a bionic airfoil, inspired by the tail fin of a swordfish, along the trailing edge of the airfoil. To evaluate the impact of these biomimetic airfoils on wind turbine functionality, applications such as numerical simulations facilitated by computational fluid dynamics (CFD) and design of experiments (DOE) were employed. The primary objective of this study is to mitigate the flow separation phenomenon that occurs when wind turbines operate at low tip speed ratios (TSR < 4). The results indicate that the addition of the bionic tail delays the angle at which the peak torque appears, and enhances positive torque generation effectively within the phase angle range of 60 degrees to 150 degrees, suggesting successful suppression of the flow separation phenomenon. The presence of the tail also postpones the occurrence of dynamic stall, particularly near the trailing edge of the airfoil, and reduces losses associated with the expansion and shedding of dynamic stall vortices. As the tip speed ratio increases, the average power coefficient of the bionic airfoil exhibits a positive trend. Notably, at a tip speed ratio of 2.63, a significant increase in the average power coefficient of approximately 17% was observed. The analysis of the downstream wake of the wind turbine reveals that the bionic tail enhances the speed loss in the wake. This indicates that the blades can generate greater lift at a lower tip speed ratio, allowing the vertical axis wind turbine to operate effectively at low wind speeds, particularly in urban areas with significant development potential.

关键词： VAWT flow control CFD Aerodynamic performance

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Photovoltaic-based energy system coupled with energy storage for all-day stable PEM electrolytic hydrogen production

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RENEWABLE ENERGY 2023年第1期209卷 53-62页

作者： Gu, Xufei Ying, Zhi Zheng, Xiaoyuan Dou, Binlin Cui, Guomin Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

Photovoltaic (PV) power generation coupled with proton exchange membrane (PEM) water electrolysis favors improving the solar energy utilization and producing green hydrogen. But few systems proposed focus on achieving all-day stable hydrogen production, which is important for the future large-scale hydrogen utilization. Herein, a PV-Battery-PEM water electrolysis system for hydrogen production was constructed. An energy man-agement strategy (EMS) was proposed to achieve the goal of all-day stable hydrogen production, improve energy utilization efficiency and reduce light discard rate. The PV power generation system, battery system and PEM electrolyzer for hydrogen production system were first established by Matlab/Simulink platform. Then, the overall PV-Battery-PEM electrolyzer system for hydrogen production was constructed, and the effectiveness of EMS was verified. The energy efficiency of the system under different working conditions with and without battery for energy storage was analyzed. The results show that the proposed energy management strategy can meet the purpose of all-day stable hydrogen production. Under the same working conditions, the energy effi-ciency of the system with battery for energy storage increases by 2-4% compared with the system without battery for energy storage, which indicates that the addition of energy storage can improve the energy utilization and reduce the light discarding.

关键词： Hydrogen production Photovoltaic power generation Proton exchange membrane water electrolysis Energy storage Energy management strategy System efficiency

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Enhancing vertical-axis tidal turbines with strategic superhydrophobic surfaces for optimized aerodynamic and self-starting performances

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OCEAN engineering 2025年 324卷

作者： Yin, Dawei Sun, Jinjing Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China

As observation and research on nature continue to progress, bionic and hydrophobic surface drag reduction is gaining increasing popularity among researchers. The application of bionic principles and hydrophobic surface technologies in the field of fluid dynamics has opened up new avenues for enhancing the performance of various engineering systems, including vertical-axis tidal turbines (VATTs). By mimicking the natural mechanisms observed in certain species, such as the lotus effect, researchers have been able to develop superhydrophobic surfaces (SHSs) that significantly reduce drag in fluid environments. Traditionally, SHSs have been applied uniformly across the entire surface of an airfoil. However, this study takes a more nuanced approach by investigating the impact of SHS application at different positions on an airfoil. Through numerical simulations, the study explores how variations in the distribution of SHSs can influence the power coefficient (Cp). The study's results are highly revealing. The leading edge and the inner side of the airfoil have a significant effect on the power coefficient, and they substantially affect the optimal tip speed ratio (TSR) offset. For example, the leading_SHS significantly enhances the power coefficient at low TSRs, especially at TSR =1.68. For this TSR, the power coefficient increases by 38.2%, higher than the 34.8% increase achieved by all_SHS. This indicates that the strategic placement of SHSs can lead to significant performance improvements without the need for uniform application, which could potentially reduce material costs and maintenance requirements. Furthermore, the diminished effectiveness of trailing_SHS and outer_SHS can be attributed to several factors, such as the exacerbation of flow separation by trailing_SHS and the impact of the separation vortex structures at the leading edge. Some research has highlighted the pivotal role of SHS application in enhancing the self-starting performance of a turbine. This

关键词： flow separation

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Numerical simulation on flow boiling heat transfer characteristics of R513A in the horizontal microfin tubes

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APPLIED THERMAL engineering 2025年 260卷

作者： Zhang, Suhan Tao, Leren Huang, Lihao Jin, Cheng Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

To address the growing demand for high-efficiency heat exchangers in refrigeration, air conditioning, and heat pump systems, this study investigates the boiling heat transfer performance of R513A (an environmentally friendly azeotropic refrigerant) in horizontal microfin and smooth tubes with a 5.89 mm ID. Using 3D transient simulations, the tubes were analyzed under operating conditions of a mass flux of 50 kg/(m2 center dot s) and a saturation temperature of 5 degrees C. The simulation results were validated against experimental data within a +/- 10 % error margin, confirming the reliability of model. At the constant mass flux, both the microfin and smooth tubes exhibited predominantly wavy-stratified flow, where surface tension dominated bubble flow. Gravity effects became more pronounced in slug, plug, and wavy-stratified flows. Structural parameters of microfin tubes, such as helical angle, fin height and number of fins, significantly affected flow boiling heat transfer. Increasing the helical angle had limited effect on enhancing boiling heat transfer performance. Microfin tube 4# (helical angle of 28 degrees) exhibited an 11.27 % reduction in the boiling heat transfer coefficient compared to microfin tube 2#, due to the uneven distribution of liquid droplets in the vapor phase further reduced liquid film continuity and thickness. Microfin tube 5# (fin height of 0.30 mm) achieved an average mainstream velocity 1.36 times that of tube 2# (fin height of 0.17 mm), enhancing heat transfer. Conversely, microfin tube 6# with 54 fins showed local drying, negatively impacting its heat transfer efficiency. In summary, microfin tube 5# exhibited the optimal heat transfer characteristics.

关键词： CFD Simulation R513A flow boiling Geometric structure Two phase flow flow pattern

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Efficient anodic biochar oxidation over three- dimensional self-support nickel-iron nanosheet on nickel foam in biochar-assisted water electrolysis for hydrogen production

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INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 2023年第3期48卷 894-908页

作者： Du, Yueyue Ying, Zhi Zheng, Xiaoyuan Dou, Binlin Cui, Guomin Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

Biochar-assisted water electrolysis (BAWE) facilitates the high-value utilization of biomass and energy-saving hydrogen production. However, the BAWE efficiency is hindered by slow kinetics of biochar oxidation reaction (BOR) at anode. Herein, to improve the overall efficiency of BAWE, three-dimensional porous nanosheets modified on nickel foam (Ni1Fe2- LDH@NF) was developed for BOR, and its mechanism was identified. Impressively, the BAWE system exhibited remarkable activity, including a low potential of 1.387 V vs. RHE for BOR over as-synthesized electrocatalyst at current density of 10 mA center dot cm-2, and excellent long-term stability over 20 h at a high current density of 200 mA center dot cm-2 and after 1000 CV cycles. The required electricity input was 3.29 kWh center dot Nm-3H2 at 10 mA center dot cm-2 for BAWE with Ni1Fe2-LDH@NF toward BOR. In addition, the reaction mechanism of BOR including biochar direct oxidation on the electrocatalysts surface and indirect oxidation in the electrolyte was deduced, according to the surface chemistry and composition changes of electrocatalysts and biochar, as well as the products. This work provides an effective strategy towards the enhancement of the BOR process by designing the binder-free electrocatalysts, and facilitates the development of BAWE for energy-efficient hydrogen production and biomass utilization.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Biochar-assisted water electrolysis (BAWE) Biochar oxidation reaction (BOR) Nickel-iron nanosheets Hydrogen

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Study on the Destruction of PCDD/Fs and Synergistic Solidification of Heavy Metals in Fly Ash by Low-Temperature Pyrolysis with the Assistant of N-Doped Hierarchical Porous Carbon

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PROCESSES 2025年第4期13卷 1202-1202页

作者： Yue, Mingqi Wang, Qiulin Wang, Haonan Wang, Xiaoyiran Jin, Jing Liu, Dunyu Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

Highlights What are the main findings? The low-temperature destruction of PCDD/Fs during FA pyrolysis is enhanced by NHPC. More lower-chlorinated PCDD/Fs can be decomposed in the presence of NHPC. The heavy metals in fly ash are synergistically solidified with the aid of NHPC. What is the implication of the main finding? NHPC regulates the structure properties and the chemical environment of fly ash. The addition of NHPC provides a novel research approach for the synergistic disposal of PCDD/Fs and heavy metals in fly *** What are the main findings? The low-temperature destruction of PCDD/Fs during FA pyrolysis is enhanced by NHPC. More lower-chlorinated PCDD/Fs can be decomposed in the presence of NHPC. The heavy metals in fly ash are synergistically solidified with the aid of NHPC. What is the implication of the main finding? NHPC regulates the structure properties and the chemical environment of fly ash. The addition of NHPC provides a novel research approach for the synergistic disposal of PCDD/Fs and heavy metals in fly *** There is an urgent need for energy-efficient disposal and resource utilization of the fly ashes from municipal solid waste incineration (MSWI). The low-energy pyrolysis-based detoxification of is a prerequisite for the harmless treatment and sustainable utilization of the fly ashes. In this study, the nitrogen-doped hierarchical porous carbon (NHPC) was prepared from the biomass-derived corn cobs and used to enhance the low-temperature destruction of PCDD/Fs in the MSWI fly ash. On thermal treatment in pure nitrogen (referring to pyrolysis in) at 350 degrees C for 30 min, the removal efficiencies of PCDD/Fs in fly ash based on mass (eta mass) and TEQ (eta TEQ) are 87.4% and 76.2%, respectively. After 5 wt.% NHPC is added in fly ash, the eta mass and eta TEQ values can be increased to 94.9% and 90.2%. The NHPC can enhance the decomposition and inhibit the regeneration of PCDD/Fs in fly ash, for the NHPC can regulate the st

关键词： energy-efficient pyrolysis fly ash PCDD/Fs heavy metals N-doped hierarchical porous carbon

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Numerical simulation on the condensation heat transfer and flow characteristics outside smooth and enhanced tubes

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APPLIED THERMAL engineering 2025年 258卷

作者： Cheng, Jian Tao, Leren Li, Meng Jin, Cheng Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

Most of the current studies only conducts two-dimensional simulations of condensation heat transfer and flow outside enhanced tubes, which cannot accurately reflect the flow and heat transfer characteristics of liquid film outside enhanced tubes. In order to provide theoretical support for the design optimization of enhanced tubes, this study adopts the VOF multiphase model and Lee condensation model to simulate the condensation heat transfer(HTC) of refrigerants outside smooth and enhanced tubes. The instantaneous film flow characteristics of the liquid film outside the horizontal smooth and enhanced tubes are analyzed, and the thickness of the liquid film and the relationship with the condensation heat transfer coefficient of the smooth and enhanced tubes under different working conditions are calculated. The refrigerants are compared under the same working conditions, and the results are shown: The simulation results are in good agreement with the experimental data and the Nusselt analytical solution, and the error is all within 15%;the distribution of liquid film is highly sensitive to the magnitude of local condensation heat transfer coefficients, and the condensation HTC outside the enhanced tube is approximately six times of that of smooth tube. Combining the distribution of the liquid film and the thermophysical properties of the refrigerants, it was determined that R410A has the highest HTC, while R1234yf has the lowest HTC.

关键词： Condensation heat transfer coefficient CFD VOF Liquid film

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Numerical study on the wake structures of a sphere in linearly stratified flow

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JOURNAL OF VISUALIZATION 2025年第1期28卷 97-113页

作者： Shi, Liu Liu Wei, Na Chen, Er Yun 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

In this study, numerical simulations have been carried out to evaluate the influence of internal Froude number (Fr) on the wake characteristics of a sphere in linearly stratified flow. Five models with different levels of Fr (Fr = 0.05, 0.2,0.25,0.5 and 1) at a Reynolds number of Re = 3700 have been selected for comparative study. UDF (User Defined Function) is employed to establish linear density stratification. The influences of stratification on wake characteristics are studied by analyzing the wake patterns, vortical structures, velocity distributions, and lee waves. The results of the study demonstrate that reduced Fr values lead to heightened vertical suppression of the near wake, while increased stratification prompts a transformation of the wake's three-dimensional coherent structures towards quasi-two-dimensionality. Furthermore, the presence of stratification notably impacts the length and amplitude of the lee wave.

关键词： Linearly stratified flow Internal Froude number Wake Lee wave

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