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Thermo-economic analysis and optimization of a novel self-condensing transcritical CO2 power cycle with ejector refrigeration

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Process Safety and Environmental Protection 2025年 199卷

作者： Xia, Jiaxi Hou, Jingjing Wang, Jiangfeng Lou, Juwei Guo, Yumin School of mechanical and Electrical Engineering Henan Agricultural University Zhengzhou450002 China State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an710049 China

The transcritical CO2 power cycle stands out as a promising approach for the utilization of waste heat and renewable energy, but its practical application is restricted by the condensation challenges of working fluid. To tackle this issue, a novel self-condensing transcritical CO2 power cycle (SC-TCO2PC), which integrates the transcritical CO2 power cycle with an ejector refrigeration cycle, is proposed. Detailed mathematical models are formulated, and parametric study is carried out to illustrate the correlations between the crucial parameters and system performance from both thermodynamic and economic viewpoints. Then a multi-objective optimization is applied to explore the potential for performance enhancement. Furthermore, the comparative analysis of the SC-TCO2PC and the recuperative supercritical CO2 Brayton cycle (SCO2BC) are conducted under optimized conditions. The results demonstrated that the enhanced turbine inlet pressure and temperature positively influence the thermal-economic performance of the SC-TCO2PC. Furthermore, the maximum thermal efficiency of 43.90 %, exergy efficiency of 72.97 % and minimum cost per unit of electricity of 0.0372$/kWh are attainable for the SC-TCO2PC, reflecting the improvements of 4.88 %pt for maximum thermal efficiency, 6.60 %pt for maximum exergy efficiency and a 8.87 % reduction for minimum unit power cost in comparison to the recuperative SCO2BC. In optimum conditions, the SC-TCO2PC is capable of achieving a thermal efficiency of 42.11 % and an exergy efficiency of 70.54 % with the cost per unit of electricity of 0.0440$/kWh. © 2025 The Institution of Chemical Engineers

关键词： Brayton cycle

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MXene-derived Ni/TiO2-x/Ti3C2 catalyst for enhanced photothermal CO2 methanation: Unraveling the roles of photoexcited carriers

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Chemical engineering Journal 2025年 515卷

作者： Sun, Fan Xin, Yu Xing, Xueli Lou, Jiahui Wang, Qiliang Hong, Hui International Research Center for Renewable Energy & State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing100190 China School of Aeronautics and Astronautics University of Chinese Academy of Sciences Beijing100049 China Huaneng Clean Energy Research Institute Beijing102209 China Shandong Institute of Advanced Technology Jinan250100 China Department of Architecture and Built Environment University of Nottingham NottinghamNG7 2RD United Kingdom

Photothermal catalysis has emerged as a promising approach for CO2 conversion, which combines photo and thermal energy to drive catalytic reactions efficiently. While light can lower activation barriers and enhance reaction rates, the interplay between light and heat within the catalytic framework remains largely unexplored. In this study, we investigate the critical role of photogenerated carriers in enhancing catalytic performance under solar irradiation, unraveling their contribution to the CO2-to-CH4 conversion process. A multilayer accordion-like Ni/TiO2-x/Ti3C2 catalyst, which exhibits excellent photothermal and photoelectric response characteristics was fabricated for efficient photothermal CO2 methanation. Experimental results demonstrated that introduction of light during thermal catalysis markedly enhanced the CO2 conversion rate, with a 55 % increase achieved at 548 K. Furthermore, the required temperature for maximum CO2 conversion rate was reduced by 50 K compared to the thermal-driven process. Meanwhile, the effects of concentrated ratio and incident wavelength on CO2 conversion were also examined, revealing a synergistic effect between photogenerated carriers and thermal energy. Further characterizations, including steady-state and transient photoluminescence spectroscopy, in-situ XPS, in-situ EPR, in-situ DRITFs, were employed to elucidate the enhancement mechanisms of photogenerated carriers in the catalytic reaction. At the same time, an outdoor experimental prototype was developed to verify the feasibility of photogenerated carrier-thermal synergistically driven CO2 methanation. Our findings provide valuable insights into the role of photo-generated carriers in photothermal CO2 methanation, offering new perspectives for the design of efficient photothermal catalysts and advancing solar catalytic CO2 conversion technologies. © 2025

关键词： Activation energy

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CdS nanocrystallites sensitized ZnO nanorods with plasmon enhanced photoelectrochemical performance

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Chinese Chemical Letters 2019年第12期30卷 2363-2367页

作者： Li Cai Yuanchang Du Xiangjiu Guan Shaohua Shen International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering (MFPE) Xi’an Jiaotong University (XJTU)

A novel architecture of CdS/ZnO nanorods with plasmonic silver(Ag) nanoparticles deposited at the interface of ZnO nanorods and CdS nanocrystallites,was designed as a photoanode for solar hydrogen generation,with photocurrent density achieving 4.7 mA/cm^2 at 1.6 V(***),which is 8 and 1.7 times as high as those of pure ZnO and CdS/ZnO nanorod films,***,with optical absorption onset extended to^660 nm,CdS/Ag/ZnO nanorod film exhibits significantly increased incident photo-tocurrent efficiency(IPCE) in the whole optical absorption region,reaching 23.1% and 9.8% at 400 nm and500 nm,*** PEC enhancement can be attributed to the one-dimensional ZnO nanorod structure maintained for superior charge transfer,and the extended visible-light absorption of CdS ***,the incorporated plasmonic Ag nanoparticles could further promote the interfacial charge carrier transfer process and enhance the optical absorption ability,due to its excellent plasmon resonance effect.

关键词： ZnO nanorods Plasmonic Ag nanoparticles CdS nanocrystallites Photoelectrochemical water splitting Synergistic effect

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Sacos-Plate: A New Thermal-Hydraulic Subchannel Analysis Code for Plate Type Fuel Assemblies

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SSRN 2023年

作者： Sun, Ruiyu Wang, Jianjun Wang, Jinshun Chen, Ronghua Jiang, Xing Tian, Wenxi Qiu, Suizheng Su, Guanghui Gui, Minyang Harbin Engineering University China School of Nuclear Science and Technology Xi’an Jiaotong University Shaanxi Xi’an710049 China Shaanxi Key Lab. of Advanced Nuclear Energy and Technology Xi’an Jiaotong University China State Key Lab. of Multiphase Flow in Power Engineering Xi’an Jiaotong University China Shanghai Nuclear Engineering Research Design Institute Shanghai China

Over the past few decades, plate-type fuel elements have been widely used in advanced research reactors, small modular pressurized water reactors, production reactors, etc., with the advantages of compact structure arrangement, good heat transfer characteristics and high fuel consumption. Currently, a thermal-hydraulic subchannel analysis code, namely SACOS-PLATE code, was newly designed to satisfy the calculation of different types of plate fuel elements under various steady-state operating conditions. Based on the original SACOS code, this updated version modifies the flow distribution model, the plate heat conduction model, the heat distribution model as well as the flow heat transfer model, and then realizes the simulation of the special thermal-hydraulic phenomena of the fuel and the rectangular flow channel. In this present study, the RA-6 experimental data was used to validate the code, and the simulation calculation was performed on the JRR-3 research reactor, which proved the good computing capability of SACOS-PLATE code. © 2023, The Authors. All rights reserved.

关键词： Plates (structural components)

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Comparison of chemical composition and acidity of size-resolved inorganic aerosols at the top and foot of Mt. Hua, Northwest China: The role of the gas-particle distribution of ammonia

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Science of the Total Environment 2023年 905卷 166985页

作者： Feng, Qiao Liu, Haijiao Dai, Wenting Cao, Yue Shen, Minxia Liu, Yali Qi, Weining Chen, Yukun Guo, Xiao Zhang, Yifan Li, Lu Zhou, Bianhong Li, Jianjun State Key Laboratory of Loess and Quaternary Geology Key Lab of Aerosol Chemistry and Physics Institute of Earth Environment Chinese Academy of Sciences Xi'an710061 China College of Geography and Environment Baoji University of Arts and Sciences Shaanxi Key Laboratory of Disaster Monitoring and Mechanism Simulation Baoji721013 China Xi'an Institute for Innovative Earth Environment Research Xi'an710061 China National Observation and Research Station of Regional Ecological Environment Change and Comprehensive Management in the Guanzhong Plain Shaanxi China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

Aerosol pH is not only a diagnostic indicator of secondary aerosol formation, but also a key factor in the specific chemical reaction routes that produce sulfate and nitrate. To understand the characteristics of aerosol acidity in the Mt. Hua, the chemical fractions of water-soluble inorganic ions in the atmospheric PM2.5 and size-resolved particle at the top and foot of Mt. Hua in summer 2020 were studied. The results showed the mass concentrations of PM2.5 and water-soluble ions at the foot were 2.0–2.6 times higher than those at the top. The secondary inorganic ions, i.e., SO42−, NO3−, and NH4+ (SNA) were 56 %–61 % higher by day than by night. SO42− was mainly distributed in the fine particles (Dp 3− showed a unimodal size distribution (peaking at 0.7–1.1 μm) at the foot and a bimodal (0.7–1.1 μm and 4.7–5.8 μm) size distribution at the top. At the top site, the distribution of NO3− in coarse particles (> 2.1 μm) was mainly attributed to the gaseous HNO3 volatilized from fine particles reacting with cations in coarse particles to form non-volatile salts (such as Ca(NO3)2). The pH values of PM2.5 were 2.7 ± 1.3 and 3.3 ± 0.42 at the top and foot, respectively. NH4+/NH3(g) plays a decisive role in stabilizing aerosol acidity. In addition, the increase of the liquid water content (LWC) at the foot facilitates the gas-particle conversion of NH3, while the H+ concentration was diluted, resulting in a decrease in acidity at the foot. NH4+/NH3 had good linear correlations with SO42−, NO3−, and LWC during the daytime at both sites, indicating that SO42−, NO3−, and LWC together affect the gas-particle distribution of ammonia by day: however, the effect of LWC at night was not evident. © 2023

关键词： Ammonia

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Thermal and film dynamics of multi-nozzle flash spray cooling towards large area and non-uniform heat source

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Thermal Science and engineering Progress 2025年 63卷

作者： Lin, Xiang-Wei Wang, Xu-Dong Zhou, Zhi-Fu Zhu, Dong-Qing Xu, Wen-Wei Zhu, Hai State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Huawei Technologies Co. Ltd. Shenzhen China

Thermal management poses a crucial challenge to the operational reliability of high-power devices which characterized by large area and uneven heat sources. Flash spray, as one of the start-of-the-art technologies, satisfies the requirements of rapid heat removal and superior droplet breakup effects. This study aims to investigate the liquid dynamics and heat transfer characteristics of multi-nozzle flash spray on a non-uniform heat flux surface. Here, the Euler-Lagrangian method is coupled to account for the gas-droplet interactions, and the Lagrangian wall-film is applied to describe the liquid film evolution. The effects of spray height and nozzle number are systematically discussed in terms of velocity, liquid film thickness, average surface temperature, and temperature non-uniformity. Results reveal that the enhanced spray-to-spray interaction can greatly alter liquid film distribution, which in turn affects the heat transfer efficiency. Notably, while increasing spray coverage improves thermal contact area, it exhibits a non-linear relationship with temperature reduction, showing an optimal spray height and nozzle number for minimizing average temperature and temperature non-uniformity. The main contribution of present work lies in its in-depth analysis of multi-nozzle flash spray on large area and uneven heating surface, which is prevalent in industrial applications buy underexplored in prior works. These findings are expected to offer actionable guidelines for understanding complex spray cooling mechanisms and designing efficient thermal management systems. © 2025 Elsevier Ltd

关键词： Film cooling

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Boiling of Water Droplet in Glass-Oil-Water multiphase System

SSRN

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SSRN 2022年

作者： He, Xiaotian Cheng, Yiwei Xu, Jinliang Yu, Xiongjiang Xie, Jian Ma, Xiaojing Ren, Yong Beijing Key Laboratory of Multiphase Flow and Heat Transfer for Low Grade Energy Utilization North China Electric Power University Beijing102206 China Key Laboratory of Power Station Energy Transfer Conversion and System of Ministry of Education North China Electric Power University Beijing102206 China Research Group for Fluids and Thermal Engineering University of Nottingham Ningbo China Ningbo315100 China

Boiling of a volatile droplet in a non-volatile liquid becomes complex due to various interface interactions in a solid-liquid-liquid system. Available studies reported explosive boiling and attributed the phenomenon to heterogeneous nucleation due to solid-liquid contact. Here, we investigate boiling of ~2 mm diameter water droplet in a silicon oil pool with glass container. Two transition temperatures are observed, with one as the transition from evaporation to boiling (122.5 o C), and the other as the transition from bubble growth in oil side to that in both oil and water side (160.0 o C). Correspondingly, four boiling modes of evaporation (E), boiling in water (BIW: bubble nucleation at glass-water interface and growth inside drop), boiling in oil (BIO: nucleation at oil-water interface and growth in oil), and boiling in oil and water (BIOW: nucleation at oil-water interface and growth in oil and water), are identified. For the first time, boiling bifurcation is found for drop boiling in a three-phase system. For oil temperature T b in the range of (122.5~160.0) o C, boiling mode switches in between BIW and BIO. On the contrary, for T b beyond of 160.0 o C, either BIW or BIOW occurs. This bifurcation is explained by the fact that a droplet prefers to choose smaller activation energy between that for bubble nucleation at solid-water interface and that for bubble nucleation at oil-water interface. Interfacial instabilities are analyzed to explain why BIOW boils more violently than BIW. Our work presents a comprehensive understanding of droplet boiling in the three-phase system. © 2022, The Authors. All rights reserved.

关键词： Bifurcation (mathematics)

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A 3d Ptco Degradation Model for Long-Term Performance Prediction of a Scaled-Up Pemfc Under Constant Voltage Operation

SSRN

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SSRN 2023年

作者： Yang, Yunjie Bai, Minli Zhou, Zhifu Wu, Wei-Tao Zhao, Jian Wei, Lei Li, Yang Li, Yubai Song, Yongchen Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education Dalian University of Technology Dalian116024 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'An710049 China School of Mechanical Engineering Nanjing University of Science and Technology Nanjing210094 China Center for Advanced Vehicular Systems Mississippi State University Starkville39762 United States Department of Mechanical and Energy Engineering Southern University of Science and Technology Shenzhen518055 China

The non-uniform distribution of reactants, pressure, temperature, and reaction rate, in a scaled-up proton exchange membrane fuel cell (PEMFC) can lead to different catalyst degradation rate, impacting the long-term performance of PEMFCs. However, the local catalyst degradation behaviors in a PEMFC stack have not yet been fully understood due to the lack of experimental approaches and catalyst degradation model. In the present study, a numerical model is established for a 200 cm2 commercial-sized PEMFC stack with realistic anode and cathode flow fields. PtCo is employed as the cathode catalyst, and a 3D PtCo catalyst degradation model is developed to analyze the non-uniform evolution of the electrochemical active surface area (ECSA), current density, and Co2+ in the catalyst layers under the constant voltage conditions. The modeling results demonstrated that catalyst degradation is more severe downstream as well as under land of the cathode flow field, and the cathode catalyst layer (CCL) is the area most contaminated by the Co2+. The non-uniform catalyst degradation as well as Co2+ contamination increased the activation losses and local oxygen transport resistance. The catalyst degradation leads to a total power loss of 43.3% after 80,000 hours operation. The aging model provides a better understanding for large scale PEMFC stacks regarding its nonuniform PtCo degradation and can assist the future design of commercial PEMFCs with better lifetime. © 2023, The Authors. All rights reserved.

关键词： Proton exchange membrane fuel cells (PEMFC)

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Strong Photo-Thermal Coupling Effect Boosts Co2 Reduction into Ch4 in a Concentrated Solar Reactor

SSRN

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SSRN 2023年

作者： Li, Naixu Xu, Lei Ren, Yuqi Liu, Maochang Zhu, Fengfan Cheng, Miao Zhou, Jiancheng Chen, Wenshuai Wang, Ke Wang, Nan School of Chemistry and Chemical Engineering Southeast University No.2 Dongnandaxue Road Jiangsu Nanjing211189 China International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University No.28 Xianning West Road Shaanxi Xi'An710049 China Key Laboratory of Bio-Based Material Science and Technology Ministry of Education Northeast Forestry University No. 26 Hexing Road Harbin150040 China

This study is dedicated to solving the problems of low energy utilization and low yield in the conventional photocatalytic CO2 reduction process. In this work, a novel concentrated solar (light) reactor was established to improve solar energy utilization efficiency and CO2 conversion rate by concentrating light and heat (that is, by converting light into heat). The TF@TNT/0.4CoOx-0.1CuO monolithic photocatalyst based on titanium foam was designed and prepared. The results showed that the light intensity increased by ~10.6 times (from 400 mW/cm2 to 4266 mW/cm2) while the yield of CH4, the product of CO2 reduction driven by photo-thermal coupling effect, increased by ~220 times (from 0.53 µmol/cm2 to 116.4 µmol/cm2) in the concentrated solar (light) reactor. The results of CH4 yield, electrochemical measurement, and apparent activation energy calculation were investigated in the concentrator reactor under the conditions of concentrated and non-concentrated irradiation of simulated sunlight in different wavelength ranges. It can be found that the concentrated light and the induced photo-thermal coupling effect can significantly reduce the reaction barrier (from 41.62 to 31.51 kJ/mol) and improve the conversion efficiency of solar energy to chemical energy by ~15 times. This provides a potentially feasible method for efficient and green utilization of CO2 driven by solar energy. © 2023, The Authors. All rights reserved.

关键词： Solar energy

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Insight into the Interconversions of Three-Phase Products Through the Supercritical Water Gasification of Bark

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SSRN 2023年

作者： Ge, Hui Yi, Lei Huang, Yong Peng, Pai Cao, Wen Chen, Yunan Qi, Xingang Guo, Liejin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University No.28 Xianning West Road Xi'An710049 China International Institute for Innovation Jiangxi University of Science and Technology Jiangxi 341000 China Suzhou Academy Xi’an Jiaotong University No.99 Ren’ai Road Jiangsu Suzhou215123 China

The clean and efficient utilization of biomass waste for hydrogen production conforms to social development in the future. In this work, hydrogen production from supercritical water gasification (SCWG) of fir bark (FB) was investigated systematically at various reaction temperatures (500–750 °C), feedstock concentrations (5%–15%), and retention time (0–40 min). The gaseous, liquid, and solid products were analyzed comprehensively to determine the gasification mechanism. The results demonstrated that FB was the alternative feedstock for hydrogen production. The maximum CE and H2 selectivity of 95.34% and 0.99 were obtained at 700 °C-5%-40 min. High reaction temperature and prolonging retention time accelerated the conversions of phenolic compounds in liquid products and functional groups in solid products. High feedstock concentration also resulted in the bond-making between functional groups in solid products. The reaction mechanism was proposed based on the components of gaseous and liquid products and the variations of functional groups in solid products. © 2023, The Authors. All rights reserved.

关键词： Hydrogen production

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