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Process analyses on sorption-enhanced electrified steam methane reforming for near-zero emission hydrogen production with CO2 capture by calcium looping thermochemical reaction

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APPLIED ENERGY 2025年 385卷

作者： Song, Huchao Zhang, Xinyue Lin, Xiaolong Bian, Hao Liu, Yinhe Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

The predominant hydrogen production method is steam methane reforming, which generates substantial CO2 emissions from both the reforming reaction and the combustion required to drive the process. Sorption-enhanced steam methane reforming (SESMR) enables the in-situ CO2 removal during the reforming reaction, enhancing hydrogen yield. Replacing combustion with renewable electricity for reforming reaction can eliminate combustion-related emissions and flue gas heat loss. However, the intrinsic randomness, intermittency, and instability of renewable electricity present significant challenges to maintaining continuous and stable operation. This study introduces a process that innovatively leverages the mass and energy flow matching characteristics of the calcium looping with renewable electricity driving calcination, thermochemical energy storage, and sorptionenhanced steam methane reforming, thereby establishing the sorption-enhanced electrified steam methane reforming (SEESMR) process. The SEESMR exploits the dual functions of sorbent as both an energy carrier and a CO2 carrier. Renewable electricity facilitates calcination in the regenerator, storing energy in the form of chemical energy and sensible heat. This stored energy is subsequently utilized in the reformer during CO2 adsorption, providing the requisite energy to drive methane reforming and produce hydrogen. First and second law analyses indicate that SEESMR demonstrates a 7.90 percentage point improvement in thermal efficiency compared to SESMR through the substitution of combustion heating with electric heating and a high-efficiency heat recovery. Additionally, this modification reduces exergy losses by up to 53.2 % through elimination of combustion in SESMR. Furthermore, SEESMR enables continuous hydrogen production from renewable elec- tricity, achieves a 35 % cost reduction within the current fuel pricing framework in China compared to direct electric heating methane reforming. This study may provide a st

关键词： Sorption enhanced steam methane reforming Electrified steam methane reforming Hydrogen production Thermodynamic optimization Techno-economic analysis

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Effect of laser spot diameter on mass transfer mechanisms in photoelectrochemical water splitting

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PHYSICS OF FLUIDS 2025年第4期37卷

作者： Chi, Jiayang Tao, Leqing Xu, Qiang Tang, Fanyu Guo, Liejin Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Clarifying the mass transfer mechanism in the evolution of bubbles on the surface of photoelectrodes can help break the shackles that limit the efficiency of photoelectrochemical water splitting. This paper utilized an electrochemical workstation and a high-speed camera to synchronously record the evolution of oxygen bubbles on the surface of thin-film catalysts and their electrochemical signals. The nucleation and detachment characteristics of bubbles at different spot diameters were investigated, and the gas evolution efficiency and mass transfer coefficient were calculated. As the spot diameter increases, the nucleation potential, terminal rising velocity, and growth duration of the bubbles show an increasing trend, and the increase in the gas evolution efficiency reflects an increase in the proportion of gas molecules entering the bubbles. According to the calculations using the mass transfer model, the mass transfer coefficient decreases as the spot diameter increases. The mass transfer coefficient increased by a factor of 1.46 when the spot diameter decreased from 1176 to 700 mu m. Our study showed that reducing the spot diameter can effectively improve the mass transfer of gaseous products on the photoelectrode surface and facilitate the nucleation and rapid detachment of bubbles.

关键词： High speed cameras

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Liquid film behavior upon an oblique jet impinging on a solid wall

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PHYSICS OF FLUIDS 2025年第3期37卷

作者： Fu, Hang Jiang, Jiawei Li, Yuan Liu, Chuansheng Tang, Chenglong Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

This work numerically explores the effect of different Reynolds numbers, inclination angles, and wall surface roughness on liquid film behaviors upon a jet impinging on a solid wall. The Volume of Fluid approach with contact angle correction, in conjunction with surface roughness estimation based on boundary layer flow, was applied. A new model for predicting the geometry of the liquid film with full consideration of flow characteristics and jet conditions was proposed. Results show that the present model predicts the maximum liquid film width, the starting point of the liquid film, and the liquid film morphology with improved accuracy. With an increase in jet Reynolds number from 1600 to 3600, the maximum width of the liquid film increases from r/D = 11.8 to 16.5, and the maximum thickness increases from h/D = 1.2 to 1.9. The pressure coefficient shows little change, while the skin friction coefficient decreases with higher Reynolds number. The variation of alpha from 45 degrees to 75 degrees shows a weak influence on the film thickness distribution in the thin layer zone. Increasing the injection angle results in a downward shift (r/D = 0.8) of the maximum pressure coefficient. The maximum pressure coefficient increases by about 25%, while the maximum skin friction coefficient increases by about 55% with a higher injection angle. With an increase in surface roughness, the maximum width of the liquid film increases about 10%, the maximum pressure coefficient by about 20%, and the maximum skin friction coefficient by about 26%.

关键词： Reynolds number

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Numerical investigation on gasification characteristics of irregularly-shaped coal particles in supercritical water for hydrogen production

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INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 2025年 124卷 304-317页

作者： Zhao, Shuaiqi Zhang, Rui Huang, Han Zhao, Kunpeng Bai, Bofeng Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

The morphology of coal particles plays a crucial role in the supercritical water gasification (SCWG) of coal for hydrogen production, as it significantly influences both mass and heat transfer processes. Most existing studies assume coal particles to be regularly-shaped, typically spherical, with an invariant morphology of shrinking reaction front inside. In this study, we employ three-dimensional (3D) numerical simulations to investigate the temporal evolution of multi-species diffusion and heat transfer within irregularly-shaped coal particles undergoing gasification in supercritical water. Compared to the conventional shrinking core model, coal particles with variable reaction front morphology exhibit a reduction in average gasification rate ranging from 21.7 % to 34.1 %. Additionally, compared to spherical particles, the gasification rate of irregularly-shaped coal particles increases by 7.1 %-68.4 %. Furthermore, the average gasification rate is found to be inversely proportional to the 1.7th power of particle sphericity and directly proportional to the 0.13th power of 3D roundness. These findings provide theoretical insights for optimizing coal particle preparation to enhance the efficiency and cleanliness of coal conversion in SCWG for hydrogen production.

关键词： Coal Supercritical water gasification Irregularly-shaped particles Reaction front

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A new control strategy of direct exergy balance for coal-fired power plants: Fundamentals and performance evaluation

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APPLIED THERMAL engineering 2025年 259卷

作者： Chen, Chen Liu, Ming Wang, Chaoyang Yan, Junjie Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

In order to facilitate the increasing penetration of grid-connected renewable power, coal-fired power plants should operate more and more flexibly. Most of the-state-of-the-art control strategies, which are mainly based on the idea of direct energy balance, cannot perform well when coal-fired power plants change load with high load cycling ramp rate. To enhance the operational flexibility of coal-fired power plants, the control idea of the direct exergy balance is proposed in this study, which directly characterizes the work capacity balance between the boiler and the steam turbine. The new control strategy of direct exergy balance emphasizes the feedback of the deviation between the turbine exergy demand signal and the boiler exergy signal. Dynamic models of a reference power plant were developed and validated, and performances of control strategies based on direct energy balance and direct exergy balance were evaluated and compared. In the 50 %-75 % load cycling process of the reference power plant, the control strategy of direct exergy balance demonstrated markedly improvements in the load cycling ramp rate (29.2 % relatively), the load cycling comprehensive index Kp (39.4 %), and reduction in the maximum deviations (28.2 %), overshoots (59.8 %), and cumulative deviations (28.7 %) of the key thermal parameters. In conclusion, the control strategy of direct exergy balance significantly strengthens the control performance during rapid load cycling processes and attains a notable enhancement in operational flexibility and a slight improvement in energy efficiency of coal-fired power plant.

关键词： Coal power Direct energy balance Direct exergy balance Operational flexibility Control strategy

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SPARDA: Sparsity-constrained dimensional analysis via convex relaxation for parameter reduction in high-dimensional engineering systems

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engineering APPLICATIONS OF ARTIFICIAL INTELLIGENCE 2025年 146卷

作者： Yang, Kuang Li, Qiang Hou, Zhenghui Liao, Haifan Yang, Chaofan Wang, Haijun Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Effective analysis of high-dimensional systems with intricate variable interactions is crucial for accurate modeling and engineering applications. Previous methods using sparsity techniques or dimensional analysis separately often face limitations when handling complex, large-scale systems. This study introduces a sparsityconstrained dimensional analysis framework that integrates the classical Buckingham Pi theorem with sparse optimization techniques, enabling precise nondimensionalization. The framework, formulated as a convex optimization problem, addresses computational challenges associated with sparsity in high-dimensional spaces. Rigorously tested across various datasets, including the Fanning friction factor for rough pipe flow, an international standards-based dataset of physical quantities and units, and experimental data from flow boiling studies, this method successfully identified critical dimensionless groups that encapsulate core system dynamics. This approach not only offers a more compact and interpretable representation than conventional methods but also retains more characteristics of function variability. It proves particularly effective in systems governed by high-dimensional interactions, demonstrating a lower failure rate and mean relative error compared to an algorithm for comparison. The methodology is applicable to the modeling and analysis of complex engineering physical systems such as nuclear power, wind tunnel design, and marine engineering, as well as in designing scaled verification experiments.

关键词： Dimensional reduction Buckingham pi theorem Active subspace Sparsity-constrained optimization Neural network

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Thermo-economic comparison of three MW-scale S-CO2 recompression Brayton cycles

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ENERGY 2025年 322卷

作者： Feng, Jiaqi Cui, Hongbo Zou, Xinsong Luo, Zhengyuan Bai, Bofeng Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

S-CO2 recompression Brayton cycle (SRBC) is considered to be one of the first choices to replace the steam Rankine cycle. Combining with nuclear or solar energy can achieve the goal of efficient, green energy conservation and emission reduction. To achieve higher efficiency and lower cost of MW-scale SRBC, this paper optimizes the cycle configuration and parameters by combining reheating, inter-cooling and pre-compression. The results show that reheating, inter-cooling and pre-compression can increase thermal efficiency by 1 %-1.65 %, 0.35 %-2.7 % and 0.16 %-0.2 %. Inter-cooling and pre-compression can increase exergy efficiency, but reheating reduces exergy efficiency. Under the condition of cycle maximum/minimum temperature of 600 degrees C/35 degrees C, the optimal value of compressor inlet and outlet pressure is 8.4 MPa and 24 MPa after consideration of system thermo-economic performance. And the expansion ratio of multi-stage turbines should be evenly distributed, the first-stage pressure ratio of multi-stage compressors should be as large as possible. SRBC can achieve optimal thermal efficiency and exergy efficiency can reach 42.62 % and 56.13 %. SRBC with staged expansion/ compression and precompression can reduce investment costs. The levelized cost of energy of SRBC and its coupled pre-compression with cycle maximum pressure of 24 MPa is 2.86 % and 10 % lower than that of the conventional S-CO2 Brayton cycle.

关键词： MW-Scale S-CO2 recompression Brayton cycle Thermo-economic analysis Configuration optimization Cycle parameter impact analysis

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Impurity-driven variations in CO2 critical flow dynamics: Modeling approaches for enhanced CCS safety

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ENERGY 2025年 323卷

作者： Liao, Haifan Wang, Xinying Yang, Kuang Hou, Zhenghui Wang, Haijun Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Carbon Capture and Storage (CCS) is a vital technology for reducing emissions, yet ensuring safe transport of CO2 and preparedness for potential leak incidents remains critical for public acceptance. Given that captured CO2 inevitably contains various impurities, it is essential to evaluate their influence on decompression behavior and critical mass flux predictions during pipeline ruptures. In this study, we investigate how different impurity compositions affect decompression dynamics and critical mass flux through classical critical flow models, in conjunction with impurity levels specified by current CCS standards. Initially, several models were evaluated for predicting the critical mass flux of pure CO2, with results indicating that the Delayed Equilibrium Model (DEM) generally outperforms others in terms of predictive accuracy. Notably, the presence of impurities elevates the pressure plateau during phase transitions, which can lead to an underestimation of critical mass flux when using standard models. Furthermore, the GERG-2008 equation of state (EOS) yields a higher pressure plateau compared to the Peng-Robinson (PR) EOS, consequently predicting a lower critical mass flux. The study also highlights differences in acoustic properties between DEM and the Homogeneous Equilibrium Model (HEM). Specifically, DEM exhibits a higher speed of sound at low void fractions, resulting in higher critical mass flux predictions under impurity-rich conditions. Recognizing the potential safety risks and economic implications of these discrepancies, we propose a new correlation that adjusts the critical mass flux of pure CO2 by incorporating thermodynamic parameters to account for impurity effects. This approach provides a practical and efficient method for improving engineering calculations and ensuring more reliable leakage response designs. Overall, our findings offer critical insights for enhancing safety management in CCS operations and support the broader integration of C

关键词： Critical flow CCS Decompression Critical mass flux prediction Impurity impact

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Prediction of adjustable steam ejectors performance through Integration of numerical simulation and theoretical model

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APPLIED THERMAL engineering 2025年 267卷

作者： Jing, Hao Yuan, Zhiwen Gao, Jianxiang Chen, Weixiong Chong, Daotong Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Adjustable steam ejector demonstrates the ability to maintain high-performance operation under frequent load fluctuations in coal-fired power plants (CFPPs), offering significant potential for practical application. To address the limitations of existing theoretical models in predicting the performance of adjustable ejectors, this study proposes a modified method that leverages numerical simulation results to drive the modification and extension of the traditional 1-D ejector theoretical model, enabling performance prediction for adjustable ejectors with known operating parameters, eliminating the need for time-consuming and costly simulations or experiments. The results indicate that the modified model significantly reduces prediction errors in subcritical mode while maintaining low errors in critical mode. Validation using simulation data from a CFPP reveals that in critical mode, the average errors for critical back pressure (CBP) and suction flow rate (ms) are within 2 % and 7 %, respectively. In subcritical mode, the average errors for CBP and ms are within 2 % and 15 %, respectively. Furthermore, the modified model demonstrates strong generalizability and practicality, accurately predicting the performance of structurally similar adjustable steam ejectors. Validation with experimental and simulation data from other studies shows average errors for CBP and ms within 2 % in critical mode and within 6 % and 12 % respectively in subcritical mode. The study confirms that the numerical simulation driven theoretical model modification approach is both effective and reliable.

关键词： Adjustable steam ejector Ejection performance prediction Numerical simulation Theoretical model modification Subcritical mode

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Co-production of hydrogen, oxygen, and electricity via an integrated solar-driven system with decoupled water electrolyzer and Na-Zn ion battery

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Journal of Energy Chemistry 2025年第1期100卷 621-627页

作者： Fei Lv Longjie Liu Jiazhe Wu Pengfei Wang Lixia Pan Dengwei Jing Yubin Chen International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi’an Jiaotong UniversityXi’an 710049ShaanxiChina

Combining water electrolysis and rechargeable battery technologies into a single system holds great promise for the co-production of hydrogen (H_(2)) and ***,the design and development of such systems is still in its ***,an integrated hydrogen-oxygen (O_(2))-electricity co-production system featuring a bipolar membrane-assisted decoupled electrolyzer and a Na-Zn ion battery was established with sodium nickelhexacyanoferrate (NaNiHCF) and Zn^(2+)/Zn as dual redox *** decoupled electrolyzer enables to produce H_(2)and O_(2)in different time and space with almost 100%Faradaic efficiency at 100 mA cm^(-2).Then,the charged NaNiHCF and Zn electrodes after the electrolysis processes formed a Na-Zn ion battery,which can generate electricity with an average cell voltage of 1.75 V at 10 m A cm^(-2).By connecting Si photovoltaics with the modular electrochemical device,a well-matched solar driven system was built to convert the intermittent solar energy into hydrogen and electric energy with a solar to hydrogen-electricity efficiency of 16.7%,demonstrating the flexible storage and conversion of renewables.

关键词： Hydrogen Electricity Decoupled water electrolyzer Na-Zn ion battery Solar energy

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