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A comparative study on evolution characteristics of organic functional groups and gases during low-rank coal pyrolysis in N2 and H2 atmospheres

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INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 2025年 114卷 106-119页

作者： Kang, Haopeng Xu, Qiang Cao, Zeshui Lu, Xuyang Shi, Jian Chen, Bin Guo, Liejin Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn 28 West Xianning Rd Xian 710049 Peoples R China

Coal hydropyrolysis is a promising conversion pathway, but its relationship with the evolution of organic functional groups and gases remains inadequately understood. Fitting the Fourier transform infrared (FTIR) spectra of the solid products reveals that the H2 atmosphere promotes the devolatilization of phenolic hydroxyl groups, but the variation of carboxyl content is unaffected by the H2 atmosphere. Real-time analysis of the volatiles by TG-FTIR shows that the reverse water-gas shift reaction is inhibited in the H2 atmosphere, increasing the CO2 yield. Gas chromatography analysis of the gaseous products indicates that the H2 yield increases rapidly after temperature exceeding 650 degrees C, giving the volatiles significant reducing capabilities. However, the H2 yield slightly decreases in the H2 atmosphere. Using model-free kinetic methods, it is found that the H2 atmosphere reduces the activation energy, energy required, and coal reactivity during the pyrolysis process.

关键词： Hydropyrolysis Devolatilization Organic functional groups Kinetics

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Effect of the spray bar on gas-liquid two-phase flow characteristics in icing wind tunnel

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APPLIED THERMAL engineering 2025年 262卷

作者： Zhang, Haibin Guan, Bo Wei, Ren Bai, Bofeng Xi An Jiao Tong Univ Sch Chem Engn & Technol State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Accurate numerical simulation of the dispersion and heat transfer behaviors of spray droplets in cold airflows under atmospheric icing condition greatly contributes to the design of icing wind tunnels. The influence of the turbulent structure caused by the spray bar on the thermodynamics of spray droplets was generally ignored in previous studies. In this paper, the influence of the turbulent structure caused by the spray bar on the thermodynamics of spray droplets is studied through numerical simulation, and the effects of the spray bar on dispersions as well as heat and mass transfer characteristics of droplets is analyzed. Results show that pressure differences formed by the joint action of spray bar and nozzle jet act on the rib structure and result in the formation of counter-rotating vortex pair (CVP). The CVPs has a significant effect on the droplet dispersion and plays a positive role in promoting the temperature and velocity of droplets to be consistent with the mainstream. Furthermore, it is found that compared with the influence of the three-dimensional contraction effect in the contraction section of an icing wind tunnel without spray bar on the droplets, the design of spray bar has a significant effect on the temperature, velocity, and spatial distribution of droplets. This work proves that taking spray bars into account is crucial to accurately predict the gas-liquid two-phase flow field in the icing wind tunnel.

关键词： Icing wind tunnel Spray bars Water droplet Two-phase flow

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Study on coupled heat transfer characteristics and performance optimization for a helical coil heat exchanger in the lead-cooled fast reactor

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PROGRESS IN NUCLEAR ENERGY 2025年 180卷

作者： Lei, Zhenxin Li, Liangxing Zhao, Haoxiang Shi, Shang Xiang, Zutao Xu, Xiangyang Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian Ning West Rd 28 Xian 710049 Peoples R China

Helical coil heat exchangers (HCHEs) are extensively applied in thermal engineering, petrochemical engineering, nuclear reactors and refrigeration engineering etc. due to the remarkable benefits of high heat transfer efficiency with compact structures. The coupled heat transfer characteristics and performance optimization of HCHE are paramount for long-lasting operational safety of the miniaturized lead-cooled fast reactors (LFRs), especially using liquid lead and supercritical carbon dioxide (s-CO2) as the working mediums. The present work conducts a numerical study on the flow and heat transfer characteristics of lead and s-CO2 in HCHE under different mass flow and inlet temperature. Then the Non-dominated Sorting Genetic Algorithm-II (NSGA-II) is employed to carry out the geometry optimization with Performance Evaluation Criterion (PEC) and heat transfer area (HTA) as the objective functions. The results indicates that the coupled heat transfer performance is primarily affected by the mass flow of s-CO2, the mass flow of lead and the inlet temperature of lead. When the mass flow of s-CO2 increases by 52%, the overall heat transfer coefficient (HTC) of helically coiled tubes increases by 21%. To improve the comprehensive performance, three structural parameters of HCHE that should be preferred in the process of optimization design are tube-outer diameter, the number of layers and the number of tubes on the first layer.

关键词： Lead-cooled fast reactor (LFR) Supercritical carbon dioxide (s-CO 2 ) Helical coil heat exchanger (HCHE) Coupled heat transfer

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Numerical analysis on the flow and heat transfer characteristics of heat exchanger with cruciform tube

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ANNALS OF NUCLEAR ENERGY 2025年 210卷

作者： Li, Liangxing Shi, Shang Zhao, Jiayuan Lei, Zhenxin Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian ning West Rd 28 Xian 710049 Peoples R China

The heat exchanger (HE) is widely used in energy and power industries, which has a vital impact on the stability and efficient operation of relevant industrial systems. Different shaped heat exchange tubes are often designed specially to improve the thermal-hydraulic efficiency of HEs. In the study, two new geometries named the cruciform twisted tube and cruciform straight tube are introduced, and the heat & mass transfer properties of liquid lead (Pb) and supercritical carbon dioxide (s-CO2) in the HEs are numerically studied to assess the thermal-hydraulic efficiency and application prospect of two kinds of cruciform tube HEs. The results demonstrate that the unique cross-section geometry of the cruciform tube improves the uniformity of the flow field, and the spiral structure of the cruciform twisted tube effectively improves the blending and turbulence of working fluid. The cruciform tube can improve the comprehensive performance of the HE by more than 12%.

关键词： Cruciform tube Numerical analysis flow and heat transfer Heat exchanger

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Performance analysis of a novel unassisted photoelectrochemical water splitting hybrid system based on spectral beam splitting

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FRONTIERS IN ENERGY 2025年 1-14页

作者： Wang, Baoyuan Yang, Suyi Zhang, Tuo Liu, Yukai Yang, Sheng Li, Luning Wang, Weiding Su, Jinzhan Xi An Jiao Tong Univ Int Res Ctr Renewable Energy State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Photoelectrochemical (PEC) water splitting, particularly self-biased PEC systems, holds great promise for solar energy utilization. However, the limited transparency of most photoelectrodes presents challenges in fabricating tandem photoelectrodes with photovoltaic (PV) cells for self-biased water splitting. Herein, a novel self-biased hybrid system integrating photoelectrodes (TiO2, BiVO4), beam splitters (BSs), and PV cell was proposed to enhance solar energy utilization and PEC water splitting performance. The results indicate that the integration of BSs significantly improves the current densities of both self-biased PV-PEC systems and single PEC systems. The current density of self-biased water splitting system with BSs exceeds that of the conventional TiO2 + BVO-PV system, and the intersection point of the I-V curves for the photoanodes and solar cell is closer to the maximum power output of the solar cell. The effective utilization of the solar spectrum by both the photoelectrode and the PV cell in the hybrid system with BSs significantly increases the power output by a factor of 18.8 compared to the conventional tandem self-biased system. The predicted results indicate that the hydrogen production rate of the system with BSs is 12.1 mu mol/(hcm2), while the STH efficiency is enhanced by a factor of 12.38 and 19.87 compared to conventional TiO2 + BVO-PV and TiO2/BVO-PV tandem PV-PEC systems, respectively, demonstrating the advantage of the water splitting system with spectral BSs. In conclusion, this work provides an innovative approach of achieving self-biased water splitting by coupling spectral BSs with a PV-PEC system, resulting in improved solar energy harvesting efficiency.

关键词： spectral beam splitter photovoltaic-photoelectrochemical (PV-PEC) water splitting spectrum energy flow

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Tailoring a local acidic microenvironment on amorphous NiMoB catalyst to boost alkaline and neutral hydrogen evolution reactions

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APPLIED CATALYSIS B-ENVIRONMENT AND ENERGY 2025年 365卷

作者： Zhao, Rui Zhang, Chunyang Wei, Liting Wei, Daixing Su, Jinzhan Guo, Liejin Xi An Jiao Tong Univ Int Res Ctr Renewable Energy State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Improving hydrogen evolution reaction (HER) kinetics in alkaline and neutral environments is crucial for reducing energy consumption in industrial electrolyzers. Here, we propose a strategy to tailor the chemical reaction microenvironment through crystal phase engineering and electronic structure modulation. Taking amorphous Am-NiMoB as a case study, we successfully created a local acid-like microenvironment in both alkaline and neutral media, enabling superior HER performance. Operando Raman spectroscopy confirmed the in-situ generation of abundant hydronium ions (H3O+) intermediates on the Am-NiMoB surface during HER. Electrochemical analysis and theoretical calculations reveal that the enriched oxygen vacancies in Am-NiMoB facilitate H2O dissociation, while Mo doping reduces the binding strength of H* intermediates. These factors are key contributors to the formation of this unique acidic surface. Am-NiMoB exhibits high performance typically associated with acidic environments, with overpotentials of 38 and 48 mV to achieve a current density of 10 mA cm-2 and Tafel slopes of 34.4 and 39.4 mV dec- 1 in alkaline and neutral electrolytes, respectively. Notably, Am-NiMoB demonstrates robust durability for over 350 h during seawater electrolysis at 500 and 1000 mA cm- 2. This work exemplifies the potential of enhancing catalytic activity through interfacial microenvironment modulation.

关键词： Amorphous Mo-doped nickel borate Water electrolysis Hydrogen evolution reaction Local acid-like microenvironment Industrial-grade current density

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Reduced Graphene Oxide Regulates Indium Oxide In-Situ Reconstruction for Enhanced CO2 Electroreduction

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ACS MATERIALS LETTERS 2025年第3期7卷 796-803页

作者： Ding, Xue Zeng, Lingchun Qiu, Haoran Jing, Wenhao Wang, Feng Liu, Ya Guo, Liejin Xi'an Jiaotong Univ Int Res Ctr Renewable Energy State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

The practical application of electrocatalytic CO2 reduction requires adaptation to the fluctuating voltage output of photovoltaic systems. However, potential-induced in-situ reconstruction of the catalyst complicates control and leads to Faradaic efficiency (FE) instability across the potential window. Here, we present a redox graphene-supported indium oxide catalyst (G-InO x ), where rGO effectively regulates the surface evolution of InO x from In3+ to In0 during electrocatalytic reactions. The multivalent In generated via electrocatalytic in-situ reconstruction lowers the energy barriers for *OCHO formation and dissociation, enhancing formate production. rGO also regulates the surface environment, optimizing CO2 and proton delivery to the active sites. Over a wide potential range (-0.86 to -1.37 V vs RHE), G-InO x achieves FEformate nearly 100%. This work offers a straightforward and efficient strategy for scalable, high-performance CO2 electroreduction.

关键词： Indium compounds

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Multi-scale simulation of displacement damage of spatially-correlated recoiled atoms in silicon

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RADIATION EFFECTS AND DEFECTS IN SOLIDS 2025年

作者： Liu, Fang Wang, Tao He, Huan Bai, Yurong Shi, Tan Zhou, Pingan Chen, Chuanhao He, Chaohui Zang, Hang Xi An Jiao Tong Univ Sch Nucl Sci & Technol Shaanxi Key Lab Adv Nucl Energy & Technol State Key Lab Multiphase Flow Power Engn Xian Peoples R China

Multi-scale simulations have emerged as a promising tool for modelling displacement damage in silicon in recent years. In the current work, binary collision approximation (BCA), molecular dynamics (MD) and kinetic Monte Carlo (KMC) simulations are employed to systematically investigate the effects of different recoiled atoms on the damage produced by one proton in silicon. The results indicate that approximately 40% of protons reacted in silicon produced two or more recoiled atoms. Furthermore, the number of Frenkel pairs generated by two nearby recoiled atoms is correlated with their energy, relative distance and relative angle. Compared with iron or tungsten, the simultaneous incidence of adjacent atoms in silicon has a smaller impact on the number of Frenkel pairs. The large defect clusters produced during the heat spike hinder the recombination between point defects, resulting in a decrease in the defect recombination rate. Additionally, the types and numbers of defects in the subsequently long-term evolution were discussed. The varieties and numbers of defect cluster might depend on the initial distance between recoiled atoms. These results provide fundamental support to understand radiation damage in silicon.

关键词： Multi-scale modeling, displacement cascade, defect annealing, defect cluster, cascade interaction

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The condensation process of supercritical water gasification products in a bicubic supersonic nozzle

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PHYSICS OF FLUIDS 2025年第2期37卷

作者： Wu, Hongtu Wang, Weizuo Jin, Hui Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn SKLMF 28 Xianning West Rd Xian 710049 Shaanxi Peoples R China

The development of energy-efficient and clean supercritical water gasification product (SCWGP) separation technology has become one of the bottlenecks in advancing supercritical water gasification technology. This study suggests utilizing a supersonic nozzle to condense and separate H-2 and CO2 from SCWGP. The flow and condensation model are established for a bicubic parametric supersonic nozzle, and the effects of various operating conditions on the condensation separation of SCWGP are analyzed. The liquid phase mass fraction at the nozzle outlet is significantly influenced by the inlet pressure and temperature. The approximate relationship between inlet pressure variations and liquid phase mass fraction is 0.065 per MPa, while the relationship between inlet temperature variations and liquid phase mass fraction is approximately -0.013 per K. The latent heat released during the condensation process has a significant impact on the temperature distribution within the nozzle. Inlet parameters have a notable effect on the peak values and positions of nucleation and droplet growth rates. The condensed liquid CO2 is primarily concentrated near the center of the nozzle outlet. The efficiency of the condensation separation is strongly influenced by the molar fraction of CO2 in the gas mixture, while the small amount of N-2 mixed in has little effect on the condensation separation performance.

关键词： Gas mixtures

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Experimental investigation of the photovoltaic thermal integrated with ground heat exchanger using volcanic tuff stones

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APPLIED THERMAL engineering 2025年 263卷

作者： Alqatamin, Ahmad Su, Jinzhan Xi An Jiao Tong Univ Int Res Ctr Renewable Energy Sch Energy & Power Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

This study evaluates the performance of a photovoltaic thermal (PVT) system integrated with a ground heat exchanger (GHE) utilizing volcanic tuff stones as a heat storage material. In contrast to conventional PVT systems, this innovative approach leverages the thermal conductivity and porosity of volcanic tuff stones to enhance heat storage capacity and cooling efficiency. While previous research has focused on standalone PVT systems or GHE applications, limited attention has been given to their integration using natural materials. This study addresses this gap by experimentally investigating the combined system's thermal and electrical performance under real outdoor conditions in Tafila, Jordan. The experimental setup included a polycrystalline solar module coupled with a GHE designed to enhance electrical, thermal efficiencies and thermal storage. The results show that integrating the GHE reduced the Solar cell's temperature by up to 23 %, improving electrical efficiency by 4 % and increasing electrical power output by 6.56 % compared to a standalone PVT system. Thermal efficiency also improved significantly, reaching 70.60 % compared to 58.66 % thermal efficiency in the PVT system. The GHE raised outlet air temperatures by an average of 10 degrees C above ambient, demonstrating effective heat recovery. Furthermore, when coupled with a fan coil unit, the system reduced energy consumption by 14.81 % during the heating season. These findings highlight the novelty of integrating volcanic tuff stones into PVT-GHE systems, offering a sustainable solution for improving energy efficiency and thermal performance in renewable energy applications.

关键词： Photovoltaic thermal Volcanic tuff stones Ground heat exchanger Efficiency Fan coil unit

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