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General analytical equation of state for nanoconfined gases derived from statistical physics

Physical Review E 2025年第2期111卷 025413-025413页

作者： Chengzhen Sun Haoxuan Li Zhixiang Zhao Mehdi Neek-Amal Bofeng Bai State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 China School of Urban Planning and Municipal Engineering Xi'an Polytechnic University Xi'an Shaanxi 710048 China Department of Physics Faculty of Sciences Shahid Rajaee Teacher Training University 16875-163 Lavizan Tehran Islamic Republic of Iran Department of Physics University of Antwerp Groenenborgerlaan 171 2020 Antwerp Belgium

The pressure prediction of nanoconfined gases is crucial for various industrial applications, yet existing equations of state (EOS) often compromise between accuracy and usability. This study derives a theoretical EOS in analytical form, combining precision and practicality through statistical physics. It begins by examining the pressure drop mechanism due to adsorbed molecules and refines molecular pairing and potential energy interactions. The resulting EOS accurately predicts the pressure of gases in nanoconfined spaces, especially with an average prediction error of about 5% for strongly adsorbing gases like nitrogen, oxygen, and argon. Additionally, it aligns with the Van der Waals EOS under macroscopic conditions, offering a unified framework across scales. This model enhances both engineering applications and the understanding of nanoconfined EOS.

关键词： Van der Waals forces

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Occurrence and flow Characteristics of Methane in High-Temperature and High-Pressure Nanopores of Deep Shale

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2025年第4期46卷 1200-1204页

作者： Wang, Rui Sun, Chengzhen Yang, Xu State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Petroleum Engineering School Southwest Petroleum University Chengdu610500 China

The understanding of gas transport in deep shale nanopores is still not clear. In this study, molecular simulations of methane occurrence and flow in illite slits of deep shales under the condition of high-temperature and high-pressure was carried out. The occurrence, diffusion and flow characteristics of methane molecules were analyzed. The effects of temperature and pressure on methane occurrence and flow were elucidated. The results show that the distribution of methane density in illite slits is nonuniform, and there are density peaks near the wall. Compared with Middle and Shallow shales, more methane molecules can exist in the pores of deep shale, and the diffusion ability is limited. The methane flow flux decreases with the decrease of pressure (5∼80 MPa) and increases with the decrease of temperature (60∼120◦C). Pressure is the main dominating factor of flow flux, and the flow flux decreases gradually during depressurization. © 2025 Science Press. All rights reserved.

关键词： Nanopores

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Laser-based speciation of acetone oxidation behind reflected shock waves and chemical kinetic modeling

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International Journal of Hydrogen Energy 2025年 141卷 46-58页

作者： Congjie Hong Xin Zhang Jiabiao Zou Zuohua Huang Yingjia Zhang Aamir Farooq State Key Laboratory of Multiphase Flows in Power Engineering Xi'an Jiaotong University Xi'an 710049 People's Republic of China Clean Energy Research Platform Physical Sciences and Engineering (PSE) Division King Abdullah University of Science and Technology (KAUST) Thuwal 23955-6900 Saudi Arabia

With the growing global focus on renewable and oxygenated fuels, acetone has attracted significant attention due to its role as a key intermediate in the oxidation of alcohol-based fuels, an efficient hydrogen carrier, and a vital component in hydrogen production via catalytic reforming and biofuel synthesis. A comprehensive understanding of its pyrolysis and oxidation mechanisms is crucial for advancing clean energy technologies and optimizing its utilization in sustainable fuel applications. However, discrepancies persist in existing models regarding the time histories of key species during acetone pyrolysis. In this study, advanced laser diagnostic techniques were employed to measure the time-resolved concentration profiles of various species during acetone oxidation behind reflected shock waves, capturing the dynamic evolution of key intermediates and products such as CO, OH, and H 2 O. By integrating the latest experimental and theoretical studies, including the concentration profiles of key intermediates during pyrolysis, rate coefficient measurements, and ignition delay times, the critical reaction pathways and rate coefficients of acetone were systematically refined. Additionally, previously missing reaction pathways (i.e., CH 2 CO + CH 3 =HCCO + CH 4 ) were incorporated, leading to an improved acetone kinetic model that underwent comprehensive validation against various experimental datasets. The results indicate that the updated model accurately predicts the time-resolved concentration profiles of key species during acetone oxidation and pyrolysis over a wide temperature range, with significant improvements in predicting ignition delay times and laminar flame speeds. This study offers valuable insights for refining acetone kinetic models and establishes a research framework for investigating the complex chemical behavior of ketones and other oxygenated fuels in combustion.

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Recent advances in nanoporous graphene membrane for gas separation and water purification

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Science Bulletin 2015年第21期60卷 1807-1823页

作者： Chengzhen Sun Boyao Wen Bofeng Bai State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University

Graphene is a one-atom-thick sheet of graphite comprising sp2-hybridized carbon atoms arranged in the hexagonal honeycomb lattices. By removing the honeycomb lattices and forming nanopores with specific geometry and size, nanoporous graphene has been demonstrated as a very high-efficiency separation membrane, due to the ultrafast molecular permeation rate for its one-atom thickness. This review focuses on the recent advances in nanoporous graphene membrane for the applications of gas separation and water purification, with a major emphasis on the molecular permeation mechanisms and the advanced fabrication methods of this state-of-the-art membrane. We highlight the advanced theoretical and experimental works and discuss the gas/water molecular transport mechanisms through the graphene nanopores accompanied with theoretical models. In addition, we summarize some representative membrane fabrication methods, covering the graphene transfer to porous substrates and the pore generation. We anticipate that this review can provide a platform for understanding the current challenges to make the conceptual membrane a reality and attracting more and more attentions from scientists and engineers.

关键词： Nanoporous graphene Gas separationWater purification Molecular permeationmechanism Membrane fabrication

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A wall-temperature-independent heat transfer model and dominant dimensionless numbers for supercritical CO 2 in vertical upward flow

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The Journal of Supercritical Fluids 2025年 224卷

作者： Zhenghui Hou Haifan Liao Kuang Yang Shaozhe Bai Xinjiang Fan Chaofan Yang Haijun Wang State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an 710049 China

The heat transfer coefficient is a critical parameter for the design and optimization of supercritical carbon dioxide (sCO₂) heat exchange systems. Based on 20723 data points collected from 22 published studies, existing heat transfer correlations are evaluated, and a new model with improved stability and predictive accuracy is developed. Current correlations for upward vertical sCO₂ flow typically include wall-temperature-dependent parameters, which often lead to issues such as non-uniqueness or the absence of solutions during wall temperature prediction, along with limited accuracy. To address these issues, this study integrates the Buckingham Pi theorem and constructs a wall-temperature-independent heat transfer model using a dimensionless neural network. This approach avoids the problems of multiple or no solutions and achieves high predictive performance, with mean absolute relative errors of 2.83 % for wall temperature and 5.81 % for Nusselt number predictions. Furthermore, the active subspace method is employed to identify four dominant dimensionless groups governing the heat transfer process. These groups can be decomposed into products of commonly known dimensionless numbers. During this process, a new dimensionless number—the buoyancy generation ( BG ) number—is proposed and defined. This study leverages data-driven dimensional analysis to explore key influencing parameters and dominant dimensionless numbers for supercritical heat transfer, offering new insights into the underlying physical mechanisms.

关键词： Electric heating

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Teardrop-like micro pin fin coated nanotube arrays chip for enhancement of flow boiling electronics cooling

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International Journal of Thermal Sciences 2025年 214卷

作者： Chen, Hongqiang Gao, Quan Ma, Xiang Li, Kai Du, Wangfang Li, Caifeng Zhang, Yonghai Wei, Jinjia School of Chemical Engineering and Technology Xi'an Jiaotong University 28 Xianning West Road Shaanxi Xi'an710049 China Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China National Microgravity Laboratory Institute of Mechanics Chinese Academy of Sciences Beijing100190 China School of Engineering Science University of Chinese Academy of Sciences Beijing100149 China Xi'an Shaangu Power Co. Ltd. Xi'an710075 China

Phase change flow boiling heat transfer in microchannel is a very efficient thermal management mode for high-power electronics/devices cooling. However, achieving comprehensive enhancement of flow boiling heat transfer performance at low power consumption is still challenging. Herein, we devised and manufactured a teardrop-like micro-pin-fin coated stable copper hydroxide nanotubes array chip surfaces (S-Nanotube), demonstrating their exceptional enhancement in flow boiling heat transfer efficiency. A series of experiments were conducted using HFE-7100 as a working fluid within a semi-open microchannel. Compared to the smooth surface, the critical heat flux (CHF) and the maximum boiling heat transfer coefficient (HTC) of the S-Nanotube is increased by 82.1 % (from 45.1 to 72.9 and then to 82.1 W/cm2) and 140.5 % (from 5955 to 11,325 and then to 14,316 W/m2·K) at extremely low-pressure drop (≤4 kPa), showing a high coefficient of performance (COP). The temperature of the onset of nucleate boiling on the S-Nanotube surface is reduced by 26.4 %, and the heat flux is greatly increased in a small wall temperature variations (ΔT ≤ 10 °C). In situ observation and analysis of the surface properties and the bubble dynamics, the S-Nanotube chip promotes the phase change heat transfer process by providing massive nucleation sites, reducing bubbles size and residence time, and enhancing the wicking wetting capacity. These findings provide guidance for the rational design of boiling heat transfer-enhanced surfaces and heat sinks and point the way to achieving efficient thermal management of power devices. © 2025 Elsevier Masson SAS

关键词： Electronic cooling

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Thermal and hydraulic performance of molten salt steam generation system under varying operating conditions in concentrating solar power plants

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Case Studies in Thermal engineering 2025年 72卷

作者： Jiaming Tian Bo Ren Yiran Duan Biao Li Yueshe Wang State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an 710049 China

To conduct the thermal transport characteristics and operational stability of the steam generation system (SGS) under partial load conditions in concentrating solar power (CSP), a real-scale shell-and-tube steam generator hydrodynamics predictive model is developed. This model integrates lumped parameter methods with the finite volume method to account for heat transfer and phase change. Additionally, in accordance with the prevailing water circulation mode in the CSP plant, a typical model of the natural circulation system is established, while optimal stable operating points of the maximum circulation mass flow rate under varying operating conditions are determined. The results indicate that the inherent stability of the generator strongly lies in the dynamic compromise between its thermodynamic and hydrodynamic characteristics. Under high load conditions, the natural circulation mode demonstrates excellent flow stability. Operating at lower operating pressures results in greater circulation flow and a heightened sensitivity to phase changes. Under system pressures of 13.76, 11.08, 8.39, and 6.71 MPa, the recommended circulation ratios are determined to be 5.38, 7.86, 11.95, and 16.07, respectively. Furthermore, the stability of the circulation curve is optimized by adjusting the structural dimensions of the steam generator. The sensitivity to evaporation capacity and heat exchanger effectiveness is assessed.

关键词： Molten salt storage Steam generator Natural circulation mode Concentrating solar power

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A review of engine application and fundamental study on turbulent premixed combustion of hydrogen enriched natural gas

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Science China(Technological Sciences) 2014年第3期57卷 445-451页

作者： WANG JinHua WEI ZhiLong ZHANG Meng HUANG ZuoHua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

The application and fundamental study on turbulent premixed combustion of hydrogen enriched natural gas is reviewed in this *** include the combustion characteristics of direct injection engine fueled with hydrogen enriched natural gas,visualization study of direct injection combustion of hydrogen enriched natural gas using a constant volume vessel,and the fundamental study of turbulent premixed combustion of hydrogen enriched natural *** effect of additional hydrogen on the combustion process of natural gas engine is investigated from the fundamental view of the interaction between combustion reaction and turbulent flow.

关键词： natural gas hydrogen direct injection combustion turbulent premixed combustion OH-PLIF engine

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Low-energy and accelerated hydrogen release from MgH2–5 wt% NaTiOxH catalyzed hydrogen storage reactor by graphite responsive microwave

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Journal of Magnesium and Alloys 2025年

作者： Wang, Bofei Wu, Zhen Liu, Honghao Yang, Fusheng Zhang, Zaoxiao Yao, Jing Li, Qian Cao, Hujun Li, Bo State Key Laboratory of Fluorine & Nitrogen Chemicals School of Chemical Engineering and Technology Xi'an Jiaotong University Xi'an710049 China State Key Laboratory of Multiphase Flow for Power Engineering Xi'an Jiaotong University Xi'an710049 China National Engineering Research Center for Magnesium Alloys Chongqing University Chongqing400044 China Dalian National Laboratory for Clean Energy Dalian Institute of Chemical Physics Chinese Academy of Sciences Dalian116023 China Faculty of Engineering Electrical Energy Management Group University of Bristol BristolBS8 1QU United Kingdom

Owing to high thermal stability and large reaction enthalpy, MgH2 has high reaction temperatures and sluggish reaction kinetics in the dehydrogenation process, which consumes lots of energy. To achieve hydrogen release with low energy consumption, accelerated reaction rate, and high heating uniformity, this paper proposes a novel method of graphite responsive microwave-assisted thermal management with NaTiOxH catalyst. A multi-physics model of the 5 wt% NaTiOxH catalyzed MgH2 reactor integrated with a microwave generator is developed to investigate the reaction, heat and mass transfer process of hydrogen release. It is found that the graphite responsive microwave heating method could improve the temperature uniformity of reaction bed, reduce the energy consumption by at least 10.71% and save the hydrogen release time by 53.49% compared with the traditional electric heating method. Moreover, the hydrogen desorption thermodynamics could be improved with the increase of microwave power. The hydrogen release time is shortened by 19.55% with the increase of 20 W microwave power. Meanwhile, it is also concluded that the microwave excitation frequency of 2.1 GHz and the graphite content of 2 wt% have better heating performance. Therefore, it can be verified that the graphite responsive microwave heating helps to low-energy and accelerated hydrogen release from MgH2 hydrogen storage reactor. © 2025

关键词： Reaction rates

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Efficient One-Step Electrochemical Synthesis of Ammonia-Hydrogen Fuel for Clean Energy Applications

SSRN

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SSRN 2025年

作者： Yang, Zhongmei Wang, Xiaoyang Mu, Xiaojiang Hong, Congjie Miao, Lei Novel Battery Materials Research Center of Engineering Technology State Key Laboratory of Featured Metal Materials and Life-cycle Safety for Composite Structures School of Physical Science and Technology Guangxi University Nanning530004 China State Key Laboratory of Multiphase Flows in Power Engineering Xi’an Jiaotong University Xi’an710049 China

Ammonia-hydrogen fuel, recognized as a quintessential zero-carbon green energy source, presents significant challenges in storage and transportation due to the inherent safety risks associated with hydrogen fuel handling. Leveraging ammonia's potential as an efficient hydrogen storage medium, we focus on developing a novel technology for on-site ammonia decomposition to produce hydrogen under ambient conditions. Here, we employ a straightforward electrochemical process to catalytically decompose ammonia into hydrogen and nitrogen at standard temperature and pressure, with ammonia in its gaseous form directly volatilized from an aqueous ammonia solution. A CeO2@NiCu₃/NF electrocatalyst capable of efficient ammonia decomposition at an impressively low potential (1.27 V vs. RHE) was synthesized. This catalyst demonstrated a Tafel slope of 41.5 mV dec-1, significantly improving electrolysis efficiency. It also exhibited excellent stability during 21 hours of continuous operation. Density Functional Theory (DFT) analysis revealed that the unique composite structure of CeO2 and NiCu3 features a d-band position similar to platinum, optimizing the adsorption-desorption balance of ammonia. Furthermore, the impact of ammonia on the combustion characteristics of hydrogen under different cracking ratios was investigated from an application perspective. Combustion kinetics simulations were performed to evaluate the effects of ammonia on the ignition delay time (IDT) and laminar flame speed (LFS) of hydrogen. The results indicate that the presence of small amounts of NH3 has a negligible effect on the ignition delay time of hydrogen but significantly reduces its laminar flame *** study provides a valuable experimental foundation for advancing the practical utilization of hydrogen as a sustainable fuel while addressing the challenges associated with ammonia-hydrogen energy systems. © 2025, The Authors. All rights reserved.

关键词： Ammonia

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