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Thermophysical property prediction of supercritical multiple mixtures fluid by molecular dynamics simulation

Journal of Molecular Liquids 2025年 432卷

作者： Tete Gui Jiasunle Li Zhiwei Ge Liejin Guo State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an 710049 China

Supercritical multiple mixtures (H 2 O/CO 2 ) fluids are produced in the poly-generation system based on supercritical water gasification (SCWG). Understanding the thermophysical property of supercritical multiple mixtures fluid is rather essential to design and industrialize the poly-generation system. At present, the selection of force field models for H 2 O/CO 2 mixtures are rather complicated, chaotic and inconsistent, the calculation of each parameter necessitates the use of one force field model. There is no universal force field model to calculate and conduct thermophysical property of H 2 O/CO 2 at one time in a wide range of temperature within SCW. In this paper, heat capacity, viscosity and thermal conductivity of multiple mixtures in supercritical and near-critical water (575 K–1075 k) are first investigated via a novel common force field model with molecular dynamics (MD) simulations. The effects of different factors including the pressure, temperature and CO 2 mass fraction on thermophysical properties of H 2 O/CO 2 at a wide range of temperature were first analyzed and conducted in detail. The calculated results indicate that the phenomenon “critical point drift” for viscosity and thermal conductivity of H 2 O/CO 2 mixtures migrating toward the low temperature region occurs. The drift values of viscosity and thermal conductivity are about 10 K and 28 K. The variation of heat capacity and viscosity of H 2 O/CO 2 mixtures increases with increasing pressures only in low temperatures region (700 K-–800 K), while the thermal conductivity always increases with increasing pressures. When the mass fractions of CO 2 increases from 20 % to 40 % and 60 %, the drift values for thermal conductivity and viscosity of H 2 O/CO 2 mixtures decreases from 628 K to 624 K and 620 K, and from 627 K to 618 K and 610 K, respectively, and the peak heat capacity decreases from 64.9 J/mol·K to 52.4 J/mol·K and 45.1 J/mol·K. The fitting polynomial to determine conductivity, visco

关键词： Molecular dynamics Supercritical multiple mixtures Supercritical water Thermophysical property

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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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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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Research on flow characteristics of dual-outlet centrifugal disk blood pumps

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Shengwu Yixue Gongchengxue Zazhi/Journal of Biomedical engineering 2025年第2期42卷 374-381页

作者： Lian, Qilong Xiao, Yuan Xiao, Yiping Cao, Zhanshuo Cui, Guomin Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China

Tesla blood pumps demonstrate a reduced propensity for hemolysis and thrombosis compared with vane blood pumps. Considering the restricted driving force within the secondary flow channel of vane blood pumps, along with the low hydraulic efficiency of conventional Tesla blood pumps and their internal flow characteristics that significantly contribute to hemolysis and thrombosis, this study introduces a set of vanes atop the rotor of the Tesla blood pump. This forms a dual-fluid domain rotor, and an axial dual-outlet volute shell structure is adopted to realize the separation of the fluid domains. Through numerical simulations of the new structure, a comparative analysis was conducted in this study on the internal flow characteristics of double-outlet and single-outlet volute shells, and symmetric and asymmetric cross-sections of the same rotor. The results indicate that the flow field distribution is more uniform under the double-outlet volute shell structure, and overall energy dissipation is decreased. After implementing the double-outlet design, in the asymmetric cross-section, compared with the symmetric cross-section, the fluid velocity gradient and turbulent kinetic energy at the tongue of the septum are reduced, and the fluid velocity gradient at the convergence of the diffuser tube outlets are also decreased. The maximum scalar stress is lower, and the decline in head and efficiency is mitigated. Moreover, compared with the single-outlet volute shell, the hemolysis index in the asymmetric cross-section is reduced. In summary, this paper proposes a novel dual-outlet centrifugal disk blood pumps, which can provide a reference for the structural design and performance optimization of magnetically levitated centrifugal blood pumps. © 2025 West China Hospital, Sichuan Institute of Biomedical engineering. All rights reserved.

关键词： Shells (structures)

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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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Modeling Study on Anisotropic Transport Properties of Pemfc Gdls Facilitated by Xct

SSRN

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SSRN 2025年

作者： Liu, Hang Li, Yang Huang, Heng Zhou, Zhifu Wu, Wei-Tao Wei, Lei Lyu, Jizu Hu, Chengzhi 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 Department of Mechanical and Energy Engineering Southern University of Science and Technology Shenzhen518055 China School of Mechanical Engineering Guangdong Ocean University Zhanjiang524088 China

The gas diffusion layer (GDL) of proton exchange membrane fuel cells (PEMFCs) is a critical component for the transport of reactants. The efficiency of reactant gas transport remains a major technical challenge in the field today. The anisotropic structure of the GDL gives rise to substantial variations of gas diffusion as well as permeability in different directions. The study employs X-CT technology to obtain the actual GDL’s geometry, aiming to investigate a spatial structure at the microscale and its gas transport characteristics. CFD method is used to simulate and study the gas diffusivity and gas permeability of GDL with four different thicknesses. The numerical simulation results show the diffusivity and permeability in the Through-plane (TP) direction are lower than those in the In-plane (IP) direction. Moreover, the effective diffusion coefficient decreases with increasing thickness, but is also dependent on the solid fibre structure of GDL. Horizontal alignment of the carbon fibers and the disc-shaped adhesive contributes to the anisotropy between the TP and IP directions, resulting in anisotropic gas transport. The purpose of the study is to supply critical references for manufacturing techniques and optimization of gas transport in GDLs. © 2025, The Authors. All rights reserved.

关键词： Gas permeability

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Corrigendum to “Experimental study on flow boiling and circumferential non-uniform heat transfer characteristics in helically-coiled tube under coupled heat transfer conditions” [Appl. Therm. Eng. 258(Part C) (2025) 124844]

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Applied Thermal engineering 2025年 261卷

作者： Hengyuan Wang Qiyu Xuan Hailin Lei Xi Li Zhibin Li Huixiong Li State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an 710049 China

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