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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： Gui, Tete Li, Jiasunle Ge, Zhiwei Guo, Liejin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

Supercritical multiple mixtures (H2O/CO2) 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 H2O/CO2 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 H2O/CO2 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 CO2 mass fraction on thermophysical properties of H2O/CO2 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 H2O/CO2 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 H2O/CO2 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 CO2 increases from 20 % to 40 % and 60 %, the drift values for thermal conductivity and viscosity of H2O/CO2 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, viscosity and heat capacity H

关键词： Temperature distribution

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Homojunction photocatalysts for water splitting

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Nano Research 2022年第12期15卷 10171-10184页

作者： Xiangjiu Guan Shichao Zong Shaohua Shen International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi’an Jiaotong UniversityXi’an710049China Suzhou Academy of Xi’an Jiaotong University Suzhou215123China Key Laboratory of Subsurface Hydrology and Ecological Effects in Arid Region Ministry of EducationSchool of Water and EnvironmentChang’an UniversityXi’an710064China

Charge-carrier separation is regarded as one of the critical issues of photocatalytic water splitting and could be accelerated by constructing microscopic junctions in *** photocatalysts consisting of different forms of semiconductor with identical compositions could inherit the advantages of heterojunction-based photocatalysts in charge separation due to the built-in electric field,while omitting the potential drawbacks of interfacial lattice distortion by providing continuous band ***,homojunction-based photocatalysts have recently drawn growing attention in water *** this review,the synthetic approaches to preparing photocatalysts with various homojunction structures including p-n junction,phase junction,and facet junction were introduced,together with a comprehensive analysis and discussion on the latest progress in the application of photocatalytic water *** review work is expected to inspire more related work with promoted research on designing efficient homojunction-based photocatalytic systems for water splitting.

关键词： photocatalytic water splitting homojunction charge separation

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Simulation Study on Heat Exchangers Characteristics of Solar Thermal Steam System Based on Aspen Plus 2

Simulation Study on Heat Exchangers Characteristics of Solar...

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2nd International Conference on Algorithms, High Performance Computing and Artificial Intelligence, AHPCAI 2022

作者： Chen, Pengfei Chen, Kang Peng, Huaiwu Zhang, Yanlong Bawaa, Baercheng Zhao, Qiuyang Institute of Solar Engineering Technology Northwest Engineering Corporation Limited Power China Xi'an710065 China Xi'An Jiaotong University State Key Laboratory of Multiphase Flow in Power Engineering Xi'an China

ISBN: (纸本)9798350334784

In the thermal recovery project of thick oil, there are high standards for steam temperature and flow rate. The solar thermal steam supply system can convert unstable solar energy into stable and efficient carrier heat, which can be used to transfer heat to low-temperature water to produce high-temperature steam and achieve a clean and low-carbon steam supply. The rated pressure of steam and the split ratio of molten salt in the heating system have a great influence on the demand area and heat load of solar panels. In this paper, a simulation is made on the solar thermal steam supply system based on Aspen Plus. The simulation result shows that the increase in pressure will cause a growth in the area of the photothermal concentrator field but will reduce the area used for photovoltaic panels. At the same time, it reduces the heat load of the evaporator and extends its service life. The split ratio affects the molten salt temperature at the outlet of the superheater and the reheater. When the split ratio increases, the heat transfer temperature difference between the two ends of the superheater heat flow decreases, and the heat transfer temperature difference of the reheater grows bigger. Therefore, the molten salt temperature flowing out of the reheater rises. © 2022 IEEE.

关键词： Heat exchangers

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Regulation on polymerization degree and surface feature in graphitic carbon nitride towards efficient photocatalytic H2 evolution under visible-light irradiation

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Journal of Materials Science & Technology 2022年第3期98卷 160-168页

作者： Cheng Cheng Chung-Li Dong Jinwen Shi Liuhao Mao Yu-Cheng Huang Xing Kang Shichao Zong Shaohua Shen International Research Center for Renewable Energy(IRCRE) State Key Laboratory of Multiphase Flow in Power Engineering(MFPE)Xi'an Jiaotong University(XJTU)28 West Xianning RoadXi’an 710049China Department of Physics Tamkang University151 Yingzhuan RoadTamsui 25137TaiwanChina

A kind of graphitic carbon nitride(TSC-550) with high polymerization degree and improved surface property was prepared by a new precursor of thiosemicarbazide. The sulfur motif and high nitrogen content in thiosemicarbazide promoted the polymerization of thiosemicarbazide to form graphitic carbon nitride framework with high degree of polymerization, which significantly influenced the electronic structure and surface chemical properties. TSC-550 possessed a narrow bandgap of 2.19 eV that facilitated the utilization of visible light, and possessed a less positive charge, acidic surface that resulted in enhanced hydrogen adsorption ability in water solution, which promoted the H;evolution kinetics. In addition, the extended π-conjugated electronic system promoted the separation and migration of photogenerated charge carries in plane of TSC-550 framework, as well as the increasing interlayer C–N interactions in TSC-550 created conductive paths across the layers to tunnel interlayers for rapid electron transportation. As a result, TSC-550 nanosheets showed excellent photocatalytic H;production activity,the AQY achieved 36.4% at 425 nm.

关键词： Degree of polymerization Graphitic carbon nitride Photocatalysis Solar energy Hydrogen

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Numerical Study on Influence of Platen Super-Heaters on Heat Deviation in a 600 MW Tangentially Fired Pulverized-Coal Boiler 9th

Numerical Study on Influence of Platen Super-Heaters on Heat...

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9th International Symposium on Coal Combustion, ISCC 2019

作者： Chen, Kai Zhang, Yan Deng, Lei Che, Defu School of Mechanic Engineering Xijing University Xi’an710123 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

ISBN: (纸本)9789811616563

In order to investigate effects of platen super-heaters on the heat deviation in the cross-over pass, numerical simulation of a 600 MW tangentially fired pulverized-coal boiler has been studied. Two cases, building super-heaters or not, were established by FLUENT software in this study. Numerical results agree well with measured data of the utility boiler. Results show platen super-heaters break symmetry of velocity distribution at the furnace outlet. The position where peak temperature occurs is affected by platen super-heaters, while the position where peak velocity occurs is not. Platen super-heaters slightly reduce the temperature deviation at the furnace outlet, and enhances the velocity deviation at the furnace outlet. For this boiler, the velocity deviation is the main reason for the heat deviation in the cross-over pass. The simulation results in this study can provide reference for optimization of temperature deviation and velocity deviation in tangentially fired pulverized-coal boiler. © 2022, Tsinghua University Press.

关键词： Furnaces

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A n-Si/CoOx/Ni:CoOOH photoanode producing 600 mV photovoltage for efficient photoelectrochemical water splitting

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Science China Materials 2022年第12期65卷 3442-3451页

作者： Zhuocheng Yin Yuchuan Shi Shaohua Shen International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi’an Jiaotong UniversityXi’an 710049China

n-Si,believed as a promising photoanode candidate,has suffered from sluggish oxygen evolution reaction(OER)kinetics and poor chemical stability when exposed to aqueous ***,CoO_(x)/Ni:CoOOH bilayers were successfully deposited on n-Si substrate by atomic layer-deposition(ALD)and photoassisted electrochemical deposition(PED)for stabilizing and catalyzing photoelectrochemical(PEC)water *** comparison to the n-Si/CoO_(x)photoanode as reference,the prepared n-Si/CoO_(x)/Ni:CoOOH photoanode upon the optimized PED process presents a much improved PEC performance for water splitting,with the onset potential cathodically shifted to~1.03 V *** hydrogen electrode(RHE)and the photocurrent density much increased to 20 mA cm^(−2)at 1.23 V *** is revealed that the introduction of Ni dopants increases the work functions of the deposited Ni:CoOOH overlayers,which gives rise to the upward band bending weakened at the n-Si/CoO_(x)/Ni:CoOOH cascading interface while strengthened at the Ni:CoOOH/electrolyte interface(with the band bending shifted from downward to upward),contributing to the decreased and the increased driving forces for charge transfer at the interfaces,***,the balanced driving forces at the interfaces would endow the n-Si/CoO_(x)/Ni:CoOOH photoanode with the best PEC ***,PED has been evidenced superior to ED to dope Ni into CoOOH with the formed overlayer effectively catalyzing and stabilizing PEC water splitting.

关键词： n-Si photoanode work function photoelectrochemical water splitting

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Exergy Analysis of a Novel Chemical Looping Hydrogen Generation System Integrated with SOFC

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Journal of Thermal Science 2021年第1期30卷 313-323页

作者： ZHANG Xiaosong CHEN Zhewen CHEN Zhenbin LI Jinsong Mechanical and Electrical Engineering College Hainan UniversityHaikou 570228China Beijing Key Laboratory of Multiphase Flow and Heat Transfer North China Electric Power UniversityBeijing 102206China

In this paper,a novel system integrating chemical-looping hydrogen generation(CLH)system and solid oxide fuel cell(SOFC)has been *** new methane-fuelled energy system was investigated with energy balance and exergy *** produces the hydrogen as the fuel of the SOFC,and the Fe O and Fe3O4 are selected as the looping *** heat from the SOFC is absorbed by the CLH and converted to chemical energy through the reduction reaction of *** to the cascade utilization of the fuel between the CLH and SOFC,the net efficiency of this novel system can achieve 62.8%considering CO_(2)separation,more than 10 percentage points higher than a methane reforming fuelled SOFC ***,by using the CLH to produce the hydrogen,the CO_(2)can be recovered without an energy *** the analysis of the graphical exergy,the cascade utilization of waste heat and the high-efficiency hydrogen production is the main reason of high *** novel system also has the advantage of CO_(2)capture without energy penalty,so this combined system is an advantaged method to accomplish the efficient utilization of methane.

关键词： chemical looping fuel cell exergy analysis

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ReaxFF-MD simulation investigation of the degradation pathway of phenol for hydrogen production by supercritical water gasification

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Energy Storage and Saving 2023年第4期2卷 578-585页

作者： Deming Zhang Shaoqi Wang Yu Feng Zixuan Wang Hui Jin School of Mechanical Engineering and Automation Harbin Institute of TechnologyShenzhenGuangdong518055China Institute of Intelligent Ocean Engineering Harbin Institute of TechnologyShenzhenGuangdong518055China State Key Laboratory of Multiphase Flow in Power Engineering(SKLMF) Xi’an Jiaotong UniversityXi’an710049China

Wastewater from the thermochemical conversion of coal and biomass contains a significant amount of phenolic structures *** degradation of these phenolic compounds to hydrogen-rich gasses can prevent envi-ronmental pollution and save *** water(SCW)gasification of phenol is experimentally studied and a reactive force field molecular dynamics(ReaxFF-MD)simulation is conducted to investigate the catalytic mechanism of Ni/Al2 O3 in the phenol *** experimental results indicate that Ni/Al2 O3 facilitates the conversion of phenol to 1-ethoxy butane via ring opening,which is a crucial step for complete *** ReaxFF-MD simulation demonstrated that Ni facilitates the formation of H3 O free radicals and Ni-phenol inter-mediates.H3 O free radicals can be decomposed into H2 and OH free *** the generated OH free radical and Ni-phenol intermediate promote the ring-opening reaction of *** promotes the direct decomposition of phenol into C1,C2,and C3 fragments,which is beneficial for further complete gasification.

关键词： Supercritical water gasification Phenol degradation Ring opening process ReaxFF-MD

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Experimental Study on Heat Transfer Characteristics of Supercritical Carbon Dioxide in a Vertical Circular Tube

SSRN

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SSRN 2025年

作者： Yang, Haikuo Nie, Ruishan Zhang, Kui Tian, Wenxi State Key Laboratory of Multiphase Flow in Power Engineering Department of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China

Supercritical carbon dioxide (S-CO2) nuclear energy and power systems have garnered significant attention for flow and heat transfer experiments because of their compact design, advanced circulation methods, and high thermal efficiency, aligning with future trends in nuclear power plant development. However, the dramatic change in physical properties of S-CO2 near its pseudo-critical point can lead to heat transfer deterioration (HTD) in heat exchangers, potentially damaging the S-CO2 Brayton system. This paper presents an experimental study on the HTD of S-CO2 in a vertical circular tube under forced circulation, examining how heat flux, inlet temperature, and system pressure influence *** analysis delves into the mechanisms of HTD, focusing on the buoyancy and flow acceleration effects. Additionally, the study explores the impact of heat flux and system pressure on S-CO2 natural circulation. Ultimately, the research summarizes the flow and heat transfer characteristics of S-CO2 and proposes a new heat transfer correlation formula, demonstrating an error margin within ±25%, which meets practical engineering requirements. This experimental study contributes valuable data to the understanding of flow and heat transfer phenomena in S-CO2, offering significant insights for future applications. © 2025, The Authors. All rights reserved.

关键词： Nuclear energy

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MULTIPLE SOLVERS FOR IMPLICIT TEMPERATURE CALCULATION OF HEAT CONDUCTION WITH THE MPS METHOD 15

MULTIPLE SOLVERS FOR IMPLICIT TEMPERATURE CALCULATION OF HEA...

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15th World Congress on Computational Mechanics and 8th Asian Pacific Congress on Computational Mechanics: Pursuing the Infinite Potential of Computational Mechanics, WCCM-APCOM 2022

作者： Li, Sijun Zhong, Yubao Cai, Qinghang Xiao, Xinkun Guo, Kailun Chen, Ronghua Tian, Wenxi Qiu, Suizheng Su, Guanghui School of Nuclear Science and Technology Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

In this study, an implicit algorithm and different solvers are applied to the Moving Particle Semi-Implicit (MPS) method for temperature calculation. The original MPS method uses an explicit method for temperature calculation and is limited by time increment due to diffusion number. In this paper, the heat conduction of plates with Dirichlet boundary condition and Neumann boundary condition is studied. The accuracy of explicit and implicit calculation of plate heat transfer cases are compared. In addition, different solvers are compared. Consequently, it is shown that the error of the implicit algorithm is not much different from the original one. And CG is still the better solver, CGS is also a superior solver. The implicit algorithm increases the size of a single time step by a maximum of 50 times (original diffusion number is 0.2), while the calculation time of a single time step does not increase Substantially, so it has a significant effect on the acceleration of calculation. © 2022 WCCM-APCOM 2022 - 15th World Congress on Computational Mechanics and 8th Asian Pacific Congress on Computational Mechanics: Pursuing the Infinite Potential of Computational Mechanics. All rights reserved.

关键词： Heat conduction

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