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Experimental and Numerical Simulation Study on Critical Heat Flux in Narrow Rectangular Channels

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SSRN 2024年

作者： Lv, Xindi Zhang, Dalin Song, Gongle Su, Guanghui Tian, Wenxi Qiu, Suizheng State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China

Experimental investigation was performed on the critical heat flux (CHF) in narrow rectangular channels. The rectangular channel adopts single-side heating, the channel gaps were 1.3 and 1.9mm, the system pressure was 1~4Mpa, the inlet subcooling was 20~100K, and the mass flux was 200~1500 kg/(m2⋅s). The variation of CHF in vertical upward flow with different thermal parameters and geometric dimensions was studied. A three-fluid transient model was established to calculate the CHF of vertical upward annular flow in narrow rectangular channel. The calculation model was validated with CHF experimental data and the results were in good agreement. Combining experimental and theoretical research results, it could be concluded that the mass flow rate played an important role in the critical heat flux phenomenon of narrow rectangular channel, and its magnitude directly affected the effect of changes in thermal parameters such as pressure, mass flow rate and inlet subcooling on CHF. © 2024, The Authors. All rights reserved.

关键词： Heat flux

Comprehensive Performance Analysis of Steam and Flue Gas Stepwise/Staged Heating Molten Salt Thermal Storage Systems Coupled with Coal-Fired power Plants

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SSRN 2024年

作者： Jing, Hao Wang, Dengliang Chen, Weixiong Zhao, Yongliang Wang, Chaoyang Zhang, Kezhen Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Xi’an Thermal Power Research Institute Co. Ltd. Xi’an710054 China

The rapid development of renewable energy has put forward higher requirements for the flexibility and deep peak shaving ability of coal-fired power plants (CFPPs). Molten salt thermal energy storage (TES) is considered a potential solution. In this study, a CFPP coupled steam and flue gas stepwise/staged heating molten salt TES system is proposed. The proportion of steam thermal energy allocated to the molten salt and feed water is adjusted. The thermodynamic and economic performance of two configurations under different thermal load distribution ratios are compared and studied. The results show that with the increase of molten salt thermal load distribution ratio, the thermal storage capacity, denitrification efficiency, and charging exergy loss increase, while the equivalent round-trip efficiency, energy storage density, and discharging exergy loss decrease. When the molten salt thermal load distribution ratio is the same, the stepwise configuration has higher energy storage density and denitrification efficiency, lower charging exergy loss of TES, and better economic performance. The staged configuration has higher thermal storage capacity and lower exergy loss of CFPP. In general, the economic performance of the stepwise configuration is higher, while the staged configuration's thermodynamic performance is higher. © 2024, The Authors. All rights reserved.

关键词： Coal fired power plant

Dense fluid transport through nanoporous graphene membranes in the limit of steric exclusion

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Physical Review Fluids 2024年第4期9卷 044202-044202页

作者： Runfeng Zhou Mathew M. Swisher Akshay Deshmukh Chengzhen Sun John H. Lienhard Nicolas G. Hadjiconstantinou Department of Mechanical Engineering Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 China Center for Computational Science & Engineering Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA

We investigate transport of dense fluid flow through nanoporous membranes in the limit of steric exclusion using molecular dynamics (MD) and finite element simulations. Simulation results suggest that, for simple fluids, deviations from Sampson flow are a consequence of the competition between slip and finite atomic size effects. The latter manifest themselves by introducing an effective pore size, as well as an effective membrane thickness. We propose an analytical model for the membrane permeance that accounts for all these factors. We also show how this model can be modified to describe transport of low molecular weight aromatic hydrocarbons across these membranes in the steric limit. Extensive validation of this model is conducted through MD simulations of Lennard-Jones fluids permeating single- and multilayer graphene membranes, as well as low molecular weight organic liquids permeating single-layer graphene membranes.

关键词： Nanofluidics Finite-element method Molecular dynamics

Intra-Ring Bridging:A Strategy for Molecular Design of Highly Energetic Nitramines

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Chinese Journal of Chemistry 2021年第10期39卷 2857-2864页

作者： Linyuan Wen Tao Yu Weipeng Lai Jinwen Shi Maochang Liu Yingzhe Liu Bozhou Wang State Key Laboratory of Fluorine&Nitrogen Chemicals Xi'an Modern Chemistry Research InstituteXi'anShaanxi710065 China International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi'an Jiaotong UniversityXi'anShaanxi 710049China

Main observation and conclusion Important progress has been made in the development of energetic molecules with high performance by computer-aided molecular design in recent years,but structural novelty of organic scaffolds is *** this work,we propose an intra-ring bridging strategy inspired by the known energetic nitramines to design novel polycyclic and cage energetic *** than 100 energetic structures were designed by introducing the C—C bridges and increasing the ring *** synthesis difficulty is considered besides the two most concerned properties of EMs,energy and *** a comprehensive estimation,a symmetric cage molecule labeled as 8U-30 was finally selected because of its relatively high detonation performance,and comparable impact sensitivity as well as synthetic accessibility with ***,the proposed strategy could be utilized in further molecular design to gain various scaffolds,especially cage structures,for different demands.

关键词： Molecular modeling Energetic materials Cage compounds Computational chemistry Nitramines

Experimental studies of ash film fractions based on measurement of cenospheres geometry in pulverized coal combustion

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Frontiers in Energy 2021年第1期15卷 91-98页

作者： Siqi LIU Yanqing NIU Liping WEN Yang LIANG Bokang YAN Denghui WANG Shi'en HUI State Key Laboratory of Multiphase Flow in Power Engineering Department of Thermal EngineeringSchool of Energy and Power EngineeringXi'an Jiaotong UniversityXi'an 710049China

In pulverized coal particle combustion, part of the ash forms the ash film and exerts an inhibitory influence on combustion by impeding the diffusion of oxygen to the encapsulated char core, while part of the ash diffuses toward the char core. Despite the considerable ash effects on combustion, the fraction of ash film still remains unclear. However, the research of the properties of cenospheres can be an appropriate choice for the fraction determination, being aware that the formation of cenospheres is based on the model of coal particles with the visco-plastic ash film and a solid core. The fraction of ash film X is the ratio of the measuring mass of ash film and the total ash in coal particle. In this paper, the Huangling bituminous coal with different sizes was burnt in a drop-tube furnace at 1273, 1473, and 1673 K with air as oxidizer. A scanning electron microscope (SEM) and cross-section analysis have been used to study the geometry of the collected cenospheres and the effects of combustion parameters on the fraction of ash film. The results show that the ash film fraction increases with increasing temperature and carbon conversion ratio but decreases with larger sizes of coal particles. The high fraction of ash film provides a reasonable explanation for the extinction event at the late burnout stage. The varied values of ash film fractions under different conditions during the dynamic combustion process are necessary for further development of kinetic models.

关键词： ash film fraction cenospheres coal combustion fly ash

Morphology Construction of Molybdenum Doped Nickel Sulfide Electrocatalyst Induced by Nh4f to Promote Hydrogen Evolution Reaction

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SSRN 2024年

作者： Zhang, Baikai Li, Xiaohui Liu, Maochang Huadian Electric Power Research Institute Co. Ltd. Zhejiang310030 China School of Eenergy and Power Engineering Xi’an Jiaotong University Shaanxi 710049 China State Key Laboratory of Multiphase Flow in Power Engineering China

Here, by varying the mass of NH4F throughout the hydrothermal process, Mo-doped nickel-based sulfide catalysts (Mo-NiS-Fx) with various morphologies (prisms, rods, flakes, and cones) were created. Among these, the flaky Mo-NiS-F1.2 exhibited exceptional performance towards electrochemical hydrogen evolution reaction, surpassing most similar catalysts with an overpotential of 79 mV at 10 mA cm-2 and a Tafel slope of 49.8 mV dec-1. Significantly, Mo-NiS-F1.2 maintained its high activity for hydrogen evolution over 60 h at 10 mA cm-2, making it suitable for widespread commercial application. This work demonstrates the potential of morphology manipulation to enhance catalytic activity. © 2024, The Authors. All rights reserved.

关键词： Hydrogen

Improved filtered mesoscale interphase heat transfer model

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Particuology 2021年第4期19卷 176-186页

作者： Yu Li Yaxiong Yu Chi Zhang Zheqing Huang Qiang Zhou School of Chemical Engineering and Technology Xi’an Jiao Tong UniversityXi’an 710049China AVIC Xi’an Flight Automatic Control Research Institute Xi’an 710049China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiao Tong UniversityXi’an 710049China

Mesoscale structures that form in gas-solid flows considerably affect interphase heat transfer.A filtered interphase heat transfer model accounts for the effects of unresolved mesoscale structures is required in coarse-grid *** the literature,researchers obtain the filtered interphase heat transfer coefficient using a correction(Q)to the microscopic interphase heat transfer *** models are based on filtered data in the range 01 is *** percentage can reach approximately 20%when the dimensionless filter size is smaller than 1.028(66.7×the particle diameter).We proposed an improved filtered interphase heat transfer model by considering the data in the range Q<0 and Q>*** evaluated the predictive power of our model in an a priori *** model has much better performance than other models when the dimensionless filter size△<8.222.

关键词： Gas-solid flows Two-fluid model Interphase heat transfer Filtered model Mesoscale

Boosting photocatalytic water vapor splitting by the integration of porous g-C_(3)N_(4)and carbonized melamine foam

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Science China Materials 2024年第9期67卷 2957-2964页

作者： Shujian Wang Dongjie Liu Chunyang Zhang Jie Huang Shidong Zhao Kejian Lu Biao Wang Hao Peng Yitao Si Maochang Liu International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi’an Jiaotong UniversityXi’an710049China School of Chemistry and Chemical Engineering Southeast UniversityNanjing211189China Suzhou Academy of Xi’an Jiaotong University Suzhou215123China Gree Altairnano New Energy Inc. Zhuhai519040China

We report a photothermally-induced liquid-solid/gas-solid-decoupling photocatalytic water-splitting system,where a carbonized melamine foam(CMF)and a porous g-C_(3)N_(4)(PCN)serve as the photothermal substrate and model photocatalyst,***,liquid water is transformed into the gaseous phase over the CMF due to the photothermal effect,and the generated vapor can be split into hydrogen by PCN via the *** unique biphasic photocatalytic system exhibits a high hydrogen production rate of 368.1µmol h^(-1),which is 2.4 and 25.6 times larger than those of the traditional triphasic PCN system(151.7µmol h^(-1))and g-C_(3)N_(4)(CN)system(14.4µmol h^(-1)),*** improved photocatalytic performance is mainly attributed to the optimized energy and mass transfer at the gas-liquid-solid reaction interface,where gas products are rapidly desorbed in the photocatalytic *** work provides a novel strategy to enhance the photocatalytic performance from the perspectives of energy and mass flow.

关键词： photocatalytic photothermal mass transfer g-C_(3)N_(4) gas-solid

Sub- and Supercritical Water Flooding for Enhanced Oil Recovery in High Water Cut Heavy Oil Reservoirs: An Experimental Study

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SSRN 2024年

作者： Miao, Yan Zhao, Qiuyang Huang, Zujie Zhao, keyu Zhao, Hao Guo, Liejin Wang, Yechun State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Xinjin Weihua Institute of Clean Energy Research Foshan528216 China

High water cut poses a formidable challenge for heavy oil reservoirs, necessitating a strategy to enhance oil recovery. This study introduces a green-efficient approach - Supercritical Water Flooding (SCWF), suitable for sandstone heavy oil reservoirs with high water cut, compared to conventional subcritical water flooding and steam flooding. A novel experimental system (450°C,30MPa) was established to conduct SCWF experiments for heavy oil from Shengli Oilfield. The results showed that SCWF at 400°C and 25MPa had the recovery factor of 96.27% and the viscosity reduction rate of 61.6% for GD heavy oil. The dynamic process of SCWF is divided into three stages: pressure rising drainage stage, heating and depressurization stage, and miscible flooding stage. Analysis indicates that the high diffusivity, solubility and reactivity of supercritical water make thermal fluid breakthrough, miscible flooding and aquathermolysis reactions become the key mechanisms for high oil recovery and in situ upgrading of SCWF for high water cut heavy oil reservoirs. © 2024, The Authors. All rights reserved.

关键词： Crude oil