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Experimental Study on flow Boiling and Circumferential Non-Uniform Heat Transfer Characteristics in Helically-Coiled Tube Under Coupled Heat Transfer Conditions

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SSRN 2024年

作者： Wang, Hengyuan Xuan, Qiyu Lei, Hailin Li, Xi Li, Zhibin Li, Huixiong State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China

Because of its compact structure and high energy conversion efficiency, helically-coiled tube steam generator has been widely used in nuclear reactor, energy power, petrochemical and other systems. In the liquid metal reactor, the liquid metal on the primary side of the helically-coiled tube steam generator washes the helically-coiled tube bundles, and exchanges heat with the water on the secondary side. Due to the coupled heat transfer between liquid metal and water, the distribution of the wall temperature or heat transfer coefficient of helically-coiled tube are significant different in the circumference direction of the tube cross-section. An experimental system of helically-coiled tube steam generator was set up in this paper. The non-uniform heat transfer characteristics of secondary side fluid of helically-coiled tube steam generator were studied under the coupled heat transfer conditions between the heat transfer of primary side and secondary sides fluid. It was found the local wall temperature or local heat transfer coefficient in the circumferential direction of the tube cross-section was significantly different, and they showed different change trends with the change of the parameters such as subcooling degree, mass flux of the secondary side fluid, system pressure of secondary side fluid, heating temperature of primary side fluid, etc. Secondly, ηt and ηh were defined to represent the degree of local non-uniformity of local wall temperature or local heat transfer coefficient in the circumferential distribution of the tube cross-section, respectively. δt and δh were defined to characterize the degree of overall non-uniformity of wall temperature or heat transfer coefficient in the circumferential distribution of the tube cross-section, respectively. The variation rules of ηt and ηh, δt and δh with subcooling degree、system pressure、mass flux of primary side fluid、mass flux of secondary side fluid and heating temperature of primary side fluid were obtained.

关键词： Steam generators

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High Concentration of CO and CO2 Inhibits Coal Gasification in Supercritical Water

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SSRN 2024年

作者： Zhang, Rui Zhao, Shuaiqi Huang, Han Zhao, Kunpeng Bai, Bofeng State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

Supercritical water gasification technology achieves efficient resource utilization of lignite and produces H2, CO and CO2. In this study, we experimentally investigated the impact of gas product generated from high concentration (>30 wt%) formic acid decomposition on the gasification of Tiebei lignite in the supercritical water. H2 promotes the pyrolysis of carbon structures, the increase in CO promotes CO2 generation through the water-gas shift reactions, and the enrichment of CO2 hinders gas diffusion. We found that high concentration of formic acid(H2, CO and CO2) inhibits the gasification of Tiebei lignite in the supercritical water. Compared with coal gasification in the supercritical water without formic acid, 30wt% formic acid reduces the carbon efficiency of lignite by 7.66%, and the mass conversion of coal by 3.97%. When the concentration of formic acid is 30wt% to 70wt%, the higher concentration of formic acid(H2, CO and CO2), the worse gasification performance of Tiebei lignite. © 2024, The Authors. All rights reserved.

关键词： Water gas shift

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Experimental Investigation on Product and Temperature Distribution in a Continuous flow Packed-Bed Reactor for Dodecahydro-N-Ethylcarbazole Dehydrogenation

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SSRN 2024年

作者： Xue, Jingwen Li, Pengzhao Yu, Pengfei Yi, Jinhao Ma, Tao Liu, Hu Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'An710049 China

The dehydrogenation of dodecahydro-N-ethylcarbazole (H12-NEC) generates enormous gas accompanied by intense heat absorption, affecting heat and mass transfer in porous catalysts. A packed-bed reactor equipped with a temperature measurement device was designed to investigate the continuous flow dehydrogenation of H12-NEC. The effects of weight hourly space velocity (WHSV), reaction temperature, catalyst particle size, and pressure were evaluated. The results reveal that the volume flow rate of hydrogen will increase with the increase of WHSV. And the generation of hydrogen enhances heat transfer by strengthening the perturbation of flow. As the temperature rises, the hydrogen yield increases along with more by-products. The decrease of catalyst particle size improves the hydrogen yield and a more uniform temperature distribution can be created within the reactor due to the weakened wall effect. 456 K and 2 mm of catalyst particle size are determined to be the optimal reaction conditions in the study, achieving the hydrogen production rate of 9.61 [[EQUATION]]. With pressure increasing, the hydrogen yield gradually decreases, but the decreased evaporation of H12-NEC results in a smaller temperature difference between the reactor and heating wall. A comparison with the thermodynamic equilibrium model reveals that the effect of pressure on chemical equilibrium may be more significant than the temperature. © 2024, The Authors. All rights reserved.

关键词： Temperature distribution

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Experimental Study on Yield and Quality of Tar from Tar-Rich Coal Under the Simulated In-Situ Conditions

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SSRN 2024年

作者： Ning, Xing Huang, Xiaole Xue, Xiangyu Wang, Chang'an Deng, Lei Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China

Tar-rich coal is considered to have a great potential to extract a large body of liquid fuels through thermal treatment. In this study, an experimental system in which the in-situ conditions can be simulated was built to investigate the yield and the quality of the tar from tar-rich coal. The simulated conditions include in-situ stress, pyrolysis temperature, heating rate, and moisture content. The results indicate that the tar yield increases from 0.83 % to 10.13 % in the temperature range of 200-500 ℃, but a considerable drop of the yield occurs around 600 ℃ due to the cracking of the tar. The heating rate is decreased from 16 °C/min to 2 °C/min, the tar yield is increased from 4.63 % to 10.3 % during the simulated in-situ pyrolysis of tar-rich coal. At low heating rates, the tar yield can be boosted owing to the difference in coal size and underground environment, in contrast to the high heating rate required in traditional coal pyrolysis. Moreover, the ether bonds connected with the oxygenated compounds in the tar under in-situ stress are cleaved, increasing the light components. For other simulated conditions, the low ratio of chain hydrocarbons to aromatic hydrocarbons leads to a decrease in the heavy components. Component variation in the tar under pyrolysis condition promotes the formation of light oil while preventing the synthesis of heavy oil, improving the quality of the tar from the simulated in-situ pyrolysis of tar-rich coal. © 2024, The Authors. All rights reserved.

关键词： Pyrolysis

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Dynamic simulation of a space gas-cooled reactor power system with a closed Brayton cycle

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Frontiers in Energy 2021年第4期15卷 916-929页

作者： Chenglong WANG Ran ZHANG Kailun GUO Dalin ZHANG Wenxi TIAN Suizheng QIU Guanghui SU Department of Nuclear Science and Technology State Key Laboratory of Multiphase Flow in Power EngineeringShaanxi Key Laboratory of Advanced Nuclear Energy and TechnologyXi’an Jiaotong UniversityXi’an 710049China

Space nuclear reactor power(SNRP)using a gas-cooled reactor(GCR)and a closed Brayton cycle(CBC)is the ideal choice for future high-power space *** investigate the safety characteristics and develop the control strategies for gas-cooled SNRP,transient models for GCR,energy conversion unit,pipes,heat exchangers,pump and heat pipe radiator are established and a system analysis code is developed in this ***,analyses of several operation conditions are performed using this *** full-power steady-state operation,the core hot spot of 1293 K occurs near the upper part of the *** 0.4$reactivity is introduced into the core,the maximum temperature that the fuel can reach is 2059 K,which is 914 K lower than the fuel melting *** system finally has the ability to achieve a new steady-state with a higher reactor *** the GCR is shut down in an emergency,the residual heat of the reactor can be removed through the conduction of the core and radiation heat *** results indicate that the designed GCR is inherently safe owing to its negative reactivity feedback and passive decay heat *** paper may provide valuable references for safety design and analysis of the gas-cooled SNRP coupled with CBC.

关键词： gas-cooled space nuclear reactor power closed Brayton cycle system startup and shutdown positive reactivity insertion accident

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Effects of Residual Carbon on Slag flow Characteristics of Zhundong High-Alkali Coal Under Oxy-Fuel Condition

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SSRN 2024年

作者： Wang, Chang'an Chen, Yuanmao Luo, Maoyun Zhao, Lin Zhao, Pengbo Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China

The implementation of oxy-fuel combustion technology in slag-tapping cyclone furnace holds significant promise for addressing the challenges associated with the combustion of Zhundong high-alkali coal. However, the flow characteristics of the Zhundong high-alkali coal slag under oxy-fuel condition remain unclear, while the influences of residual carbon have yet to be fully understood. In the present study, a high-temperature flow experimental system was designed to investigate the effects of residual carbon content, degree of graphitization of residual carbon, and atmosphere on the high-temperature flow behaviors of the high-alkali coal slag. The scanning electron microscopy (SEM) with energy dispersive spectrometer (EDS) was utilized to further analyze the microscopic characteristics and elemental distribution within the slag samples. The results reveal that under oxy-fuel condition, the flow length of slag diminishes as the content of residual carbon increases. The slag samples blended with residual carbon exhibit rougher and looser surfaces, with numerous particles adhering to them. In addition, the higher the degree of graphitization in the residual carbon, the lesser its impact on the flowability of the slag. The slag samples in oxy-fuel atmosphere display relatively smooth surfaces with dense structures and extensive liquid-phase areas. On the contrary, slag samples under inert condition feature fewer smooth surfaces, with adherent particles visible along the edges of the structure. The present research provides valuable insights into the high-temperature flow behaviors of slag in oxy-fuel combustion for Zhundong high-alkali coal in slag-tapping boilers, which can contribute to clean and efficient energy production. © 2024, The Authors. All rights reserved.

关键词： Coal

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Graph neural network-driven prediction of high-performance CO_(2)reduction catalysts based on Cu-based high-entropy alloys

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Chinese Journal of Catalysis 2025年第4期71卷 197-207页

作者： Zihao Jiao Chengyi Zhang Ya Liu Liejin Guo Ziyun Wang International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi’an Jiaotong UniversityShaanxi 710049China School of Chemical Sciences University of AucklandAuckland 1010New Zealand

High-entropy alloy(HEA)offer tunable composition and surface structures,enabling the creation of novel active sites that enhance catalytic performance in renewable energy ***,the inherent surface complexity and tendency for elemental segregation,which results in discrepancies between bulk and surface compositions,pose challenges for direct investigation via density functional *** address this,Monte Carlo simulations combined with molecular dynamics were employed to model surface segregation across a broad range of elements,including Cu,Ag,Au,Pt,Pd,and *** analysis revealed a trend in surface segregation propensity following the order Ag>Au>Al>Cu>Pd>*** capture the correlation between surface site characteristics and the free energy of multi-dentate CO_(2)reduction intermediates,a graph neural network was designed,where adsorbates were transformed into pseudo-atoms at their centers of *** model achieved mean absolute errors of 0.08–0.15 eV for the free energies of C_(2)intermediates,enabling precise site activity *** indicated that increasing the concentration of Cu,Ag,and Al significantly boosts activity for CO and C_(2)formation,whereas Au,Pd,and Pt exhibit negative *** screening stable composition space,promising HEA bulk compositions for CO,HCOOH,and C_(2)products were predicted,offering superior catalytic activity compared to pure Cu catalysts.

关键词： Density functional theory Machine learning CO_(2)reduction High entropy alloys Graph neural network

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Experimental study on combustion, ash fusibility and slagging propensity during co-combustion of organic solid waste and lignite

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Journal of the Energy Institute 2023年 106卷

作者： Liu, Hu Wang, Yancheng Xue, Jingwen Zhang, Yankang Yu, Pengfei Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Rapidly growth of organic solid waste (OSW) has caused serious social and environmental problems. Incineration as one of the most good public acceptance and environmentally friendly method attains increasing attention. In this study, the co-combustion characteristics of OSW and lignite, including the ignition and burnout temperature, ash melting and slagging propensity were studied. The experimental results show that the ignition temperature almost remains stable while the burnout temperature of the blends decreases as the increase of the OSW blending ratio, since the heat release during volatile combustion is beneficial for the burnout of coal char, but the polymer may melt and block the pores of the coal char at high temperature when the OSW blending ratio is higher than 30%. Besides, the slagging propensity of blending fuel is severe when the OSW blending ratio is 30%, and special attention should be paid to avoid slagging during the combustion process. © 2022 Energy Institute

关键词： Lignite

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Rotor dynamic analysis of supercritical carbon dioxide Bryton cycle coaxial integrated unit 14

Rotor dynamic analysis of supercritical carbon dioxide Bryto...

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14th IEEE Global Reliability and Prognostics and Health Management Conference, PHM-Hangzhou 2023

作者： Xu, Xiaokang Yang, Yi Wang, Jiangfeng Lou, Juwei Chen, Liangqi State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an China Laboratory of Science and Technology on Integrated Logistics Support College of Intelligence Science and Technology National University of Defense Technology Changsha China

ISBN: (纸本)9798350301359

The rotor system plays a very important role in supercritical carbon dioxide Brayton cycle system, and its dynamic problem will directly affect the motion stability and safety of the whole unit. In this paper, the rotor dynamic model of supercritical CO2 coaxial unit is established by finite element method, and the critical speed, modal shape and unbalance response of the rotor are studied. The first seven critical speed of the rotor and the first seven natural frequency of the rotor at the working speed are calculated. The bending modal of the rotor and the position where the rotor amplitude is the largest are analyzed, which can provide reference for the optimization design of the rotor stability. The influences of mass unbalances at the operational speed of rotor are analyzed. The research can provide some suggestions for the optimal design and actual operation of the supercritical CO2 coaxial integrated unit. © 2023 IEEE.

关键词： critical speed unbalance response vibration analysis

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Analysis of Different Control Strategies Considering Individual Regulation of Heat User 3

Analysis of Different Control Strategies Considering Individ...

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3rd International Conference on Electrical engineering and Mechatronics Technology, ICEEMT 2023

作者： Xun, Zhiwei Wang, Huijie Wang, Liyuan Yang, Long Gao, Yunfang Liu, Ming Guoneng Jinjie Energy Co. Ltd Yulin China Xi'an Jiaotong University Xi'an China Xi'an Jiaotong University State Key Laboratory of Multiphase Flow in Power Engineering Xi'an China

ISBN: (纸本)9798350303698

In the process of outdoor temperature change, it is beneficial to improve the comfort of thermal users to formulate adjustment and control strategies according to the actual needs of each user. In this paper, different adjustment modes are established according to the thermal comfort of users, and the control strategies of rising and cooling within 0, 30 and 60 minutes are proposed, and the indoor temperature control effect and heating energy consumption of each adjustment mode under different control strategies are analyzed. The results show that: in different modes, when the rise and cooling time increase, compared with the design room temperature, the indoor temperature difference under the control mode is smaller, but the time needed to reach stability is longer. At the same time, the total heat load is unchanged, but the total pump work decreases. © 2023 IEEE.

关键词： Energy utilization

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