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Investigation on a Supercritical Water Gasification System with CO_(2)as Transporting Medium

Journal of Thermal Science 2023年第4期32卷 1614-1625页

作者： WANG Weizuo LU Bingru SHI Jinwen ZHAO Qiuyang JIN Hui State Key Laboratory of Multiphase Flow in Power Engineering(SKLMF) Xi’an Jiaotong UniversityXi’an710049China

As a benign energy vector,hydrogen has been discussed for a long *** water gasification was one of good ways to produce ***,supercritical water gasification system with H_(2)O transporting was energy consuming in the process of heating due to the high specific heat of H_(2)O.A new supercritical water gasification system was established in this paper with supercritical CO_(2)as medium *** plastics were used as the sample transported by CO_(2).Production yields,energy flow and exergy flow of the system were collected and the influence of temperature,pressure,gasification concentration and transporting concentration was *** flow of H_(2)O input into the reactor was 1000 kg/*** typical condition was as follow:temperature 923.15 K,pressure 23 MPa,and the mass ratio of water,sample and transporting medium was 100:9:*** of H_(2),CH4,CO and CO_(2)at this condition was 8.1 kg/h,39.6 kg/h,6.6 kg/h and 137.5 kg/h,*** system with H_(2)O transporting was used to compare with the supercritical CO_(2)transporting system and proved that system with CO_(2)transporting could reduce the loss of both energy and exergy while the reduce of each gas production yield was less than 0.1 mol/mol.

关键词： phenolic plastics supercritical water gasification CO_(2)-transporting system energy and exergy flow

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Study on the Enhancement Effect of Dielectric Barrier Discharge on the Premixed Methane/Oxygen/Helium Flame Velocity

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Plasma Science and Technology 2015年第12期17卷 1019-1026页

作者：穆海宝喻琳李平汤成龙王金华张冠军 State Key Laboratory of Electrical Insulation and Power Equipment School of Electrical EngineeringXi'an Jiaotong University State key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

Recently,plasma-assisted combustion has become a potentially applicable technology in many combustion *** this paper,a dielectric barrier discharge（DBD） plasma generator is designed to explore the effect of plasma on the CH4 oxidation process,and several properties of combustion are ***,in the presence or absence of plasma discharge,physical appearance of the flame is examined and ***,the flame propagation velocity is calculated by the flame front extracted from the imaging data with the Bunsen burner ***,the main molecular components and their intensity variation in the flame and the plasma zones are identified with an emission spectrograph to analyze the effect of active species on the combustion *** also discuss the possible kinetic regime of plasma-assisted *** results imply that plasma discharge applied to the premixed CH_4/O_2/He mixture significantly raises the flame speed with equivalence ratios ranging from 0.85 to 1.10,with the flame speed improved by 17%to 35%.It can be seen that plasma can improve methane oxidation efficiency in the premixed fuel/oxidizer,especially at a low equivalence ratio.

关键词： combustion flame Oxygen equivalence appearance Velocity scenarios burning camera hydrocarbon

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A computational particle fluid-dynamics simulation of hydrodynamics in a three-dimensional full-loop circulating fluidized bed: Effects of particle-size distribution

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Particuology 2020年第2期18卷 134-145页

作者： Hang Zhang Youjun Lu State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049ShaanxiChina

A computational particle fluid-dynamics model coupled with an energy-minimization multi-scale(EMMS)drag model was applied to investigate the influence of particle-size distribution on the hydrodynamics of a three-dimensional full-loop circulating fluidized *** particle systems,including one monodisperse and two polydisperse cases,were *** numerical model was validated by comparing its results with the experimental axial voidage distribution and solid mass *** EMMS drag model had a high accuracy in the computational particle fluid-dynamics simulation of the three-dimensional full-loop circulating fluidized *** total number of parcels in the system(Np)influenced the axial voidage distribution in the riser,especially at the lower part of the *** numerical simulation results showed that axial segregation by size was predicted in the two polydisperse cases and the segregation size increased with an increase in the number of size *** axial voidage distribution at the lower portion of the riser was significantly influenced by particle-size ***,radial segregation could only be correctly predicted in the upper region of the riser in the polydisperse case of three solid species.

关键词： Circulating fluidized bed Computational particle fluid dynamics Particle-size distribution Energy-minimization multiscale model Three-dimensional full-loop simulation

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Fluidization of particles in SCW fluidized bed:Voidage distribution of emulsion phase

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Particuology 2022年第4期20卷 60-75页

作者： Hao Wang Youjun Lu State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049ShaanxiChina

Supercritical water(SCW)fluidized bed reactors convert biomass to fuels without pollutants *** this work,experimental studies were carried out to investigate voidage distribution in an SCW fu-idized bed by capacitance *** sands with different particle sizes were fluidized by SCW under system pressure of 20-27 MPa and temperature of 410-570℃.The effect of operation conditions on voidage distributions of the emulsion phase(*** voidage and probability density)is discussed.A predicting correlation between voidage and superficial velocity in emulsion phase is *** relative error of the correlation is within+25%.These research results provide useful guidance for the optimization of supercritical water gasification technology.

关键词： Supercritical water fluidized bed Capacitance probe measurement system Voidage distribution

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Instantaneous mixing characteristics of binary mixtures differing in density in a gas-solid fluidised bed

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Particuology 2020年第6期18卷 63-71页

作者： Zhen Wan Youjun Lu Hao Wang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049ShaanxiChina

Characterisations of instantaneous mixing behaviours in fluidised beds with binary mixtures has many *** studied the instantaneous mixing characteristics of binary mixtures in a 2-D quasi gas-solid fluidised bed using a capacitance probe *** method enabled the quantitative assessment of instantaneous mixing behaviours,including mixing index,rate,and *** kinds of binary mixtures of similar size but different density were used for the transient and steady fluidisation experiments in a bubbling fluidised *** mixing curves of initially segregated binary mixtures were acquired,and the instantaneous characteristics for the entire process were *** equation was proposed to describe the mixing process and predict the mixing degree over *** comparing experiments with different working conditions,the effects of superficial gas velocity and density ratio on the mixing in the centre and at the wall of the fluidised bed were *** the stable fluidisation stage,the axial concentration profiles of the mixtures were obtained,and the mechanisms of mixing were *** showed that the mixing level increased logarithmically with time and eventually reached a relatively stable *** the superficial gas velocity and reducing the density ratio promoted mixing and reduced mixing *** superficial gas velocities tended to mix the mixtures well and quickly,regardless of the density ratio of the two components.

关键词： Binary mixtures Fluidised bed Mixing Instantaneous characteristics

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Thermally induced non-coalescence of compound droplets

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Applied Thermal engineering 2025年 276卷

作者： Jianmei Zhao Xing Li Bofeng Bai State Key Laboratory of Multiphase Flow in Power Engineering School of Chemical Engineering and Technology Xi’an Jiaotong University Xi'an 710049 China

Compound droplets surrounded by a gaseous phase with different temperatures widely exist in industrial applications. Previous research has focused on thermally induced non-coalescence or delayed coalescence between two single-phase droplets or a droplet and a liquid bath. The primary mechanism is the levitated intervening pressure in the lubricating air layer between droplets, which is caused by the thermocapillary convection. In this study, the non-coalescence of two compound droplets in a cold ambient air environment is experimentally investigated. The thermocapillary mechanism manifests three distinct features. First, as the two compound droplets approach each other, the temperature of the contact side of each droplet increases because of reduced heat loss, a phenomenon termed as the contact-side heating effect. This creates a surface temperature gradient, inducing Marangoni stress and subsequent surface convection. Second, owing to the immiscibility of the two phases within each compound droplet, the thermocapillary convection develops independently in each phase, forming independent convection which cannot be observed in single-phase droplets . It was observed that the directions of the thermocapillary convection within the two droplets were correlated and always planar symmetric, which is different from the uncorrelated and opposite convection of two single-phase droplets. Third and most importantly, the thermocapillary convection in the oil phase entrains the air into the lubricating film between droplets, inhibiting their coalescence only when the oil/water interface is adjacent to the contact zone.

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Experimental investigation of enhanced heat transfer for fined circular tube heat exchanger with rectangular fins

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Journal of Harbin Institute of Technology(New Series) 2006年第4期13卷 385-390页

作者：李永星杨冬陈听宽 State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

Presents a set of data for flow and heat transfer of finned-tube bundle under the condition of high air flow velocity. Air flow and heat transfer over a 4 × 4 （ columns × rows） finned-tube heat exchanger with rectangular fins was investigated experimentally in a wind tunnel with constant wall temperatures condition. The air flow velocity based on the minimum flow cross-section area over flow channel ranged from 13.8 to 50. 2 m/s, the heal transfer rate ranged from 21.8 to47. 1 kW, and the air temperatures increase ranged from 10. 9 to 19. 8 ℃. The present results were compared with results calculated from correlations proposed by CSPE. For air flow velocity less than 25 m/s, these two results of heat transfer agreed well with each other, whereas for larger velocity, our test data disagreed with the CSPE correlations. For the friction factor, present data are much higher than the predicted results in the whole range. Finally, correlations for friction factors and heat transfer coefficients are DrODosed based on the experimental results.

关键词： haeat exchanger rectangular finned-tube enhanced heat transfer friction factor

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Optimization and renovation of energy complementary intra-plant/inter-plant integrated heat exchanger networks for waste heat recovery in the calcium carbide industry

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Process Safety and Environmental Protection 2025年 199卷

作者： Wang, Hongxia Li, Xiaoli Guo, Peinan Zhang, Zaoxiao Shi, Lei School of Chemical Engineering and Technology Xi'an Jiaotong University Xi'an710049 China State Key Laboratory of Multiphase Flow in Engineering Xi'an Jiaotong University No.28 Xianning West Road Xi'an710049 China Zhejiang Fengwang Environmental Protection Co. Ltd Zhejiang 323000 China

The calcium carbide industry, characterized by its energy and emissions intensity, faces pressing sustainability demands in the "double-carbon" era. This study identifies substantial energy-saving opportunities within heat exchange networks. An optimization method is proposed that combines intra-/inter-plant heat integration to retrofit carbide plant heat exchange networks for energy efficiency. This approach is primarily based on pinch technology, where the heat exchange was first reconstructed within subsystems to minimize utility consumption. Results indicate that the intra-plant heat integration yields energy savings of 31.49 % for subsystem 1 and 28.79 % for subsystem 2. Subsequently, excess heat and cooling loads from the optimized subsystems were extracted as new heat exchange streams, facilitating heat exchange matching between subsystems. Thus, excess heat from subsystem 1 serves as heat source, while the excess cold from subsystem 2 acts as heat sink in inter-plant integration, creating a synergistic energy-saving mechanism to achieve inter-plant heat integration. The total energy from inter-plant heat integration reaches 10.83 MW, contributing to an overall heat recovery potential of 38.55 MW, ultimately achieving a remarkable total energy saving rate while minimizing the heat exchange units in this case. This research underscores the importance of multi-energy complementarity in advancing energy efficiency for future carbide industry. © 2025

关键词： Energy efficiency

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Two-phase flow instabilities in helical tubes of once-through steam generators

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PROGRESS IN NATURAL SCIENCE 1997年第3期7卷 360-365页

作者： Zhou, FD Shi, SP Hu, MS State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Helical tube is one type of once-through stream generators in integrative nuclear device. The thermal-hydrodynamic instabilities in helical tubes of a once-through steam generator (HTOTSG) with exit-steam superheated were studied by using multi-variable liner-frequency-domain theory. Based on the drift-flux model, a small perturbation method, as well as Laplace transformation theory, was empolyed to linearize the system of partial differential equations. A computer code called HTOTSGM-D was developed to investigate the influences of inlet flow rate, inlet subcooling, heat flux, and system pressure on oscillations. The calculated results showed that the above factors must be considered comprehensively in once-through steam generator design and operation, even though the installation of the entrance throttles was still an effective way to stabilize the system.

关键词： two-phase flow instabilities helical tube once-through stream generator

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Prediction of Heat Transfer Rates for Shell-and-Tube Heat Exchangers by Artificial Neural Networks Approach

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Journal of Thermal Science 2006年第3期15卷 257-262页

作者： Qiuwang WANG Gongnan XIE Ming ZENG Laiqin LUO State Key Laboratory of Multiphase Flow in Power Engineering Xi＇an Jiaotong University Shaanxi Xi＇an710049 China

This work used artificial neural network(ANN)to predict the heat transfer rates of shell-and-tube heatexchangers with segmental baffles or continuous helical baffles,based on limited experimental *** BackPropagation (BP) algorithm was used in training the *** network configurations were *** deviation between the predicted results and experimental data was less than 2%.Comparison withcorrelation for prediction shows ANN *** is recommended that ANN can be easily used to predict theperformances of thermal systems in engineering applications,especially to model heat exchangers for heattransfer analysis.

关键词： heat transfer rate Artificial Neural Network shell-and-tube heat exchanger back propagation

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