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Numerical prediction of spatio-temporal frosting patterns of curved surface considering varying working parameters

Energy Storage and Saving 2023年第1期2卷 348-358页

作者： Xue Liu Xiaojun Dong Shaohang Yan Yu Hou Tianwei Lai State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an710049China

Accurate numerical prediction of frosting patterns is essential for the efficient layout and timing defrosting of heat exchangers under frosting *** this study,a numerical model is developed to predict the spatio-temporal frosting habits on curved surfaces in combination with the correlations of frost density and thermal *** the model,frost melting is *** verification,the frosting and heat transfer characteristics along the flow path are investigated under various structural and operating *** thickness along the path is mainly affected by the cooling surface temperature,while the heat and mass transfer rates are strongly correlated with the humidity *** proportions of latent heat and sensible heat are distributed more unevenly in parallel flow case than in counter flow *** deposition is facilitated by a smaller radius of curvature of the cooling *** uniform frosting characteristics along the path and smaller heat transfer obstruction are presented with a smaller length-to-height ratio of the flow path.

关键词： Frosting Numerical prediction Heat transfer Curved surface Varying parameter

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Experimental study on flow excursion instability of supercritical hydrocarbon fuel in scramjet regenerative cooling parallel channels

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Chinese Journal of Aeronautics 2023年第1期36卷 201-215页

作者： Xiaoyong LIU Zhuqiang YANG Ruipu MIAO Feng LIU Shujun ZHAO Qincheng BI Beijing Power Machinery Research Institute Beijing 100074China Liaoning Key Laboratory of Complex Energy Conversion and Utilization School of Energy and Power EngineeringDalian University of TechnologyDalian 116024China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China

flow instability of supercritical hydrocarbon fuel is a crucial issue in scramjet regenerative cooling structure. In this study, flow excursion instability and flow distribution in parallel tubes were experimentally studied for supercritical fluids. Two types of flow excursion occur in a single tube. Type Ⅰ and Type Ⅱ excursions, and they are corresponding to decreasing and increasing flow rate respectively. They can trigger flow maldistribution between parallel tubes and the hysteresis phenomenon of flow distribution. The effects of system parameters, including inlet temperature,system pressure, and heat flux, on flow distribution were analyzed. In addition, the relationship between flow excursion and the pseudo-critical interval proposed in the literature was established according to the heated tube outlet temperature at the onset of flow instability. Finally, the flow excursion instability boundary was obtained using two dimensionless parameters. These experimental results can provide helpful insight on the mechanism of Scramjet regenerative cooling.

关键词： flow distribution Ledinegg instability Onset of flow excursion Parallel channels Regenerative cooling Scramjet Supercritical flow

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Alloy nanocrystals:Synthesis paradigms and implications

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Chinese Journal of Structural Chemistry 2023年第11期42卷 1-5页

作者： Zhaojun Liu Zerui Mu Chuanbo Gao State Key Laboratory of Multiphase Flow in Power Engineering Frontier Institute of Science and TechnologyXi'an Jiaotong UniversityXi'an710054China

*** Noble metal nanocrystals serve as exceptional catalysts across a wide spectrum of industrial processes[1..Moreover,there exists a substantial demand for noble metal catalysts in emerging clean-energy applications,such as water-splitting hydrogen production and fuel *** non-noble transition metals or main-group metals into noble metal nanocrystals can reduce the weight of noble metals in the catalysts,thus remarkably lowering the ***,alloy nanocrystals offer intriguing catalytic properties that surpass those of their monometallic counterparts,thanks to the charge transfer between the constituent components and the expansion or shrinkage of the lattice size[2].

关键词： alloy metals noble

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Temporal and spatial non-uniformity of surface heat transfer during r404a spray cooling in laser surgery 13

Temporal and spatial non-uniformity of surface heat transfer...

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1.th International Conference on Liquid Atomization and Spray Systems, ICLASS 201.

作者： Wang, R. Zhou, Z.F. Chen, B. Bai, F.L. Wang, G.X. State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University China

Cryogen spray cooling has been applied to protect epidermis from thermal damage in laser dermatology. However, present cryogen R1.4a shows insufficient cooling capacity on minimizing the laser energy absorption by the melanin in darkly pigmented human skins. With lower boiling point, R404A has potential to improve the cooling capacity. This paper presents an experimental study on the temporal and spatial variation in surface temperature and heat flux during spray cooling using R404A by a straight tube nozzle with expansion chamber, which significantly improves the atomization effect. The experimental results indicate that the temporal and spatial conditions strongly influence the uniformity of surface heat transfer. There exists a sub-region of uniform cooling with radius of 2 mm around spray center with high transient heat flux above 400 kW/m2, which is conducive for physicians to control the therapy area precisely with enhanced laser energy. © 201. International Conference on Liquid Atomization and Spray Systems. All rights reserved.

关键词： Laser surgery

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Experimental and Theoretical Study on CHF of a Ultra-Supercritical Circulating Fluidized Bed Boiler Water-Wall Tube at near-Critical Pressures

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Journal of Thermal Science 2023年第1期32卷 166-182页

作者： WANG Wenyu MA Zhan QING Hao NIE Chao YANG Haoyu BI Lingfeng YANG Dong PAN Wenxiao State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China Department of Mechanical Engineering University of Wisconsin-Madison1513 University AveMadisonWI 53706USA

The experimental and theoretical research on the critical heat flux(CHF)in a uniformly heated water-wall tube of the efficient ultra-supercritical circulating fluidized bed(USCFB)boiler has been *** particular,the experimental pressure varies from 1. MPa to 21.MPa,which is from 0.81.Pcr–0.95Pcr(Pcr:critical pressure).The mass flux varies from 31. kg·m^(–2)·s^(–1.to 550 kg·m^(–2)·s^(–1..The inlet sub-cooling temperatures vary from 5°C to 1.°*** material of the tube is *** experimental investigation,the near critical pressure CHF test data of water are *** find that the CHF mainly occurs when the vapor qualities are less than 0.4,and it occurs earlier(at lower vapor quality)when the pressure is closer to 22.1.5 MPa or the mass flux is *** the experimental data,a correlation function for the CHF is established via regression and machine *** established via machine learning greatly improved the regression *** study the CHF phenomenon mechanically,a theoretical model is established based on the near-surface bubble crowding model describing the DNB-type *** the development of the CHF model,the friction resistance coefficient is determined according to our test *** comparison with different experimental results,the near-surface bubble crowding model is well suited to describe DNB-type *** calculation results of the model can provide reference for the optimal design of the USCFB boiler.

关键词： circulating fluidized bed critical heat flux near-critical pressure bubble crowding machine learning

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Simulation and Experiment on Elbow Wear in Pneumatic Conveying System

Simulation and Experiment on Elbow Wear in Pneumatic Conveyi...

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International Conference on power {1. 2021. ICOPE 2021

作者： Xiaole, Chen Qulan, Zhou Du, Wen Qingtian, Liu Na, Li State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University China

Elbow wear, which is most likely occurring in pneumatic conveying, becomes a key factor in development of pneumatic conveying. This paper used 3D DEM-CFD to simulate the elbow wear in pneumatic conveying system. Simulation results show that: elbow wear is linear with material mass {1. rate. Elbow wear increases along with the increasement of material particle velocity. When the velocity changes from 0 to 1.m/s, the elbow wear increases 3.1. times. Elbow wear increases while the radius of material particles is growing. When the particles radius increases from 0.1.m to 0.5mm, the elbow wear increases 1..1.%. This paper also established a complete pneumatic conveying device for experiment. In pneumatic conveying experiment, the pressure loss was measured in situations: different air{1. velocity, different velocity of material particles. The results of experiment show the same regular indicated in simulation. © 2021.The Japan Society of Mechanical Engineers.

关键词： Wear of materials

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Single-jet Spray Mixing with a Confined Crossflow

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Chinese Journal of Chemical engineering 2013年第1期21卷 14-24页

作者：孙慧娟白博峰严俊杰张海滨 State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

In order to achieve uniform mixing between spray droplets and crossflow, cold-model experiment of a hollow-cone water spray in an air crossflow is investigated via a numerical simulation. The simulation cases are designed by using the orthogonal design method. The Eulerian-Lagrangian formulation is employed for modeling the droplets-crossflow two-phase flow while the realizable k-ε turbulence model is used to describe the turbulence. A new index, mixedness quality, is proposed to assess the overall mixing of the droplets in the crossflow. The simulation results demonstrate that the counter-rotating vortex pair (CVP) imposes a more significant impact on the spatial distribution than on the size distribution of the droplets. Pairs of CVP with smaller scales are preferable for achieving a better mixing. The influencing factors are listed in the following order in terms of the degree of their impact from the greatest to the least: the Sauter diameter of the initial droplets, the mixing tube diameter, the spray angle, the velocity of the inlet crossflow, and the vertical velocity of the initial droplets. A moderate droplet diameter, a smaller tube diameter, a moderate spray angle, a greater crossflow velocity and a moderate vertical velocity of the droplet are favorable for achieving a higher mixedness quality of the jet spray in a confined crossflow.

关键词： mixing jet spray droplets crossflow numerical simulation

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Experimental study on the thermochemical reduction of supercritical CO2by guaiacol 8

Experimental study on the thermochemical reduction of superc...

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8th International Conference on Smart and Sustainable Technologies, SpliTech 2023

作者： Wei, Yimeng Kuanibieke, Jiadela Jin, Hui Xi'an Jiaotong University State Key Laboratory of Multiphase Flow in Power Engineering China

ISBN: (纸本)9789532901283

The continuous growth of CO2 emissions is one of the global problems facing humanity, and how to convert and exploit the stock of CO2 has become an urgent issue. Biomass as an activity of CO2 thermal reduction medium has become the focus of human attention in general. Supercritical CO2 (SCCO2) has the advantages of near-liquid density and high solubility, which can further strengthen the reduction process (T≥31.26, P≥72.9 atm). This paper described a SCCO2 reduction method of guaiacol on an intermittent Kettle Reactor to investigate the effects of reaction temperature (400-700), residence time (5-20 min) and reactant concentration (4 wt%-1.wt%) on the three-phase products. The experimental results indicated that the carbon gasification efficiency (CE) and hydrogen gasification efficiency (HE) were 43.7% and 56.7%, respectively, when the carbon dioxide consumption reached 1..1. mol/kg. As the temperature increased, the consumption of carbon dioxide increased and the concentration of reactants increased with opposite results. © 2023 University of Split, FESB.

关键词： Carbon dioxide

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Experimental study on the influence of the temperature and thermal Stress of water wall in different arrangements of burners

Experimental study on the influence of the temperature and t...

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International Conference on power {1. 2021. ICOPE 2021

作者： Wei, Lin Zhou, Qulan Liu, Zhuhan Li, Na State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University China

To study the water walls' safety problems of the opposed firing boiler, thermal experiments for four typical arrangements of burners conditions are run in a laboratory-scale boiler. The four working conditions include 25% rated load (four burners are arranged side by side on the front wall), 50% rated load (eight burners are all arranged on the front wall;eight burners are arranged opposed to each other on the front and rear walls) and 1.0% load (front and rear walls are filled with sixteen burners). The principal strain, principal stress and temperature distribution of the water wall under four operating conditions are drawn for comparison and analysis. In addition, the results of the thermal stress, principal main stress direction and water wall temperature of the four working conditions are counted respectively to summarize the laws of them. This study highlights the influence of the temperature and thermal stress on water walls in different arrangements of burners to guide the safe operation of water walls in the real opposed firing boiler. © 2021.The Japan Society of Mechanical Engineers.

关键词： Thermal stress

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Prediction of von Mises stress on the membrane wall in a lab-scale arch-fired boiler based on artificial neural work

Prediction of von Mises stress on the membrane wall in a lab...

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International Conference on power {1. 2021. ICOPE 2021

作者： Wen, Du Zhou, Qulan Pan, Yuqing Chen, Xiaole Li, Na State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University China

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