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High-Quality Critical Heat Flux in Horizontally Coiled Tubes

Journal of Thermal Science 1995年第3期4卷 205-211页

作者： Weimin Ma Mingyuan Zhang Xuejun Chen (state {1. laboratory of multiphase flow in power engineering, Xi’an Jiaotong Universityt Xi’an 71.049, China) State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an China

An investigation on the high-quality dryout in two electrically heated coiled tubes with horizontally helix axes is reported. The temperature profiles both along the tube and around the circumference are measured, and it is found that the temperature profiles around the circumference are not idelltical for the cross-sections at different parts of the coil. The 'local condition hypothesis' seems applicable under present conditions, and the critical heat flux qcr decreases with increasing critical quality xcr The CHF increases as mass velocity and ratio of tube diameter to coil diameter (d/D) increases, and it seems not to be effected by the system pressure. The CHF is larger with coils than that with straight tubes, and the difference increases with increasing mass velocity and d/D.

关键词： horizoatally coiled tube critical heat flux.

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Preparation of biochar adsorption material from walnut shell by supercritical CO_(2)pretreatment

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Biochar 2024年第1期6卷 168-185页

作者： Zitong Zhuang Yanbing Liu Wenwen Wei Jinwen Shi Hui Jin State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049People’s Republic of China.

In order to treat dyes in the wastewater of the printing industry and to reutilize walnut shell(WS)waste gener-ate economic benefits,supercritical carbon dioxide(SC-CO_(2))pretreatment technology was developed to prepare porous biochar as a precursor for adsorption *** experiments were conducted at the temperatures of 200,300,and 400℃with durations of 20,40,and 60 min,and a control group was set up using N_(2)***,KOH activation was employed to prepare biochar adsorption *** biochars were analyzed and characterized using TGA,BET,SEM,FT-IR,and XRD,and the liquid and gas phase products of the pretreatment process were analyzed semi-quantitatively and quantitatively using GC-MS and gas *** blue(MB)dye was selected as an indicator to measure the adsorption capacity of biochar,and adsorption kinetics were analyzed based on the *** results indicate that pretreatment with SC-CO_(2)effectively enhanced the performance and yield of the activated *** highest specific surface area increased by 1.%,and the maximum adsorption of MB increased by 23%compared to the N_(2)control *** yield increased by 8-262%and the specific surface area increased by 50-1.2%compared to the direct activation of walnut shell(WS).During the pretreatment processes for the preparation of biochar adsorption material with the best specific surface area,phenol-enriched bio-oil was produced as a by-product which has economic value.

关键词： Supercritical carbon dioxide Walnut shell Biochar Methylene blue adsorption

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Numerical Investigation of Developing Turbulent flow in a Helical Square Ductwith Large Curvature

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Journal of Thermal Science 2001年第1期10卷 1-6页

作者： Gao Hui,Guo Liejin (state {1. laboratory of multiphase flow in power engineering, Xi’an Jiaotong University, Xi’an 71.049, China ) State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an China

A fully elliptic numerical study has been carried out to investigate the three-dimensional turbulent developing flow in a helical square duct with large curvature. A two-layer zonal model is proposed and used, in which the whole region is divided into a viscosity-affected near wall layer and a fully turbulent region. A DSM closure is applied in the former, and a one-equation model is solved in the latter. The results presented in this paper cover a Reynolds number range of (l- 1.) x 1.4. The development of flow is found to be dominated by radial pressure gradient and Dean-type secondary motion. The distribution of Reynolds stresses in fully developed flow exhibit a complex pattern of turbulence anisotropy The development of peripherally averaged friction factor and the distribution of local friction factor in fully developed flow are given and discussed.

关键词： curved pipe developing flow turbulence model numerical simulation.

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Thermo-economic analysis and optimization of a novel self-condensing transcritical CO 2 power cycle with ejector refrigeration

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Process Safety and Environmental Protection 2025年 199卷

作者： Jiaxi Xia Jingjing Hou Jiangfeng Wang Juwei Lou Yumin Guo School of mechanical and Electrical Engineering Henan Agricultural University Zhengzhou 450002 China State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an 710049 China

The transcritical CO 2 power cycle stands out as a promising approach for the utilization of waste heat and renewable energy, but its practical application is restricted by the condensation challenges of working fluid. To tackle this issue, a novel self-condensing transcritical CO 2 power cycle (SC-TCO 2 PC), which integrates the transcritical CO 2 power cycle with an ejector refrigeration cycle, is proposed. Detailed mathematical models are formulated, and parametric study is carried out to illustrate the correlations between the crucial parameters and system performance from both thermodynamic and economic viewpoints. Then a multi-objective optimization is applied to explore the potential for performance enhancement. Furthermore, the comparative analysis of the SC-TCO 2 PC and the recuperative supercritical CO 2 Brayton cycle (SCO 2 BC) are conducted under optimized conditions. The results demonstrated that the enhanced turbine inlet pressure and temperature positively influence the thermal-economic performance of the SC-TCO 2 PC. Furthermore, the maximum thermal efficiency of 43.90 %, exergy efficiency of 72.97 % and minimum cost per unit of electricity of 0.0372$/kWh are attainable for the SC-TCO 2 PC, reflecting the improvements of 4.88 %pt for maximum thermal efficiency, 6.60 %pt for maximum exergy efficiency and a 8.87 % reduction for minimum unit power cost in comparison to the recuperative SCO 2 BC. In optimum conditions, the SC-TCO 2 PC is capable of achieving a thermal efficiency of 42.1. % and an exergy efficiency of 70.54 % with the cost per unit of electricity of 0.0440$/kWh.

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Recent advances in nonmetallic atom-doped metal nanocrystals:Synthesis and catalytic applications

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Chinese Chemical Letters 2021年第9期32卷 2679-2692页

作者： Ruiyun Guo Ke Zhang Shangdong Ji Yangzi Zheng Mingshang Jin Frontier Institute of Science and Technology and State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

Metal nanocrystals have been recognized as the main catalytic materials in many fields,but insufficient activity and stability,as well as high prices,have limited their large-scale potential *** one of the extremely promising alternatives toward metal in boosting their catalytic performance,nonmetallic atoms-doped metal nanocrystals have recently received extensive attention because of their high efficiency,chemical and structural durability,abundant reserve,and low *** this review,we highlight the most recent progress in this field and provide insights into their catalytic *** metalnonmetal nanocrystals prepared by doping metal nanocrystals with nonmetallic atoms are introduced and classified based on the types of nonmetallic atoms,including metal hydrides,borides,carbides,nitrides,oxides,phosphides,and ***,their applications in catalysis,especially in electrocatalysis and organic catalysis,have been summarized and ***,the conclusions and perspectives are given for the catalysis-driven rational design of metal-nonmetal nanocrystals in this minireview.

关键词： Nonmetallic atom-doping Metal-nonmetal nanocrystals Organic catalysis Electrocatalysis Catalyst design

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Thermal and film dynamics of multi-nozzle flash spray cooling towards large area and non-uniform heat source

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Thermal Science and engineering Progress 2025年 63卷

作者： Xiang-Wei Lin Xu-Dong Wang Zhi-Fu Zhou Dong-Qing Zhu Wen-Wei Xu Hai Zhu State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an 710049 China Huawei Technologies Co. Ltd. Shenzhen China

Thermal management poses a crucial challenge to the operational reliability of high-power devices which characterized by large area and uneven heat sources. Flash spray, as one of the start-of-the-art technologies, satisfies the requirements of rapid heat removal and superior droplet breakup effects. This study aims to investigate the liquid dynamics and heat transfer characteristics of multi-nozzle flash spray on a non-uniform heat flux surface. Here, the Euler-Lagrangian method is coupled to account for the gas-droplet interactions, and the Lagrangian wall-film is applied to describe the liquid film evolution. The effects of spray height and nozzle number are systematically discussed in terms of velocity, liquid film thickness, average surface temperature, and temperature non-uniformity. Results reveal that the enhanced spray-to-spray interaction can greatly alter liquid film distribution, which in turn affects the heat transfer efficiency. Notably, while increasing spray coverage improves thermal contact area, it exhibits a non-linear relationship with temperature reduction, showing an optimal spray height and nozzle number for minimizing average temperature and temperature non-uniformity. The main contribution of present work lies in its in-depth analysis of multi-nozzle flash spray on large area and uneven heating surface, which is prevalent in industrial applications buy underexplored in prior works. These findings are expected to offer actionable guidelines for understanding complex spray cooling mechanisms and designing efficient thermal management systems.

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Improving sampling depth of laser speckle imaging by topical optical clearing:A theoretical and in vivo study

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Journal of Innovative Optical Health Sciences 2020年第2期13卷 33-43页

作者： D.Li Y.Zhang B.Chen State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049P.R.China

The effect of optical cleaning method combined with laser speckle imaging(LSI)was discussed to improve the detection depth of LSI due to high scattering characteristics of skin,which limit its clinical application.A double-layer skin tissue model embedded with a single blood vessel was established,and the Monte Carlo method was used to simulate photon propagation under the action of light-permeating agent.808 nm semiconductor and 632.8 nm He–Ne lasers were selected to study the e®ect of optical clearing agents(OCAs)on photon deposition in *** show that the photon energy deposition density in the epidermis increases with the amount of tissue°uid replaced by *** with glucose solution,polyethylene glycol 400(PEG 400)and glycerol can considerably increase the average penetration depth of photons in the skin tissue,thereby raising the sampling depth of the *** the action of glycerol,PEG 400,and glucose,the average photon penetration depth is increased by 51.78%,51.06%,and 21.51.for 808nm,68.93%,67.94%,and 26.67%for 632.8 nm lasers,*** vivo experiment by dorsal skin chamber proves that glycerol can cause a substantial decrease in blood°ow rate,whereas PEG 400 can signicantly improve the capability of light penetration without a®ecting blood velocity,which exhibits considerable potential in the monitoring of blood°ow in skin tissues.

关键词： Laser speckle image topical optical clearing imaging depth Monte-Carlo simulation dorsal skin experiment

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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 1.93 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 91. 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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Experimental and modeling investigation of zero net liquid flow in hilly terrain pipeline

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Petroleum Science 2025年

作者： Huang, Bo Xu, Qiang Chang, Ying-Jie Cao, Ye-Qi Yu, Hai-Yang Li, Yu-Wen Guo, Lie-Jin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Shaanxi Xi'an 710049 China College of Petroleum Engineering Xi'an Shiyou University Shaanxi 710065 China

Hilly terrain pipeline is a common form of pipeline in oil and gas storage and transportation industry. Due to the hilly terrain influence, the liquid at the elbow of the gathering pipeline is easy to flow back and accumulate to form slug flow, so it is necessary to remove the accumulated liquid by gas purging. In this paper, experiment is carried out in hilly terrain pipelines. Three flow patterns of stratified flow, slug flow and stratified entrained flow are observed. The process of gas purging accumulated liquid is divided into four stages, namely liquid accumulation, liquid rising;continuous outflow and tail outflow. At the same time, the flow pattern maps of each stage are drawn. The pressure drop signal is analyzed in time domain and frequency domain, and the contour map of pressure drop distribution is drawn. It is found that the ratio of range to average value can well distinguish the occurrence range of each flow pattern. Based on visualization, the transition process of slug flow to stratified flow and stratified entrained flow is studied, and the transition boundary prediction model is established. An image processing method is proposed to convert the image signal into a similarity curve, and PSD analysis is performed to calculate the slug frequency. The normal distribution is used to fit the slug frequency, and the predicted correlation is in good agreement with the experimental data. © 2025 The Authors

关键词： flow pattern transition Hilly terrain pipeline Quantitative image processing Slug flow Zero net liquid flow

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Investigation of the transfer ionization process in collisions of partially stripped ions on He

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Chinese Physics B 2010年第6期19卷 277-282页

作者：刘会平陈熙萌欧阳晓平席发元苏光辉 State Key Laboratory of Multiphase Flow in Power Engineering Department of Nuclear Science and TechnologyXi'an Jiaotong University School of Nuclear Science and Technology Lanzhou University

In this paper a projectile ion-recoil ion coincidence technique is used to investigate the transfer ionization processes in collisions of 0.22-6.30 MeV Cq＋ ions and 0.25-6.35 MeV 0q＋ ions （q=1. 2, 3, 4） with the He atom separately. The cross section ratio f of transfer ionization to single electron transfer is measured, and the dependence of f on both charge state q and energy E of the projectiles is investigated. The electron-structure and the mechanisms leading to transfer ionization affect the dependence of f on q and E. Our measurements, along with other data published previously, suggest a similar dependence of f on charge state and energy of projectile for partially stripped ions over a large energy range. The maximum value of f is approximately 0.1.q^0.60; the energy corresponding to maximum f is about 1.0q^0.60 keV/u.

关键词： ion atom collision transfer ionization single electron transfer

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