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Experimental Study on flow Patterns in Narrow Rectangular Channels

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SSRN 2022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 Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610041 China

Plate fuel elements are commonly used in compact nuclear reactors due to the advantages of high fuel consumption. In this paper, the two-phase flow pattern in the coolant channel of plate fuel elements, i.e. the rectangular narrow channel was studied. Visualization flow pattern experiments of upward steam-water two-phase flow in narrow rectangular channels, 745mm long and 67mm wide with gap widths of 1.3mm and 1.9mm, were investigated. The experiments were performed in the conditions of pressure ranging from 1 to 2MPa, mass flow rate ranging from 200 to 1500kg/(m2 ⋅s), inlet subcooling ranging from 20~100°C and tilt angle ranging from 0~ 45°. Three flow patterns, consisting of bubble flow, churn flow and annular flow, were obtained in a wide range of thermal parameters. flow patterns maps were plotted and the influences of pressure, mass flow rate, inlet subcooling, channel gap and tilt angle on the flow pattern transformation of narrow rectangular channel were studied. This study is of great significance for investigating the subsequent heat transfer process of two-phase flow in compact nuclear reactors. © 2022, The Authors. All rights reserved.

关键词： Two phase flow

Research on Artificial Neural Network for Geometric Design and Optimization of Three-Stage Segmented Thermoelectric Generators

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SSRN 2024年

作者： Zhang, Yin Guo, Kailun Wang, Chenglong Zhang, Jing Wang, Yulu Tian, Wenxi Su, Guanghui Qiu, Suizheng School of Nuclear Science and Technology Shanxi Key Laboratory of Advanced Nuclear Energy and Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi’an710049 China School of Mechatronic Engineering Xianyang Vocational Technical College Xi’an712000 China

More green and environmentally friendly electricity production is the driving force for the development of thermoelectric generators. In addition to high-performance thermoelectric materials, optimizing the geometric shape of thermoelectric generators can also maximize thermoelectric efficiency. This work applies artificial neural networks to the design and optimization of a three-stage segmented thermoelectric generator. After verifying the thermoelectric numerical model of COMSOL, this work generated 3000 sets of simulation data for neural network training. After hyperparameter and particle swarm optimization, the trained neural network can exhibit extremely high prediction accuracy. By coupling the genetic algorithm and artificial fish swarm algorithm, the trained artificial neural network can optimize eight geometric parameters of a three-stage segmented thermoelectric generator under different temperature differences. Compared with COMSOL optimization results, the conversion efficiency optimized by GA has increased by 1.42% and 2.48% in cases 1 and 2, respectively;The conversion efficiency optimized by AFSA has increased by 3.61% and 2.86% in cases 1 and 2, respectively. By obtaining almost identical optimization values, the neural network can achieve geometric design optimization within 5 minutes under different temperature differences. This method provides a new and economical avenue for rapid prediction and design of thermoelectric generators. © 2024, The Authors. All rights reserved.

关键词： Genetic algorithms

Thermionic Conversion Performance Analysis of the Single-Cell Thermionic Fuel Element Based on Froba-Thermion Code

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SSRN 2022年

作者： Lu, Kailin Yao, Hao He, Yanan Wu, Yingwei Zhang, Jing Liao, Haoyu Su, Guanghui H. Qiu, Suizheng School of Nuclear Science and Technology Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610041 China

The thermionic conversion performance of the single-cell thermionic fuel element (TFE) is influenced by fuel mass transfer and other parameters. With the consideration of current flow and heat transfer, the thermionic conversion model and the modified heat transfer model were implemented in FROBA-THERMION. Afterward, both implemented models were verified by comparing with experiments or KATET calculation results. Further, a steady-state performance simulation of the single-cell TFE was carried out. The results indicate that the thermionic conversion efficiency will be decreased due to the emitter temperature flattening caused by fuel mass transfer. In addition, the influence of several key parameters on thermionic conversion efficiency and measures to improve the thermionic conversion efficiency were analyzed. © 2022, The Authors. All rights reserved.

关键词： Mass transfer

Enhanced photodynamic therapy of mixed phase TiO2（B）/anatase nanofibers for killing of HeLa cells

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Nano Research 2014年第11期7卷 1659-1669页

作者： Shuchao Zhang Dongjiang Yang Dengwei Jing Hongwei Liu Long Liu Yi Jia Meihua Gao Liejin Guo Ziyang Huo Department of Blood Transfusion the Affifiated Hospital of Medical College Qingdao University Oingdao 266003 China Department of Immunology Medical College of Qingdao University Qingdao266000 China Collaborative Innovation Centre for Marine Biomass Fibers Materials and Textiles of Shandong Province College of Chemical and Environmental Engineering Qingdao University Qingdao China Queensland Micro- and Nanotechnology Centre (QMNC) Griffith University Nathan Brisbane QLD 4111 Australia International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering College of Chemistry Chemical and Environmental Engineering Xi'an Jiaotong University Xi'an 710049 China Australian Centre for Microscopy and Microanalysis (ACMM) the University of Sydney Sydney NSW 2006 Australia

Photodynamic therapy （PDT）, which is a procedure that uses photosensitizing drug to apply therapy selectively to target sites, has been proven to be a safe treatment for cancers and conditions that may develop into cancers. Nano-sized TiO2 has been regarded as potential photosensitizer for UV light driven PDT. In this study, four types of TiO2 nanofibers were prepared from proton tri-titanate （H2T3O7） nanofiber. The as-obtained nanofibers were demonstrated as efficient photosensitizers for PDT killing of HeLa cells. MTT assay and flow cytometry （FCM） were carried out to evaluate the biocompatibility, percentage of apoptotic cells, and cell viability. The non-cytotoxicity of the as-prepared TiO2 nanofibers in the absence of UV irradiation has also been demonstrated. Under UV light irradiation, the TiO2 nanofibers, particularly the mixed phase nanofibers, displayed much higher cell-killing efficiency than Pirarubicin （THP）, which is a common drug to induce the apoptosis of HeLa cells. We ascribe the high cell- killing efficiency of the mixed phase nanofibers to the bandgap edge match and stable interface between TiO2（B） and anatase phases in a single nanofiber, which can inhibit the recombination of the photogenerated electrons and holes. This promotes the charge separation and transfer processes and can produce more reactive oxygen species （ROS） that are responsible for the killing of HeLa cells.

关键词： photodynamic therapy titanium oxides （TiO2） nanomaterials apoptosis mixed phase

Application of high resolution finite difference scheme in direct numerical simulation of turbulent flow

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2007年第5期28卷 859-861页

作者： Ma, Liang-Dong Li, Zeng-Yao Tao, Wen-Quan State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an 710049 China

A direct numerical simulation of a fully developed turbulent flow and heat transfer in a square duct is studied based on high resolution finite difference scheme. The flow and temperature fields are obtained at a turbulent Reynolds number of 400 based on the mean friction velocity and the hydraulic diameter, and the Prandtl number (Pr) of 0.71. Two kinds of point-stencil method are used for the spatial derivatives of the pressure Poisson equation, i.e. the second-order and fourth-order central difference, respectively. The results show that satisfactory solutions can be obtained in the present DNS simulation with coarse grids compared with the method of second-order central difference. And the solutions from the two kinds of point-stencil method for pressure Poisson equation are consistent with the second-order central difference being more economical in saving computation time.

关键词： Pipe flow

The Enriched-Embedded Discrete Fracture Model (Nedfm) for Fluid flow in Fractured Porous Media

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SSRN 2023年

作者： Jiao, Kaituo Han, Dongxu Chen, Yujie Bai, Bofeng Yu, Bo State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi’an710049 China School of Mechanical Engineering Beijing Key Laboratory of Pipeline Critical Technology and Equipment for Deepwater Oil & Gas Development Beijing Institute of Petrochemical Technology Beijing102617 China

The embedded discrete fracture model (EDFM) is widely adopted for fluid flow in fractured porous media, but it cannot be employed for blocking fractures due to the assumption of symmetric and linear pressure distribution around fractures. To improve it, this work presents a novel numerical framework named the enriched-embedded discrete fracture model (nEDFM). It is based on the non-conforming grid and discretized by the mass-conservative finite volume method. Attractively, the nEDFM applies to both conductive and blocking fractures, as well as isotropic and anisotropic matrix permeability, while maintaining a low computational cost. The local shape function, which introduces two enriched degrees of freedom for every fracture cell, is developed to model the discontinuities of pressure and its gradient on two sides of the fracture. Correspondingly, two equations for coupling the matrix and reduced fracture are supplemented to close the system and improve the accuracy of mass exchange between the matrix and fracture. The performance of nEDFM is compared with the classical EDFM and projection-based EDFM (pEDFM). The results show that the nEDFM outperforms the EDFM for conductive fractures and can obtain better pressure distribution inside blocking fractures than the pEDFM. For anisotropic matrix permeability with conductive or blocking fractures, the nEDFM can get solutions comparable to those obtained by the reference solution. Hence, the nEDFM is an accurate and flexible method for fluid flow simulation in fractured porous media. © 2023, The Authors. All rights reserved.

关键词： Fracture

The uniformity improvement of temperature distribution in the cryogenic target by means of auxiliary heating belts

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The uniformity improvement of temperature distribution in th...

The 5thInternational Conference on Cryogenics and Refrigeration ICCR 2013(第五届国际低温制冷会议)

作者： Zhao J. Li Y.Z. Yu J.L. Zheng J. Department of Refrigeration and Cryogenic Engineering Xi''an Jiaotong UniversityXi''an710049China Department of Refrigeration and Cryogenic EngineeringXi''an Jiaotong UniversityXi''an710049China State Key Laboratory of Multiphase Flow in Power Engineering Xi''an710049China

Numerical Simulation Study on Two-Phase flow of Thermal Runaway Evolution and Jet Fire of 18650 Lithium-Ion Battery Under Thermal Abuse

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SSRN 2023年

作者： Wang, Jia-Hao Mei, Mei Jiang, Ziqi Qiu, Huihe Wang, Ying Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Department of Mechanical and Aerospace Engineering The Hong Kong University of Science and Technology Clear Water Bay Hong Kong

This study investigates the impact of particles on the external jet flame of 18650 lithium-ion batteries using a two-dimensional transient numerical simulation. The mixing characteristics of jet flames and particles generated by battery combustion are analyzed using a multi-component Navier-Stokes equation and Lagrangian method. The model is validated by comparing it with experimental measurements of flame height. The results show that particles have a significant impact on the jet flame's characteristics and dynamic behavior during the battery's thermal runaway process. The study includes an analysis of the velocity field, temperature field, flow field, component concentration distribution, and lift-off height. Two stages of the jet flame are identified: unstable and stable. The presence of particles causes the unstable flame height to be 1-2 times higher than the stable flame height. This research provides reference for the safety assessment of actual batteries. © 2023, The Authors. All rights reserved.

关键词： Lithium-ion batteries

An Experimental Study on the Hypergolic Process Enhanced by Pre-Ignition Heat Release: [Amim][Dca]/Furfuryl Alcohol Blends Reacting with White Fuming Nitric Acid

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SSRN 2022年

作者： Wu, Yingtao Wang, Zhi Fei, Lihan Guo, Yang Liu, Yang Tang, Chenglong Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Research Center of Energetic Material Genome Science Institute of Chemical Materials China Academy of Engineering Physics Mianyang China

The hypergolic ignition behaviors of [AMIM][DCA] (1-allyl-3-methylimidazolium dicyanamide)/furfuryl alcohol (FA) blends reacting with white fuming nitric acid (WFNA) are investigated using drop test approach. Morphology results from two high speed cameras and temperature profiles from an infrared camera are combined in analyzing the hypergolic process. A typical hypergolic process observed in this work involves a mixing dominant stage, a stage with moderate temperature rising and vapor/secondary droplets emerging, and a stage with violent temperature rising accompanied by flame occurrence. Two kinds of delay times are used to characterize the hypergolic process which are found to be nonmonotonic with the variations of FA fractions. FA, though not hypergolic with WFNA, exhibits extensive pre-ignition heat release due to its physical and chemical properties, which enhances the hypergolic process of [AMIM][DCA]/FA blends with WFNA. © 2022, The Authors. All rights reserved.

关键词： Ionic liquids