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Numerical investigation of heat transfer characteristics between two particles and supercritical water

JOURNAL OF SUPERCRITICAL FLUIDS 2021年 177卷 105327-105327页

作者： Li, Xiaoyu Wu, Zhenqun Wang, Huibo Jin, Hui Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

This work takes two particles as an example to study the effect of distance and angle between two particles on the average Nusselt number Nu, average heat transfer rate lb, local Nusselt number Nu phi, and local heat transfer rate la phi. It was found that the variation trend of Nu and Nu phi in supercritical water is the same as that in constant property flow, thus indicating that the variation trend of heat transfer between particles and fluid in supercritical water is the same as in constant property flow. The change in physical properties of supercritical water does not have any special effect on the variation trend of heat transfer. The heat transfer is mainly affected by the overlap of temperature field and the overlap of flow field. However, the results of lb and la phi indicate that the variation trend of heat transfer rate is affected by temperature gradient changes and physical property changes.

关键词： Supercritical water Two particles Heat transfer rate Changes in physical properties

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Hydrogen purification using nanoporous graphene membranes and its economic analysis

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CHEMICAL engineering SCIENCE 2019年 208卷 115141-000页

作者： Sun, Chengzhen Zheng, Xiuzhi Bai, Bofeng Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian Shaanxi Peoples R China

We show from molecular dynamics insights that the nanoporous graphene (NPG) is an efficient membrane in hydrogen purification for separating gaseous H-2/CH4 mixtures with a high permeance and selectivity. The H-2 permeance is as high as 106 GPU, extremely higher than those of polymer membranes;the selectivity of H-2 over CH4 is up to 225, in the same order with those of polymer membranes. An economic analysis is performed from the aspects of compression energy consumption and required membrane area;it is shown that the NPG membrane requires less membrane area but a bit more compression energy compared with the polymer membranes. However, the slightly higher compression energy consumption can be totally offset by the remarkably smaller membrane area. In summary, the NPG membranes for hydrogen purification present an excellent separation performance with a high H-2 permeance, ultimately resulting in an impressive economic index comparing to the polymer membranes. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Separation membrane Nanoporous graphene Hydrogen purification Economic analysis Molecular dynamics

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Investigation on Effect of Gravity Level on Bubble Distribution and Liquid Turbulence Modification for Horizontal Channel Bubbly flow

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MICROGRAVITY SCIENCE AND TECHNOLOGY 2017年第4期29卷 313-324页

作者： Pang, M. J. Wei, J. J. Yu, B. Changzhou Univ Sch Mech Engn Changzhou 213164 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China Beijing Inst Petrochem Technol Sch Mech Engn Beijing 102617 Peoples R China

Bubbly flows in the horizontal channel or pipe are often seen in industrial engineering fields, so it is very necessary to fully understand hydrodynamics of horizontal bubbly flows so as to improve industrial efficiency and to design an efficient bubbly system. In this paper, in order to fully understand mechanisms of phase distribution and liquid-phase turbulence modulation in the horizontal channel bubbly flow, the influence of gravity level on both of them were investigated in detail with the developed Euler-Lagrange two-way coupling method. For the present investigation, the buoyance on bubbles in both sides of the channel always points to the corresponding wall in order to study the liquid-phase turbulence modulation by bubbles under the symmetric physical condition. The present investigation shows that the gravity level has the important influence on the wall-normal distribution of bubbles and the liquid-phase turbulence modulation;the higher the gravity level is, the more bubbles can overcome the wall-normal resistance to accumulate near the wall, and the more obvious the liquid-phase turbulence modulation is. It is also discovered that interphase forces on the bubbles are various along the wall-normal direction, which leads to the fact that the bubble located in different wall-normal places has a different wall-normal velocity.

关键词： Microbubbles Phase distribution Turbulence modulation Gravity level DNS

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A review of molecular tagging measurement technique

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MEASUREMENT 2021年 171卷 108790-108790页

作者： Li, Fangbo Zhang, Haibin Bai, Bofeng Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Molecular tagging measurement technique is an advanced non-intrusive visualization approach which uses the molecules as the tagging and tracking materials. This technique has advantages in the measurement of complex flow fields such as the boundary layer flow, supersonic turbulence, micro-scale flow and combustion flow, and it owns superiorities in the simultaneous measurement of multi-parameters in the flow field such as velocity field, temperature field and pressure field. In this paper, a comprehensive review on recent advances of molecular tagging measurement is presented, with an emphasis on its measurement fundamentals and approaches. In addition, the factors influencing the resolution and uncertainty of this technique are also discussed. Finally, the applications highlighting the advantages of this technique are shown. This review provides the current situation as well as challenges of this measurement technique, and is expected to promote the extensive applications of molecular tagging measurement technique in both scientific research and industry.

关键词： Molecular tagging measurement Non-intrusive visualization approach Complex flow measurement Measurement fundamentals Measurement applications

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Signal selection for identification of multiphase flow patterns in offshore pipeline-riser system

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OCEAN engineering 2023年第1期268卷

作者： Xu, Qiang Yuan, Xintong Liu, Chenying Wang, Xinyu Guo, Liejin Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

multiphase flow pattern identification is an urgently desirable approach for flow assurance of gas-liquid trans- portation in deep-sea pipelines. Experiments are performed on a system with 1657 m horizontal pipe and 16.7 m S-shaped riser. A new method of sample preparation using only data from liquid accumulation stage is proposed for identification of early-stage severe slugging. A set of signal evaluation and selection criteria covering the recognition effect and practicability of signals are proposed for identification of severe slugging, oscillating flow and stable flow. For oilfield applications including above-water and underwater scenarios, pressure signals at different locations of the pipeline-riser system are selected to meet the actual demand with the shortest sampling duration. Using the combination of above-water signals at the top of the riser, the recognition rate of 90.0% is achieved at a sampling duration of 37.2 s. Feature dimension is reduced by principal component analysis, and good recognition results are obtained using the optimal signal combinations in different classifiers.

关键词： Air-water flow Severe slugging Pipeline-riser system Pattern identification Signal selection

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Review: Steam cavity characteristics of steam submerged jet condensation at SC regime

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PROGRESS IN NUCLEAR ENERGY 2020年 130卷 103560-103560页

作者： Zhao, Quanbin Chong, Daotong Chen, Weixiong Li, Gen Yan, Junjie Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Steam submerged jet condensation has been widely used in nuclear fission and fusion industries, chemical engineering and aerospace industry. Steam cavity and its feature in stable condensation regime play important roles since they are closely related to heat transfer and condensation oscillation. Due to the different definitions of steam cavity, the properties of steam cavity, such as shapes, void fraction distribution and two-phase mixing regions, are different. The mechanism of steam cavity forming and development remains unclear. The existing analytical models and empirical correlations for steam jet length are verified with experimental data. Most correlations based on Kerney's model can predict the experimental jet lengths when water is stagnant and steam mass flux lower than 800 kg m-2.s-1. For other conditions, significant discrepancy is found among existing experimental jet lengths, and no model can predict them well. The heat transfer coefficient calculation models based on steam jet length correlations fail to predict the experimental data, and no unified correlations or models can predict heat transfer coefficient well. The causes of prediction deviation for jet length and heat transfer coefficient are analyzed. The inconsistent tendency and nonunified saturated temperature cause the significant predicted deviation. Further efforts on analytical and experimental studies on steam jet length and heat transfer coefficient are encouraged in the future.

关键词： Direct contact condensation Steam jet condensation Steam cavity Steam jet length Heat transfer

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Numerical simulation on the hydrodynamic performance of high-pressure evaporator in once-through heat recovery steam generators

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APPLIED THERMAL engineering 2022年 217卷

作者： Nie, Chao Zhang, Xirong Li, Weiteng Chen, Jingrong Chen, Tingyu Yang, Dong Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

The once-through heat recovery steam generator (HRSG) of gas-turbine combined-cycle power plants adopts a triple-pressure reheat evaporator arrangement. To study the overall performance of the evaporator during operation, it's divided into three sections: EVA1, EVA2, and EVA3 along the working fluid flow. In this study, in accordance with the heating load distribution characteristics of the evaporator and in consideration of the system mass, momentum, and energy conservation equations, the nonlinear mass and pressure drop balance equations are directly solved. The flow distribution, pressure drop distribution, profiles of working fluid temperature and outlet steam temperature of evaporator at boiler maximum continuous rating (BMCR), 75 % BMCR, and 30 % BMCR loads are analyzed. The flow distribution of evaporator at each load shows a positive response characteristic. The flow distribution at all levels is relatively reasonable, and there will be no heavy difference in the temperature and steam quality of fluid, which will lead to pulsation. Simulation results demonstrate that the metal properties can meet the requirements of material strength at each working condition, and the evaporator will not experience flow instability, stagnation, and pulsation at low loads. The triple-pressure once-through reheat HRSG can operate safely and reliably and has the advantage of lifting and lowering the load rapidly.

关键词： Heat recovery steam generator Once-through triple-pressure reheat evaporator Hydrodynamic simulation Safety check flow instability

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A three-dimensional numerical analysis of platelet flow in a carotid artery

A three-dimensional numerical analysis of platelet flow in a...

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7th International Conference on Fluid Mechanics(ICFM7)

作者： Guojie Li Bin Chen State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

Human carotid artery is bifurcated into two arteries in the neck,supplying blood to the brain and facial *** plaque tends to occur and develop in carotid artery sinus,where stenoses and other lesions can cause cerebral *** is accepted that the chronic exposure of the endothelial cells to lower wall shear stress(WSS)is associated with thickening of the vessel wall and development of atherosclerotic ***,platelet in blood is also accepted to play es-

关键词： profile A three-dimensional numerical analysis of platelet flow in a carotid artery WSS

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A simplified steady-state mesoscale drag model with an analytical solution for fluidized beds

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POWDER TECHNOLOGY 2023年第1期429卷

作者： Meng, Lingyue Zhang, Xujie Shang, Yuqi Zhao, Mingchuan Li, Jiasunle Ge, Zhiwei Guo, Liejin Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Mesoscale structures have an essential impact on hydrodynamics and heat/mass transfer and hence should be considered in drag modeling. However, there is a lack of generalized drag coefficient expressions taking into account mesoscale effects for fluidized beds. In this study, a simplified steady-state mesoscale drag model which can be solved analytically was proposed by simplifying sub-system drag forces and cluster diameter equation. Thus, two new generalized expressions for mesoscale drag coefficient used to simulate fluidized beds were obtained by deriving the analytical solution of the simplified steady-state mesoscale drag model. The sensitivity of the heterogeneity index Hd of the new drag model to material properties and operating gas velocity was analyzed, and the results showed that Hd was most sensitive to dp and Ug, followed by pp and & mu;g, and least sensitive to pg. As a preliminary validation, new drag coefficient expressions were incorporated into two-fluid model simulations of realistic fluidized beds. Noteworthy, the relative errors of axial solid volume fraction using the new Drag A for bubbling, turbulent and circulating fluidized beds, which were 7.41%, 12.51% and 12.80%, respectively, were the smallest compared to that using other drag models. The simulation results proved the accuracy and generality of the new simplified steady-state mesoscale drag model.

关键词： Fluidization Heterogeneous structures Drag coefficient Analytical solution Hydrodynamics Structure-based

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Influence of Stefan flow on the drag coefficient and heat transfer of a spherical particle in a supercritical water cross flow

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PHYSICS OF FLUIDS 2021年第2期33卷 023313-023313页

作者： Jin, Hui Wang, Yingdong Wang, Huibo Wu, Zhenqun Li, Xiaoyu Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

The interaction between the fluid and particles is the key to obtain accurate flow and heat transfer rules. For a reactive particle, the Stefan flow will affect the mass, momentum, and energy transfer between the particle and the fluid. The Stefan flow on the coal particle surface cannot be neglected in supercritical water gasification technology. In this paper, the influence of different Stefan flow intensities on the drag coefficient (Cd) and the Nusselt number (Nu) of supercritical water (SCW) cross flowing around a fixed spherical particle with Re in the range of 10-200 is studied;at the same time, the velocity and temperature boundary layers and the flow field around the particle are analyzed. For the influence of the dramatic change of the thermophysical properties of SCW near the pseudo-critical point, simple analysis of the drag coefficient and heat transfer of the particle with Stefan flow is conducted. The results show that with the increase in Stefan flow intensity, Cd and Nu decrease and the thickness of velocity and temperature boundary layers increases. A model of the particle with Stefan flow is constructed, and the Cd and Nu correlation formulas of the particle with Stefan flow are obtained.

关键词： Drag coefficient

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