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Experimental study on flow characteristics of rectangular narrow channel

International Journal of Advanced Nuclear Reactor Design and Technology 2020年 2卷 60-68页

作者： Song, Gongle Sun, Rulei Zhang, Dalin Su, G.H. Tian, Wenxi 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

Plate fuel elements is gradually used in advanced reactor structure design because of its advantages of high fuel consumption and high safety. The flow channel of the plate fuel element is a typical rectangular narrow channel, and accurately obtaining the flow characteristics of the rectangular narrow channel has become the most basic problem in the thermal and hydraulic research of the rectangular narrow channel. The flow characteristics of a rectangular narrow channel with cross-section of 3 × 67 mm and length of 745 mm are studied experimentally. The mass flow range is 50–650 kg/h, the pressure is 0.1–1 MPa, and the range of the inlet temperature is 283.15–333.15 K. The Reynolds number obtained experimentally in the laminar-turbulent transition region is in the range of 2700–4000, which has a significant delay compared to round channels. Laminar flow is modeled theoretically, and the Fourier sine transform method is used to solve the momentum Navier-Stocks equation, and the expression of the friction coefficient is obtained through the velocity distribution. However, due to the particularity of the test section, the error of the theoretical solution is large compared with experimental data. Five empirical correlations commonly used in rectangular narrow channels are evaluated. The Leon correlation is applicable to the experimental laminar flow area, and the Blasius correlation is applicable to the turbulent flow area. In order to further reduce the error, the friction correlation applicable to this experimental condition is fitted, making the prediction of friction coefficient more accurate. For subsequent experimental research on heat transfer, flow pattern, CHF, flow instability, etc., these works are of great significance. © 2020 Xi'an Jiaotong University

关键词： Laminar flow

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Multi-Objective Optimization and Configurations Comparison of Closed-Air Brayton Cycle

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SSRN 2023年

作者： Qian, Yiran Gu, Zhenzhen Song, Meihui Yang, Yi Zhao, Quanbin Chen, Weixiong Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China China Institute of Atomic Energy P.O. Box 275-32 Beijing102413 China

Microreactor power system has characteristics of efficient, compact and high environmental adaptability. In this study, closed-air Brayton cycle (CABC) is proposed as the microreactor thermoelectric conversion system, and thermodynamic model of CABC with different configurations are established. The cycle parameters and component’s structure are designed using system-component combined design method. To obtained the optimal system design scheme, the Genetic Algorithm (GA) and the Non-dominated Sorting Genetic Algorithm II (NSGA-II) are separately applied for single-objective optimization and multi-objective optimization. According to multi-objective optimization results, the IRRC has the highest cycle efficiency of 35.4% and the ratio of power to mass of 59.1 kW·t-1 , respectively, and the RRC has the highest power density of 179.6 kW·m-3 . Similar performance with IRRC and simpler structure make the RRC the optimal configuration of CABC. Compared with single-objective optimization, the design results of multi-objective optimization are more balanced in terms of three performance indicators, meaning that the optimized design scheme has a better comprehensive performance. © 2023, The Authors. All rights reserved.

关键词： Multiobjective optimization

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Numerical simulation on filling process of drag reduction agent in natural gas pipeline 5

Numerical simulation on filling process of drag reduction ag...

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2021 5th International Conference on Fluid Mechanics and Industrial Applications, FMIA 2021

作者： Yin, Xiaoyun Jing, Jiaqiang Jing, Peiyu Sun, Jie Yuan, Ying School of Oil and Natural Gas Engineering Southwest Petroleum University Chengdu China Oil and Gas Fire Protection Key Laboratory of Sichuan Province Chengdu China State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an China

In this paper, a numerical simulation is established to model the filling process of atomized natural gas drag reduction agent (DRA) at the pipeline inlet section. The computations are on the basis of the Euler-Lagrange method with the standard k-ϵ turbulence model. The effects of atomizing parameters on the droplets Sauter Mean Diameter (SMD) and the adsorption performance on the wall of pipe are investigated using the validated model. The results show that nozzle diameter and nozzle angle have little effect on the SMD of DRA droplets, whereas the size of the droplets SMD reduces with the increase of atomizing pressure, and the influence of atomizing flow rate is just the opposite. © Published under licence by IOP Publishing Ltd.

关键词： Drops

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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

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Dynamic simulation of coal-fired power plant integrated with trough solar collector operating in parallel with high pressure heaters

Dynamic simulation of coal-fired power plant integrated with...

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2019 Canadian Society for Civil engineering Annual Conference, CSCE 2019

作者： Yan, Hui Li, Xin Liu, Ming Chong, Daotong Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China

ISBN: (纸本)9780791883747

Solar-aided coal-fired power plant (SACFPP) is a costeffective approach to overcome solar energy intermittency. SACFPPs frequently operate in dynamic processes due to power load and solar energy fluctuations. This study investigated the dynamic characteristics of SACFPPs;such characteristics are important for flexibility evaluation and control system design. The SACFPP used in this study was based on a 660 MW coalfired power plant, and a trough collector system (TCS) operates in parallel with high pressure (HP) heaters. After model development and validation, the dynamic performance of the SACFPP was analyzed under four load ratios of power plant, with disturbances of two parameters: direct normal irradiance (DNI) and mass flowrate ratio to TCS. The performance was also compared with three parallel TCS connection modes. Results showed that the magnitude and response time for power variation under DNI disturbance increased with load ratio. With 500 W/m2 DNI step increments, power increased by approximately 18.4, 21.2, 24.7, and 29.8 MW in 2200, 2330, 2550 and 2620 s at 70%, 80%, 90%, and 100% load ratios, respectively, when all the HP heaters were replaced. The serial number and the number of HP heaters replaced also increased the power variation and response time. Under mass flowrate ratio to TCS increase disturbance, the power rapidly changed to its maximum and then slowly decreased, but the variation value depended on the load ratio. Copyright © 2020 ASME.

关键词： Coal fired power plant

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Characteristics of Bubble Dynamic Behavior on the Surface of Photoelectrode Under the Influence of a Vertical Magnetic Field

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SSRN 2023年

作者： Feng, Yuyang Wang, Yechun Zhang, Bo Cao, Zhenshan Liu, Miaomiao Zhen, Canghao Guo, Liejin State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Xinjin Weihua Institute of Clean Energy Research Nanhai District Guangdong Province Foshan City China

The magnetohydrodynamic (MHD) flow around the bubble induced by the Lorentz force owing to the applied magnetic field significantly affects the behavioral characteristics of the bubble on the electrode surface. However, the mechanism of the impact of a magnetic field perpendicular to the electrode on the dynamic behavior of bubbles remains unclear. In this study, the evolution law of a single oxygen bubble on the surface of a TiO2 photoelectrode under the influence of a vertical magnetic field with different magnetic induction intensities was investigated. The vertical magnetic field effectively promoted the rapid detachment of bubbles from the electrode surface, and greatly improved the gas evolution efficiency. The mass transfer was dominated by single-phase free convection during bubble evolution. Under the influence of the vertical magnetic field, the mass transfer coefficient near the electrode was enhanced, and the adverse effects of bubbles on mass transfer were counteracted when they entered the reaction-controlled growth phase. The further multiphysics simulation found that the MHD convection decreased the local supersaturation of reaction product oxygen molecules near the electrode, thereby reducing concentration overpotential and increasing the reaction rate. This study provides an experimental and theoretical basis for promoting the bubble detachment and the reaction rate on the gas evolving electrode surface during photoelectrochemical water splitting. © 2023, The Authors. All rights reserved.

关键词： Efficiency

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Transient Analysis of Cryogenic Cooling Performance for High-power Semiconductor Lasers Using Flash-Evaporation Spray

SSRN

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SSRN 2022年

作者： Tian, Jiameng Li, Bufa Wang, Junfeng Chen, Bin Zhou, Zhifu Wang, Hai School of Energy and Power Engineering Jiangsu University Zhenjiang212013 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China

Focusing on the cryogenic cooling for the high-power semiconductor lasers to improve their output performance, this work conducted an experimental investigation on analyzing the transient cooling performance using a pulsed two-phase flash-evaporation spray with the environmental cryogen R32. A heat flux estimation methodology that considers an imposed heat flux as a boundary condition, was first developed to assist the transient heat transfer analysis. The results provided further insight into phase-change heat transfer on the hot surface from high-temperature to cryogenic regimes through coupling the heat transfer measurements with observations of hydrodynamic liquid film formation and development. The moderate spurt duration (Δ t = 30 s) that produced a large temperature drop (109.5 °C) and high time-averaged cooling rate (24.1 W/cm2) was preferable. The significant losses in droplets’ momentum and mass contributed to the fast decrease in cooling effect as spray distance (Z) increased. Specifically, shortening Z from 50 to 10 mm not only increased the maximum surface heat flux from 19.6 to 73.6 W/cm2, but also broadened the temperature region with high heat flux. The nozzle with a smaller orifice diameter (0.5 mm) produced a lower cooling rate. Whereas surprisingly, its lower flow rate resulted in the lesser coolant accumulation and splashing on the hot surface, which elevated its thermal efficiency. Spurt duration that can produce a specific temperature drop almost remained unchanged or slightly raised as the input heating power increased, implying that the fluid supply is excess and the liquid flow rate could be reduced to save liquids. © 2022, The Authors. All rights reserved.

关键词： Heat flux

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Simulation Study on Heat Exchangers Characteristics of Solar Thermal Steam System Based on Aspen Plus

Simulation Study on Heat Exchangers Characteristics of Solar...

引用

Algorithms, High Performance Computing and Artificial Intelligence (AHPCAI), International Conference on

作者： Pengfei Chen Kang Chen Huaiwu Peng Yanlong Zhang Baercheng Bawaa Qiuyang Zhao Institute of Solar Engineering Technology Northwest Engineering Corporation Limited Power China Xi'an China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China

In the thermal recovery project of thick oil, there are high standards for steam temperature and flow rate. The solar thermal steam supply system can convert unstable solar energy into stable and efficient carrier heat, which can be used to transfer heat to low-temperature water to produce high-temperature steam and achieve a clean and low-carbon steam supply. The rated pressure of steam and the split ratio of molten salt in the heating system have a great influence on the demand area and heat load of solar panels. In this paper, a simulation is made on the solar thermal steam supply system based on Aspen Plus. The simulation result shows that the increase in pressure will cause a growth in the area of the photothermal concentrator field but will reduce the area used for photovoltaic panels. At the same time, it reduces the heat load of the evaporator and extends its service life. The split ratio affects the molten salt temperature at the outlet of the superheater and the reheater. When the split ratio increases, the heat transfer temperature difference between the two ends of the superheater heat flow decreases, and the heat transfer temperature difference of the reheater grows bigger. Therefore, the molten salt temperature flowing out of the reheater rises.

关键词： Water Temperature Costs Oils Simulation Water heating Solar heating

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Analysis on the Thermal Behaviour of the Latent Heat Storage System Using S-Co2 and H-Pcm

SSRN

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SSRN 2022年

作者： Nan, Wenguang Ming, Zhu Wang, Yueshe School of Mechanical and Power Engineering Nanjing Tech University Nanjing211816 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

Energy storage and utilization of CO2 have attracted increasing attention due to international zero carbon plan. Here, the latent heat storage system using high-temperature phase change material (H-PCM) and supercritical CO2 (S-CO2) is analysed by using CFD simulation, in which the tube containing S-CO2 is submerged in a tank containing the salt with high melting temperature. A new and combined phase transition model is developed to describe the dynamics of PCM in different phase state, and it is validated against experimental data in literature. The dynamics of natural convection is focused, and its effects on the heat storage system are analysed, including maximum natural convection velocity, phase interface, and melting pattern. The results show that natural convection has a great influence on the melting process of the H-PCM in the charging process. The melting pattern of H-PCM could be contrary between the cases with and without considering natural convection. During the discharging process, natural convection has little effect on the heat transfer of energy release due to its short duration. With the increase of ratio between the S-CO2 tube and H-PCM tank, the strength of the natural convection of melting H-PCM is enhanced, especially the duration of natural convection. © 2022, The Authors. All rights reserved.

关键词： Natural convection

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Prediction of Pressure Drop in Heavy Oil-Water Ring Two-Phase flow Based on Modified Two-Fluid Model

SSRN

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SSRN 2024年

作者： Fu, Jiqiang Du, Mingjun Jing, Jiaqiang Sun, Jie Liu, Huichao Chen, Yongjiu State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China China Petroleum Engineering & Construction Corp North Company Heibei Renqiu062552 China School of Oil & Natural Gas Engineering Southwest Petroleum University Sichuan Chengdu610500 China

Accurate prediction of pressure drop of the heavy oil-water ring flow in pipeline is of great significance for establishing an optimal drag reduction model and ensuring safe production. The effects of different factors on the flow pattern and pressure drop of heavy oil-water annular two-phase flow were systematically analyzed, and a standard two-fluid pressure drop prediction model for annular flow was established. By modifying the shear stress equation of oil-water interface and introducing the wave-flow theory to modify the shear stress equation of water wall, a pressure drop prediction model for the generalized concentric water ring was obtained to calculate the periodic fluctuations of oil phase. Furthermore, by introducing the comprehensive Reynolds number expression of eccentric water ring, the pressure drop prediction model for the generalized eccentric water ring was obtained to calculate the periodic fluctuations of oil phase. The results show that the pressure drop prediction accuracy of the concentric water ring for ultra-heavy oil is improved by 80 % by using the modified pressure drop prediction model. The comprehensive Reynolds number expression of eccentric water ring can effectively reflect the influence of eccentric effect on shear stress of water wall and the calculation error is less than 20 % by predicting the pressure drop of the generalized eccentric water ring with different density differences. © 2024, The Authors. All rights reserved.

关键词： Two phase flow

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