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Experimental Study on Heat Transfer Characteristics of Static Flash Evaporation Process

Energy Procedia 2017年 105卷 4776-4781页

作者： Qingzhong Yang Dan Zhang Daotong Chong Yu Wang Junjie Yan State Key Laboratory of Multiphase Flow in Power Engineering School of Energy & Power Engineering Xi’an Jiaotong University Xi’an Shaan

An experimental study on flash evaporation process in static flash evaporation of aqueous NaCl solution was presented. Experiments were carried out with initial concentration of waterfilm varied from 0 to 0.15, initial height from 0.1 to 0.4 m, and superheat from 1.8 to 49.5 K. Instant superheat was the driving force during flash evaporation. A negative correlation was found between temperature drop rate and instant superheat. Instant heat transfer coefficient increased with the increase of instant superheat. A peak value of instant superheat existed during static flash. The evolution of instant superheat was affected by initial superheat, or initial height, or initial concentration of waterfilm.

关键词： Static flash evaporation Instant superheat Aqueous NaCl solution temperature drop rate

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Effect of nozzle diameter on spray and thermal characteristics of R134a flashing spray 13

Effect of nozzle diameter on spray and thermal characteristi...

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13th International Conference on Liquid Atomization and Spray Systems, ICLASS 2015

作者： Zhou, Z.F. Wang, R. Chen, B. Wang, G.X. State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Department of Mechanical Engineering University of Akron AkronOH44325-3903 United States

Two-phase flashing spray holds a special interest in the safety area. High pressure liquids or liquefied gases accidentally released from small hole in chemical or nuclear industry can form two-phase mixtures due to the rapid decrease of pressure, resulting in injuries, fatalities, serious local pollution, etc. Besides, flashing spray has been successfully used in laser dermatology to prevent thermal injuries during recent decade. In this work, an experimental study is conducted to characterize the two-phase flashing spray in the close field of flashing occurrence and quantify the effect of nozzle diameter on the spray and thermal characteristics, using the volatile and low boiling point cryogen of R134a. From the axial and radial distributions of droplet diameter, velocity and average temperature, it is found that droplet diameter and average temperature experience rapid decline along the axial spray distance, and the velocity has acceleration near the nozzle exit due to the explosive atomization. Droplet diameter keeps almost constant except at the spray periphery, and droplet velocity decreases linearly in the radial direction. Droplet average temperature has complex variation along the radial distance depended on the axial distance. Nozzle diameter has significant effect on the spray and thermal characteristics. Larger diameter nozzle results in longer acceleration distance of droplet velocity, whereas smaller diameter nozzle causes higher decrease rate of droplet diameter and temperature near the nozzle exit. Nevertheless, nozzle diameter has little effect on the minimum droplet temperate with the same value of -60oC. The dimensional analysis indicates that the non-dimensional lateral velocity profile and the non-dimensional droplet average temperature in the spray centerline all show self-similarity. New correlations of non-dimensional droplet velocity and average temperature are proposed. © 2015 International Conference on Liquid Atomization and Spray Systems

关键词： Velocity

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Thermoelectric characteristics analysis of TOPAZ-II

Thermoelectric characteristics analysis of TOPAZ-II

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2019 Transactions of the American Nuclear Society, ANS 2019

作者： Dai, Zhiwen Wang, Chenglong Liu, Xiao Zhang, Dalin Qiu, Suizheng Su, Guanghui School of Nuclear Science and Technology Shanxi Engineering Research Center of Advanced Nuclear Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

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FLUENT-based computation for a time-space-dependent neutron kinetics model

FLUENT-based computation for a time-space-dependent neutron ...

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2015 ANS Annual Meeting

作者： Zhang, Dalin Ge, Jian Tian, Wenxi Qiu, Suizheng School of Nuclear Science and Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University No.28 Xianning West Road Xi'an710049 China

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Spatio-Temporal flow Field Prediction of Turbulent Boundary Layer Based on PINN

Spatio-Temporal Flow Field Prediction of Turbulent Boundary ...

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Vortex Workshop on New Progress in Vortex Identification and Applications, VW 2023

作者： Zhu, Jiahao Song, Yang Dong, Xiangrui School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer for Power Engineering Shanghai200093 China

ISBN: (纸本)9789819786077

Based on the PINN neural network for the study of turbulence, it can solve the nonlinear equations without grid, which is different from the CFD method. This paper mainly uses the PINN method to study the temporal and spatial prediction of the turbulent boundary layer flow field, and in the absence of label values, based on the known flow field information, the unknown information is reasonably predicted by solving the N-S equation. The comparison of PINN prediction results with numerical simulation and experimental results verifies the feasibility of applying PINN to the study of turbulent boundary layer. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.

关键词： Computational fluid dynamics

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Optimization of Heliostat Fields Using Advanced Particle Swarm Optimization (APSO) 4

Optimization of Heliostat Fields Using Advanced Particle Swa...

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4th IEEE International Conference on Renewable Energy and power engineering, REPE 2021

作者： Rizvi, Arslan A. Yang, Dong Khan, Talha Ali Xi'An Jiaotong University State Key Laboratory of Multiphase Flow in Power Engineering Xi'an710049 China University of Europe for Applied Sciences Department of Data Science Potsdam Germany

ISBN: (纸本)9781665443715

Optical losses account for 40% of all the losses in a central receiver system. These optical losses occur due to factors like shading, blocking, atmospheric attenuation, spillage, cosine loss, and mirror reflectivity. These factors are collectively represented using a single factor known as optical efficiency. There exists a tradeoff among these factors. The unavoidable optical loss can be minimized by optimizing the positions of heliostats in a strategic manner. An advanced particle swarm algorithm is used to optimize the position of heliostats around a dense radial staggered field. An efficiency map of the heliostat field is generated. Using instantaneous optical efficiency as an objective function, a single objective optimization is performed using 30 particles and 2 dimensions (each dimension representing an optimization variable). The results highlight the areas in the heliostat field with the highest losses associated with different components of optical efficiency and their solution. The instantaneous efficiency increases by 1.5% after optimization. © 2021 IEEE.

关键词： Particle swarm optimization (PSO)

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Measurement of the instantaneous detailed flame front structure of syngas turbulent premixed flames at high pressure

Measurement of the instantaneous detailed flame front struct...

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9th Asia-Pacific Conference on Combustion, ASPACC 2013

作者： Wang, Jinhua Zhang, Meng Huang, Zuohua Kudo, Taku Kobayashi, Hideaki State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Institute of Fluid Science Tohoku University Sendai Miyagi 9808577 Japan

Instantaneous detailed flame front structure of syngas turbulent premixed flames was investigated and compared to that of CH4/air flames. Results show that the flame front of turbulent premixed flames at high pressure is a wrinkled flame front with small scale convex and concave structures superimposed with large scale flame branches. The convex structures are much more frequent than the concave ones on flame front which reflects a general characteristic of the turbulent premixed flames at high pressure. The syngas flames possess much wrinkled flame front with much smaller fine cusps structure compared to that of CH4/air flames and the main difference is on the convex structure. The effect of turbulence on the general wrinkled scale of flame front is much weaker than that of the smallest wrinkled scale. The general wrinkled scale is mainly dominated by the turbulence vortex scale, while, the smallest wrinkled scale is determined by the flame intrinsic instability. The effect of flame intrinsic instability on flame front of turbulent premixed flame is mainly on the formation of a large number of convex cusps structure propagating to the unburned reactants and enlarge the effective contact surface between flame front and unburned reactants.

关键词： Turbulence

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Low pressure premixed laminar n-heptane+propane/oxygen flames studied with tunable synchrotron photoionization 7

Low pressure premixed laminar n-heptane+propane/oxygen flame...

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7th Asia-Pacific Conference on Combustion, ASPACC 2009

作者： Yu, W. Wei, L.X. Ma, Z.H. Huang, Z.H. Yuan, T. Tian, Z.Y. Li, Y.Y. State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China National Synchrotron Radiation Laboratory University of Science and Technology of China Hefei230029 China

Low pressure premixed laminar n-heptane/propane/O2/N2 flames were investigated with tunable synchrotron vacuum ultraviolet (VUV) photoionization and molecular-beam sampling mass spectrometry. Three flames with different mass percentage of propane in the fuel blends of 0%, 10%, and 20% were studied. The combustion intermediates were identified by comparing the measured IEs with those values in literatures. Mole fraction profiles of the main species were compared among the three flames. The experimental results provide detailed experimental data in understanding the combustion of n-heptane and n-heptane/propane blends in engine. They are also helpful in establishing and verifying the kinetic model. © 2009 Combustion Institute. All rights reserved.

关键词： Combustion

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flow visualization study of two-phase flashing spray with iso-pentane 14

Flow visualization study of two-phase flashing spray with is...

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14th International Conference on Liquid Atomization and Spray Systems, ICLASS 2018

作者： Wang, J.F. Zhou, Z.F. Yang, T. Chen, B. Wang, G.X. Zhao, L. State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Department of Mechanical Engineering University of Akron AkronOH44325-3903 United States

The explosive flashing spray commonly occurs during the accidental release of flammable and toxic pressure-liquefied gases in chemical or nuclear industry. This work conducts a small-scale flashing spray experiment in house to simulate the accidental release, aiming to investigate the macroscopic atomization characteristics, which is helpful for the risk assessments and therefore minimizing the impact of the release hazard. The iso-pentane was taken as the working medium, and a transparent straight-tube nozzle with inner diameter of 0.6 mm and length of 40 mm was employed to generate the flashing spray vertically. A high-speed camera was used to record the images of the flashing spray. The whole dynamic evolution was obtained. The effects of injection pressure (0.6 to 2.4 MPa) and initial temperature (40 to 60 oC) were fully explored, respectively. The experiment results indicate that the superheat and injection pressure have a coupled effect on flashing spray. The release of superheat results in phase change with the generation of bubble within liquid, which facilitates the break-up of liquid core and ligament liquid. Meanwhile, the increment of injection pressure can enhance the disturbance of the flow and the number of nucleation. © 2018 Solar Turbines Incorporated.

关键词： Atomization

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Startup transient thermal-hydraulic analysis of a lithium heat pipe cooled reactor Core

Startup transient thermal-hydraulic analysis of a lithium he...

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2020 International Topical Meeting on Advances in Thermal Hydraulics, ATH 2020

作者： Liu, Xiao Tian, Zhixing Wang, Chenglong Tian, Wenxi Qiu, Suizheng Su, Guanghui Shanxi Engineering Research Center of Advanced Nuclear Energy School of Nuclear Science and Technology Xi'an Jiaotong University State Key Laboratory of Multiphase Flow in Power Engineering Xi'an710049 China

ISBN: (纸本)9780894487774

Heat pipe cooled reactor has been proposed for applying in the space station and underwater exploration featured with high reliability, low noise level and compact structure. A typical design of a heat pipe cooled reactor system is HP-STMCs designed by the University of New Mexico. It is conceptually designed as a fast reactor, lithiumfilled heat pipes that transfer heat to potassium heat pipes radiator and thermoelectric generators. In this paper, a code is developed for studying the operating thermal-hydraulic characteristics of the reactor core, which consists of core thermal-hydraulic model, neutron kinetics model and heat pipe startup model. The highest temperatures of fuel and matrix in reactor core shows at the 2nd channel, which reach 1720K and 1545K from the results of steady-state. As for the startup transient, the code for heat pipe cooled reactor core successfully predicts key parameters during startup transient, such as each layer material temperature of reactor core, a single heat pipe's temperature response and heat rejection power. The code has initially predicted the transient response of the heat pipe cooled reactor under 800W/s and130W/s power increasing rates. It is discussed that the startup strategy of power increasing rates is based on heat pipe transition temperature (916K). This research provides valuable experience for designing and formulating control strategies of the heat pipe cooled reactor. © ATH 2020 - International Topical Meeting on Advances in Thermal *** rights reserved.

关键词： Heat pipes

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