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Study in steam-water two-phase flow heat transfer at high mass velocity of flow in vertical helical coiled tube

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2008年第3期29卷 423-428页

作者： Guo, Meng Zhao, Liang Mao, Yu-Fei Zhen, Fei-Qiang Zhang, Wen-Bin Guo, Lie-Jin Peng, Xiao-Feng State Key Lab. of Multiphase Flow in Power Engineering Xi'an 710049 China

Experiments were conducted to further understand the heat transfer in two-phase flow in vertical helically-coiled tubes. The experiments covered a wide range of pressure 8.0-15.0 MPa, mass flow rate 2500-4000 kg/(m2s), heat flux 200-800 kW/m2. The experimental segment is 2.335 meter long and made by φ14 × 2 mm steel tube. The diameter ratio D/d is 30.1. Through analyzing the influence of heat flux, mass velocity on average heat transfer coefficient, we acknowledge the activities of nucleate boiling and forced convection two mechanism on steam-water two-phase heat transfer in helical coils tubes at high mass flow rate. The average and local heat transfer coefficient correlations were obtained. At high mass flow rate conditions, the effect of heat transfer in the steam-water two-phase flow in helically coils is inclined to that of straight tube at same conditions and the results are compared.

关键词： Heat exchangers

Preliminary Conceptual Design with Neutronics and Thermal-Hydraulics Assessments of Fustar

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SSRN 2023年

作者： Zhou, Xingguang Zhang, Dalin Li, Xinyu Lv, Xindi Jiang, Dianqiang Tian, Wenxi Qiu, Suizheng State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Lab. of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi'an Jiaotong University Xi'An710049 China

The fluoride-salt-cooled high-temperature advanced reactor (FuSTAR) is an advanced small modular reactor, which aims to the electric supplement and clean heat production to western China. In this study, neutronics and thermal-hydraulics analysis are also carried out, and established the core layout and material ratio under the near-critical condition. The parameters of the designed core are evaluated quantitatively from various aspects. The results show that FuSTAR has sufficient shutdown depth, the equilibrium cycle is 3.24 years, and the discharge burnup depth is 106 GWd/MtU. The analysis of 1/6 core porous media shows that the peak fuel temperature under normal operating condition is 1009.3 K, which is far below the limit of 1573 K. Relevant design and analysis results can provide the reference for the subsequent small modular FHR design and construction. © 2023, The Authors. All rights reserved.

关键词： Computational fluid dynamics

flow Fluctuations and flow Friction Characteristics of Lead-Bismuth Eutectic in a Vertical Tube Under Rolling Conditions

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SSRN 2022年

作者： Liu, Zhipeng Zhao, Yafeng Tian, Wenxi Wang, Chenglong Qiu, Suizheng Su, Guanghui H. School of Nuclear Science and Technology Shaanxi Key Lab. of Advanced Nuclear Energy and Technology Xi’an Jiaotong University Shaanxi Xi’an710049 China State Key Laboratory of Multiphase Flow in Power Engineering China

The effects of rolling motion on the flow characteristics of lead-bismuth eutectic in a vertical circular tube are investigated experimentally. The results show that the pressure drop and flow rate of the forced LBE circulation fluctuate under rolling conditions. The effect of rolling motion on the flow characteristics decreases with the increase of the corresponding static Reynolds number. The rolling motion may increase the time-averaged frictional resistance coefficient of the LBE when flow rate is low. The critical value of the impact Reynolds number is about 125,000. As a result, the time-averaged flow rate decreases. The analysis shows that it is mainly the transverse additional force caused by the rolling motion increases the frictional resistance of the LBE. An empirical correlation is established to predict the frictional resistance coefficient under rolling conditions. This study may be useful in the thermal-hydraulic analysis of LBE as a working fluid under moving conditions. © 2022, The Authors. All rights reserved.

关键词： Reynolds number

Steady-state Multi-Physics Coupling Analysis of Heat Pipe Cooled Reactor Core

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SSRN 2022年

作者： Zhang, Zhipeng Wang, Chenglong Guo, Kailun Tian, Wenxi Qiu, Suizheng Su, Guanghui Department of Nuclear Science and Technology Shaanxi Key Lab. of Advanced Nuclear Energy and Technology Xi’an Jiaotong University Shaanxi Xi’an710049 China State Key Laboratory of Multiphase Flow in Power Engineering China

Due to the advantages of mobility, safety and universality, the heat pipe reactors have great competitiveness in many applications such as strategic defense locations, remote communities, and emergency locations. In addition, most of the heat pipe reactors are designed as solid-state reactors, which avoid the two-phase flow problem caused by the coolant transformation and make it possible to analyze the reactor with multiple physical field coupling. In this work, a typical heat pipe reactor has been carried out a 3-D neutronic-thermal-mechanical analysis, and steady state analysis is performed by OpenMC coupled with COMSOL. Coupling calculation results show that under normal operation, the maximum temperature and thermal expansion of core is 1338.94 K and 2.53 mm. In the steady-state coupling process, the influence of temperature parameters on physical calculation is mainly reflected in k eff and its power level, the maximum temperature drops from 1347.26 K to 1338.94 K, but it has little influence on power distribution. By coupling calculations, the maximum stress of the reactor is reduced by 5.78 MPa. The research results will support the subsequent development of multi-physics coupled transient analysis code for heat pipe reactors. © 2022, The Authors. All rights reserved.

关键词： Heat pipes

Measurement of saturated liquid density of dimethyl ether

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2006年第5期27卷 748-750页

作者： Wu, Jiang-Tao Wang, Bin Yuan, Le-Ming Liu, Zhi-Gang State Key Lab of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

A new vibrating tube densimeter was developed with a precision of better than ±0.5 kg/m3. Using this apparatus, the saturation liquid density of dimethyl ether was measured from 233.15 K to 320.15 K, and the max relative expanded uncertainty was 0.34%(coverage factor k = 2). The experimental data of this work were correlated as a polynomial function of the temperature with the published data of our previous work. The average and maximum relative deviation were 0.13% and 0.37%, respectively.

关键词： Dimethyl ether Saturation liquid density Vibrating tube

Characterization of High-Performance Nanostructured Wick for Heat Pipes

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SSRN 2023年

作者： Sun, Qishi Han, Ruiyu Guo, Kailun Wang, Chenglong Zhang, Jing He, Xiaoqiang Qiu, Suizheng Su, Guanghui Tian, Wenxi Department of Nuclear Science and Technology State Key Lab. of Multiphase Flow in Power Engineering Shaanxi Key Lab. of Advanced Nuclear Energy and Technology Xi’an Jiaotong University Xi’an710049 China Key Lab. of Nuclear Reactor System Design Technology China Nuclear Power Research and Design Institute Chengdu610213 China

To investigate the best performance wick forms to support the design and fabrication of high-performance heat pipes, in this paper, two kinds of nanostructured wick were prepared by the oxidation-reduction method. The effect of surface nanostructure on the wick performance was investigated by comparing the surface characteristics, capillary properties, permeability, and evaporation properties. The result shows that the nanostructured wick presented excellent super hydrophilic properties. A liquid-lift visualization experimental method for measuring the capillary performance factor M was proposed, and it was verified to be correct by the separation effect of the capillary pumping experiment under a vacuum environment. With the increasing oxidized degree, the densification of nanoparticles on the wick surface increased the capillary performance factor M from 8.68 μm to 13.81 μm, with a maximum enhancement of 59.1%. The effective capillary radius decreased from 4.70×10-5 m to 4.01×10-5 m, with a maximum reduction of 14.9%. The permeability increased from 4.33×10-10 m2 to 5.83×10-10 m2, with a maximum enhancement of 34.7%. The increase in porosity made the effective capillary radius dominate the competition for permeability, and the capillary performance factor decreased by 17.1%. The thermal resistance of the wick decreased with the enhancement of the capillary performance factor, which fell from 2.03×10-3 m2·K/W to 1.26×10-3 m2·K/W. The current study provides a reference for the future design and preparation of high-performance heat pipe wicks. © 2023, The Authors. All rights reserved.

关键词： Heat resistance

Numerical Study of High-Energy Spark Ignition Characteristics in a Scramjet Combustor

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SSRN 2024年

作者： Gao, Ziyan Zhang, Meng Zhang, Zhibo Wu, Yun Zheng, Xing Miao, Huifeng National Key Lab of Aerospace Power System and Plasma Technology Xi’an Jiaotong University Xi’an710049 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong Universiy Xi’an710049 China National Key Lab of Aerospace Power System and Plasma Technology Air Force Engineering University Xi’an710038 China Shaanxi Key Laboratory of Environment and Control for Flight Vehicle School of Aerospace Engineering Xi’an Jiaotong University Shaanxi 710049 China

Reliable ignition is a fundamental prerequisite for the scramjet engines. In order to improve the reliability of ignition, further enhance the application of spark ignition in engineering, and improve the ignition ability in the field of supersonic combustion, an innovative long electrode distance high-energy spark igniter (LHSI) system was proposed by our research team. To reveal the instantaneous ignition characteristics of the LHSI, a simulation model of the LHSI is established and verified by experiments. Based on this, the formation and development of the initial fire core of vaporized kerosene and the ignition characteristics of LHSI in a scramjet combustor were simulated and compared with the conventional high-energy spark igniter (HSI). The analysis revealed that the success of the cavity ignition is greatly influenced by the local equivalent ratio of the initial flow field and the penetration depth of the initial flame core. Meanwhile, the fore recirculation zone of the cavity plays a key role in stabilization and development of the initial fire core. Compared with the HSI, the LHSI can produce initial flame core with higher penetration and greater size, which is the main reason for why LHSI has a broader ignition boundary. © 2024, The Authors. All rights reserved.

关键词： Ignition

Experimental Investigation on flow and Heat Transfer Characteristics of Helium in Rectangular Narrow Slit Channel

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SSRN 2024年

作者： Li, Changzhong Wang, Chenglong Sun, Yanyu Chen, Ronghua Tian, Wenxi Su, Guanghui Qiu, Suizheng State Key Laboratory of Multiphase Flow in Power Engineering China Department of Nuclear Science and Technology Shaanxi Key Lab. of Advanced Nuclear Energy and Technology Xi’an Jiaotong University Shaanxi Xi’an710049 China China Nuclear Power Engineering Co. Ltd. Beijing100840 China

Helium is utilized as coolant in high temperature gas cooled reactors. Rectangular narrow slit channels are commonly present in the core. The flow and heat transfer properties of helium significantly affect the core temperature and flow distribution. This paper experimentally investigates the flow and heat transfer properties of high temperature helium in rectangular narrow slit channel. The Reynolds numbers ranged from 468 to 5327, the temperature ratio of wall to bulk from 0.91 to 1.22, the helium outlet temperature up to 944 K, and the maximum heat flux density up to 0.101 MW/m². In the experiment, the total and local convective heat transfer coefficients, along with the friction factors, are measured. Correlation equations for the Nusselt number and friction factor with respect to Reynolds number are derived. The primary findings are as below: the friction factors of helium in rectangular narrow slit channels are significantly larger than those calculated by current empirical correlations. In the turbulent zone, the measured local Nusselt numbers are in excellent accordance with the Gnielinski correlation;however, a significant discrepancy exists in the laminar zone. New flow heat transfer correlation equations are proposed on the bases of experimental data. Upon comparison, the total Nusselt numbers fall in the error of 10%, and almost all local Nusselt numbers and the friction factors fall in the error of 20%. © 2024, The Authors. All rights reserved.

关键词： Helium

Investigations of Sodium Droplet Spreading and Evaporation on Surfaces with Different Wettability Based on Lattice Boltzmann Simulations

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SSRN 2024年

作者： Tang, Songsheng Guo, Kailun Tian, Zhixing Wang, Mingjun Wang, Chenglong He, Xiaoqiang Su, Guanghui Qiu, Suizheng Tian, Wenxi School of Nuclear Science and Technology State Key Lab. of Multiphase Flow in Power Engineering Shaanxi Key Lab. of Advanced Nuclear Energy and Technology Xi’an Jiaotong University Shaanxi Xi’an710049 China Key Lab. of Nuclear Reactor System Design Technology China Nuclear Power Research and Design Institute Chengdu610213 China

The spreading and evaporation of sodium droplets is one of the fundamental phenomena in high-temperature heat pipes. The LBM sodium two-phase flow and phase transition model, which can simulate a huge liquid-vapor density ratio, is first established and validated. Then, the spreading and evaporation processes of sodium droplets on solid walls with different wettability are numerically simulated and analyzed. The main conclusions obtained are as follows: (1) The dimensionless spreading diameter and time of the droplet spreading process conforms to Tanner's power law, and the power exponent has exponential relationship with the equilibrium wetting angle;(2) The maximum dimensionless spreading diameter is negatively and linearly correlated with the equilibrium wetting angle;(3) Evaporation of sodium droplets under constant heat flow conditions shows a mixed pattern. The droplets will be detached from the droplet wall at the late stage of evaporation, and the larger the equilibrium wetting angle the sooner the droplets detach. © 2024, The Authors. All rights reserved.

关键词： Evaporation