摘要
高温热管的启动是复杂的相变及流动过程,若发生传热振荡将造成温度波动,进而影响热管堆运行安全。本文通过实验及仿真方法研究高温钠热管在启动过程中的传热振荡现象及热疲劳后果。在竖直工况中,不同输入热流密度将引起钠蒸发速率变化,呈现不同振荡特征;热流密度提升时振幅下降,周期缩短;振荡发生时,若输入功率骤降,波形将从锯齿状转变为梯形状;在水平工况中,传热振荡被明显抑制。热管在堆内发生传热振荡时,应力风险区为热管蒸发段内壁中部;异相振荡时相较同相振荡工况应力均值升高,振幅下降,疲劳损伤减轻;当安全因子K低于1.4时热管不存在疲劳失效风险,K达1.4以上后损伤逐渐显著;其中同相工况疲劳损伤最严重,K=1.6时管壁材料疲劳寿命已降低至3.29年。本研究对高温钠热管传热振荡的机理分析及完善热管可靠性评估具有重要意义。
The start-up of a high temperature heat pipe is a complex multi-phase transition and flow heat transfer process,which may result in heat transfer oscillations,causing fluctuations in the heat pipe temperature and thus affecting the operational safety of the reactor.In this study,for the high temperature sodium heat pipe with a length of 1000 mm and a diameter of 20 mm,the evolution law of the heat transfer oscillation was summarized through start-up experiments under vertical and horizontal conditions.The finite element thermal-mechanical simulation and thermal fatigue program analysis of a localized heat pipe reactor core design with generalized characteristics were carried out,and the stress response and the consequences of fatigue damage induced by heat pipe heat transfer oscillations were investigated.The experimental results show that the change of sodium evaporation rate causes the change of heat pipe pressure under vertical condition,which affects the evaporation and reflux balance of working medium,and causes the oscillation of heat transfer in different characteristics during start-up process.Enhancing the input power will shorten the frequency and decrease the amplitude of the oscillation.When the heat flow density increases from 9973.71 W/m 2 to 12452.28 W/m 2,the temperature oscillation amplitude decreases by nearly 30%and the oscillation period is shortened by about 40%.In the heat transfer oscillation state,the heat pipe will still maintain the heat transfer oscillation when the input power is suddenly reduced,but the waveform changes from a sawtooth shape to a trapezoid shape.The oscillation is obviously suppressed under horizontal condition.Simulation results show that,when the high temperature heat pipe heat transfer oscillation occurs,the thermal fatigue failure risk area of the localized reactor core is the inner wall of the evaporation section of the heat pipe.Fatigue damage is the largest in same-phase oscillation.The average value of the stress increases when the peak temperature difference increases due to the phase difference of oscillation,but because the decrease in the amplitude of stress of different-phase condition,the fatigue damage is reduced compared to the same-phase condition.Considering the effect of the conservatism deviation and creep on the fatigue damage,the thermal fatigue analysis is based on the safety factor K.Fatigue safety analysis results show that when the safety factor K is lower than 1.4 there is almost no risk of fatigue failure.K reaches 1.4 or more fatigue damage is gradually significant.When K=1.6 the fatigue life of the pipe wall material reduces to 3.29 years.This study is of great significance in analyzing the mechanism of heat transfer oscillation of high temperature sodium heat pipe and improving the reliability assessment of heat pipe.
作者
张凌义
张智鹏
王成龙
郭凯伦
田文喜
苏光辉
秋穗正
ZHANG Lingyi;ZHANG Zhipeng;WANG Chenglong;GUO Kailun;TIAN Wenxi;SU Guanghui;QIU Suizheng(School of Nuclear Science and Technology,Xi’an Jiaotong University,Xi’an 710049,China)
出处
《原子能科学技术》
EI
CAS
CSCD
北大核心
2024年第5期1024-1032,共9页
Atomic Energy Science and Technology
关键词
高温钠热管
传热振荡
启动特性
热疲劳
high temperature sodium heat pipe
heat transfer oscillation
start-up characteristics
heat fatigue
