单棒通道流动振荡诱发沸腾临界可视化实验研究

Visual Experimental Study on Boiling Crisis Induced by Flow Oscillation in a Single Rod Channel

为深入分析沸腾两相流动振荡诱发沸腾临界的影响特性,本文以去离子水为工质,横截面19 mm×19 mm、中心为外径9.5 mm的单棒通道为研究对象,通过在不同热工参数下开展沸腾两相流动特性可视化实验研究,结合汽泡行为和汽-液界面特性,分析流动振荡诱发沸腾临界的影响特性。研究结果表明,低压力、低质量流速和低入口过冷度下,极易出现流动振荡,并导致沸腾临界提前发生,此时的临界热流密度与稳定工况下相比明显偏低;随着壁面热流密度不断增加,流道中两相流型先后出现泡状流、弹状流、合并弹状流、搅混流、剧烈搅混流、不稳定环状流;当流动出现剧烈振荡时,流道存在回流;发生沸腾临界时流道压降波动最大,对应的流型为不稳定环状流。因此,单棒通道内流动振荡可能会导致沸腾临界提前发生。

In order to deeply analyze the influence characteristics of boiling crisis induced by boiling two-phase flow oscillation,this paper takes deionized water as the working medium,a single rod channel with a cross section of 19 mm×19 mm and an outer diameter of 9.5 mm at the center as the research object.Through visual experimental research on boiling two-phase flow characteristics under different thermal parameters,combined with the behavior of bubbles and vapor-liquid interface characteristics,the influence characteristics of boiling crisis induced by flow oscillations are analyzed.The results show that flow oscillation is easy to occur at low pressure,low mass flow rate and low inlet subcooling,which leads to the early occurrence of boiling crisis,and the critical heat flux is significantly lower than that under stable conditions;With the increase of wall heat flux,the two-phase flow patterns in the channel appear bubble flow,slug flow,combined slug flow,stirred flow,violent stirred flow and unstable annular flow;When the flow oscillates violently,there is reflux in the channel;When the boiling crisis occurs,the pressure drop fluctuation in the channel is the largest,and the corresponding flow pattern is unstable annular flow.Therefore,the flow oscillation in the single rod channel may lead to the early occurrence of boiling crisis.