大宽高比矩形窄缝通道沸腾起始点实验研究

Experimental Study on Onset of Boiling in Rectangular Narrow Channel with Large Aspect Ratio

矩形窄缝通道中的泡核沸腾起始点(ONB)预测对反应堆安全设计十分重要。针对通道尺寸为50mm×3mm×1000mm的竖直矩形窄通道,以去离子水为介质,通过监测壁面温度变化确认ONB的位置,研究了热流密度、质量流速、压力、入口过冷度等参数对ONB发生位置和壁面过热度的影响。收集并评价了已有的8个ONB预测模型,结合实验数据分析得到结论:基于池沸腾的ONB预测模型及其改进模型不能很好的适用于矩形窄通道内,尤其是针对质量流速带来的影响。一些针对矩形通道ONB预测开发的模型可以一定程度上反映ONB点壁面过热度随不同参数变化的发展趋势,但由于实验参数范围不够宽,适用范围和预测精度仍受到限制。结合影响矩形窄缝通道ONB发生的主要因素,推导了适用于计算宽谱参数工况下矩形窄通道中ONB点壁面过热度的解析解形式,并利用实验数据进行了拟合,新关系式超过95%的预测结果与实验结果偏差小于±20%。同时新关系式对其他相关公开文献的ONB数据预测仍在较好的误差范围内。

The prediction of onset of nucleate boiling(ONB)in rectangular narrow channel is very important for reactor safety design.For the vertical narrow rectangular channel with the channel size of 50mm×3mm×1000mm,using deionized water as the medium,the position of ONB is confirmed by monitoring the change of wall temperature.The effects of heat flux,mass flow rate,pressure and inlet subcooling on ONB location and wall superheat are studied.Eight existing ONB prediction models are collected and evaluated,and the conclusions are obtained by analyzing the experimental data:The ONB prediction model based on pool boiling and its improved model can not be well applied to rectangular narrow channels,especially for the impact of mass flow rate.Some models developed for prediction of ONB in rectangular channels can reflect the development trend of wall superheat of ONB points with different parameters to a certain extent.However,because the range of experimental parameters is not wide enough,the scope of application and prediction accuracy are still limited.Combined with the main factors affecting the occurrence of ONB in narrow rectangular channels,the analytical solution form suitable for calculating the wall superheat of ONB points in narrow rectangular channels under the conditions of wide spectrum parameters is derived,and the fitting is carried out using experimental data.The deviation between the predicted results of more than 95%of the new relationship and the experimental results is less than±20%.At the same time,the prediction of ONB data from other relevant published literatures by the new relationship is still in a good error range.