竖直环形通道内液氮流动沸腾的数值模拟

Numerical simulation of liquid nitrogen boiling flow in vertical annular pipe

在多尺寸组模型的基础上,从加热壁面上脱离汽泡的受力分析入手,对液氮过冷流动沸腾模型进行了修正。将新模型应用于环形通道内液氮过冷流动沸腾的数值模拟,同时为了比较,采用基于Kirichenko,Fritz汽泡脱离直径公式的多尺寸组模型对同一管道内液氮过冷流动进行了数值模拟。结果表明:结合脱离汽泡受力分析模型的多尺寸组模型可用来预测流动沸腾过程中的汽泡起飞直径及其变化趋势。同基于Kirichenko,Fritz汽泡脱离直径公式的多尺寸组模型相比,新模型有助于改善管道内汽泡尺寸分布以及空泡系数的预测,从而有助于准确分析弹状汽泡及间歇泉的形成。

Based on the multi-size group（MUSIG） model,the mathematic model of subcooled boiling flow of liquid nitrogen was amended according to the force analysis for departing vapor bubble on the heating wall.The new model was used to simulate the three-dimensional boiling flow of liquid nitrogen in vertical annular pipe.For comparison,similar simulation was performed by using multi-size group model based on Kirichenko′s,Fritz′s empirical correlations for bubble departure diameter separately.The numerical results show that the new model can be used to predict the bubble lift-off diameter and the change trend of this value.Compared with the MUSIG model based on Kirichenko′s,Fritz′s empirical correlations for bubble departure diameter,the newly proposed MUSIG model can help to improve the precision of predicting the local bubble size distributions and void fraction,accordingly can help to accurately analyze the formation of slug bubble and occurring of the geyser.