沸腾诱导的两相流脉动特征模拟分析

NUMERICAL ANALYSIS ON THE CHARACTERISTICS OF THE TWOPHASE FLOW OSCILLATIONS INDUCTED BY BOILING

两相流脉动现象广泛存在于有相变过程的换热设备中,对生产工艺流程和运行安全等有着重要影响。本文基于实验观察测试事实构建数值模型,对沸腾诱导的两相流脉动现象和基本特征进行数值模拟分析。一定条件下沸腾两相流系统宏观参数将在时域上出现脉动,包含高频和低频成分。脉动高频成分由核化产生气泡直接引起,而低频成分则是多核化点产生的高频成分的叠加结果。进出口压降、壁面热流密度、核化点数密度等对脉动特征有实质性影响。

Two-phase flow oscillations are widely encountered in heat exchangers with phase change, showing an important influence on the production process and operation safety. In present investigation a numerical model was proposed based on the available experimental observations and fundamental characteristics of two-phase flow oscillations induced by boiling. The completed simulation shows that the two-phase flow oscillations occur under certain situations for a single tube indicates, and the oscillations normally are composed of high-frequency and low-frequency components. The highfrequency components are directly induced by boiling nucleation and bubble generation at nucleation sites, and the low-frequency components are the result of the superposition of the high-frequency components. Some parameters including the pressure drop, applied heat flux and nucleation site density have a influence on the characteristics of the oscillations.