通过建立考虑密度变化的三维CFD（计算流体动力学）模型，对单相自然循环条件下水平换热回路的流动特性进行了研究。在稳态流动分析中，首先通过三维CFD模型，获取了加热管道的径向温度和速度分布，发现管道截面温度场和速度场均为不均匀分布，这分别是由径向自然对流和对流换热系数决定的；其次，应用量纲分析的方法，整理归纳系统无量纲参数间的线性关系。在非稳态分析中发现水平换热通道出现不规则复杂流动，证明了混沌现象的存在，产生这种现象的原因是自然循环的特性与回路布置方式双重作用的结果。

A three-dimensional CFD model which of varied density is considered is proposed to investigate flow characteristics in a horizontal cooler and heater natural circulation loop. Firstly, it is found that the imbalance of temperature and speed fields acquired by three-dimensional CFD model in the stable flow conditions. Which decided by natural convection and convective heat transfer coefficient respectively. Secondly, linear relationships are concluded between some dimensionless parameters in the stable flow conditions based on dimensionless analysis method. It is found that irregular complex flow in the horizontal cooler and heater natural circulation loop in the unstable flow conditions, and exist of chaotic behavior is proved. The mechanism for this phenomenon is the result of the double effect of the natural circulation characteristics and the loop layout.

TQ022.12+1

东北电力大学博士科研启动基金项目（BSJXM-201312）；东北电力大学科研提升工程项目（201501）