核反应堆不同温度流体热混合的机理及实验研究

Mechanism and experimental study of thermal mixing of fluid with different temperature

探讨了在核反应堆热工流体力学中具有普遍意义的不同温度流体达到热混合均匀状态的过程和机理。１０ＭＷ高温气冷实验堆（ＨＴＲ－１０）热气导管内的流体热混合主要是径向对流扩散过程。用流体温度空间分布的方差表示混合效果，通过雷诺比拟方法求得在点热源下游流动流体的径向扩散系数解析解，与在模拟热气导管内的点热源下游流动流体的扩散混合实验的结果相符合。在雷诺数Ｒｅ为（１．００～３．５０）×１０５范围内，径向湍动系数εｒ的相应范围是（１．００～４．００）×１０－３ｍ２／ｓ。反映混合效果的湍动系数与流速ｕ之比εｒ／ｕ随雷诺数Ｒｅ变化不大，解释了在高温堆堆芯底部结构中Ｒｅ对流体混合效果影响不大的现象。

The mechanism and process of thermal mixing of fluid with different temperature in a straight pipe were studied, which has general significance in nuclear reactor thermohydraulic process. Radial convection diffusion is the main process that takes place in the hot gas duct(HGD) of 10 MW high temperature gas cooled reactor(HTR 10). Being expressed by spatial temperature difference distribution of mixing efficiency and using Reynolds similarity method, analytical solution of radial convection diffusion coefficient ε r of a point source flowing in a pipe is gained, and it is in good agreement with HGD mixing test data. The range of Reynolds number Re is (1.00￣3.50)×10 5, and ε r has a corresponding value range of (1.00～4.00) ×10 -3 m 2/s, the ratio between ε r and velocity u which indicates mixing efficiency changes lightly among Re range. The phenomena of Re making a slight difference of thermal mixing in the plenum and HGD of HTR 10 are explained in theory.