Analysis of natural circulation frictional resistance characteristics in a rod bundle channel under rolling motion conditions

摘要

In order to study the frictional resistance characteristics of a rod bundle channel under ocean conditions, a natural circulation experiment was performed in a 3 x 3 rod bundle channel under rolling conditions. The characteristics of the instantaneous frictional resistance coefficient in the rod bundle channel under rolling conditions are obtained by analyzing newly obtained experimental data. The experimental results show that the frictional resistance coefficient varies with the rolling conditions. The larger the rolling amplitude and frequency, the larger the average value of the frictional resistance coefficient, and the greater the fluctuation of the coefficient. It is also affected by the fluid property parameters. The hotter the fluid in the channel, and the faster the fluid velocity, which means the larger heating power and the steady state Reynolds number, cause the coefficient to decrease, and the fluctuation of the coefficient will also decrease. A new correlation function of the instantaneous frictional resistance coefficient under differing rolling conditions is developed and compared with these newly presented data. The correlation function is a good predictor of the frictional resistance coefficient and is in good agreement with the experimental results over a broader range of conditions than previous functions and is also applicable for both laminar and transitions fluid flow. This new correlation function introduces the viscosity correction factor based upon the previous research, which makes it more widely applicable in predicting the instantaneous frictional resistance coefficient under rolling conditions. This newly developed function should be useful for design considerations for passive cooling for sea-based nuclear reactor cores.