Experimental study on thermal striping phenomena; Evaluation on transfer characteristics of temperature fluctuation from fluid to structure

Kimura, Nobuyuki; Miyake, Yasuhiro*; not registered; Nagasawa, Kazuyoshi*; not registered; Kamide, Hideki 

A quantitative evaluation on thermal striping, in which temperature fluctuation due to convective mixing causes high cycle thermal fatigue in structural components, is of importance for reactor safety. The reasonable and safety design could be approved by taking account of decay of temperature fluctuation in fluid, heat transfer from fluid to structural surface and thermal conduction into structure. In this study, a sodium experiment of parallel triple jets configuration was performed in order to evaluate transfer characteristics of temperature fluctuation from fluid to structure. As for the experimental geometry, a cold jet at the center and hot jets in both sides flowed vertically along a wall. The temperature fluctuation is transferred from fluid to the wall in the wall jet geometry. In addition, double jets experiment was carried out. The experimental parameters were discharged velocities of the jets. The temperature fluctuation intensity decreased as the frequency of temperature fluctuation increased where temperature fluctuation was transferred from fluid to structure. The time-delay of transfer of temperature fluctuation from fluid to structure decreased as the discharged velocity increased. The non-stationary heat transfer characteristics from fluid to structure could be described by using a time-constant heat transfer coefficient. The heat transfer coefficient was proportional to Peclet number to the power of 0.8 and independent of the flow pattern in which the ratio of discharged velocities of the jets was varied.