Experimental study on thermal striping; Sodium experiment of paranel triple jets

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

A quantitative evaluation on thermal striping, in which temperature fluctuation due to convective mixing among jets causes thermal fatigue in structural components, is of importance for reactor safety. It is necessary for quantity of thermal striping phenomena to evaluate occurrence of temperature fluctuation, decay of temperature fluctuation near structures and transfer of temperature fluctuation from fluid to structures. The structural safety is clarified, based on the above information. In this study, a sodium experiment of parallel triple jets configuration was performed in order to evaluate temperature fluctuation characteristics in fluid, tansfer characteristics of temperature fluctuation from fluid to structure and toward inner structure. As for the experimental geometry, a cold jet on center and hot jets on both sides flowed vertically and along the wall. The temperature fluctuation intensity near the wall decreased as the discharged velocity of the jet decreased. The power spectrum density of the temperature fluctuation could be evaluated using Strouhal number based on the discharged velocities of the jets. In this experiment, the temperature fluctuation characteristics were independent of the discharged temperature difference of the jets and the bulk temperature. The temperature fluctuation intensity at the neighborhood of the wall decreased approximate 0.8 times in comparison to that at the furthest position from the wall. The temperature fluctuation in the structure could be predicted by the non-stationary heat conduction equation. Thus, the temperature fluctuation characteristics on the structural surface were predicted based on the measured data in the structure. The decay rate of the temperature fluctuation from the fluid to the structure decreased as the frequency of the temperature fluctuation increased. And the decay rate decreased as the discharged velocity increased. The phase delay of the temperature fluctuation, in which the temperature ...