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Report No.

Study on thermalhydraulics in thermal striping phenomena; Experimental analysis of sodium parallel triple-jet DNS

Kimura, Nobuyuki; Nagasawa, Kazuyoshi*; Miyakoshi, Hiroyuki; Miyake, Yasuhiro*; Igarashi, Minoru; 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, during heat transfer from fluid to structural surface and thermal conduction in the structure. Temperature fluctuation characteristics due to convective mixing will be influenced by the velocity/temperature boundary layers near the structure. In this study, an experimental analysis was performed using DNS in order to separate influence of heat capacity of the structure and to evaluate an attenuation due to the boundary layer near the wall surface for a sodium experiment of parallel triple jets configuration. In the experiment, a cold jet on center and hot jets on both sides flowed vertically and along the wall, and the discharged velocities of triple jets were O.5m/s equally. The calculated temperature field was in good agreement with the experimental result at further position from the wall surface, including the power spectrum density of the temperature fluctuation. On the other hand, at near position from the wall surface, calculated temperature fluctuation intensity was not attenuated whereas the experimental intensity was decreased. This means that the intensity of temperature fluctuation is not decreased by the boundary layer. Thermal interaction between fluid and the wall will decrease the temperature fluctuation intensity in the fluid near the wall. The effect of wall friction on second moments of turbulence was evaluated.



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