Experimental study on thermal hydraulics in high cycle thermal fatigue; Temperature fluctuation in mixing tee and parallel triple jets along wall

Kamide, Hideki ; Igarashi, Minoru; Kimura, Nobuyuki; Hayashi, Kenji

When temperature fluctuation in fluid is transferred to the structure, it induces thermal load via thermal expansion of the structure. If the fluid temperature fluctuation amplitude and then thermal stress are large, structural integrity might be lost due to high cycle thermal fatigue, i.e., thermal striping. Water experiments were carried out for thermal hydraulic aspects of the thermal striping. A mixing tee and a triple-parallel jet along wall were selected as the test geometry. Detailed temperature and velocity fields were measured by movable thermocouple trees and particle image velocimetry. The power spectrum density (PSD) of temperature fluctuation could be estimated by a universal line, which is normalized by St number, when the flow velocity ratio and flow pattern was identical. Comparison of frequency characteristics between the temperature and velocity showed that the temperature fluctuation in the mixing tee was caused by Karman vortex behind the jet exiting from the branch pipe in case of wall jet condition.