Experimental study on temperature fluctuations on plate surface induced by coaxial-jet flow

In nuclear reactors, temperature fluctuations of fluids may cause fatigue damage to adjacent structures; this is referred to as thermal striping. Research on thermal striping in the upper plenum has mainly focused on fluid fields. Few experimental studies have been reported on solid structures in a fluid field with a coaxial jet. This study entailed an experimental study of the temperature fluctuations in the fluid and on a plate surface caused by a coaxial jet. The temperature fluctuations of the fluid and plate surfaces located at different heights were analyzed. The cause of the temperature fluctuation was analyzed using a transient temperature distribution. The results show that the mixing of the hot and cold fluids gradually becomes uniform in the positive axial direction. The average surface temperatures tended to be consistent. When the jet reaches the plate surface, the swing of the jet center, contraction and expansion of the cold jet, and changes in the jet shape result in temperature fluctuations. The intensity of the temperature fluctuation was affected by the position. More attention should be paid when the plate is located at a lower height, and between the hot and cold-fluid nozzles.