Investigation of fluid phenomena in a branch pipe of nuclear reactor

Many pipes branch off from a main pipe in industrial plants. Hot water penetrates into the branch pipe with a cavity flow induced by the main flow when fluid temperature in the main pipe is higher than that in the branch pipe. The penetration causes thermal stratification in the branch pipe. The cavity flow causes a spiral flow with long period fluctuations. The thermal stratification layer fluctuated and caused fluctuations of the wall temperature at an elbow of the branch pipe when the burst phenomena occurred. The characteristics of velocity distributions in the branch pipe for inner diameters from 21 mm to 43 mm were investigated by LDV. (author)