The Transitional Temperature Fluctuation Caused by the Swirling Cavity Flow in a Branch Pipe with a Closed End

Abstract

Many pipes branch off from the main pipe in plants. When the main flow in the main pipe is hotter than the fluid in a branch pipe that branches off downward, the hot water penetrates into the branch pipe with the cavity flow. The strength of this cavity flow varies with long period. The thermal stratification in the branch pipe is, therefore, fluctuated by this cavity flow. Some experiments and numerical simulations were conducted to investigate this fluctuation in a straight branch pipe. The swirling vortex structures were observed in experiments and numerical simulations. The transient temperatures of the water near the wall in numerical simulation showed good agreement with the experimental results. These fluctuating temperatures were synchronized with the swirling flow velocities in long period. The period of these were about 60-140 seconds. The amplitude of the fluctuating temperature became small with long time span.