The Numerical Simulations Of The Mixing Of Hot And Cold Fluids In The T-junction With A Upstream Elbow

The piping system play a very important role in the factory machines,and the elbow and tee junction are most widely used in piping transportsystem. The elbow is used to change the direction of fluid in the pipingsystem which can save space. The flow field in the curved pipe is verycomplicated, can lead a secondary flow in the pipe easily. Andthe total pressure and energy of the fluid lose, the formation oflocal barriers increases flow resistance, reduces the exchangeefficiency of the heat and mass.The T-junctions are widely used to connect pipes and optimizepipelines in the piping systems. When two fluids with differenttemperature mix in the T-junction, the thermal fluctuation will occur. Thethermal fluctuations near the wall may lead to thermal stress easily, thencause fatigue failures and cracks on wall. Several pipe crack and leakageaccidents sometimes happened in factories, which make people attachmuch importance to the thermal fatigue problem in tee junction.Although the T-junction has typically been considered a single component, the mixing tee is usually connected to another part of thecomplex piping system—one of these parts is a90-deg bend that typicallyexists upstream of the T-junction and has strong effects on the mixingmechanismIn this paper, the mixing process of hot and cold fluids in tee junctionwith a90-deg bend upstream was simulated. The turbulent model of largeeddy simulation (LES) was adopted in this simulation. By simulation, wenumerically observe the thermal fluctuation phenomena in a hot and coldfluids mixing tee. The simulation results were compared with those of theexperimental ones published in previous literature, which shows that thelarge eddy simulation is not only reliable but also economical approach.Several mixing process in different condition were simulated toanalyze the effects of curved ratio (Cr) and axial distance (L) on mixingcourse and thermal fluctuation. It can be concluded that by increasing thecurvature ratio of bends the temperature and velocity fluctuationsbecomes lower; by connecting the branch piper farer to the bend, thetemperature and velocity fluctuations becomes lower.