Research On Fluid Thermal Mixing And Its Attenuation Mechanism In T-Type Pipeline

T-type pipeline is one of the main components in pipeline systems such as petrochemical plants,electronic cooling equipment and power plants.It connects various pipelines to form a huge pipeline system,which is often used to mix fluids with different temperatures.The temperature fluctuations in the pipeline are also caused by the thermal mixing of the fluid in the main branch pipe in the pipeline.When the thermal mixing is insufficient,the fluid temperature fluctuations near the wall surface of the pipeline increase,causing the pipe to bear the alternating temperature load,causing the pipe wall Withstands periodic thermal stress,causing wall rupture and penetration,and eventually causing thermal fatigue failure of the pipeline,which strongly affects the structural integrity and service life of T-type pipelines.In view of this,this paper uses the LES method to combine heat transfer and solid mechanical units to numerically simulate the fluid flow and heat transfer in a T-shaped pipeline.The main research results are as follows:In the T-shaped flow transmission pipeline,the jet flow condition,the incident angle of the branch pipe and the temperature difference of the fluid all have a great influence on the flow and heat transfer in the pipe.Combined with the temperature,velocity and wall stress distribution law,it is found that the temperature fluctuation of the pipe wall is smaller than that of the deflection jet and the impact jet when the wall jet is working.The fluid mixing area is mainly located on the upper wall surface of the pipeline,and the maximum stress value of the wall surface at this time is also lower than the other two working conditions.When the incident angle of the branch pipe decreases,the temperature fluctuation of the pipe wall also decreases.When the incidence angle of the branch pipe is 30,the wall stress value is the lowest,and the distance and time required for the fluid to mix to a stable state also become longer.With the decrease of fluid temperature difference in the main branch pipe,the fluctuation of wall temperature first decreases and then increases.When the fluid temperature difference in the main branch pipe is 20?,the thermal stress on the pipe wall is minimum.Adding a mixer to the T-tube can slow down the thermal fluctuation of the wall to a certain extent.Numerical simulation results show that the wall jet,the incident angle of the branch pipe at 45 °,and the main branch pipe temperature difference of 20 ° C are the optimal working conditions for the mixer.At this time,the minimum temperature fluctuation of thewall surface appears and the high stress concentration of the pipe wall also disappears,the possibility of thermal fatigue failure is the lowest.The research results have important practical significance and guiding role in understanding the flow and heat transfer nature of thermal fatigue problems in T-type pipelines,reducing thermal oscillations in industrial pipelines,reducing the occurrence of thermal fatigue failures,and ensuring the safe operation of pipeline systems.