Large Eddy Simulation On The Reduction Mechanism Of Thermal Fluctuation In The Mixing Process Of Cold And Hot Flows

During the operation of natural gas transmission pipelines,water transportation pipelines,inbound pipelines,and various liquid chemical material conveying pipeline systems,the thermal fatigue failure of pipelines due to uneven temperature of pipeline fluids occurs frequently.It caused many accidents and losses.Therefore,in view of the thermal fatigue failure of T-junction pipes,the LES method is applied to study the flow and heat transfer of T-junction pipes under different jet conditions.It is also proposed to add a SK mixer in the mixing zone of T-junction pipe to weaken the temperature fluctuation of the mixing process and reduce the possibility of thermal fatigue failure.The results show that the structure and flow velocity of the T-junction pipe have a great influence on the wall fluctuation during the mixing of the hot and cold flow.In the 3:1 pipe diameter ratio and 1:2 flow ratio,the temperature fluctuation of the wall of the confluence pipe is the smallest,and the possibility of thermal fatigue failure of the pipe is the lowest.Filling the SK mixer is beneficial to reduce the temperature fluctuation of the wall of the confluence pipe,and in the 3:1 pipe diameter ratio?2:1 speed ratio and-25 °C temperature difference,the SK mixer has the best effect of slowing the thermal fluctuation of the wall of the confluence pipe.The embedded depth of the SK mixer has a great influence on weakening the thermal fluctuation of the inner wall of the T-junction pipe,while the number of SK mixer blades has less influence on weakening the thermal fluctuation.The SK mixer with three blades at-115 mm embedded depth has the best effect on reducing the thermal fluctuation of T-junction pipe.This paper theoretically expounds the mechanism of thermal fluctuation,numerically simulates the flow and heat transfer of T-junction pipeline,and proposes a new pipeline structure to weaken the thermal fluctuation during the mixing process of hot and cold flow.These are of great scientific significance and practical significance for exploring the phenomenon of thermal mixing and thermal fluctuation in T-junction,and improving fluid mixing efficiency for us to understand,prevent and weaken T-junction thermal fatigue and optimize pipeline design and operating parameters.