Study on targeted influence of annular porous media and rotating impeller on thermal mixing in T-junctions

T-junctions are utilized as the thermal mixing equipment of hot and cold fluids in chemical and nuclear industries. However, the flow/heat induced fatigue damage can be generated in the pipe wall of the T-junction by the intense velocity and temperature fluctuations. In this study, new targeted regulation methods consisting of the annular porous media and rotating impeller are proposed to regulate the thermal mixing performances of the T-junction. Then, the thermal mixing processes of T-junctions with/without porous media and impeller are evaluated by the large eddy turbulence model. The temperature field, velocity field, secondary flow intensity and performance parameters of T-junctions are compared. It is found that the annular porous media can targetedly inhibit velocity and temperature fluctuations in the near-wall zone, reduce the temperature gradient and decrease the secondary flow intensity. Besides, the rotating impeller can targetedly promote the thermal mixing in the mainstream zone, inhibit the thermal stratification and increase the secondary flow intensity. If the annular porous media and rotating impeller are utilized together, the effects can be superimposed, which is the recommended choice in this study. Finally, the results can be used as the guidelines for the thermal mixing enhancement and fatigue inhibition of the T-junction.