Study On Hydrodynamic Characteristics Of Chinese-Knot Static Mixer

Efficient mixing and heat transfer of viscous fluid is of great significance to petrochemical,food and other process industries.Chinese-knot type static mixer is a new design based on the bending of hollow tubes with semicircle structure near the wall and crossed shape in the middle.Because of its structural effect and multi-stream heat transfer method,CKSM can obtain greater heat transfer performance with smaller temperature difference.Aiming at the viscous fluid in the tube,the computational fluid dynamic(CFD)simulation is used to study the flow characteristics,heat transfer and mixing performance.It can be seen from the results that the existence of CKSM provides a structured flow field,intensive radial mixing and weaken boundary layer.The axial velocity distribution of the fluid changes with the axial structure evolution of the static mixer,and the radial velocity distribution is central symmetry.The friction coefficient is used to calibrate the pressure drop of the tube.Under the same Re number,the friction coefficient is 3.4 times higher than empty tube.Moreover,the CKSM has a larger heat transfer area which can greatly enhance the heat transfer performance of viscous fluid.Under the same working condition,the Nu number of the wall is 1.9～3.2 times higher and the performance efficient coefficient(PEC)is 1.4～1.5 times higher than empty tube.When the inside of CKSM is heated by the heating media,the Nu number of CKSM is 2.7～4.0 times and the PEC is 1.9～2.7 higher than the empty tube.In addition,the Fc based on the field synergy principle(FSP)indicates with CKSM elements improves the comprehensive performance inside the heat exchange tube.The CKSM can enhance the mixing performance of viscous fluid as well.The existence of CKSM is of good help in improving the flow pattern and mixing performance in the tube.The RTD results shows that more the repeating elements are,the closer the flow pattern is to the ideal advection state.The comprehensive mixing efficiency of CKSM is better than SMX with the same structural units.The new efficient Chinese-knot static mixer can coordinate the temperature field and flow field in the tube,and enhance the heat and mass transfer process of high viscosity fluid.