Study On Flow Characteristics In SK Static Mixer

Static mixer, as new and efficient equipment, is used more and more broadly in process industry by its ability of strengthening chemical engineering process, and even maybe substitutes for traditional stirred reactor in many occations. In this paper, the flow characteristics under high Reynolds number in SK static mixer which has extensive applied in industry were described detailedly and veritably, and the mathematical model of pressure drop was put forward and resolved. The results give a favorable reference to the further study on heat and mass transfer and the design of mixer.The velocity field of SK static mixer was measured by three-dimensional LDA. The flow phenomena of rotating at two different directions in the same cross section were described. Rules of the magnitude and distribution of three-dimensional time-averaged velocities at helix ordinates were revealed. The effects of flow rate on time-averaged velocities and pulsatile characteristics were discussed. The results indicated that due to mixing elements, the fluid radial timed-averaged and pulsatile characteristics were enhanced and the flow field was anisotropic. The fluid velocity downstream was also measured in order to reveal its law of decline. To the amplificatory phenomena of experimental error, a new measurement method that the laser detector was changed its orientation at the second time was brought forward to advance veracity of experimental data.Four types of turbulent flow models were chosen to simulate the flow field in the static mixer, among them Reynolds stress model was validated credible by comparing the simulation results with experimental ones. By using this model, the flow fields of mixer with different aspect ratios under different flow rates were simulated. Moreover, the effects of aspect ratio and the numbers of mixing elements on flow field were discussed and the strain rates were calculated, by which the relation between mixing efficiency and flow field was established. A new numerical model of fluid resistance is put forward. Friction loss along mixer induced by friction of fluid with wall and local friction loss induced by reverse rotation and intersect of the elements at the junctions were discussed respectively, and the former was resolved theoretically.