Numerical simulation of mixing performance of thin plate static mixer
The thin plate static mixer has simple internals,high flux and low pressure,which can effectively reduce the energy consumption of dilution water mixing.The non-uniformity coefficient ψ and pipeline pressure drop Δp were used as evaluation indices.The mixing effect and pressure drop of four kinds of water injection modes,such as single straight pipe,single downstream plume pipe,single countercurrent plume pipe and double downstream plume pipe,were compared and analyzed by CFD(computational fluid dynamics).It is found that when the water injection pipe is installed at L/D=5.3 and a single pipe is injected,the strength of the radial secondary flow Se formed on both sides of the water injection changes slowly,resulting in a mixing"dead zone"in the mixer due to the stable vortex flow,which reduces the oil-water mixing speed of the static mixer.When ψ reduces to 0.05,the mixing distance exceeds 18D.This mixed dead zone also explains that local high concentration zone is easy to appear near the injection point of dispersed phase during single tube injection.When the double downstream plume tube is used,the impinging water phase produces a higher radial secondary flow intensity Se,and decreases rapidly.The rapidly changing flow field significantly reduces the mixing distance.Compared with single tube injection,the mixing distance decreases by 76.9％and the pressure drop increases by 1.5％whenψdecreases to 0.05.
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