Flow and Separation Characteristics of Oil Droplets in Shallow Annular Counter-Flow Field

The characteristics of oil droplet flow and separation in shallow annular multi-layer counter-flow channels have been inadequately investigated.In this paper,the flow and separation of dispersed oil droplets in shallow annular counter-flow channels and the velocity distribution in shallow multi-layer flow channel were analyzed by using computational fluid dynamics(CFD)methods.The results indicate that the plate length required for the oil droplet floating upward in the shallow annular counter-flow channel to the surface of the inclined plate is 96 mm,less than the theoretical plate length(122 mm).The inter-layer velocity distribution in the shallow channel has a great impact on the separation efficiency,and the velocity at the inlet of the lower channel peaks at 0.008 05 m/s.The oil droplet may encounters a cross flow when it floats upward in the shallow annular multi-layer channel,which will impede greatly the separation efficiency in the channel.The sliding distance is a key factor influencing the separation efficiency.When the plate length is 350 mm and the grain size of oil droplet is 50 μm,the sliding distance accounts for 38.35% of the plate length.The research findings provide theoretical support for the innovative design and optimization of compact produced water treatment equipment based on the theory of shallow settling and enhanced separation.