Flow Field Simulation Of Micro-patterned Surface To Inhibit Microorganism Adhesion

Treated sewage source heat pump technology has a good application prospects,but because of the complex water quality,it is easy to form biofouling on the surfaces of the heat exchangers,which seriously affects the overall performance of the heat pump system.Micro-patterned surface method is a noval approach of physical anti-fouling method,by changing the heat transfer surface micro-topology to achieve anti-fouling effect.At present,most scholars have explored the influence of the micro-pattern size and shape on the inhibition effect.However,the limitation of the experimental method limits the research on the inhibition mechanism.The simulation of micro-patterned surface method is not enough,and the relationship between the change of flow field and the possibility of biofouling attachment is unclear.In this paper,Fluent numerical method is used to simulate the distribution of shear force field on different micro-patterned surfaces.Simulation results are compared with the experimental results to explore the inhibition mechanism and how the factors influence microorganism attachment.These conclusions can be a reference for the selection of micro-patterned surface type.Firstly,simulation scale is discussed,from the beaker scale model which is most similar to the experiments,to the simplified protuberance scale model and the coupon scale model.The best geometric model,coupon scale model,is gradually determined.Secondly,the simulation of the three hanging scale geometry models is carried out.The effects of the micro-pattern size,the micro-pattern shape,and the flow rate on the wall shear stress are explored.The characteristics and the application range of the different geometriy models are discussed.Finally,the simulation results are verified.The simulation results are compared with the experimental results to explore the inhibition mechanism of micro-patterned surface method,and the simulation results are used as a reference to select the experimental scheme of micro-patterned surface.The results show that the concave or convex of the micro-pattern only have an effect on the wall shear stress of the initial micro-pattern,which has little effect on the followers.The wall shear stress increases with the decrease of the micro-pattern size.When the size is between 1-5 μm,the wall shear stress is significantly large,biofouling growth is slow;when the size is between 10-100 μm,the decreased magnitude of wall shear stress is smaller with the size increase,and the change of the biofouling growth rate is not obvious with the size change.The wall shear stress of the stripe-shaped surface is larger than that of the same-sized tube-shaped surface.When the size is between 1-5 μm,the wall shear stress of the stripe-shaped surface is significantly larger than that of the tube-shaped surface,and the biofouling mass of the stripe-shaped surface is slightly smaller than the tube-shaped surface,but other larger sizes have no significant difference on the mass and wall shear stress.The average wall shear stress increases linearly with the increase of flow velocity.The biofouling inhibition effect is better when the micro-pattern size is small.Micro-patterned surface method inhibits the biofouling growth by changing the wall shear stress.The increase of wall shear stress makes the biofouling denser,and make the bacteria more difficult to attach,especially in the initial stage of bacteria attachment,thereby inhibiting the biofouling growthg.Wall shear force is also a good characteristic parameter of bacteria adhesion and micro-patterned surface method inhibition effect.