Simulation Analysis Of Dynamic Process Of External Pressure Submerged Hollow Fiber Membrane

Membrane fouling has limit to hollow fiber membrane application in the waste water treatment,and membrane shear stress and membrane displacement caused by fluid could decrease the membrane fouling in the external pressure membrane reactor.Computational Fluid Dynamics(CFD)combined with experiment is applied to study membrane fouling layers decreasing trend and the effect of membrane shear stress on membrane fouling decrease.Firstly,in the CFD simulation,hydraulic shock on membrane displacement and membrane shear stress is researched in this work.Assembling that membrane fouling layers are formed after the membrane filtration,membrane displacement could enhance the membrane shear stress contributing to the membrane fouling control.According to the module structure simulation results in this work,membrane shear stress in the middle part is much less than that of the two ends,because axial displacement in the middle is much less than that of two ends,and membrane shear stress has a formulation with the equivalent elastic stress.Besides,membrane shear stress is10 times of the equivalent elastic stress.Secondly,liquid and solid phase flow in the membrane oscillation was simulated using the FSI(Fluid and Solid Interaction)in this study.Different inlet velocity was chosen to study the effect of inlet velocity on the membrane oscillation and displacement,and different membrane shear stress was compared between the different inlet velocity.In this work,inlet velocity is0.5m/s,0.8m/s,1.0m/s,1.2m/s,1.5m/s,1.8m/s,2.0m/s.According to the results,the more inlet velocity,the more the membrane oscillation frequency.And more inlet velocity could increase the maximum of membrane shear stress,but reduce the membrane shear stress distribution uniformity.So it is not that more inlet velocity could contribute to more shear stress.Analyzing the fluid dynamics property in the best at the best inlet velocity,we can get that the large membrane shear stress occurred at the lower part of the membrane fiber,and membrane fouling could be controlled at the lower part of the membrane fiber.Except this,larger membrane shear stress could slow the filtration layer to form,and membrane shear stress could effectively decrease the membrane fouling.Last but not least,this work included that experimental verification of the CFD simulation results in order to verify that the CFD simulation results are right,and a pilot-scale experimental equipment was set up as the Fluid-Solid-Interaction experiment.In this experiment,FBG grating was applied to monitor the membrane shear stress.Different membrane anti-fouling ability were compared under different inlet velocity,in order to get the most comprehensive ability of membrane anti-fouling.Membrane fiber looseness could increase the membrane oscillation displacement.According to the experimental results,membrane oscillation could optimize the membrane reactor system operation effect and decline the energy cost,and achieve the operation effect optimization.Above all,membrane oscillation could effectively decrease the membrane fouling layer accumulation and at some extent could recover the membrane filtration ability.Experimental and simulation results mainly coincide,that is,membrane oscillation could increase the membrane shear stress and decrease the membrane fouling.