Hydrodynamic Modeling of the Helical Membrane Modules

Membrane fouling and concentration polarization can be greatly mitigated by using the helical membrane modules to enhance the mass transport process. In this study, experiments and computational fluid dynamics were used to investigate the transport phenomena in a helical membrane filter with several helical membrane modules. A model is constructed with a square filter which has three helical membrane modules embedded as not only turbulence promoters but also filtering elements. Direct numerical simulations based on the Navier-Stokes equations are performed over a range of characteristic parameters of membrane and aeration flux. The distributions of local parameters such as velocity, shear stress and turbulent kinetic energy on the membrane surface were obtained by numerical simulations with different helical angle and aeration flux. These parameters are directly related to mass transport enhancement. Results show that both wall shear stress and turbulent kinetic energy obtained from helical membrane modules are larger than those from flat membrane modules, and they increase with an increase of the helical angle. The average shear stress on the membrane surface increases from 0.097 Pa to 0.217 Pa as the helical angle changes from 0° to 360°. In addition, the flow field was analyzed by means of noncontact measuring and visualization device-Particle Image Velocimetry (PIV), and the vorticity as well as the turbulent kinetic energy were obtained from the velocity distribution. The measured data are in agreement with the numerical results. From the research, we can see that the helical membrane modules can enhance the transfer efficiently compared to the flat membrane modules, which means the concentration polarization and membrane fouling can be alleviated efficaciously, it can be concluded that the helical membrane modules can play an important role in government actions membrane separation engineering and its application prospect in industry is very broad.