The Simulation Of The Flow Field In The Electrodialyzer By Computational Fluid Dynamics (CFD)

Electrodialysis, as the earliest used technology for water treatment, is becoming more and more important in various fields. One of the best choices for solving the problem of concentration polarization and fouling in the electrodialysis is to design the rational module of electrodialyzer. With the continuous development and improvement of CFD, it has become possible to achieve the research and simulation of the process of electrodialysis, as well the design and optimization of module electrodialyzer. In this paper, a three-dimensional numerical simulation of the flow field in the spacer channel was investigated through the Computational Fluid Dynamics, the purpose is to verify the effect of the geometric characteristics of the spacer on the fluid behavior and try to identify the optimal spacer.At first, the effect of the angles of spacer filaments on the fluid flow behavior in electrodialyzer has been investigated. Through the calculation and analysis of the pressure drop, the velocity vector contours and shear stress in the spacer channel, the optimal angle is identified. The results show that the pressure drop increases exponentially with the increase of the spacer filaments angle. The fluid turbulence in the local area becomes more intense with the increase of the angle. The shear stress near the membrane increases with the increase of the angle. By considering all the factors, the appropriate angle of spacer should be the range of 80°to 90°.Secondly, the effect of the geometric characteristics of the spacer including the configuration of the distribution sink and the length-width ratio of spacer on the fluid flow behavior in electrodialyzer was investigated. The results show the influent of the width of distribution sink is more significant than length of distribution sink. It is benefit to choose the wider distribution sink for fluid turbulence and mass transfer while the length of distribution sink is fixed, the optimal width of the distribution sink is 4mm.After analyzing the contours plots of velocity, velocity vector contours, shear stress, velocity distribution on some surface. The results also suggest that the growth of the length-width ratio of spacer can lead to increase of pressure drop, and the turbulence become more obvious, but death zone of velocity doesn’t decrease with the increase of the ratio. Therefore, the appropriate ratio must be selected according to the real demand. The ratio is 1:0.52 may be the best choice in this simulation.The conclusion of this paper help us have a comprehensive understanding on the electrodialyzer flow field with the spacer geometric characterization variation, which is benefit to designing, optimizing and transforming electrodialyzer module. It has some significance for enterprise energy-saving and profit improvement.