Abstract
Based on CFD and film theory, filtration’s two-dimensional CFD model of the hollow membrane was established by integrating the mass transformation and the hydrodynamic transportation. Parameters of concentration polarization in the membrane channel (i.e., solute mass concentration, concentration polarization factors, and concentration polarization layer thickness) were estimated under different hydraulic conditions. In addition, the algorithm for the thickness of the concentration polarization layer has been improved. The results showed that decreasing the feed Reynolds number or increasing the transmembrane pressure can enhance the concentration polarization phenomena. Concentration polarization parameters increased sharply at the initial place (X/H < 25, where H is the entrance width, X is the distance from entrance) and then flatten out (X/H > 25) along the membrane channel; solute concentration and concentration polarization factors were arranged in a U-shape in the membrane channel’s cross-section. The improved algorithm could match well with cross section data, δ2H at X/H = 1, 25, and 200 are 0.038, 0.11, and 0.25, respectively, which can reasonably reflect the distribution of the concentration polarization phenomenon in the membrane channel.
Highlights
During the past decades, membrane technologies have played an increasingly important role in the industrial separation process and water treatment field
This study focused on the Computational fluid dynamics (CFD) simulation of the concentration polarization of the hollow membrane. which few studies had focused on
Due to the limitation of the solver, solver, which is limited to the prediction of hydrodynamic conditions for fluids near the which is limited to the prediction of hydrodynamic conditions for fluids near the memmembrane, it is assumed that the membrane is an impermeable wall with zero concentrabrane, it is assumed that the membrane is an impermeable wall with zero concentration tion accumulation
Summary
Membrane technologies have played an increasingly important role in the industrial separation process and water treatment field. Previous studies about CFD technology paid attention to the hydrodynamics and the fluid flow pattern adjacent to the membrane, which can distinctly impact the permeation and solute rejection mechanism across the membrane [7,8,9,10] These studies may provide incorrect predictions for the phenomenon based on film theory and assuming the membrane as an impermeable wall with zero concentration build-up and zero mass transmembrane transportation [11,12,13]. Amokrane [4] studied the concentration polarization in the spacer-filled spiral wound membrane by simplifying the film theory and taking into the rejection coefficient R > 0.99 These studies have solved the CFD limitations that concentration build-up and mass transmembrane transportation were ignored, and they conducted the filtration modeling for the plate membrane or spiral wound membrane. The calculation method of the thickness of the concentration polarization layer is optimized to overcome the shortcomings of small values and to better couple the cross-sectional analysis data
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