Study Of Diffusion Influence On Sodium Mass Transfer

Author : Azadeh Ghorbani
Publisher :
ISBN 13 :
Total Pages : 246 pages
Book Rating : 4.:/5 (962 download)

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Download or read book Mathematical and Experimental Predictive Models for Sodium Chloride Mass Transfer Along and Across the Electrodialyzer written by Azadeh Ghorbani and published by . This book was released on 2016 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt: Electrodialysis is one of the membrane-based desalination technologies which is widely used to desalinate natural water and represents one of the most important desalination methods. Mass transfer in Electrodialysis is very important therefore many studies have been carried out to investigate transfer processes through ion exchange membranes. The purpose of this work is to develop a three dimensional model that incorporates all relevant factors--migration, diffusion, and convection--which can predict salt removal concentration gradient in electrodialysis cells more completely than conventional models. Additionally, this model will find the concentration and potential distribution in both flow and current direction in dilute compartment. As a demonstration of this approach, the study develops mathematical and experimental model that incorporates all three contributions to predict NaCl mass transport through a rectangular electrodialysis cell. In order to evaluate the reliability and accuracy of the model, the results are compared with theory as calculated by the Nernst-Planck equation and Shaposhnik model. The equations used in the model – the complete Navier-Stokes, continuity, Poisson, and steady state Nernst-Planck equations – are solved by the finite difference numerical method in the particular control volumes. Additionally, this study employs theory and experimental data from a laboratory-scale electrodialyzer to develop a mathematical model for predicting sodium chloride mass transport and concentration distribution along the electrodialyzer as a function of feed concentration, feed flow rate, applied voltage, and pressure. The findings of the experiment confirmed that concentration distributions are nonlinear along both the dilute and concentrate compartments. The results also confirmed that increases in pressure and feed flow rate have a negative effect on salt removal, linear and nonlinear for pressure and flow rate respectively. In the investigated ranges, higher voltage increased salt removal at a constant feed concentration.