Analogy of electrodialysis mass exchangers to heat exchangers

Heat exchangers and electrodialysis (ED) systems share a strong analogy. A method similar to ε-NTU is developed for designing ED mass exchangers that can be called ε-MTU (effectiveness-mass transfer units). The effectiveness is defined as the system transport ratio over its maximum possible value. Two different modelling results are shown depending on whether water transport is accounted for (as in a high salinity source) or not (as in brackish water). The equations that relate the MTU, the concentration ratio (CR), and the resistance ratio (ER) to other system parameters such as effectiveness are developed. Finally, the model is tested by comparing its results to both salinity levels. The errors found are ∼0.02 % for the brackish water source (3500 ppm) and ∼0.44 % for the high salinity source (150,000 ppm). Therefore, the ε-MTU model developed can help to design and evaluate ED systems in a robust manner.