Mass transfer in the U-turn of an electrodialyzer

✍ Scribed by In Ho Kim; In Seok Kang; Ho Nam Chang

• Publisher: Elsevier Science
• Year: 1980
• Tongue: English
• Weight: 980 KB
• Volume: 33
• Category: Article
• ISSN: 0011-9164
• DOI: 10.1016/s0011-9164(00)80336-7

✦ Synopsis

As a link in the chain of the hydrodynamic theories on electrodialysis, the mass transfer rate in the U-turn of a tortuous spacer was investigated . Besides, the solutions by Sonin and Probstein (1968) for a straight channel geometry were modified using a concentration profile approximated with a third order polynomial .

The flow in a U-turn geometry at low Reynolds numbers was analyzed with the aid of the potential flow theory, and the related mass transfer problem was solved in connection with the flow field solution for the U-turn and the revised concentration distribution . Theoretical analysis showed that the desalting efficiency in the U-turn was nearly the same as that in the straight channel for low polarization, but the efficiency was lower for high polarization . Experimental results for the U-turn geometry were in good agreement with the theory for the case of low polarization . However the discrepancy between the two was noticeable for the case of high polarization . Also the disagreement became more pronounced at higher flow velocities possibly owing to the formation of a secondary flow caused by centrifugal forces.

SYMBOLS

A o, A 1i A 2 -constants defined by Eq . (30) A 3(0), A 4(r), A S (0) -functions defined by Eq . ( ) B constant defined by Eq. (33) C salt concentration, kg equiv/m 3 CD *(Y) -average salt concentration in the dialysate channel at the sweeping front Y, kg equiv/m 3 c dimensionless concentration, C/COD Co, Cn -constants in Fourier series