ISSN:
1572-8838
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Chemie und Pharmazie
,
Elektrotechnik, Elektronik, Nachrichtentechnik
Notizen:
Abstract Mixing is investigated in three laminar radial flow cells (capillary gap cell (stationary discs), pump cell (one disc spinning) and the rotating electrolyser (co-rotating discs)) using numerical and semianalytical methods for inert tracer transport. Results are compared to existing data. Mixing in the three cells is modelled using finite element techniques applied to convection-dominated inert tracer transport. For the capillary gap cell modes of tracer tagging and detection are commented on with respect to which type provides the correct representation of the residence time distribution. The extent of cross-gap communication, from anode to cathode, is quantified and compared to that observed in the other radial cell designs. Two semi-analytical solutions (convection only, Taylor diffusion) are derived for inert tracer transport in this configuration and are compared to the detailed numerical results. Convection only is relevant fort d/t c ratios of greater than 100 and the Taylor diffusion model applies fort d/t c ratios of about 0.10 and only beyond a critical radius defined herein. Pump cell (PC) mixing is modelled using finite element techniques for the tracer, the velocity field being provided by a semi-analytical solution. Mixing is quantified in this cell and cross-gap communication evaluated. The large axial velocities provide for significant cross-gap mixing. The rotating electrolyser is modelled and the efficiency of separation of catholyte/anolyte streams is observed to be determined by Taylor number (Taylor number (α) — ratio of half-gap width divided by theoretical boundary layer thickness). The superiority of separation in this cell is quantified by definition of the zeroth wall moment and comparison with the other two radial cells. For the example modelled, cross-gap communication was less than half that of the other cells.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF01007932
