https://orcid.org/0000-0001-8301-4923
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ABSTRACT
An electrochemical method (limiting current technique) was used to obtain mass transfer coefficient (kL) in a flow reactor in which the coaxial inner cylindrical rod was rotated at different revolutions per minute (rpm). The effect of liquid velocity, rpm and rod diameter on the liquid-wall mass transfer coefficient was investigated. It was observed that at any given rpm, the kL increased with the liquid velocity. Rotation of the central rod was found to further augment the coefficient. Augmentations were found to be more significant at small liquid velocities. The effect of central (annular) rod diameter was also studied and the kL data were correlated using Colburn j-factor format.
GRAPHICAL ABSTRACT
Acknowledgement
The authors express their thanks to Mr Ch. Siva Rama Krishna for his help during experimentation.
Disclosure statement
No potential conflict of interest was reported by the author(s).
| Nomenclature | ||
| A | = | surface area of the point electrodes, m2 |
| Cb | = | concentration of the ferricyanide ion, kmol/m3 |
| Dc | = | inner diameter of the test cell, m |
| Dr | = | diameter of the inner annular rod, m |
| dt | = | diameter of the tangential inlet, m. |
| F | = | Faraday constant, 96,500 Coulombs/mol of electrons |
| i | = | limiting current, amperes |
| kL | = | mass transfer coefficient, m/s |
| N | = | rpm of the central annular rod |
| n | = | number of electrons exchanged in the electrode reactions |
| Rc | = | inner radius of the outer cylinder of the test section, m. |
| Rr | = | radius of the annular rod, m |
| Va | = | axial flow velocity of the electrolyte in the annular test section, m/s |
| Vr | = | linear velocity of the rotating central annular rod, m/s |
| Greek symbols | ||
| µ | = | viscosity, Pa s |
| ρ | = | density of the electrolyte, kg/m3 |
| Dimensional groups | ||
| jd | = | mass transfer factor |
| Rea | = | Reynolds number based on the axial flow of the electrolyte |
| Rer | = | rotational Reynolds number based on the rpm of the central annular rod |
| Sc | = | Schmidt Number |