الفهرس 
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Abstract
The present work aims to evaluate the performance of a vertical array of closely spaced horizontal cylinders in building catalytic and electrochemical reactors used to conduct diffusion controlled reactions encountered in wastewater treatment. This new geometry offers the possibility of using the eternal surface as a turbulence promoter for the diffusion controlled reaction, while the inner surface acts as a heat exchanger to control the reactor temperature. The mass transfer behaviour of the cylinder array was studied by an electrochemical technique which involved measuring the limiting current of the cathodic reduction of K3Pe(CN)6 under the following hydrodynamic conditions:- (i) single phase flow, (ii) gas sparging and (iii) cocurent two phase (gas-liquid) flow using an inert gas (air). The effect of the following variables on the rate of mass transfer was studies:-
(1) Cylinder diameter.
(2) Active height of vertical array.
(3) Physical properties of the solution e.g. (solution viscosity, solution density and
the diffusivity of the electro active ion).
(4) Solution flow rate.
(5) Gas (air) flow rate.
The study has revealed the following results:-
(1) The single phase flow, data show that the mass transfer coefficient increases
with increasing the liquid flow rate. The mass transfer coefficient does not
depend on neither cylinder diameter nor the height of the array.
(2) The gas sparging data show that, the rate of mass transfer increases with
increasing gas superficial velocity up to certain limit and then remains
constant with further increase in gas flow rate.