الفهرس 
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Abstract
The Mass transport behavior of a new heterogeneous stirred tank reactor with a reaction surface composed of a helical coil integrated with the reactor cylindrical wall was studied by a technique which includes measuring the rate of the Dissolution of copper in acidified dichromate, controlled by diffusion. The studied variables were helical coil tube diameter (d), helical coil pitch (p), impeller rotation speed, impeller geometry (axial and radial), the presence of baffles and the solution physical properties. The presence of the helical coil in the immediate vicinity of the reactor wall enhanced the rate of mass transfer by a factor ranging from 1.01 to 2.48 and the volumetric mass transfer coefficient (KA) by a factor ranging from 2.675 to 4.55 depending on the operating conditions. The average mass transfer coefficient was found to increase with decreasing coil tube diameter, coil pitch was found to have a little effect on the average mass transfer coefficient. Radial flow turbine produced mass transport rate higher than axial flow turbine. Baffled reactor produces higher mass transport rates than unbaffled reactors. The unbaffled reactor data with axial flow turbine were correlated by the equation: Sh = 0.614 Sc 0.33 Re 0.63 (p/d) 0.3 While the data for unbaffled reactor with radial flow turbine were correlated by the equation: Sh = 0.3581 Sc 0.33 Re 0.7 (p/d) 0.24 The importance of the multirole of the helical coil as a catalyst support along with the tank wall, cooler and turbulence promoter in the design of stirred tank catalytic Reactor suited for exothermic reactions regulated by diffusion which need rapid cooling such as biocatalytic reactions was highlighted, also the merits of the suggested reactor compared to the conventional stirred slurry reactor were pointed out. The use of the present reactor as an efficient heat exchanger-reactor in case of highly exothermic liquid-liquid reactions was also noted. Drag reducing polymer was found to decrease the rate of mass transfer at the vessel wall by an amount ranging from 2.2 to 38.5 % depending on impeller rotation speed, polymer concentration and impeller geometry. Implication of the present results for stirred tank biochemical reactors which use drag reducing polymer to control solution viscosity and decrease the shear stress between the moving solution and the vessel wall in order to protect immobilized enzyme or cells fixed to the wall against mechanical damage were discussed. The present results would help in determining the economic feasibility of using drag reducing polymers in operating biochemical stirred tank reactors where the beneficial effects of reducing the shear stress at the wall and the saving in mechanical power consumption should be weighed against the adverse effects of the polymer such as the decrease in the rate of mass transfer controlled reactions and the rate of heat transfer at the vessel wall. The present reactor can find applications in many fields such as pharmaceuticals, fine chemical production and production of petrochemicals via immobilized enzyme or cell catalyzed biochemical reactions.