Abstract
Rates of mass and heat transfer at the wall of a square agitated vessel fitted with semicylindrical turbulence promoters were measured using the electrochemical limiting diffusion current technique. Variables studied were promoter diameter, spacing between successive promoters, promoter orientation, impeller speed, and impeller geometry. The data were correlated by empirical dimensionless correlations. The promoters increased both the wall mass transfer coefficients and the volumetric mass transfer coefficients by factors ranging from 1.1 to 1.59 and 1.25 to 2.09, respectively depending on the operating conditions. Vertical turbulence promoters enhanced the rate of mass transfer by 3-29% more than the horizontal promoters. Confirming their economic worth, the turbulence promoters enhanced the mechanical energy utilization of the reactor up to 96%. Power consumption measurements revealed that the 45 impeller was more energy-efficient than the 90 degrees impeller up to 54%. Besides the novelty of using turbulence promoters in agitated vessels rather than their common use in flow ducts, the present study used chemically active promoters as a catalyst support in conducting diffusion-controlled catalytic reactions at the wall. The novelty of using chemically active promoters qualified the present promoters to outperform the chemically inert promoters in enhancing the mass and heat transfer rates. (C) 2021 THE AUTHORS. Published by Elsevier BV on behalf of Faculty of Engineering, Alexandria University.