Scaling-Up the Geometrically Similar Unbaffled Circular Tank Surface Aerators

Present investigation is concerned with the development of scale-up equations for oxygen transfer coefficient, k and power number, $P_O$, for unbaffled circular tank surface aerators under geometrically similar conditions for the purpose of designing of energy efficient aerators. It has been found that k and $P_O$ for the present aerators are uniquely related to a parameter, X, governing the theoretical power per unit volume and is defined as $Fr^{4/3}$ $Re^{1/3}$, where Fr and Re are impellers’ Froude and Reynolds number respectively. Empirical correlations between k and X as well as $P_O$ with X are developed for the range of experiments conducted. Based on such experimental results, procedures to design energy efficient aeration systems have been demonstrated and found that smaller sized aerators are more energy conservative and economical when compared to bigger sized tanks, while aerating the same volume of water, by maintaining the same input power to the tanks irrespective of their size. It has been also demonstrated that energy can be saved substantially if the aeration tanks run at higher input power