Abstract :
Concerning the transfer of energy from the mechanical aerator to the liquid in an aeration tank, new relationships between the oxygen mass transfer rate, the aerator diameter, its rotational velocity and the volume of the aerated liquid, have been proposed by the author of this paper. Therefore, according to the power consumption of the aerator, three parameters characterizing the oxygen mass transfer process have been defined by the author. These are the active volume, the energy transfer area and the mass transfer area. Meanwhile, an ideal mechanical aerator has been defined as a hypothetical aerator for which the volume generated by the spinning of the aerator is equal to the active volume corresponding to the potential energy transferred by the aerator. The new relationships between the oxygen mass transfer rate, the aerator diameter, its rotational velocity and the aerated volume were determined by the author for both ideal aerators and the real aerators used in full scale processes. It has been proven, on the basis of these relationships, that for an aerator of given geometrical shape there is both a unique rotational velocity and aerated volume for which the transfer efficiency is optimum. The correlation between the experimental results and theoretical data, generated using specific mathematical formulas which express the dependence of the oxygen mass transfer rate on the power consumption, has been established. New relationships are proposed for scaling.
