Aeration Cost of Propeller-Aspirator Pump Aerator at Optimum Geometric and Dynamic Conditions

Aeration test was conducted in a brick masonry tank of dimension 5 m 3 m 1.5 m to evaluate the optimum geometric condition of Propeller -aspirator pump aerator, i.e., positional angle of propeller shaft (a) and dynamic condition, i.e., rotational speeds of propeller shaft (N) and submergence depth of propeller shaft (d). The results indicated a maximum SAE at a = 75 degree . Keeping the geometric condition constant (a = 75 degree ), aeration experiments were further conducted at different rotational speeds of propeller shaft, N ranging from 1420 to 2840 rpm with an interval of 355 rpm and different values of submergence depth, d from 140 to 460 mm with an interval of 80 mm to evaluate the effect of dynamic conditions on aeration characteristics. Non-dimensional numbers related to standard aeration efficiency (SAE) and wire power (P) termed as E and Ne respectively, were introduced. It was found that E and Ne could be well correlated with Froude number (Fr) and Reynolds number (Re) respectively. Power consumption and Standard oxygen transfer rate (SOTR) of Propeller-aspirator pump aerator were evaluated at optimum geometric condition (a = 75 degree ) and optimum dynamic conditions (N = 2840 rpm and d = 0.14 m). Further, aeration cost (Rs. 37.73 / kg O2) of propeller-aspirator pump aerator was estimated for tank volume of 100 m3.