Influence of the angle and perimeter of contact of the blades in a horizontal axis aerator on the transfer of dissolved oxygen

Abstract

Dissolved oxygen (DO) is a fundamental parameter in water bodies that can be supplied using horizontal axis mechanical agitators. However, blade geometry and operating conditions can influence the process cost. In this work, it is studied the effect of the perimeter and angle of impact of the blades on the water in a prototype of horizontal axis mechanical aeration, starting from the DO transfer analysis. Measurements were made on anoxic water samples using two types of blades with the same area, varying their perimeter and angle of impact. Other parameters that influence the DO transfer process were controlled in this work. The results show the increase in the perimeter, and blade impact angle with the water body, which generates a reduction in the standard aeration efficiency (SAE) up to 30 % in the process. In that way, it is obtained the best results for the prototype Type II blades with a K_La value of 3.69 h^-1, and a SAE of 0.47 kgO₂∙kW^-1h^-1 when using an impact angle of 13.5 °. In general, the geometry of the blades is a fundamental design parameter, which influences the transfer of dissolved oxygen in the water. The results of this study can contribute to improving the efficiency of these mechanical systems, reducing the energy consumption associated with oxygenation processes.