Influence of paddlewheel geometry on hydrodynamic performance and energy consumption in microalgae cultivations in...

Microalgae cultivation is a field with significant potential across various industries, such as pharmaceuticals, food, cosmetics, and energy. Aiming to optimize the geometric parameters of a paddlewheel agitation system through computational fluid dynamics (CFD) and experimental validation, an investigation was conducted involving different rotation speeds, blade pitch angles, and the number of blades on a paddlewheel within a microalgae cultivation tank. The results revealed paddlewheels with 90° inclined blades exhibited higher average flow velocities. Regarding the vertical mixing index, the 8-blade paddlewheels demonstrated inferior performance compared to systems with four and six blades. A pitch angle of 60° minimized power consumption. The optimal configuration found was a 60°-angled 4-blade paddlewheel, operating at a rotation speed of 19 rpm, yielding the highest mixing performance index value at 46.12 W^-1. The straight blades operated at 13 rpm could not sustain microalgae suspension. For 60° inclined blades, all tested rotations achieved a high level of suspension.