Effect of speed on Taiwanese paddlewheel aeration

Abstract

Aerators are generally used in Australian aquaculture ponds day and night at full speed without regulation. This situation is untenable in view of climate change, as energy conservation becomes an essential issue for all industries, including aquaculture. Variable speed performance curves were developed for the paddlewheel aerators that have been employed on Australian marine aquaculture ponds so that speed may be actively adjusted to match pond water quality requirements. Results show that speed of rotation is a significant factor effecting the performance of a paddlewheel aerator. Of particular note was the observation of backsplashing when kinetic energy (pumping head) was greater than the radius of a paddlewheel. The process of backsplashing is readily identified when whitewater is seen flying above a paddlewheel. It is hypothesised that backsplashing dilutes the oxygen-starved water entering a paddlewheel, thereby degrading the operational efficiency. Backsplash breakpoint speed is related to paddlewheel diameter. Aerator users can reduce backsplash by changing mechanical gearboxes or using a variable frequency drive (VFD inverter).