A Preliminary Study on Efficiency of Air-lift Upwelling

摘要

Upwelling of deep seawater using air-lift system to the region, where sunlight reaches, can produce the ocean farm since deep seawater contains high concentration of nutrient such as nitrogen and phosphorus. The efficiency of air-lift upwelling along a 300 mm diameter vertical pipe has been studied in this paper. Using a plexiglass pipe as the upwelling-pipe, a laboratory experiment was performed in a 4.5 m deep tank to obtain the flow rate ratio of water to gas. We also performed numerical experiments using commercial CFD software FLUENT 6.3 based on conditions of experiment. Both the experiment and simulation have shown promising results that the upwelling flow rate increased as the injection air flow rate increased, and there was a good lineal relationship between them in a certain range. The value of the lifting efficiency is about 2-3. Further work will have to determine the efficiency of air-lift upwelling under real ocean conditions and the minimum power of air pump required to sustain air-lift system.