Influence of Twisted Tape Ratio on Oxygen Transfer Efficiency in an Ejector-Based Aeration System
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Abstract
Although ejector aeration offers strong air entrainment and mixing capability, quantitative evidence remains limited regarding how the twisted-tape twist ratio (y/w) in the mixing chamber affects the standard volumetric oxygen transfer coefficient at 20 °C (KLa(20)) and oxygen transfer efficiency per unit energy input (OTE). This study therefore investigated the effects of Reynolds number (Re) and y/w on the oxygen transfer performance of an ejector -based aeration system. Experiments were conducted in a 100-L water tank over Re = 17,000 –25,000 and y/w = 4.21, 5.62, 8.43, and 16.85, and performance was evaluated using KLa(20) and OTE. The results showed that KLa(20) increased significantly with increasing Re, with a notably steeper increase when y/w was below 6, indicating enhanced mixing and mass transfer in the mixing chamber. In contrast, OTE tended to decrease as Re increased; however, OTE improved markedly at lower y/w values, particularly at y/w = 4.21 and 5.62, which provided the best overall performance. These findings demonstrate that an appropriately designed internal structure can enhance both oxygen transfer and energy efficiency, supporting practical implementation in wastewater treatment and aquaculture applications requiring high performance with reduced energy demand.
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