Abstract
Pump efficiency of an air-lift column, which is used for aeration in eutropic lake or the like, was studied experimentally. It is considered that the pump head is a function of gas holdup and frictional head loss. However, the momentum head loss is not important for the pump head. The pump efficiency is equal to the ratio of the true mean water velocity and the true mean air velocity if the frictional loss is neglected. The efficiency increases with the decrease in the diameter of the hole of the air distributor, and with the increase of water flow rate in a large column. In a small column the frictional loss can not be neglected, and hence, the efficiency has a peak as the water flow rate increases. The flow pattern of the two-phase flow has a considerable effect upon the efficiency, which is highest in the bubbly flow region. The maximum pump efficiency due to an air-lift column in this experiment was about 80%, however we can expect a higher efficiency.
