This study is on the performance characteristics of bubble pump with vertical pipe of different lengths. For the experimental facilities composed of electrical heater used for providing heat source to generate bubble, a vertical tube with Ø4mm diameter, length of 200mm, 300mm, 400mm and 500mm. Storage tank with capacity was of 40 L containing a heat exchanger. The separator and condenser of the air bubble pump were installed separately. The results obtained from this experiment are as follows: there were a few variations of values of temperatures according to vertical pipe lengths of the bubble pump. The mass flow rate was increased by 0.17g/s when it was short as 200㎜ long pipe. But when vertical pipe length was 500㎜, it reached the normal temperature quickly because the slug flow occurred in this case at initial stage. Consequently, it was found that 500㎜ of the vertical pipe length was optimum for best performance of bubble pump.

The mechanism of micro-bubble generation with a pump is not clarified yet, so the design of water treatment systems with a micro-bubble generating pump is based on trial and error methods. This study tried to explain clearly quantitative relationships of experimental micro-bubble concentration (Cair) of continuous operation tests with a micro-bubble generating pump and theoretical air solubility. Operation parameters for the tests were discharge pressure (Pg), water (Qw0) and air (q0) flow rates, orifice diameter (DO), and retention time (t). The experimental micro-bubble concentrations (Cair) at 4.8 atm of discharge pressure (Pg) were in the range of 21.04 to 25.29 mL/L. When the retention time (t) by changing the pipe line length (LP) increased from 1.22 to 6.77s, the experimental micro-bubble concentrations (Cair) increased from 25.86 to 30.78 mL air/L water linearly. The dissolved and dispersed micro-bubble concentrations (Cair) are approximately 4 times more than the theoretical air solubility.

The goal of this study was to evaluate micro-bubble concentration (Cair) in water by air/water ratio (A/W ratio) with a micro-bubble generating pump. The estimation of micro-bubble concentration is based on the balance of inlet/outlet air and water flow rate. On net A/W ratio to be generated micro-bubble, we found that the obtained the Cair are shown as a function of discharge pressure (Pg) of the micro-bubble generating pump. The correlation of the Cair and the Pg(Cair =3.261Pg-1.754) was adequately described by the least square methods with a high correlation coefficient (r = 0.9459) and calculated values fit the experimental data quite well. The Cair was lower than theoretical dissolved air concentration (Caq) calculated by Henry’s law. The Cair for being operated the micro-bubble generating pump was 6.75 – 39.53 mL/L, however, we found that the optimum of the Cair to generate micro-bubble was the range from 10 to 12 mL/L.