Development of a fine bubble generator through the active control of gas chamber pressure

A unique device to generate fine bubbles (FBs) from nozzle under oscillatory flow inside the tube was proposed. The oscillatory flow was formed by controlling the pressure in the two gas chambers with two solenoid valves. The growing bubble was released from the top of the nozzle mainly by wall shear stress of the liquid through the tube in the pressurized state of gas chamber to form only micro bubbles (MBs) at a low frequency of pressure in gas chambers of less than 10 Hz for the one-hole nozzle with an inner diameter of 0.007 mm, since the wall shear stress of the liquid is kept constant. When the pressure in the two gas chambers was controlled independently using two solenoid valves (independent control mode), the monodispersity of MBs generated was high (the CV value was 8.5%). Additionally, the number density of MBs increased with A 21-hole nozzle with an inner diameter of 0.03 mm. These findings would serve as guidance for the design of gas-liquid contactors such as three-phase fixed bed reactors, where the monodispersity of bubbles is critical.