A phenomenological study of bubbles from the venturi pipe microbubble generator without and with guitar string insertion

The phenomena of bubble formation from the venturi pipe microbubble generator were investigated. The air hole sizes were varied at 1, 0.5, and 0.3 mm while the volumetric flow rates were set at 4, 5, 6, 7, and 8 LPM. Insertion of a guitar string with a diameter of 0.2 mm into the 0.5 mm air hole size was also performed to examine its effect. The simulation of the bubble shrinkage process in water (sizes of 25, 50, 75, and 100 μm) was held with and without saturated nitrogen at 0.25, 0.5, 0.75, 0.875, and 1 atm. The experiment shows that average bubble sizes for air hole sizes of 1, 0.5, and 0.3 mm are 1.37, 1.40, and 1.09 mm, respectively. The flow rate alteration significantly affects the bubble sizes for air hole sizes of 0.5 and 0.3 mm but is not meaningful for 1 mm. In addition, the guitar string insertion also produces spherical bubbles with a size of 1.33 mm for deep depth location. Moreover, simulation results prove that smaller bubble sizes lead to prolonged shrinkage time and a greater mass transfer coefficient in the liquid phase with and without saturated nitrogen.