Experimental Investigation of Venturi Microbubble Generation in a Viscous Fluid Using Temperature-Controlled Facility

Abstract

Venturi microbubble generators play a critical role across industries ranging from nuclear engineering to pharmaceutical and food processing, yet their performance in viscous fluids has not been well investigated. This experimental study examined bubble fragmentation in a viscous silicone oil using Venturi microbubble generators at controlled temperatures (120°F - 225°F) and varied flow rates (1.5 − 5.5 GPM). At a given flow rate, bubble size decreased with increased temperature due to lower fluid viscosity and surface tension. Bubble size also decreased with increasing flow rate owing to higher flow turbulence intensity in the diverging chamber. Among Venturi designs tested (7°, 15°, and 30° diverging half-angles), the 15° geometry provided optimal bubble fragmentation. Though the Reynolds number is traditionally used to characterize bubble fragmentation, the current studies with viscous liquids reveal that bubble fragmentation is best characterized by the Weber number, emphasizing flow energy and surface tension as the primary drivers of fragmentation over viscosity effects.