Quantifying the relationship between bubble surface area and gas evolution rate

Abstract

Bubbling is a common phenomenon in nearly all fields of engineering. For example, in gas/liquid separations, the mass transfer rate of gas exiting the liquid is affected by the bubbling of the system, and ultimately the area available for mass transfer. This study is aimed at understanding the influence of bubble surface area on gas evolution (mass transfer) behavior in liquids. Bubbling was characterized by three regimes: low bubbling, transitional bubbling, and high bubbling in the liquid during the mass transfer process. An optical technique was designed to determine bubble diameters using an HD camera. Observations of an increase in bubble surface area were directly correlated to an increase in the mass transfer rate. In addition, liquid viscosity was observed to play a major role in the bubbling behavior. Fluids with viscosity lower than 96 cP did not experience bubbling irrespective of mixing speeds during the gas evolution process. With an increase in the fluid viscosity, the ease of bubbling increased. Bubbling was not seen during the gas absorption process irrespective of fluid viscosity, indicating the bubbling phenomenon is a result of the gas evolution process.