Measurement of interfacial mass transfer of single bubbles rising in homogeneous turbulence

Abstract

Accurate quantification of the mass transfer coefficient kl of bubbles under high Reynolds number conditions has been in desperate need for decades to provide insights into its fundamental physics and reach a general mass transfer model. In this paper, a state-of-the-art SI-LIF technique is developed to quantify kl indirectly based on the law of conservation of mass. The reconstruction algorithms of the required physical quantities are validated numerically, suggesting an overall uncertainty of less than ± 5 % in the estimation of kl. We perform mass transfer experiments of single oxygen bubbles with deq = 1.5 mm rising in both quiescent water and homogeneous turbulence, with turbulent Reynolds number ReT ranging from 0 to 1114. The measured kl under turbulent conditions are independent of ReT, and all collapse to the analytical solution of potential flow approximation, revealing that the flow in the immediate vicinity of the bubble interface remains undisturbed by the fluctuating liquid motions across all the turbulence settings examined in this paper.