Experimental study of interfacial mass transfer from single CO₂ bubbles ascending in stagnant water

The study focuses on the interfacial mass transfer from single CO2 bubbles with initial diameter in the range of 0.7 - 3.0 mm in a vertical column with stagnant deionized water. The objective is to enhance the understanding of the intricate phenomena involved in interfacial mass transfer by examining the individual effects of the liquidside mass transfer coefficient and the bubble size. The liquid -side mass transfer coefficient is found in this study to be influenced by both the initial bubble diameter and on the bubble age, i.e., the time the bubble is exposed to the liquid influences the obtained liquid -side mass transfer coefficient. Existing literature suggests that bubbles of diameter < 2 -3 mm behave as rigid spheres with immobile interface and reduced internal gas circulation, which negatively impact the interfacial mass transfer. The results obtained from this study show that the maximum value of the liquid -side mass transfer coefficient is obtained for bubbles of diameter 2.1 - 2.3 mm. For bubbles with a mean diameter <= 1.4 mm, the mean liquid -side mass transfer coefficient decreases with decreasing mean bubble diameter. A Lagrangian model description is used with various correlations for the liquid -side mass transfer coefficients to perform numerical simulations of the change in bubble volume during the bubble rise. The existing correlations for the liquid -side mass transfer coefficient give very different simulation results and fail to accurately capture the transient evolution of the bubble as it exposes to the mass transfer phenomenon and hydrostatic pressure gradient. The correlation for the liquid -side mass transfer coefficient proposed by Clift et al. (1978) is modified in this work, and the experimentally obtained data are well predicted by the new modified correlation.