Experimental study on the dynamics and mass transfer of CO2 bubbles rising in viscoelastic fluids.

Abstract Single CO2 bubbles rising in quiescent viscoelastic polyacrylamide (PAA) aqueous solutions of different weight percentages (wt. %) were studied to obtain insight into the impact of fluid elasticity on the rising dynamics of dissolving bubbles. A random abrupt fall and rise in velocity was observed as the bubble velocity gradually and progressively decreased throughout the journey. This is the first time this observation is reported. In the most viscoelastic medium in which this phenomenon occurred, CO2 bubbles decreased in diameter by at least 20% over 1m of height. Mass transfer analysis of the system indicated significant reduction of mass transfer coefficient with increase in weight percentage of the polymer solution. Comparison of experimental mass transfer coefficients with predictions for mobile and immobile gas-liquid interfaces were consistent with theoretical predictions from Higbie's and Frossling's equations respectively. The rising dynamics was correlated using dimensional analysis, and the prediction by a developed empirical correlation considering the combined effect of fluid elasticity and shear-thinning property showed a satisfactory agreement with experimental data in all liquids studied.