A novel correlation of bubble aspect ratio through analysis of gas/shear-thinning liquid two-phase flow in a bubble column.

• The bubble shape variation in the shear-thinning fluid with bubble swarms is investigated using high-speed imaging. • Influence of superficial gas velocity and solution concentration over the bubble shape is systemically evaluated. • The relationship between the bubble aspect ratio and equivalent diameter is revealed. • The novel aspect ratio prediction correlations based on dimensionless group Re · Eo are proposed for oblate and prolate spherical bubbles, respectively. Gas/shear-thinning liquid two-phase flow is often involved in the petroleum, chemical, and food industries, with the bubble shape playing a vital role in the theoretical analysis and numerical simulation of the flow. This study investigates the bubble shape variation in a shear-thinning liquid (carboxymethyl cellulose sodium solution) under the bubble swarm condition using high-speed imaging and a bubble recognition algorithm. The results show that trailing bubbles accelerate as they rise along the flow path of leading bubbles. During acceleration, the bubbles are subjected to lateral forces that cause them to deform from an oblate spheroid to a prolate spheroid. The effect of the shear-thinning property is enhanced owing to the increased superficial gas velocity and solution concentration, leading to an increase in the number of prolate spherical bubbles. Considering the significant difference in energy transfer in the flow fields around oblate and prolate particles, new aspect ratio correlations were developed for the two shapes based on the correlations of Re · Eo derived from the Newtonian fluid case. Compared to the previous correlation developed by assuming that the two shapes have the same aspect ratio, the proposed method significantly improves the prediction accuracy of the bubble aspect ratio for a shear-thinning fluid case. [ABSTRACT FROM AUTHOR]