Motion and interaction of in-line bubbles in quiescent non-aqueous solutions of hydrocarbon resin

Hydrocarbon resin (HR) is an essential fine chemical. The preparation and application process of HR involves lots of gas–liquid heterogeneous reactions, and the bubbly flow behavior influences them significantly. Using high-speed photography and digital image processing techniques, the motion and interaction of in-line bubbles in non-aqueous solutions of HR are examined in this article. The results show a critical gas flow rate that can change the bubbling regime. It can be observed that viscosity features prominently in changing the shape of bubbles and their motion. As the viscosity increases, the bubbles are more prone to coalescence, and the bubble coalescence process gradually changes from connected slip-rising coalescence to connected-rising coalescence. The viscosity transition region between non-coalescent and coalescent systems in non-aqueous solutions of HR occurs at 3.6–9.2 mPa·s. Further, a force analysis shows that in paired bubbles, the leading bubble can be viewed as an individual bubble unaffected by trailing bubble before the two bubbles collide, but in the wake of the leading bubble, the drag force on the trailing bubble decreases and the added mass force increases.