Abstract
In-line defoaming of highly viscous fluids is one of the remaining challenges for their industrial use. To overcome the problem of air bubbles in such fluids, the pressure oscillating defoaming for shear-thinning fluids has been developed. The key of this method is to intentionally apply pressure oscillation to the fluid containing a bubble, so as to produce continuous strong local flow around the alternately contracting/expanding bubble, where shear-viscosity has been lowered. Based on our success using this technique to cause bubbles in a quartz cell to rise faster, we applied it to a branched flow channel filled with viscoelastic fluid of zero shear viscosity 90 Pa⋅s for the purpose of developing an in-line defoaming system. In this study, motions of bubbles in a revised flow channel filled with higher-viscosity 220 Pa⋅s liquid were investigated experimentally. In addition, a small air cavity on the upper side of the flow channel was introduced as a bubble trap to improve the defoaming perfor mance. We studied the effect of the trap position on defoaming performance.
