Removal of gas bubbles from highly viscous non-Newtonian fluids using controlled vibration

Formation of gas bubbles is normal and practically inevitable when fluids are agitated or flow in open containers. The unwanted gas bubbles will damage the product quality, and they are very difficult to be removed from highly viscous fluids. In this paper, the effectiveness of vibration degassing for highly viscous non-Newtonian fluids is investigated using volume of fluid (VOF) model coupled with continuous surface force (CSF) model. The motions of gas bubbles in liquid under vibration are simulated and the effects of various rheological parameters as well as vibration parameters on the degassing rate are studied. The results show that the shear thinning (or thickening) induced by vibration is responsible for the enhancement (or retardation) of degassing rate for non-Newtonian fluids. The more pronounced the non-Newtonian behaviors of fluids are, the greater the effects of vibration on the degassing rate are. The degassing rate is governed by the vibration amplitude and frequency of vibration. However, high frequency or large amplitude vibration may intensify air entrapment and bring new gas bubbles into fluids. Thus, the feasible region of vibration degassing in which the vibration frequency and amplitude don't cause new gas bubbles are further studied. The vibration degassing technology has the added advantage that it does not use intrusive devices to container, nor does it limit the container structure or shape, and thus will find wide applications in laboratory and industrial fields. (C) 2018 Elsevier Ltd. All rights reserved.