A comparative study of bubble rise phenomena in water and low concentration polymer solutions

Abstract

Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.Bubbles are used in polymer, metallurgy, biotechnology and especially in process industries for improving the heat and mass transfer from a dispersed gaseous phase to viscous liquid phase. A comparative study of the bubble rise characteristics in water and a few selected low concentration polymer solutions is presented in this paper. The characteristics, namely, the bubble velocity, the bubble trajectory, the bubble volume and the drag relationship are investigated. The experiments were conducted in 125 mm cylindrical column at liquid heights of 1 m, 1.2 m, 1.4 m and 1.6 m by introducing different bubble volumes (from 0.1 mL to 5.0 mL ) corresponding to each height. The bubble rise velocity and trajectory were measured using a combination of non-intrusive (high speed photographic) method and digital image processing. The parameters that significantly affect the rise of air bubble are identified. The effect of different bubble volumes and liquid heights on the bubble rise velocity and bubble trajectory are analysed and discussed. The correlation between the Reynolds number and the drag coefficient is developed and presented. The results of this study are compared with the results of other analytical and experimental studies available in the literature.