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.
