An experimental study of bubble rise characteristics in non-Newtonian (power-law) fluids

Air bubbles are used in chemical, biochemical, environmental, food process such as sugar industries for improving the heat and mass transfer. In particular, the bubble rise characteristics in massecuite - a fluid made from sugar crystals and sugar syrup have a great influence on vacuum pan operation which is an important process for the production of raw sugar in sugar industries. An experimental study of the bubble rise characteristics in xanthan gum solutions, a non-Newtonian (Power-Law) massecuite equivalent fluid are presented in this paper. The main characteristics, i.e. the bubble velocity, the bubble trajectory, and the drag relationship were investigated as a function of volume of air bubbles. 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. A relationship between the Reynolds number and the drag coefficient is presented and discussed.