Experimental Investigation of Bubble Dynamics Using Four Point Optical Probe
The knowledge of bubble properties, including gas holdup, bubble velocity, bubble distribution and specific interfacial area, is of considerable importance for efficient design and sacle-up of bubble columns. However, the measurement of these properties has always been a challenging problem and the experimental data is limited in the literature. In this research work, bubble dynamics in a 10 cm column has been investigated using Four Point Optical Probe. Experiments with air-water system were performed at CREL, USA. Study was conducted for range of superficial gas velocity (1–18 cm/s) covering both bubbly and churn-turbulent regimes. Bubble properties at 5 different radial positions were measured at a fully developed axial position using a constant L/D of 5.5.
Analysis of overall gas holdup has depicted an increasing behaviour with increase in ug. A transition from bubbly to churn-turbulent regime was noticed at Ug ≥ 5 cm/s. An increase in overall gas holdup from 2 – 25 % was obtained for the operating range of gas velocity. Radial profiles of bubble properties (local gas holdup, specific interfacial area, bubble velocity and bubble frequency) have shown an increasing behaviour with increase in ug. These profiles were relatively flat in the bubbly regime. With increase in ug an increasing trend in parabolic pattern of the plot was evident in all cases. Similarities among radial profiles have demonstrated a strong correlation in bubble properties. In summary, the bubble properties obtained in present study can give a deeper understanding of the hydrodynamics in bubble columns.