Measurement of Bubble Size Distribution in High Pressure Bubble Columns Using Borescope Imaging Technique

Size distribution of the discrete phase objects such as particles, bubbles, and droplets can enhance the understanding of mixing, heat and mass transfer properties as well as the complex phase interactions etc in multiphase flow systems. Numerous techniques including laser Doppler anemometry, tomography, intrusive probe measurement, and direct imaging have already been developed in order to determine the size distributions. Direct imaging is preferred over other techniques to give direct measurement of size and shape. However, the unknown object location prevents the determination of a correct calibration scale for accurate size measurement from captured images. A statistical method is developed in our previous study to convert the object size distribution obtained from a common calibration scale into the actual size distribution.

In the current study, the effect of object concentration on the horizontal viewable distance is determined. The information will be applied to the statistical model developed previously to refine the size distribution measured at high object concentration conditions. The methodology is then applied to determine the bubble size distribution in a bubble column under both homogeneous and heterogeneous bubbling flow regimes at pressures up to 10 bar.