Dynamics of gas-liquid flow in helical static mixer: An experimental and numerical study

Static mixer is an attractive alternative to conventional gas-liquid contactor, widely used for mixing and heat transfer between two fluids in various process applications. Knowledge on the limits of number and dimension of the static mixer element are important for packing optimization for desired mixing. The present work are designed to investigate the flow mixing pattern in a upward gas-liquid (air - water) flows in a column packed with helical static mixer both experimentally and numerically.
Experiments are carried out in a column of diameter (DT = 0.08 m) packed with helical static mixer (length 80 mm/ diameter 80 mm) using ultrafast electron beam X- ray tomography. The effect of number of static mixer element (3 – 9), liquid velocity (UL = 0.02 & 0.6 m/s), gas velocity (0.15 ≤ UG ≤ 0.6 m/s) on hydrodynamic parameters like gas holdup, bubble size distribution and pressure drop across the static mixer are studied.
Corresponding CFD simulations using the Euler-Euler model implemented in CFX 14 for some selective cases are done. The predicted axial and radial gas phase distribution considering different mono-dispersed bubbles classes (3, 5.8 and 8 mm) and poly-dispersed bubble classes are studied and validated against experimental results. The dependency of non-drag forces on the bubble size was considered. Consequently, the bubble size dependent effect of the non-drag forces on the flow and on the cross sectional gas volume fraction distribution are shown (see Fig. 1). The predicted axial gas volume fraction and velocity contour plots for different mono-dispersed bubbles classes within the helical static mixer are shown in Fig 2. The detailed effect of helical static mixer configuration and operating conditions on the predicted gas phase distribution & pressure drop and their validation with the measured results will be presented in our contribution.