Experimental Investigation and Correlation of the Effect of Carbon Nanotubes on Bubble Column Fluid Dynamics: Gas Holdup, Flow Regime Transition, Bubble Size and Bubble Rise Velocity

Abstract

The gas holdup is an important parameter in industrial applications for design and operation of bubble columns as well as for calculation of the pressure gradient in fluid flow through pipelines. This study presents new experimental gas holdup data by using kerosene as the liquid phase, CO2 and N2 as the gas phase, and multiwall carbon nanotubes (one of them without functionalized group and another with carboxyl functionalized group) as the solid phase. Results show that the un-functionalized multiwall carbon nanotube (MCNT) decreases the gas holdup until the concentration of 17 ppm and after that increasing the concentration of nanoparticle increases the gas holdup. The maximum gas holdup for kerosene/CO2 and kerosene/N2 systems was 0.3 and 0.29, respectively. The MCNT at 17 ppm concentration decreased the maximum gas holdup to 0.22 and 0.25 for kerosene/CO2 and kerosene/N2 systems. Results also show that the multiwall carbon nanotube with carboxyl functionalized group (MCCNT) increases the gas holdup until the concentration of 17 ppm and after that increasing the concentration of nanoparticle decreases the gas holdup. The MCCNT at 17 ppm concentration increases the maximum gas holdup to 0.37 and 0.33 for kerosene/CO2 and kerosene/N2 systems. The analysis of transition point of flow from homogeneous regime (bubbly flow regime) to heterogeneous regime shows that the transition point is not significantly affected by the addition of both types of nanoparticles; however, the type of gas has a strong effect on the transition point. Two correlations were also developed for prediction of experimental gas holdup data for two types of nanoparticles in both homogeneous and heterogeneous regimes and analysis of predicted data showed the acceptable accuracy of the developed correlations.