Effect of spheroid bubble interface contamination on gas-liquid mass transfer at intermediate Reynolds numbers: From DNS to Sherwood numbers

Gas-liquid mass transfer from spherical bubbles is studied by DNS for various Reynolds numbers (1 <= Re <= 300), Schmidt numbers (1 <= Sc <= 500) and bubble surface contamination degrees (0 degrees <= theta(cap) <= 180 degrees). Computed separation angles, drag coefficients and average Sherwood numbers for both clean and fully contaminated bubbles are favorably compared to literature. For partially contaminated bubbles, a correlation giving the separation angle versus Re and Ocap is proposed. Local Sherwood numbers along the bubble interface shows a transition between clean and contaminated zones closed to the separation angle. At low Re, for theta(cap) < 40 degrees, mass transfer of the contaminated bubble can be estimated by correlations for spherical solid particles, meanwhile for theta(cap) > 160 degrees, bubbles can be assimilated to clean bubbles. For intermediate contamination levels, a normalized Sherwood number Sh* from the drag Sadhal(1983) model can be used. For intermediate Re and high Sc; Sh* converges to a function well correlated to the normalized drag coefficient C*(D) bySh*(lower) = 1- (1-(C*(D))(2))(0:5). (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

Gas-liquid mass transfer from spherical bubbles was studied by DNS for various Reynolds numbers, Schmidt numbers, and bubble surface contamination degrees. The results were compared favorably to literature, and correlations for separation angles and mass transfer were proposed for different contamination levels.