Premium
Airlift bioreactors: Analysis of local two‐phase hydrodynamics
Author(s) -
Young Mark A.,
Carbonell Ruben G.,
Ollis David F.
Publication year - 1991
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690370311
Subject(s) - airlift , mechanics , two phase flow , sparging , slug flow , draft tube , flow (mathematics) , fluid dynamics , mass transfer , volumetric flow rate , flow conditions , materials science , bioreactor , chemistry , physics , organic chemistry
Local two‐phase flow measurements were obtained in a pilot‐scale, external‐loop airlift bioreactor using hot‐film anemometry and resistivity probe techniques. The radial dependence of both gas and liquid velocities and of the void fraction was substantial. Developing flow effects were pronounced, as evidenced by distinct changes in the radial profiles of fluid flow properties with axial position. For high gas flow rates, liquid acceleration effects near the sparger resulted in greatly reduced slip velocities in a substantial portion of the riser. A significant reduction in mass transfer may occur under such conditions. The point equations of continuity and motion were used to develop a differential, two‐fluid model for two‐phase flow in airlift risers. The only empirical parameters in the model represent frictional effects. The developing two‐phase flow characteristic of airlift risers was observed to create significantly higher frictional effects at the wall than is routinely observed for fully‐developed flow. Model predictions were compared to our own experimental results as well as those of Merchuk and Stein (1981). Agreement between the predicted and measured values was typically within 10% for both cases.