CFD-Based Scale-Up Analysis of Airlift Photobioreactors: Effects of Superficial Gas Velocity on Hydrodynamics and Mass Transfer

Document Type : Regular Article

Authors

1 SR.C., Islamic Azad University

2 University of Tehran

3 TU Wien

10.22034/ijche.2026.590277.1603
Abstract
Maintaining a constant superficial gas velocity (Usg) is the most common criterion for scaling aerated photobioreactors, yet whether it preserves gas–liquid hydrodynamics is rarely tested directly. Euler–Euler CFD was used to characterize two baffled airlift reactors, a 9.7 L laboratory unit and a 106 L scaled-up unit, over Usg = 0.025–0.10 m·s⁻¹, evaluating gas holdup, gas-phase velocity, and the volumetric mass transfer coefficient (kLa) alongside Reynolds number, Froude number, and power input per unit volume (P/V). Across this range, gas holdup rose 2.4–2.6-fold and kLa rose 1.3–1.6-fold in both reactors, but mean gas velocity increased more in the larger unit (1.4-fold vs. 1.1-fold). Extended-range simulations of the large reactor showed continued but progressively less proportional gains. Froude number was not conserved across scales, and P/V remained consistently higher in the larger reactor. These results show that Usg alone is an insufficient scale-up criterion, gas holdup, kLa, Froude number, and P/V should be evaluated jointly.

Keywords

Subjects

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Articles in Press, Accepted Manuscript
Available Online from 31 July 2026