(768b) Multiphysics Simulation of Microalgae Growth in an Airlift Photobioreactor: Effect of Fluid Mixing and Shear Stress

Phototropic microalgae provide renewable feedstock for manufacture of biofuels, biochemicals, foods, nutrients, and pharmaceuticals. These organisms can be cultivated in photobioreactors with the aim of speeding their production. To reduce reactor design cost and improve reactor efficiency, it is necessary to simulate the key phenomena and mechanisms for biomass synthesis, as well as their mutual interactions, on reactor performance. Here, a multiphysics model has been developed with the objective to accurately simulate the effects of fluid mixing and shear stress on microalgal growth in an airlift photobioreactor. The model integrates multiphase flow dynamics, radiation transport, and algal growth kinetics using an Eulerian approach [1]. The multiphase computational fluid dynamic (CFD) model is first validated by comparing its predictions with corresponding experimental data. Subsequently, the CFD model is integrated incorporating sub-models for radiation transport and algal growth kinetics to predict reactor performance under various flow flow conditions. The simulations correctly predict the experimental trends that biomass productivity increases with increased rates of mixing, whereas it decreases with increases in shear stress. Lastly, we demonstrate the superiority of the Eulerian simulation approach by comparing its predictions not only with experimental results but by also comparing them to commonly used circulation cell and Lagrangian approaches [2].

[1] Gao, X., Kong, B. Vigil, R. D., 2017. Comprehensive computational model for combining fluid hydrodynamics, light transport and biomass growth in a Taylor vortex algal photobioreactor: Eulerian approach, Algal Research. 24, 1-8.

[2] Gao, X., Kong, B. Vigil, R. D., 2017. Comprehensive computational model for combining fluid hydrodynamics, light transport and biomass growth in a Taylor vortex algal photobioreactor: Lagrangian approach. Bioresource Technology. 224, 523-530.