Productivity Analysis in Tubular Photobioreactors Using a Dynamic Photosynthesis Model Coupled to Computational Fluid Dynamics Particle Tracking

Abstract

Tubular photobioreactors (TPBRs) are closed devices widely used for the mass culture of microalgae. TPBRs are supposed to be well-mixed, high-efficiency devices, but the influence of their fluid dynamics in photosynthesis has never been studied in detail. We use CFD coupled to a dynamic photosynthesis model to analyze the efficiency of the photosynthetic in the loop of TPBRs of different sizes (14, 24, 44, 64, and 84 mm) and circulation velocities (0.4 to 1 m s-1 ). The results show that only the smallest diameters cause enough radial mixing for a photosynthesis-enhancing light regime (integration factor Γ =0.199 for D=14 mm and v=1 m s-1 ) while high circulation velocities in larger diameters (up to 1 m s-1) do not enhance photosynthetic productivity. It is also explained how the characteristic frequency of the strain ( β ) is crucial for high productivity and that there is room for improvement.