CFD simulation for reduced energy costs in tubular photobioreactors using wall turbulence promoters

Tubular photobioreactors (PBR) have great potential for microalgae cultivation due to its high productivity compared with open ponds. However, the energy uptake for fluid circulation and mixing is significant, impacting the operation and production costs. In this work, we investigate by CFD simulation the effect of wall turbulence promoters, i.e. profiles at the inner tube wall, at low flow velocities (0.1-0.3 m/s). The use of these wall turbulence promoters is compared to the mixing behaviour in standard tubular PBRs at flow velocity of 0.5 m/s. It was found that the wall turbulence promoters have at flow velocities of 0.2-0.25 m/s better mixing behaviour as in standard PBRs while the energy uptake is 60-80% lower.