Enhancing microalgal biomass productivity with an optimized flow field generated by double paddlewheels in a flat...

Computational fluid dynamics were used to analyze the flash light effect and CO₂ bubble behavior in an optimized flow field generated by double paddlewheels in a flat plate photoreactor to enhance microalgal biomass productivity. The increased D/w ratio significantly enhanced the average turbulent kinetic energy and flash cycle frequency. However, the effects became weak when the D/w ratio was over 0.67. Appliance of double paddlewheels increased flash cycle frequency from 0.035 to 0.121 Hz and increased light time ratio from 8.3% to 31.5%. Meanwhile, the bubble dynamic behavior was characterized using population balance model. The average bubble size reduced by 24.4% and the bubble rising velocity reduced by 10.6%, which facilitated CO₂ mixing and mass transfer in microalgal solution. Therefore, biomass accumulation of microalgae Chlorella in the photoreactor with double paddlewheels increased by 62.3% under 15% CO₂.