Investigation on the performance of raceway ponds with internal structures by the means of CFD simulations and experiments

• CFD model for simulating raceway pond was validated by PIV test.
• Hydrodynamics of four types of raceway ponds were calculated and analyzed.
• Performance of traditional raceway pond was increased by built-in structures.
• Simulation results were verified by the experiments of microalgae cultivation.

Raceway pond is the most widely used for large scale microalgae culture. In the present study, the Particle Image Velocimetry technology was used to validate the reliability of the computational fluid dynamics simulation model for raceway pond. In order to increase the mixing degree and decrease the power consumption, novel mixers called sloping baffles and flow deflectors were combined in the raceway pond. The hydrodynamic characteristics of four types of raceway ponds (traditional raceway, raceway fitted with flow deflectors, raceway fitted with sloping baffles, raceway fitted with both flow deflectors and sloping baffles) were simulated by computational fluid dynamics. The results showed that the raceway pond fitted with sloping baffles and flow deflectors reduced the power consumption by 10%, increased the average velocity by 6.8%, promoted the velocity along the light attenuation direction by 93% and significantly eliminated the dead zone compared with the traditional raceway pond at the condition of rotation speed of paddlewheel of 20 rpm. Lastly, cultivation of Chlorella pyrenoidosa experiments was conducted, and the results indicated that the combination of sloping baffles and flow deflectors can significantly improve the productivity of microalgae.