Light-gradient Mixing Performance Improvement of the Flat Plate Photobioreactor with Waved Baffles

L. Wang and X. You

Abstract
A computational fluid dynamics (CFD) simulation of a flat plate photobioreactor with waved baffles was performed. The research of the ratio of waved baffle height to wave length (L/λ) and the ratio of wave amplitude to wave length (A/λ) on light-gradient mixing was made. The optimized waved baffles structures of L/λ=12 and A/λ=0.2 was obtained, under which both the average turbulent kinetic energy in the downcomer ((TKE)d) and average liquid radial velocity in the downcomer (Ud) were larger. The light-gradient mixing was enhanced. Through the performance evaluation, (TKE)d increased about 35 % under the action of the optimized waved baffles than under traditional flat baffles. The statistical analysis method was employed, which reflects the light-gradient mixing more precisely than mean value. It is shown that the proportion of negative velocities indicating the radial mixing condition was 2.5 times larger in the optimized waved baffles than in traditional flat baffles.

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Keywords
CFD, Photobioreactors, Waved baffles, Mixing