Modeling Effect of Bubbles on Time-Dependent Radiation Transfer of Microalgae in a Photobioreactor for Carbon Dioxide Fixation

Microalgae are considered one of the most efficient and environmentally friendly ways for carbon dioxide fixation. The bubbles play an important role in analyzing the radiation transfer in photobioreactors during microalgae growth. Herein, Chlorella sp. and Scenedesmus obliquus were cultured in the airlift flat plate photobioreactor and evaluated for the temporal evolution of radiation characteristics. A one-dimensional model of bubbles on time-dependent radiation transfer in a photobioreactor was proposed, and it was well verified with the experimental result. The results indicated that with the increase of bubble volume fraction or the decrease of bubble radius, the local irradiance increased at the illuminated surface of the microalgal culture and was attenuated more rapidly along with the radiation transfer. The average specific growth rate of microalgae decreases as bubble volume fraction increases or bubble radius decreases. The volume fraction of 0.003 and a radius of 3.5 mm are the optimal operating conditions in this study for microalgae growth and carbon dioxide fixation. The presented analysis would facilitate the design and optimization of the optical and aeration configurations of photobioreactors for carbon dioxide fixation.

Automated summary

This study investigated the effects of bubbles on the radiation characteristics of microalgae growth and proposed a one-dimensional model of bubbles on time-dependent radiation transfer. Experimental results showed that with the increase of bubble volume fraction or the decrease of bubble radius, the local irradiance at the illuminated surface of microalgal culture increased and attenuated more rapidly along with the radiation transfer. Additionally, the average specific growth rate of microalgae decreased as the bubble volume fraction increased or bubble radius decreased.