An Experimental Investigation on the Multiphase Flows in a Photobioreactor for Algae Cultivation

Light absorption, fluid dynamics, and algal metabolism are the three key factors in determining the overall algae cultivation performance of a photobioreactor. The turbulent mixing of multiphase flows inside the photobioreactor (i.e., liquid phase - water, gas phase - CO2 and O2, and solid phase - algae cells) is the core connecting the three key factors together. In the present study, a comprehensive experimental investigation is conducted to quantify the effects of turbulent mixing in photobioreactors on the reactor performance for algae cultivation. A high-resolution particle image velocity (PIV) system will be used to achieve time-resolved, in-situ flow field measurements to quantify the turbulent mixing inside the bioreactors, while algal cultures will also be grown in the same reactors. The effects of various important controlling flow parameters, such as the flow rate of the air flow, the formation of the circulation regions, and the turbulent kinetic energy level of the mixing flow inside the photobioreactor on the final growth rate of algae, were investigated in great detail. The detailed flow field measurements results about the mixing characteristics are correlated with the algal growth performance in the photobioreactors to elucidate the underlying physics in order to explore/optimize design paradigms for the the optimum design of photobioreactors for algal cultivation.