Static mixer proposal for tubular photobioreactors to reduce mixing energy consumption and enhance light–dark cycles

Abstract

AbstractBACKGROUNDTubular Photobioreactors (PBR) present better productivity using static mixers but they consume large amounts of energy. In this study, a tubular PBR is presented with a new static mixer that produces swirl mixing, inducing light–dark (LD) cycles, and adequate uptake of nutrients in the culture. This study was focused on diminishing the pumping energy required for culture transport while improving productivity by the development of LD cycles in microalgae culture.RESULTSThree types of tubular PBRs with mixers that induce swirl flow were simulated using computational fluid dynamics (CFD). Pumping energy and mixing degree were estimated. Mixing conditions and swirl flow were calculated through the swirl number. Evaluation of the illumination periodic behavior induced by the proposed new configuration in the frequency domain, using the Discrete Fourier Transform (DFT), revealed a distinctive correlation between main frequencies and average flow velocity. Energy consumption results showed that the proposed mixer consumes the least energy in comparison with others proposed previously in the literature; moreover, the proposed mixer also is simpler than traditional types. Thus, there are cost benefits in using this static mixer in tubular PBR mixing. © 2020 Society of Chemical Industry