Flow Field Simulation And Optimization Of The Tangent Tube-in-tube Photobioreactor Based On The Field Synergy

Microalgae as a kind of biomass energy resources, has a tremendous potential forenergy conservation and emission reduction. The photobioreactors for microalgaecultivation are developing rapidly in recent years. Among them, the tubularphotobioreactor has some advantages such as high output and suitable for large-scalecultivation, compared with other photobioreactors. However, it has somedisadvantages which limited its development such as weak mass transfer, hard tocontrol conditions, adherent cells and small pipe diameter limitation etc. Recently,many researchers designed different types of photobioreactors and mixing methods tocheck the cultivation effect. However, whether the structures and mixing methods canmake the conditions optimal was uncertain.Therefore, this paper first utilizes the field synergy principle in optimization ofmicroalgae cultivation environment. Combined the parabola structure and pipephotobioreactor, a novel tangent tube-in-tube photobioreactor is designed to generatelongitudinal vortexes. At the same time, the novel tangent tube-in-tubephotobioreactor structure is simulated and optimized. The concentric-tubephotobioreactor is also simulated, then compared with the tangent tube-in-tubestructure in order to forecast the cultivation effect of the tangent tube-in tubephotobioreactor.After simulations and comparison of two photobioreactors, we draw a conclusionthat:1. After simulation, longitudinal vortexes were generated in the tangenttube-in-tube reactor according with the field synergy principle, preliminarilyenhancing mass transfer.2. Downwards30°aeration direction and aeration rate of0.7vvm were moreadvantageous to the mixing effect in the dark zone, and the average|cos|of thesection was0.656, making the synergy extent of light direction and velocity field best,in order to improve the gas-liquid mass transfer efficiency, and make cells swimmingbetween the light and dark zones to enhance photosynthetic efficiency. 3. In the experiment of microalgae cultivation, we got the results that BG-11culture medium and chlorella sp. were most suitable to the next large-scale cultivation.Now the expermental table has been already constructed and the cultivationexperiment will begin up after the reactor processing.4. The average radial velocity and|cos|of the tangent tube-in tube reactor werebigger than that of the concentric-tube reactor and articles. Thus, the mixing effect oftangent tube-in-tube reactor was better.5. Experimental cultivation results of the concentric-tube bioreactor showed thatit has advantages in large-scale cultivation. However, the tangent tube-in-tube reactorwas better than it in the mixing effect, so the tangent tube-in-tube reactor has greaterpotential in large-scale cultivation.