Numerical study of liquid mixing in microalgae-farming tanks with baffles

Abstract

One possible renewable energy source is microalgal biomass, representing sunlight-driven cell factories. Experimental studies have shown that a uniform mixture of microalgae is required for their access to sunlight. Generally, running paddlewheels for raceway ponds and mechanical pumps for photobioreactors are used, and their electricity consumption increases the costs of algae-mediated biodiesel production. To reduce the consumption of electricity, we developed the idea of using a floating automatic mix system based on the mixing nature of liquid sloshing in a baffled tank floating in the ocean. When oscillatory water waves induce liquid sloshing in the tank, vortices form and shedding is generated by horizontal baffles installed in the tank. Wave motions may be employed to enhance the mixing of microalgae in the tank and dramatically reduce the electricity consumption that is required in traditional algae-mediated biodiesel production. The vortex generation of sloshing liquids in a tank with horizontal baffles was numerically and experimentally investigated in this study. The effects of baffle location and length were systematically studied.The study and application of liquid sloshing in a tank with baffles are usually used to tune liquid dampers for vibration control of a structure. The particles movement and mixing in the tank are seldom discussed. The simulation results found in this study introduce a new application for liquid sloshing in a tank with baffles. Appropriately allocated horizontal baffles in the tank can significantly enhance the mixing of liquid particles and can be applied in microalgae cultivation.