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Microbubble generation by a novel fluidic oscillator driven approach is analyzed, with a view to identifying the key design elements and their differences from standard approaches to airlift loop bioreactor design. The microbubble generation mechanism has been shown to achieve high mass transfer rates by the decrease of the bubble diameter, by hydrodynamic stabilization that avoids coalescence increasing the bubble diameter, and by longer residence times offsetting slower convection. The fluidic oscillator approach also decreases the friction losses in pipe networks and in nozzles / diffusers due to boundary layer disruption, so there is actually an energetic consumption savings in using this approach over steady flow. These dual advantages make the microbubble generation approach a promising component of a novel airlift loop bioreactor whose design is presented here. The equipment, control system for flow and temperature, and the optimization of the nozzle bank for the gas distribution system are presented. §1 Introduction Airlift reactors are perceived to have performance advantages over bubble columns and stirred tank bioreactors for many applications, biorenewables production in particular.Where the product is a commodity biochemical or biofuel, energy efficiency is the primary concern. There are multiple objectives for the optimization of energy efficiency, however. The hydrodynamics of stirring is an important consideration, as are the phase transfer of nutrient influx and the efflux of inhibitor products and byproducts. Finally, the metabolism of cells or microbes engaged in the biochemical production are a major constraining factormass transfer from the bulk liquid to the bioculture must be maintained. There are two important reasons to use airlift loop bioreactors (ALB) that arise from the airlift effects: flotation and flocculation. Small bubbles attached to particles or droplets significantly lower the density of the aggregrate. Grammatika and Zimmerman (2001) describe these generalized flotation effects. Such aggregates are susceptible to floc formation. Typically, microbes or cells that sediment out of the suspension accumulate in stagnation zones at the bottom expire.Given the importance of energy usage in the operation of ALBs, it is surprising that the sparging system, which is the central power consumption feature of the ALB, has not received more attention. Jones (2007) gives a good review of the major features of ALB, including the conventional types of sparger design. Chisti and Moo-Young (1987) classify the spargers used in the ALB as dynamic and static. Dynamic spargers use injection through nozzles to disperse the gas introduced. Static spargers are typically less reliant on the momentum of the jet, and the gas is introduced typically through a perforated plate (see Deshpande and Zimmerman, 2005a,b) or less commonly, through a porous baffle (Heijnen and Van't Riet, 1984). This study was motivated by the development of a novel microbubble generation technique based on fluidic oscil...

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A conservative level-set method (LSM) embedded in a computational fluid dynamics (CFD) simulation provides a useful approach for the studying the physics and underlying mechanism in two-phase flow. Detailed two-dimensional (2D) computational microfluidics flow simulations have been carried out to examine systematically the influence of different controlling parameters such as flow rates, viscosities, surface wettability, and interfacial tensions between two immiscible fluids

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