(468c) Simplified Model-Based Design and Shape Optimization for T-Shaped Microreactors with Secondary Flow
AIChE Annual Meeting
Wednesday, November 11, 2009 - 4:05pm to 4:30pm
T-shaped microreactors, which use two horizontal arms as the inlet channels and one vertical arm as the mixing channel, have attracted in the academic and industrial field. Using T-shaped microreactors in secondary flow regime, a complete reaction with a high product yield can be realized on a short mixing time. In the design of T-shaped microreactors to achieve desired product yield, the fluid velocity and the size and geometry of mixing channel are essential factors, but a systematic design method on these essential factors has not been established. Moreover, when parameter studies or optimization runs need to performed in the microreactors, the repeating computational burden related to the normal Computational Fluid Dynamics (CFD) model is usually much too heavy. Therefore, a simplified model is indispensable to describe the mixing, diffusion and reaction phenomena in the T-shaped microreactors.
In this research, a simplified lamellar model is developed to efficiently design T-shaped microreactors with secondary flow. In the model, the same thicknesses of striations are produced initially by mixing without reaction or diffusion, and then reaction and diffusion are allowed to occur in the mixing channel. The concentration profiles under laminar flow condition in the flow direction are estimated by a simplified lamellar model based on the two-dimensional convection- diffusion -reaction equations. The two dimensions are the flow direction along the mixing channel (x direction) and the same direction as the flow path along the inlet channel (y direction). At the first step of building the lamellar model, the fluid velocity and the striation thickness are used to predict the product yield. Then, a pseudo-three-dimensional model, which combines the x-y lamellar model and the x-z lamellar model (z is the vertical direction of x-y surface), is constructed. It can complement the concentration distribution in the y-z direction of cross section at different location along the mixing channel. Therefore, comparing to the first x-y dimensional lamellar model, the predictive accuracy of concentration profiles is improved by the pseudo-three-dimensional model.
Using the developed pseudo-three-dimensional lamellar model, the cross section size can be optimized to get the desired product yield. To investigate the effectiveness of the optimization results, a series-parallel reaction system in T-shaped microreactors is used to compare the three-dimensional CFD simulation results and the proposed model. In the comparison, the rate constant of the reaction and the flow velocity distribution are discussed on the effectiveness of the lamellar model. Though the discussion results, a design guideline for shape design using the simplified model is mentioned.