Design of confluence and bend geometry for rapid mixing in microchannels

In micromixers, reactant fluids deform through convection arisen by channel geometries such as channel confluence and bend. This deformation reduces the diffusion length between fluids and thus enhances the mixing performance. This paper discusses the effects of channel confluence and bend geometries in microchannles on mixing rate. The results show that the combination of these geometries enhances the mixing performance under the condition that the channel bend is set after the confluent flow sufficiently develops. Larger confluence angle is also effective for rapid mixing. We also confirmed that the bend geometry has little effect for increasing the pressure drop in microchannels. To achieve a fixed segregation index, which represents the mixing performance, microchannels with a bend requires smaller flow rate and thus lower pressure drop than straight channels. From the experimental results, we have established the design guideline of microchannel for improving mixing performance without channel reduction and pressure drop confirmed the effectiveness of this guideline. Using this guideline, a micromixer with high operability and productivity can be developed.

► Channel geometry including confluence and bend for achieving rapid mixing is examined.
► Larger confluence angle provides enhanced convection and better mixing.
► Horizontal bend gives unsymmetrical flow of the two fluids and better mixing.
► Bend after the development of velocity distribution gives better mixing.
► Micromixer based on the above guideline gives enhanced mixing performance without channel reduction.