Dual-fluid laminar flow in microchannels can be utilised through microfabrication to create polymer membranes at the interface between aqueous and organic solutions. In order to enable smooth membrane growth it is necessary not only to maintain a stable interface between the aqueous and organic phase, but also to minimise near-wall stresses, which affect membrane attachment at the initial stages of membrane formation. The characteristics of the dual-fluid flow in the entrance region of the micro-channel can be significantly affected by the geometry of the inlet and flow rates involved. We present a numerical study of the effects of the inlet geometry on the flow development and near-wall stresses in xylene/water flows, which represent the initial stages of nylon 6,6 membrane formation on the interface between an aqueous solution of hexamethylenediamine and adipoyl chloride solution in xylene. The shape of the inlets considered here varies from a T-inlet (90 degrees inlet angles) to an M-inlet (0 degrees inlet angles). We show that although higher flow rates are needed in order to contain reagents to the narrow region near the interface, the increase of the flow rate leads to significant increase of the shear stresses with the maximum values being obtained in the entrance region thus preventing membrane attachment. CFD validation against experimental data for rhodamine diffusion broadening in a microfluidic is also presented.

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