3. Flow characteristics

3.1 Single-phase flows

The small channel dimensions in microreactors or microstructured reactors mean that the flow regime is almost always laminar. This translates into a parabolic velocity profile and, in the case of simple geometries, parallel streamlines, thus creating residence time and mixing difficulties.

Due to radial velocity gradients in a parabolic profile, molecules in a flow have widely varying residence times in a single microchannel. As a result, the flow is characterized by high axial dispersion and a wide residence time distribution, properties that are undesirable for chemical reaction. It is therefore important to control the flow by modifying the channel geometry to promote transverse movement and reduce axial dispersion.