Characterization of Microreactors with Respect to Pressure Drop, Heat Transfer and Mixing Efficiency

Microreactors have been shown to greatly improve process in the pharmaceutical and fine chemical industry and provide solutions to many of the drawbacks that exist in batch and semi-batch processes. However, industry experts agree that there is a need for a standard method of analysis to compare the performance of complex microreactor geometries. This study provides a method to compare the pressure drop and mixing efficiency on a common scale and observes the effect of reactor materials on the overall heat transfer. Semi-empirical pressure drop modeling determined the pressure drop along the mixing zone and showed that the axial mixing of the tangential mixing unit had the highest friction factor. Mixing efficiency was characterized using the 4th Bourne reaction and showed that under turbulent conditions at a given energy dissipation the mixing efficiency is independent from geometry and confirmed that their mixing occurs at the same mixing time scale. However, after increasing the viscosity of the system, the geometries differed in their transition from turbulent to laminar. The tangential mixing unit showed to have lowest regime transition Reynolds number. The effect of reactor materials was observed with respect to heat transfer performance. Empirical modeling determined that the Hastelloy reactor provided a heat transfer rate up to 40% greater than a glass system and was limited by the convective heat transfer of the reactor channels whereas the glass reactor was limited by the thermal conductivity of the reactor wall.