Heat and Mass Transfer and Wall Contact for Laminar Vortices in Microreactors
In microreactors, interactions between fluid and channel wall affect many chemical reactions. Due to a good heat and momentum transfer, highly exothermic reactions can be quenched and so combustion is inhibited. On the other hand, reactions on catalyst-coated walls call for a high mass transport to and from the walls which is one of the parameters determining the reaction rate for fast reactions. In this contribution, heat and mass transfer towards the walls are investigated in bent microchannels. Laminar flow in the Reynolds number range of 100 < Re < 1000 is studied, where Dean vortices are induced by bends. Optimized geometries of the bends are found with numerical fluid simulations and compared experimentally using chemical reactions. As characteristic parameter, the contact time distribution is calculated which is defined by the distribution of the residence time in regions near the wall. For the characterization of the reactors, also simulations of heat flux are performed. Various optimized reactors are fabricated and experimentally compared by a luminol reaction catalyzed at the copper-plated walls. In other experiments, heat transfer into the fluid is measured. The experimental results are compared to the simulated transport processes.