E.R. Delsman

Microchannel Plate Geometry Optimization for Even Flow Distribution at High Flow Rates

Microreactors generally consist of microstructured plates containing a large number of equal channels. The small diameter of the channels enables high heat and mass transfer rates. To exploit this feature and realize a high throughput within a small volume, it is necessary to use high flow rates. However, at these high flow rates it is not straightforward to obtain an even distribution of fluid flow over the individual microchannels. A three-dimensional computational fluid dynamics (CFD) model was used to calculate the flow distribution on a microstructured plate. Calculation time was reduced by introducing an artificial viscosity in the channel region. The calculations show that a transitional velocity exists, below which the flow distribution is independent of velocity and above which inertia effects start to influence the distribution. To optimize the flow distribution, nine different plate geometries were studied at flow rates between 0.1 and 100 m s–1, or 4 × 10–4 to 0.4 m3 h–1 per plate. By optimizing the plate geometry, the relative standard deviation of the flow distribution was reduced from 19 to 3%. Furthermore, it is shown that the optimal geometry depends on the flow rate, which thus needs to be taken into account in the design of microchannel plates.

MiRTH-e: Micro reactor technology for hydrogen and electricity

Research groups of six companies, institutes and universities have joint forces in a European Community funded project, to develop a miniaturized, low-power fuel processor for the conversion of methanol into clean hydrogen for use in a proton exchange membrane (PEM) fuel cell. The integrated unit will provide a portable power source and is an alternative for battery packs or hydrogen storage in metal hydrides. In the realization of this small-scale fuel processor, microreactor technology will play a key role. Based upon a so-called pinch analysis, a conceptual design of the fuel processor is made, consisting of three combined microreactors/heat exchangers.