Multilayer Microchannel Research Articles

Preferential oxidation of CO over CuO/CeO 2 and Pt-Co/Al 2O 3 catalysts in micro-channel reactors

Micro-channel plates with dimension of 1 mm × 0.3 mm × 48 mm were prepared by chemical etching of stainless steel plates followed by wash coating of CeO 2 and Al 2O 3 on the channels. After coating the support on the plate, Pt, Co, and Cu were added to the plate by incipient wetness method. Reaction experiments of a single reactor showed that the micro-channel reactor coated with CuO/CeO 2 catalyst was highly selective for CO oxidation while the one coated with Pt-Co/Al 2O 3 catalyst was highly active for CO oxidation. The 7-layered reactors coated with two different catalysts were prepared by laser welding and the performances of each reactor were tested in large scale of PROX conditions. The multi-layered reactor coated with Pt-Co/Al 2O 3 catalyst was highly active for PROX and the outlet concentration of CO gradually increased with the O 2/CO ratio due to the oxidation of H 2 which maintained the reactor temperature. The multi-layered reactor coated with CuO/CeO 2 showed lower catalytic activity than that coated with Pt catalyst, but its selectivity was not changed with the increase of O 2/CO ratios due to the high selectivity. In order to combine advantages (high activity and high selectivity) of the two individual catalysts (Pt-Co/Al 2O 3, CuO/CeO 2), a serial reactor was prepared by connecting the two multi-layered micro-channel reactors with different catalysts. The prepared serial reactor exhibited excellent performance for PROX.

Hot wire anemometry for experimental determination of flow distribution in multilayer microreactors

Thermal anemometry with constant wire temperature for characterization of the flow distribution was applied for multilayered microchannel reactors first. A reactor system made by stereolithography was used as a model. The hot wire 400 μm long was placed in front of the microchannel exits 800 μm wide. Using a micrometer table all single channel volume flows were measured in the model reactor in dependence of the overall flow through the reactor. A strongly pronounced core flow through the microchannel body was observed at flows where laminar flow was calculated in the reactor inlet tube. This was a result from the design, i.e. of ratio of inlet tube cross-section area to the sum of channel cross-section areas. Calculating pressure drop of channel and reactor inlet tube showed that pressure drop was approximately 10 times higher in the tube than in the channels. In this special case inlet turbulence helped to equalize the flow over the channels.

Forced Convective Heat Transfer in Parallel Flow Multilayer Microchannels

Abstract In this paper, the effect of increasing the number of layers on improving the thermal performance of microchannel heat sinks is studied. In this way, both numerical and analytical methods are utilized. The analytical method is based on the porous medium assumption. Here, the modified Darcy equation and the energy balance equations are used. The method has led to an analytical expression presenting the average dimensionless temperature field in the multilayer microchannel heat sink. The effects of different parameters such as aspect ratio, porosity, channel width, and the solid properties on the thermal resistance are described. The results for single layer and multilayer heat sinks are compared to show the effectiveness of using multilayer microchannels.