3. Results and discussion
The methanol mole fraction contour maps are illustrated in Figure 1 for the integrated combustion-reforming reactor in which combustion chambers are in direct thermal contact to reaction chambers for an endothermic steam reforming reaction. Channels refers to the generally accepted meaning and includes conduits and other means for directing the flow of a fluid. Channels include at least one opening, typically with an inlet and outlet, and may include other openings. Fluid communication between two areas means that a fluid can flow from one area to the other. Thermal communication between two areas means that heat can flow from one area to the other. Heat exchanger is a device or component designed such that heat can be transferred from one fluid to another. The heat source for the endothermic reaction is delivered directly to the wall in contact with the endothermic catalyst. This follows from the fact that metal conduction is a more efficient mode of heat transfer than either convective or radiative heat transfer. In contrast to premixed combustion, where the heat release will occur primarily in the homogeneous phase, combustion jets can direct a concentrated stream of air into a separate fuel channel stream. The two streams subsequently mix and undergo an oxidation reaction. In order to suppress homogeneous combustion and promote heterogeneous catalytic combustion on the channel wall, unique jet design features can be implemented. Important features include geometry, size, and relative location and spacing. The jets should not only impinge on the wall but also spread out the combustion oxidant as uniformly as possible along the entire width of the channel. Furthermore, heterogeneous combustion is preferably concentrated at the combustion wall in closest proximity to the endothermic reaction catalyst. Combustion on other walls represents a heat loss and furthermore has a disadvantageous impact on thermal stresses in the device. In order to raise the temperature of an endothermic steam reforming reaction and reduce the likelihood of coke formation at the beginning of the reactor zone or in the heat exchanger zone reactant or product channels, more air should be delivered for combustion against the wall at the beginning of the reactor zone. Concentration of jets in this region as well as application of non-circular jet orifices can successfully meet this objective. All the goals above are desired to be accomplished with a minimal pressure drop for both economic reasons as well as for the purposes of preserving back pressure in the integrated combustion-reforming reactor device to ensure good flow distribution. To this end, a hybrid of circular and rectangular slot orifices can be implemented in the jet design. Alternatively, other non-rectangular non-circular jets could be used such as diamonds, triangles, semi-circles, quarter-moons, and the like. Computational fluid dynamics predictions indicate that a combination of these two jet geometries provide a more ideal heterogeneous fuel-oxidant mixture distribution on the combustion channel wall opposite the jet shim. It is recognized that other non-circular jet orifices could also be used at the entrance of the combustion zone or anywhere down the length of the reactor. It is also recognized that the combustion orifices could start before the reaction zone in the recuperative heat exchanger section to further preheat the reactants or further tailor the thermal profile of the device.