Numerical Investigation of the Effects of Inlet and Outlet Configurations on Methanol Conversion and Flow‐Distribution Uniformity in a Methanol Steam Reforming Microreactor

Methanol steam reforming (MSR) in parallel multichannel microreactors is governed by heat transfer, species transport, catalytic reactions, and flow‐distribution processes. In this study, a three‐dimensional CFD model coupled with MSR reaction kinetics is developed to investigate the effects of heating‐gas inlet and outlet configurations and reactant‐inlet configurations on methanol conversion and methanol molar‐flow uniformity in a SiC honeycomb microreactor. The model is validated against experimental data. Six heating‐gas configurations representing coflow, counterflow, and cross‐flow arrangements are first compared. The heating‐gas flow arrangement has only a minor effect on the temperature field and methanol conversion because the high thermal conductivity of the SiC monolith promotes temperature homogenization. The maximum temperature difference within the monolith ranges from ~1.03–3.03 °C, while methanol conversion varies only slightly from 87.63% to 87.84%. The CO production rate likewise changes only slightly, from ~25.60–25.66 mL/min. Two idealized cases are then introduced to assess the relative effects of wall‐temperature nonuniformity and reactant‐flow maldistribution. Methanol conversion increases from 87.80% in the original case to 88.56% when the reforming‐channel wall‐temperature field is homogenized, while a higher conversion of 91.86% is obtained when the reactant flow is distributed uniformly among the microchannels. These results indicate that, under the present conditions, reactant‐flow maldistribution has a stronger influence on methanol conversion than the mild temperature nonuniformity. Finally, single‐, dual‐, and triple‐inlet reactant‐feeding schemes are compared. The maximum methanol conversion increases from 87.80% for the single‐inlet configurations to 90.00% for the dual‐inlet configurations and 91.58% for the triple‐inlet configurations. The maximum uniformity index (UI) within each inlet‐number category increases from 0.72–0.82 and 0.89, respectively. Increasing the number of reactant inlets therefore improves methanol molar‐flow uniformity and methanol conversion, although the incremental improvement decreases as additional inlets are introduced. The dual‐inlet configuration is therefore suggested as a candidate for further experimental evaluation under the present reactor geometry and operating conditions.