The effect of
flow configuration, namely co- vs.
counter-current
flow, on the operation of multifunctional microdevices for hydrogen production is analyzed using two-dimensional computational fluid dynamics simulations. Stoichiometric propane/air gaseous
combustion and ammonia reforming on Ru occur in alternate parallel channels (600 and
![Click to view the MathML source](http://www.sciencedirect.com/cache/MiamiImageURL/B6TFK-4GJM3V5-2-R/0?wchp=dGLzVlz-zSkWA)
wide, respectively) separated by a thermally conducting wall (
![Click to view the MathML source](http://www.sciencedirect.com/cache/MiamiImageURL/B6TFK-4GJM3V5-2-S/0?wchp=dGLzVlz-zSkWA)
thick). It is shown that complete conversion of ammonia can be achieved at millisecond residence times in both
flow configurations. The power generated, based on 100%utilization of the hydrogen produced, is in the range of 8–60 W per cm height of the device depending on
flow rates. A proper balance of the
flow rates of the
combustion and reforming streams is, however, crucial in achieving this. For either configuration, the maximum power generated is determined by extinction at large reforming stream
flow rates. Materials stability, resulting from high temperatures generated at low reforming stream
flow rates, determines the lower power limit for a given
flow rate of combustible mixture. The two
flow configurations are contrasted based on multiple performance criteria, such as device temperature, power exchanged, conversions, and net hydrogen production by constructing operation maps. They are found to be practically equivalent for highly conductive materials. Using properly balanced
flow rates, the co-current configuration expands the operation window to medium as well as low thermal conductivity materials as compared to the
counter-current configuration that shows a slightly superior performance but in a rather narrow regime of high ammonia
flow rates and high thermal conductivity materials.