Rapid start fuel reforming systems and techniques
An on-board fuel processor includes a microchannel steam reforming reactor ( 30 ) and a water vaporizer ( 40 ) heated in series with a combustion gas. The reformer ( 30 ) and the vaporizer ( 40 ) are both of a cross-flow panel configuration that allows for low combustion side pressure drop. Fuel is directly injected into the steam, and during a rapid cold start, both the combustion gas flow rate and the steam to carbon ratio are substantially increased relative to their steady state operating values. A rapid cold start can be achieved in under 30 seconds with a manageable amount of electric power consumption, removing impediments to use in automotive fuel cell applications.
1. A fluid processing device comprising:
a stack of thin sheets integrally bonded, the stack including alternating recessed sheets having aligned triangular first and triangular second header openings at two opposing ends of the stack, wherein the recesses in the sheets define a plurality of first microchannel flow paths between the first header openings at the two opposing ends of the stack and a plurality of second flow paths distinct from the first microchannel flow paths and between the second header openings at the two opposing ends of the stack,
wherein the aligned first and second header openings have a shape that generally defines at least three sides wherein two sides are substantially longer than a third side and wherein the two longer sides are relatively adjacent the first microchannel flow paths and the shorter side is relatively spaced from the first microchannel flow paths and generally perpendicular to a line connecting the openings at the two opposing ends of the sheets;
at least two support ribs adjacent to at least one of the two longer sides of the first header opening or the second header opening; and
at least one support structure located at an apex of the first header opening or an apex of the second header opening;
wherein the cumulative cross sectional area of the flow in an entrance region to the first microchannel flow paths is within about 20% of the cross sectional area of the flow in the first microchannel flow paths a substantial distance removed from the entrance region.
2. The fluid processing device of claim 1 wherein the aligned first and second header openings have a major axis that is generally parallel with a line connecting the openings at the opposing ends of the sheets.
3. The fluid processing device of claim 1 wherein the triangular first and second header openings have a height that is at least 2 times the length of the base.
4. The fluid processing device of claim 1 wherein the cumulative cross sectional area of the flow in the entrance region is within about 10% of the cross sectional area of the flow a substantial distance removed from the entrance region.
5. The fluid processing device of claim 1 wherein the device is a laminar flow heat exchanger capable of greater than 80% effectiveness between two equi-molar flows of air at 1 atm pressure where the pressure drop in each air stream is less than about 2.5 inches of water.
6. A fluid processing device comprising:
a stack of thin sheets integrally bonded, the stack including alternating recessed sheets having aligned triangular first and triangular second header openings at two opposing ends of the stack, wherein the recesses in the sheets define a plurality of first microchannel flow paths between the first header openings at the two opposing ends of the stack and a plurality of second microchannel flow paths between the second header openings at the two opposing ends of the stack,
wherein the aligned first and second header openings have a shape that generally defines at least three sides wherein two sides are substantially longer than a third side and wherein the two longer sides are relatively adjacent the first microchannel flow paths and the shorter side is relatively spaced from the first microchannel flow paths and generally perpendicular to a line connecting the openings at the two opposing ends of the sheets;
at least two support ribs bonded between each sheet and adjacent to at least one of the two longer sides of the first header opening or the second header opening; and
at least one support structure bonded between each sheet and located at an apex of the first header opening or an apex of the second header opening;
wherein
the cumulative cross sectional area of the flow in an entrance region to the first microchannel flow paths is within about 50% of the cross sectional area of the flow in the first microchannel flow paths a substantial distance removed from the entrance region.