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A vaporizer is provided for vaporizing liquid in a fluid stream. The vaporizer includes at least two heat exchangers serially arranged in a direction of flow of the fluid stream through the vaporizer for vaporizing liquid in the fluid stream in stages. The heat exchangers each comprise a first plura

A vaporizer is provided for vaporizing liquid in a fluid stream. The vaporizer includes at least two heat exchangers serially arranged in a direction of flow of the fluid stream through the vaporizer for vaporizing liquid in the fluid stream in stages. The heat exchangers each comprise a first plurality of thermally conductive flow channels through which the fluid stream flows and a second plurality of thermally conductive flow channels through which a heating stream flows and which are in heat exchange relationship with the first plurality of thermally conductive flow channels. A liquid supply means is provided for adding liquid to a downstream heat exchanger. The added liquid mixes with the vaporized stream exiting an upstream heat exchanger for vaporization in the downstream heat exchanger.

대표청구항 ▼

1. A system comprising:a vaporizer having an inlet receiving a fluid stream comprising a liquid which is vaporized to form a vaporized outlet stream, said vaporizer comprising at least two heat exchange sections serially arranged in a direction of flow of said fluid stream through said vaporizer for

1. A system comprising:a vaporizer having an inlet receiving a fluid stream comprising a liquid which is vaporized to form a vaporized outlet stream, said vaporizer comprising at least two heat exchange sections serially arranged in a direction of flow of said fluid stream through said vaporizer for vaporizing liquid in said fluid stream in stages, said heat exchange sections each comprising at least one first channel through which said fluid stream flows and at least one second channel comprising heating means, said first and second channels being separate from one another and arranged in heat transfer relationship with one another; a liquid supply means for adding liquid to a downstream heat exchange section of said at least two heat exchange sections, said added liquid mixing with said fluid stream exiting an upstream heat exchange section of said at least two heat exchange sections, for vaporization within said downstream heat exchange section; and a subsystem in fluid communication with an outlet of said vaporizer, said subsystem receiving said vaporized outlet stream; wherein said first channels are defined by grooves in a first planar surface of respective said heat exchange sections and said second channels are defined by fins in a second planar surface of respective said heat exchange sections. 2. The system of claim 1 wherein said heating means comprises electrical resistive heating.3. The system of claim 1 wherein said heating means comprises a fluid heating medium.4. The system according to claim 3 wherein said second channels comprise an oxidation catalyst and said heating medium comprises oxidation products.5. The system of claim 4 wherein said heating medium comprises hydrogen and carbon monoxide, said catalyst is selective for oxidation of carbon monoxide in the presence of hydrogen, and said oxidation products comprise carbon dioxide.6. The system of claim 3 which comprises a first heating medium flowing in said second channel of said upstream heat exchange section and a second heating medium flowing in said second channel of said downstream heat exchange section, where said first heating medium is different from said second heating medium.7. The system of claim 3 wherein said heating means comprises a hot flowing fluid.8. The system of claim 1 wherein said subsystem is a reformer reactor.9. The system of claim 1 wherein said upstream heat exchange section is at a higher pressure than said downstream heat exchange section.10. The system of claim 1 wherein the downstream heat exchange section is a first downstream heat exchange section, and the system further comprises a second downstream heat exchange section, wherein the fluid stream from said upstream heat exchange section is divided between said first and second downstream heat exchange sections.11. The system of claim 10 wherein said heating medium has a flow path to and through said second downstream heat exchange section and then through said first downstream heat exchange section and then through said upstream heat exchange section.12. The system of claim 1 in which said at least two heat exchange sections each comprise first, second and third heat exchange sections arranged in series with respect to the direction of flow of said fluid.13. The system of claim 1 wherein said heating medium has a flow path which is countercurrent with respect to a flow path of said fluid stream through said at least two heat exchange sections.14. The system of claim 1 which further comprises a source of pressurized gas and mixing means upstream of said inlet for combining said pressurized gas with said fluid stream entering said vaporizer.15. The system of claim 1, wherein said heat exchange sections are arranged along a common core.16. The system of claim 1, wherein said heat exchange sections include a first group of elongate channels defined by said grooves and a second group of elongate channels defined by said fins.17. The system of claim 16, wherein said first group of channels and said second group of channels are transverse with respect to one another.18. The system of claim 1, wherein an electrical resistive heating element forms part of said fins.19. The system of claim 1, wherein said subsystem is a fuel cell stack and said vaporized outlet stream comprises water for humidifying said fuel cell stack.20. A system comprising:a vaporizer having an inlet receiving a fluid stream comprising a liquid which is vaporized to form a vaporized outlet stream, said vaporizer comprising at least two heat exchange sections serially arranged in a direction of flow of said fluid stream through said vaporizer for vaporizing liquid in said fluid stream in stages, said heat exchange sections each comprising at least one first channel through which said fluid stream flows and at least one second channel comprising heating means, said first and second channels being separate from one another and arranged in heat transfer relationship with one another; a liquid supply means for adding liquid to a downstream heat exchange section of said at least two heat exchange sections, said added liquid mixing with said fluid stream exiting an upstream heat exchange section of said at least two heat exchange sections, for vaporization within said downstream heat exchange section; a reactor in fluid communication with an outlet of said vaporizer, said reactor receiving said vaporized outlet stream for reaction within said reactor to produce a reaction product; and a pressure control means to maintain said upstream heat exchange section at a higher pressure than said downstream heat exchange section.