Plate-Frame Graphite-Foam Heat Exchanger

Abstract

A heat exchanger for thermally coupling a first fluid and second fluid is disclosed. The heat exchanger comprises plates comprising cores of thermally conductive graphite foam. A plurality of conduits for conveying the first fluid is formed in each core. Each plate further comprises thermally conductive barriers that sandwich the core, wherein the barriers are substantially impervious to r the first fluid and second fluid. Plates are stacked in a frame such that the frame and plates collectively define a plurality of channels for conveying the second fluid. Heat is exchanged between the primary fluid and the secondary fluid through the graphite-foam cores and barriers.Heat exchangers in accordance with the present invention can be lighter, have improved ratio of heat transfer surface density to heat exchanger volume, be lower cost, and / or be smaller for a given heat transfer capability than prior-art heat exchangers.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This case claims priority of U.S. Provisional Patent Application U.S. 61 / 145,996, which was filed on Jan. 21, 2009 (Attorney Docket: 711-246US), and which is incorporated herein by reference.[0002]In addition, the underlying concepts, but not necessarily the language, of the following case is incorporated by reference:[0003]U.S. patent application Ser. No. 12 / 484,542, filed Jun. 5, 2009 (Attorney Docket: 711-231US).[0004]If there are any contradictions or inconsistencies in language between this application and one or more of the cases that have been incorporated by reference that might affect the interpretation of the claims in this case, the claims in this case should be interpreted to be consistent with the language in this case.FIELD OF THE INVENTION[0005]The present invention relates to energy conversion in general, and, more particularly, to heat exchangers.BACKGROUND OF THE INVENTION[0006]Patent application Ser. No. 12 / 484,542, fil...

AI Technical Summary

Benefits of technology

[0017]Each plate comprises a “sandwich” structure of a graphite-foam core that interposes a pair of barriers. The barriers are substantially impervious to both the primary and secondary fluids. As a result, the barriers inhibit cross-contamination of the two fluids.

[0020]In some embodiments, the conduits formed in the graphite-foam core comprise open pores and capillaries that serve to enhance heat transfer through the graphite foam.

Problems solved by technology

Although shell and tube style heat exchangers are often used for ship / submarine service, they are typically characterized by relatively low heat transfer coefficients.

As a result, shell and tube heat exchangers are not well-suited for OTEC applications since they would require undesirably large surface areas.

This drawback is further exacerbated by the fact that there is normally only a small difference between seawater and process fluid temperatures.

Plate-frame heat exchangers have a high capital cost.

As a result, the cost associated with such heat exchangers would be increased further.

Such heat exchangers are not well-suited for OTEC applications, however, since seawater is corrosive to brazed fin joints.

Further, these heat exchangers are typically characterized by small passages that are prone to clogging due to biofouling.

Unfortunately, these modified brazed fin / extruded aluminum fin heat exchangers require large braze furnaces for their fabrication.

As a result, they are also quite expensive to produce.

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