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Title: Candidate alloys for cost-effective, high-efficiency, high-temperature compact/foil heat-exchangers

Abstract

Solid oxide fuel cell (SOFC) and molten carbonate fuel cell (MCFC) systems operate at high temperatures (up to 1000 C and 650 C, respectively), which makes them especially attractive sources for combined heat and power (CHP) cogeneration. However, improvements in the efficiency of heat exchange in these fuel cells require both development and careful processing of advanced cost-effective alloys for use in such high-temperature service conditions. The high-temperature properties of both sheet and foil forms of several alloys being considered for use in compact heat-exchangers (recuperators) have been characterized. Mechanical and creep-rupture testing, oxidation studies, and microstructural studies have been performed on commercially available sheet and foil forms of alloy 347, alloys 625, HR230, HR120, and the new AL20-25+Nb. These studies have led to a mechanistic understanding of the responses of these alloys to anticipated service conditions, and suggest that these alloys developed for gas- and micro-turbine recuperator applications are also suitable for use in fuel cell heat-exchangers. Additional work is still required to achieve foil forms with creep life comparable to thicker-section wrought product forms of the same alloys.

Authors:
 [1];  [1];  [1];  [1];  [1]
  1. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Shared Research Equipment Collaborative Research Center
Sponsoring Org.:
OE USDOE - Office of Electric Transmission and Distribution; USDOE Office of Science (SC)
OSTI Identifier:
932075
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Conference: Materials Science & Technology'07, Detroit, MI, USA, 20070916, 20070920
Country of Publication:
United States
Language:
English
Subject:
30 DIRECT ENERGY CONVERSION; ALLOYS; COGENERATION; CREEP; EFFICIENCY; FUEL CELLS; HEAT EXCHANGERS; MOLTEN CARBONATE FUEL CELLS; OXIDATION; PROCESSING; SOLID OXIDE FUEL CELLS; TESTING; heat exchangers; foil; creep resistance; austenitic alloys; HR230

Citation Formats

Evans, Neal D, Maziasz, Philip J, Shingledecker, John P, Pint, Bruce A, and Yamamoto, Yukinori. Candidate alloys for cost-effective, high-efficiency, high-temperature compact/foil heat-exchangers. United States: N. p., 2007. Web.
Evans, Neal D, Maziasz, Philip J, Shingledecker, John P, Pint, Bruce A, & Yamamoto, Yukinori. Candidate alloys for cost-effective, high-efficiency, high-temperature compact/foil heat-exchangers. United States.
Evans, Neal D, Maziasz, Philip J, Shingledecker, John P, Pint, Bruce A, and Yamamoto, Yukinori. Mon . "Candidate alloys for cost-effective, high-efficiency, high-temperature compact/foil heat-exchangers". United States. doi:.
@article{osti_932075,
title = {Candidate alloys for cost-effective, high-efficiency, high-temperature compact/foil heat-exchangers},
author = {Evans, Neal D and Maziasz, Philip J and Shingledecker, John P and Pint, Bruce A and Yamamoto, Yukinori},
abstractNote = {Solid oxide fuel cell (SOFC) and molten carbonate fuel cell (MCFC) systems operate at high temperatures (up to 1000 C and 650 C, respectively), which makes them especially attractive sources for combined heat and power (CHP) cogeneration. However, improvements in the efficiency of heat exchange in these fuel cells require both development and careful processing of advanced cost-effective alloys for use in such high-temperature service conditions. The high-temperature properties of both sheet and foil forms of several alloys being considered for use in compact heat-exchangers (recuperators) have been characterized. Mechanical and creep-rupture testing, oxidation studies, and microstructural studies have been performed on commercially available sheet and foil forms of alloy 347, alloys 625, HR230, HR120, and the new AL20-25+Nb. These studies have led to a mechanistic understanding of the responses of these alloys to anticipated service conditions, and suggest that these alloys developed for gas- and micro-turbine recuperator applications are also suitable for use in fuel cell heat-exchangers. Additional work is still required to achieve foil forms with creep life comparable to thicker-section wrought product forms of the same alloys.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

Conference:
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  • Oak Ridge National Laboratory (ORNL) has conducted research and development for several years which has been focused on the behavior and performance improvements of sheets and foils of various alloys for compact heat-exchangers (recuperators) for advanced microturbines. The performance and reliability of such thin sections are challenged at 650-750 C by fine grain size causing excessive creep, and by moisture effects greatly enhancing oxidation attack in exhaust gas environments. Standard 347 stainless steel has been used successfully at or below 600 C, but has suffered from both of these kinds of degradation at 650 C and above. Alloys have beenmore » identified which can have very good properties for such heat-exchangers, especially with careful control of microstructure during processing, including alloy 625, HR120 and the new AL20-25+Nb. These alloys, and the mechanistic understanding behind their behavior, are also applicable to achieving the better heat-exchanger technology needed for fuel cells or other high-temperature, clean-energy applications.« less
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  • Reduction in the cost of balance of plant applications is one of the top priority focus areas for the successful implementation of solid oxide fuel cell technology. High temperature heat exchangers are employed to heat cathode air utilizing either hot gases coming from the anode side of the stack or other hot gases generated by external processes. In order to reduce the cost of heat exchangers, it may be necessary to apply several different materials, each in a different temperature zone, for the construction of the heat exchanger. This technique would require the joining of dissimilar materials in the construction.more » In this work, welding of commercial candidate dissimilar materials is explored. Filler materials were identified using equilibrium phase diagrams and thermodynamic simulation software. Autogenous welding was performed and the welding defects were characterized. Finally, experimental weld microstructures were compared to phases predicted by the simulations.« less
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