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A Multi-Disciplinary Approach to Materials Joining for Fabrication of a Prototype Stirling Engine Heat Exchanger


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A prototype heat exchanger for a Stirling type heat engine is fabricated using multi-disciplinary joining techniques. A complex assortment of materials and geometries are joined in multiple steps producing sub-assemblies which are then consolidated into the final heat exchanger assembly. To build the heat exchanger, an array of Inconel 718 tubes is high vacuum furnace brazed to Multimet Alloy tube headers and Multimet header collectors using commercially available BNi-2 BFM paste. A set of vendor-fabricated electromagnetic (EM) susceptor tiles, individually comprised of cylindrical AlN:Mo ceramic matrix composite elements, a metal back-plane assembly including a Kovar baseplate, and internal (96.4Au-3Ni-0.6Ti) Braze Filler Metal (BFM) interfaces are then high vacuum furnace brazed to the Inconel tubing array also using BNi-2 BFM paste and foil. Finally, the completed absorber/tubing array is then joined to the Stirling engine cylinders using Gas Tungsten Arc Welding (GTAW) more commonly known as Tungsten Inert Gas (TIG) welding and Multimet filler rod. The complete heat exchanger assembly is then leak checked using a Varian Helium-leak tester. Mating of the heat exchanger to the Stirling engine and performance testing is not discussed herein.



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