Design and Manufacturing Development of Lightweight Heat Exchangers

摘要

The final assembly operations for completion of the Cb-1%-Zr, Hastelloy X, and 6061-T6 aluminum test modules were described. The tests performed were described and preliminary test results were listed. Final assembly operations of the Cb-1%-Zr core disclosed lack of ductility due to excess oxygen in the metal and internal surface inperfections in the tubing that required modifications in forming operations on the tubes at the upper header. Welding operations of the lap joint between the lower and upper headers of the core disclosed the need for extraordinary controls in fit and restraint to achieve satisfactory welds. The tendency of AGCI braze alloy (50% Au, 25% Ni, 25% Pd) to alloy with Hastelloy X, although less than with stainless steel, dictated a maximum of a single repair cycle using a lower melting temperature alloy. Preplaced braze alloy rings, held in place with a volatile acrylic resin, provided leak-tight tube-header joints in more than 99.5 percent of those attempted on the core. During final assembly operations of the aluminum core, it was learned that accelerated aging, which reduced the ductility of the tubing, made it necessary to modify the shape of the ends of the tubes to prevent splitting. The epoxy sealing material for the tubeheader joints proved to be partially effective at liquid hydrogen temperature and at temperatures of 300F to 350F. (Author)