High-temperature ceramic heat exchanger. Final report

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Abstract
The results of an 18-month effort directed to developing the technology necessary to build a ceramic heat exchanger for operation with a small (200-hp) closed-Brayton-cycle engine are described. The ceramic heat exchanger operates with 3000/sup 0/F combustion products on one side and heats high-pressure Argon gas, which subsequently is delivered to the turbine, to 1800/sup 0/F. The design consisting of an array of siliconized-silicon carbide U-tube modules employing 180 1-in.- dia finned tubes was selected. An extensive materials data base was obtained on the Norton Company's NC-430 grade siliconized-silicon carbide, and to a lesser extent on Carborundum's sintered alpha silicon carbide (SASC). 250 basic material tests were conducted on various test specimens. The materials test program encompassed strength tests, cyclic fatigue tests, and stress rupture tests from room temperature to a maximum of 2950/sup 0/F (SASC only). Strength data were compiled on Weibull plots for application to the design effort. A subcontract was let to develop the required ceramic fabrication technology to produce the heat exchanger components. Finned tubes, manifolds, and U-tube sections were produced to specifications. Several complete heat exchanger modules incorporating the major design features of the engine heat exchanger configuration were designed and fabricated. Various tests weremore » conducted on the ceramic components produced to relate the actual strength characteristics of the components to predictions based on the material test specimens. Complete heat exchanger modules were produced and tested under simulated engine operating conditions up to 2300/sup 0/F tube wall temperatures. Heat transfer performance and pressure drop experiments were performed. Based on the experimental data collected, lifetime/reliability predictions were made for the ceramic heat exchanger designed for the original engine application. « less

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