Carbon/Carbon Composites with Refractory Metal Tubes Formed In-situ for Improved Heat Transfer

In the next generation of air-breathing high-performance engines, significant engine performance improvements are envisioned by combusting hydrogen with air in a regeneratively cooled carbon/carbon composite combustion chamber. Surfaces subjected to aerodynamic heating will also be cooled by recirculating hydrogen through cooling tubes. To date, approaches investigated have not had desired levels of heat transfer. In the Phase I program, two approaches to providing high heat transfer between cooling tubes and the C/C composite will be investigated. In the first, holes machined in the composite will be lined with a refractory metal liner using a proprietary process which provides good bonding between the metal liner and the composite. The process should completely fill any cracks or pores in the C/C composite. In the second approach, metal alloy tubes will be placed in refractory metal lined holes in the C/C composite. The gap between the tubes and the lined holes will be filled with copper or other non-reactive brazing metal. Filling the gap with high-conductivity metal should increase heat transfer to desired levels. Samples will be tested for hydrogen leakage, resistenace to thermal cycling and resistance to high heat fluxes. The data developed in Phase I will lead to the design and operation of a prototype heat exchanger in Phase II.