Flocked Carbon Heat Exchanger Tubing

This project aims to develop nonpermeable thin-guage carbon tubing with an integral radial carbon fiber brush on its outer surface for enhanced heat transfer. The carbon tubing is derived from polyimide tubing. The radial fiber structure is created by electrostatic flocking. Coatings to block hydrogen permeation and to prtotect against erosion are applied by chemical vapor deposition. The proposed process is suited for various guages of tubing and for various curvatures. The flocked carbon tubing my be integrated with carbon fiber preforms and processed to form an actively cooled carbon-carbon structural component for use with hot pressurized hydrogen. Phase 1 effort will focus on materials processing. We will investigate the carbonization of selected precursors, fiber flocking methods, and CVD coatings. Electron microscopy will be used to inspect the tubing wall and fiber attachment. Sections of flocked carbon tubing will be fabricated for thermal cycling, and measurements of permeation and the rate of erosion in hot hydrogen. Preliminary thermal analysis will model carbon-carbon heat exchanger structures with the new tubing to investigate design trades and assess the overal performance. A draft design for a Phase 2 prototype heat exchanger panel will be prepared. Phase 2 would continue process development, leading to fabrication of a prototype exchanger panel to be tested under conditions relevant to the NASP leading edge application.