Improved Heat Removal by Microscopic Surface Texturing of Capillaries

Future space power and propulsion systems will be hot, hotter than materials can stand. They'll need active cooling for the toughest spots, either heat pipes (with recoverable coolant) or fuel channels. In general, heat transfer in these devices improves as capillary sizes shrink, but they cannot be arbitrary reduced without eventually causing blockages and catastrophic hot spots. Instead, Spire proposes to keep the larger passages but micro-texture inner surfaces by ion beams to increase surface area, similar to using internal vanes. For really hot applications, this will also increase thermal emissivity, something ordinary capillaries cannot do. Feature sizes much smaller than optical wavelengths make micro-textured metals broadband light absorbers, nearly perfect blackbodies that radiate more effectively than plain metal surfaces. The extra radiational heat transfer could really make a difference. Texture blakening will improve active cooling or nucleate boiling in hypersonic aircraft, fast computers, high power x-ray sources, adiabatic or Stirling engines, and other advanced systems.