Flexible wickless heat pipes radiator with self-rewetting fluids

Dilute aqueous solutions of high carbon alcohol (number of carbon atoms ≥ 4) show an increase in the surface tension with increasing temperature. In the course of liquid/vapor phase change, especially in microgravity condition, such a particular surface tension behavior introduces a vigorous liquid inflow at nuclealion sites or dry patch by enhanced Marangoni effect induced by both temperature gradient and concentration gradient due to preferential evaporation of alcohol-rich component One of the most promising applications of such "self-rewetting" fluids in space may be a working fluid for wickless heat pipes. The present authors first evaluated the heat transfer performance of wickless heat pipes (8mm in diameter) in reduced gravity available by parabolic flight, and outstanding performance of wickless heat pipe with 1-butanol aqueous solution was experimentally confirmed. Based on the concept of wickless heat pipes, the authors have been attempting at the development of advanced radiator panel that allows for flexible, inflatable, and deployable characteristics. New heat pipe radiator panels are now being fabricated by either polyimide multilayer film or polyimide/copper (or polyimide/graphite) laminate film, and reduced gravity experiments will be performed in the ESA parabolic flight campaign with A-300 in October, 2006 by the collaboration between AIST (National Institute of Advanced Industrial Science & Technology) and University of Naples. In addition to transparent single heat pipe panel tests, a series of mechanical and thermal performance tests of heat pipe radiator panels, such as inflation, extension, thermal operation and deployment, will be conducted in the reduced gravity condition with the aid of an IR camera.