Heat Transfer Considerations for Designing FSW Cryogenic Thermal Structures for Aerospace Applications

Research was conducted to investigate potential structural design configurations for aerospace cryogenic tank wall applications. The primary design considerations included the vibration damping characteristics under various flight loading conditions and the panel wall thermal resistance under different heat loads. The discussion herein is with regards to the thermal issue, specifically the heat transfer rates across two different panel wall designs that have attractive vibration damping characteristics. The heat transfer rates were evaluated analytically and verified with experimental data. One panel is a corrugated, serpentine-layered design fabricated using friction stir welding. The other panel is an “egg-carton” design fabricated using friction stir spot welding. An important thermal consideration for the cryogenic tank wall design is the minimum outer wall temperature attained during ambient storage or prior to launch. Of the two designs considered herein, neither wall provided sufficient thermal resistance to maintain outer wall temperatures above freezing under ambient conditions. One of the wall designs, however, performed somewhat better. It is shown that when configured with an outer layer of thermal plastic coating both designs could maintain an outer wall temperature within design constraints.