Material Compatibility Problems for Ammonia Systems

Thermal management systems are currently being developed for application on large orbiting platforms, specifically the Space Station. Based upon its thermodynamic properties, ammonia was selected as a working fluid suitable to handle the power and heat rejection requirements of these systems. The Space Station's 30-year design life, minimum maintenance requirement, maximum reliability, and ammonia working fluid have led to new material compatibility issues. Although ammonia is a well understood fluid for ground-based refrigeration uses, it produced some unexpected results when applied to space-based heat transport systems.