CPL and LHP Technologies: What are the Differences, What are the Similarities?

Despite the wide use of the capillary pumped loop (CPL) and loop heat pipe (LHP) technologies, fundamental confusion persists about CPL and LHP operation, their uses and limitations, and even the similarities and distinctions between the western-heritage CPLs and Russian-heritage LHPs. It is therefore the purpose of this paper, written by engineers who have participated in developments on both sides of the Atlantic Ocean, to explain these issues to potential users of these emerging thermal control technologies.