Effect of evaporator tilt on the startup performance of loop heat pipe with non-condensable gas

This work investigated the startup performance of a loop heat pipe (LHP) with non-condensable gas (NCG) under different evaporator tilt angles from -15° to 90°. The working fluid of the tested LHP was ammonia and nitrogen was injected into the LHP to simulate NCG. The main conclusions are summarized as follows: (1) When the tilt angle of evaporator was relatively small, the LHP could operate normally unless there was a large amount of NCG. The reverse flow usual occurred in the case without NCG and could be inhibited in the case with a small amount of NCG; (2) When the tilt angle was relatively large, the LHP could startup successfully with a small amount of NCG but not without NCG. (3) The LHP could not startup when the NCG inventory was large enough at all evaporator tilts.