Start-up of a large diameter Pulsating Heat Pipe on ground and on board a sounding rocket

This work presents the results obtained by a large diameter Pulsating Heat Pipe tested both on board a sounding rocket in March 2017 and on ground. During the flight, the PHP is tested exclusively at 200 W, while on ground several combinations of heat power input and inclination are tried. Since no steady state occurred on board the rocket, the comparison between flight and ground data focuses on the startup phenomenon, whereas the thorough ground test campaign describes the limits and performances of the device working in thermosyphon mode. The expected outcome of the Space PHP behavior is between that of a purely conductive tube and that of a gravity assisted thermosiphon. The obtained results, instead, evidence a favorable difference in the Space PHP thermal response with respect to any kind of ground test. Important innovations, as the employment of Fiber Bragg Grating sensors, allowed an easier integration of a high number of sensors for the temperature data acquisition with respect to conventional thermocouples