U-PHOS Project: Experimental Results of A Large Diameter Pulsating Heat Pipe on Board Rexus 22

Micro-gravity environments might extent the concept of capillary behavior structure to large diameter tubes. A Loop Termosyphon, in its traditional use, is a two-phase thermal device which usually consists of a large tube, closed end to end in a loop, evacuated and partially filled with a working fluid and intrinsically gravity assisted. With the concept stated here, it may become a capillary tube in space condition and turn its thermo-fluidic behavior into a Pulsating Heat Pipe (PHP), or better, a Space Pulsating Heat Pipe (SPHP). The present work presents the results of the experimental campaign of a SPHP effectuated both on ground and in microgravity conditions. A SPHP has been designed and implemented on board of a sounding rocket launched in the 22nd ESA REXUS Sounding Rocket Campaign. This type of sounding rocket launch guarantees approximately 120s of microgravity environment. The ground tests prior to the launch demonstrated that the device effectively work as a gravity assisted loop thermosyphon, while the experimental data from the microgravity period during the sounding rocket launch reveal a change in the thermal hydraulic behavior similar to the PHP. The micro-g environment provided by the rocket was not sufficient to reach a pseudo steady state regime, therefore, further investigation on a longer term weightless condition is mandatory.