U-PHOS EXPERIMENT: THERMAL RESPONSE OF A LARGE DIAMETER PULSATING HEAT PIPE ON BOARD REXUS 22 ROCKET

A Pulsating Heat Pipe (PHP) is tested on board REXUS 22 sounding rocket in order to obtain data over a relatively long milli-gravity period (120s). The device is made of an aluminum tube bent in a serpentine staggered configuration, closed in a single loop and partially filled with FC-72. Despite the 3mm internal diameter is Greater than the capillary threshold in ground conditions, in milligravity the slug flow pattern is maintained as well as the thermally driven self sustained oscillation of the working fluid. The possibility to build PHPs with big diameters, with increased heat transfer rates and reduced overall Thermal resistances, is an interesting step forward in the fast developing space industry, always craving for greater performances at a reduced weight and cost. The experiment is the natural improvement of the PHOS project, launched on REXUS 18 but only partially successful due to a failure in the de-spin system of the rocket. All the components have been improved, especially the test cell geometry, the data acquisition system -now employing 24 Fiber Bragg Grating optical sensors for a more accurate temperature detection- and the heat sink -now composed by a combination of paraffin wax and metal foams for an enhanced thermal conductivity. The Thermal response of the device is given under a constant heat power supply at the evaporator.