A hybrid Closed Loop Thermosyphon/Pulsating Heat Pipe with an inner diameter bigger than the capillary\udthreshold is tested both on ground and in hyper/microgravity conditions. The device, partially filled up\udwith FC-72, consists of an aluminum tube (inner diameter: 3 mm) bent into a planar serpentine with five\udcurves at the evaporator. A transparent section closes the loop in the condenser zone, allowing fluid flow\udvisualization. Five heaters are mounted alternatively on the branches, just above the turns and controlled\udindependently, in order to investigate the effect of non-uniform heating configurations. On ground,\udwhere the device works as a thermosyphon, the non-uniform heating configurations promote the fluid\udnet circulation in a preferential direction, increasing the thermal performance with respect to the homogeneous\udheating. Parabolic flights point out that during the 20 s of microgravity, the sudden absence of\udthe buoyancy force activates an oscillating slug/plug flow regime, typical of the Pulsating Heat Pipes,\udallowing the device to work also without the assistance of gravity. Furthermore, peculiar heating configurations\udcan shorten the stop-over periods and stabilize the pulsating two-phase flow motion.
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