Self-Deployable Pulsating Heat Pipe actuated by Shape Memory Alloy for Space and Ground Application

The present thesis is developed in the European Space Agency project framework and deals with the facility study of a passive, thermally driven, deployable Pulsating Heat Pipe. Seven Shape Memory Alloy wires unfold the device, and the spring PHP tube folds it. Cold-worked 6063 Aluminum tube is shaped in 3.5 coils, and a mechanical model of the spring tube is proposed and validated by a Finite Element Method analysis with an error of 2-5%. The Shape Memory Alloy actuator employs the heat produced inside the satellite to passively actuate itself. During active heating, the maximum experimental deployable angle is 75 deg. Whilst, due to the ununiform temperature distribution, in passive heating, the deployment is 17 deg. The thermomechanical Shape Memory Effect is predicted by the implemented Brinson model and fits the final angle with an error of 6%. The thermo-fluid dynamic of the coiled Pulsating Heat Pipe is investigated by developing two different PHPs with the same length of the adiabatic section and different shapes, helical and straight pipes. Experimental results of the planar PHP show that the best-working fluid and filling ratio are HFE7000 and 70%. At the same parameters and boundary conditions, the deployable Pulsating Heat Pipe is investigated for three different deployable angles, 0, 90 and 180 deg, under normal and microgravity conditions. At 24 W and 34 W, the device is not affected by the mutual position of the evaporator relative to the condenser. The 180-deg configuration, the worst one at the start-up, is tested for two different coil orientations, up and down; the thermal resistance in the first configuration is lower than in the latter. The mean flow velocity, at 40 W, for the planar PHP is 0.34 m/s whilst for the PHP deployable in 180-up configuration is 0.46 m/s. Lastly, Srinivasan, White and Mori friction factors qualitatively best-fits the pressure drops in a coiled capillary tube of the Pulsating Heat Pipe.