Self-Deployable pulsating heat pipe concept based on a shape memory alloy actuator

The concept of a self-deployable Pulsating Heat Pipe (PHP) actuated by Shape Memory Alloy (SMA) is shown in the present paper. The system exploits the heat source to activate both the two-phase flow in the PHP and the shape memory effect in the actuator to passively fold and unfold the device. The PHP acts as a torsional spring in the adiabatic section, and a shape memory wire unfolds it. The authors propose a mechanical model that outlines the size/material (spring/Al6063) and number of coils (3.5) to design the PHP adiabatic section and the actuator (7 Nickel-Titanium parallel wires). Two strategies are adopted to simulate active (Joule effect) and passive (heat conduction) heating. Joule heating uniformly warms the SMA wire to 120 ℃, allowing the device to deploy up to 80 deg. Despite, under the passive heating, the shape memory effect is limited (deployment 16.5 deg) due to poor heat conduction, this is a breakthrough starting point for further implementation. For such purpose, the shape memory effect at non-uniform heating is simulated and predicted via a thermomechanical analytical model. Simulations are then validated with good accuracy with the experimental results obtained (error between 12 %-15 %).