Effect of bending angle on the thermal performance of a polymeric flat plate pulsating heat pipe

In response to the rising popularity of foldable electronics, Flexible Pulsating Heat Pipes (FPHPs) have emerged as a potential, adaptable and efficient solution for smart thermal management. This study experimentally investigates the performance of a novel FPHP with asymmetric channels at various bending angles. Four bending angles (0⁰, 30⁰, 60⁰, and 90⁰) were tested to observe the effect on the thermal resistance, evaporator temperature, pressure, and the underpinned two-phase flow dynamics. All experiments were conducted under constant filling ratio of 50% and heating power range of 4-32W using a compatible working fluid (FC-72). The tested FPHP was fabricated utilizing the stereolithography (SLA) technique. Results indicated that the required start-up temperature at the evaporator increases when the position of the condenser section is changed from vertical to 90° bending. Additionally, as the heating power increases, the thermal resistance variations are similar for 0°, 30°, and 60° bending angles, whereas the thermal performance deteriorates at 90°. The excessive bend at 90° results in a significantly increased flow resistance, affecting the internal flow. This results in a sudden increase of the evaporator temperature and pressure, leading to dry-outs. The maximum operating heating power is 32W for 0⁰, 30⁰, and 60⁰, while it reduces to 20W for 90⁰.